OBJECTIVETo analyze the clinical features of patients with delayed third degree atrioventricular block after ethanol septal ablation for hypertrophic obstructive cardiomyopathy.

METHODThe clinical data of cases with delayed third degree atrioventricular block after septal ablation for hypertrophic obstructive cardiomyopathy at our hospital from 2000 to 2011 were collected.

RESULTFive out of 235 patients (2.1%) developed delayed third degree atrioventricular block. Delayed third atrioventricular block occurred at 32 h post ablation (28 - 120 h). Their average age is 46 (33 - 64) years old, there are 4 males and 1 female. Left ventricular outflow gradient before ablation was 70 - 100 mm Hg (1 mm Hg = 0.133 kPa). Intraprocedural third degree atrioventricular block occurred in 4 patients. The average injected dose of Ethanol was 1.8 (1.4 - 4.3) ml. Syncope occurred in 3 patients. Temporary pacemaker was reimplanted to all 5 patients and removed after an average of 8 d (3 - 18 d). All 5 patients were in normal sinus rhythms at discharge without the need of implanting permanent pacemaker. There was no syncope in these 5 patients after discharge during the telephone follow up for an average of 9 (1 - 72) months.

CONCLUSIONThe incidence of delayed third degree atrioventricular block after septal ablation is rare. Prolonged electrocardiography monitoring and prophylactic temporary pacemaker backup post ablation are necessary to detect this event and to prevent syncope related to delayed third degree atrioventricular block after septal ablation.