V 3 R/V 7 Index

Background: Several algorithms have been proposed to predict the origin of outflow tract (OT) ventricular arrhythmias (VAs) using standard 12-lead ECG. However, the additive value of right precordial and posterior leads is unknown. Methods: Standard 12-lead ECG, right precordial leads ECG (V3 R, V4 R, V5 R) and posterior leads ECG (V7 , V8 , V9 ) were recorded and analyzed in a development cohort of consecutive patients undergoing OT-VAs ablation at a single center. These findings informed the development of a novel algorithm incorporating right precordial and posterior leads to discriminate between left ventricular OT (LVOT) and right ventricular OT (RVOT) foci. The performance of this novel algorithm which includes the V3 R/V7 index was prospectively tested in a validation cohort of consecutive patients undergoing OT-VA ablation at 4 centers and compared with published algorithms. The location of the foci was determined by the successful ablation site.Results: One hundred ninety-one patients were recruited, of which 94 formed the validation cohort (mean age of 45.7±15.6, 39% male, 79% RVOT foci). During OT-VAs, a QS pattern in lead V3 R and an S wave in lead V7 were exclusively recorded in RVOT and LVOT foci, respectively. The V3 R/V7 index of LVOT origin was significantly greater than that of RVOT (1.05±0.83 versus 0.28±0.23,P <0.001). The V3 R/V7 index ≥0.85 predicted an LVOT origin with 87% sensitivity and 96% specificity. In the prospective evaluation, when the V3 R/V7 index ≥0.85, an RVOT origin could be excluded with 98.6% accuracy. The area under the curve of V3 R/V7 index (0.954) was larger than that of previously reported ECG criteria, including V2 S/V3 R (0.896), V2 transition ratio (0.792), and transition zone index (0.666). This novel index was also accurate in both patients without obvious LVOT or RVOT origins and subgroups with cardiac rotation or lead V3 R/S transition.Conclusions: The V3 R/V7 index is a novel and accurate ECG criterion that predicts OT-VAs origin.