Terminal S‐Wave Amplitude in Lead V 2 With Monophasic R Waves in Other Precordial Leads: A Novel ECG Marker for Predicting Acute Successful Endocardial Ablation of a Subtype of Left Ventricular Outflow Tract Idiopathic Ventricular Arrhythmias

ABSTRACT Background An electrocardiographic (ECG) pattern—terminal s‐wave in lead V 2 with monophasic R waves in other precordial leads—may help identify a subset of left ventricular outflow tract (LVOT) idiopathic ventricular arrhythmias (IVAs) amenable to acute successful endocardial ablation. However, further clinical validation is needed. Methods This retrospective study included 93 patients with LVOT IVAs displaying the defined ECG pattern. Results Acute successful endocardial ablation was achieved in 70 patients (75.3%; successful endocardial ablation group), while the remaining 23 patients (24.7%; endocardial ablation failure group) required epicardial ablation or had unsuccessful outcomes. The s‐wave amplitude in lead V 2 was significantly deeper in the successful than in the failure group (5.0 ± 2.6 vs. 2.1 ± 1.1 mV, p = 0.000). In the successful group, the most common effective ablation sites were the left/right coronary sinus (LCC/RCC) commissure subvalvularly (52 patients, 55.9%) and anterior mitral annulus near the aorto‐mitral continuity (AMC) (18 patients, 19.4%). In the failure group, success was achieved via the coronary venous system (11 patients), combined endo‐epicardial ablation (3 patients), percutaneous epicardial access or surgical epicardial ablation (3 patients); one procedure failed due to proximity to the left main coronary artery, and 5 patients declined epicardial ablation. Conclusions Among patients with this ECG phenotype, approximately 75% can be successfully ablated endocardially at the LCC/RCC commissure subvalvularly or the anterior mitral annulus near the AMC. Greater terminal S‐wave amplitude in lead V 2 is associated with an increased likelihood of acute endocardial ablation success.