LAUSR

The Task Force Criteria (TFC) for ARVC are highly sensitive, but lack specificity. Patients with atypical RV-involvement (aRVi) may have different underlying aetiologies and prognosis, requiring specific therapeutic interventions. We aimed to evaluate the role of the baseline ECG for initial suspicion of aRVi. From the Netherlands Heart Institute Arrhythmogenic Cardiomyopathy (NHI-ACM) registry, patients were selected who 1) fulfilled TFC for definite ARVC, 2) presented with sustained VT, 3) underwent genetic testing. The first available ECG after VT was evaluated for AV-conduction and the presence and surface area (SA) of an R'-wave in V1-V3. ECGs with AV-conduction disturbances or an R'-wave with SA ≥1.65 mm2 were classified as suspicious for `atypical RV-involvement' (aRVi-ECG). Patients with ARVC-related pathogenic/likely pathogenic variant (P/LP+) were classified as “typical ARVC”. Data of patients without an ARVC-related pathogenic/likely pathogenic variant (P/LP−) were reviewed by an expert panel and classified as either “typical ARVC” or “suggestive for another aetiology” based on consensus. In total 124 P/LP+ patients and 35 P/LP− patients were included. Nineteen patients had an aRVi-ECG, which appeared significantly more predominant in the P/LP− group (11 (9%) P/LP+ vs. 8 (22%) P/LP−, p=0.019). Of the P/LP− patients, seventeen (49%) were classified as “suggestive for another aetiology” (e.g. myocarditis, ischemia, sarcoid), including all 8 patients with an aRVI-ECG. Among P/LP+ patients with an aRVi-ECG, 46% carried the Arg14del phospolamban variant and 64% died, versus 15% and 18% of P/LP+ patients without aRVi-ECG, respectively (Table 1). For patients presenting with sustained VT and fulfilling the TFC for ARVC diagnosis, a baseline ECG suggestive for atypical RV-involvement should raise suspicion for a different underlying aetiology in patients without an ARVC-related P/LP variant. In P/LP+ patients, an aRVi-ECG may identify those with poor outcome. Type of funding sources: None.