Abnormal Myocardial Contractility After Pediatric Heart Transplantation by Cardiac MRI

Acute cellular rejection (ACR) compromises graft function after heart transplantation (HTX). The purpose of this study was to describe systolic myocardial deformation in pediatric HTX and to determine whether it is impaired during ACR. Eighteen combined cardiac magnetic resonance imaging (CMR)/endomyocardial biopsy (EMBx) examinations were performed in 14 HTX patients (11 male, age 13.9 ± 4.7 years; 1.2 ± 1.3 years after HTX). Biventricular function and left ventricular (LV) circumferential strain, rotation, and torsion by myocardial tagging CMR were compared to 11 controls as well as between patients with and without clinically significant ACR. HTX patients showed mildly reduced biventricular systolic function when compared to controls [LV ejection fraction (EF): 55 ± 8% vs. 61 ± 3, p = 0.02; right ventricular (RV) EF: 48 ± 7% vs. 53 ± 6, p = 0.04]. Indexed LV mass was mildly increased in HTX patients (67 ± 14 g/m² vs. 55 ± 13, p = 0.03). LV myocardial deformation indices were all significantly reduced, expressed by global circumferential strain (−13.5 ± 2.3% vs. −19.1 ± 1.1%, p < 0.01), basal strain (−13.7 ± 3.0% vs. −17.5 ± 2.4%, p < 0.01), mid-ventricular strain (−13.4 ± 2.7% vs. −19.3 ± 2.2%, p < 0.01), apical strain (−13.5 ± 2.8% vs. −19.9 ± 2.0%, p < 0.01), basal rotation (−2.0 ± 2.1° vs. −5.0 ± 2.0°, p < 0.01), and torsion (6.1 ± 1.7° vs. 7.8 ± 1.1°, p < 0.01). EMBx demonstrated ACR grade 0 R in 3 HTX cases, ACR grade 1 R in 11 HTX cases and ACR grade 2 R in 4 HTX cases. When comparing clinically non-significant ACR (grades 0–1 R vs. ACR 2 R), basal rotation, and apical rotation were worse in ACR 2 R patients (−1.4 ± 1.8° vs. −4.2 ± 1.4°, p = 0.01 and 10.2 ± 2.9° vs. 2.8 ± 1.9°, p < 0.01, respectively). Pediatric HTX recipients demonstrate reduced biventricular systolic function and decreased myocardial contractility. Myocardial deformation indices by CMR may serve as non-invasive markers of graft function and, perhaps, rejection in pediatric HTX patients.