Effects of Short-Term Continuous Positive Airway Pressure on Myocardial Sympathetic Nerve Function and Energetics in Patients With Heart Failure and Obstructive Sleep Apnea A Randomized Study

Background-Heart failure with reduced ejection fraction and obstructive sleep apnea (OSA), 2 states of increased metabolic demand and sympathetic nervous system activation, often coexist. Continuous positive airway pressure (CPAP), which alleviates OSA, can improve ventricular function. It is unknown whether this is due to altered oxidative metabolism or presynaptic sympathetic nerve function. We hypothesized that short-term (6-8 weeks) CPAP in patients with OSA and heart failure with reduced ejection fraction would improve myocardial sympathetic nerve function and energetics. Methods and Results-Forty-five patients with OSA and heart failure with reduced ejection fraction (left ventricular ejection fraction 35.8 +/- 9.7% [mean +/- SD]) were evaluated with the use of echocardiography and C-11-acetate and C-11-hydroxyephedrine positron emission tomography before and approximate to 6 to 8 weeks after randomization to receive short-term CPAP (n= 22) or no CPAP (n= 23). Work metabolic index, an estimate of myocardial efficiency, was calculated as follows: (stroke volume indexxheart ratexsystolic blood pressure%K-mono), where K-mono is the monoexponential function fit to the myocardial C-11-acetate time-activity data, reflecting oxidative metabolism. Presynaptic sympathetic nerve function was measured with the use of the C-11-hydroxyephedrine retention index. CPAP significantly increased hydroxyephedrine retention versus no CPAP (Delta retention: +0.012 [0.002, 0.021] versus -0.006 [-0.013, 0.005] min(-1); P= 0.003). There was no significant change in work metabolic index between groups. However, in those with more severe OSA (apnea-hypopnea index >20 events per hour), CPAP significantly increased both work metabolic index and systolic blood pressure (P<0.05). Conclusions-In patients with heart failure with reduced ejection fraction and OSA, short-term CPAP increased hydroxyephedrine retention, indicating improved myocardial sympathetic nerve function, but overall did not affect energetics. In those with more severe OSA, CPAP may improve cardiac efficiency. Further outcome-based investigation of the consequences of CPAP is warranted.