Left bundle branch–Purkinje system in patients with bundle branch reentrant tachycardia: Lessons from catheter ablation and electroanatomic mapping

The mechanism of bundle branch reentrant tachycardia has been described, and ablation of the right bundle branch (RBB) is a curative approach.The purpose of this study was to evaluate the left bundle branch (LBB)-Purkinje system during sinus rhythm and to test the feasibility of ablating the LBB in patients with bundle branch reentrant tachycardia.Thirteen consecutive male patients (age 62 +/- 12 years) with sustained bundle branch reentrant tachycardia were included in the study.Surface ECG before ablation showed left bundle branch block (LBBB) in 10 patients and a narrow QRS in 3 patients. Bundle branch reentrant tachycardia with LBBB morphology was inducible in all cases. Ablation of the RBB resulted in right bundle branch block (RBBB) on surface ECG in 8 of 9 patients and total AV block with preserved retrograde conduction over the LBB in 1 of 9 patients. In 4 patients with LBBB during sinus rhythm, electroanatomic mapping showed (1) absent conduction through the anterior fascicle of the LBB and (2) anterograde slow conduction through the posterior fascicle of the LBB with (3) left ventricular activation by transseptal conduction due to conduction block between the distal Purkinje and the local ventricle in 2 of 4 patients. The LBB was successfully ablated in these 4 patients. During mean follow-up of 48 +/- 29 months, 3 patients died, but bundle branch reentrant tachycardia did not recur in any patient.In patients with LBBB and bundle branch reentrant tachycardia, anterograde slow conduction over the LBB is present. Ablation of the LBB is feasible and may be an alternative approach for bundle branch reentrant tachycardia. Patients with normal heart and bundle branch reentrant tachycardia have a good prognosis and may not require further intervention.