Idiopathic dilated cardiomyopathy (IDCM), which is characterized by cardiac enlargement and impaired systolic function of one or both ventricles, has an age-adjusted prevalence of 36 cases per 100,000 population and accounts for 10,000 deaths annually in the United States. This condition is an important cause of
Nocturnal treatment of sleep apnea by continuous positive airway pressure (CPAP) in individuals with congestive heart failure not only alleviates sleep-disordered breathing but also improves LV function, ameliorates the symptoms of heart failure, and reduces sympathetic activation by decreasing the secretion of norepinephrine. However, the increased effort required to complete expiration against the applied pressure often results in a sensation of dyspnea in individuals treated with CPAP. The Canadian Continuous Positive Airway Pressure for Patients with Central Sleep Apnea and Heart Failure (CANPAP) trial showed that CPAP attenuates central sleep apnea and improves cardiovascular function in patients with heart failure, but it did not demonstrate any beneficial effect of CPAP on survival. Ventilation by bilevel positive airway pressure (BPAP) almost completely abolished Cheyne-Stokes respiration in patients with congestive heart failure, suggesting that this approach is a noninvasive option for treatment of such patients. BPAP with room air for 1 h was also found to reduce systemic vascular resistance, reflecting cardiac afterload, as well as systolic BP and heart rate in patients with congestive heart failure, indicating that the reduction in LV transmural pressure during inspiration and expiration induced by this approach might alleviate congestive heart failure. BPAP was thus proposed to have excellent potential for improving LV performance. The long-term effects of treatment with BPAP on cardiac function and its mechanisms of action have not been systematically evaluated, however, in patients with IDCM. We have now performed a randomized prospective controlled trial to determine whether BPAP might improve LV function during daytime wakefulness and survival in ambulatory patients with IDCM and central sleep apnea-hypopnea.
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