Treating sleep apnea may improve heart function in individuals with heart failure. The heart serves as a muscular pump to provide blood carrying oxygen to the entire body. It’s function can be measured by ejection fraction, a measure of the volume of blood pumped out (relative to the total blood in the ventricle). A normal ejection fraction is between 55% and 70%. In heart failure, muscles of the heart are weak or diseased leading to ejection fractions less than 55%. Positive airway pressure (PAP) may help.
By reducing the work load on the heart, PAP can increase ejection fraction and reduces the incidence of complications such as pulmonary edema. The benefit has been shown when used alone or together with heart failure medications like metoprolol.
Why is there a beneficial effect? With PAP positive pressure is spread throughout the thoracic cavity. The transmural pressure, or pressure across the wall of the left ventricle is thereby reduced, reducing the afterload or pressure working against cardiac output. As a result of afterload reduction, cardiac ejection fraction increases while cardiac effort decreases. The increase in intrathoracic pressure also results in better right heart function and can reduce the liklihood of pulmonary edema in heart failure. This is because less blood fills the left ventricle before it pumps. This reduction in LV preload translates into lower intrapulmonary blood volume and reduced right ventricular afterload. In summary, positive pressure treatment of sleep apnea in heart failure results in favorable pressure changes making heart function more efficient.
PAP treatment for heart failure patients with OSA remains a debated topic. The CanPAP trial, the original research on continuous-positive-airway pressure (CPAP) use in heart failure patients showed no benefit and possible harm to those treated. Further analysis demonstrated that half of patients benefited, but those who didn’t benefit from treatment could be harmed. Heart failure patients may exhibit predominantly central apnea rather than obstructive sleep apnea, which may qualify for different types of treatment than CPAP (i.e. BIPAP, ASV). Recent controversy also surrounds the use of adaptive servo-ventilation (ASV) in heart failure patients with central sleep apnea.
PAP treatment is important in patients with sleep apnea and heart failure. Individuals require accurate diagnosis with polysomnography to clarify whether apnea is predominantly central or obstructive in nature. This can guide choosing the right type of positive airway pressure. Once treatment is elected, follow up is also important to ensure a beneficial effect of positive airway pressure before committing to longer term treatment.
Johnson CB, Beanlands RS, Yoshinaga K, et al. Acute and chronic effects of continuous positive airway pressure therapy on left ventricular systolic and diastolic function in patients with obstructive sleep apnea and congestive heart failure. The Canadian Journal of Cardiology. 2008;24(9):697-704.
Phillips B, et al. Hypertension and Obstructive Sleep Apnea. Current Hypertension Reports. 2003;5:380–385.
The Effects of Continuous Positive Airway Pressure on Myocardial Energetics in Patients With Heart Failure and Obstructive Sleep Apnea. J Am Coll Cardiol. 2007 January 30; 49(4): 450–458. doi: 10.1016/j.jacc.2006.08.059