AUTHOR=Zhao Lei , Li Ruibin , Zhang Jidong , Xie Ruiqin , Lu Jingchao , Liu Jinming , Miao Chenglong , Cui Wei 

TITLE=The R-S difference index: A new electrocardiographic method for differentiating idiopathic premature ventricular contractions originating from the left and right ventricular outflow tracts presenting a left bundle branch block pattern

JOURNAL=Frontiers in Physiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.1002926

DOI=10.3389/fphys.2022.1002926

ISSN=1664-042X

ABSTRACT=<p><bold>Introduction:</bold> Differentiating idiopathic premature ventricular contractions (PVCs) originating from the right and left ventricular outflow tracts with a left bundle branch block (LBBB) morphology is relevant to catheter ablation planning and important for lowering the risk of complications. This study established a novel electrocardiographic (ECG) criterion to discriminate PVCs originating from the septum of the right ventricular outflow tract (s-RVOT) and those originating from the aortic sinus cusp of the left ventricular outflow tract (LVOT-ASC).</p><p><bold>Methods:</bold> A total of 259 patients with idiopathic PVCs originating from ventricular outflow tract with a LBBB pattern who underwent successful catheter ablation were retrospectively included. Among them, the PVCs originated from the s-RVOT in 183 patients and from the LVOT-ASC in 76 patients. The surface ECGs of the PVCs and sinus beats were analyzed using an electronic caliper. The R-S difference index in the precordial leads was calculated as V2R + V3R + V4R − V1S.</p><p><bold>Results:</bold> PVCs originating from both the s-RVOT and LVOT-ASC displayed an inferior axis (dominant R waves in leads II, III, and aVF). Compared with the s-RVOT group, the R-wave amplitudes on leads II, III, and aVF were significantly larger in the LVOT-ASC group (<italic>p</italic> &lt; 0.001, <italic>p</italic> &lt; 0.003, and <italic>p</italic> &lt; 0.001, respectively). Compared to the LVOT-ASC group, the s-RVOT group showed smaller R-wave amplitudes on leads V1–V6 (<italic>p</italic> = 0.021, <italic>p</italic> &lt; 0.001, <italic>p</italic> &lt; 0.001, <italic>p</italic> &lt; 0.001, <italic>p</italic> &lt; 0.001, and <italic>p</italic> &lt; 0.001, respectively) and larger S-wave amplitudes on leads V1–V3 (<italic>p</italic> &lt; 0.001, <italic>p</italic> &lt; 0.001, and <italic>p</italic> &lt; 0.001, respectively). Lead V3 was the most common transitional lead in both groups. Analysis of the receiver operating characteristic curve showed that the R-wave amplitude on lead V3 had the largest area under the curve (AUC) of 0.856 followed by the R-wave amplitudes on leads V4 (0.834) and V2 (0.806). The AUC of the R-S difference index was 0.867. An R-S difference index greater than 20.9 predicted an LVOT-ASC origin with 73.7% sensitivity and 86.3% specificity. This index is superior to previous criteria in differentiating PVCs with LBBB morphology and inferior axis originating from s-RVOT vs. LVOT-ASC.</p><p><bold>Conclusions:</bold> The R-S difference index in precordial leads is a useful new ECG criterion for distinguishing LVOT-PVCs from RVOT-PVCs with LBBB morphology.</p>