Novel electrocardiogram and electrophysiological findings for differentiating idiopathic left posterior papillary muscle and left posterior fascicular ventricular arrhythmias

Differentiation between idiopathic left posterior fascicular ventricular arrhythmias (LPF-VAs) and posterior papillary muscle (PPM) VAs is of clinical value. This study aimed to develop an algorithm to distinguish PPM-VAs from LPF-VAs. This study enrolled 73 consecutive cases, including 31 with PPM-VAs and 42 with LPF-VAs, undergoing successful ablation by using 3D mapping and intracardiac echography to confirm the origin of the VAs. Electrocardiographic and electrophysiological parameters were compared between two groups. The 12-lead electrocardiography of the PPM-VAs was characterized by a longer QRS duration than that in LPF-VAs (154.4 ± 14.5 vs. 132.3 ± 13.1 ms, P  36 ms was recognized in 28/31 patients with PPM-VAs (90.3%) and 2/42 with LPF-VAs (4.8%). An algorithm incorporating a QRS duration of ≥133 ms with a conduction duration of a VA-RBB of >36 ms could yield a sensitivity of 90.3% and specificity of 100% for discriminating PPM-VAs from LPF-VAs. The novel algorithm incorporating a QRS duration of ≥133 ms with a conduction duration of the VA-RBB of >36 ms could be useful in differentiating PPM-VAs from LPF-VAs.