Time to first nadir of the QRS complex in aVR/time to first nadir of the QRS complex in aVL: A novel method for distinguishing left from right outflow tract premature ventricular complexes (PVCs) with precordial transition in V3

Background: The aim of the present study was to investigate the value of 'time to first nadir of the QRS complex in aVR/time to first nadir of the QRS complex in aVL' for distinguishing left vs. right outflow tract premature ventricular complexes (PVCs) with precordial transition in lead V3.

Methods: Data from 88 eligible consecutive patients (39 males; 48.3 ± 13.4 years of age) who had undergone ablation due to outflow tract PVCs that had transition in V3 were retrospectively evaluated and used in the analysis.

Results: Fifty-one patients (57.9 %) had PVCs with a left ventricular outflow tract (LVOT) origin, and 37 (42.1 %) patients had PVCs with a right ventricular outflow tract (RVOT) origin. There were significant differences between the LVOT and RVOT PVC groups in terms of the V2S/V3R index (0.97 ± 0.70 vs. 1.96 ± 0.80, p < 0.001), V1-V3 transition index (-2.6 ± 4.4 vs. -0.4 ± 4.6, p = 0.026), and 'aVR/aVL time to first nadir of the QRS complex' (0.94 ± 0.15 vs. 1.1 ± 0.2, p = 0.001). ROC curve analysis revealed that a 'aVR/aVL time to first nadir of the QRS complex ratio' greater than 0.98 predicted the RVOT origin, with 67.6 % sensitivity and 62.7 % specificity. A V1-V3 transition index > - 1.21 predicted an RVOT origin with 75.7 % sensitivity and 72.5 % specificity. A V₂S/V₃R index <1.4 predicted the origin of the LVOT, with a sensitivity of 78.4 % and a specificity of 80.4 %.

Conclusion: Although less precise than other established ECG criteria, the novel parameter 'time to first nadir of the QRS complex in aVR/aVL' was able to aid in the differentiation of LVOT vs. RVOT PVCs with V3 precordial transition in our study. Based on this finding, it may be suggested that if an OT PVC has an earlier negative QRS peak on aVL compared with aVR, the probability of it being the RVOT origin is high. This simple observation might aid the preprocedural planning of OT PVC ablation in clinical practice.