Acute Predictors of Subacute Complete Heart Block After Alcohol Septal Ablation for Obstructive Hypertrophic Cardiomyopathy

Acute and subacute complete heart block (CHB) are sequelae of alcohol septal ablation (ASA) for obstructive hypertrophic cardiomyopathy. Temporary pacemakers are routinely placed at the time of ASA, but there are no widely accepted guidelines for their management. This study examined acute predictors of subacute CHB in 52 consecutive ASA procedures in 48 patients without preexisting permanent pacemakers. Acute CHB occurred during 32 ASA procedures (62%), with the return of atrioventricular conduction on the day of ASA in all cases. New intraventricular conduction defects (IVCDs) were noted after 32 procedures (62%); in 9 of these, there was new first-degree atrioventricular block as well. CHB recurred subacutely 36 ± 22 hours after 13 ASA procedures (25%). In 5 of these cases, there was absent or inconsistent ventricular escape rhythm. Subacute CHB did not occur in 9 cases without acute CHB during ASA or new IVCDs after ASA. Acute CHB during ASA, new IVCDs after ASA, and new first-degree atrioventricular block after ASA incrementally increased the risk for subacute CHB. In conclusion, patients with acute CHB during ASA or new IVCDs after ASA are at high risk for developing subacute CHB, sometimes without a reliable escape rhythm; these patients should therefore have temporary pacing support for ≥48 hours after ASA or the last occurrence of CHB. Patients without acute CHB during ASA or new IVCDs after ASA are at low risk for subacute CHB.