Effects of Dual-Chamber Pacing for Pediatric Patients With Hypertrophic Obstructive Cardiomyopathy

Objectives. The effects of both temporary and permanent dual-chamber pacing (DCP) were evaluated in symptomatic pediatric patients with hypertrophic obstructive cardiomyopathy (HOCM) unresponsive to medications. Background. Permanent DCP pacing can reduce left ventricular outflow tract (LVOT) gradient and relieve symptoms in adult patients with HOCM. Methods. Ten patients (mean [±SD] age 11.1 ± 6 years, range 1 to 17.5) with HOCM and Doppler LVOT gradient ≥40 mm Hg were studied. The seven patients showing hemodynamic improvement during temporary pacing at cardiac catheterization underwent surgical implantation of permanent DCP system. The effects of permanent pacing were evaluated using questionnaire, Doppler evaluation, treadmill testing and repeat cardiac catheterization. Results. At initial cardiac catheterization, three patients failed to respond to temporary pacing (inadequate pace capture in two; congenital mitral valve abnormality in one). The remaining seven patients (70%, 95% confidence interval 38.0% to 91.7%; mean age 13 ± years, range 4 to 17.5) showed significant reduction (p < 0.05) in LVOT gradient, left ventricular systolic pressure and pulmonary capillary wedge pressure. After pacemaker implantation, these seven patients reported significant reduction in dyspne on exertion and exercise intolerance. Serial Doppler evaluation showed significant reduction in LVOT gradient. Follow-up catheterization at 23 ± 4 months in six patients (one patient declined restudy) showed persistent decrease in LVOT gradient (53 ± 13 vs. 16 ± 11 mm Hg), left ventricular systolic pressure (149 ± 16 vs. 108 ± 14 mm Hg) and pulmonary capillary wedge pressure (18 ± 2 vs. 12 ± 4 mm Hg) versus preimplantation values. Conclusions. Permanent DCP is an effective therapy for selected pediatric patients with HOCM. Rapid atrial rates and intrinsic atrioventricular conduction, as well as congenital mitral valve abnormalities, may preclude effective pacing in certain patients.