DUAL-CHAMBER PACING FOR HYPERTROPHIC CARDIOMYOPATHY - A RANDOMIZED, DOUBLE-BLIND, CROSSOVER TRIAL

Objectives. In a double blind, randomized, crossover trial we sought t o evaluate the effect of dual-chamber pacing in patients with severe s ymptoms of hypertrophic obstructive cardiomyopathy. Background. Recent ly, several cohort trials showed that im plantation of a dual chamber pacemaker in patients with severely symptomatic hypertrophic obstructi ve cardiomyopathy can relieve symptoms and decrease the severity of th e left ventricular outflow tract gradient. However, the outcome of dua l-chamber pacing has not been compared with that of standard therapy i n a randomized, double blind trial. Methods. Twenty-one patients with severely symptomatic hypertrophic obstructive cardiomyopathy were ente red into this trial after baseline studies consisting of Minnesota qua lity-of-life assessment, two dimensional and Doppler echocardiography and cardiopulmonary exercise tests. Nineteen patients completed the pr otocol and underwent double blind randomization to either DDD pacing f or 3 months followed by backup AAI pacing for 3 months, or the same st udy arms in reverse order. Results. Left ventricular outflow tract gra dient decreased significantly to 55+/-38 mm Hg after DDD pacing compar ed with the baseline gradient of 76+/-61 mm Hg (p < 0.05) and the grad ient of 83+/-59 mm Hg after AAI pacing (p < 0.05). Quality-of-life sco re 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 si gnificantly differ among the three periods. Overall, 63% of patients h ad symptomatic improvement during the DDD arm, but 42% also had sympto matic improvement during the AAT backup arm. In addition, 31% had no c hange and 5% had deterioration of symptoms during the DDD pacing arm. Conclusions. Dual chamber pacing may relieve symptoms and decrease gra dient in patients with hypertrophic obstructive cardiomyopathy. In som e 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, s uggesting the role of a placebo effect. Long-term follow-up of a large number of patients in randomized trials is necessary before dual-cham ber pacing can be recommended for all patients with severely symptomat ic hypertrophic obstructive cardiomyopathy. (C) 1997 by the American C ollege of Cardiology.