The precordial R′ wave: A novel discriminator between cardiac sarcoidosis and arrhythmogenic right ventricular cardiomyopathy in patients presenting with ventricular tachycardia

Background Cardiac sarcoidosis (CS) with right ventricular (RV) involvement can mimic arrhythmogenic right ventricular cardiomyopathy (ARVC). Histopathological differences may result in disease-specific RV activation patterns detectable on the 12-lead electrocardiogram. Dominant subepicardial scar in ARVC leads to delayed activation of areas with reduced voltages, translating into terminal activation delay and occasionally (epsilon) waves with a small amplitude. Conversely, patchy transmural RV scar in CS may lead to conduction block and therefore late activated areas with preserved voltages reflected as preserved R′ waves. Objective The purpose of this study was to evaluate the distinct terminal activation patterns in precordial leads V 1 through V 3 as a discriminator between CS and ARVC. Methods Thirteen patients with CS affecting the RV and 23 patients with gene-positive ARVC referred for ventricular tachycardia ablation were retrospectively included in a multicenter approach. A non–ventricular-paced 12-lead surface electrocardiogram was analyzed for the presence and the surface area of the R′ wave (any positive deflection from baseline after an S wave) in leads V 1 through V 3 . Results An R′ wave in leads V 1 through V 3 was present in all patients with CS compared to 11 (48%) patients with ARVC ( P = .002). An algorithm including a PR interval of ≥220 ms, the presence of an R′ wave, and the surface area of the maximum R′ wave in leads V 1 through V 3 of ≥1.65 mm 2 had 85% sensitivity and 96% specificity for diagnosing CS, validated in a second cohort (18 CS and 40 ARVC) with 83% sensitivity and 88% specificity. Conclusion An easily applicable algorithm including PR prolongation and the surface area of the maximum R′ wave in leads V 1 through V 3 of ≥1.65 mm 2 distinguishes CS from ARVC. This QRS terminal activation in precordial leads V 1 through V 3 may reflect disease-specific scar patterns.