Long-term Effect of Dual-chamber Pacing on Pressure Gradient at Left Ventricular Outflow Tract in Hypertrophic Obstructive Cardiomyopathy

A 60-year-old man with hypertrophic obstructive cardiomyopathy (HOCM) was implanted dual-chamber ICD for the purpose of both the left ventricular outflow tract (LVOT) gradient reduction by ventricular pacing and the primary prevention of ventricular tachyarrhythmia. Because the LVOT gradient reduction and improvement of symptoms by pacing were insufficient, however, a new pacing lead was inserted in the right ventricular apex at a different position 1.5 cm away from the site of the defibrillation lead, and the LVOT gradient greatly declined from 108 to 30 mmHg. This DDD pacing was continued over seven years. On this occasion, he was referred to our hospital because of battery depletion, and a cardiac catheterization study was performed after ICD replacement. The LVOT gradient was 10 mmHg in sinus rhythm. After administration of isoproterenol (0.02γ), the gradient was increased to 92 mmHg in sinus rhythm. DDD pacing using a newly placed ventricular pacing lead significantly decreased the gradient to 36 mmHg. This case study indicated that DDD pacing from a suitable location in the right ventricular apex caused a marked early reduction in the LVOT gradient, and at long-term follow up a further significant effect was obtained, also in sinus rhythm.