ECG and anatomical features in patients of left coronary cusp ventricular arrhythmias with R wave in lead 1

Ventricular arrhythmias (VAs) originating from the coronary cusps with R wave in Lead 1 typically originate specifically from the right coronary cusp (RCC), but are occasionally of left coronary cusp (LCC) origin. Purpose: To identify distinguishing features of LCC-VAs exhibiting an R wave in Lead 1. Methods: We retrospectively analyzed patients who underwent successful initial catheter ablation for VA in either the LCC (N=41) or RCC (N=14). Twelve lead ECG during VA and during sinus rhythm were compared between LCC arrhythmia patients with an R wave in lead I during VA (R-wave group) and those without (non-R-wave group). In LCC cases in whom CT was available, we measured the anatomical axis of the left ventricle in the frontal plane. Results: Among the 41 LCC patients, 9 (22.0%) showed an R wave in lead I in contrast to 100% of the 18 RCC patients. CT imaging was available for 22 LCC patients (53.7%), and revealed a modest correlation between electrocardiographic and anatomical axis (r = 0.64, p = 0.0014). The R wave group had a significantly more leftward QRS axis during sinus rhythm (2.0 ± 29.6° vs 43.1 ± 31.1°, p = 0.001) and smaller anatomical axis on CT (14.4±16.46° vs 35.8±11.71°, p=0.004). ROC analysis showed that a QRS axis < 26° best predicted R wave presence in LCC patients. Conclusion: In cases of VA suspected to originate from the aortic cusps with R wave in lead I, presence of a leftward QRS axis during sinus rhythm suggests mapping should be extended to the LCC.