Effect of biventricular pacing on left ventricular outflow tract pressure gradient in a patient with hypertrophic cardiomyopathy and normal interventricular conduction.

We report a case of hypertrophic obstructive cardiomyopathy (HOCM) that was markedly improved by biventricular pacing. A 55-year-old woman with HOCM presented with palpitation and presyncope. Electrophysiologic study revealed an atrioventricular nodal reentrant tachycardia. After radiofrequency catheter ablation, a Mobitz type II atrioventricular block developed and a permanent pacemaker implantation was decided. Cardiac catheterization showed a left ventricular outflow tract (LVOT) gradient of 130 mmHg. Right dual-chamber and atrial-synchronous left ventricular epicardial pacing failed to reduce the gradient. After biventricular pacing, LVOT gradient decreased to 20 mmHg. Biventricular pacing may be an alternative therapy for patients with HOCM.