Lung resection has been shown to impair right ventricular function. Although conventional measures of afterload do not change, surgical ligation of a pulmonary artery branch, as occurs during lobectomy, can create a unilateral proximal reflection site, increasing wave reflection (pulsatile component of afterload) and diverting blood flow through the contralateral pulmonary artery. We present a cardiovascular magnetic resonance imaging (MRI) observational cohort study of changes in wave reflection and right ventricular function after lung resection.Twenty-seven patients scheduled for open lobectomy for suspected lung cancer underwent cardiovascular MRI preoperatively, on postoperative Day 2, and at 2 months. Wave reflection was assessed in the left and right pulmonary arteries  by wave intensity analysis and calculation of wave reflection index. Pulmonary artery blood flow distribution was calculated as percentage of total blood flow travelling in the non-operative pulmonary artery. Right ventricular function was assessed by ejection fraction and strain analysis.P<0.001) with an associated redistribution of blood flow towards the nonoperative pulmonary artery . On postoperative Day 2, impaired right ventricular ejection fraction was associated with increased operative pulmonary artery wave reflection  and pulmonary artery blood flow redistribution . At 2 months, impaired right ventricular ejection fraction and right ventricular strain were associated with pulmonary artery blood flow redistribution .Operative pulmonary artery wave reflection increased from 4.3 (2.1–8.8) % preoperatively to 9.5 (4.9–14.9) % on postoperative Day 2 and 8.0 (2.3–11.7) % at 2 months (Pulsatile afterload increased after lung resection. The unilateral increase in operative pulmonary artery wave reflection resulted in redistribution of blood flow through the nonoperative pulmonary artery and was associated with right ventricular dysfunction.NCT01892800. Secondly, we hypothesised that a unilateral increase in wave reflection results in a redistribution of blood flow through the contralateral PA, which may be a surrogate marker of afterload in this setting.ClinicalTrials.gov (identifier: NCT1892800) in August 2013. Ethics approval was obtained from the West of Scotland Research Ethics Committee (134/WS/0055). Written informed consent was provided by all patients. Inclusion criteria were adult patients undergoing elective open lobectomy. Exclusion criteria included pregnancy, ongoing participation in investigational research that could undermine the scientific basis of the study, contraindication to cardiovascular magnetic resonance imaging (CMRI), video-assisted thoracoscopic surgery, or any planned resection other than lobectomy. Techniques were standardised for surgery  and anaesthesia .We conducted a single-centre, prospective, observational cohort study in a tertiary referral cardiothoracic centre in Scotland. The study was prospectively registered on −1 for normal flow). Effective temporal resolution was one-thirtieth of the duration of the cardiac cycle.Cardiovascular magnetic resonance imaging  was performed preoperatively, on postoperative Day 2 (POD2), and at 2 months. ECG-gated fast-imaging steady-state free precession cines  were utilised throughout. Functional assessment slices of 6 mm thickness with a 4 mm gap between and voxel size 1.5 × 1.3 × 6 mm were measured. Short- and long-axis stacks of the ventricles were performed during breath holds. Flow analysis was performed in the pulmonary arteries (left and right), field of view 320–360 mm, slice thickness 5 mm, base resolution 256, phase resolution 100%, echo time 2.7 ms, repetition time 29.2 ms, and velocity encoding, as appropriate (150 cm sQ) and area (A) results for the 30 phases of the cardiac cycle were generated from the main PA (MPA), RPA, and LPA, termed operative or non-operative, as appropriate  by two independent reporters.ropriate .Fig 1SumIn patients with complete imaging at preoperative, POD2, and 2 months, strain analysis was performed on the cardiac four-chamber long-axis view using commercially available software .vs time curve throughout the cardiac cycle. PA distribution of blood flow was assessed by the blood flow travelling in the non-operative PA divided by the sum of total blood flow in the operative and non-operative PAs. PA acceleration time (AT) was measured as the time to peak flow.Data processing and interpretation were performed, as detailed in R Studio Inc . The anonymised and randomised images were inspected, analysed, and interpreted before unblinding. To reduce signal noise, the dual reported flow and area results were averaged for each phase of the cardiac cycle, a 7-point second-order Savitzky–Golay filter,Q) multiplied by the change in area (dA) and separated into the underlying forward and backward component waves; area changes are commonly used as a surrogate marker for pressure changes for noninvasive WIA.Wave intensity analysis (WIA) was performed as per Quail and colleaguesPost hoc comparisons were performed with the paired t-test or Wilcoxon signed-rank test. Unpaired comparisons were performed by the unpaired t-test or Wilcoxon rank-sum test. Within-subject association testing between the change in two continual variables was assessed by performing analysis of covariance (ancova) with the patient as the factor, as described by Bland and AltmanAll statistical analyses were performed in R Studio. Data are presented as mean (standard deviation) or median (inter-quartile range), as appropriate. Changes over time were assessed by one-way repeated measures analysis of variance or Friedman's test, as appropriate. in situ that was not MR compatible.Twenty-eight patients were recruited between September 2013 and September 2014, but one patient was discovered to have a ferromagnetic object within the chest wall on initial CMR imaging and excluded from further participation. CMR imaging was completed in 27 patients (100%) preoperatively, 22 patients (81.5%) on POD2, and 24 patients (88.9%) at 2 months. On POD2, three patients declined CMR imaging, one patient had a persistent air leak and CMR transfer was deemed unsafe, and one patient had an epidural catheter The mean patient age was 67 (15.0) yr, and 17 (63%) were female. Twenty-two patients had a lobectomy, and four had a bilobectomy (including right middle lobe). One patient required on table conversion to pneumonectomy; the patient is included in the strain and WIA results although excluded for the PA blood flow distribution testing. Right-sided procedures were performed in 17 (63%) patients  for all.P=0.022 and P=0.023, respectively; paired t-tests). LV strain was unchanged throughout the study.Heart rate and cardiac output were increased on POD2 but returned to baseline at 2 months . Twenty ,In total, flow/area plots were available for 215 vessels . Visual inspection of MPA area plots, however, revealed movement artifact in the majority of scans preventing WIA in the MPA. Inspection of operative and non-operative PA WIA plots revealed abnormalities in six scans (4.2%); all had marked late diastolic increases in area without corresponding changes in flow. This was considered not to be a true physiological change but secondary to motion artifact, as observed previously in the MPA,P<0.001; paired t-test; P=0.001 and P=0.026, respectively; Wilcoxon signed rank) compared with preoperative. Although the BCW area increased in the non-operative PA postoperatively, the FCW area increased in a similar ratio; therefore, non-operative PA WRI was unchanged throughout the study.There was a marked postoperative redistribution of blood flow with an increased percentage travelling through the non-operative PA compared with the operative PA  and was less than the non-operative PA at both postoperative time points  and the change in time to peak BCW in the operative PA , all within-subject ancova with patient as a factor.The time to peak BCW was reduced in the operative PA  and at 2 months , both within-subject ancova with patient as a factor. A within-subject increase in non-operative PA WRI was strongly associated with a reduction in RVGLS and RVFWLS at 2 months. In each association, increased WRI or redistribution of PA blood flow through the non-operative PA was associated with an impairment in RV function.On POD2, there were moderate negative within-subject associations between the change in RVEF (from preoperative to POD2) and both changes in operative PA WRI and PA blood flow distribution from preoperative . At 2 moPulsatile afterload (PA wave reflection) was increased after lung resection, which was associated with impaired RV function. Assessment of each individual PA revealed a unilateral increase in wave reflection in the operative PA and a redistribution of blood flow through the contralateral PA that are associated with impaired RV function. Although RV strain was initially maintained, impaired RV strain occurred by 2 months postoperatively.,pulsatile components of afterload without any change in PVR. At normal PA pressure, as demonstrated previously after lung resection,,Lung resection is a unilateral insult to the pulmonary vasculature; as such, conventional approaches to measure RV afterload across the entire pulmonary circulation may not detect important changes. Previous authors have demonstrated that PVR and PA pressures are unchanged at rest after lung resection, with no association demonstrated between changes in afterload (as measured by PVR) and RV function.,r=–0.663; P=0.001), PA blood flow redistribution , and RVEF , all within-subject ancova with patient as a factor. None of these associations were significant between the preoperative and 2 month time points.The wave intensity analysis models afterload in the time domain and can be performed in any vessel. This allows assessment of wave reflection in each individual lung and allows the changes observed to be temporally related to the cardiac cycle.P<0.001; Wilcoxon signed rank for both). The origin of the new reflection site in the operative PA may therefore be the anatomical site of surgical ligation of the lobar PA. Similar to pulmonary hypertension, the arrival of a BCW from a proximal reflection site earlier in systole appears to impair RV function.,vs 20–31.8% reported in pulmonary hypertension).,In the operative PA, the postoperative increase in WRI and reduction in time to peak BCW are in keeping with wave reflection occurring from a more proximal site than preoperatively. This is supported by calculation of the apparent distance to reflection (see Supplementary methods),In this study, there is evidence of both acute and chronic postoperative increases in wave reflection associated with impaired RV function. On POD2, the acute changes in operative PA WRI and PA blood flow distribution are associated with impairment of RVEF. At 2 months, the change in PA blood flow distribution is associated with impaired RVEF, RVGLS, and RVFWLS. The increases in WRI are associated with impaired RVGLS and RVFWLS at 2 months; interestingly, the association is strongest with the change in non-operative PA WRI, suggesting that if the non-operative PA is unable to accommodate the increased blood flow (i.e. no capacity to compensate), then impaired RV strain may develop over time.,,The results of this study highlight the potential pathophysiological mechanism by which RV dysfunction occurs after lung resection. At rest, the non-operative lung may initially be able to compensate for increased wave reflection in the contralateral lung; however, this may be insufficient with increasing cardiac output. Previous studies investigating the response to exercise after lung resection have demonstrated a rapid postoperative increase in PVR as cardiac output increases,The potential limitations of the study include the temporal resolution of CMR imaging, the use of PA area as a surrogate of PA pressure, and the lack of a load-independent measure of RV function. Wave reflection generates a short-lived BCW, which a low temporal resolution CMR scan may underestimate or fail to detect. High CMR temporal resolution requires long breath holds or prolonged free-breathing sequences to limit motion artifact.Further investigation is required to determine if the changes in RV function and afterload demonstrated in this study impact patient-centred outcomes. Having now confirmed the existence of the association between wave reflection and RV function, this now paves the way for testing of novel therapeutic strategies aimed at aiding adaptation to the unique perioperative physiology seen in patients undergoing thoracic surgery with a view to preventing cardiovascular complications and improving long-term functional capacity.Pulsatile afterload was increased after lung resection. The unilateral increase in operative PA wave reflection resulted in redistribution of blood flow through the non-operative PA and was associated with RV dysfunction.Study conception: BS.Obtaining of funds: BS.Supervising all aspects of the study: BS.Patient recruitment: PM, AA.Data acquisition: PM, AA.Data reporting/analysis/interpretation: AG.Dual reporting of cardiovascular magnetic resonance images: AA.Dual reporting of strain analysis: KM.Drafting of final manuscript: AG.Critical revision of manuscript: AG, PM, BS.Approval of final manuscript: all authors.


Empagliflozin, a sodium-glucose transporter 2 inhibitor, has been shown to bind to late sodium channels in mice cardiomyocytes. We sought to investigate the electrocardiographic (ECG) features associated with empagliflozin use in patients with diabetes mellitus. We compared ECG features of 101 patients before and after initiation of empagliflozin and found that empagliflozin was associated with a significant increase in QRS duration among diabetes patients with heart failure. The latest updates to the heart failure treatment guidelines by the American College of Cardiology recommend the use of sodium-glucose cotransporter 2 (SGLT2) inhibitors, either dapagliflozin and empagliflozin, in patients with heart failure with reduced ejection fraction (HFrEF) irrespective of diabetes status as add-on therapy . This reRecently, empagliflozin was shown to decrease the risk of CV death or HF hospitalizations in patients with HF with preserved or mid-range ejection fraction . The EurSGLT2 inhibitors have also gained attention for their potential antiarrhythmic effects, including a significant reduction in the risk of atrial fibrillation, atrial flutter, and new-onset arrhythmias ,8,9,10. SGLT2 inhibitors have the potential for wide adoption among prescribers given the clinical benefits. It is therefore important for clinicians to be aware of electrophysiologic effects of this class of medication. However, potential electrocardiographic changes associated with SGLT2 inhibitor use have not been reported. We hypothesized that empagliflozin (henceforth referred to as “Empa”) would be associated with shortening of the myocardial action potential duration, which would manifest as a shorter QRS duration and QT interval on the surface electrocardiogram (ECG). We also postulated that Empa would cause slower ventricular rates due to inhibition of the sympathetic nervous system . In thisn = 78), we used the most recent ECG obtained in the 12-month period prior to the initiation of Empa as the baseline ECG. We limited our sampling space to this window in order to limit the influence of disease progression and chronic medication changes in our observations. The frequency distribution of ECG rhythms before and after initiation of Empa was compared using Fisher’s exact test of independence. The paired t-test was used to assess the difference between baseline and post-Empa ECG measurements. Medication lists before and after initiation of Empa were compared using the two-sample Z-test of equality of proportions. All tests were performed as 2-tailed and statistical significance levels were set at a p < 0.05 in all applied analysis. Statistical analysis was performed using Stata (StataCorp Release 16). The study was deemed exempt from institutional review board evaluation as it used existing patient data.We queried our healthcare system’s database for encounters between 1 January 2020, and 31 December 2020, with at least one prescription renewal for empagliflozin and included patients who were at least 18 years old and had at least one ECG after initiation of Empa. We abstracted demographic data, comorbid conditions, all medication list before and after initiation of Empa, and cardiologist-confirmed ECG reports. For subjects who had before and after ECGs  were on the 10 mg daily dose; the remainder were on the 25 mg dose. Six patients (5.94%) died in the 18-month follow-up period. Hypertension and hyperlipidemia were the most common comorbid conditions. p = 0.65). An increase in several ECG metrics was observed after initiation of Empa, none of which were statistically significant: the PR interval increased by 4 milliseconds (ms) above baseline ; the QRS duration increased by an average of 6 ms ; and the corrected QT interval (QTc) increased by 2 ms  among females but remained unchanged in males. p = 0.04). In a further subgroup analysis, the difference persisted only among the 10 patients who were on the 10 mg dose. Within this subgroup, the ventricular rate increased by 2 beats/min, PR interval increase by 2 ms, and the corrected QT interval increased by 3 ms. The increases were not statistically significant.Seventy-eight patients had ECGs before and after initiation of Empa. Of these, 53.9% were female. Pre-diabetes and diabetes mellitus (DM) are independent risk factors for the development of atrial fibrillation and ventricular arrhythmias ,17,18,19p-value was significant at <0.1). Although baseline QRS durations were reported, the authors did not include this in predictor models for the odds of the composite outcomes occurring. While investigator-reported events represent important clinical outcomes, the role of SGLT2 inhibitors in altering electrical or mechanical remodeling of the heart in HF remains to be elucidated. In mouse models of HF and metabolic syndrome, there was a significant shortening of the QT interval and effective refractory period, and fewer fibrotic areas in the ventricular tissue in the group treated with Empa [There is a paucity of data on the electrophysiologic effects of Empa and other SGLT inhibitors in patients with heart failure. Previous studies are limited to analysis of clinical event rates in clinical trial data or animal models. Post-hoc analysis of the DAPA-HF trial reported a 21% reduction in the risk of investigator-reported ventricular arrhythmia, resuscitated cardiac arrest, and/or sudden death in patients with HFrEF treated with dapagliflozin in addition to standard therapy . In backith Empa . Thus, EINa) has a marked antiarrhythmic effect and pharmacologic agents targeting this pathway show a great deal of promise for patients with arrhythmogenic conditions [INa remains to be definitively established. However, Empa has recently been shown to inhibit late-INa in murine models of DM and heart failure [INa likely contributes to the arrhythmia burden in both conditions, and thus Empa has the potential to ameliorate both hyperglycemia and arrhythmias in patients with concomitant DM and heart failure [Inhibition of the late sodium current (late-nditions ,28,29,30 failure ,31. Prol failure ,32. The  failure ,31. HoweThe principal finding of our study is a significant increase in the QRS duration among HF patients who received the 10 mg Empa dose from 109 ± 22 ms to 120 ± 24 ms. Although this observation was in a small number of patients, the finding could have significant clinical implications in HF patients. QRS prolongation may result in ventricular desynchrony, which can result in further compromised cardiac output, increasing myocardial demand and overall worsening HF symptoms ,34. FurtINa in models representing coexistent DM and heart failure. It is therefore conceivable that there are interdependent effects that influence the response to Empa.Our analysis represents the first attempt to investigate electrophysiologic features of SGLT inhibitors in patients with coexistent DM and heart failure. Prior animal studies have been performed in models of either heart failure or diabetes mellitus; to the best of our knowledge, there are no data pertaining to the association between Empa and action potential duration or late-There are several limitations of this study inherent to its design. First, with only 101 patients in the cohort and 16 patients with both DM and heart failure, our findings should be interpreted cautiously. The generalizability of our findings is limited. Second, medication compliance and hemoglobin-A1C were not monitored throughout the duration of the study, thus effects of glycemic control on ECG changes could not be assessed. Third, other SGLTIs were not studied directly and the observed associations reported herein with Empa cannot be generalized to other agents within this class. Fourth, the study period is probably not long enough to assess the influence of duration of use on our findings. Lastly, owing to the small sample size, we were unable to control for confounders which could affect our findings. Despite these limitations, this study attempts to extrapolate proposed mechanisms of electrocardiographic effects in murine models to human subjects and represents a first step in translational research into the role, if any, of Empa on myocardial membrane physiology. Larger studies are warranted to definitively characterize electrophysiologic effects of Empa and other SGLT2Is in patients with heart failure and DM. A prospective cohort study in a carefully selected patient population could explore the relationship between Empa dose and electrocardiographic findings, assess whether the degree of glycosylation influences the association, and whether similar observations are seen in the other SGLT2Is.


Reproducibility between comparable LALS parameters was poor . Conclusions: LALS variables might be a sensitive marker of ACR in HTx recipients, principally discriminating between those studies without rejection and those with any grade of ACR. Inter-vendor variability was significant.Our aim was to investigate the role of left atrial longitudinal strain (LALS) in the non-invasive diagnosis of acute cellular rejection (ACR) episodes in heart transplant (HTx) recipients. Methods: We performed successive echocardiographic exams in 18 consecutive adult HTx recipients in their first year after HTx within 3 h of the routine surveillance endomyocardial biopsies (EMB) in a single center. LALS parameters were analyzed with two different software. We investigated LALS association with ACR presence, as well as inter-vendor variability in comparable LALS values. Results: A total of 147 pairs of EMB and echo exams were carried out. Lower values of LALS were significantly associated with any grade of ACR presence. Peak atrial longitudinal strain (PALS) offered the best diagnostic value for any grade of ACR, with a C statistic of 0.77 using one software (95% CI 0.68–0.84,  Left atrial longitudinal strain (LALS) has recently emerged as a useful tool, generating independent added value in different scenarios such as valvulopathies, atrial fibrillation, heart failure and systemic diseases ,7,8,9,10Endomyocardial biopsy (EMB) histological analysis is the gold-standard diagnostic method for cardiac graft ACR . In 2005As an arising technology, myocardial strain analysis by means of speckle-tracking echocardiography has been tested in ACR. In that regard, left ventricular global longitudinal strain (GLS) has been proved to be more significantly associated with myocardial injury in ACR episodes than the ejection fraction, which is usually preserved until severe damage is established . Some stWhereas strain analysis techniques applied to ventricular walls and their association with ACR in HTx recipients have been widely explored, evidence of the role of LALS in this context is lacking. There are some studies that explore the usefulness of left atrial strain in pediatric HTx recipients, and its association to left ventricular filling pressures ,28.Our group reported strain analysis applied to ventricular walls and its variability between two different software  in adultWe prospectively included all consecutive HTx recipients who underwent routine surveillance EMB during their first year after HTx, from 15 September 2014 to 31 October 2016. Bicaval technique was the surgical approach in all patients.An echocardiographic exam was performed within 3 h of EMB. Baseline demographics, clinical characteristics and hemodynamic data obtained in right heart catheterization were collected for each patient.ACR episodes were managed according to clinical presentation, EMB results and medical standards by expert heart failure cardiologists who were blinded to strain analysis results. No treatment was initiated before echocardiographic examination had been performed, as EMB histological reports were not yet available.The study fulfilled Helsinki recommendations for medical studies and was validated by the ethical research board of our center . All patients agreed and granted informed consent before enrollment.In our center, surveillance protocol after HTx consists of periodical transjugular vein right heart catheterization with EMB and right hemodynamic study . EMB is performed weekly in the first month, once every two weeks until the third month, monthly up to the sixth month, in the ninth and twelfth months, as well as every time there is a clinical surmise of ACR.Histological examination of EMB specimens was done by an expert pathologist blinded to echocardiographic findings and classified according to the revised criteria of the ISHLT as OR grade (no rejection), 1R grade (mild rejection), 2R grade (moderate rejection) and 3R grade (severe rejection). Grades 2R and 3R were considered treatment-requiring ACR (TR-ACR).Image acquisition was performed in accordance with consensus guidelines  by the sStrain analysis was performed or closely supervised off-line by two expert operators (M.R.O and J.K.). Both software packages included a dedicated mode for atrial analysis. The atrial region of interest was manually traced and adjusted to the atrial contour. Software automatically executed longitudinal deformation analysis under visual control of the atrial border tracking by the operator, who remained blinded to EMB results. No segmental sub-division of the LA was made, following current consensus for atrial deformation imaging ; therefoThe studies were firstly analyzed with Tom Tec 2D Cardiac Performance Analysis software  in New York (USA). LALS variables obtained as output included three longitudinal strain variables: end-systolic global LALS (ESALSg) which stands for the top atrial deformation value reached at the end of the systole, peak average LALS during reservoir phase (PALS) which is the parameter mostly recommended in consensus papers  and stanThe sample was secondly analyzed with Velocity Vector Imaging software  in Córdoba (Spain), which only proffered one atrial strain variable: PALS.Both software provided just one strain rate variable: peak average LALS rate during reservoir phase (PALSR).In order to test inter-vendor variability only comparable variables were used for this purpose: PALS and PALSR. All echocardiographic studies were classified according to the rejection grade observed in the concomitant EMB in three groups: no rejection (grade 0R), mild rejection (grade 1R) and TR-ACR (grades 2R and 3R). As the primary endpoint for this study, LALS variables and their association with ACR grades were investigated. We also performed a longitudinal analysis, comparing LALS values in every echocardiographic study with the previous one in the same patient, according to the change in rejection status.All valuable studies were incorporated to assess inter-software variability. To evaluate intra-software variability, a random sample of ten studies was analyzed independently by two expert operators with each software. The same sample was newly analyzed one month later by the same operator to test intra-observer variability within each software.Quantitative variables were expressed as mean ± standard deviation if normal distribution was confirmed by Kolmogorov–Smirnov test, or as median [percentile 25–75] otherwise. Categorical variables were expressed as percentages.t-test or Mann–Whitney U test were used to investigate the association LALS variables with ACR grades, as appropriate. To examine discriminative ability to diagnose rejection, receiver-operating characteristic (ROC) curves were depicted for those strain variables significantly associated with rejection.Analysis of variance for independent data, Student t-test for paired data was used, calculating Pearson correlation coefficients and the slope of regression line. Intra-class correlation coefficients (ICC), bias and Bland–Altman limits for agreement were calculated for all reproducibility analysis.In order to compare strain values generated with both software, Student p value < 0.05 was considered significant.ROC curves were compared with a De Long test . For the rest of statistical analyses, we used SPSS v 21.0 . A two-tailed n = 8, 44%), coronary artery disease , valvular disease , and congenital heart disease . Treatment at first visit consisted of corticosteroids , tacrolimus , mofetil mycophenolate , everolimus  and cyclosporine . Hemodynamic data collected during EMB procedure included: systolic blood pressure 149 ± 18 mmHg, diastolic blood pressure 94 ± 12, heart rate 93 ± 11 beats/min, systolic right atrial pressure 4 ± 3 mmHg, systolic right ventricular pressure 35 ± 7 mmHg and end-diastolic right ventricular pressure 5 ± 3 mmHg.We identified 169 EMB performed in 18 HTx recipients during the period of study. As echocardiographic equipment was unavailable in 22 of them, the final sample comprised 147 pairs of EMB and echocardiographic study (8 ± 3 per patient). The HTx recipients’ mean age was 51 ± 14, and the donors’ was 42 ± 11. Most recipients and donors were men . Mean ischemic time was 247 ± 33 min. Previous diagnosis leading to transplant were myocardiopathy . Conforming to histological and immunopathological analysis, none of the EMB met criteria for antibody-mediated rejection. Although being asymptomatic at the moment of examination, patients with TR-ACR (19 episodes in 9 patients) received intensified immunosuppressant therapy. There were neither deaths nor hemodynamic instability episodes.Pathological diagnosis was absence of ACR (grade OR) in 65 EMB (44%), mild rejection (grade 1R) in 63 EMB (43%), and TR-ACR in 19 EMB (13%), without significant differences in ACR grades distribution when compared to the whole sample . We found that lower values of LALS parameters were significantly associated with higher ACR severity  with TomTec software, and in 114 (77.5%) with Siemens (severity . Post hoseverity  pointed p < 0.0005). A value of TT-PALS ≥ 19%, present in 34% of studies, had a negative predictive value of 77% for any grade of ACR.LALS parameters performance in the diagnosis of any grade of ACR was calculated depicting ROC curves . On ROC Regarding longitudinal analysis, the previous echocardiographic study was available for 129 studies: rejection status changed from ACR absence to ACR presence in 15 cases, it did not change in 91 pairs (36 showed no rejection at the two time points and 51 presented ACR at both of them) and it changed from ACR presence to no rejection in 23 cases. LALS parameters did not significantly change according to changes in rejection status .p < 0.001 for both correlations, p < 0.0005; and 0.42 for PALSR, 95% CI −0.13–0.68, p < 0.0005. Bland–Altmann plots (p < 0.0005).Values of comparable LALS parameters (PALS and PALSR) were significantly correlated, although Pearson’s correlation coefficients of 0.44 to 0.45 suggest only a moderate association . The difference observed between areas was significant (p = 0.02), demonstrating TomTec’s better discriminative ability.As PALS was the parameter with the best ability to discriminate the presence of any grade of ACR, ROC curves were drawn using a total of 106 studies in which PALS values obtained with both software were available . Both son = 129) into derivation (n = 57) and validation (n = 72) cohorts. The ROC curve for PALS was calculated in the derivation cohort, showing a C statistic of 0.67 . A PALS value of ≥16% was selected as the best cut-off point for any grade ACR diagnosis in the derivation cohort. Applying this cut-off point to the validation cohort, we obtained sensibility, specificity, positive and negative predictive values for the diagnosis of any grade of ACR of 76%, 79%, 81% and 74%, respectively.We randomly divided the whole sample in which PALS measurement was feasible with TomTec (The main finding in this study was the significant association of LALS parameters with the presence of any grade of ACR in HTx recipients. To the best of our knowledge, LALS parameters behavior during ACR episodes in adult HTx recipients had not been reported before. LALS values, particularly PALS, showed a significant decrease with the presence of any grade of ACR, but failed to discriminate mild from TR-ACR episodes, and were not able to detect longitudinal changes in rejection status.These data come from a sample which is similar to those reported in previous studies regarding basal characteristics, as well as ACR episodes incidence ,24,25,26A transverse study has shown atrial strain to be affected in HTx recipients compared to control subjects , as atriHowever, LALS parameters in our study have been unable to rule out TR-ACR episodes, neither were they able to detect longitudinal changes in rejection status. Bidimensional speckle tracking applied to ventricular walls has shown consistent results in detection of TR-ACR, although this technique has not been as reproducible in longitudinal analysis ,24,25,26Despite well-known strain reproducibility when using the same software, inter-vendor strain reproducibility has been a striking concern during the last decade, due to which the European Association of Cardiovascular Imaging and the American Society of Echocardiography have addressed manifest efforts to standardize measurements. This is also true regarding LALS, and as exposed in the NORRE study, cautions have to be made when using different vendors . As expeOur study sample, although representative of standard HTx recipients’ follow-up, accounts for a limited number of patients and is circumscribed to a single center. As an observational study, it can only be hypothesis generating. A multicenter study would help to confirm these findings and may improve statistical power to detect changes in LALS parameters. HTx recipients often present challenging acoustic windows, mainly due to post-surgical changes, and suboptimal quality images forced us to exclude some images from strain analysis. Although our frame rate was optimized and adequate for longitudinal strain analysis, a higher frame rate would have been desirable for strain rate performance. We only took into account four-chamber view for atrial strain analysis, and used PALS during reservoir phase, as this approach is admitted in guidelines and has been used in several studies ,13,31. NLALS variables were found to be a sensitive marker of ACR episodes in HTx recipients in this prospective observational monocentric study, although more studies with higher sample size and follow-up are required to confirm its potential role in this scenario. The main discriminative value appears to reside between the absence of rejection and presence of any grade of ACR, and these findings were consistent when the images were analyzed using two independent software. Despite high inter-observer and intra-observer agreement, inter-vendor reproducibility of strain values was deficient, and feasibility and discriminative ability were significantly different. We postulate that a LALS decrease could be related to diastolic dysfunction in the context of myocardial impairment.


Moreover, TAPSE, TVS’, RVFWSL, and RV4CSL increased by 8.3% (p < 0.05), 9.0% (p < 0.05), 13.7% (p < 0.05), and 26.7% (p < 0.05), respectively, while PASP decreased by 7.6% (p < 0.05). At the end of the study, there was a significant linear correlation between the number of steps and the PASP  as well as the indices of RV systolic function in Group A. In conclusion, WAT is a valuable tool for implementing an effective ET program in CF. Furthermore, ET has a positive effect on RV systolic and diastolic function.Several studies have shown that patients with cystic fibrosis (CF), even at a young age, have pulmonary and cardiac abnormalities. The main complications are cardiac right ventricular (RV) systolic and/or diastolic dysfunction and pulmonary hypertension, which affects their prognosis. Exercise training (ET) is recommended in patients with CF as a therapeutic modality to improve physical fitness and health-related quality of life. However, questions remain regarding its optimal effective and safe dose and its effects on the patients’ cardiac function. The study aimed to provide a wearable activity tracker (WAT)-based ET to promote physical activity in CF patients and assess its effects on cardiac morphology and function. Forty-two stable CF individuals (aged 16.8 ± 3.6 years) were randomly assigned to either the intervention (Group A) or the control group (Group B). Group A participated in a 1-year WAT-based ET program three times per week. All patients underwent a 6-min walking test (6-MWT) and an echocardiographic assessment focused mainly on RV anatomy and function at the baseline and the end of the study. RV systolic function was evaluated by measuring the tricuspid annular plane systolic excursion (TAPSE), the systolic tricuspid annular velocity (TVS’), the RV free-wall longitudinal strain (RVFWSL), and the right ventricular four-chamber longitudinal strain (RV4CSL). RV diastolic function was assessed using early (TVE) and late (TVA) diastolic transtricuspid flow velocity and their ratio TVE/A. Pulmonary artery systolic pressure (PASP) was also estimated. In Group A after ET, the 6MWT distance improved by 20.6% ( Patients with cystic fibrosis (CF) often showed pulmonary and cardiovascular complications such as pulmonary hypertension, etc. and perform less physical activity than their healthy counterparts ,2,3. SomMany questions remain about how ET can affect the CF patients’ respiratory and cardiovascular systems. Moreover, uncertain results exist concerning the type of exercise that is the most appropriate for these patients and the most effective and safe ET prescription in terms of intensity, duration, and frequency ,4. ConsuThus, the present study aimed to use WATs to adequately prescribe the scheduled ET program dose applied to patients with CF and investigate whether it was sufficient to cause improvements in physical function and cardiac structure and function.Patients with CF were recruited from the Pediatric Pulmonology and Cystic Fibrosis Unit, Hippokration Hospital, Aristotle University of Thessaloniki, Greece.The study’s inclusion criteria were the following: patients with a stable clinical status, without worsening respiratory symptoms or overt pulmonary hypertension, or a history of contemporary heart issues. In addition, patients already participating in structured physical activity were excluded from the study. Finally, out of the 75 patients tested for eligibility for the study, nine eventually refused to participate  and the remaining 16 due to the presence of non-eligible criteria: active manifestation respiratory infection (six patients), findings of pulmonary hypertension (four patients), co-existing cardiac problems (two patients), and their regular participation in regular exercise programs (four patients)Patients fulfilling the inclusion criteria were informed regarding the aim and methodology of the research protocol and provided informed consent. Moreover, in the cases of minors, the parents/guardians signed the consent form. The Ethics Committee of the Aristotle University of Thessaloniki approved the study protocol. The study was conducted in accordance with the Declaration of Helsinki.The eligible patients’ anthropometric characteristics , clinical, medical, and physical activity history, and current medications were collected. After that, all patients underwent a six-minute walking test and an echocardiographic assessment, repeated at the end of the 1-year study. All outcome assessors were blinded to patient group allocation. After the initial assessment, the eligible patients were randomly assigned in a 1:1 ratio by simple randomization (drawing lots) to either the intervention (Group A) or the control group (Group B). The exercise group participated in a 1-year WAT-based ET program three times per week. Patients in the control group were asked to continue their usual lifestyle to participate in recreational physical activities, but refrain from any structured exercise intervention.A 6-min walking test (6MWT) was performed in both groups to evaluate the individuals’ level of physical fitness. This test measured the distance (6MWTD) that each patient could quickly walk on a flat and hard surface (30 m) in 6 min. In addition, the Borg scale Rating of Perceived Exertion Exercise was used to monitor the perceived intensity during the workouts.Echocardiographic studies were performed using a Vivid S70; GE Medical; Horten, Norway, equipped with an M5S phased-array transducer. Each subject was examined in a semisupine left lateral position. The electrocardiogram was recorded continuously, and three consecutive beats were stored digitally. All studies were stored in a central workstation  and were analyzed offline. The internal dimension of the left ventricle (LVEDD), the left ventricular interventricular septum thickness (LVIVSd), and the posterior wall thickness (LVPWd) were obtained at the end-diastole from the parasternal long-axis view. The dimension of the left atrium (LA) was measured at the end-systole. The systolic function of the left ventricle (LV) was acquired from the apical 4- and 2-chamber views. The LV end diastolic volume (LVEDV) and LV ejection fraction (LVEF) were obtained by the modified biplane Simpson’s method. The assessment of diastolic function was estimated with the measurement of early diastolic transmitral flow velocity (MVE), late diastolic transmitral flow velocity (MVA), and their ratio (MVE/A). All measurements were undertaken following the European Association of Cardiovascular Imaging and American Society of Echocardiography guidelines .Right ventricular (RV) linear dimensions were assessed from parasternal long axis proximal RV outflow diameter (RVOT prox) and RV-focused view basal RV linear dimension (RV bas) at the end-diastole. Right atrial volume (RAVol) was calculated using the disk summation techniques from apical four-chamber view at end-systole. The diameters of RV and RAVol were normalized with body surface area. The measurement of tricuspid annular plane systolic excursion (TAPSE) was obtained by M-mode echocardiography with the cursor optimally aligned along the direction of the lateral tricuspid annulus apical four-chamber view. The diastolic function of RV was measured from early diastolic transtricuspid flow velocity (TVE), late diastolic transtricuspid flow velocity (TVA), and their ratio (TVE/A) at held end-expiration without tachycardia. Pulsed-wave TDI analysis of the RV free wall at the level of the tricuspid valve annulus was performed to measure the systolic tricuspid annular velocity (TVS’), the early diastolic tricuspid annular velocity (TV), and the late diastolic tricuspid annular velocity (TVA’). Pulmonary artery systolic pressure (PASP) was measured from peak TR jet velocity, using the simplified Bernoulli equation and combining this value with an estimate of the RA pressure, estimated from the IVC diameter and respiratory changes following the guidelines. The 2D systolic longitudinal strain was measured from an RV-focused apical view, and the RV was divided into six segments . The RV free-wall longitudinal strain (RVFWSL) and the RV four-chamber longitudinal strain (RV4CSL) were measured following the consensus document of the EACVI/ASE Industry .The 1-year intervention consisted of an individualized home-based ET program using WAT to ensure the patients’ autonomy and often behavioral face-to-face sessions with a physician. The exercise program consisted of any physical activity that each patient preferred that counted steps at least five times a week. The goal was for females to achieve >10,000 steps and males >12,000 per day during the third month of the program and gradually increase to >14,000 steps for females and >16,000 steps for males toward the end of the 1-year intervention. To avoid injuries during a scheduled ET session, patients were asked to start with 5 min warm-up and stretching exercises and finish with 5-min cool down. Patients were asked to choose enjoyable, easy, and accessible activities such as brisk walking, jogging, or dancing, at least five days a week. They were also encouraged to participate in any recreational sports they preferred to increase adherence. Τheir steps during these activities, where the sport allowed it, were counted in the number of total steps. Each patient was asked to upload and store their WAT data on the computer by the end of each week for 52 weeks. The same researcher collected the data, monitored each patient’s progress, and called them in case they did not achieve the goal. The face-to-face behavioral sessions with a physician occurred during the clinic visits at the baseline and every three months. At all sessions, patients brought their diaries, presented their progress, described their experiences and impressions, discussed their achievements, and were educated about the health benefits of exercise, encouraged to continue the ET program, and instructed to continue the self-monitoring to achieve their goal. Therefore, patients were asked to note the number of steps during their daily physical activity and not its duration. Moreover, the total step counts were computed by summing each exercise training step and calculating the median values from the ET days for each participant. At the end of the study, the sum of the total steps per week was estimated. Regular clinical examinations were also performed in all face-to-face clinical sessions.http://www.garminconnect.com (accessed on 23 March 2022).The G1  wearable activity tracker, a 3-axis accelerometer, was provided to each patient in Group A to record their level of physical activity in terms of the number of steps per day. Participants were asked to wear the WAT continuously during the study. They were also instructed to record the number of steps achieved each day in their diary. Additionally, they were educated to upload their data online weekly at Did you accept wearing the wearable activity tracker sensor during your exercise training? (Yes/No).Do you think that the wearable activity tracker provided you support and motivation to increase your level of participation in the exercise training program? .Do you think the wearable activity tracker increased your adherence to the exercise training program? .To assess the effective behavioral principles , each patient filled out a simple questionnaire at the end of the study, answering the following questions:p-values < 0.05 were considered as statistically significant.Data are presented as mean ± SD. The Statistical Package for Social Sciences , version 25.0 software for windows, was used. The normality of distribution was examined using the Kolmogorov–Smirnov test T-test was used to examine the initial mean differences between the two groups, while two-way repeated measures ANOVA was used to examine the mean differences within time and between the two groups with a Bonferroni correction (Bonferroni post hoc test). Moreover, linear regression was used to study the association between variables at the baseline and the end of the study. The two-tailed Fifty patients with CF participated in the study . Eight participants (four from each group) dropped out of the study due to exacerbation or non-compliance . All parThe demographic and clinical characteristics of the 42 patients (21 in each group) at baseline and after one year are presented in In Group A, the mean number of steps per day recorded by the WAT was at baseline 6374.4 ± 812.1 and 7543.2 ± 654.1; at the end of six months, 10,103.3 ± 985.9 and 12,464.8 ± 846.4 and at the end of the twelve months 15,924.0 ± 927.1 and 16,884 ± 882.3 for females and males, respectively. There were statistically significant differences between the different periods.All patients in Group A accepted the use of the WAT (Question 1); they supported that the WAT helped them increase participation in the ET program and, in general, their physical activity (score 8.1 ± 0.6 in Question 2), and they believed that the WAT increased the adherence to the exercise training program (score 7.35 ± 0.3 in Question 3).p < 0.05), as estimated by the significant increase by 84.3 ± 9.6 m in the distance walked in the 6-MWT. In addition, a significant linear correlation was observed between the number of steps recorded and the 6-MWT results both at baseline  and the end of the study  in group A. From the echocardiographic studies at baseline, all patients had a normal systolic and diastolic function of LV and normal dimensions of LA and LV  were at lower limits, probably reflecting subclinical changes-abnormalities of RV. The mean PASP was within the normal limits . No baseRV bas: right ventricular basal diameter, RVOT prox: proximal right ventricular outflow track diameter from PLAX, RAVol: right atrial volume, TVE: early diastolic transtricuspid flow velocity, TVA = late diastolic transtricuspid flow velocity, TVE/A: ratio of early to late diastolic transtricuspid flow velocity, TVS’: systolic tricuspid annular velocity, TVE’: early diastolic tricuspid annular velocity, TVA’: late diastolic tricuspid annular velocity, TAPSE: tricuspid annular plane systolic excursion, PASP: pulmonary artery systolic pressure, RVFWSL: right ventricular free-wall longitudinal strain, RV4CSL: right ventricular four–chamber longitudinal strainp < 0.05) and TVE/A increased by 13.2% (p < 0.05). Moreover, TAPSE, TVS’, RVFWSL and RV4CSL increased by 8.3% (p < 0.05), 9.0% (p < 0.05), 13.7% (p < 0.05) and 26.7% (p < 0.05) respectively (p < 0.05).At the end of the ET program in Group A, TVA decreased by 17% , 11.3% (p < 0.05), and 20.3% (p < 0.05), respectively, compared to group B.No change was found at the end of the study in Group B over time. However, at the end of the study, patients of group A demonstrated increased TAPSE, RVFWSL, and RV4CSL by 6.3% (p < 0.01), TAPSE , RV4CSL  and RVFWLS  in group A.At the end of the study, there was a significant linear correlation between the number of steps per day recorded and the PASP (r = −0.727, 2. [The present study results showed that using a WAT during the ET program in patients with CF significantly helped them monitor their physical activity levels, follow the prescribed ET schedule, improve their exercise adherence, and, thus, increase their performance. In addition, a strength of the study was that a significant increase in the number of steps performed by patients during ΕΤ was associated with more benefits on functional capacity and RV cardiac function. Patients with CF were characterized by exercise intolerance, which is multifactorial including age, sex, sedentary lifestyle, nutritional status, the severity of the disease, lung, and heart dysfunction, genotype, and chronic colonization by Pseudomonas aeruginosa, etc. ,3,12. Ce2. ,14,15. T2. . Excessi2. . It was 2. ,19,20. T2. . Moreove2. . A cysti2. ,23. Thus2. . Finally2. . The ech2. . Moreove2 peak improvement and survival in patients with CF [Regular exercise is recommended to be included in the CF treatment. Several studies have supported that ET is an essential therapeutic intervention in CF to maintain respiratory function, physical fitness, and health-related quality of life ,2,3. Sys with CF . We foun with CF . The 6MW with CF .Apart from the widely acknowledged cardiovascular and musculoskeletal benefits of exercise in chronic disease patients, studies have described specific mechanisms of physical training to maintain respiratory function ,30. It wThere has been no study examining the effects of ET on the cardiac function in CF patients in the literature. However, the results of our study indicated that the WAT-based ET program did not affect LV anatomy and function. Similarly, no changes were found in LA, RA, and RV anatomy. In contrast, speckle tracking echocardiography revealed an exercise-related subclinical improvement in systolic RV function. Notably, the PASP, TAPSE, RVFWLS, and RV4CSL were correlated with the number of steps counted at the end of the study in Group A. Similar evidence of the dose–response relationship between the exercise prescription and the improvement in QoL, aerobic capacity, and cardiac function in chronic cardiac and pulmonary disease patients has previously been reported ,35.Cardiac exercise rehabilitation attenuates cardiac remodeling in cardiovascular disease states, typically defined as mild LV end-diastolic or end-systolic volume changes and improvements in systolic and diastolic cardiac function . Such exIt was demonstrated that exercise primarily affects the RV, which is critical to circulatory function during a performance . La GercSome controversies exist about the optimal dose of exercise in CF patients . GuideliThere were some limitations to our study. First, we did not include a sedentary healthy control group to compare the physical capacity and cardiac function with the findings of our patients at baseline. However, we used the normal values reported in the literature for these ages to estimate the cardiac function of our patients ,47. SecoIn conclusion, WAT is a helpful tool for the reliable implementation of an exercise training program in patients with CF. Furthermore, our findings indicate that higher levels of physical function cause more distinct cardiac adaptations in RV.


RVGCS, RVESVi, and RVGRS were decent predictors of low RWA  early after implantation and during 2–6-month follow-up. To summarize, low RWA of ICD lead in ACM patients was associated with RV abnormalities. The RVGCS, RVGRS, and RVESVi can be valuable predictors for identifying low RWA prior to ICD implantation.Inadequate R wave amplitude (RWA) after implantable cardiac defibrillator (ICD) implantation in patients with arrhythmogenic cardiomyopathy (ACM) was suspected to relate to right ventricle impairment. However, little data-based evidence was provided to quantify the association. We retrospectively enrolled ACM patients receiving CMR examinations before transvenous ICD implantation from Fuwai Hospital. The RWA was obtained within 24 h and at 2–6-month follow-up after the operation. Structural, functional, as well as tissue characterization of the left ventricle (LV) and right ventricle (RV), were analyzed in relation to RWA. Among the 87 ACM patients (median RWA: 8.0 mV), 19 (21.8%) patients were found with low initial RWA (<5 mV) despite attempts in multiple positions. RV end diastolic diameter (RVEDD), (r = −0.44), RV ejection fraction , RV end diastolic volume index , RV end systolic volume index , RV global circumferential , and radial strain (RVGRS, r = 0.61, all  Arrhythmogenic cardiomyopathy (ACM) is a type of inherited adverse cardiomyopathy featuring fibrofatty replacement of the normal myocardium and holds a high risk of life-threatening ventricular arrhythmia or sudden cardiac death . An implPrevious small-sample size studies have found that, compared with other types of progressive cardiac disease such as dilated cardiomyopathy and hypertrophic cardiomyopathy, a higher rate of low RWA <5 mV) was observed in ARVC patients at the time of implantation and during long-term follow-up  mV was o. AnotherWe retrospectively reviewed ACM adult patients (age ≥ 18 years old at implantation) who were hospitalized in the Arrhythmia Center of Fuwai Hospital from January 2011 to March 2022 for primary implantation of ICD to prevent VTA or SCD and underwent the CMR examination within 30 days before the implantation. Among the 93 ACM patients who met the definite 2010 ARVC task force criteria (TFC) with 2 major, or 1 major plus 2 minor, or 4 minor criteria from different categories, 2 patients were excluded due to confirmed obstructive coronary heart disease and another 4 patients were excluded due to inadequate quality of CMR image. Finally, 87 consecutive ACM patients were included for analysis. Clinical history, symptoms, demographic, 12-lead or long-time monitoring electrocardiogram features, CMR, and medical treatment data were collected. Low RWA was defined as the value of the baseline rhythm R-wave voltage below 5 mV [Implanting records were reviewed to determine the device and lead type as well as the site of the RV lead position. All patients received ICD  via a transvenous lead system by three senior electrophysiologic physicians , all of the ventricular leads were active fixation leads, and were inserted in the RV apex or septum. The lead parameters, including sensing, pacing threshold, pacing impedance, and defibrillation parameters were determined during the procedure and within 24 h after the procedure. Careful attention was paid to achieve adequate sensing of 5 mV and a pacing threshold of <1.5 V per 0.5 ms, otherwise multiple endocardial positions were tested. If there was still unfavorable RWA even after several attempts, the lead was placed at a position with relatively higher sensing parameters with a shared decision by the physician and the patients. The minimum nominal sensitivity was set at 0.3 mV. The ICD parameters were repeatedly measured in 2–6-month clinic follow-up after discharge. The bipolar recordings from the right ventricular lead under intrinsic rhythm were tested repeatedly at least twice and the mean value of a stable RWA record was used for RWA comparison.CMR studies were conducted on a 1.5 T MRI scanner  or a 3.0 T MRI scanner . MRI studies were transferred to offline blinded analysis. Breath-hold cine images were acquired in 3 long-axis views  and a series of short-axis planes covering the whole LV and RV from the annulus of the aortic valves to the apex using balanced steady-state free precession sequence (b-SSFP). Cardiac volumetric and functional parameters, including left/right ventricular end-diastolic volume, left/right ventricular end-systolic volume, and left/right ventricular ejection fraction (LVEF/RVEF), were automatically generated. All the volumetric parameters were indexed to body surface area. To visually assess the fibrofatty infiltration, mDixon’s technique was applied for fat–water separation imaging . SpecifiLate gadolinium enhancement (LGE) images were acquired 10 to 15 min after intravenous administration of gadolinium-DTPA  at a dose of 0.2 mmol/kg with a breath-held phase-sensitive segmented inversion-recovery sequence in the same views as the cine images. The presence of LGE in LV myocardium was visually analyzed using the American Heart Association (AHA) 16-segment model by consensus reading of 2 independent observers (Y.S and X.M). The regions of LGE were fine-tuned by the operator to reduce false-positive when necessary. CMR-FT analysis was carried out by using CVi42 . LV and RV end-diastolic endocardial and epicardial contours were traced semi-automatically in long-axis views  and short-axis view on cine images by investigators blinded to the clinical and CMR data. All contours were adjusted after visual inspection during cine loop playback to ensure appropriate tracking of LV and RV segments. The global longitudinal strain (GLS) was obtained from the 4-chamber view for the RV and from the 2-chamber, 3-chamber, and 4-chamber views for the LV. The global circumferential and radial strain (GCS and GRS) parameters for both the RV and the LV were determined in the short-axis views of cine images [t-test/Mann–Whitney U test, analysis of variance, or Kruskal–Wallis test was applied for evaluating the differences between continuous variables as appropriate, and Dunn’s multiple comparisons were used for post hoc analysis. The chi-square test or Fisher’s exact test was used for assessing the difference of discrete variables between groups. The simple correlation between continuous imaging markers and RWA was examined by the Spearman correlation rank test and evaluated by the correlation coefficient and p-value. Univariate linear regression analysis was also performed to assess the clinical and imaging variables associated with RWA with parameter estimates and standard errors reported. The independent associations between RV mechanical, tissue characterization variables, and RWA were further accessed by adjusting for demographic, ECG, and traditional structural and function imaging features and lead position using a multivariate linear regression model. The independence of variables was confirmed by the Durbin–Watson statistic. A value of Durbin–Watson statistic close to 2 indicates no autocorrelation within the model [Continuous variables distributions were tested for normality via the Shapiro–Wilk test and were described as mean with standard deviation if normally distributed, otherwise as median with interquartile range (IQR). The discrete variables were depicted as counts and proportions. Student’s he model . The recn = 5) and DSG2 (n = 5) as the most common pathogenic gene. The median RWA was 8.00 mV (IQR: 5.1–11.8 mV) in the total population. In 19 of the 87 patients, though multiple positions of the RV lead were tested for achieving adequate pacing parameters, the final RWA achieved in ARVC remained lower than 5 mV.A total of 87 patients were included for final analysis, of whom 77% were implanted for secondary prevention while the rest 23% were implanted for primary prevention. The mean age at initial ICD implantation was 43.8 years old and 70.1% were male patients. For these patients, genetic testing was performed on 15, and 10 of them were positive for pathogenic variants, with PKP2 ) and 9.7 mV (IQR (7.3–13.6) mV), respectively, while the pacing threshold and impedance were satisfactory and did not differ between the two groups. Furthermore, there is no difference in the ICD brands and ICD types between those presented with low RWA or acceptable RWA. The final screwed lead position of the low RWA group was more frequent in RV apex compared with the acceptable RWA group, but this does not reach statistical significance.p = 0.002) and circumferential strain values (−2.86 (−4.17–1.95) vs. −6.08 (−9.42–−3.52), p < 0.001) were significantly impaired in the low RWA group, as compared to the other group , RVEF , RVESVi , RVEDVi , RVGLS , RVGRS , and RVGCS , rather than the LV features . All patients with RWA lower than 5 mV remained having low RWA level. Four (5.9%) patients in acceptable RWA group at implantation have RWA dropped to lower than 5 mV at the first follow-up. There is a slight increase in pacing threshold (0.50 (0.50–0.80) V @0.5 ms vs. 0.75 (0.50–1.00) V @0.5 ms, p < 0.001). The median pacing impedance measured at implantation decreased from 595.0 (IQR 509.5–774.0) to 550.0 (IQR: 464.0–668.0 ohms). The RV parameters derived from CMR analysis was also strongly correlated with the follow-up RWA, while the LV metrics did not display significant correlation (p < 0.001), these parameters still held high predictive values for low RWA at 2–6-month follow-up .At first follow-up after patients discharge, generally at 2–6 months post-implantation. The median initial RWA measured within 24 h after ICD implantation through the device was not different compared with that measured at 2–6 months (8.00 (5.10–11.85) mV vs. 7.80 (4.80–11.80) mV, relation . The RVGThe inter-observer and intra-observer variability of RV strain parameters were displayed in In this study, we observed pronounced arrhythmia clinical phenotypes rather than more severe LV dysfunctions in those with low RWA and we also found it is the impaired RV structure and function rather than the LV measurement correlate with the RWA. Specifically, abnormal morphological parameters such as RVEF, RVEDD, RVEDVi, RVESVi, impaired RV mechanics, including RVGLS, RVGCS, and RVGRS, as well as the presence of RV scar and fat infiltration were all associated with lower RWA within 24 h after ICD implantation. The RVESVi, RVGCS, and RVGRS held a good performance for differentiating low RWA in all ACM patients and the LV involvement subgroup and they also held predictive value of low RWA at 2–6-month follow-up after ICD implantation. Therefore, the RVGCS, RVGRS, and RVESVi derived from CMR are valuable parameters for predicting low RWA before the ICD implantation and might assist in pre-procedural planning, the decision of additional intraoperative mapping or optimized position for lead placement in ACM patients.Although recent years have witnessed the benefit brought by ICD for reducing the rate of SCD and improving the prognosis in ACM patients , low senRegarding the device or operation-related factors, we did not observe a significant difference in the device type, device brand, or pacing threshold and impedance between the acceptable RWA and low RWA groups. And among our population, the pacing thresholds were all below 1.5 V at 0.5 ms and impedance within the normal range, without dislocation events reported within 24 h after ICD implantation or before patients discharge.p = 0.165) at 2–6 months compared with the value measured 24 h after implantation, but the pacing threshold was slightly increased, with impedance decreased  mV vs. 7.80 (4.80–11.80) mV, ecreased , which iCMR allows for accurate quantification of biventricular morphology and function and provides additional information on tissue characterization. In the CMR-derived structural and functional parameters, larger RVEDD, lower RVEF, higher RVESVi, and RVEDVi, rather than corresponding LV parameters, were all strongly correlated with lower RWA. Additionally, the unfavorable RWA was absent from LV-dominated ACM phenotype and those with RVEF over 40%, which further affirms the dominating effect of abnormality from RV on the low sensing values of ICD.In addition to the traditional morphological parameters, the myocardium impairment can be more directly analyzed by both the fibrosis/fibrofatty replacement and regional motion abnormality. These factors are also emphasized in the diagnostic TFC as a visual assessment of RV regional wall motion abnormalities and histopathological findings. However, the visual assessment of RV motion is subjective and myocardial biopsy can be limited by the sample location and number. Even though direct assessment of fibrofatty replacement was challenging due to the thin RV structure, some advances in CMR imaging have been achieved. The emerging feature tracking technique based on SSFP images, the mDixon technique of fat–water separation, and the classical LGE analysis may provide a new modality for objective quantification of wall motion or noninvasive visual assessment of tissue characterization ,23. PrevRVEDD and RVEF were classical routine parameters for evaluating RV abnormality, but for predicting the low RWA probability, the discriminability of the two parameters is not as good as RVESVi and RVEDVi, which held AUC of 0.769 and 0.746, respectively. More importantly, CMR-FT-derived novel strain parameters such as RVGCS and RVGRS provided decent performance for predicting low RWA within 24 h after implantation with higher AUC in both the overall ACM population  and those with LV involvement , and these metrics are also capable of predicting low RWA at first follow-up at 2–6 months, which means that by resorting to the CMR evaluation before the ICD implantation, one might predict the possibility of low RWA in the ACM patients.Despite the fact that ICD is an undouble effective treatment for VA and SCD prevention in ACM patients, the low RWA is a troubling issue that adds difficulties to lead placement and leaves a risk for future complications such as delay or inappropriate therapy. Therefore, knowing which kind of ACM patient was more likely to experience low RWA at ICD implantation allows for a more thorough preparation of the operation. The current study offers a concept in the explanation of potential underlying factors responsible for low RWA after ICD implantation in ACM utilizing CMR to assess morphological and functional parameters and provides the possibility to predict tough situations preoperatively, thus advancing operational planning. Encouragingly, during recent years, more promising attempts have been made for dealing with the problem such as clinical usage of subcutaneous ICD , electriThis study also has several limitations. Firstly, as a retrospective study based on single-center experience, the detailed records of intraoperative parameters during every attempted position were not available, and information on difficulties in lead placement was described quantitively in the implanter notes so we cannot calculate the explicit attempted positions for each patient. Secondly, despite RV strain as a promising parameter for quantifying RV dysfunction, there are still no standardized normal values for the strain values, so it is still a research tool and not routinely applied in clinical practice. Additionally, although the CMR-FT is a less time-consuming and user-friendly method for RV analysis , compareIn conclusion, the structural, functional, mechanical, and tissue impairments of RV affect the RWA after ICD implantation. The RVESVi as well as RV strains including RVGRS and RVGCS provided by CMR were promising imaging markers for predicting low RWA and might assist in the preoperative planning before ICD implantation.


Microvascular obstruction is a transient phenomenon of “no reflow” after myocardial infarction or radiofrequency ablation, diagnosed using late gadolinium enhancement cardiac MRI. We present a patient with a persistent microvascular obstruction-like lesion following radiofrequency ventricular tachycardia ablation post-myocardial infarction, which was best characterized by a novel dark-blood late gadolinium enhancement technique. Microvascular obstruction (MVO), also known as “no reflow”, is a well-characterized condition that generally occurs after myocardial infarction or radiofrequency ablation. It is a transient phenomenon, presumably caused by damage to the myocardial microvasculature, and it usually disappears after a few days to weeks. MVO can be diagnosed using cardiac magnetic resonance (CMR) with late gadolinium enhancement (LGE), where it appears as a dark core within the hyperenhanced area of a myocardial scar. Here, we present a case of a persistent MVO-like lesion in a patient with previous radiofrequency ventricular tachycardia (VT) ablation post-myocardial infarction. Hereby, we illustrate the importance of a novel dark-blood LGE technique for detection of (chronic) ablation lesions and differentiation of MVO from other conditions.A 63-year-old male patient with high cardiovascular risk profile was initially hospitalized for late presentation anteroseptal myocardial infarction. Nevertheless, successful revascularization with percutaneous coronary intervention could be achieved. In the following days, several episodes of non-sustained and sustained VT occurred, requiring radiofrequency VT ablation. Hereafter, the patient was discharged without further complications and follow-up CMR was planned to evaluate left ventricular function post-myocardial infarction.1 All other sequence parameters were kept identical. On the four-chamber view, conventional LGE revealed a mid-septal dark area, slightly smaller compared to EGE, next to a bright zone in keeping with subendocardial ischemic scar . A short-axis cine stack was acquired to assess left ventricular function and post-myocardial infarction remodelling. Hypokinesia was observed at the mid-ventricular and apical segments of the septum. Global left ventricular ejection fraction was calculated at 53%. 2 min after intravenous injection of a gadolinium-based contrast agent, early gadolinium enhancement (EGE) imaging was performed which showed an area of subendocardial mid-septal hypoenhancement on the four-chamber view  panel A.mic scar  panel B.mic scar  panel C.mic scar  panel D.2 In reference to the timing of imaging after contrast administration, “early” and “late” MVO can be defined.3 Although the appearance of MVO is broadly similar on early and late gadolinium enhancement sequences, there are important differences. Since contrast agent diffusion is impaired in the direct vicinity of MVO, it appears larger on EGE than on LGE images, as was also observed in our case. Hence, sensitivity might be higher on EGE, but LGE is currently acknowledged as the most reliable technique to detect MVO and its structural and clinical implications.2As mentioned earlier, MVO is a phenomenon of “no reflow” observed in relation to ischemic myocardial scar formation. Using contrast-enhanced CMR sequences, it is characterized as an area with absent gadolinium enhancement within the infarct zone, and therefore appearing as a dark core within the hyperenhanced scar.2 To the best of our knowledge, no study observed MVO at more than 2 months after acute myocardial infarction.4The time course of MVO is known to be highly dynamic and differs depending on the clinical scenario. Following myocardial infarction, it usually appears after reperfusion and resolves after several days to weeks, reflecting areas of decreased myocardial perfusion.5,6 Chronic radiofrequency ablation lesions in regions of normal myocardium are observed to be hyperenhanced areas without the presence of MVO using LGE CMR.6A similar evolution has been observed with regard to MVO-like lesions post-ablation of non-infarcted areas. Several studies in patients without pre-existing myocardial fibrosis showed a transition of “dark” MVO appearance on CMR directly following ablation to “bright” LGE pattern on CMR at approximately 1 month following VT ablation.7 Although the appearance was similar, the authors concluded that the “dark core” regions could not be diagnosed as MVO, as they were observed several years after initial myocardial infarction. Surprisingly, in that study, the differential diagnosis between the MVO-like lesions and cardiac thrombi was made by echocardiography and medical history, even though CMR is considered the most accurate technique to detect left ventricular thrombi.8However, a different evolution has been observed regarding radiofrequency ablation lesions of myocardial scar in regions of previous myocardial infarction. A recent study by Dabbagh et al revealed, for the first time, the presence of a persistent MVO-like lesion on CMR in 17 patients at 30 ± 29 months after VT ablation post-myocardial infarction.1 Importantly, this dark-blood LGE technique is readily and widely available since no additional magnetization preparation mechanisms are required. Therefore, this technique can be helpful in clinical practice to improve the detection of  ischemic scar patterns.9,10 As this case illustrates, this novel LGE technique may also facilitate the discrimination of MVO from other conditions, such as left ventricular thrombus and wall thinning.It can be challenging to delineate areas of hyperenhanced subendocardial scar from the bright signal of the adjacent blood pool using conventional bright-blood LGE imaging. Due to this poor scar-to-blood contrast, the full extent of myocardial scar tissue can be significantly underestimated. In our case, a novel dark-blood LGE technique was used to improve scar-to-blood contrast by creating a darker blood pool signal while preserving the dark myocardium and bright scar signals.7 In their study, the dark cores corresponded with unexcitable areas, and thus might represent effective ablation lesions with dense scarring. Moreover, there has been evidence that the presence of MVO post-ablation is associated with a lower incidence of VT recurrence.11 Although different wash-in kinetics of very dense scar might be a possible explanation for the persistence of MVO-like lesions, further studies and histological validation are required to unravel the underlying pathophysiology and evaluate clinical implications.6The underlying mechanisms that make these MVO-like lesions visible long after radiofrequency ablation in pre-existing myocardial ischemic scar, while this is not the case for other types of post-ablation lesions, remain unknown. The clinical history and CMR findings in our case are consistent with the recent observations of Dabbagh et al.The phenomenon of persistent MVO-like lesions after VT ablation post-myocardial infarction has only recently been discovered and is supported by the findings illustrated in this case. The pathophysiology and clinical significance of these lesions in this specific setting remain unclear. Novel dark-blood LGE, compared to conventional bright-blood LGE, may be the preferred method to detect and differentiate (chronic) ablation lesions due to its superior scar-to-blood contrast.MVO-like lesions can persist for several months or years post-VT ablation in patients with previous ischemic scar.Dark-blood LGE improves differentiation of MVO and left ventricular thrombus due to its superior scar-to-blood contrast.


Ambystoma mexicanum, Shaw 1789) as model system of these diseases. Using micro-echocardiography, we assessed the form and function of the heart of the axolotl, an amphibian, and compared this to human DILV (n = 3). The main finding was that both in the axolotl and DILV, blood flows of disparate oxygen saturation can stay separated in a single ventricle. In the axolotl there is a solitary ventricular inlet and outlet, whereas in DILV there are two separate inlets and outlets. Axolotls had a lower resting heart rate compared to DILV (22 vs. 72 beats per minute), lower ejection fraction (47 vs. 58%), and their oxygen consumption at rest was higher than peak oxygen consumption in DILV (30 vs. 17 ml min−1 kg−1). Concerning the ventricular myocardial organization, histology showed trabeculations in ET (n = 5) are much closer to the normal human setting than to the axolotl setting. We conclude that the axolotl heart resembles some aspects of DILV and ET albeit substantial species differences exist.Few experimental model systems are available for the rare congenital heart diseases of double inlet left ventricle (DILV), a subgroup of univentricular hearts, and excessive trabeculation (ET), or noncompaction. Here, we explore the heart of the axolotl salamander ( The other ventricle is hypoplastic or, rarely, is completely absent2. Most of the systemic venous return as well as pulmonary venous return pass through the same ventricle without anatomical separation3. There is no cure and only palliation is possible. Most patients are currently palliated with a sequence of operations during their neonatal and childhood phase culminating in the Fontan circulation. This entails the creation of a direct connection between the systemic venous return and the pulmonary arteries, bypassing the heart4. Fontan patients suffer from the long-term consequences of this un-physiological circulation, which severely limits their quality of life and often leads to an untimely death6. Some patients with functionally univentricular hearts live without the standard Fontan palliation9. Long-term survival is probably related to favorable intraventricular streaming of blood flows with disparate oxygen saturation and a pulmonary artery stenosis10.Human functionally univentricular hearts are characterized by only one fully developed ventricle13. The axolotl salamander (Ambystoma mexicanum Shaw 1789) represents the oldest lab animal in a self-sustained population and is a widely used model in the fields of evolutionary developmental biology and regenerative biology14. The axolotl ventricular cavity is not only univentricular, but contains a very high number of trabeculations just as in other cold-blooded vertebrates15. In human, an excessively trabeculated ventricular wall allows for the diagnosis of ventricular noncompaction cardiomyopathy and it can afflict either or both ventricles16. Noncompaction is the most commonly used term for this affliction, but it presumes an etiology that is disputed whereas ‘excessive trabeculation’ (ET), which we will use henceforth, describes the setting irrespective of the underlying etiology17. So-called true cases are characterized by poor pump function18.Functionally univentricular hearts resemble the setting in the amphibians, where there is a single ventricle onlyFunctionally univentricular heart and ET are rare congenital heart diseases for which almost no valid experimental model systems exist. For the first time, the axolotl will serve as a model to deepen our understanding of the human univentricular heart and its functional anatomy and hemodynamics as well as deepen our understanding of ET. The aim of this study is to characterize heart function and structure of the axolotl hearts in comparison to human cases of DILV and ET.Xenopus hearts that have previously been published19.In total, fifteen axolotls, body mass (BM) = 39.2 ± 25.2 g, total length (TL) = 17.2 ± 4.5 cm, of different color variants  and sex were used in the experiments  solution for 30 min and then maintained on 3 mg l−1 propofol for the rest of the experiment. The entire cardiac region was imaged with a series of 0.25 mm spaced transversal B-mode ultrasound acquisitions with 250 frames (35–45 frames s−1), spanning ~ 3 cardiac cycles pr. acquisition. Reconstructions were made in Amira , as previously described20.Three axolotls (Group A), BM = 17.2 ± 6.3 g, TL = 13.0 ± 1.6 cm, were used for 4D modeling and morphometric analyses of the axolotl heart. Prior to imaging, the animals were anesthetized by immersion in an induction bath of 6 mg lHR), stroke volume (SV), cardiac output (CO) and ejection fraction (EF). Prior to ultrasound imaging animals were anesthetized by immersion in 200 mg l−1 benzocaine (ethyl 4-aminobenzoate) for 30 min. Heart rate was measured in pulsed wave Doppler mode at the outflow tract. Combined myocardium and blood volumes of the heart ventricle at end diastole and end systole were acquired as described above by sweeping the ultrasound transducer across the entire cardiac region to obtain a 4D dataset of the beating heart consisting of at least three cardiac cycles pr. slice. However, as volume estimation does not require the same small step size as modeling, only 9–11 sagittal slices spaced by 1 mm  were acquired at this instance. End diastolic and end systolic ventricle volume (myocardium and blood combined) was calculated by tracing the outer surface of the epicardium in these two cardiac phases for each acquired slice and using the formula:Ai is the area of the ventricle cross-section at the ith slice and n is the total number of slices. Stroke volume was calculated by:CO was calculated by:EF in the trabeculated heart of the axolotl with no well-defined inner border of the cardiac wall, myocardial volume (V(myocardium)) was measured using quantitative histology as described below, and EF was calculated using the formula:Another four axolotls (Group B), BM = 35.1 ± 4.0 g, TL = 18.4 ± 0.3 cm, were used to measure functional parameters of the heart: Heart rate  was used as a negative contrast agent appearing dark compared to blood. Following the initial 4D scan, the inflow of the heart was surgically exposed with a small incision and by lifting a portion of the pectoral girdle out of the way. The sinus venosus was non-occlusively cannulated with a PE20 catheter. The ultrasound transducer was placed over the sinus venosus and correct placement of catheter was verified by injecting a small portion of Ringer’s solution resulting in a dark trace within the sinus venosus. The ultrasound transducer was then positioned over the outflow tract with a short axis orientation to transversally image the origin of the eight gill arches  starting with five cardiac cycles with no infusion for baseline, Ringer’s solution was infused at an increasing rate of 0.01, 0.1, 0.5 and 5 ml min−1 for 30 cardiac cycles (only three cardiac cycles for 5 ml min−1 infusion) separated each with 30 cardiac cycles pause with no infusion to allow for a complete washout and mixing of previously infused Ringer’s solution. Blood signal change in each gill arch was evaluated by measuring average signal intensity at end diastole in all cardiac cycles in regions of interest (area = 0.063 mm2) placed within each gill arch.The same three animals used for 4D modeling (Group A) were used for ultrasonographic evaluation of flow separation in the axolotl heart. Due to the high echogenicity of amphibian blood containing nucleated erythrocytes, isosmotic amphibian Ringer’s solution  of the heart region was recorded with a smartphone camera  while a 10.4 mM solution of Evans Blue was infused at 5 µl min−1 for 1.68 min reaching a total amount of injected dye of 8.4 µl.Two axolotls (Group C), BM = 6.6 ± 0.3 g, TL = 9.8 ± 0.4 cm, were used for visual evaluation of flow separation in the heart using Evans Blue injection. Animals were anesthetized by immersion in an induction bath of 6 mg l−1) amphibian Ringer’s solution, blotted on tissue paper, immersed in Tissue Tek optimal cutting temperature medium in a cryomold and snap frozen on a plastic cradle floating on liquid nitrogen. Subsequently, samples were cryosectioned at a 10 µm slice thickness and a 100 or 200 µm spacing between slices to obtain 24–48 equally spaced slices spanning the entire heart. Tissue slices were digitized with a slide scanner and ventricular tissue volume  was measured using stereology (point counting) as described by Mühlfeld et al.21.Immediately following cardiac functional evaluation with echocardiography the hearts of the four axolotls (Group B) were excised, flushed with heparinized (100 units ml2) using closed respirometry. Before respirometry, resting conscious heart rate was measured using Eulerian video magnification as described by Lauridsen et al.22. A Unisense Clark type oxygen sensor (tip size 25 µm) was calibrated using tempered water bubbled with atmospheric air (20.95% O2) or a 100% oxygen gas respectively. Daily barometric pressure and relative humidity was used to calibrate for vapor pressure. Axolotls were fasted for two days prior to respirometry. Closed respirometry was performed at normal housing temperature of 20.6 ˚C in 1.1 l oxygen impenetrable glass containers for two hours with water samples being withdrawn to measure oxygen content just after respirometer closure and again at the end of the experiment.Six axolotls (Group D), BM = 63.7 ± 17.3 g, TL = 21.0 ± 2.3 cm, were used to measure oxygen consumption rate .The investigation conforms to the principles outlined in the Declaration of Helsinki. The institutional ethics committee approved the conduct of this investigation, and patient informed consent was waived. Patient characteristics were collected retrospectively from medical records and included age, sex, cardiac anatomy and medical history.NYHA class, oxygen saturation measured by pulse oximetry, cardio-pulmonary exercise testing (CPET), echocardiography and cardiac magnetic resonance imaging (CMR) data were collected from the most recent clinic visit.2 (pVO2) was calculated as the mean of the last 30 s during exercise and was indexed for body weight (pVO2 indexed). The pVO2 as percentage of predicted was calculated using reference values24. Adequate performance of CPET was defined as RER > 1.0 in agreement with guidelines for both the pediatric population as well as for adults with heart failure25.CPET was performed on an upright cycle ergometer. Peak VO26 in a sagittal volume over the heart and aorta , in free breathing with a lung-liver respiratory navigator and with prospective ECG gating. The spatial resolution was 2.5 mm × 2.5 mm × 2.5 mm reconstructed into a voxel size of 1.22 mm × 1.22 mm and slice thickness of 0.89 mm. The temporal resolution was 46 ms (19 timeframes) and a velocity sensitivity (VENC) of 90 cm/s was used. Echo and repetition time were 2.9 and 4.6, respectively, and a flip angle of 10° was used. The raw 4D flow DICOM files were processed in GTFlow  including background phase correction, velocity unwrapping and creation of streamline and pathline images.CMR of patient 2 was performed on a 1.5 Tesla system . The CMR protocol included a stack of short-axis slices from the base to the apex of the heart using cine-steady-state free precession with end-expiratory breath holding. Imaging analysis was performed using Qmass . The end-systolic and end-diastolic blood volumes were calculated from the endocardial contours; both the volumes of the dominant and hypoplastic ventricle were included for the calculation of ejection fraction. For ease of comparison, mass-specific cardiac output (ml/min/kg) was calculated. For 3D reconstruction Mimics Medical  was used. To assess blood flow magnitude and direction in patient 3, 4D flow MRI on a 3 Tesla system  was performed according to the consensus statementTransthoracic echocardiography was performed using a commercially available General Electric ultrasound machine with a 3.5 MHz probe. A standardized protocol was used, which included parasternal, apical, subcostal and suprasternal views.27 and adults28.To compare the ventricular wall anatomy of human and axolotl, we re-examined previously published histological sections of normal and excessively trabeculated human ventricular walls of fetusesAll continuous variables are presented as mean  if parametric or as median (interquartile range) if nonparametric. Categorical data are presented as frequency . For all tests, we used SPSS  and we considered P-values less than 0.05 to signify statistical significance.29 and a conus arteriosus30 and electrical activation of which is distinct from that of the atria and ventricles. The human DILV heart comprises the following parts: the left and right atrium, the ventricles  and two arterial outflow tracts. Within the pericardial cavity, in the axolotl the atria are located on the cranial left, whereas the ventricle is on the caudal right. In DILV, the chamber topology is essentially normal with the atria located on the cranial right, and the ventricles on the caudal left. In the axolotl the ventricular apex is very rounded and points caudal-right rather than caudal-left as in human . Together the two ventricles function as a single ventricular unit10. There is variability in the exact location of the hypoplastic ventricle. It is always located on the anterior side of the left ventricle, but can be either left, right, or medial35.The axolotl ventricle is a highly trabeculated chamber with a sponge-like appearance Fig. E. In its12. A valve guards the conoventricular orifice. In the axolotl, the conus lumen comprises a systemic and a pulmonary channel which are separated by the so-called spiral valve. From the conus emerges the arterial truncus arteriosus which has eight channels, one for each of the left–right paired gill arches  with arches 3 to 5 supplying the three paired gills in the axolotl . The 6th arch supplying the lungs, however, did not receive diluted blood showing some capacity for flow separation in the unseptated ventricle  Fig. A. The colar Fig. B. Fetal lar Fig. C. Even ilar Fig. D. In thelar Fig. E,F. Measlar Fig. G. Accordlar Fig. H.Figure 9 and cardiac imaging studies of single ventricle amphibians have been conducted13, however, this is the first study to directly compare human functionally ventricular hearts to those of the axolotl. Analyses of blood gasses38, injection of X-ray contrast39, and UV-light activated fluorescence12 have been used previously to show degrees of streaming in the salamander and anuran amphibian ventricles. Here, we used micro-echocardiography for visualization of streaming in the axolotl single ventricle with Ringer’s solution as a contrast agent which should be innocuous albeit a substantial injected volume was necessary to get good visualizations. Furthermore, this is the first study to use 4D MRI for visualization of streaming in a human DILV without Fontan circulation.The axolotl has attributes that could make it an interesting model for human DILV and ET. Both in the axolotl as well as in DILV, disparate blood flows can stay separated in a single ventricle through streaming. This may be possible through an interplay of various anatomical characteristics that lead to a separation with flows staying separated on either side and being directed along the inner and outer bend of the single ventricle. For the axolotl, this is the natural situation, whereas for humans, albeit not ideal, it can aid in facilitating survival for those born with functionally univentricular hearts, and, in the most favorable cases, may allow for a higher life expectancy and better quality of life than those observed in Fontan patients. Differences were found with regards to anatomy, most importantly, the axolotl having a common ventricular inlet and outlet, whereas in DILV, there are two separate inlets and outlets. Moreover, it was established that the trabeculations found in ET are closer to the normal human setting than to the axolotl setting. A few case series of DILV survivors are described in the literature so far40. The range of values in this study falls well within previously reported heart rate for awake and anesthetized axolotls40, generally showing a subtle tachycardia effect of propofol and a more pronounced effect of benzocaine. Resting heart rate in the axolotl was much lower than in DILV . Cardiac output of the axolotl under anesthesia, when corrected for body mass, is similar to that in DILV patients at rest. Because mass-specific CO is dependent on body mass, the values tend to be greater in lighter animals. The fact that the values for CO are comparable in human and axolotl could thus be accounted to a chance effect of the sizes (as well as the endo- vs. ectothermic state) of these two species. The ejection fraction in the axolotl reported here is lower than that in DILV patients, however this may reflect a short and incomplete contraction of the ventricle during benzocaine anesthesia, which can be observed when comparing to echocardiography on awake animals. In amphibians, the highly trabeculated ventricle feed the systemic circulation with blood pressures that are much lower than in human, also DILV, with a mean systemic arterial blood pressure of 20–30 mmHg41. Oxygen consumption in the ectothermic axolotl at 20.6 °C is lower than in endothermic healthy human, but comparable to DILV patients.Cardiac function in the axolotl is known to be affected by the use of anesthetics42. This study showed that in the single ventricle of the axolotl and in DILV, favorable streaming, meaning little-to-no mixing of oxygen-rich and oxygen-poor blood, is possible. The possibility of favorable streaming has previously been acknowledged45. It offers an explanation for why certain DILV patients have high systemic oxygen saturations even though both oxygen-rich and oxygen-poor blood enter the same ventricle. Certain anatomical constitutions in both DILV patients as well as the axolotl may facilitate this favorable streaming. In the axolotl, the atria are located on the left, whereas the ventricle and the conus arteriosus is located on the right. We postulate that the blood from one atrium, due to its location, will stay on one side, whereas blood from the other atrium will stay on the other side, leading to streamlining in the ventricle up to the point where the blood flows enter the outflow tract. In DILV, there is more variance with regards to the spatial relationship of the inflow-and outflow tracts35. Ideally, similar to the axolotl, the atria and atrioventricular connection are positioned in a way that blood from one atrium may enter the ventricle and stay on one side, taking the outer bend toward the correct outflow tract, whereas blood from the other atrium may enter the ventricle on the other side and take the inner bend toward the correct outflow tract. This configuration was seen in patient 2, who has favorable streaming with normal systemic oxygen saturation. The presence or absence of pulmonary vasculature protection7 can also influence streaming. DILV patients who do not have restriction of pulmonary blood flow inevitably develop Eisenmenger syndrome (patient 3). Although it was demonstrated that blood flows are also partially separated, patient 3 has lower oxygen saturations due to right-left shunting. When the pulmonary vasculature is protected by pulmonary stenosis, as in patient 1 and 2, oxygen saturations are higher.Streamline flows as those entering into the ventricle do not have an intrinsic tendency to mix unless forced by turbulenceAs opposed to DILV, there is no complete separation on the atrial level in the axolotl, and there is a common atrioventricular valve instead of two separate inlets. Furthermore, the axolotl has a common ventricular outlet through the conus arteriosus, whereas in DILV there are two outlets. Another difference is the trabeculation pattern. We found that the axolotl ventricular trabeculations are much smaller in size and much greater in number than in human, even when compared to ET. The trabeculations in ET resembles the normal human setting in a higher degree than the axolotl setting.This is a small study that focused on qualitative evaluation and comparison. The results and conclusions are therefore of a somewhat theoretical nature. Especially with regards to possible treatment options and alternatives to the Fontan circulation, larger-scale studies and quantitative analyses are needed in order to find the best, individualized approach for each patient.49.This study shows that it is possible for DILV patients to survive and live without Fontan circulation. Although their exercise tolerance was reduced in varying degrees, these patients had a preserved NYHA class and heart function. This can be seen in contrast to patients with a Fontan circulation, where long-term longevity and quality of life is limited due to the un-physiological character of the Fontan circulationThis is the first study comparing human survivors of DILV and ET to the axolotl heart and circulation. The most important observations are that ET resembles the human setting more than that of the axolotl, and that both in the axolotl as well as in human DILV, disparate blood flows from the two atria can stay separated in a single ventricle through streaming. This study lays the groundwork for future studies focusing on identifying those selected DILV patients that might benefit from non-Fontan palliation, for example by means of a form of pulmonary artery banding.Supplementary Information 1.Supplementary Information 2.Supplementary Video 1.Supplementary Information 3.Supplementary Information 4.