His-LBB Twig: The Origin for Premature Ventricular Complexes With Morphology Almost Identical to Sinus Rhythm

Premature ventricular complexes with a QRS morphology almost identical to the sinus rhythm (PVC-iSR) are scarce and have been insufficiently investigated.

The purpose of this study was to explore the electrophysiology characteristics, true origin, and ablation strategy for PVC-iSR.

Among 3,804 patients referred for PVC ablation, 20 patients with PVC-iSR were identified. Detailed mapping, ablation, and analysis were performed.

The earliest activation site (EAS) of PVC-iSR consistently recorded a sharp Purkinje potential with a Purkinje-ventricular interval of 46.65 ± 4.43 milliseconds. By targeting the EAS of PVC-iSR, successful ablation was achieved without incurring atrioventricular block or bundle branch block in 17 of 20 cases. These findings indicate that PVC-iSR may originate from a discrete branch of the His bundle or proximal left bundle branch (LBB); we labeled this "His-LBB twig." His-LBB twig was located anterosuperior to the His-LBB trunk and underneath the right coronary cusp (RCC). The distance was 8.96 ± 2.32 mm between the EAS and left-sided His bundle, and 5.55 ± 2.31 mm between EAS and RCC. Ablation was successful in the RCC in 45%, beneath the RCC in 40%, and aborted for high risk of atrioventricular nodal injury in 15% of patients, with the distance between the EAS and RCC being shortest, moderate, and longest, respectively. The R/S index >1.0 in lead II was a good predictor of successful ablation in RCC.

PVC-iSR was caused by a His-LBB twig that could be successfully ablated in or underneath the RCC without injury to the conduction system.