The electrocardiogram (ECG) provides important information to aid in the diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D). The ECG changes may be explained by the pathophysiology of the disease. The proximity of the right ventricle (RV) to the anterior chest leads (V(1) to V(4)) explains why the characteristic ECG abnormalities are most prominent in those lends. The specific ECG abnormalities reflect the pathophysiology of the disease including T-wave inversion due to scarring of the free wall of the RV, prolonged S-wave duration due to slow depolarization of the terminal part of the QRS because the RV is the last part of the heart to undergo depolatization, and epsilon waves due to slow conduction in the RV. The extent of ECG abnormalities correlate with the degree of structural change in the RV.