Noninvasive detection of fibrofatty displacement in arrhythmogenic right ventricular cardiomyopathy detected by 3D cardiovascular magnetic resonance imaging

Background Arrhythmogenic right ventricular cardiomyopathy (ARVC) is diagnosed based on ESC-Guidelines 2023, Tissue differentiation using Cardiovascular Magnetic Resonance (CMR) is often based on 2020 Padua criteria (1). CMR using 3D Dixon late gadolinium enhancement (3D Dixon LGE) allows for a high-resolution simultaneous characterization and differentiation of myocardial fat and fibrosis in ARVC in both ventricles (2,3). Purpose To investigate the fibrofatty myocardial remodeling of the right and the left ventricle (LV/RV) using 3D Dixon LGE CMR imaging in ARVC. Methods Nineteen prospectively included patients undergoing CMR for suspected ARVC were characterized and classified as definite or borderline ARVC. The CMR protocol included cine imaging as well as tissue characterization by high-resolution isotropic 3D Dixon LGE (1.3 mm3) assessing both ventricles (Figure 1). 3D Dixon phenotypes were categorized into two groups: Group 1 non fibrofatty involvement (including: isolated fat infiltration, isolated scar, fat/scar in different anatomical locations, and phenotypes with no fat or scar) and Group 2 fibrofatty involvement in the same anatomical location. Overall Padua criteria burden was calculated by summing major criteria (weighted by 2) and minor criteria (weighted by 1). Due to the small sample size inherent to this rare disease, only descriptive statistics were performed (median and interquartile range [IQR]). Results Eleven Patients were diagnosed with definite ARVC and eight were classified with borderline ARVC. In total, six patients in the cohort had a positive genetic test for ARVC-associated pathogenic variants. Overall Padua criteria burden was higher in patients with definite ARVC compared to patients with borderline ARVC (Figure 2A and 2C). The definite ARVC patients showed lower RVEF compared to borderline ARVC patients. In the 3D Dixon LGE analysis fibrofatty involvement was associated with higher overall Padua criteria burden (median IQR vs median IQR). Moreover, patients with fibrofatty involvement showed lower RVEF than patients without fibrofatty involvement (Figure 2B and 2D). In contrast, isolated fat infiltration as well as isolated scar did not discriminate between definite and borderline ARVC patients in our cohort. Conclusion CMR based 3D Dixon-derived fibrofatty involvement reflects overall disease burden in ARVC as defined by the Padua criteria. Dixon-derived tissue characterization may provide complementary structural information reflecting disease severity in ARVC. Our findings support the usage of advanced tissue characterization methods for phenotype assessment in ARVC.