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Dual-chamber pacing for hypertrophic cardiomyopathy: a randomized, double-blind, crossover trial
R A Nishimura1, J M Trusty, D L Hayes
1Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.
Insights
Dual-chamber pacing (DDD) may improve symptoms and reduce left ventricular outflow tract gradient in hypertrophic obstructive cardiomyopathy. However, benefits vary, and a placebo effect may contribute to symptom relief.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Hypertrophic obstructive cardiomyopathy (HOCM) is a condition characterized by left ventricular outflow tract (LVOT) obstruction.
- Previous cohort studies suggested dual-chamber pacing (DDD) may alleviate symptoms and reduce LVOT gradient in HOCM patients.
- A randomized, double-blind trial comparing DDD pacing to standard therapy was lacking.
Purpose of the Study:
- To evaluate the efficacy of dual-chamber pacing (DDD) in patients with severe symptoms of hypertrophic obstructive cardiomyopathy (HOCM).
- To compare the effects of DDD pacing versus backup AAI pacing on symptoms, quality of life, and hemodynamic parameters.
Main Methods:
- A double-blind, randomized, crossover trial involving 21 patients with symptomatic HOCM.
- Patients underwent baseline assessments including quality of life, echocardiography, and exercise tests.
- Nineteen patients were randomized to 3 months of DDD pacing followed by 3 months of AAI pacing, or vice versa.
Main Results:
- DDD pacing significantly reduced LVOT gradient compared to baseline and AAI pacing (55 vs. 76 and 83 mm Hg, respectively; p < 0.05).
- Quality of life and exercise duration improved with DDD pacing but not significantly different from AAI pacing.
- Symptomatic improvement occurred in 63% of patients during DDD pacing, but 42% also improved during AAI pacing, suggesting a potential placebo effect.
Conclusions:
- Dual-chamber pacing may offer symptomatic relief and reduce LVOT gradient in HOCM patients.
- Symptomatic improvement can occur without significant hemodynamic benefit, indicating a possible placebo effect.
- Further long-term, large-scale randomized trials are needed to establish DDD pacing as a standard recommendation for HOCM.
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 implantation 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 were 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 AAI 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.