new sleep apnea/CPAP research

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News-Medical.Net Tuesday, 21 Jun-2005

Wearing a continuous positive airway pressure device helps heart

failure patients with obstructive sleep apnea get a good night's rest

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 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.

http://www.acc.org/