Wearing a continuous positive airway pressure (CPAP) device not only helps heart failure patients with obstructive sleep apnea get a good night’s rest, it lowers blood pressure and heart rate well into the morning, apparently, by reducing sympathetic nervous system activity, according to a new study (PDF) in the June 21, 2005, issue of the Journal of the American College of Cardiology.
“The bottom line is that when we abolished obstructive apnea during sleep by applying CPAP at night, we caused a number of changes that carried over into the morning during wakefulness. Specifically, we’ve shown that the sympathetic drive from the brain to resistance blood vessels in skeletal muscle is attenuated. At the same time, there is a fall in blood pressure and a fall in heart rate. The net result is a reduction in the work of the heart, which is evident in the morning when the patient is awake and now breathing normally,” said John S. Floras, M.D., D.Phil., F.A.C.C., at the University of Toronto in Canada.
In patients with obstructive sleep apnea, tissue in the upper throat collapses intermittently, temporarily cutting off breathing and sometimes waking patients. This study did not include patients with central sleep apnea, which has a different cause.
The researchers, including lead author Kengo Usui, M.D., Ph.D., randomly assigned 17 patients referred from the Heart Failure programs of the Mount Sinai and Toronto General Hospitals, who also had moderate to severe obstructive sleep apnea, to two groups. The eight patients in the treatment group were treated with CPAP, in addition to the optimal heart failure management given to all participants. After one month, patients in the CPAP group had fewer obstructive sleep apnea events. In addition, several variables related to heart failure were improved even during the morning after waking. Muscle sympathetic nerve activity, which is related to the constriction of blood vessels, was lower, as were blood pressure and heart rate.
While an earlier study by this research team had shown CPAP could reduce blood pressure and heart rate and improve ejection fraction in heart failure patients with obstructive sleep apnea, this study is the first of its kind to demonstrate suppression of the sympathetic nervous system after long term treatment with CPAP.
“This was the novel observation. No one has shown this before in a randomized clinical trial involving patients with heart failure and obstructive sleep apnea,” Dr. Floras said.
Dr. Floras noted that further work is needed to determine whether these changes after one month of CPAP use lead to long term benefit for these heart failure patients.
“We have no data that tells us that by treating such patients, we will prolong life, so that’s the subject of future study,” he said.
Nevertheless, he advised clinicians to watch for signs of sleep apnea in their heart failure patients because obstructive sleep apnea puts extra stress on hearts during sleep, normally a restorative period. However, he noted that unlike most patients with obstructive sleep apnea, those with heart failure often do not report daytime fatigue.
“Our view is that it would be important to identify and treat obstructive sleep apnea in a heart failure population because the drug therapy of heart failure does not address the pathophysiology of sleep apnea. So, in order to optimize medical treatment, we believe that treatment of sleep apnea is an important component of the overall management of these patients,” Dr. Floras said.
Virend K. Somers, M.D., D.Phil., who wrote an editorial in the journal along with Apoor S. Gami, M.D., and Lyle J. Olson, M.D., at the Mayo Clinic College of Medicine in Rochester, Minn., said this study provides important additional information regarding decreases in sympathetic drive if heart failure patients with high blood pressure have their sleep apnea treated.
“However, it is important to keep the study in perspective in that what is shown is an improvement of a surrogate of outcome in heart failure. What we still need data on is whether treating sleep apnea in patients with heart failure has significant effects on hard cardiovascular end points such as mortality,” Dr. Somers said.
He agreed that sleep apnea should be treated in heart failure patients, noting that other treatment options already shown to improve outcomes should be fully utilized and that treatment decisions should be made based on the individual patient.
Prof. Ian Wilcox, M.D., at the University of Sydney and the Royal Prince Alfred Hospital in Australia, who was not connected with this study, noted that CPAP treatment is relatively inexpensive and widely available.
“The study indicates a mechanism for the improved cardiac function shown to occur when patients who have both left ventricular dysfunction and obstructive sleep apnea are treated with CPAP,” he said. “Unfortunately, patients with congestive heart failure are treated by cardiologists and those with sleep apnea have traditionally been seen by pulmonologists. Increased recognition by cardiologists of sleep-disordered breathing in their patients is critical to the wider use of this type of therapy.”
Dr. Wilcox also remarked that since these heart failure patients usually do not suffer from daytime sleepiness, despite their sleep apnea attacks, the main benefits of CPAP treatment would be potential improvements in heart function and exercise capacity.
The American College of Cardiology, a 31,000-member nonprofit professional medical society and teaching institution, is dedicated to fostering optimal cardiovascular care and disease prevention through professional education, promotion of research, leadership in the development of standards and guidelines, and the formulation of health care policy.