Background: Adverse fibrotic remodeling is detrimental to myocardial health and a reliable method for monitoring\nthe development of fibrotic remodeling may be desirable during the follow-up of patients after heart transplantation\n(HTx). Quantification of diffuse myocardial fibrosis with cardiovascular magnetic resonance (CMR) has been increasingly\napplied and validated histologically in adult patients with heart disease. However, comparisons of CMR findings with\nhistological fibrosis burden in children are lacking. This study aimed to compare native T1 times and extracellular\nvolume fraction (ECV) derived from CMR with the degree of collagen on endomyocardial biopsy (EmBx), and to\ninvestigate the association between myocardial fibrosis and clinical as well as functional markers in children after HTx.\nMethods: EmBx and CMR were performed on the same day. All specimens were stained with picrosirius red. The\ncollagen volume fraction (CVF) was calculated as ratio of stained collagen area to total myocardial area on EmBx.\nNative T1 values and ECV were measured by CMR on a mid-ventricular short axis slice, using a modified look-locker\ninversion recovery approach.\nResults: Twenty patients (9.9 Ã?± 6.2 years of age; 9 girls) after HTx were prospectively enrolled, at a median of 1.3 years\n(0.02ââ?¬â??12.6 years) post HTx, and compared to 24 controls (13.9 Ã?± 2.6 years of age; 12 girls). The mean histological CVF\nwas 10.0 Ã?± 3.4%. Septal native T1 times and ECV were higher in HTx patients compared to controls (1008 Ã?± 32 ms vs\n979 Ã?± 24 ms, p < 0.005 and 0.30 Ã?± 0.03 vs 0.22 Ã?± 0.03, p < 0.0001, respectively). CVF showed a moderate correlation with\nnative T1 (r = 0.53, p < 0.05) as well as ECV (r = 0.46, p < 0.05). Native T1 time, but not ECV and CVF, correlated with\nischemia time (r = 0.46, p < 0.05).\nConclusions: CMR-derived fibrosis markers correlate with histological degree of fibrosis on EmBx in children after HTx.\nFurther, native T1 times are associated with longer ischemia times.
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