Cardiac Magnetic Resonance Imaging in Pediatric Heart Transplant Recipients: Correlation with Cardiopulmonary...

Multiparametric cardiac magnetic resonance (CMR) is increasingly used for rejection and coronary artery vasculopathy (CAV) surveillance in pediatric heart transplant recipients (PHTR). There is limited data regarding how graft assessment by multiparametric CMR may reflect functional capacity in PHTR. To explore the relationship between multiparametric CMR and markers of exercise capacity in PHTR. PHTR who underwent CMR within 1 year of cardiopulmonary exercise testing (CPET) were retrospectively reviewed. Those with submaximal effort on CPET (respiratory exchange ratio < 1.10), depressed function (left ventricular ejection fraction (LVEF) < 50% and/or right ventricular ejection fraction (RVEF) < 45%), or significant clinical events (rejection, new or worsening CAV, cardiac hospitalizations) between CMR and CPET were excluded. CMR variables included biventricular volumes, ejection fraction, cardiac index (CI), myocardial T2, T1/extracellular volume fraction (ECV), and myocardial perfusion reserve index (MPRI). CPET variables were VO_2peak, O₂ pulse, percent age-predicted maximum heart rate (APMHR), HR reserve, and exercise duration. Relationships between variables were studied using correlations and regression. Forty-seven PHTR were included. Time between CPET and CMR was 5.5 ± 3.4 months. CI correlated positively with O₂ pulse (R = 0.642, p < 0.001). Global T1 correlated negatively with both APMHR (R = - 0.538, p < 0.001) and HR reserve (R = - 0.598, p < 0.001). Global T2 correlated negatively with APMHR (R = - 0.335, p = 0.049), HR reserve (R = - 0.488, p = 0.003), and VO_2peak (R = - 0.327, p = 0.045). In PHTR with normal LV function, CMR-derived tissue characteristics have correlations with exercise capacity. Larger studies are needed to understand the role of multiparametric CMR in the functional surveillance of PHTR.