Alcohol-induced right bundle branch block is associated with a benign outcome in HOCM after alcohol septum ablation (ASA)

Introduction: Alcohol septum ablation (ASA) is a treatment option for hypertrophic obstructive cardiomyopathy (HOCM). We examined the impact of ASA-induced bundle branch block (BBB) on clinical and hemodynamic features.

Methods and results: We retrospectively analysed 98 HOCM patients with regard to ASA-induced BBB. Clinical examination was performed at baseline, early after ASA and at chronic follow-up (FU). ASA reduced left ventricular outflow tract gradient (LVOTG) during chronic FU (69.2 ± 41.6 pre vs. 31.8 ± 30.3 mmHg post ASA; p < 0.05) and interventricular septal diameter (21.7 ± 3.4 pre vs. 18.7 ± 5.0 mm post ASA; p < 0.05). ASA-induced early right BBB (RBBB) until discharge was observed in 44.9% and chronic RBBB at FU in 32.7%. Left BBB (LBBB) occurred in 13.3% early after ASA and in only 4.1% at chronic FU. Chronic RBBB was associated with more pronounced exercise-induced LVOTG reduction (102.1 ± 55.2 with vs. 73.6 ± 60.0 mmHg without; p < 0.05). 6-min-walk-test (6-MWT) and NYHA class were not affected by RBBB. LBBB had no influence on LVOTG, 6-MWT and symptoms. More ethanol was injected in patients with early RBBB (1.1 ± 0.4 vs. 0.8 ± 0.3 ml without; p < 0.05), who also showed higher mean CK release (827 ± 341 vs. 583 ± 279 U/l without; p < 0.05). Pacemaker implantation during FU was necessary in 11.5% of patients with early RBBB, 3.1% with chronic RBBB, 7.7% with early LBBB and 0% with chronic LBBB (p = n.s. for BBB vs. no BBB).

Conclusion: ASA-induced RBBB is associated with a higher volume of infused ethanol and higher maximum CK release. RBBB does not adversely affect the clinical outcome or need for pacemaker implantation but was associated with higher exercise-induced LVOTG reduction during chronic FU.