Updated quantitative thresholds for cardiac magnetic resonance imaging-based diagnosis of arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy associated with life-threatening ventricular arrhythmias. Currently, ARVC diagnosis is defined by the 2010 modified task force criteria. OBJECTIVE: This study aimed to evaluate the implementation of updated cardiac magnetic resonance (CMR) imaging thresholds used to define pathologic right ventricular (RV) dilation and systolic dysfunction in the diagnosis of ARVC. METHODS: This was a retrospective, observational cohort study that enrolled patients with ARVC with available quantitative CMR evaluated at the Johns Hopkins ARVC Center. Reclassification of RV diagnostic criteria was reevaluated using updated standards for RV structure and function. RESULTS: 430 patients with ARVC were enrolled. Mean age was 35.1 years, 47.7% were female, and 66.3% had pathogenic variants in ARVC-associated genes. Mean RV end-diastolic volume index was 114 mL/m2 (±39), and mean RV ejection fraction was 41% (±11%). Using updated standards, 18.3% of patients previously fulfilling major RV structure and function criteria were downgraded to minor criteria, and 10.5% were downgraded to no criteria fulfillment, whereas 35.0% patients fulfilling minor RV structure and function criteria were downgraded to no criteria fulfillment. 1 patient was downgraded to a borderline diagnosis, and 3 patients were downgraded to no ARVC diagnosis. 1 patient in whom ARVC diagnosis was reversed developed ventricular arrhythmia during follow-up, but had a clear alternative explanatory diagnosis of LMNA-related cardiomyopathy. CONCLUSION: Incorporation of modern standards for normal RV structure and function improved the specificity of the ARVC modified task force criteria without reducing sensitivity. These findings support the use of updated CMR-derived criteria for defining the presence or absence of pathologic RV phenotype during ARVC diagnostic evaluation.