The risk of delayed atrioventricular and intraventricular conduction block following ablation of bundle branch reentry.

Background: The aim of the study was to determine the long-term reliability of atrioventricular and intraventricular conduction and the implications for cardiac resynchronization therapy (CRT-D) following catheter ablation of bundle branch reentry tachycardia (BBRT) and interfascicular tachycardia.

Methods And Results: Fourteen patients with recurrent monomorphic ventricular tachycardia (VT) (n = 11) and incessant VT (n = 3) underwent catheter ablation of BBRT (n = 7), interfascicular tachycardia (n = 5) or both arrhythmias (n = 2). Successful ablation was achieved in all patients without intraprocedural atrioventricular (AV) block. Within 2 months after ablation, three patients with BBRT and pre-existing prolonged QRS developed a delayed third-degree AV block. During the follow-up of 2 years, two patients with interfascicular tachycardia developed a new left bundle branch block (LBBB) associated with worsening of heart failure. Three patients underwent upgrading of implantable cardioverter defibrillator therapy to CRT-D early after ablation which improved heart failure during the 6 months follow-up. During the long-term follow-up of 39 ± 13 months, VT storm recurred in one patient. Four of the 14 patients died of deterioration of heart failure and one had to undergo heart transplantation.

Conclusions: Catheter ablation for BBRT in patients with prolonged QRS is associated with a high risk of delayed third-degree AV block. Ablation of interfascicular tachycardia can be associated with delayed LBBB. After ablation of bundle branch reentry, patients with prolonged QRS are candidates for cardiac resynchronization therapy but the mortality remains high.