Lead aVR in ARVC: Rediscovering an Overlooked Signal

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is part of the spectrum of arrhythmogenic cardiomyopathies and is characterized by progressive replacement of the myocardium with fibrofatty tissue, often with epicardial predominance and variable biventricular involvement.1) ARVC presents with diverse phenotypes, reflecting not only its association with ventricular arrhythmias (VAs) and sudden cardiac death, but also heterogeneity in genetic background, disease expression, and temporal progression.Accordingly, predicting the risk of sudden cardiac death and identifying patients who may benefit from device therapy remain important clinical challenges in the management of ARVC.2) Prediction models for risk stratification in ARVC have advanced by incorporating demographic, electrocardiographic, Holter, and imaging variables.3) However, these models still have limitations because disease expression and, consequently, arrhythmic risk may change dynamically over time.4) Advanced imaging, ambulatory monitoring, genetic testing, and emerging artificial-intelligence-based electrocardiogram (ECG) tools 5) can provide complementary information, but their accessibility, cost, interpretability, and suitability for repeated assessment may vary.In this context, simple and readily available ECG markers that are mechanistically linked to the distribution of arrhythmogenic substrates may provide clinical insights into disease phenotyping.In the present issue, Lee and colleagues 6) report a retrospective single-center study evaluating whether QRS morphology in lead aVR can serve as an electrocardiographic marker of epicardial right ventricular outflow tract (RVOT) scar in patients with ARVC.The study included 45 patients who underwent catheter ablation for drug-refractory ventricular arrhythmias and received both endocardial and epicardial electroanatomic mapping.Lead aVR morphology was classified into QR, QS, and R patterns, and epicardial RVOT scar involvement was defined by a predefined segment-based criterion.The principal finding was that lead aVR morphology was associated with the regional distribution of right ventricular epicardial scar.Among patients with a QR pattern, an R/Q ratio <0.582 helped identify those with epicardial RVOT scar, suggesting potential guidance for pre-procedural planning.QS and R patterns were also associated with