The V₁–V₃ transition index as a novel electrocardiographic criterion for differentiating left from right ventricular outflow tract ventricular arrhythmias

Purpose: The aim of this study was to develop a new electrocardiographic criterion for differentiating the origin of outflow tract ventricular arrhythmias (OT-VAs) with precordial transition in lead V₃. Methods: A total of 147 consecutive patients with OT-VAs displaying precordial transition in lead V₃ who underwent successful catheter ablation in the right ventricular outflow tract (RVOT) (n = 118) or left ventricular outflow tract (LVOT) (n = 29) were included in this study. The V₁–V₃ transition index was defined as the sum of S-wave amplitude in lead V₁ and V₂ during premature ventricular contractions (PVCs) divided by the S-wave amplitude during sinus rhythm (SR), respectively, minus the sum of R-wave amplitude in lead V₁, V₂, and V₃ during PVCs divided by the R-wave amplitude during SR, respectively, i.e., [(S_PVC/S_SR)V₁ + (S_PVC/S_SR)V₂] − [(R_PVC/R_SR) V₁ + (R_PVC/R_SR)V₂ + (R_PVC/R_SR)V₃]. Results: The V₁–V₃ transition index was significantly higher for RVOT origins than for LVOT origins (1.25 ± 2.48 vs. − 3.94 ± 3.11; P < 0.001). Receiver operating characteristic (ROC) analysis revealed an area under the curve (AUC) of 0.931 for the V₁–V₃ transition index, and a cutoff value of > − 1.60 predicted a RVOT origin with a 93% sensitivity and 86% specificity. With respect to AUC and accuracy, the V₁–V₃ transition index was superior to any previously proposed ECG indices for differentiating left from right OT-VAs. In 37 prospective cases, the new index was able to predict the site of a RVOT origin with 95% accuracy (35 of 37 cases). Conclusions: The V₁–V₃ transition index is a useful novel ECG criterion for distinguishing left from right OT-VAs with precordial transition in lead V₃.