Aim: Knowledge of the human body’s ability to adapt to repeated endurance efforts during swimming is limited. We echocardiographically assessed the impact of an exhausting and repetitive swimming effort on cardiac activity.Materials: Fourteen well-trained amateur swimmers  participated in an ultramarathon relay. Over 5 days, swimmers swam 500 km in the Warta River . Each swimmer swam seven intervals, each within 44:46 to 60:02 min. Objective difficulties included low water temperatures, strong winds, rain, and night conditions.Methods: Transthoracic echocardiography (TTE) was performed three times: at baseline (the day before exertion), at peak effort, and during recovery (48 h after the event). The heart rate (HR) of each swimmer was monitored.Results: Swimmers completed the ultramarathon relay within approximately 91 h. The average HR value at the end of each interval was 91% HRmax. TTE test results showed no significant changes indicative of deterioration of myocardial function at peak effort or after 48 h. Significant increases in left ventricular (LV) ejection fraction, LV fractional shortening (LVFS), LV myocardial systolic velocity, and right ventricular (RV) fractional area changes observed on day 2 after swimming were compared to baseline values and peak effort values. No significant changes in diastolic heart function were observed.Conclusion: Echocardiography assessment indicated that prolonged intense swimming does not affect LV or RV function. Supercompensation of the post-event RV function and increased global LV systolic function demonstrated ventricular interaction after prolonged intense swimming. Knowledge regarding the adaptations of the human body following long hours of exhaustive swimming is limited . HoweverAlthough the benefits of systematic training for physiological capabilities and the health status of athletes are indisputable, numerous studies have indicated that multi-hour, exhausting physical effort may cause heart rhythm disturbances, heart attacks, and even sudden death during or after exertion . DetermiThe aim of our study was to evaluate several vital functions during and after exhausting, repetitive endurance swimming of a group of well-trained, but not elite, swimmers. The swimmers included females and males aged 13–67 years who participated in a 500-km ultramarathon swim relay in open water. Our study included several anthropometrical, biochemical, hematological, and hemostatic parameters and evaluated endothelium function and intraocular pressure. We describe data related to the influence of endurance swimming on cardiac function and structure. We hypothesized that repeated exhausting effort, such as long-distance swimming in a relay swimming ultramarathon, may adversely affect cardiac function, as assessed by echocardiography.2max values obtained during a stress test performed on a moving treadmill indicated that the swimmers were not high-performance athletes with very high aerobic capacity . Only athletes who completed the relay and for whom we possessed echocardiographic data of all three measurements  were included in the statistical analysis. One 15-year-old girl was unable to continue the event on the third day due to acute symptoms of airway inflammation. She was examined by experienced physicians and withdrawn from the relay. Notably, she was free of serious health-related symptoms within 2 days. Another participant, a 43-year-old woman, successfully completed the event, but was unable to participate in the final echocardiography examinations, which were performed 48 h after the event, due to professional obligations. The detailed demographic, clinical, and echocardiographic characteristics of the subjects are reported in capacity .2max) during a mobile treadmill test, biochemical blood tests, and an eye examination, at the Department of Sports Medicine of the Medical University of Łódź.The organizers of this extraordinary swimming ultramarathon carefully prepared the entire event while considering the physical and psychological preparations of the relay participants and their safety during the many hours of swimming. All participants had been regularly swimming for at least 5 years, usually 2 to 3 times per week for 45 to 60 min each time. Importantly, the swim ultramarathon participants were mostly well-trained, but non-competitive, athletes. During the 6 months preceding their participation in the ultramarathon, swimmers increased both the frequency and duration of their swimming training. Several training sessions were conducted in natural water reservoirs (lakes and rivers) at low air and water temperatures and at night to adequately prepare them for the upcoming ultramarathon. During the last 5 days before the relay event, the swimmers only participated in light training in the form of warm-up exercises to fully rest before the swimming ultramarathon. During the 2 to 3 weeks before the swimming ultramarathon, all swimmers participated in specialized sports medical tests, including detailed interviews and a medical examination, electrocardiogram (ECG), spirometry test, measurement of maximum oxygen consumption . Each test was performed using the same equipment. All studies were performed and interpreted by a single experienced investigator.m), early diastolic (Em), and late diastolic (Am) velocities were measured by placing the sample volume at the septal and lateral angles of the mitral annulus, and the average values of each velocity were calculated. Similarly, pulsed tissue Doppler was used with the sample volume positioned at the lateral corner of the tricuspid annulus to assess its velocity (RV Sm).Participants underwent standard Doppler echocardiography using an ultrasound imaging system  with a 2.5-MHz transducer and Doppler tissue imaging. Echocardiographic variables, including the left ventricular (LV) end-diastolic diameter, LV end-systolic diameter, septal and posterior wall thicknesses, RV end-diastolic diameter, and left atrial diameter (LAD), were recorded in the parasternal view. LV fractional shortening (FS) was calculated as the percentage change in the LV systolic and diastolic dimensions. The LV ejection fraction (LVEF) was calculated using Simpson’s biplane method. The Doppler-derived LV diastolic inflow was recorded in the apical four-chamber view by placing the sample volume at the level of the leaflet tips. In the same view, the RV end-diastolic and end-systolic areas were measured, and the RV fractional area change (FAC) was calculated. Additionally, the tricuspid annular plane systolic excursion (TAPSE) was acquired using the conventional M-mode method at the lateral tricuspid annulus. The LV myocardial tissue Doppler peak systolic (SHeart rate (HR) measurements during the exercise were performed using Polar V800 HR monitors . The results were analyzed by a cardiologist with extensive experience.post hoc test. Parameter characteristics are presented as the average value (± standard deviation). All statistical calculations were performed using STATISTICA 12 software. The significance level was set as p < 0.05.Significant differences between consecutive measurements using echocardiography  were analyzed by an analysis of variance (ANOVA) Friedmann test followed by a Friedmann The swimming ultramarathon was organized for charity. Both young and very experienced amateur swimmers participated to raise a considerable amount of money for the Oncology, Hematology, and Pediatric Transplantology Clinic in Poznań.The athletes provided written consent to participate in the swimming ultramarathon, to participate in the aforementioned study, and to have their results published. Parents provided written consent for the teenage swimmers to participate in the swimming ultramarathon and all biomedical tests. Approval was obtained from the Bioethics Committee of the Medical University of Łódź to perform biomedical monitoring of the Warta Marathon participants.The average HR value at the end of each shift was 91% HRmax (169 bpm). The average HR during the effort was 157 bpm. This was 84% of the average maximum HR of all athletes. The maximum HR was the value reported by the athletes after previous maximum swimming efforts, such as tests or competitions (in two cases). The HR values of the individual competitors are shown in Echocardiographic studies showed no obvious LV wall hypertrophy, with a mean septal thickness of 0.88 ± 0.08 cm and a mean posterior wall thickness of 0.84 ± 0.14 cm . All indRegarding the global systolic LV function, compared to measurements obtained at baseline and at peak effort, significant increases in the LVEF and LV shortening fraction were observed during recovery. Similarly, the myocardial systolic peak velocity (Sm) was higher 2 days after swimming .m/Am and E/Em ratios did not change during or after swimming.Left ventricular diastolic function, as assessed by the standard transmitral flow, was not affected by the extreme exercise . Similarm) did not significantly differ between consecutive measurements  during individual sections of the swimming ultramarathon. Based on these values, we determined whether the intensity of the effort was high, very high, or maximum  Table 7Table 7. Swimmers completed the ultramarathon relay within approximately 91 h. Considering the length of the swimming sections (5 km), the duration of the effort, the number of repeated trials (seven times), the special conditions (the need to swim at night and in low water and air temperatures), and the HR values reached during each shift, the relay was considered exhaustive or extremely difficult .The data from our study strongly demonstrate that intense prolonged repeated bouts of swimming in open water in difficult environmental conditions did not negatively influence the heart function.Echocardiography assessment indicated that prolonged intense swimming does not affect LV or RV function.In the group of swimmers included in this study, atrial enlargement or deterioration of the RV or LV systolic function was not observed during the echocardiographic evaluations of the heart.Transthoracic echocardiography (TTE) test results showed no significant changes indicative of deterioration of myocardial function at peak effort or after 48 h. Regarding the systolic function of both chambers, compared to the baseline values and the values at peak effort, significant increases in the EF and FS of the left ventricle, myocardial LV systolic velocity, and RV FAC were observed on day 2 after completing swimming. No significant changes in the diastolic function of the heart were observed.We did not observe a significant decrease in the echocardiographic parameters when assessing RV function during the post-swimming examination. TAPSE and RV systolic velocity illustrating the function of RV longitudinal fibers did not change; moreover, compared to assessments made at baseline and at peak effort, the RV FAC significantly increased during recovery. A possible explanation for this phenomenon might be that the FAC describes not only longitudinal but also oblique and circular myofibers that appear to enhance its function to address the exercise-induced increased contractility demand. Therefore, our study showed that the right ventricle copes with the increase in load during swimming even if the intense exercise is maintained for a long duration and is repeated during a short period. The supercompensation of the post-event RV function and the increase in the global LV systolic function demonstrated the ventricular interaction after high-intensity swimming.Moreover, while analyzing separately the individual echocardiographic data of al 500-km relay participants, we did not detect any changes that could be interpreted as signs of cardiac “fatigue” dysfunction, or any other cardiac pathology.The observed changes did not suggest that long-distance swimming caused changes in the echocardiographic parameters of the tested athletes, thus demonstrating no harmful effect on the hearts of athletes.Studies investigating changes in LV function following prolonged intense exercise have yielded inconsistent data, and studies involving swimmers are scarce . Cahill Regarding the Doppler-derived diastolic parameters, no significant changes were observed in the LV filling pattern in this study. A previous study showed that after ultra-endurance exercise, the peak early transmitral filling velocity significantly decreased . In contPrevious studies have revealed that intensive endurance exercise may lead to RV dysfunction, and that the degree of RV functional impairment depends on the duration of the exercise .Numerous studies have shown that certain cardiac arrhythmias and their preceding morphological and functional changes in the heart are more common in high-performance athletes than in their inactive peers. These arrhythmias include paroxysmal atrial fibrillation and atrial flutter , and atrIt should be noted that, in our study, the effort was performed during approximately 45- to 60-min sessions. The resting time between sessions may have allowed partial RV recovery (and possibly LV recovery). In practice, the time from leaving the water by the swimmer until the next shift was 9 h. Accordingly, a repetitive exercise pattern might yield a different cardiac adaptation than swimming 25 km consecutively , swimminThe main strengths of our study were the unique exercise protocol and comprehensive monitoring of various important vital functions during and after the ultramarathon. Each athlete performed several intensive swimming endurance exercise sessions in open water during the day and night under difficult environmental conditions. Moreover, other than two very experienced master athletes who were champion endurance swimmers, most swimmers had not been previously involved in competitive swimming training, although all had experience with long-distance swimming. Despite the age groups used in other studies, we included both females and males of various ages in our study. Echocardiography was performed by the same cardiologist with extensive experience with similar studies. A member of our study team was constantly with the swimmers to monitor the necessary physiological parameters and report potential adverse effects. The biochemical, hematological, anthropometric characteristics, intraocular pressure, and endothelium function analyses are currently being prepared by our research group for publication in another article.The main limitation of this study was that monitoring of the cardiac, hematological, and biochemical adaptations to prolonged repetitive swimming was performed for a relatively small group of athletes. As previously mentioned, we obtained echocardiography data of 12 males and females. The echocardiographic analysis was limited to standard two-dimensional, Doppler, and tissue Doppler studies. Regional myocardial deformation was not performed. We analyzed a heterogeneous group of swimmers that included adolescents (13- to 16-year-old participants) and adults . However, cardiac adaptations and remodeling may significantly change in adolescents and between sexes . The effIn summary, the results of this study indicated that prolonged intense swimming does not affect LV and RV function, as assessed by echocardiography.Echocardiography assessment indicated that prolonged intense swimming does not affect LV and RV function. Supercompensation of the post-event RV function and the increase in the global LV systolic function demonstrated ventricular interaction after prolonged intense swimming.All datasets generated for this study are include in the manuscript and/or the This study was carried out in accordance with the recommendations of Resolution No. RNN/230/16/KE of July 12, 2016, Bioethics Commission at the Medical University of Łódź with written informed consent from all subjects. All subjects gave written informed consent in accordance with the Declaration of Helsinki. The protocol was approved by the Bioethics Commission at the Medical University of Łódź.RG and WD conceived the study. WD, MK, ER, and MN designed the study details and supervised the data collection. SR, ER, RG, MK, MN, and WD contributed significantly to data collection. RG, EK, PH, and WD participated in writing the paper and checking the draft for errors. WŚ was the statistician and was involved in designing the study. RG, WD, and EK written by the final version of the manuscript. All authors read and accepted the final version of the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Point-of-care ultrasound is increasingly being used as a diagnostic tool in resource-limited settings. The majority of existing ultrasound protocols have been developed and implemented in high-resource settings. In sub-Saharan Africa (SSA), patients with heart failure of various etiologies commonly present late in the disease process, with a similar syndrome of dyspnea, edema and cardiomegaly on chest X-ray. The causes of heart failure in SSA differ from those in high-resource settings. Point-of-care ultrasound has the potential to identify the underlying etiology of heart failure, and lead to targeted therapy. Based on a literature review and weighted score of disease prevalence, diagnostic impact and difficulty in performing the ultrasound, we propose a context-specific cardiac ultrasound protocol to help differentiate patients presenting with heart failure in SSA.Pericardial effusion, dilated cardiomyopathy, cor pulmonale, mitral valve disease, and left ventricular hypertrophy were identified as target conditions for a focused ultrasound protocol in patients with cardiac failure and cardiomegaly in SSA. By utilizing a simplified 5-question approach with all images obtained from the subxiphoid view, the protocol is suitable for use by health care professionals with limited ultrasound experience.The “Cardiac ultrasound for resource-limited settings (CURLS)” protocol is a context-specific algorithm designed to aid the clinician in diagnosing the five most clinically relevant etiologies of heart failure and cardiomegaly in SSA. The protocol has the potential to influence treatment decisions in patients who present with clinical signs of heart failure in resource-limited settings outside of the traditional referral institutions. Point-of-care ultrasound is increasingly being used as a diagnostic tool in resource-limited settings. With more portable and affordable machines, providers from small clinics to large hospitals have increasing access to this technology. The majority of ultrasound protocols aimed at cardiac pathology have been developed and implemented in high-resource settings where more advanced imaging technology is usually available to help the clinician confirm their ultrasound diagnosis. As cardiovascular disease is an increasing cause of morbidity and mortality in sub-Saharan Africa (SSA) , there iIn SSA, patients with heart disease often present late in their clinical course with signs and symptoms of heart failure . The etiPatients with heart failure of various etiologies commonly present with a similar syndrome of dyspnea, edema and cardiomegaly on chest X-ray. In tropical settings common cardiac causes of dyspnea and edema are dilated cardiomyopathy , hypertensive cardiomyopathy, pericardial effusion with tamponade (most commonly due to TB), post-rheumatic heart disease (RHD) and cor pulmonale , 8. PoinA large body of evidence has demonstrated the feasibility and clinical utility of point-of-care cardiac ultrasound performed by non-cardiologists –13. In SAs ultrasound becomes more ubiquitous, there is a need for context-specific training protocols. In the following pages, we outline a cardiac ultrasound protocol specifically for providers working in sub-Saharan Africa (SSA). This protocol is based on a literature review of locally prevalent conditions, and created for ease of use both in regards to performing ultrasound with basic B mode software capabilities and for teaching cardiac ultrasound in a way that is most relevant for healthcare professionals in SSA.We searched PubMed with the following search string: “Africa” [MeSH Terms] AND “heart diseases” [MeSH Terms] and extracted information on the frequency of causes of heart failure. Our search was conducted on 1 August 2018, and an additional search on 11 October 2019. We limited our search to papers published in the last 5 years and relevant references cited herein published within the last 10 years. We excluded papers focusing on pediatric populations, ECG findings, surgery, cardiovascular risk or stroke, studies outside SSA, case reports and studies focusing on clinical characteristics of specific groups, such as HIV patients or patients with congenital heart disease. Review papers were included to search for additional relevant references. Geographic area, number of assessed patients and relative frequencies of underlying conditions were extracted. These data were subsequently used to identify the most relevant conditions that need to be assessed in a cardiac ultrasound protocol.Given that our goal is to create a protocol that is most relevant for clinicians in resource-limited settings, epidemiology was combined with ease of use and predicted clinical relevance to create a scoring system that would identify the high-yield ultrasound applications. Each application was assessed on three components: disease prevalence, diagnostic impact, and ultrasound difficulty Table . The wei878 titles and abstracts were screened; nine papers provided relevant information on etiologies of cardiac failure in SSA –28, nineBased on the 5 highest ranking conditions Table , we propPericardial effusion is easily identified in a subxiphoid view and usually presents as an anechoic rim around the heart. If a significant pericardial effusion is present, the heart should be evaluated for signs of tamponade. If jugular veins are distended, the patient has tachycardia and low blood pressure, obstructive shock and tamponade may be present. Right atrial systolic collapse and right ventricle (RV) diastolic collapse suggest tamponade physiology. It is important to be aware that if the rate of fluid accumulation is rapid, even a small effusion can cause hemodynamic compromise. In a patient with cardiac tamponade emergency pericardiocentesis can be life-saving. In resource-limited settings an ultrasound-guided intercostal approach with a simple cannula can be used .Dilated cardiomyopathy can have multiple causes, but sonographically, the end stage is similar with global enlargement of both atria and ventricles with reduced left ventricular systolic function. Unfortunately, most symptomatic patients present in a late stage of the disease. Formal measurement of the ejection fraction and assessment of regional wall motion abnormalities is mostly confined to referral centers as it requires dedicated echocardiographic software and substantial experience. However, a broad classification of left ventricular contractility as hyperdynamic, normal, moderately impaired and severely impaired, can be made by estimating whether contraction is symmetrical towards the center, whether the myocardium thickens as it contracts, and whether the mitral valve opens normally during diastole. In an enlarged heart, this can usually be achieved in a subxiphoid view.An enlarged RV can indicate cor pulmonale. Cardiac ultrasound can demonstrate sonographic features of cor pulmonale by evaluating shape, size and pressure of the right side of the heart. In the subxiphoid view, in the presence of a normal-sized left ventricle (LV), the RV is typically 2/3 the size of the LV, any larger suggests RV enlargement. If the RV is equal in size to the LV, it is considered moderately enlarged. Pronounced dilatation of the RV such that it is larger than the LV is considered severe RV enlargement and cor pulmonale may be considered. In addition, movement of the intraventricular septum away from the RV indicates increased right ventricular pressure or volume, resulting in a D-shaped LV in the parasternal short axis view . The measurement of RV contractility and the calculation of the pressure gradient in the setting of tricuspid regurgitation can be helpful. However, this is technically more difficult and requires Doppler software, so it is best reserved for referral sites.An enlarged left atrium (LA) is a feature of mitral stenosis and/or regurgitation, which may serve as a surrogate marker for RHD. The LA often becomes larger than the normal-sized LV by the time the patient presents. Additional findings include a thickened mitral valve with a diastolic hockey stick appearance or “doming” of the valve leaflets. The right heart may also be enlarged due to the subsequent increase in pulmonary pressures. Post-rheumatic changes of the aortic valve are slightly more difficult to detect as they initially lead to left ventricular hypertrophy only and the aortic valve is more difficult to visualize on ultrasound from a subxiphoid view. The morphological assessment of the aortic valve is possible at referral centers, as is the detection of mitral and aortic regurgitation if color-Doppler is available. For the basic CURLS exam, these questions were not included.Left ventricular hypertrophy can be determined by measuring the intra-ventricular septum (IVS) at end diastole. The standard measurement of the IVS is performed in the parasternal long axis view and should be less than 12 mm. Nevertheless, the septum is generally visible in the subxiphoid view. The clinician should freeze the screen and scroll back to end diastole where the IVS is measured at the level of the mitral valve leaflet tips.The clinical syndrome of heart failure is prevalent around the world. However, the underlying pathology differs significantly between resource-limited and resource-affluent settings. Ischemic heart disease is the main underlying cause in high-resource settings, but is only observed in a minority of patients in SSA. On the other hand, dilated cardiomyopathy, RHD and pericarditis (mostly TB-related) are important causes of heart failure in resource-limited settings, which are less prevalent in high-resource settings. Limited cardiac ultrasound can play a significant role in differentiating between underlying causes. Based on our analysis of the frequency of cardiac conditions, the impact on treatment decisions and the ease of use, we identified five cardiac conditions relevant to SSA for the CURLS protocol. The protocol should serve in emergency departments or acute patient settings and is not intended for screening asymptomatic patients.Our literature search identified hypertension as the most common cause of heart failure followed by dilated cardiomyopathy and valvular causes. Pericardial effusion and cor pulmonale were less frequently reported, but play a significant role in sub-populations such as HIV-infected patients. Our suggested “cardiac ultrasound for the resource-limited setting” (CURLS) protocol aims to identify these conditions in the “5-question” approach summarized in Box Ultrasound protocols designed specifically for resource-limited settings have proven effective in SSA. Heller et al. demonstrated that the FASH (focused assessment with sonography for HIV-associated tuberculosis) exam could be efficiently taught to ultrasound-naïve clinicians over a 2-day training period . The FASSome limitations of the protocol should be highlighted. The protocol has not been validated in clinical practice, so its sensitivity and specificity still need to be determined. While the use of only the subxiphoid view simplifies the protocol for non-expert sonographers, it is possible that the image quality is insufficient in some patients. Furthermore, as with any focused protocol, it is not a replacement of an expert cardiology ultrasound and difficult cases should be referred for more extensive workup. Finally, no evidence is available that the protocol enhances diagnosis of cardiac pathologies in resource-limited settings. Hence, the protocol we outline here is set forward as a research agenda and discussion point to encourage all providers to think about how the incredible potential of ultrasound can become more context specific for both patients and providers. Future studies need to assess if the CURLS protocol is trainable and whether significant cardiac findings are missed in comparison to “full specialist” echo exam even though this is not widely available.Based on the epidemiology of heart disease in sub-Saharan Africa and expert consensus on difficulty and impact of cardiac sonographic examinations, we propose a protocol for screening symptomatic patients with signs of heart failure and/or cardiomegaly on chest X-ray in resource-limited settings. This protocol is unique in that uses primarily the subxiphoid view and is designed to have high clinical relevance whilst being easy to use for providers at the front line of patient care in these settings. The protocol assesses pericardial effusion, dilated cardiomyopathy, cor pulmonale, mitral valve disease, and left ventricular hypertrophy. The protocol has great potential to influence treatment of patients with heart failure in resource-limited settings. Future studies are needed to evaluate whether the protocol can easily be taught and implemented by clinicians, and if ultrasound findings have a positive influence on treatment decisions without missing important findings that would be observed by a specialist echocardiogram.Additional file 1: Figure S1. Literature search flowchart. Table S1. Baseline characteristics of included studies on etiologies of cardiac disease in SSA (2008–2018).Additional file 2. Normal heart.Additional file 3. Pericardial effusion.Additional file 4. Dilated cardiomyopathy.Additional file 5. Right sided heart failure.Additional file 6. Rheumatic heart disease with mitral valve dysfunction.Additional file 7. Left ventricular hypertrophy.


Left ventricular ejection fraction (LVEF) is the most frequently used parameter in the assessment of heart failure (HF). Cardiac index (CI) is considered a potential alternative to LVEF despite limited evidence. We aimed to assess and compare the predictive accuracy of LVEF and echocardiographically-assessed CI in HF patients.A single-centre, retrospective cohort study was conducted in patients hospitalized for acute HF from 2010–2016. Cox proportional hazard models including either LVEF or CI were created to predict all cause death, cardiovascular (CV) death, or first HF-readmission. Of 334 patients included in the analysis, 58.7% exhibited HF with reduced LVEF (HFrEF). Left ventricular ejection fraction did not show correlation with any endpoint, while CI was predictive of HF-readmission in the entire cohort. Both the LVEF-based and CI-based models demonstrated moderate discriminative accuracy when predicting all-cause death, CV death, or HF-readmission. Left ventricular ejection fraction proved to be an independent predictor of CV mortality in HFrEF-patients, while CI was predictive of HF-readmission in the non-HFrEF group.Left ventricular ejection fraction seemed to be associated more closely with disease severity in HFrEF, and CI in the non-HFrEF group, in this real-life cohort of elderly HF patients. The LVEF-based and CI-based predictive models have clinically similar predictive accuracy for mortality and HF-readmission, thus CI may be a potential alternative to LVEF in the assessment of left ventricular function. Cardiac index may be an important new tool in the assessment of HF patients with midrange or preserved LVEF. Heart failure (HF) affects a large segment of the population worldwide, and has a mortality risk comparable to malignancies., 2 The dEarly studies identified left ventricular ejection fraction (LVEF) as a useful, easily obtainable, prognostic echocardiographic parameter. Low LVEF is correlated to reduced cardiac output (CO), cardiac index (CI), and poor tissue perfusion and has been shown correlated with increased risk of mortality and morbidity., 6 TheseCardiac output and cardiac index have also been shown to correlate with mortality, but theiThe current research aims to compare the predictive value of LVEF to that of CI-based models for mortality and re-hospitalization in an unselected HF population in a retrospective study.We conducted a retrospective cohort study comprising patients hospitalized for HF from 2010–2016 at the Heart-Lung Clinic of Örebro University Hospital, Sweden. Patients were eligible for inclusion if the primary reason for hospital admission was acute HF, if they had an echocardiography after admission with stored images available for post-hoc measurement of CI, and were at least 18 years old at the time of echocardiography. If a patient had more than one admission matching the inclusion criteria during the study period, only the first such event was taken into account. Patients were excluded if they presented any cardiac condition that would affect the measurement of CI, for example moderate or severe aortic valve disease, hypertrophic obstructive cardiomyopathy or congenital heart disease, or if they did not fulfil the diagnostic criteria of HF according to the 2016 guidelines of the European Society of Cardiology (ESC). No criteCI = LVOT − VTI * HR * LVOTd2 * 0.7854/BSA. Left ventricular outflow tract diameter (LVOTd) was measured from parasternal long axis images, as close to the aortic valve as possible. Left ventricular outflow tract velocity-time integral (LVOT-VTI) was measured on pulsatile doppler LVOT flow pattern images obtained from an apical 5-chamber view. LVOT-VTI was assessed on as many cardiac cycles as possible (maximum of 5) and the average of these measurements was used in the calculation of CI, in order to reduce possible inaccuracies caused by arrhythmias. Measurement bias of LVOTd and LVOT-VTI due to potentially suboptimal imaging plane and angle deviation could however not be eliminated due to the retrospective setting of the study. Mean cardiac cycle length (CCL) was assessed by measuring and averaging the duration of the cardiac cycle of LVOT-VTI measurements from the end of the ejection period of the previous systole to the end of the index ejection period. Heart rate (HR) was then calculated as HR = 1/CCL. Body surface area (BSA) was calculated using the DuBois-formula.All echocardiographic examinations were performed and analysed by experienced echocardiographers. Left ventricular ejection fraction was assessed during initial examination, and a different echocardiographer assessed CI values retrospectively, blinded to outcomes. Cardiac index was calculated as Endpoints were defined as all-cause death, cardiovascular (CV) death, or first HF-related hospital readmission. Information on HF-related readmission was obtained from electronic patient journals. Mortality and date of death were obtained from the Swedish Death Registry. Cause of death was assessed by two independent investigators based on available patient journals and, in cases of discrepancy, adjudicated by a third.Prognostic models were created using the Cox proportional hazard method including either LVEF or CI together with available traditional risk factors for HF: age, sex, diabetes, ischemic aetiology, chronic obstructive pulmonary disease (COPD), glomerular filtration rate (GFR), body mass index (BMI), atrial fibrillation, and heart rate. Data of traditional risk factors for morbidity and mortality with HF were collected by manual search in patient electronic journals. The diagnosis of heart failure was confirmed using the diagnostic criteria for heart failure with reduced ejection fraction , mid-range ejection fraction  and preserved ejection fraction  as described in the 2016 guidelines of the ESC. ClinicalCategorical variables were compared using chi-square test and unpaired two-tailed t-test was used for the comparison of continuous variables. Discriminative accuracy of the prediction models was assessed by Harrell’s c-index, with standard deviation obtained by the jack-knife method and compared by unpaired t-test. The P-value of 0.05 was considered significant.The investigation conforms to the principles outlined in the Declaration of Helsinki and was approved by the Regional Ethical Review Board in Uppsala, Sweden. Data on patient demographics and outcomes were collected from the patients’ electronic medical records and the Swedish Death Registry, and linked to echocardiographic data by personal identification numbers. All data was anonymized before further processing. The Regional Ethical Review Board did not waive any requirement for informed consent.2. The majority of subjects were >70 years old and had multiple comorbidities. All patients received guideline directed medical treatment. Medications and devices applied after the index hospital admission and after treatment optimization are shown in We found 1823 acute HF-related hospital admissions of 1274 individuals during the study period. Lack of echocardiography after hospital admission excluded 456 patients from the study, and 139 were excluded due to the presence of moderate to severe aortic valve disease or hypertrophic obstructive cardiomyopathy. Of the remaining 679 patients, echocardiography images necessary for CO measurement and documented height and weight needed for BSA calculation at the time of echocardiography were available for 339. Five patients exhibited LVEF≥40% and elevated natriuretic peptides but presented no echocardiographic evidence of diastolic dysfunction or structural heart disease, so did not fulfil the diagnostic criteria of HF. The final subject group of 334 patients was a heterogeneous population comprising patients with reduced ejection fraction (HFrEF) (n = 196), mid-range ejection faction (HFmrEF) (n = 65), or preserved ejection fraction (HFpEF) (n = 73) and included those with newly diagnosed HF before treatment optimization as well as patients with a long history of HF, already on optimal medical treatment at the time of admission. Patient baseline characteristics are shown in 2 vs. 30.5±11.3 ml/ m2, p = 0.0005) and higher heart rate , resulting in lower CI ; however this difference did not reach statistical significance. As irregular heart rhythm leads to beat-to-beat changes in SVI and CI, intra-observer variability assessment was limited to the subgroup of 179 patients with sinus rhythm and at least 2 cardiac cycles. The absolute intra-observer variability for SVI was 0.2±3.9ml/m2 (relative variability 0.5±13.0%). For single beat estimates of CI, intra-observer variability was 0.01±0.24 l/min/m2 (relative variability 0.1±10.7%).A total of 1133 cardiac cycles were analysed. Patients with atrial fibrillation had more cardiac cycles available than those with sinus rhythm . They had significantly lower stroke volume index . Cardiac index was not associated with all-cause death (P = 0.271) or CV death (P = 0.209) but showed significant association with HF-readmission (P = 0.020).One-hundred-seventy-three patients died , and 133 underwent HF-related hospital readmission during 2.3±1.9 years of follow-up. On univariate Cox proportional hazards analysis, LVEF was not associated with all-cause death, CV death, or HF-readmission . Cardiac index showed no correlation with all-cause or CV death but remained an independent predictor of HF-readmission . The risk ratios of the final prediction models in the overall cohort are presented in When adjusted for traditional risk factors, LVEF showed no significant correlation with the endpoints (P < 0.001), CV death , and HF-readmission , with slight but significant difference in all cases.Both the LVEF-based and CI-based models had moderate discriminative accuracy when predicting all-cause death . Cardiac index showed a strong association with all-cause death but did not demonstrate correlation with CV death or HF-readmission. After adjustment for other risk factors, neither LVEF nor CI showed correlation with all-cause death or HF-readmission, but LVEF became an independent predictor of CV death .In the combined group of 65 HFmrEF and 73 HFpEF patients, neither LVEF nor CI was individually predictive of all-cause death or CV death. LVEF had no correlation with HF-readmission; however CI showed a significant association with HF-readmission. On adjusted analysis, CI proved to be an independent predictor of HF-readmission but not of all-cause or CV death, while LVEF had no independent predictive value for any endpoint .Our study fills a gap in information on echocardiographic measures of cardiac function. Left ventricular ejection fraction is used routinely as standard for the diagnosis and management of HF, however the moderate accuracy of the LVEF measurement raises concerns when using cut-off values as indication for potentially life-saving treatment. Earlier In contrast to earlier invasive studies of younger patients showing a strong association among LVEF, CI, and prognosis, our results show that both LVEF and CI measured by transthoracic echocardiography are poor predictors of all-cause death in an elderly HF cohort, which may be explained by a high proportion of deaths from causes other than HF in an aging population., 14 CardThe major limitation of this study was the timing of the echocardiography. A significant proportion of patients were examined early after admission for new onset HF, before initiation of therapy. As therapy may lead to an improvement in hemodynamic status and significant increase in both LVEF and CI, assessment of these parameters early in the disease course may have had limited value as predictors of later events. Further It is well known that approximately 30–40% of patients with guideline-based indication for cardiac resynchronization therapy do not experience improvement in left ventricular function or in clinical symptoms., 17 ApprThe group of HF patients with an LVEF ≥40% has been the focus of research in recent decades. Results of all large mortality trials in this patient population have been neutral despite efforts to refine the diagnostic criteria for HF. Our analS1 File(XLSX)Click here for additional data file.


In this study, we tested whether an albumin-binding intravascular contrast agent (gadofosveset) allows for improved quantification of myocardial permeability compared to the conventional extracellular contrast agent Gd-DTPA using late gadolinium enhancement (LGE) and T1 mapping MI was induced in C57BL/6 mice (n = 6) and cardiac magnetic resonance imaging (CMR) was performed at 3, 10 and 21 days post-MI using Gd-DTPA and 24 h later using gadofosveset. Functional, LGE and T1 mapping protocols were performed 45 min post-injection of the contrast agent.1 measurements after administration of gadofosveset were higher in the acute phase-day 3 (R1 [s−1] = 6.29 ± 0.29) compared to the maturation phase-days 10 and 21 (R1 [s−1] = 4.76 ± 0.30 and 4.48 ± 0.14), suggesting that the uptake of this agent could be used to stage myocardial remodeling. No differences in myocardial R1 were observed after administration of Gd-DTPA at different time points post-MI . The MRI results were validated by ex vivo histology that showed albumin leakage in the myocardium in the acute phase and microvessel formation at later stages.LGE images showed that both contrast agents provided similar measurements of infarct area at all time points following MI. Importantly, the myocardial RWe demonstrate the merits of an albumin-binding contrast agent for monitoring changes in myocardial permeability between acute ischemia and chronic post-MI myocardial remodeling. •In-vivo measurements of LGE areas using gadofosveset after MI are comparable to the gold-standard, Gd-DTPA.•In-vivo imaging using gadofosveset shows higher signal intensity making delineation of the ischemic myocardium easier.•T1 mapping using gadofosveset allows monitoring changes in myocardial permeability.•T1 mapping using gadofosveset allows differentiation between acute and chronic phases post-MI, compared to Gd-DTPA. Post-MIThe extent of myocardial damage and its location within the left ventricle (LV) directly affects the magnitude of LV remodeling . The undAnimal models of MI are important in research to understand the complex pathophysiology of ischemic heart disease  and are ®, is a clinically approved gadolinium-based blood pool contrast agent that reversibly binds to serum albumin, resulting in a prolonged vascular presence and a 5–10-fold increase in relaxivity (r1) T1=T1For T1 mapping and LGE analysis, images were segmented at the end-diastolic phase due to the better contrast between the enhanced and remote areas compared to other time points during the cardiac cycle.Contrast-to-noise ratio (CNR) between infarcted and remote myocardium was calculated using the following equation:No dedicated noise scan was used. Noise was measured in air, outside of the mouse. No Rayleigh correction was applied.2.4At the end of the CMR scans, mice (n = 6) were culled by cervical dislocation and the hearts were harvested. An additional 3 hearts were used for histology at 3 and 10 days post-MI. Hearts were perfused with saline, harvested and immersed in 10% formalin for 48 h at 4 °C. Hearts were then embedded in paraffin and sectioned into 5 μm-thick transverse slices. Sections were stained with Masson's trichrome  to assess tissue morphology and visualize the infarct, CD31 immunohistochemistry to detect endothelial cells and microvessels, and albumin immunohistochemistry for intraventricular albumin detection.2O2 in methanol to block endogenous peroxidase. Sections were then immersed in 0.01 M citrate buffer, pH 6.0, and boiled for 3 min, washed and blocked for 1 h with 10% donkey serum and then incubated overnight with the primary antibody [rabbit anti-mouse CD31 ]. Sections were washed and incubated with anti-rabbit HRP Polymer [X-Cell Plus Universal Polymer HRP detection kit ] followed by peroxidase substrate to detect the signal . Sections were counterstained with nuclear fast red. For albumin immunohistochemistry, the same protocol was performed and samples were incubated overnight with the primary antibody [goat anti-mouse serum albumin ]. Sections were washed and incubated with secondary antibody [donkey anti-goat biotinylated antibody ] followed by streptavidin-peroxidase complex to amplify the signal , and diaminobenzidine/H2O2 solution to detect the signal . Sections were counterstained with hematoxylin. Negative control sections were incubated without the primary antibody.For CD31 immunohistochemistry, sections were immersed in 3% H2.5post hoc multiple comparison test. Bland-Altman method was used to test the agreement between the two contrast agents. P-values < 0.05 were used to define statistical significance.Results are expressed as mean ± SEM. Statistical differences were determined using GraphPad Prism 5.0 . Differences between time points and contrast agents were analyzed using 1 way ANOVA followed by a Dunns 33.1Cine-FLASH images were used to assess ejection fraction, left ventricular (LV) volumes and mass (n = 6). Representative diastolic and systolic short-axis images of control, 3, 10 and 21 days post-MI hearts showed a significant enlargement of the LV and myocardial wall thinning at the later stages of infarction A; arrows3.21) of both the ischemic myocardium and blood peaked at 30 min and was maintained for at least 90 min after administration of either Gd-DTPA or gadofosveset. However, gadofosveset showed increased R1 values compared to Gd-DTPA in the ischemic myocardium and blood (Pharmacokinetics of Gd-DTPA and gadofosveset (n = 6) were investigated at 3 days post-MI to determine the optimum imaging time point for MI imaging. The relaxation rate  in situ allows quantification of gadolinium uptake in the ischemic and remote myocardium. The analysis showed significantly higher R1 values in both the remote  after MI, which were primarily characterized by a significant increase in collagen deposition (blue) in the ischemic area by day 21 : r1 = 4.7 mmol−1s−1) at 1.5 T are currently used in the clinic  unbound gadofosveset leaks into the myocardium; [2] unbound gadofosveset leaks into the myocardium and binds to intra-myocardial albumin; and [3] bound gadofosveset leaks into the myocardium. Gadofosveset also has longer blood half life time due to its interaction with albumin allowing for a longer imaging window and enabling acquisitions during the steady-state. In the present study, we demonstrate that imaging with gadofosveset provides similar LGE areas as compared to Gd-DTPA but with higher signal intensity which facilitates scar visualization and delineation. At high field (7 T), the relaxivity of Gd-DTPA and gadofosveset are significantly lower compared with that at lower magnetic field strength  [In our study, all mice showed progressive LV dilation that was accompanied with a reduction in global contractile function (ejection fraction around 40%) after MI. In addition, stroke volume and mass were significantly increased at later time points suggesting alteration of the heart. These measurements are in good agreement with other studies that evaluated cardiac function in this animal model using different imaging modalities ,47. Diffe clinic . Althouge clinic . Experime clinic  and coroe clinic  atherosct 1.5 T) . The r1 solution . When gactively) ,55. At l1 values in the infarct after injection of gadofosveset. This is most likely due to the acute damage of the cardiac endothelium, which allows non-restricted leakage of macromolecules, such as albumin, from the blood into the ventricular wall, leading to a higher permeability that it is not associated with ventricular remodeling. This result is in good agreement with the ex vivo histological validation where highest and diffused albumin extravasation is present 3 days post-MI. At later time points (10 and 21 days post-MI), increased R1 values after gadofosveset administration where observed in areas of the LV wall with increased microvessel formation. In contrast, R1 values measured after Gd-DTPA administration did not change between 3 and 21 days, thus providing limited information about LV remodeling post-MI. Moreover, both Gd-DTPA and gadofosveset led to higher R1 values in infarcted tissue compared to remote myocardium, demonstrating that both contrast agents preferentially extravasate into injured tissues. Similarly to our results, Saed et al. demonstrated the presence and distribution of abnormal microvascular hyperpermeability in a rat model of ischemia-reperfusion using a different albumin-binding MR contrast agent 10-(Gd-DTPA)25) [After MI, the ischemic tissue undergoes severe changes in cellular and extracellular matrix composition leading to an increase in the extracellular volume ,57. AcutDTPA)25) .Gd-DTPA and gadofosveset have been also compared in other animal models and man. Using a canine model of ischemia reperfusion, Gd-DTPA showed better characteristics for myocardial scar visualization compared with Gd-BOPTA (MultiHance) and gadofosveset. However, a single imaging session 90min after reperfusion of the hearts was performed in these studies and a thus the temporal changes of contrast uptake within the remodeled myocardium was not investigated . In patiThe noninvasive assessment of cardiac permeability and neovascularization in the infarcted myocardium may be a useful tool to characterize ventricular remodeling after MI and may lead to a more accurate diagnosis and treatment guidance by differentiating the acute for the maturation phase of the myocardial remodeling process. This study demonstrates that gadofosveset has the potential to visualize and quantify microvascular changes associated with post infarction healing, allowing the differentiation between the acute and maturation phases post-MI. This approach could provide new valuable information for the stratification of patients in order to use a more targeted therapeutic intervention.4.1ex vivo methods. Our aim was to provide a proof of principle on the potential mechanism underlying the uptake of contrast agent into the myocardium but not to perform an extensive ex vivo quantification of the changes in albumin or neovessels density.One of the limitations of our study is the high dose of contrast agent used  due to low signal intensity obtained at the 7 T pre-clinical scanner and probably because of the use of intraperitoneal injection as opposed to the clinical standard intravenous injection, also resulting in a prolonged washout period. Therefore, additional studies are needed to investigate the optimal contrast agent dose administered at lower field strength (e.g. 3 T). In addition, to obtain better imaging quality of the ischemic myocardium, a wash out period of gadofosveset from blood is required, which would delay the imaging protocol. An additional limitation is the use of a permanent ligation animal model of MI. Additional studies using an ischemia-reperfusion model could potentially increase the clinical applicability of this study. In addition, because of the limited number of animals used in this study we did not have enough specimens to quantify the increase in albumin/CD31 staining by complimentary 4.2We demonstrate that both Gd-DTPA and gadofosveset provide comparable measurements of ischemic area. Additionally, the combination of LGE and T1 mapping after administration of gadofosveset allowed for the detection of changes in myocardial permeability differentiating acute and chronic phases following MI.The authors declared they do not have anything to disclose regarding conflict of interest with respect to this manuscript.British Heart Foundation Centre of Excellence at King's College London, (2) a British Heart Foundation Program grant (RG/12/1/29262), (3) the Wellcome EPSRC Centre for Medical Engineering at King's College London  and (4) the Department of Health through the National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre award to Guy's & St Thomas' NHS Foundation Trust in partnership with King's College London and King's College Hospital NHS Foundation Trust.This work was supported by the (1) Author contributions: B.L. and A.P. conception and design of research; B.L., A.P. and X.D. performed experiments; B.L., A.P. and S.L. analyzed data; B.L. A.P., S.L., A.Ph., R.B., and A.M.S. interpreted results of experiments; B.L. prepared figures; B.L. and A.P. drafted manuscript; B.L., A.P., A.Ph., R.B., and A.M.S. edited and revised manuscript; B.L., A.P., A.Ph., R.B., and A.M.S. approved final version of manuscript.


The role of atrial rate‐responsive (RR) pacing in cardiac resynchronization therapy (CRT) is unclear due to the favorable effect of rate lowering in systolic heart failure. Atrial high rate episodes (AHREs) in CRT recipients are particularly worrisome since they cause loss of CRT, beyond representing a stroke risk factor.The presence of an association between RR and the incidence of AHREs.Daily remote transmissions from 836 CRT recipients were analyzed. AHREs were classified by duration: ≥15 minutes, ≥5 hours, and ≥ 24 hours. Variables possibly associated to AHREs were included in time‐dependent proportional‐hazard models, averaging over 30‐day periods and adjusting for main baseline variables.P = .01), while CRT amount decreased it . The extent of atrial pacing did not predict AHRE occurrence.After a median follow‐up of 23.9 (12.2‐36.0) months, 507 (60.6%) patients experienced at least one 15‐minute AHRE. RR function was programmed in 166 (19.8%) patients and was associated with an increased AHRE occurrence rate with hazard ratio (HR) ranging from 1.45 to 1.78 for the 3 cutoffs of episode duration. The negative effect of RR function was not observed in the subset of patients with low mean heart rate (<68 bpm). Higher mean heart rates increased AHRE risk (HR:1.02, RR pacing in CRT recipients is associated with increased AHRE occurrence, especially when an average heart rate > 68 bpm is attained. Eventually, 836 patients provided data that could be processed. Device replacements were excluded to avoid the risk of possible arrhythmic episodes experienced with the previous device and not properly documented.All RM data were generated by the Home Monitoring system  a well‐known fully automatic RM technology, characterized by daily device to patient‐unit telemetry, and daily transmissions from patient‐unit to a central Service‐Center through the GSM network for mobile communications. For the purpose of our analysis, we firstly selected 1226 consecutive patients who received an implantable defibrillator with CRT function (CRT‐D) from 2008 to 2017. We further excluded 390 patients due to permanent atrial fibrillation (280), device replacements,2.3The primary endpoint of the analysis was time to first post‐implant date with atrial high rate episode (AHRE). The following AHRE burden cutoffs were considered: ≥15 minutes, ≥5 hours, and ≥ 24 hours. AHRE detection was based on the rate criterion with a detection limit of 200 bpm in most cases. In order to correctly evaluate the association between atrial pacing and AHRE incidence, atrial arrhythmic burden was not preferred as study endpoint, as periods of atrial fibrillation should necessary be excluded from the analysis. In fact, atrial fibrillation and atrial pacing are normally inversely related due to the obvious pacing inhibition during the arrhythmia.The main objective of the analysis was to evaluate whether RR function was associated to an increased or decreased incidence of AHRE. Patients were therefore divided into subgroups according to whether the RR function was programmed on or off. When programmed on, the RR function was provided by standard accelerometers nominally programmed. The analysis was repeated in subgroups of tertiles of baseline mean heart rate. To this end, we excluded the first 30 days post‐implant and calculated the average of daily‐sampled heart rate over the second month post‐implant.In order to investigate whether the association between RR function and AHRE incidence was mediated by other factors, the following variables were also evaluated: atrial pacing percentage (AP%), CRT percentage (CRT%), and 24‐hour average of heart rate (24 hours). As these data were longitudinal with daily sampling, the variables were included in time‐dependent proportional‐hazard models, averaging over 30‐day periods and adjusting for main baseline variables. These models were used to fit AHRE burden ≥15 minutes and 5 hours. Analysis for AHRE burden ≥24 hours was omitted as pacing percentages and heart rates could have been significantly biased by long‐lasting AHREs.2.4U‐test if the normality hypothesis could be rejected. Missing data were not replaced; all available data were used for sample distributions evaluation and proportions calculation. RR association with AHRE incidence was evaluated with univariate proportional‐hazard Cox model with the whole population and within each second‐month heart rate tertile, reporting the relative hazard ratio (HR) along with the 95% confidence interval (CI). Schoenefeld's residual method was used to test the proportional‐hazard assumption. Plots of AHRE‐free rates were generated as Kaplan‐Meier curves and the cumulative proportions of patients with AHREs during follow‐up and the CI were calculated with the product‐limit method. Multivariate time‐dependent proportional‐hazard Cox models were also used to separately fit AHRE incidence with AP%, CRT%, and 24 hours as longitudinal variables, taking averages every 30 days. Sex, age, and ischemic cardiomyopathy were used as adjusting baseline variables. All statistical tests were significant with P ≤ .05. All analyses were performed with Stata software version 11.1SE .We described the selected population by using RR programming at baseline as grouping criteria. Binary and categorical variables were reported as percentages of available data and compared between groups with the Pearson χ² or Fischer tests, as appropriate. Continuous variable distributions were reported as median (interquartile range) and checked for normality with the Shapiro‐Wilk test. Between‐group comparisons were performed with the Mann‐Whitney 33.1P < .0001). Excluding the first month post‐implant period for implant stabilization, the 30‐day average AP% at the second month was significantly higher in the RR on group , but no differences were detected in CRT% and 24 hours.Of the 836 CRT‐D patients included in the analysis, 166 (19.8%) had the RR function programmed on at baseline (Table 3.2After a median follow‐up of 23.9 (12.2‐36.0) months, 507 patients (60.6%) experienced at least one AHRE burden ≥15 minutes.P = .002). Figure P = .001) and ≥ 24 hours .The 3‐year cumulative proportion of patients with AHRE burden ≥15 minutes was 0.76  in the RR on group and 0.63  in the RR off group, with 1.45  HR of RR on vs off . The HRs and CIs are listed in Table 3.3P < .001) and increase in 24 hours HR (P ≤ .013) there was an approximate 2% increase in the risk of AHRE occurrence.The results of the multivariate Cox analysis including AP%, CRT%, and 24 hours HR as time‐dependent covariates are reported in Table 44.1In a relatively large population of HF patients implanted with remotely monitored CRT‐D devices as per routine practice, about 50% of devices were programmed with a lower rate of 60 bpm or higher and 20% with RR function on. We observed a 45% to 78% increased risk of both short and long‐lasting AHREs, associated to the activation of the RR function. The negative correlation for the RR function was not observed in the subset of patients with low mean heart rate (<68 bpm). At a multivariate time‐dependent analysis, suboptimal CRT delivery and high mean heart rate were factors significantly associated with AHRE onset. Conversely, we did not find any evidence that atrial pacing itself may affect AHRE incidence.4.2Several investigations performed in the past provided controversial results about RR function and atrial pacing above intrinsic rate as effective strategies for preventing atrial fibrillation in sinus node dysfunction.4.3Consistently with previous reports,Programming 60 to 70 bpm lower rates and activating the RR function in CRT‐D devices disrupts physiologic heart rate behavior when sinus node performance is still adequate, a significant association with AHRE onset being observed despite relatively small amounts of atrial pacing. RR feature should be reserved for those patients with marked resting bradycardia in the range of 40 bpm and no/little increase during exercise, thus showing reduced heart rate variability and exercise intolerance: in this setting, restoration of a normal rate fluctuation in daily activity may exert symptomatic improvement, and is devoid of unwanted effect on atrial arrhythmias, as our data pointed out Table .4.3.1The limitations of a registry rather than a randomized study apply to our analysis including the impossibility to test a formal hypothesis. As there are no established indications for the use RR function in sinus rhythm CRT patients, the decision of switching RR on or off was purely based on physicians' personal believes and perceptions. This is a typical trait of large retrospective observations, nevertheless, it represents the main strength stemming from patients' enrolment in real‐life clinical practice. Our study addressed patients in sinus rhythm that represent about 80% of CRT recipients at implantation. Patients in permanent AF or AF as “destination” rhythm are managed differently, and according to current practice they receive either atrio‐ventricular node ablation or strict pharmacologic rate control to ensure CRT delivery as close as possible to 100%. In this setting, RR is often used to achieve a target 100 to 110 bpm to ensure exercise tolerance. Finally, as the HMEA database is based on the Home Monitoring system, all results were obtained with a single manufacturer RR pacing algorithm potentially compromising in some way the extrapolation to other devices.5RR pacing in CRT recipients is associated with an increased burden of short‐ to long‐lasting AHREs when the average heart rate exceeds 68 bpm. The extent of atrial pacing per se does not seem to predict the occurrence of atrial arrhythmias, rather the average rate is the strongest AHRE predictor. In this population, a low heart rate seems to confer advantage also in the prevention of atrial arrhythmias, beyond the well‐known effect on HF outcome.D.G. and A. G. are employees of BIOTRONIK Italia. All other authors have reported that they have no conflicts relevant to the contents of this paper to disclose. This research did not receive any specific grant from funding agencies in the public, commercial, or not‐for‐profit sectors.APPENDIX S1 Supporting informationClick here for additional data file.


First Person is a series of interviews with the first authors of a selection of papers published in Disease Models & Mechanisms (DMM), helping early-career researchers promote themselves alongside their papers. Nicoleta Baxan is first author on ‘ Nicoleta BaxanHow would you explain the main findings of your paper to non-scientific family and friends?in vivo CMR parameter measurements with the underlying heart histopathology.Immune-mediated damage to the heart may occur as the result of a wide variety of underlying conditions, including infectious disease, exposure to toxins, chemotherapeutic agents, and systemic inflammation due to autoimmune disease. CMR mapping provides unique information of tissue damage in inflammatory disease by tracking subtle changes in myocardium, such as specific disease pathways related to intracellular disturbances of cardiomyocytes (iron deposition); extracellular disturbances in the myocardial interstitium (fibrosis from accumulation of collagen); or both . In this study, we identified a significant amount of interstitial iron in the hearts of Resiquimod-treated mice, which is most likely the result of hemorrhage, erythrocyte cell death and hemoglobin degradation. We show that chronic anti-heart autoimmunity in the Resiquimod model of systemic lupus erythematosus (SLE) follows acute thrombocytopenia and hemorrhagic myocarditis, and provide a thorough comparison of What are the potential implications of these results for your field of research?1, T2, T2* will allow insight into the natural history of disease and improve our understanding of the potentially subclinical course of cardiac involvement in systemic inflammation.Acute myocarditis may trigger an autoimmune reaction against the heart, and it is feasible that severity of hemorrhaging, acute tissue damage and subsequent autoimmunity are correlated. The ability to non-invasively discriminate different processes of tissue damage by using specific magnetic resonance imaging (MRI) metrics based on changes in myocardial parameters T“Studying genetically diverse mouse panels instead of a single inbred mouse line may reveal a range of susceptibilities.”What are the main advantages and drawbacks of the model system you have used as it relates to the disease you are investigating?CFN mice. Considering that myocardial hemorrhaging may be more common than currently appreciated in systemic inflammation of both infectious and autoimmune origin, as well as directly heart-targeted infections, these processes need to be characterized in the corresponding mouse models. Considering that only a small proportion of human patients develop clinically detected hemorrhagic myocarditis, there is likely to be a genetic component to disease susceptibility. Studying genetically diverse mouse panels instead of a single inbred mouse line may reveal a range of susceptibilities.Myocardial hemorrhage is not commonly reported in patients with myocarditis. Underlying mechanisms leading to hemorrhage in some myocarditis patients but not in others and implications on survival and subsequent development of inflammatory cardiomyopathies are far from understood. The specific phenotype of hemorrhagic myocarditis has only been studied in Resiquimod-induced systemic inflammation in In acute stage, the mouse model used in this study closely mimics physiological responses to a viral infection due to the stimulation of the TLR-7 pathway. TLR-7 is a pattern-recognition receptor involved in recognition of single-stranded RNA of viral origin, and is thus crucial in host defense against viral infections. Artificial over-activation of this virus defense system may cause the same phenomena as seen in severe complications of viral infection .What has surprised you the most while conducting your research?I am constantly amazed by the power of multidisciplinary research, and this project is a true example of it. I am an MR physicist by training, and the collaborative nature of this project gave me the opportunity to work with amazing and highly skilled researchers coming from different disciplines . Bringing together multiple disciplines brought this paper to light (and most of my research so far), and this almost certainly wouldn't have been done by focusing on a single area.“I am constantly amazed by the power of multidisciplinary research, and this project is a true example of it.”Describe what you think is the most significant challenge impacting your research at this time and how will this be addressed over the next 10 years?The technical challenges of acquiring CMR data synchronized with the cardiac motion combined with the relatively poor pathological specificity of CMR may affect the scan time, the analysis and interpretation of data. New emerging techniques based on artificial intelligence and machine learning approaches are bringing exciting possibilities of faster data acquisition and automated AI-driven quantitative analysis, eliminating many tedious, manual tasks. This will provide enormous opportunities to homogenize data acquisition and computation to better characterize disease by imaging.“I believe that giving full confidence, responsibility and credit to early-career scientists to conduct their research independently is crucial for their future career.”What changes do you think could improve the professional lives of early-career scientists?I am very lucky to have a very supportive PI, giving me the chance to be autonomous in my work and in my projects. I am constantly learning and improving my skills of setting new collaborative projects, presenting my findings and networking. I believe that giving full confidence, responsibility and credit to early-career scientists to conduct their research independently is crucial for their future career.


In the last years, the number of clinical indications for the evaluation of the heart – with both computed tomography (CT) and magnetic resonance (MR) – exponentially grew. This evidence reflects the remarkable technological developments of both techniques allowing unprecedented spatial, temporal and contrast resolution levels and to comprehensively evaluate cardiac pathology, combining anatomical information with functional assessment and tissue characterization of myocardial diseases.In the field of non-invasive coronary artery imaging, CT has a prominent role, thanks to its superior spatial resolution (up to 0.3 mm with recently released scanners) and improved temporal resolution (up to 87 msec), and it is overall accepted better by the patient.Theoretically, MR represents an ideal tool for coronary imaging, due to the lack of ionizing radiation or contrast agents, lack of beam-hardening artefacts related to the presence of calcifications and to its superb contrast-to-noise ratio and high temporal resolution (up to 50 msec) making coronary-related motion artefacts less likely to occur. As confirmed in a large number of metanalyses, however, this method is currently non-competitive with CT for the evaluation of coronary artery disease due to its overall high technical complexity with long scanning times (still consistently higher than five minutes) and due to the low spatial resolution (0-8-1 mm maximum), limiting reliable quantification of stenosis degree only to large-caliber proximal epicardial vessels.As a matter of fact, cardiac MR is frequently required for the evaluation of origin and course of coronary arteries and to characterize benign vs malignant anomalies. In pediatric patients, Cardiac Magnetic Resonance (CMR) is also utilized in the follow-up of vasculitis (like Kawasaki disease) in which repeated follow-up scans are often required (with possible radiation overexposure) to monitor progression of giant coronary aneurisms.Temporal resolution is the real gatekeeper for optimal cardiac functional and valvular imaging. Morphological assessment of valvular apparatus including evaluation of small vegetations or moving structures is also frequently required in combination with functional imaging and limited by spatial resolution constraints mostly for MR imaging.As a consequence, cardiac MR is the current gold standard for both regional and global functional assessment including (bi-)ventricular volumes and ejection fraction and myocardial mass.Although feasible and accurate, the role of CT in this application is limited by some important technical drawbacks, including the intrinsic increase of radiation dose related to the application of a retrospectively Electrocardiography (ECG)-gated scanning technique and to the relatively low frame-rate  leading to the risk of over-estimating ventricular volumes (particularly End Systolic Volume ESV).For the same reason, regional wall motion is also well assessed with MR, which also exploits the availability of a variety of techniques  allowing qualitative and semi-quantitative assessment of different components of intrinsic cardiac motion.In valvular disease, combined morphological and functional assessment is also mandatory and both techniques are used in a variety of clinical setting in patients with valvular heart disease including pre-surgical evaluation (with TAVR) and assessment of prosthetic valves. CMR offers the added value of trans-valvular flow quantification which is particularly useful in right heart pathology and complex congenital heart diseases.The authors declare that they have no competing interests.


ECG-gated 18F-FDG PET imaging was performed in a rat model of type 2 diabetes (ZDF fa/fa) and ZL control rats at age of 13 weeks . Under hyperinsulinemic-euglycemic clamp to enhance cardiac activity, 18F-FDG was administered and subsequently, list-mode imaging using a dedicated small animal PET system with ECG signal recording was performed. List-mode data were sorted and reconstructed into tomographic images of 16 frames per cardiac cycle. Left ventricular functional parameters (systolic: LV ejection fraction (EF), heart rate (HR) vs. diastolic: peak filling rate (PFR)) were obtained using an automatic ventricular edge detection software. No significant difference in systolic function could be obtained . On the contrary, ECG-gated PET imaging showed a mild but significant decrease of PFR in the diabetic rats . Investigating a diabetic rat model, ECG-gated 18F-FDG PET imaging detected LV diastolic dysfunction while systolic function was still preserved. This might open avenues for an early detection of HF onset in high-risk type 2 diabetes before cardiac symptoms become apparent.In diabetic cardiomyopathy, left ventricular (LV) diastolic dysfunction is one of the earliest signs of cardiac involvement prior to the definitive development of heart failure (HF). We aimed to explore the LV diastolic function using electrocardiography (ECG)-gated  However, epidemiologists forecast that its prevalence will rise up to 33% in the year 20502 and therefore, an extensive disease burden can be anticipated in both the United States and Europe3. The Framingham Study has intensively reported on an increased risk of heart failure (HF) development prior to clinical manifestation of DM4 and consequently, novel non-invasive diagnostic strategies to reveal an early onset of HF in diabetic cardiomyopathy (CM) are intensively sought.As one of the most devastating diseases, diabetes mellitus (DM) type 2 is also called “The Epidemic of the Century”5. As a clinical impetus, diastolic dysfunction has attracted interest, mainly due to its presence in asymptomatic DM patients and as an early sign of a chronic heart disease, such as diabetic CM7. The latter one is defined as structural and functional heart abnormality in DM patients that is not directly attributable to another underlying pathological cause 8. Of note, impaired diastolic function is a common phenomenon in asymptomatic patients suffering from diabetes and therefore, it should be assessed systematically among those high-risk patients9.Diastolic HF is defined as an increased filling pressure that is needed to achieve ventricle filling to a normal end-diastolic volume, while left ventricular (LV) systolic function is not hampered10. Apart from that, electrocardiography (ECG)-gated 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) has been established for the assessment of glucose utilization of the heart, as well as LV volumes and LV ejection fraction (LVEF) in clinical PET studies13. However, its potential for the assessment of ventricular performance in a dedicated diabetic CM small animal model has not been investigated yet.In recent years, a large variety of animal models have been investigated to study diabetic CM and its underlying pathology, in particular by using echocardiography or magnetic resonance imaging (MRI) for the evaluation of both LV systolic and diastolic function18F-FDG PET in the detection of LV diastolic dysfunction in a rat-model of type 2 diabetes.Therefore, we aimed to elucidate the capability of ECG-gated 14. Zucker lean (ZL) controls rats and Zucker diabetic fatty (ZDF fa/fa) rats  were investigated at an age of 13 weeks .Animal protocols were approved by the local Animal Care and Use Committee  and conducted according to the Guide for the Care and Use of Laboratory Animals15. 18F-FDG was synthesized in-house according to the manufacturer’s instructions. All animals were maintained under anesthesia throughout the imaging procedure. To enhance cardiac activity, approximately 37 MBq 18F-FDG were administered via the tail vein under hyperinsulemic-euglycemic clamp16. A 35-min list-mode PET acquisition with ECG recording was started shortly before tracer injection. The data were sorted into 3-dimensional sonograms of 16 frames per cardiac cycle, which were then rebinned with a Fourier algorithm to reconstruct dynamic images using a 2-dimensional ordered-subset expectation maximization method. All reconstructed images were corrected for 18F decay, random coincidences, and dead time. A 13 min transmission scan was also conducted prior to the emission scan for attenuation correction17.Fasting was performed >10 h . A high resolution dedicated small animal PET system  was used for data acquisition. Its specifications have been described previously19. Heart Rate (HR) was also compared.For LV functional and volume analysis, image data from 15 to 35 min after tracer injection were employed. Evaluation of LV function and volume was performed using a dedicated automatic ventricular edge detection software , which had been adapted to the size of a rat heart (5 fold magnification of the voxel size of the reconstructed images). The following parameters were assessed using a programme feature for 16-gated myocardial perfusion single photon emission computed tomography: As volume parameters, end-diastolic and end-systolic volumes . As a systolic parameter, ejection fraction . As diastolic parameters, the peak filling rate , the one-third mean filling rate  and the time to PFR  were investigated .All results are displayed as mean ± standard deviation. The two-tailed paired Student’s t-test was used to compare differences between two dependent groups, and the two-tailed independent Student’s t-test for differences between independent groups. The use of the latter test has been recommended, in particular for smaller sample sizesECG-gated PET in the ZDF rat model indicated a reduced diastolic function, while the systolic function was still preserved: No significant difference in the systolic assessment could be obtained . In addition, cardiac MRI cannot be routinely performed in patients with limiting preconditions, such as subjects with implantable devices or rhythm disorders23. As a fast, accurate and easily available method, TTE is extensively performed to assess this phenomenon among high-risk individuals, but it may be limited by its acoustic window23. In addition, paroxysmal or permanent atrial fibrillation may also limit its interpretation24. Thus, novel non-invasive imaging modalities may overcome those hurdles and 18F-FDG PET may serve as an attractive alternative, e.g. by investigating subclinical diastolic dysfunction with preserved EF in patients with implantable devices.To assess the clinical condition of diastolic HF, left-sided heart catherization may give ultimate evidence, but its invasive nature may limit its widespread adoptionMarsh et al. demonstrated that Zucker diabetic fatty obese rats suffered from impaired LV relaxation 25. In a previous investigation also relying on echocardiographic images, a dilated ventricle with reduced subnormal contraction was proven in a head-to-head comparison between ZDF fa/fa rats and ZL controls26. In addition, 18F-FDG PET studies for the assessment of LV function have also been performed previously in healthy animals: Investigating MRI as a reference standard in healthy mice, an LV function obtained by 18F-FDG PET demonstrated an excellent correlation compared to MRI27. Similar results could be obtained for healthy rats: in a comparison of 18F-FDG PET with a clinical MRI system, LVEF values were almost identical to the herein obtained LVEF values of ZL control rats28. In an elegant approach, Todica et al. recently reported on the use of the novel blood-pool tracer 68Ga-albumin in healthy Sprague-Dawley rats: notably, compared to the gold standard MRI, an even better correlation between LVEF values could be obtained for 68Ga-albumin than for 18F-FDG29. Moreover, Aikawa and coworkers recently investigated 11C-hydroxyephedrine (11C-HED) in HF patients with preserved ejection fraction: altered myocardial sympathetic innervation was associated with the presence of advanced diastolic dysfunction30. Hence, other promising cardiac PET imaging agents could potentially be applied in the herein described diabetes rat model and might pave the way for further insights into diabetic CM prior to the onset of cardiac involvement in the long run.Previous studies have reported on the use of imaging tests in dedicated diabetes small-animal models: Assessing cardiac function via echocardiography, Welch et al. studied ZDF rats at week 12, which is considered to be consistent with the metabolic alterations occurring at an early stage of type 2 DM in human subjects32. To further strengthen our preliminary findings, we also investigated 18F-FDG under hyperinsulinemic-euglycemic clamp conditions: This strategy is known to provide an excellent image quality and is superior to other conventional techniques to enhance cardiac activity, such as glucose load and/or insulin bolus prior to image acquisition35.Apart from that, the age of the investigated ZDF rats is of utmost importance: analogous to our study, db/db mice and ob/ob mice36. Nonetheless, given a potential partial volume effect on PET, the larger size of a rat heart may be more suitable in the present study design37. In addition, such examinations in ZDF/ZL rats could also be conducted in recently introduced imaging modalities, such as (PET/)MRI or with the more commonly used TTE38. In particular, the latter imaging technique could also serve as a gold standard, in a manner similar to left-sided heart catherization23.This study has several limitations: First, it is discussed controversially which animal model may fulfil all disease conditions present in a human setting and patients suffering from DM. Thus, other animal models could also be investigated, e.g. 18F-FDG PET demonstrated distinguished characteristics to assess impaired diastolic function, while systolic function was not significantly altered. Hence, reflecting a typical pathological condition which occurs early in diabetic CM prior to symptomatic manifestation of cardiac involvement, this novel PET-based strategy might set the scene for identifying high-risk patients before cardiac symptoms become clinically apparent. In light of the results of the present study, future efforts may focus on investigating this phenomenon in a clinical setting, e.g. by performing PET studies in DM patients at an early stage of disease. This could be done not only with the”working horse” in PET imaging, namely 18F-FDG, but also with other, recently emerging cardiac radiotracers, such as the blood-pool tracer 68Ga-albumin, or with imaging probes evaluating cardiac innervation (11C-HED or 18F-LMI1195)40. Such an approach of a global assessment of different cardiac conditions may pave the way to obtain further insights in the underlying pathology of diastolic dysfunction in DM patients.In a diabetic CM rat model under insulin clamp, ECG-gated


Identification of in vivo passive biomechanical properties of healthy human myocardium from regular clinical data is essential for subject-specific modelling of left ventricle (LV). In this work, myocardium was defined by Holzapfel-Ogden constitutive law. Therefore, the objectives of the study were (a) to estimate the ranges of the constitutive parameters for healthy human myocardium using non-invasive routine clinical data, and (b) to investigate the effect of geometry, LV end-diastolic pressure (EDP) and fibre orientations on estimated values. In order to avoid invasive measurements and additional scans, LV cavity volume, measured from routine MRI, and empirical pressure-normalised-volume relation (Klotz-curve) were used as clinical data. Finite element modelling, response surface method and genetic algorithm were used to inversely estimate the constitutive parameters. Due to the ill-posed nature of the inverse optimisation problem, the myocardial properties was extracted by identifying the ranges of the parameters, instead of finding unique values. Additional sensitivity studies were carried out to identify the effect of LV EDP, fibre orientation and geometry on estimated parameters. Although uniqueness of the solution cannot be achieved, the normal ranges of the parameters produced similar mechanical responses within the physiological ranges. These information could be used in future computational studies for designing heart failure treatments. Local myocardial wall stress is hypothesised to be responsible for many cardiac mechanisms, including ventricular remodelling, which is frequently associated with heart failure (HF). However, stress in the left ventricle (LV) cannot be measured directly . Finite Traditionally, ex vivo mechanical testing was carried out on myocardial tissue, harvested from a specific heart, to identify its properties. Results from the biaxial tests of canine myocardium , 31, 63 FE modelling, in combination with cardiac magnetic resonance imaging (CMRI), was carried out to estimate passive myocardial properties in a non-invasive manner , 60–62. An inverse estimation method, which is typically formulated as a non-linear optimisation problem to minimise the differences in the measurements with respect to the unknown parameters, was used to quantify passive properties of human myocardium using Holzapfel-Ogden material law. Due to the highly non-linear nature of the inverse optimisation problem, large design space and correlation amongst the material parameters, it is non-trivial to inversely estimate those parameters accurately and uniquely using limited clinical data. The trade-off is that while fewer clinical data make the inverse problem more ill-posed, requirement of more subject-specific data (i.e. MRI tagging and in-vivo ventricular pressure) leads to more complex and invasive clinical measurements with longer processing times, which is not always possible. Therefore, one of the major challenges, addressed in this study, was to extract the human myocardial properties instead of finding unique solution using non-invasive routinely used clinical data rather than using invasive and computationally expensive clinical data. Therefore, the study proposed a method to achieve the following objectives: (a) to estimate the normal ranges of Holzapfel-Ogden parameters for healthy human myocardium using routinely used non-invasive clinical data, and (b) to explore the effect of geometry, fibre orientation and EDP on the estimation of passive parameters.a, b, af, bf, as, bs, afs, bfs)in the strain energy function along with an extra bulk modulus (K) as shown in Eq.  and  a represent the dimension of stress in kPa and the unit-less parameter bi  and  b represent the non-linear behaviour of the corresponding structure. The bulk modulus (K) works as a penalty parameter for imposing incompressibility.In the present study, ECG gated, breath hold, steady-state free precession (SSFP) cine CMRI was used to capture the images of five normal human ventricles at UHCW, UK. BSREC ethics approval REGO-2012-032) and patients’ consent were obtained to carry out the research on anonymised human data. Mimics and 3-matic  were used to construct the bi-ventricular (BV) mesh geometry form CMRI as detailed in Palit, Turley    . The eaAs outlined by Xi, Lamata  in the ca, b, af, bf, as, bs, afs, bfs > 0). On the other hand, it was reported that the human myocardium is less stiff than pig myocardium [From the definition of the material law, all the eight parameters are positive real number  [γ = amount of shear. From Eq. (a and b. The last six parameters are only responsible for maintaining the ordering as is evident from Eq. (ai (and bi) are kept same (i.e. if af : as : afs = constant and bf : bs : bfs = constant). Therefore, all the ai and bi  should be divided by Ka and Kb, respectively, so that Eqs.  . The ana, s, n}) .3\documehat Eqs.  are maina, b, Ka, Kb) were required for inverse estimation to maintain the observed shear stiffness ordering [Thus, only four independent parameters ..af and ba, b, Ka, Kb) so that the passive inflation of LV could produce ‘real’ LV EDV at EDP where real referred to MRI measured volume. Therefore, the objective function was to minimise the differences between the FE predicted and real LV cavity volume (Eq. (Sn) was measured.V0 and V20 are LV volume at 0 and 20 mmHg, respectively, V is the volume at a certain LV EDP. The empirical Klotz-curve (PVRn) was then derived by varying EDVn from 0 to 1 in Eq.  was calculated using Eq. . There ume  was, thsing Eq. ) was assSubject to,VRnR−ErDVR)/EDVR,Real (MRI measured) normalised volume = 100* (EDVVSn*(EDVS−ErDVR)/EDVSSimulated (FE generated) normalised volume = 100EDVRReal end diastolic volume measured from CMRI,ErDVR Real early diastolic volume measured from CMRI,EDVS End diastolic volume generated from simulation,PVRnEmpirical Klotz curve in 20 mmHg pressure scale (Eq. ),PVSnPressure normalised volume curve generated from FE resultsdvInfinitesimally small volumeabsAbsolute valueSn to Klotz curve (PVRn), i.e. Eq. . Ea. Ea20). i.e. Eq. ) were mei.e. Eq.  and (16)a, b, Ka, Kb) for five human BVs using the proposed inverse optimisation procedure  were then derived using Eqs. (11) and  and . The valfs) were plotted  and (fn) plane compared to the shear in (sf) and (sn) plane.Shear stresses for four shear modes  were plotted ( and σfn) and (fn) shear modes. However, the variation was higher for (sf) and (sn) shear modes although the predicted stress values were in the range from 0.4 to 0.8 kPa only.Shear stresses for four shear modes  with the results from Gao, Li . The parsurement  whereas surement  in ex via, b, af, bf) using transversely isotropic part of Holzapfel-Ogden model for human LV with heart failure. Genet, Lee [Another study was carried out by comparing the stress–strain relation of a cubic myocardial tissue under uniaxial stretch test using the estimated parameters in this study with those from other studies, which inversely estimated human myocardial parameters. Xi, Lamata  estimatenet, Lee  reportednet, Lee  were alsIt was observed that true fibre strain in LV wall is more for human data, because it is less stiff than pig myocardium, and therefore, inflated more at diastole Fig. . HoweverThe biomechanical properties of myocardium, derived from ex vivo cadaver heart, might be different from in vivo properties due to tissue homeostasis. Therefore, estimation of in vivo passive orthotropic biomechanical properties of LV myocardium could provide improved insight of the physiology of the heart functionalities. This study introduced a novel method consisting of FE modelling, response surface method (RSM) and genetic algorithm (GA) to non-invasively estimate the Holzapfel-Ogden constitutive parameters using routinely used clinical data rather than using invasive and computationally expensive clinical data. However, the method is also capable of adding new subject-specific data  as a constraint to produce unique solutions. In addition, effects of end diastolic pressure, fibre structure and geometrical heterogeneity on estimated values of the parameters were also examined, and it was observed that the greater variation in material parameters occurred due to the change in EDP rather than the variation of ventricular geometries and fibre orientations. These estimated parameters of healthy human myocardium can be used directly in future studies.The objective of the study was to estimate the subject-specific passive orthotropic properties of human myocardium using inverse optimisation method. This is a major challenge in the field of cardiac biomechanics  due to ta, b, Ka, Kb) instead of eight. The decision was based (i.e. reduction in number of independent parameters) on the shear test results of myocardium [σfs)( > σfn)( > σsf)( > σsn)( > σnf), σ(ns) , 18. ComIf4 and Is4 terms have major contributions in stress prediction. The estimated parameters that influence these terms (If4 and Is4) in the Holzapfel-Ogden constitutive law were relatively close for all the cases, and therefore, these parameter sets yielded similar mechanical responses.Subject-specific LV EDP and fibre-orientations were not available due to invasive measurement and technical limitations , 52, 56.Validation of the inversely estimated parameters for each human ventricle is not feasible as it is very challenging to perform mechanical tests on in vivo human hearts. Therefore, stress–strain relations of a cubic myocardium under simple shear and uniaxial stretch were compared with previous studies , 60, 62.SSFP cine CMRI was used to construct subject-specific bi-ventricular geometry, and subsequently, the FE modelling of LV. Although MRI tagging is able to provide in vivo strain measurement, this requires additional scanning time, and subsequently, needs to perform complex image processing to calculate strain values. Besides, MRI tagging is not a routine clinical procedure whereas cine CMRI is performed routinely and readily available. LV strain can be measured from 2D cine CMRI as described by Gao, Li . HoweverOne limitation of the study was the assumption of an initial stress-free state, which was present in all previous simulations of the heart based on in vivo images , 57, 59.In this study, subject-specific in vivo passive material properties of human myocardium were estimated using inverse optimisation procedure. MRI measured EDV and empirical Klotz relation were used to scale the material parameters of the Holzapfel-Ogden model for five healthy human ventricles. Anatomically realistic subject-specific models of five human bi-ventricles (BVs), constructed from CMRI, that employed rule-based fibre-sheet orientation and a structure-based orthotropic constitutive law (Holzapfel-Ogden model) were used to simulate the passive diastolic mechanics. This study introduced a novel method consisting of FE modelling, response surface method (RSM) and genetic algorithm (GA) to non-invasively estimate the Holzapfel-Ogden constitutive parameters using routinely used clinical data rather than using invasive and computationally expensive clinical data. Due to the limited clinical data, two different sensitivity studies were accomplished to identify the changes in parameters with the change in EDP and fibre orientations. Comparison of simple shear and uniaxial stress–strain relations with other studies, which inversely estimated human myocardial parameters based on different constitutive laws and EDP, showed that the estimated material parameters in this study generated similar stress–strain predictions. The study provided a wide range of parameter values due to the change in geometry, EDP and fibre orientations. These information could be useful for future computational study to identify the normal ranges of myocardial wall stress and strain during cardiac cycle.