Fascicular ventricular tachycardia arising from the left side His and its adjacent region: a subset of upper septal idiopathic left ventricular tachycardia

Fascicular ventricle tachycardia (FVT) arising from the proximal aspect of left His-Purkinje system (HPS) has not been specially addressed. Current study was to investigate its clinical, electrocardiographic, and electrophysiological characteristics.Eighteen patients who were identified as this rare FVT were consecutively enrolled, and their scalar electrocardiogram and electrophysiological data were collected and analysed. The ventricular tachycardia (VT) morphology was similar to sinus rhythm (SR) in eight patients, left bundle branch block type in one patient, right bundle branch block type in seven patients, and both narrow and wide QRS type in two patients. During VT, right-sided His potential preceded the QRS with His-ventricle (H-V) interval of 36.3 ± 12.4 ms, which was shorter than that during SR (-51.4 ± 8.6 ms) (P = 0.002). The earliest Purkinje potentials (PPs) were recorded within 7 ± 3 mm of left-side His and preceded the QRS by 49.1 ± 14.0 ms. Mapping along the left anterior fascicle and left posterior fascicle revealed an antegrade activation sequence in all with no P1 potentials recorded. In the two patients with two VT morphologies, the earliest PP was documented at the same site, and the activation sequence of HPS remained antegrade. Ablation at the earliest PP successfully eliminated the tachycardia, except one patient who developed complete atrial-ventricular block and two patients who abandoned ablations. After at least 12 months follow-up, 15 patients were free from any recurrences.Fascicular ventricle tachycardia arising from the proximal aspect of left HPS was featured by recording slightly shorter H-V interval and absence of P1 potentials. Termination of VT requires ablation at the left-sided His or its adjacent region.