Dual-chamber pacing for hypertrophic cardiomyopathy: A randomized, double-blind, crossover trial

Objectives. In a double blind, randomized, crossover trial we sought to evaluate the effect of dual-chamber pacing in patients with severe symptoms of hypertrophic obstructive cardiomyopathy. Background. Recently, several cohort trials showed that im plantation of a dual chamber pacemaker in patients with severely symptomatic hypertrophic obstructive cardiomyopathy can relieve symptoms and decrease the severity of the left ventricular outflow tract gradient. However, the outcome of dual-chamber pacing has not been compared with that of standard therapy in a randomized, double blind trial. Methods. Twenty-one patients with severely symptomatic hypertrophic obstructive cardiomyopathy were entered into this trial after baseline studies consisting of Minnesota quality-of-life assessment, two dimensional and Doppler echocardiography and cardiopulmonary exercise tests. Nineteen patients completed the protocol and underwent double blind randomization to either DDD pacing for 3 months followed by backup AAI pacing for 3 months, or the same study arms in reverse order. Results. Left ventricular outflow tract gradient decreased significantly to 55+/-38 mm Hg after DDD pacing compared with the baseline gradient of 76+/-61 mm Hg (p < 0.05) and the gradient of 83+/-59 mm Hg after AAI pacing (p < 0.05). Quality-of-life score and exercise duration mere significantly improved from the baseline state after the DDD arm but were not significantly different between the DDD arm and the backup AAI arm. Peak oxygen consumption did not significantly differ among the three periods. Overall, 63% of patients had symptomatic improvement during the DDD arm, but 42% also had symptomatic improvement during the AAT backup arm. In addition, 31% had no change and 5% had deterioration of symptoms during the DDD pacing arm. Conclusions. Dual chamber pacing may relieve symptoms and decrease gradient in patients with hypertrophic obstructive cardiomyopathy. In some patients, however, symptoms do not change or even become worse with dual-chamber pacing. Subjective symptomatic improvement can also occur from implantation of the pacemaker without its hemodynamic benefit, suggesting the role of a placebo effect. Long-term follow-up of a large number of patients in randomized trials is necessary before dual-chamber pacing can be recommended for all patients with severely symptomatic hypertrophic obstructive cardiomyopathy. (C) 1997 by the American College of Cardiology.