Multiparametric cardiovascular magnetic resonance is associated with outcomes in pediatric heart transplant recipients

BACKGROUND: Multiparametric cardiovascular magnetic resonance (CMR) has an emerging role in non-invasive surveillance of pediatric heart transplant recipients (PHTR). Higher myocardial T2, higher extracellular volume fraction (ECV), and late gadolinium enhancement (LGE) have been associated with adverse clinical outcomes in adult heart transplant recipients. The purpose of this study was to investigate the prognostic value of CMR-derived T1 and T2 mapping, ECV, and LGE for clinical outcomes in PHTR. METHODS: We performed a single-center, retrospective chart review of consecutive, gadolinium-enhanced CMR studies in PHTR over a 7.5-year period, excluding follow-up studies. Standard CMR ventricular volume and function analysis, T1 mapping with ECV, T2 mapping, and LGE assessment were performed. The composite outcome included cardiac death, non-cardiac death, re-transplantation, and cardiac hospitalization. RESULTS: Among 113 PHTR, mean age was 13.0 ± 5.1 years, with 6.0 ± 4.0 years since transplant. The indication for CMR was surveillance in 79%. Mean native T1 was 1050 ± 48 ms, T2 49.2 ± 3.9 ms, and ECV 29.7 ± 4.5%. Left ventricular LGE was present in 37% (42/113) and right ventricular LGE in 3.5% (4/113). The mean follow-up time was 2.3 years and median was 1.4 years. Cardiac death occurred in 2% (2/113), re-transplantation in 4% (4/113), and cardiac hospitalization in 22% (25/113). Non-cardiac death did not occur. Using Kaplan-Meier analysis, high T1 (≥1061 ms), T2 (≥50.0 ms), and ECV (≥31.4%) were each associated with decreased freedom from the composite outcome in follow-up. In univariable Cox regression analyses, high T1 was associated with increased risk of the composite outcome (hazard ratios HR 4.0, 95% confidence interval CI 1.7-9.2, p = 0.001), as were high T2 (HR 2.8, 95% CI 1.1-7.1, p = 0.026), and high ECV (HR 3.5, 95% CI 1.5-8.1, p = 0.004). CONCLUSION: T1 and T2 mapping are associated with early differences in adverse cardiac events in PHTR. These data suggest a role for a multicenter study with a longer follow-up duration.