Premature Ventricular Contractions From the Proximal Left Anterior Fascicle: Insight From the Electrophysiologic and Anatomic Parameters

INTRODUCTION: Premature ventricular contractions (PVCs) originating from the proximal left anterior fascicle (LAF) are rarely discussed. We aimed to describe the characteristics and ablation outcome of PVCs originating from the proximal LAF and propose a stepwise approach. METHOD AND RESULTS: From 2018 to 2024, 16 patients (nine males) with proximal LAF-PVCs who underwent ablation were enrolled, and their electrophysiological characteristics and procedural details were analyzed. The acute procedural outcomes were complete success, success with residual nonclinical PVCs, and partial success (decrease in clinical PVCs). The electrocardiographs of the PVCs showed a right bundle branch block with an inferior axis. In the initial ablation attempt, targeting the earliest left ventricular (LV) endocardial activation site eliminated clinical PVC in 14 patients. Nonclinical PVC occurred in seven patients. A second attempt from the right coronary cusp (RCC) was made in four patients (three nonclinical and one clinical PVC), which resulted in complete success. One patient (6.3%, partial success) had PVC recurrence. Sites with a successful ablation showed a significantly greater Fascicle-QRS[PVC] interval, Delta Fascicle-QRS[PVC-Sinus] interval, and more reverse fascicle potentials than other sites. Patients who underwent successful supra-RCC ablation had a shorter RCC-LV earliest activation site distance (EAS). CONCLUSION: This is the first study to investigate the dynamic electrogram property in LAF-PVC ablation. The Fascicle-PVC interval and reverse fascicle are useful for predicting acute ablation success. The RCC approach may be effective in cases with a short RCC-LV EAS distance. Nonclinical PVC morphology could be due to LAF block and might not affect the long-term outcome after careful mapping.