Value of a Posterior Electrocardiographic Lead for Localization of Ventricular Outflow Tract Arrhythmias: The V4/V8 Ratio

Abstract

Objectives This study sought to prospectively evaluate the value of a dedicated electrocardiographic posterior lead to create an anteroposterior ratio to localize premature ventricular complexes (PVCs) between the right ventricular outflow tract and left ventricular outflow tract for catheter ablation. Background The anteroposterior relationship between the right and left outflow tract has not been explored for electrocardiographic localization of ventricular arrhythmia. Methods Standard V5 and V6 leads were placed posteriorly and ablation was performed with activation mapping. The site of successful ablation was correlated with the ratio of the R-wave in V4 to the R-wave in V8. Normalization of the V4/V8 ratio to a V4/V8 index was achieved by dividing the V4/V8 ratio by sinus V4/V8. After determination of optimal cutoffs, comparison with V2 transition ratio and V2S/V3R was subsequently performed using receiver operating characteristic curves in a prospective validation cohort. Results A total of 134 patients underwent ablation of PVCs with 2 modified posterior leads. PVCs successfully ablated from the left side had a statistically significantly higher V4/V8 ratio compared with right-sided PVCs (11.7 ± 10.6 vs. 2.3 ± 2.4, p < 0.001). At a cutoff of >3, the V4/V8 ratio had a sensitivity of 88% with a specificity of 77% for left-sided locations. At a cutoff of >2.28, the V4/V8 index had a sensitivity of 67% with a specificity of 98%. In the prospective validation cohort (n = 40), the V4/V8 ratio exhibited the highest sensitivity of 75% with a negative predictive value of 89% compared with the V4/V8 index, V2 transition ratio, and V2S/V3R. The V4/V8 index had the highest specificity of 96% with positive predictive value of 89% compared to the other predictive ratios. When analyzing cases with a V3 transition, the V4/V8 index demonstrated 100% specificity and positive predictive value. Conclusions A simple modification of V5 to V8 posteriorly may provide incremental diagnostic value for localizing PVCs arising from the outflow tracts. Normalizing PVC localization criteria to the sinus rhythm results in the highest specificity when compared with other validated criteria.