The V6R/V5R index, a novel ECG criterion, can identify idiopathic ventricular arrhythmias arising from the aortic cusp

Abstract

Abstract Background Idiopathic ventricular arrhythmias (VAs) with a left ventricular outflow tract (LVOT) origin often have dominant R waves (R wave amplitude>S wave amplitude) in the precordial leads (V1 through V6). Radiofrequency catheter ablation (RFCA) within the aortic cusp can eliminate LVOT-VAs. However, some require RFCA at the aorto-mitral continuity (AMC), the endocardium just below the LV summit, and/or mitral annulus for a cure. No ECG indices have been fully established to help differentiate between VAs that can be ablated from the aortic cusp and those that require ablation from other sites. Purpose The purpose of this study was to identify ECG indices useful in differentiating VAs with an aortic cusp origin from those from outside the cusp among the LVOT-VAs. Methods Among 200 patients in whom successful RFCA of idiopathic VAs was obtained at the OT, this study included 36 (totaling 37 premature ventricular complexes [PVCs]) who had dominant R waves in the precordial leads and an LVOT origin. According to the PVC origins, the PVCs were classified into 2 groups: 1) Cusp group (n=22); PVCs were successfully eliminated by RFCA within or just under the aortic cusp and 2) non-cusp group (n=15); PVCs were successfully ablated from the other LVOT sites described above or by a sequential unipolar ablation (combination of the cusp, AMC, and mitral annulus). The detailed PVC morphology was compared between the 2 groups. Results There was no significant difference in the ratio of the Q wave amplitude in aVL to aVR, V2 R/S amplitude ratio, V2 R/S duration index, V2 transition ratio, transition zone index, or V2S/V3R index between the 2 groups. However, the ratio of the R wave amplitude in V6 to V4 (V6R/V4R index) was significantly higher in the cusp group than in the non-cusp group (0.68±0.14 mV vs. 0.52±0.15 mV, p=0.002). The receiver operating characteristic curve demonstrated that a V6R/V4R index of >0.56 predicted the PVCs originated from the cusp with a sensitivity of 0.73 and specificity of 0.91 (area under the curve of 0.81). Conclusion The V6R/V4R index is a simple and useful ECG parameter and could distinguish PVCs with an aortic cusp origin from those originating from outside the cusp among the LVOT-VAs with a high accuracy.