[Long-term beneficial effect of dual chamber pacing in a patient with hypertrophic obstructive cardiomyopathy].

Dual chamber (DDD) pacing therapy was effective to reduce the left ventricular outflow tract pressure gradient for a long time in a patient with pharmacotherapy-resistant hypertrophic obstructive cardiomyopathy. A 52-year-old man with pharmacotherapy-resistant pressure gradient was treated by a DDD pacemaker implantation, because the pressure gradient was proved to be reduced (94-->16 mmHg) by transient DDD pacing with an atrioventricular delay of 50 msec. Hemodynamics and ventricular wall thickness were serially observed after the implantation for 2 years. The pressure gradient progressively decreased during the pacing period, at 4 months and 2 years follow-up, (10-->2 mmHg) and during the sinus rhythm period (60-->25 mmHg), and left ventricular ejection fraction and end-diastolic volume index were increased. Although the ventricular wall thickness remained constant, the systolic anterior motion of the mitral valve and A/E were reduced during the pacing period in the echocardiography. During the acute effect of DDD pacing, the pressure gradient reduction seemed to be related to dilatation of the left ventricular outflow tract induced by a change of contraction modality of the intraventricular septum. Improved left ventricular diastolic function may contribute to the pressure gradient reduction during extended periods of pacing therapy.