Venoarterial extracorporeal membrane oxygenation is widely used as mechanical circulatory support for severe heart failure. A major concern with this treatment modality is left ventricular distension due to inability to overcome the afterload created by the extracorporeal membrane oxygenation circuit. The present porcine study evaluates coronary circulation, myocardial perfusion and ventricular distension during venoarterial extracorporeal membrane oxygenation.Ten anesthetized open-chest pigs were cannulated and put on cardiopulmonary bypass. Heart failure was achieved by 90 minutes of aortic cross-clamping with insufficient cardioplegic protection. After declamping, the animals were supported by venoarterial extracorporeal membrane oxygenation for 3 hours. Continuous haemodynamic measurements were performed at baseline, during cardiopulmonary bypass/aortic cross-clamping and during venoarterial extracorporeal membrane oxygenation. Fluorescent microsphere injections at baseline and after 1, 2 and 3 hours on venoarterial extracorporeal membrane oxygenation evaluated myocardial perfusion. Left ventricular function and distension were assessed by epicardial echocardiography.The myocardial injury caused by 90 minutes of ischaemia resulted in a poorly contracting myocardium, necessitating venoarterial extracorporeal membrane oxygenation in all animals. The circulatory support maintained the mean arterial blood pressure within a satisfactory range. A hyperaemic left anterior descending coronary artery flow while on extracorporeal membrane oxygenation was observed compared to baseline. Myocardial tissue perfusion measured by microspheres was low, especially in the subendocardium. Echocardiography revealed myocardial tissue oedema, a virtually empty left ventricle, and a left ventricular output that remained negligible throughout the extracorporeal membrane oxygenation run.Coronary artery blood flow is maintained during venoarterial extracorporeal membrane oxygenation after cardiopulmonary bypass and cardioplegic arrest despite severely affected performance of the left ventricle. Myocardial perfusion decreases, however, presumably due to rapid development of myocardial tissue oedema. Echocardiographic evaluation would reveal left ventricular distension, indicating high intraventricular pressures and compromised myocardial perfusion.7 The aim of the present study is to evaluate an animal model for critical post-cardiotomy failure and VA-ECMO-supported circulation, focusing on the relationship between left ventricular distension, coronary circulation and myocardial perfusion early after aortic declamping.A major concern with VA-ECMO as circulatory support is left ventricular distension due to the inability of the failing heart to generate sufficient ejection pressure and empty into the ascending aorta against the afterload (i.e. the aortic pressure) generated by the ECMO unit. Failure to decompress the left ventricle (LV) might delay myocardial restitution.8The experimental protocol was ethically evaluated and approved by the Norwegian State Commission for Laboratory Animals (Project: 201710294), and performed in accordance with the European Communities Council Directive of 2010 (63/EU). Ten young pigs (NOROC) of either gender, weighing 46 ± 5 kg (standard deviation (SD)) were used. The animals were premedicated with 20-mg/kg i.m. ketamine, 10-mg diazepam and 1-mg atropine, and ventilated on mask with oxygen with 3% isoflurane  for a short time to establish intravenous (IV) access through two ear veins. After inducing anaesthesia with loading doses of fentanyl (0.02 mg/kg), midazolam (0.3 mg/kg), pancuronium (0.063 mg/kg) and pentobarbital (15 mg/kg), the animals were tracheotomised, intubated and ventilated  with nitrous oxide (57-58%) and oxygen. Continuous IV infusions of fentanyl (0.02 mg/kg/h), midazolam (0.3 mg/kg/h), pancuronium (0.2 mg/kg/h) and pentobarbital (4 mg/kg/h) maintained anaesthesia. The pentobarbital infusion constituted the basic fluid substitution, 15 mL/kg/h of Ringer’s acetate. This anaesthetic protocol has previously been thoroughly evaluated, justifying safe use of neuromuscular blocking agents in young pigs.A urinary catheter was introduced through an open suprapubic cystotomy. Rectal temperature was monitored, and a pulse oximeter was applied to the tail. The iliac vessels were accessed through inguinal incisions, and the right carotid artery through the tracheostomy incision. A 6-Fr radial introducer  was introduced in the right carotid artery, another in the right external iliac artery and a third one in the left external iliac vein. Heparin 125 IU/kg was administered IV to prevent catheters clotting. A microtip pressure catheter  was inserted into the proximal aorta through the right carotid artery.® and TruWave®, Edwards Life Sciences Inc.). A second microtip pressure catheter  was inserted into the LV from the apex of the heart. An infant feeding tube was inserted into the left atrium via the auricle for injection of microspheres. Blood flow rate in the proximal left anterior descending coronary artery (LAD) was measured with a transit-time flowmeter . Haemodynamic variables were continuously recorded, digitized and later analysed .A median sternotomy and pericardiotomy were performed. A continuous cardiac output catheter  was introduced through the left internal mammary vein and floated into the pulmonary artery, monitoring CCO, central venous pressure (CVP) and pulmonary artery pressure (PAP) . The heparin-coated ECMO circuit  was primed with Ringer’s acetate. The centrifugal pump was driven by a Maquet Rotaflow ECMO unit (Maquet Cardiopulmonary GmbH). A repeated dose of Heparin 125 IU/kg was given after 45 minutes of aortic cross-clamping.2 on the respirator) and during brief periods of respiratory shut-off, echocardiographic recordings in end-expirium were obtained. In the four chamber long-axis view, the left ventricular end-diastolic and end-systolic septal to free wall and apex to basis diameters were measured with echocardiography . The corresponding anterior–posterior and the septal to free wall diameters were measured from the short-axis view, together with the anterior wall thickness. End-diastole was defined as the first deflection of the QRS-complex in the electrocardiogram (ECG), start and end of ejection were defined as the opening and closure of the aortic valve by pulsed wave Doppler (PWD). Recordings were analysed with a commercial software .After instrumentation baseline variables were registered, including haemodynamic variables, arterial blood gases  and the first injection of 15-μm fluorescent microspheres . After pre-oxygenation  with a pump flow set to 90 mL/kg/min. The aorta was cross-clamped. Lukewarm crystalloid cardioplegia  was infused in the aortic root and immediately discontinued once ECG was isoelectric. Ventilation was reduced to half of the original setting during this period of CPB. The aortic cross-clamp was maintained for 90 minutes, and then released for the heart to be reperfused. Any ventricular fibrillation was immediately electroconverted. Once a spontaneous cardiac rhythm was regained, within minutes after declamping, flow on the ECMO unit was decreased to 72 mL/kg/min, balancing between suck-down and fluid overload. Whenever heart rate exceeded 200 beats/min, synchronized electroconversion was performed, and if the heart rate was below 100 beats/min, a pacemaker set at 100 in ‘on-demand’ mode was allowed to pace the heart by use of epicardial electrodes on the right ventricle. After aortic declamping, an additional infusion of Ringer’s acetate was commenced with 10 mL/kg/h. At any sign of imminent suck-down, bolus doses of 60-mL Ringer’s acetate were given until the problem ceased. Arterial blood gases, microsphere injections into the ECMO arterial line and echocardiographic recordings were repeated at 60, 120 and 180 minutes on ECMO-supported circulation.9 Separate tissue samples were weighed, dried at 60°C for 3 weeks, reweighed and water content calculated as fraction of wet weight.After euthanasia (intracardiac potassium chloride), tissue samples were obtained from the endo-, mid- and epicardium of the anterior, posterior and the septal wall of the LV, from the right ventricle and from both kidneys. The samples along with reference blood samples were weighted and hydrolysed, with subsequent isolation of microspheres by filtration, dissolving of the fluorescent colours and quantification with fluorospectrophotometry .Data were analysed using SPSS v. 23 . Baseline values are given as mean ± SEM (standard error of the mean) or median  for variables with normal or skewed distribution. Haemodynamic variables were evaluated by one-way analysis of variance for repeated measurements (RM-ANOVA) or by Friedman Repeated Measures Analysis of Variance on Ranks whenever appropriate. If significant, time trend analysis using linear regression analysis with replication and testing for linearity was performed. Left ventricular tissue blood flow rates during ECMO-assisted circulation was evaluated by two-way analysis of variance (ANOVA) with time and wall layer within the same heart as repeated/related factors. If the interaction between time and layer were significant (p < 0.10), new ANOVAs for simple main effects were performed followed by Holm–Sidak multiple contrast tests when appropriate. Except for the interaction effect, a p-value <0.05 was regarded as significant.Supplemental Table A).The haemodynamic variables at baseline are presented in Supplemental Table A).An average of 266 mL (range: 95-522 mL) of antegrade tepid crystalloid cardioplegia was used to obtain isoelectric ECG. During aortic cross-clamping, mean aortic blood pressure was slightly lower than at baseline, but stable . Both CVmax gradually increased over time whereas LV-dP/dtmin became more negative , left ventricular end-diastolic pressure (LVEDP) decreased from 21.0 ± 2.3 to 12.2 ± 1.5 mmHg (p < 0.001).After removal of aortic cross-clamp, electroconversion of ventricular fibrillation and ECMO-supported circulation was necessary in all animals. Heart rate and LV-dP/dtnegative , mean PAnegative . The sysA hyperaemic response in the proximal LAD flow was observed following aortic declamping. After 15 minutes of reperfusion, LAD blood flow rate was on average increased by approximately 50% compared to baseline. LAD flow rate decreased over time levelling off at baseline levels at 120 minutes on ECMO-supported circulation . ThroughMyocardial tissue perfusion measured with microspheres was low in the subendocardium already after 60 minutes on ECMO-supported circulation. In the mid-and subepicardium of the LV and in the right ventricular myocardium tissue, perfusion was also reduced with time .In the short-axis view, LV antero-posterior and septum to free-wall end-diastolic dimensions were reduced and unaltered during ECMO perfusion. In the long-axis view, end-diastolic septum to free-wall dimension decreased whereas the apex to basis dimension was unchanged . The LV This experimental pig model can be used to study coronary blood flow and myocardial perfusion in a non-working heart during post-cardiotomy VA-ECMO-supported circulation. After declamping, 10 consecutive pigs with CPB and 90 minutes of aortic clamping with suboptimal cardioplegic arrest regained spontaneous cardiac rhythm after defibrillation. In pilot experiments with both 40 and 60 minutes of cross-clamp time, cardiac function was partially restored in the acute phase, and the indication for immediate ECMO-supported circulation was less clear. This experimental model thus represents an acute situation where a patient cannot be weaned from CPB after surgery.10 Echocardiography can be used to exclude or confirm distension of the LV, and to verify whether the aortic valve opens or not; a finding usually interpreted as a sign that the LV is ejecting blood into the ascending aorta.11In the acute phase, cardiac function was not restored. VA-ECMO-supported circulation was established resulting in a nearly non-pulsatile aortic pressure curve for up to 3 hours . In a cl12 With this setting, no haemodynamic signs of cardiac distension were observed, neither in the right nor the left side of the heart. This is in contrast to findings in a pig model without post-cardiotomy cardiogenic shock, where both LV end-systolic and end-diastolic volumes increase during ECMO-supported circulation.13 In the present study, the LVEDP gradually decreased from 21.0 ± 2.3 to 12.2 ± 1.5 mmHg from 15 to 180 minutes of mechanical circulatory support (mean from 7.9 ± 1.1 mmHg after 15 minutes to 9.5 ± 1.2 mmHg at 180 minutes of ECMO-supported circulation was observed (mean decreased from 21.7 ± 2.3 to 17.8 ± 1.3 mmHg.In the present study, the flow in the ECMO circuit is set at 72 mL/min/kg, 80% of calculated full CPB flow in this pig model, a typical initial setting in a clinical situation when total circulatory support with ECMO is needed. support . There w support . Only a observed . Correspmax was close to the mean aortic blood pressure resulting in an almost flat aortic pressure curve (14In addition to the standard postoperative setup with pulse-oximetry, ECG, central venous and arterial pressures, the animals in the present study were instrumented with a left ventricular pressure catheter and a coronary artery flow probe. During the 180 minutes of VA-ECMO-supported circulation, the LVSPre curve . The cycre curve . The cycre curve . The inc15 At the end of the experiments, left ventricular myocardial tissue water content averaged 84.2 ± 0.2%; clearly increased compared to 80.0 ± 0.4% found in non-ischaemic pig hearts.16 The development of tissue oedema might compromise myocardial perfusion.After 60 minutes of reperfusion with ECMO-supported circulation, the myocardial perfusion measured by microspheres was reduced in the midmyocardial and the subendocardial compared to the subepicardial wall layer both in the anterior, posterior and septal regions of the LV . In the 1719 and thus underestimate myocardial perfusion as computed from the microspheres. However, only occasionally, a low-velocity forward flow profile was observed with Doppler.An alternative explanation to the apparent deterioration of myocardial perfusion is the minor increase in pulsatile aortic pressure during the 180 minutes of circulatory support with ECMO . This co20Studies of the pathophysiology in healthy hearts in an animal model limit the direct clinical relevance. Furthermore, the duration of VA-ECMO in the present study was only 3 hours, and must be extended when focusing primarily on restoration of cardiac function. Failure to decompress a severely dysfunctional LV during VA-ECMO is frequently reported to cause pulmonary oedema, a complication that may develop in the present model if the time on ECMO-supported circulation is extended.21 However, Thebesian veins contribute to volume build-up in the left side of the heart.22In humans, the bronchial arterioles form an anastomotic network with the pulmonary arterioles. Drainage of blood into the left atrium via the pulmonary veins contributes to volume and pressure build-up in the left atrium and ventricle. It is not clear whether this network is found in the domestic pig.23We observed a lack of correlation between LAD flow measured by transit-time flowmetry and myocardial perfusion measured by microspheres. We have attributed this to regional differences in the myocardium, but there is also the possibility that it could be caused by arteriovenous shunting in the myocardium.In the clinical setting, active decompression of the LV with an Impella device or a LV vent should be considered whenever the ‘breakthrough waves’ on the arterial pressure curve are less than 10 or 15 mmHg in height. This study suggests that pressure build-up and distension of the LV does not always occur in a severely affected LV with only ripples on the arterial pressure curve, and that venting of the LV during ECMO may not be needed, at least in the very early phase of post-cardiotomy circulatory support. However, left ventricular decompression should be considered when there are signs of a pressure build-up in the left atrium and ventricle.With ECMO-support and critical left ventricular failure after CPB and cardioplegic arrest, coronary artery blood flow is maintained in the acute phase, even in the presence of a non-pulsatile aortic pressure profile. However, tissue oedema rapidly develops, and myocardial perfusion decreases, earlier and more pronounced in inner wall layers of the LV.Click here for additional data file.Supplemental material, 907557__Supplemental_file for Myocardial perfusion and cardiac dimensions during extracorporeal membrane oxygenation–supported circulation in a porcine model of critical post-cardiotomy failure by Atle Solholm, Pirjo-Riitta Salminen, Lodve Stangeland, Christian Arvei Moen, Arve Mongstad, Bård Svenheim, Rune Haaverstad and Ketil Grong in Perfusion


Myocardial fibrosis is a major determinant of outcome in aortic stenosis (AS). Novel fast real-time (RT) cardiovascular magnetic resonance (CMR) mapping techniques allow comprehensive quantification of fibrosis but have not yet been compared against standard techniques and histology.n = 110) and left ventricular (LV) endomyocardial biopsy (n = 46) at transcatheter aortic valve replacement (TAVR). Midventricular short axis (SAX) native, post-contrast T1 and extracellular volume fraction (ECV) maps were generated using commercially available modified Look-Locker Inversion recovery (MOLLI) (native: 5(3)3, post-contrast: 4(1)3(1)2) and RT single-shot inversion recovery Fast Low-Angle Shot (FLASH) with radial undersampling. Focal late gadolinium enhancement was excluded from T1 and ECV regions of interest. ECV and LV mass were used to calculate LV matrix volumes. Variability and agreements were assessed between RT, MOLLI and histology using intraclass correlation coefficients, coefficients of variation and Bland Altman analyses.Patients with severe AS underwent CMR before (p = 0.073) and septal region of interest . MOLLI native T1 time was in median 20 ms longer compared to RT (p < 0.001). Agreement between RT and MOLLI was best for ECV (ICC > 0.91), excellent for post-contrast T1 times (ICC > 0.81) and good for native T1 times (ICC > 0.62). Diffuse collagen volume fraction by biopsies was in median 7.8%. ECV  and LV matrix volumes  were the only parameters associated with histology.RT and MOLLI derived ECV were similar for midventricular SAX slice coverage (26.2 vs. 26.5, RT mapping offers fast and sufficient ECV and LV matrix volume calculation in AS patients. ECV and LV matrix volume represent robust and universally comparable parameters with associations to histologically assessed fibrosis and may emerge as potential targets for clinical decision making. Left ventricular (LV) remodelling including hypertrophy, interstitial volume alteration and expansion is a common feature in cardiac diseases . Severe Between January 2016 and August 2019 patients who underwent transcatheter aortic valve replacement (TAVR) following heart team consensus decision were approached for study participation. Ethical approval was obtained from the local ethics committee. All patients gave written informed consent before participation. The study was conducted according to the principles of the Helsinki Declaration. The study was funded by a grant from the German Research Foundation .2, in-plane resolution 1.41 × 1.41 × 8 mm3, TR/TE = 2.7/1.12 ms, nominal flip angle 35°, bandwidth 1085 Hz/pixel and a total acquisition of 11 heart beats. Additionally, RT T1 single-shot myocardial T1 maps [2 and 8 mm slice thickness using a FOV 256 × 256 mm2 in combination with a resolution of 512 complex data points per radial spoke (two-fold oversampling). Other parameters were TR/TE = 2.67/1.66 ms, nominal flip angle 4°, bandwidth 850 Hz/pixel and total acquisition time of 4 s following a non-selective adiabatic inversion pulse. Correct overlapping of underlying T1 weighted images was checked by the operator prior to drawing of the respective region of interest (ROI). The ROI was then propagated to all underlying T1 weighted images to create a midventricular SAX slice coverage and a septal ROI separately. To avoid partial volume effects of the blood pool or adjoining non-myocardial structures ROI delineation was carefully reviewed on all underlying T1 weighted images. ECV was calculated for the entire myocardium as well as the septal ROI separately as recently published [CMR imaging was carried out using a standard protocol including balanced steady state free precession (bSSFP) functional imaging, native mapping prior to gadolinium application and post-contrast mapping 20 min after contrast administration as well as late gadolinium enhancement (LGE) imaging. Cardiac volumes were assessed in short axis (SAX) stacks acquired using electrocardiogram(ECG) gated bSSFP cine imaging. Mapping sequences comprised commercially available MOLLI (native: 5(3)3, post-contrast: 41)3(1)2) sequences –21 2) se T1 maps  . The study procedure accounted for additional 5 to 10 min of intervention time. TAVR and CMR were performed within 48 h. Biopsies were fixed in 10% paraformaldehyde (PHA) and embedded in paraffin. Fibrosis was assessed using quantitative morphometry  and defined as blue area in Masson trichrome staining  in relation to total tissue area. Collagen volume fraction (CVF) was defined as the amount of total fibrosis, including subendocardial fibrosis (ischemic), interstitial diffuse fibrosis (reactive) and replacement (scar) fibrosis  P-values provided are two-sided, an alpha level of 0.05 and below was considered statistically significant. Statistical agreement and variability were assessed in 20 randomly selected patients using the coefficient of variation  and intra-class correlation coefficients (ICC). Intra-observer reproducibility was performed with 4 weeks in between repeated analyses. ICCs were evaluated based on a model of absolute agreements as well as on a model for consistency [Continuous parameters are presented as median values with interquartile range (IQR) after testing for normal distribution using the Shapiro-Wilk test. Non-normally distributed parameters underwent logarithmic transformation to achieve normal distribution. Dependent variables were compared using the Wilcoxon signed-rank test. Correlations were assessed using Pearson correlation coefficients. sistency . ICC wassistency . StatistBaseline characteristics are reported in Table CVF as assessed by biopsy was in median 10.5%  with 7%  histologically defined as dCVF. Replacement fibrosis was present in 10 biopsies ranging between 1 and 76% of CVF within these biopsies. Subendocardial fibrosis was present 18 biopsies ranging between 1 and 81% of CVF of the biopsies. After accounting for different fibrosis pattern, dCVF accounted for 7.8% of total biopsy area .p < 0.001 for all). However, calculated ECV were similar for midventricular SAX slice coverage (p = 0.073) as well as the septal ROI (p = 0.216). Differences between MOLLI and RT sequences were numerically smaller for the septal ROI compared to the midventricular SAX slice coverage. ECV  were the only parameter associated with dCVF as assessed by biopsies. In contrast, ECV derived cellular volume did not correlate significantly with dCVF . There was no correlation comparing the proportion of dCVF in relation to healthy myocardium to native T1 (5(3)3 MOLLI r = 0.08, p = 0.600; RT r = 0.09, p = 0.547) or post-contrast T1 . Furthermore, there was no correlation between histologically assessed total fibrosis and neither 5(3)3 MOLLI derived native T1  or ECV  nor RT native T1 mapping  or ECV  assessments. Out of 16 patients with atrial fibrillation, 4 patients had combined data on CMR and histologically derived fibrosis. Correlation coefficients of ECV and dCVF were numerically higher for RT  as opposed to MOLLI .CMR derived tissue characterisation is reported in Table OI p = 0.16. DiffeAgreements of MOLLI and RT mapping are reported in Tables The present study reports 4 major findings. First, novel RT native T1 and ECV mapping agrees well with MOLLI sequences suggesting adequate estimation of myocardial fibrosis. Second, the relationship between fibrosis assessment by CMR and LV endomyocardial biopsy derived histology is complex and both modalities provide different and complementary information. Third, ECV and LV matrix volume are the only parameters showing a significant correlation with dCVF and may therefore serve as non-invasively obtained surrogates of biopsy derived histological extent of interstitial fibrosis with potential implications for clinical decision making and follow up surveys. Last, RT mapping may be particularly suited for examinations depending on high temporal resolution e.g. in patients prone to dyspnoea, arrhythmias or stress mapping.The present data demonstrates good agreement between novel RT and 5(3)3 MOLLI mapping techniques for native T1 values, which is generally better for the septum as compared to the overall myocardium. Higher and excellent agreement is found for ECV for midventricular SAX slice coverage and the septal ROI, showing no statistical numerical difference between RT and MOLLI sequences. Additionally, and in opposite to native or post-contrast T1, ECV is less prone to factors influencing magnetization thus being more universally comparable . The potIn contrast, agreement with fibrosis assessment by histology is low. Neither native 5(3)3 MOLLI nor RT T1 as well as ECV mapping did correlate with total fibrosis, which is a distinct deviation from previous assumptions , 28 but First, despite of limited guidance for biopsies performed in the cath-lab and their focal nature of assessment of endomyocardial tissue, biopsies are considered to represent the whole ventricular myocardium. Biopsies performed in the CMR suite may overcome limitations owed to guidance , neverthr = 0.78) using a 3-(3)-3-(3)-5 MOLLI sequence. Multiple factors may contribute to this difference. It could be partially related to the different sequence used, it could be influenced by lower sample size and time differences between CMR and biopsy (1 to 30 days) or the size of the latter, since patients undergoing open-chest aortic surgery underwent biopsies of the full width of myocardium as opposed to our endomyocardial biopsy. In line with our data de Meester de Ravenstein also reported low correlation for native T1 to histology. Kammerlander et al. [r = 0.49) but association to cardiovascular outcome in 473 consecutive patients referred to CMR. Similar to Treibel et al. [Second, it has to be noted that ECV reflects diffuse myocardial fibrosis. Reports for the correlation of ECV to histologically assessed fibrosis vary. Better correlation than ours was found by de Meester de Ravenstein  reportinr et al.  reportedl et al.  we did nl et al. . Indeed,Third, despite the focal nature of biopsies, one would expect lower but significant correlations of fibrosis and T1 as previously reported , 28. TheTechnical challenges in MOLLI T1 mapping comprise banding artefacts depending on magnetic field strengths. CMR imaging in general is prone to artefacts caused by inadequate breath-holding. MOLLI sequences require a breath hold for up to 17 heartbeats . ConsequFurthermore, none of the above covers the entire pathophysiology of AS . Whilst Whilst intra- and inter-observer reproducibility was assessed underlining excellent post-processing reproducibility, data on inter-study reproducibility is lacking which would be desirable for follow-up surveys of cardiac remodelling. With this perspective, further clinical follow-up studies are warranted. Mapping was performed in one representative midventricular SAX slice only, future studies should consider an apical, midventricular and basal slice for more comprehensive assessments. We have not demonstrated a significant association of native and post contrast T1 mapping based on RT and MOLLI (native 5(3)3 and post-contrast 4(1)3(1)2) with histology. This may partially be due to the specific sequences used. Both T1 mapping sequences utilized are affected by imperfect inversion due to T2 relaxation. While the MOLLI sequence is additionally affected by T2 and magnetization transfer effects during the bSSFP readout , this dRT mapping offers fast and sufficient ECV and LV matrix volume calculation in AS patients. RT ECV and LV matrix volume represent robust and universally comparable parameters that agree well with those derived from a specific MOLLI sequence. Since they show associations to histologically assessed fibrosis they may well emerge as a potential target for clinical decision making.


TLV) at the expense of decreases in the native LV cardiac output (CONLV), the underlying mechanism determining COTLV remains unestablished. This study aims to clarify the mechanism and develop a framework to predict COTLV under known LVAD flow (COLVAD). We previously developed a generalized framework of circulatory equilibrium that consists of the integrated CO curve and the VR surface as common functions of right atrial pressure (PRA) and left atrial pressure (PLA). The intersection between the integrated CO curve and the VR surface defines circulatory equilibrium. Incorporating LVAD into this framework indicated that LVAD increases afterload, which in turn decreases CONLV. The total LV cardiac output (COTLV) under LVAD support becomes COTLV = CONLV+EFe · COLVAD, where EFe is effective ejection fraction, i.e., Ees/(Ees+Ea). Ees and Ea represent LV end-systolic elastance (Ees) and effective arterial elastance (Ea), respectively. In other words, LVAD shifts the total LV cardiac output curve upward by EFe · COLVAD. In contrast, LVAD does not change the VR surface or the right ventricular CO curve. In six anesthetized dogs, we created LV failure by the coronary ligation of the left anterior descending artery and inserted LVAD by withdrawing blood from LV and pumping out to the femoral artery. We determined the parameters of the CO curve with a volume-change technique. We then changed the COLVAD stepwise from 0 to 70–100 ml/kg/min and predicted hemodynamics by using the proposed circulatory equilibrium. Predicted COTLV, PRA, and PLA for each step correlated well with those measured . The proposed framework quantitatively predicted the upward-shift of the total CO curve resulting from the synergistic effect of LV systolic function and LVAD support. The proposed framework can contribute to the safe management of patients with LVAD.Left ventricular assist device (LVAD) has been saving many lives in patients with severe left ventricular (LV) failure. Recently, a minimally invasive transvascular LVAD such as Impella enables us to support unstable hemodynamics in severely ill patients. Although LVAD support increases total LV cardiac output (CO Heart failure is one of the most challenging cardiac pathophysiologies, and the survival rate remains unacceptably poor despite the guideline-recommended optimal medical therapy . AlthougThe latest advance in medical technology has allowed us to develop minimally invasive transvascular LVAD such as Impella® . The fact that LVAD promotes recovery of myocardial function makes temporary LVAD implantation as a practical therapeutic option in the treatment of heart failure . In myocHemodynamic responses to the “off-pump” trial were critical in weaning LVAD and predicting long-term cardiac stability after weaning . TherefoThis study aims to develop a framework to predict the impact of partial LVAD support on hemodynamics. To answer this complex question, we first analyzed the quantitative effect of partial LVAD support on the LV pressure-volume relationship by using the concept of the left ventricular-arterial coupling . We thenRA). They defined the circulatory equilibrium by the intersection between the CO curve and the VR curve. Although this framework explains numerous pathophysiological conditions such as volume overload, heart failure, and exercise, they failed to express unilateral heart failure and resultant volume redistribution between the systemic circulation and the pulmonary circulation. This inability of the Guyton's framework makes its application seriously limited.In the 1950s, Guyton proposed a disruptive concept, the framework of circulatory equilibrium, because the CO curve alone could not determine cardiac output in the closed-loop circulation . They opRA and left atrial pressure (PLA)  . In thisRA, on COLV is negligible because PRA is much lower than systemic arterial pressure. Therefore, we described the COLV as the curve, not the surface.In the systemic circulation, the effect of downstream pressure, PLA approximates the native CO curve without LVAD (CONLV) asAs explained in L and HL represent parameters of the left heart.where Sa) line determines SV for a given preload. LVAD flow (COLVAD) increases arterial pressure (AP) independent of LV ejection, thus shifts the Ea line upward by R · COLVAD, where R is systemic resistance. This upward shift of the Ea line indicates the increases LV afterload, and, in turn, decreases SV (Rearranging Equation 2 givese) as the ratio of Ees to Ees+Ea. Dividing ΔSV by T yields the decrease in COLV (ΔCOLV) aswhere T is the cardiac cycle length. We define the effective ejection fraction  became following equation  curve becomes as following . Animal care was performed in strict accordance with the Guide for the Care and Use of Laboratory Animals by the US National Institutes of Health, and experiments were approved by the Committee on Ethics of Animal Experiment, Kyushu University Graduate School of Medical Sciences. All dogs were initially anesthetized with pentobarbital sodium (25 mg/kg) and vecuronium bromide (0.2 mg/kg). We then performed endotracheal intubation and started mechanical ventilation. We maintained an appropriate anesthesia level during the experiment by continuous infusion of isoflurane (1–2%) and pentobarbital sodium through a 5F catheter introduced into the right femoral vein during the experiment. We isolated the bilateral carotid sinuses and kept intra-sinus pressure constant at 100 mmHg to abolish the arterial baroreflex  around the ascending aorta to measure COLV. We ligated the major branches and the first diagonal branch of the left anterior descending coronary artery (LAD), and added left circumflex coronary artery (LCx) ligation as needed to induce substantial worsening of LV function. After the condition was well-stabilized, we used a centrifugal pump  as LVAD . We also inserted 5F catheter to left femoral vein to administer physiological saline as needed to keep mean AP above 70 mmHg for conducting 6–7 h experiment.We used adult mongrel dogs of either gender weighing 16.9–22 kg  in the COLV-PLA relation and three-parameters  in the CORV-PRA-PLA relation by incorporating obtained hemodynamics into Equations 1 and 7 with the least-squares method.Before LVAD support, we infused 250 ml of 10% dextran and waited to reach a steady-state of hemodynamics. We then withdrew blood stepwise at 2.5 ml/kg in each step (up to 4 or 5 steps) while recording PLVAD stepwise at 5 ml/min/kg in each step from ~70–110 ml/min/kg to 0 ml/min/kg and measured the PLA, PRA, and COLV. Adding the COLVAD to the measured COLV yielded the total LV cardiac output, COTLV, which equals CORV, and venous return, COVR. We then calculated the EFe by substituting both the parameters of the COLV curve (SL and HL) determined above and the equilibrated COLV and PLA at the maximal COLVAD into Equation 4. We similarly obtained VRmax by substituting the COVR, PRA, and PLA at the maximal COLVAD into Equation 8. Assuming that EFe and VRmax are constant irrespective of COLVAD, we predicted COTLV, PRA, and PLA under various LVAD supports by simultaneously solving Equations 6–8. We compared the predicted hemodynamic values with those measured.After the CO curve estimation, we decreased COLV curve and CORV surface by changing blood volume is impractical if not impossible in clinical settings. Thus, we employed the simplified estimation of hemodynamics on LVAD for another five dogs. We determined the parameters of the COLV curve and CORV surface under LVAD from three equilibrium points induced by the changes in COLVAD. In other words, three sets of measured COLV, PLA, and COLVAD uniquely determined SL, HL, and EFe in Equation 5. We similarly estimated the SR, HR, and α by three sets of measured CORV, PRA, and PLA in Equation 7. After confirming that VRmax calculated in Equation 8 did not change despite the changes in COLVAD, we predicted COTLV, PLA, and PRA under various LVAD supports from Equations 6–8 and COTLV =CORV =COVR, and compared them with those measured. In this prediction, we excluded the data set that had been used to estimate the COLV curve and the CORV surface to avoid logical circularity.The estimation of COP < 0.05 in paired t-test . We calculated the coefficient of determination (r2) for the goodness of fit and the standard error of estimate (SEE) for predictive accuracy.All analog signals were digitized at 200 Hz using a 16-bit analog-to-digital converter  with a dedicated laboratory computer system. Each data was averaged over 9 s and used for analysis after hemodynamic stability. Differences between groups were considered significant at LA compared to baseline (P = 0.0019), indicating MI induced LV failure. In contrast, MI did not noticeably affect mean AP (MAP), heart rate (HR), CO, or PRA.LA increased CONLV. A two-parameters logarithmic function approximates the CONLV curve (Equation 1) reasonably well. RV in response to changes in PRA and PLA. Increases in PRA increased CORV, while increases in PLA decreased CORV. A surface generated by the three-parameters logarithmic function of PRA and PLA  approximated the changes in CORV reasonably well.NLV curves and CORV surfaces in all six dogs. The fact that the coefficient of determination was quite high (r2 = 0.94–0.99) in each dog suggested that the 2-parameter function and 3-parameter function accurately represent the CONLV curve and CORV surface, respectively.LVAD. Decreases in COLVAD increased COLV and PLA, while decreased the COTLV and AP. Despite changes in AP, HR remained unchanged because of the abolishment of the baroreflex. e and VRmax for each dog. As we expected, the creation of MI markedly lowered EFe. VRmax varied among dogs, indicating the variability of stressed blood volume. TLV, PRA, and PLA in all dogs. Regression analysis revealed that the predicted COTLV , PRA , and PLA  matched well with those measured.Shown in LVAD levels. By using three points hemodynamic data in each dog , PRA  and PLA  demonstrated the good agreement between the predicted and measured.each dog , we estimeasured . RegressNLV curve and the CORV surface with a volume-changing technique. Furthermore, in Protocol 2, the hemodynamic assessment during the small perturbations of COLVAD enabled us to predict the COTLV, PLA, and PRA when LVAD was weaned.In this study, we analyzed the LVAD interaction with the native LV cardiac output in determining total LV cardiac output. We then developed a framework to predict the impact of LVAD on hemodynamics. In Protocol 1, we showed that we could predict hemodynamics on LVAD by determining the COTLV curve upward by EFe · COLVAD, indicating the poorer LV function, the poorer increases in COTLV. The depressed LV is more susceptible to the LVAD-induced increases in LV afterload; that is, LVAD decreases the SV more in low LV contractility than in high LV contractility (Equation 3). In addition, the results of a computational study by using a multi-element cardiovascular model were in line with our results  · COLVAD. The multi-element cardiovascular model cannot easily attribute a particular observation to a specific element of the system. Despite small increases in COTLV in our study, we found the significant decreases in PLA from 19 to 7 mmHg  (Equation 3). This is equivalent to say that EFe equals SV divided by end-diastolic volume in excess of V0, where V0 is the volume axis intercept of the end-systolic pressure-volume relationship , calculated by echocardiogram, under LVAD support. Because EF is the ratio of SV to end-diastolic volume (Ved), EF could markedly change with LVAD support. Furthermore, regional ischemia significantly increases the V0  · FECMO, where FECMO indicates the ECMO flow , and results in increases of PLA.We previously reported the impact of extracorporeal membrane oxygenation (ECMO) on circulatory equilibrium and showed that ECMO also suppresses the COCMO flow . In termTLV curve upward by EFe · COLVAD, indicating the poorer LV function, the poorer increases in COTLV. This relationship may become important for the management of transvascular LVAD. Impella 2.5 or sometimes CP cannot necessarily generate sufficient flow to establish total support where LV is no longer ejecting , EFe in LV, CORV surface, and VR surface as shown in RA, and PLA), while we did not compare the parameters calculated by our proposed equation to those of direct measurements. Further investigations might be needed to evaluate the utility of this method in terms of the estimation of cardio-vascular properties. The proposed framework allows us to predict the hemodynamics even after LVAD weaning. Since the hemodynamic assessment during “off-pump” is critical for patients undergoing LVAD removal (The present study suggested that, with small changes in CO removal , the pro removal  but alsoLVAD among dogs in our study. It may well be attributed to the fact that we conducted the experiment where LV remained ejecting under LVAD support. It means that the degree of MI affected how much we could increase COLVAD. LV would quickly become the non-ejecting state as we increase COLVAD if MI severely impairs LV contractility, indicating that the variability of maximal COLVAD under the LV ejecting condition depends on MI size. Third, we did not measure either the pressure-volume loop or echocardiogram. Although the EFe we used in the equation is different from standard EF calculated by echocardiogram as we addressed in the discussion, the standard EF as well as the direct measured EFe by pressure-volume loop in the same dog may help the interpretation of EFe obtained from the equation. Further detailed experiment might be needed to clarify the accuracy of our method in estimating EFe. Fourth, our proposed framework is a static mathematical model of circulation. Thus, we did not consider dynamic hemodynamic change during the cardiac cycle in LV under LVAD support. To improve the estimation accuracy of hemodynamics, we need to adopt the fluid dynamics and dynamic change in cardio-vascular properties into our framework. Lastly, we utilized the previously reported values as the slopes of the VR surface for simplicity (There are several limitations in our study. First, we conducted experiments using anesthetized and open-chest dogs. Furthermore, we isolated the bilateral carotid sinuses and cut the vagal trunks. Since both the baroreflex and other reflexes through the vagal nerves alter the vascular as well as cardiac properties , we elimmplicity . NeedlesThe proposed framework is capable of quantitatively predicting the hemodynamic impact of partial LVAD support. Circulatory equilibrium is generalizable and essential for understanding the cardiovascular system, including LVAD. It would provide the physiological insight into hemodynamics on LVAD and contribute to the safe management of patients with LVAD.The datasets generated for this study are available on request to the corresponding author.The animal study was reviewed and approved by the Committee on Ethics of Animal Experiment, Kyushu University Graduate School of Medical Sciences.TK, KSa, TN, and KSu conceived of the presented idea and designed the study. TK and KSa performed the data collection. TK, KSa, and TN performed the analysis and took the lead in writing the manuscript. TK, KSa, and KSu edited and revised manuscript. All authors discussed the results and contributed to the final manuscript. All authors approved the final version of the manuscript and agree to be accountable for the study.KSa received research funding from Omron Healthcare Co., Abiomed Japan K.K., and Zeon Medical Inc., and honoraria from Abiomed Japan K.K. KSu received research funding from Omron Healthcare Co. and honoraria from Abiomed Japan K.K. The remaining 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. The handling editor declared a past co-authorship with one of the authors KSu.


Conduction system damage is the most common complication of transcatheter aortic valve replacement (TAVR), which frequently requires placement of a permanent pacemaker. Bundle branch reentry (BBR) is a well-recognized mechanism of ventricular tachycardia (VT) in the setting of abnormal intraventricular conduction. We describe a case of a patient with post-TAVR intraventricular conduction abnormalities who presented with intermittent advanced atrioventricular block and BBR VT and discuss the potential risks, diagnosis, and management of BBR after TAVR. Therefore, an electrophysiology study (EPS) was performed.A 76-year-old female with a medical history of coronary artery disease and severe aortic stenosis who underwent transcatheter aortic valve replacement (TAVR) with a 23-mm Sapien S3  prosthetic aortic valve presented to the clinic. Her preoperative electrocardiogram (ECG) showed no intraventricular conduction abnormalities (QRS duration: 90 ms) and a mildly prolonged P–R interval (212 ms). The postoperative period was complicated by the development of advanced conduction system abnormalities that manifested as alternating left and right bundle (RB) branch block  as well as transient complete heart block. Her postoperative echocardiogram showed normal left ventricular (LV) systolic function and a normally functioning aortic prosthetic valve. A dual-chamber permanent pacemaker was subsequently implanted. She presented three days later with complaints of recurrent brief episodes of dizziness and one episode of syncope. A review of the stored intracardiac electrograms from her pacemaker revealed multiple logged events of monomorphic tachycardia at average rates of 205 bpm to 223 bpm lasting from six seconds to 25 seconds. The timing of her syncopal episode corresponded with the longest logged tachycardia event. There was ventriculoatrial (VA) dissociation during these tachycardia events . The AV block cycle length was 420 ms. There was no VA conduction. Frequent spontaneous ventricular premature beats (VPBs) with the RB potential preceding V by 45 ms were noted. LBBB QRS morphology similar to that in sinus rhythm and an RB-V interval longer than that recorded in sinus rhythm strongly suggested a bundle branch reentry (BBR) mechanism of these VPBs . A wide complex tachycardia identical to the above beats’ LBBB QRS morphology was induced with triple ventricular extrastimuli from the right ventricle . The tachycardia was hemodynamically unstable and terminated spontaneously. Thus, pacing maneuvers during tachycardia were not feasible. The tachycardia mechanism was consistent with BBR VT based on the following electrophysiological findings: evidence of advanced intraventricular conduction defect during sinus rhythm; presence of VA dissociation during tachycardia; typical LBBB QRS morphology during tachycardia, which was similar to the patient’s LBBB QRS pattern in sinus rhythm; stable RB potential that preceded each ventricular activation with an RB-V interval during tachycardia longer than that recorded in sinus rhythm (35 ms versus 45 ms); spontaneous changes in the RB–RB intervals during tachycardia preceding similar changes in the V–V intervals; and spontaneous termination of the tachycardia with retrograde conduction block to the RB (V with no RB).She presented to the electrophysiology laboratory in sinus rhythm with a cycle length of 950 ms, 1:1 atrioventricular (AV) conduction, and intermittent LBBB. For the EPS, her pacemaker was programmed to the VVI 45-bpm mode. The RB–ventricular (RB-V) interval was 35 ms. The proximal His-bundle potential could not be consistently obtained. A few recorded beats with the proximal His-bundle potential revealed a markedly prolonged intra-Hisian (H-RB) conduction time of 145 ms and an H–V interval of 180 ms Following successful RB ablation (as evidenced by the development of RBBB), the index tachycardia was no longer inducible and there were no spontaneous VPBs with the RB potential preceding V. Also following ablation of the RB, an RBBB QRS pattern was noted. Additionally, 1:1 AV conduction with a P–R interval of 270 ms was observed. The RB potential could no longer be recorded at this point. No other sustained ventricular arrhythmia could be induced with programmed ventricular stimulation. The patient remained free from the presenting symptoms and arrhythmia over the ensuing three months.We herein describe a case of a patient with post-TAVR intraventricular conduction abnormalities who presented with intermittent advanced AV block and BBR VT.2 Although cardiac dilatation may potentially facilitate BBR by functional slowing of transseptal conduction between the bundle branches, a significant conduction delay within the His–Purkinje system is considered to be the major prerequisite for this arrhythmia mechanism. Aortic and mitral valve surgery are known causes of BBR VT. Because of the close anatomic proximity of the His bundle and proximal bundle branches to the valvular annuli, injury to them during corrective valve surgery is not uncommon. BBR has been reported in 10% to 29% of patients with inducible sustained VT after valve surgery.4 In this context, BBR VT usually manifests early in the postoperative period  and commonly occurs in the setting of preserved LV systolic function. BBR VT has been recently reported in two cases after TAVR complicated by conduction abnormalities.6 Similar to in our case, both patients presented with arrhythmia soon after the procedure and had relatively preserved LV systolic function.BBR is a well-recognized mechanism of VT in patients with advanced conduction system disease. Although structural heart abnormalities, particularly those resulting in cardiac dilatation, account for the majority of reported cases, BBR VT has been reported in patients without apparent structural heart disease or cardiac dilation.8 Conduction abnormalities such as high-grade AV block and new LBBB are common after TAVR , and incidence rates have not decreased despite improvements in operator experience and the introduction of newer-generation valves in more recent years.10 An autopsy report has suggested necrosis of the His bundle and proximal LBBB due to mechanical compression by the expanded prosthetic valve to be the underlying pathology of post-TAVR conduction abnormalities.11 Reported rates of this complication have been higher with the use of self-expandable valves relative to those with balloon-expandable valves.10TAVR has become a commonly performed procedure for the treatment of severe aortic stenosis as an alternative to surgical aortic valve replacement in high- and moderate-risk surgical candidates. Recent data support broadened indications for this technology; thus, it is likely to emerge as a primary approach for severe aortic stenosis even in patients at lower surgical risk.12 Most published TAVR series do not detail the incidence of SCD separately from that of cardiovascular mortality. One of the possible explanations is that the mode of death is frequently difficult to ascertain, particularly when performing a retrospective data analysis. In a recent analysis of prospectively collected data from 3,726 consecutive TAVR patients in 18 centers worldwide, the cumulative rates of SCD at one and two years of follow-up were 1.0%  and 1.8%  and the development of new LBBB  were independent predictors of SCD.13 Further, a QRS duration of more than 160 ms was found to be the best discriminator for predicting SCD in post-TAVR LBBB patients . In this cohort, one of 10 patients died suddenly within one year after TAVR (rate of SCD of 9.9% at one year of follow-up). Although the exact mechanism of SCD  could not be determined, the presence of a permanent pacemaker appeared to have no impact on SCD risk in this analysis. In the prospective Ambulatory Electrocardiographic Monitoring for the Detection of High-degree AV Block in Patients with New-onset Persistent LBBB after TAVI (MARE) study, 103 patients with new-onset persistent post-TAVR LBBB were implanted with an insertable loop monitor and were followed up with for one year.14 Progression to high-degree AV block was noted in 15 (15%) patients, while 10 (10%) received a pacemaker for symptomatic bradycardia. VT was documented in 13 (13%) patients including 12 cases of nonsustained (duration: 6–11 seconds) and one case of sustained VT. Based on these findings, two patients received implantable cardioverter-defibrillators (ICDs) and four patients were treated with antiarrhythmic medications.The available data on the risk of sudden cardiac death (SCD) following TAVR are scarce. Although AV block is considered to be the major potential mechanism of SCD in this setting, cases of SCD attributable to ventricular arrhythmias have been reported.15 There are currently no practical approaches established for identifying patients at risk for BBR VT after TAVR. The utility of EPS in patients with post-TAVR new-onset intraventricular conduction defects for evaluating the risk of ventricular arrhythmias (including BBR) or progression to high-degree AV block is yet to be determined.The incidence of BBR VT after TAVR is unknown. This issue might be compounded by the fact that EPS is currently not routinely performed in many patients with documented VT prior to ICD placement, particularly in the setting of reduced LV systolic function. Given the frequency of conduction system complications following TAVR, it is conceivable to speculate that some cases of BBR remain undiagnosed. Unrecognized BBR VT may result in sudden death or cause significant morbidity secondary to recurrent syncope or ICD shocks. Antiarrhythmic medications are usually ineffective, whereas the ablation of a bundle branch is a highly successful and potentially curative procedure.19 The role of ICDs in BBR patients without these risk markers is less clear. Limited evidence indicates that these patients may have a favorable prognosis following the successful ablation of BBR.19 Our patient had preserved LV systolic function and no inducible VTs other than BBR. Thus, we elected not to pursue upgrading her pacemaker to an ICD.The available data from small retrospective series suggest that the long-term outcome of patients with BBR VT treated by catheter ablation is primarily driven by underlying cardiac pathology, and the decision about ICD placement should be guided by conventional risk markers for sudden death such as LV function or evidence of scar-related ventricular arrhythmias (spontaneous or inducible), among others.In summary, our case indicates that BBR should be strongly considered as a potential mechanism of syncope or documented VT, particularly occurring in the early postoperative period, in patients after TAVR procedure complicated by new intraventricular conduction defects.


Cardiac magnetic resonance imaging (CMR) allows for detection of fibrosis in hypertrophic cardiomyopathy (HCM) by quantification of the extracellular volume fraction (ECV).To quantify native T1 mapping and ECV in cats. We hypothesize that native T1 mapping and ECV will be significantly increased in HCM cats compared with healthy cats.Seventeen healthy and 12 preclinical HCM, age‐matched, client‐owned cats.Prospective observational study. Tests performed included indirect blood pressure, CBC, biochemical analysis including total thyroid, urinalysis, transthoracic echocardiogram, and CMR. Cats were considered healthy if all tests were within normal limits and a diagnosis of HCM was determined by the presence of left ventricular concentric hypertrophy ≥6 mm on echocardiography.P < .0001), native T1 mapping , and ECV . Variables of diastolic function including deceleration time of early diastolic transmitral flow (DTE), ratio between peak velocity of early diastolic transmitral flow and peak velocity of late diastolic transmitral flow (E : A), and peak velocity of late diastolic transmitral flow (A wave) were significantly correlated with ECV .There were statistically significant differences in LV mass (healthy = 5.87 g, HCM = 10.3 g, Quantitative assessment of cardiac ECV is feasible and can provide additional information not available using echocardiography. Apeak velocity of late diastolic transmitral flowCMRcardiac magnetic resonance imagingDTEdeceleration time of early diastolic transmitral flowE : Aratio between E and AECVextracellular volumeE/SrCEratio between peak velocity of early diastolic transmitral flow and peak circumferential strain rate during early diastoleE/SrREratio between peak velocity of early diastolic transmitral flow and peak radial strain rate during early diastoleGLPSglobal longitudinal strainIVSdinterventricular septal thickness in diastoleIVSsinterventricular septal thickness in systoleLAAleft auricular appendageLA : AoSAX and Aoratio between LALA FSleft atrial fractional shorteningLVFWdleft ventricular free wall thickness in diastoleLVIDdleft ventricular internal dimension in diastoleSrCEpeak circumferential strain rate during early diastoleSrREpeak radial strain rate during early diastole1Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats.One method to overcome the limitation of LGE to detect diffuse fibrosis is quantitative myocardial mapping. T1 mapping measures the longitudinal or spin‐lattice relaxation time, which is determined by how rapidly protons reequilibrate their spins after an excitation radiofrequency pulse. All tissues have inherent T1 relaxation times that are based on a composite of their cellular and interstitial components.The use of CMR to evaluate HCM in people has determined that native T1 values are prolonged and ECV increased in HCM.2The study protocol was reviewed and approved by the Institutional Animal Care and Use Committee (Protocol #17281) at the University of Illinois at Urban‐Champaign.2.1Twenty‐nine client‐owned cats were prospectively studied and recruited over a 2‐year period and emphasis was placed on recruiting older normal cats. Tests performed included physical examination, indirect blood pressure by Doppler method, CBC, biochemical analysis including total thyroid, urinalysis, transthoracic echocardiogram, and CMR with contrast. Cats were considered healthy if all diagnostic tests were within normal limits and a diagnosis of preclinical HCM was determined by the presence of either focal or generalized LV concentric hypertrophy ≥6 mm on echocardiography.2.2All transthoracic echocardiographic examinations were performed by a single investigator (RCF), using a digital ultrasound systemic , equipped with a 12‐MHz phased‐array transducer with simultaneous ECG monitoring. Awake, unsedated cats were positioned in right, and then left lateral recumbency on a raised table with a central opening. All images and cine loops were digitally stored and transferred to a separate workstation  for off‐line analysis. Each study was analyzed by the same observer (R.C. Fries) at the end of the recruitment period in random order. All studies were labeled by random identification number only and each measurement was repeated 5 times and the mean values were used for statistical analysis. Echocardiographic studies were performed before CMR on the same day.Assessment of LV size and function was performed using standard right parasternal short‐axis and long‐axis views, and left apical parasternal long‐axis views.SAX) and aortic diameter (Ao) measured from a right parasternal short‐axis view in early diastole timed to the earliest frame in which the closed aortic value cusps could be visualized. The ratio between LASAX to Ao (LA : Ao) was calculated. Additionally, the LA septal‐to‐free wall dimension maximum (LADMax) and minimum (LADMin) were measured from the right parasternal long‐axis 4‐chamber view. The LADMax and LADMin were measured mid‐chamber approximately parallel to the mitral annuls at end LV systole immediately before mitral valve opening (LADMax) and end LV diastole immediately after mitral valve closure (LADMin). The LA fractional shortening was calculated using the following formula: LA FS = [LADMax − LADMin]/LADMax × 100%. Left atrial appendage velocities, emptying (LAA emptying) and filling (LAA filling), were recorded using pulsed‐wave Doppler from the left cranial short‐axis view with the sampling gate placed as proximal the entrance of the LAA as possible.Assessment of left atrial (LA) size was performed from standard right parasternal long‐axis and short‐axis views. Variables measured included LA diameter , peak velocity of early diastolic transmitral flow (E), deceleration time of early diastolic transmitral flow (DTE), and peak velocity of late diastolic transmitral flow (A). Ratio between peak E to peak A (E : A) was calculated.Tissue Doppler imaging was performed with the highest available transducer frequency to record the velocity of lateral mitral annular motion from the left apical parasternal long‐axis view with the sampling gate placed on the lateral mitral annulus. The following variables were measured: peak early diastolic velocity (E′), peak late diastolic velocity (A′), and peak systolic velocity (S′).Speckle tracking postprocessing was used to evaluate circumferential, radial, and global longitudinal strain. The peak systolic radial and circumferential strains (SR and SC), and the peak radial and circumferential strain rates during the systole and early diastole  were measured at the level of papillary muscles. The variables E/SrCE and E/SrRE were derived from the E wave divided by the SrRE and SrCE, respectively. Global longitudinal strain was measured using the left apical 4‐chamber, left apical 2‐chamber, and left apical 5‐chamber views. All strain and strain rate variables were calculated by 6 segmental values . A global value was calculated as the mean value in all 6 segments and an overall global longitudinal strain was calculated as the average of the global longitudinal strain values from the 3 long‐axis apical views.2.3The morning of the CMR procedure, all cats had 1 to 2 mL of blood drawn for determination of hematocrit, before being placed under general anesthesia. Premedication protocols were determined by a board‐certified anesthesiologist (S. Kadotani) based on clinical assessment and cardiovascular status. Anesthesia was induced with alfaxalone 2 mg/kg IV to effect and maintained with isoflurane in 100% oxygen following intubation. Cats were monitored throughout the CMR using ECG, pulse oximetry, end‐tidal carbon dioxide, direct arterial blood pressure monitoring, and assessment of anesthetic depth, heart rate, respiratory rate, and temperature with values recorded every 5 minutes. Lactated Ringer's solution was administered at 5 mL/kg/hour during the anesthetic period in healthy cats and 2.5 mL/kg/hour in HCM affected cats.All cats underwent CMR studies performed on a MAGNETOM Skyra 3T scanner with a 4‐channel phased array flex coil . Scout images were used to identify the long‐ and short‐axis views of the left ventricle as well as the 2‐ and 4‐chamber views of the heart. Thereafter, cine‐images of 3 long‐axis views  were acquired using a balanced steady‐state precession sequence in combination with parallel imaging and retrospective gating during an expiratory breath‐hold. Frequency scout scans were performed before each cine image and optimal frequency was subjectively assessed and determined by the operator (RCF). Frequencies (−200 Hz to +200 Hz) were optimally adjusted before each cine loop based on the frequency scout.42, version 5.10, Circle Cardiovascular Imaging Inc, Calgary, Alberta, Canada). Four, manually drawn, regions of interest were used to create individual regional T1 values and ECV in both the basal and mid‐ventricular slice. The septum was divided into 2 regions, as was the free wall including the papillary muscles . Manual segmentation of the epicardial and endocardial borders of the LV in the short axis were outlined from the CMR derived images. Ejection fraction, end‐diastolic volume, end‐systolic volume, and mass were calculated by manually tracing the epicardial and endocardial contours of the LV in each phase from end‐diastole to end‐systole. End‐diastole was determined by visually selecting the phase with the largest LV volume and end‐systole was determined by visually selecting the phase with the smallest LV volume. Papillary muscles were included in the LV cavity and thus not counted towards LV mass. Segmental myocardial wall thickness was manually measured in end‐diastole on basal and mid‐chamber images. Left ventricular segments with LGE were qualitatively evaluated and enhancement was defined as 6 standard deviations above the manually selected normal area . Native and postcontrast MOLLI images were processed using commercially available software  and once by another investigator (J.P. Stack) each blinded to the other's results. Intra‐ and interobserver variability was determined by the coefficient of variation utilizing the root means squared method ([coefficient of variation] = 100 × ∑d/m2n2), where d is the difference between 2 paired measurements and m is the mean of the paired measurements. Statistical significance was defined for P values <.05. Receiver operating characteristic (ROC) analysis was performed to assess the diagnostic accuracy of native T1 time, ECV, and left ventricular mass to detect the presence of HCM. Diagnostic cutoffs for each variable were chosen on the basis of the highest of various combinations of sensitivity and specificity using Youden's index (Y = sensitivity + specificity − 1).Statistical analyses were performed using commercially available software . Continuous variables were expressed as mean ± SD when normally distributed, or median and range when the distribution was non‐normal. Normality was assessed using the Shapiro‐Wilk test. Groups were compared using unpaired Student's 3Demographic data and results of physical examination are summarized in Table r = 0.63, P = .01, LAd_LAX; r = 0.54, P = .04) and global radial and circumferential strain were significantly correlated with ECV .Within the healthy control group, no diastolic variables were significantly correlated with age, ECV, LV mass, or native T1 time. Linear measurements of the left ventricle and left atrium in diastole were significantly correlated with mass .Within the HCM group, there were significant correlations with multiple echocardiographic variables for both ECV and mass summarized in Table P < .001), ECV , and LV mass  provide outstanding discernment between healthy and HCM groups. Using a cutoff for native T1 of >1153 ms (Youden's Index = 80) provides a sensitivity of 92% and specificity 88%, whereas a cutoff for ECV of >28.1% (Youden's Index = 74) provides a sensitivity of 92% and specificity of 82%, and for LV mass a cutoff of >8.2 g (Youden's Index = 92) provides a sensitivity of 92% and specificity of 100%.Receiver operating characteristic results indicate native T1 time  are obtainable in cats, with acceptable repeatability, and are significantly different between healthy and HCM cats. In this study sample, HCM cats had increased native T1 times and ECV compared with normal cats, but only ECV was significantly correlated with diastolic function and left atrial size. Preclinical HCM cats had reduced GLPS compared with normal cats and this variable was not correlated with fibrosis.Based on CMR, HCM cats in this study sample have increased interstitial fibrosis compared with normal cats. Native T1 and ECV are highly correlated with histological measures of collagen and fibrosis in humans with a variety of cardiac diseases including HCM.The role of CMR in veterinary medicine is limited, but provides novel information about cardiac composition that cannot be determined from echocardiography. Although none of the cats in this study were in heart failure, there is reason to believe that diffuse fibrosis plays an important role in disease progression.Results of this study also demonstrated that ECV was correlated with multiple measures of diastolic function, LA size, and LA function irrespective of age, LV mass, IVSd, or LVFWd. Native T1 did not correlate with diastolic function and is likely related to the composite signal (cellular and extracellular) that determines native T1 time. The relationship between ECV and diastolic dysfunction occurs in people with clinical heart failure and asymptomatic HCM.Similar to other veterinary studies, despite clinically normal measures of global systolic function (LV FS), indices of systolic function measured by strain  support an overall decreased systolic function in cats with HCM.Our study had several limitations. This study included a small number of cats and further studies are warranted to determine the repeatability of these results. Additionally, the sample size of this study does not allow for the establishment of reference ranges and importantly, native T1 and ECV values should only be compared if they are obtained under similar conditions, including acquisition scheme, field strength, and processing approach. Future studies are needed to establish reference ranges for normal cats at the most common MRI field strengths 1.5T and 3T. We used echocardiography as the reference standard to determine if a cat was affected; however, it is still possible that some healthy cats are affected but have not progressed. Additionally, the preclinical HCM cats in this study were at most moderately affected and findings could differ in cats with more advanced HCM. In particularly, the relatively mild nature of the preclinical HCM could influence the distribution of fibrosis as well as the relationship between diastolic function and LV wall thickness. There were no significant differences with respect to the distribution of fibrosis based on CMR. On possible explanation for this finding could be related to the severity of HCM. Cats in this study were at most moderately affected and fibrosis could be more diffuse in the earlier stages of HCM. Additionally, the HCM affected cats in this study were considered to have symmetrical left ventricular hypertrophy, not allowing for comparison of regionally thicker areas of myocardium. The ROC results in this study are for detecting HCM based on the echocardiographic criteria, and it remains to be seen if CMR is more sensitive than echocardiography at discriminating between affected and unaffected cats in an equivocal range. Histopathology was not performed in this study, therefore even though ECV has been correlated with histopathology in multiple other species, we cannot definitely conclude that ECV has the same relationship in cats. Finally, correlations in this study do not equate to outcomes and prospective studies are warranted to determine the outcome relationship between ECV and HCM.In this study sample, cats with HCM had significantly higher ECV values compared with healthy controls and ECV significantly correlated with worsening diastolic function and left atrial size. Quantitative assessment of ECV is feasible in cats and can provide additional information not available using standard imaging techniques. Larger prospective studies are necessary to validate our findings and the effect of ECV on prognosis in cats with HCM requires further study.Authors declare no conflict of interest.Authors declare no off‐label use of antimicrobials.Approved by the IACUC of the University of Illinois at Urban‐Champaign, protocol #17281.Authors declare human ethics approval was not needed for this study.


The purpose of this study was to identify where ultrasmall superparamagnetic particles of iron oxide (USPIO) locate to in myocardium, develop a methodology that differentiates active macrophage uptake of USPIO from passive tissue distribution; and investigate myocardial inflammation in cardiovascular diseases.Myocardial inflammation is hypothesized to be a key pathophysiological mechanism of heart failure (HF), but human evidence is limited, partly because evaluation is challenging. USPIO-magnetic resonance imaging (MRI) potentially allows specific identification of myocardial inflammation but it remains unclear what the USPIO-MRI signal represents.Histological validation was performed using a murine acute myocardial infarction (MI) model. A multiparametric, multi-time-point MRI methodology was developed, which was applied in patients with acute MI (n = 12), chronic ischemic cardiomyopathy (n = 7), myocarditis (n = 6), dilated cardiomyopathy (n = 5), and chronic sarcoidosis (n = 5).USPIO were identified in myocardial macrophages and myocardial interstitium. R1 time-course reflected passive interstitial distribution whereas multi-time-point R2* was also sensitive to active macrophage uptake. R2*/R1 ratio provided a quantitative measurement of myocardial macrophage infiltration. R2* behavior and R2*/R1 ratio were higher in infarcted (p = 0.001) and remote (p = 0.033) myocardium in acute MI and in chronic ischemic cardiomyopathy , and were borderline higher in DCM (p = 0.096), in comparison to healthy controls, but were no different in myocarditis or sarcoidosis. An R2*/R1 threshold of 25 had a sensitivity and specificity of 90% and 83%, respectively, for detecting active USPIO uptake.USPIO are phagocytized by cardiac macrophages but are also passively present in myocardial interstitium. A multiparametric multi-time-point MRI methodology specifically identifies active myocardial macrophage infiltration. Persistent active macrophage infiltration is present in infarcted and remote myocardium in chronic ischemic cardiomyopathy, providing a substrate for HF.  Myocardial inflammation is widely hypothesized to be key driver of heart failure (HF) . PersistHowever, evaluation of myocardial inflammation in humans is challenging and, as a result, data to support the myocardial inflammation-HF hypothesis in humans are limited. Although circulating inflammatory markers are associated with incident HF, they are not specific to the myocardium . EndomyoUltrasmall superparamagnetic particles of iron oxide (USPIO), composed of an iron oxide core surrounded by a carbohydrate or polymer coating, passively cross the capillary barrier and appear to be phagocytosed by macrophages. The associated perturbation in magnetic field can be detected with MRI; thus, the method potentially allows identification of active immune cell tissue infiltration and, therefore, inflammation. USPIO-MRI has been applied in cardiovascular diseases; however, histological validation and methodological evaluation of the technique are limited, and as a result, it remains unclear what the USPIO-MRI signal represents , 9, 10.This study aimed to identify where USPIO locate to in myocardium, develop a methodology that differentiates active macrophage uptake of USPIO from passive tissue distribution, and apply the optimized method to investigate myocardial inflammation in a range of acute and chronic human cardiovascular conditions.This was a prospective research study. The study comprised 3 parts: 1) A preclinical histological validation study; 2) a human methodological study investigating and developing the USPIO-MRI methodology, which included comparison of R1 and R2* kinetics in active phagocytic cell-rich tissues and active phagocytic cell-poor tissues; and 3) a clinical study applying the optimized USPIO-MRI methodology to investigate myocardial inflammation in a range of acute and chronic cardiovascular conditions.An ethics committee of the UK National Research Ethics Service approved the clinical studies and written informed consent was obtained from all participants. The work was conducted according to the Helsinki Declaration.See the The study comprised healthy volunteers with no cardiovascular symptoms, no history of medical conditions, no drug allergies, and normal electrocardiogram. Standard cardiac MRI (cine and late gadolinium enhancement [LGE] imaging) performed as part of the study was also normal. Participants were age and sex matched to patients in the clinical study (see the following section).Participants underwent baseline blood tests  and MRI (details follow) followed by intravenous infusion of USPIO  in 0.9% saline. Participants underwent daily MRI for 4 days thereafter. MRI measurements from tissues rich with active phagocytic cells (spleen and liver) were compared with measurements from active phagocytic cell-poor tissues .1.Acute ST-segment elevation MI undergoing primary percutaneous coronary intervention, defined as per standard criteria.2.Chronic ischemic cardiomyopathy, defined as: established diagnosis per the clinical cardiology team, history of MI at least 10 months before study enrollment, MRI demonstrating an established infarct and LV ejection fraction <50%.3.Acute myocarditis, defined as: established diagnosis per the clinical cardiology team, acute hospital presentation in keeping with acute myocarditis, elevated serum troponin and C-reactive protein, and MRI typical of myocarditis (as reported by 2 independent experts), including the presence of nonischemic and the absence of ischemic myocardial LGE.4.DCM, defined as: established diagnosis as per the clinical cardiology team, MRI demonstrating LV ejection fraction <50% with global dysfunction, mid wall septal striae of LGE and no ischemic LGE.5.Sarcoidosis, defined as: an established multidisciplinary and histological diagnosis of pulmonary sarcoid. All patients also had nonischemic myocardial LGE on MRI. None were thought to have active cardiac sarcoid by their clinical teams.Consecutive consenting patients with the following conditions were recruited from Manchester University NHS Foundation Trust:2, any drug allergy, conditions associated with iron overload, significant liver disease, absolute erythrocytosis/polycythemia, hypotension, bacteremia, pregnancy, breast-feeding, atrial fibrillation, acute HF, and known critical left main stem stenosis/unstable angina.Exclusion criteria included contraindications to MRI, estimated glomerular filtration rate <50 ml/min/1.73 mParticipants underwent baseline blood tests and MRI followed by intravenous USPIO infusion. Participants underwent 2 post-USPIO MRI scans.MRI was performed at 1.5-T . The baseline MRI scan included standard long- and short-axis steady-state free precession cine imaging. T1 mapping (Modified Look-Locker Inversion Recovery) and T2* imaging (black blood multi-gradient-echo sequence) were acquired at the 4 most basal short-axis slice positions below the LV outflow tract, using the cines as reference, to cover basal and mid-myocardium. Dedicated liver and spleen T1 mapping and T2* imaging were also performed. Following an intravenous bolus of gadolinium contrast agent , LGE imaging, and repeat T1 mapping were performed (15 min postcontrast for the latter).USPIO were administered at the conclusion of the baseline MRI. Post-USPIO MRI included long- and short-axis cine imaging, T1 and T2* mapping at slice positions corresponding to those acquired at baseline. No immediate post-USPIO MRI was performed.LV volumes and mass were measured using CVI42 . T1 maps were generated in Siemens Argus . T2* maps were generated in MatLab v9.0 . Maps were transferred into Horos software  where endo and epicardial borders, and areas of LGE, were contoured. Two regions of interest were drawn on maps of the liver and spleen, avoiding vessels. Weighted mean voxel relaxation rates, including R1  and R2* (transverse magnetic resonance relaxation rate in the presence of static field inhomogeneities) were calculated for whole myocardium, and myocardium with and without LGE where relevant. Similarly, weighted mean voxel relaxation rates were calculated for liver and spleen. Myocardial ECV was calculated as described previously .t-tests  or nonparametric equivalents. The Student's t-tests or nonparametric equivalents were used to compare relaxation times at individual times points and generalized estimating equations, which adjusted for repeated measurements within each subject, were used to compare change in relaxation rates over time between groups. Correlation analysis was performed using Pearson or Spearman correlation as appropriate. Statistical significance was defined as p < 0.05. Analyses were performed using SPSS version 22 .Data distribution was determined using the Shapiro-Wilk test. Data were summarized using mean ± SD or median (interquartile range [IQR]), and compared using Student's See the Seven healthy subjects were recruited, but 1 was excluded following baseline MRI because of an incidental extracardiac finding. Six subjects completed the protocol. Three were male, mean age 45 ± 18 years. The 4 post-USPIO MRI scans were performed at 19 h (IQR: 16 to 20 h), 50 h (IQR: 43 to 54 h), 75 h (IQR: 69 to 78 h), and 93 h (IQR: 90 to 99 h) following USPIO. No subject experienced an adverse reaction.In myocardium, R2*  and R1  both incAs such, tissue R2* and R1 appeared to represent different phenomena following USPIO administration. The time-course of R1 reflected passive interstitial tissue distribution of USPIO, in keeping with the expected plasma elimination of USPIO, but was not sensitive to active phagocytic tissue accumulation. In contrast, although passive tissue distribution also affected R2*, R2* was sensitive to active tissue accumulation. The differences in R2* and R1 are illustrated most clearly in the spleen, a tissue rich with active phagocytic cells, where R2* remained substantially elevated at 75 and 93 h post-USPIO administration but R1 returned close to baseline . In compAs displayed in The ratio of R2* to R1 was calculated at each time point to provide quantitative assessment of active tissue USPIO accumulation while taking account of passive tissue distribution. R2*/R1 ratio was found to increase following USPIO administration in liver and spleen, whereas it decreased in myocardium . The difRaw R1, R2*, and R2*/R1 data are presented in Characteristics of patients in each disease group are presented in Twelve patients with acute ST-segment elevation MI were recruited but 2 were excluded: 1 because of a USPIO infusion failure and 1 developed an unrelated medical condition. The study therefore included 10 patients; in 5 patients, the LAD artery was the culprit MI artery and in 5 the right coronary artery was the culprit. Mean time between primary percutaneous coronary intervention and baseline MRI was 79 ± 22 h. For logistic reasons, 2 patients underwent 1 post-USPIO MRI only.On baseline MRI, native T1 and ECV were higher in infarcted myocardium, and were trending to be higher in remote myocardium, compared with healthy control myocardium. There were no differences in native T2*.R2* behavior over time was different (higher) in infarcted myocardium (p = 0.001), and in remote myocardium (p = 0.033), compared with healthy myocardium. Likewise, R2*/R1 ratio at 75 h was higher in infarcted myocardium (p = 0.041) and in remote myocardium (p = 0.032), compared with healthy myocardium at the same time point.Seven patients with chronic ischemic cardiomyopathy were recruited. Median time from MI to enrolment was 1.4 years (IQR: 1.1 to 11.5 years). Mean LV ejection fraction was 41 ± 5%. Four patients had an LAD territory infarct, 2 patients had a right coronary artery territory infarct and 1 patient had infarcts in both territories.On baseline MRI, native T1 and T2* were no different in infarcted or remote myocardium compared with healthy control myocardium. ECV was higher in infarcted myocardium compared with healthy control myocardium, but ECV in remote myocardium was not.R2* behavior over time was different (higher) in infarcted myocardium (p = 0.008), and in remote myocardium (p = 0.010), compared with healthy myocardium. R2*/R1 ratio at 75 h was higher in remote myocardium (p = 0.042) and trended toward being higher in infarcted myocardium (p = 0.095), compared with healthy myocardium at the same time point.Using the R2*/R1 ratio at 75 h post-USPIO in healthy myocardium as a reference, a threshold of 25 had a sensitivity and specificity of 90% and 83%, respectively, for detecting active USPIO uptake in infarcted and remote myocardium in acute MI and chronic ischemic cardiomyopathy .Central Six patients with acute myocarditis were recruited but 1 patient was excluded because their post-USPIO MRI could not be performed within the required time frame for logistical reasons. Mean time from admission to baseline MRI was 102 ± 52 h.On baseline MRI, all patients displayed myocardial nonischemic LGE. Regions displaying LGE had higher native T1 and ECV than healthy control myocardium (results not shown). There was a trend towards higher pan-myocardial native T1 and ECV compared with healthy myocardium. There were no differences in native T2*.Myocardial R2* behavior over time was no different in myocarditis (p = 0.461) compared with healthy myocardium. R2*/R1 ratio was also no different from healthy myocardium (p = 0.226); indeed, in contrast to the other groups, R2* and R2*/R1 ratio were lower than in healthy controls. Findings were the same when analysis was confined to myocardium displaying LGE (results not shown).Five patients with DCM were recruited. On baseline MRI, all patients displayed myocardial nonischemic LGE. Myocardial ECV was higher in DCM compared with healthy control myocardium and there was a trend toward higher native myocardial T1. There were no differences in native T2*. There was a trend toward a difference in myocardial R2* behavior over time (higher) compared with healthy myocardium (p = 0.096), but R2*/R1 ratio was no different to that in healthy myocardium (p = 0.259).Five patients with sarcoid were recruited. On baseline MRI, all patients displayed myocardial nonischemic LGE. Native myocardial T1 and T2* were no different compared with healthy control myocardium. Myocardial R2* behavior over time was no different in sarcoid compared with that in healthy myocardium (p = 0.265). R2*/R1 ratio was also no different (p = 0.304).There were no significant correlations between native myocardial T1 and post-USPIO R2* or R2*/R1 in the whole group or when the analysis was confined to the acute conditions  see .Our study has a number of novel findings.USPIO have been used in conjunction with MRI to identify tissue inflammation for a number of years but validation of the technique, including descriptions of the methods and findings, have been limited. Colocalization of USPIO  and macrophages has been demonstrated in vascular tissue and ex vivo ,10. StirMultiple previous studies, including large clinical trials , 8, 9, hMoreover, after examination of R2* and R1 behavior post-USPIO, we propose a new metric, R2*/R1 ratio, for identifying active myocardial inflammation. R1 is determined by short-range dipolar interactions. R2* is determined by local field gradients. Uniformly dissolved USPIO affect R1 and R2* relaxivity similarly. CompartFor future research, we propose a protocol that includes T1 and T2* mapping at baseline followed by USPIO administration and then repeat T1 and T2* mapping at 50 and 75 h post-USPIO. This will provide R2* behavior over time and R2*/R1 ratio, which, as demonstrated, provide complementary information. Nevertheless, given the effectiveness of R2*/R1 ratio for identifying active macrophage infiltration, it may be that only 1 post-USPIO scan, performed at 75 h, is necessary, which would have logistical and cost benefits.Through application of the optimized USPIO-MRI method, we demonstrate active inflammation in infarcted and remote myocardium following acute MI, and persistent active inflammation in infarcted and remote myocardium in chronic ischemic cardiomyopathy.Persistent myocardial inflammation is widely hypothesized as being a key driver of adverse LV remodeling and HF, although there is very little evidence for it in humans ,13. In pMacrophage infiltration in remote myocardium in the acute phase following MI has been demonstrated in animal models and human tissue ,17. IncrAlthough DCM is pathogenically diverse, myocardial immune activation and inflammation are thought to influence the progression of LV dysfunction and adverse outcome . InflammWe did not find evidence of active myocardial macrophage activity in patients with sarcoid, which was in keeping with their clinical status; although patients had pulmonary sarcoidosis and evidence of focal myocardial fibrosis, none was thought to have active cardiac sarcoid by their clinical teams. Future investigation should include patients with active cardiac sarcoid.In keeping with the recent findings of Stirrat et al. , we did Although ferumoxytol has been voluntarily withdrawn from European markets for commercial reasons, it remains available for clinical use elsewhere, including in the United States. Following earlier studies that included 1,164 patients in which the aggregate rate of anaphylaxis was 0.2%, the US Food and Drug Administration in 2015 included a boxed warning for ferumoxytol (Feraheme) highlighting potential fatal and serious hypersensitivity reactions including anaphylaxis, and administration rate was lowered from bolus to infusion. A postmarketing study that included 8,666 patients found the anaphylaxis rate to be only 0.02%, and a number of studies have shown the adverse event rate with ferumoxytol to be no different to that of other intravenous iron products ,19. A PuFollowing on from the observation in myocarditis, our results provide important insight into myocardial inflammation in general. Although the range of potential insults to the myocardium is wide , the response of the myocardium to injury has often been considered to be quite generic, including edema and immune cell infiltration . Our resOur findings regarding the differential effect of compartmentalized versus “free” iron on R1 may have implications for R1 (or T1) assessment of “native” myocardial iron. T1 has recently been advocated as an alternative to T2* for measuring myocardial and hepatic iron accumulation in conditions associated with iron overload. However, in these conditions, iron is deposited intra- as well as extracellularly; thus, T1 may not accurately reflect total iron levels .It was not possible to include preclinical imaging in the validation study. The number of patients with each condition included in the clinical study was small, although we were able to demonstrate significant results despite the small numbers.PerspectivesCOMPETENCY IN MEDICAL KNOWLEDGE: Myocardial inflammation is hypothesized to be a key pathophysiological mechanism of HF. A multiparametric multi-time-point USPIO-MRI methodology was developed to specifically identify active myocardial macrophage infiltration. Its application demonstrates persistent active macrophage infiltration in infarcted and remote myocardium in chronic ischemic cardiomyopathy.TRANSLATIONAL OUTLOOK: Investigation of the relationship between myocardial inflammation, adverse remodeling, and HF is required. The new USPIO-MRI technique provides the methodology to achieve this.This study confirms the utility of USPIO for identifying active cardiac macrophages but also shows that USPIO can be passively present in the myocardial interstitium, outside of phagocytic cells. A novel multi-time-point multiparametric MRI protocol is developed that specifically identifies active myocardial macrophage infiltration. Application of the new methodology uniquely demonstrates persistent active macrophage infiltration in infarcted and remote myocardium in human chronic ischemic cardiomyopathy, thus providing the first direct evidence in humans of a substrate for the widely held hypothesis that myocardial inflammation is a key driver of HF. The new USPIO-MRI methodology provides the opportunity to investigate the relationship between myocardial inflammation, adverse remodeling and HF in larger studies.Dr. Lagan is funded by a Clinical Research Training Fellowship from the British Heart Foundation (FS/17/47/32805). Dr. Karen Piper Hanley is funded by the Medical Research Council Grant (MR/P023541/1). Dr. Miller is funded by a Clinician Scientist Award (CS-2015-15-003) from the National Institute for Health Research. The work was also supported in part by a British Heart Foundation Accelerator award to The University of Manchester (AA/18/4/34221). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health. The authors recognize the support from AMAG Pharmaceuticals who provided the USPIO. AMAG Pharmaceuticals had no role in study design, data collection, analysis, interpretation or writing of the report. All other authorshave reported that they have no relationships relevant to the contents of this paper to disclose.