CENTRAL AND OBSTRUCTIVE SLEEP APNEA – A RISK FACTOR FOR PATIENTS WITH CONGESTIVE HEART FAILURE

CENTRAL AND OBSTRUCTIVE SLEEP APNEA – A RISK FACTOR FOR PATIENTS WITH CONGESTIVE HEART FAILURE

Central and Obstructive Sleep Apnea are very commonly underdiagnosed in the Congestive Heart Failure patients. Men are especially at a higher risk for Central Sleep Apnea as they have a less stable sleep architecture than women as well as a greater number of sleep–wake transitions and shorter slow-wave sleep, which makes them more susceptible to respiratory control system instability and central apneas. Patients with Congestive Heart Failure and Central Sleep Apnea are at a higher risk for death and cardiac transplantation.

Treatments specifically aimed at Obstructive Sleep Apnea and Central Sleep Apnea in patients with Congestive Heart Failure have shown to improve cardiovascular function and clinical status. For example, continuous positive airway pressurehas been shown to alleviate both Obstructive Sleep Apnea and Central Sleep Apnea along with improvements in left ventricular ejection fraction, decrease in urinary and plasma norepinephrine concentrations, and improved symptoms of heart failure. Oxygen also alleviates Central Sleep Apnea and reduces nocturnal urinary norepinephrine concentration.

The clinical characteristics of patients with Central Sleep Apnea appear to differ from those with Obstructive Sleep Apnea, probably reflecting important differences in the underlying pathophysiologies of these two breathing disorders. In a study of men with Congestive Heart Failure, it was found that those with Obstructive Sleep Apnea were heavier and were more prone to snoring than those with Central Sleep Apnea or no sleep apnea. Patients with Central Sleep Apnea, on the other hand, had a lower left ventricular ejection fraction. Hypocapnia has been found to be a chief risk factor for Central Sleep Apnea in both men and women. Increasing age is also an additional independent risk factor for Central Sleep Apnea along with atrial fibrillation which is a risk factor for sleep-disordered breathing in general but not for Obstructive Sleep Apnea.

Hypocapnia in Congestive Heart Failure appears to be related to the presence of high left ventricular filling pressures and pulmonary congestion which provoke hyperventilation through stimulation of pulmonary vagal irritant receptors. Atrial fibrillation is a marker for loss of atrial contraction and poorer cardiac pumping function and it can lead to a higher left ventricular filling pressure. Increasing age may play a role in increasing the risk for Central Sleep Apnea through similar mechanisms. Compared with younger Congestive Heart Failure patients, those who are older tend to have less compliant left ventricles with higher left ventricular filling pressures, as well as an increased prevalence of pulmonary venous hypertension. This may place them at a higher risk for nocturnal hyperventilation and Central Sleep Apnea.

These results are presented as reported by the Sleep Research Laboratory of the Toronto Rehabilitation Institute and the Departments of Medicine, The Toronto Hospital and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.