Background: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) carries risk of sudden death. We hypothesize that the S-wave angle differentiates ARVD/C with otherwise normal electrocardiograms from controls. Materials and methods: All patients met Task Force 2010 definite ARVD/C criteria. ARVD/C patients without Task Force depolarization/repolarization criteria (-ECG) were compared to controls. Electrocardiogram measures of QRS duration, corrected QT interval, and measured angle between the upslope and downslope of the S-wave in V2, were assessed. Results: Definite ARVD/C was present in 155 patients (42.7 +/- 17.3 years, 68.4%male). -ECG ARVD/C patients (66 patients) were compared to 66 control patients (41.8 +/- 17.6 years, 65.2%male). Only the S-wave angle differentiated -ECG ARVD/C patients from controls (amp;lt;0.001) with AU the ROC curve of 0.77 (95%Cl 0.53 to 0.71) and odds ratio of 28.3 (95%Cl 6.4 to 125.5). Conclusion: ARVD/C may lead to development of subtle ECG abnormalities distinguishable using the S-wave angle prior to development of 2010 Taskforce ECG criteria. (C) 2018 Elsevier Inc. All rights reserved.