Lesion of the atrioventricular conduction system is a well known adverse effect of alcohol septal ablation (ASA) in patients with obstructive hypertrophic cardiomyopathy (HCM). We assessed the atrioventricular conduction at long-term follow-up after ASA.In patients with a pacemaker implanted for high-grade atrioventricular block after ASA, the atrioventricular conduction was assessed prospectively by ECGs and 48-h Holter recordings. In the remaining patients, the atrioventricular conduction was analysed retrospectively for comparison.A total of 24 (28%) of 87 patients with obstructive HCM without a pacemaker at baseline had a pacemaker implanted due to high-grade atrioventricular block after ASA. Ten of these patients were not available for follow-up. Holter recordings in the remaining 14 patients revealed normalized atrioventricular conduction in 6 patients 6.2 years (range 2.1-9.4) after ASA. Patients with high-grade atrioventricular block at follow-up had longer PR intervals at baseline [205 ms (200-230)] than the rest of the cohort [180 ms (140-200), P = 0.004] and a higher incidence of acute complete heart block (63 vs. 15%; P = 0.007) during ASA. A PR interval of at least 200 ms at baseline was associated with higher prevalence of high-grade atrioventricular block at follow-up (30 vs. 2%; P = 0.0013). The incidence of late-onset complete heart block was 1.5% per year after ASA.We found normalized atrioventricular conduction at long-term follow-up, suggesting recovery in 6 of 14 patients with a pacemaker implanted in relation to ASA. Permanent atrioventricular conduction abnormalities were associated with baseline PR intervals of at least 200 ms and acute persistent complete heart block during ASA.