Cincinnati, OH - Another study has found that people with heart failure and sleep apnea face higher risks of dying than do heart-failure patients without sleep disordered breathing [1]. Researchers writing in the May 22, 2007 issue of the Journal of the American College of Cardiology say the study results show HF patients without sleep apnea may live twice as long as those who also have significant central sleep apnea.

In the same journal last month [2], Toronto researchers reported that 164 patients with systolic heart failure and obstructive sleep apnea had more than twice the adjusted risk of death over an average of three years, when compared with HF patients with no sleep apnea, as reported by heartwire.

In the current study, Dr Shahrokh Javaheri (University of Cincinnati College of Medicine, OH) et al tested 88 systolic HF patients for central sleep apnea (CSA) during two consecutive nights of sleep study; CSA was defined as an apnea-hypopnea index of >5.

In all, 56 subjects were found to have CSA, while 32 did not. Over a median follow-up of 51 months, survival among subjects with CSA was 45 months, exactly half that of those without CSA, who lived a median of 90 months. In Cox multiple regression analyses, CSA was independently correlated with poor survival, as was low diastolic blood pressure and right ventricular systolic dysfunction.

In an interview with heartwire, Javaheri said that these three factors, while independent predictors of reduced survival, likely work synergistically to increase risk. Sleep apnea, he noted, likely increases pulmonary hypertension, which in turn exacerbates right ventricular dysfunction. Reductions in diastolic blood pressure could also contribute to myocardial ischemia during sleep.

"If people with sleep apnea already have a low diastolic blood pressure, that may further impair the ventricular filling through the coronary circulation," he said. "These really are feeding each other in a major way. . . . We now have congestive heart failure, pulmonary hypertension, CSA, impairment of the right ventricle, and low diastolic blood pressure, and these will all feed each other so that there will be a very vicious cycle that could result in impairment of the inflow from the aorta to the ventricles, ischemia, arrhythmia, and potentially even heart attack."

Javaheri et al conclude that physicians need to be aware that CSA may confer reduced survival in people with systolic heart failure. "We need to look into patients with a higher index of suspicion for having sleep apnea," he said. "Cardiologists should look into these patients, send them for a sleep study, and treat them appropriately if they have it."