Electrophysiological Characteristics of Bundle Branch Reentry Ventricular Tachycardia in Patients Without Structural Heart Disease

Background: The distinct electrophysiological features of bundle branch reentry ventricular tachycardia (VT) in patients without structural heart disease have not been systemically characterized. Methods: Nine patients (mean age, 29.6 years) with normal left ventricular function were enrolled. Bundle branch reentry VT with right and left bundle branch block (BBB) patterns was induced in 1 and 9 patients, respectively. The right bundle was attempted to record by a 6F decapolar or quadripolar catheter. Electroanatomic mapping of the left ventricle was performed in 6 patients. In all left BBB pattern VT, the mean VT cycle length was 329.3±89.1 ms, and the median HV interval during tachycardia was longer than that of baseline (78 [73–100] versus 71 [64.5–88] ms; P =0.11). Results: The H-RB interval during VT was slightly shorter ( P =0.14); however, the median RB-V interval was markedly longer than that during sinus rhythm (50 [29.5–83] versus 30 [8–51] ms; P =0.043]. In 6 patients with 3-dimensional mapping of the left ventricle, a slow anterograde or retrograde conduction over left HIS-Purkinje system with normal myocardial voltage was identified. In addition, Purkinje-related VTs (1.0±1.3 types) were also induced in 5 patients. Ablation was applied in distal left BB in patients with baseline left BBB and in one narrow QRS patient with sustained Purkinje-related VT, whereas right BB was targeted in other patients. During a mean follow-up of 31.4 months, frequent premature ventricular contractions occurred in one patient, and new VT developed in the other patient. Conclusions: Bundle branch reentry VT can occur in young patients with extensive conduction disturbances within HIS-Purkinje system. Ablation targeting at the distal left BB which bifurcates into left posterior and anterior fascicle can preserve the residual atrioventricular conduction, but intensive follow-up is needed.