Rare association of hypertrophic cardiomyopathy and complete atrioventricular block with prompt disappearance of outflow gradient after DDD pacing.

Although arrhythmias are common in hypertrophic cardiomyopathy (HCM), complete atrioventricular (AV) block is very unusual. A 27-year-old female presented with a recent history of syncope and exercise intolerance. ECG demonstrated complete AV block. Two-dimensional Doppler echocardiography revealed HCM with a 60 mmHg left ventricular outflow tract (LVOT) gradient. A temporary transvenous ventricular pacemaker was inserted urgently, and subsequently replaced by a permanent DDD pacemaker. All symptoms were eliminated. This symptomatic improvement was associated with complete disappearance of LVOT gradient at the time of implantation. No gradient was observed during early follow-up and at 6 months after DDD pacemaker implantation.