Cardiac transplantation is a lifesaving procedure for patients with end-stage heart failure. As acute rejection is a severe complication patients have to undergo invasive endomyocardial biopsy to rule out rejection episodes especially in the early phase after cardiac transplant.
This study is focused on comparing extracellular volume (ECV), T1 and T2 mapping via cardiac magnetic resonance imaging (CMR) with results endomyocardial biopsy at early post-transplant follow-ups to provide reference values for rejecting and non-rejecting patients.
Forty-five patients underwent endomyocardial biopsy three months after cardiac transplantation alongside CMR on a 1.5T system for evaluation of graft rejection and function. Left ventricular function (LVEF) was derived from short axis steady-state free precision (SSFP) sequences, myocardial ECV (%) was calculated using T1 pre- and postcontrast maps at three short axis slices using a 16-segment model. T2 maps were acquired from identical planes for edema assessment. CMR findings were compared with histology based on the guideline of the international society for heart and lung transplant (ISHLT).
Myocardial biopsy showed no signs of rejection (0A/0R) in thirty-nine patients and mild rejection (1A/1R) in six patients. Mean LVEF was normal in both groups (64.1% vs. 72.7%; p=.082). Mean ECV% (31.8% vs. 31.8%; p=.980), T1 in ms (1063.0 vs. 1079.1; p=.418) and T2 in ms (51.2 vs. 53.0; p=.137) did not differ significantly between patients with no or mild rejection.
In the reported patient cohort, there was no significant difference in the observed quantitative CMR markers in patients with mild vs. no transplant rejection, showing comparable pseudonormal values. The reported values may serve as reference values for CMR in the early stage after transplant. Further data from patients with higher rejection scores is needed to establish CMR as a screening tool for transplant rejection.