Abstract 4125497: Diagnostic Discrepancies Revealed by Explant Pathology at the Time of Cardiac Transplant in Patients Clinically Diagnosed with Nonischemic Cardiomyopathy: Role of Cardiac Magnetic Resonance Imaging

Background: Differentiating between causes of non-ischemic cardiomyopathy is important for disease-directed treatment. Cardiac MRI (CMR) and the use of late gadolinium enhancement (LGE) have proven useful for enhancing diagnostic accuracy. Definitive assessment of cardiomyopathy etiology by explant pathology facilitates direct evaluation of CMR utility. Hypothesis: We hypothesized direct comparison between pre-transplant (Tx) CMR and explant pathology will improve the characterization of undifferentiated cardiomyopathy through examination of cases where pre- and post-Tx diagnoses were discordant. Aims: To evaluate discrepant cases to describe imaging patterns in relation to post-Tx diagnosis. Methods: Institutional Tx recipients between 2000 and June 2023 were queried for pre-Tx MRI (n=122). Discrepant cases were identified (n=8). Pre-Tx diagnostic modalities, including CMR, were reviewed, and CMR patterns were evaluated in association with ultimate explant diagnosis. Results: Of the eight patients with discrepant diagnoses, five carried clinical diagnosis of dilated cardiomyopathy, one hypertrophic cardiomyopathy, one peripartum cardiomyopathy, and one congenital heart disease having undergone tricuspid valve and ASD repair. Pathologic evaluation most frequently identified biventricular or left ventricular arrhythmogenic cardiomyopathy (ARVC) (n=6), where CMR disclosed a diffuse pattern of subepicardial LGE and pre-Tx diagnosis of DCM was most common. Two of these pathologic descriptions represented a different disease on genetic evaluation: one patient had Danon disease, another had a LMNA pathogenic variant. The presumed peripartum cardiomyopathy was identified as Fabry’s disease on pathology (however, genetic testing consistent with Danon disease). Both Danon disease patients had primarily subendocardial LGE on CMR. One patient with a DCM phenotype had HCM pathologically. Results summarized in Table 1. Conclusions: Cardiac MRI can be a useful modality for the evaluation of underlying cardiomyopathy and should prompt appropriate genetic testing. Diffuse subepicardial LGE frequently accompanied the diagnosis of ARVC whereas a non-subepicardial pattern reflected alternative etiologies identified only through genetic testing.