Feb. 6, 2002 -- A pacemaker may never become a treatment for the symptoms of sleep apnea, but researchers studying people who have pacemakers are finding that the pace at which the heart beats during sleep can improve apnea symptoms. And other researchers have developed a simple, FDA-approved device that can make it much easier to find out whether you have a sleep disorder.
In a new study, French researchers report in TheNew England Journal of Medicine that the symptom of repeated nighttime waking that apnea sufferers live with can be reduced in certain heart patients who have pacemakers.
When you have apnea, your throat closes down during sleep. When the body can't force air through the closed throat, it briefly wakes you in an effort to restore normal breathing. But the process of trying to force breathing places stress on the heart. In the long term, this stress can lead to high blood pressure and other heart troubles even though the patient often has no recollection of waking.
"Obstructive sleep apnea [OSA] appears to be one cause of high blood pressure," says Daniel Gottlieb, MD, MPH, a professor in the Boston University School of Medicine who wrote an editorial accompanying the heart-pacing study. "There is also increasing evidence that OSA contributes to the risk of heart attack, stroke, and congestive heart failure, although this is less certain."
More Beats, Improved Sleep
The French researchers, led by Stephane Garrigue, MD, MS, assistant professor at the Hospital Cardiologique du Haut-Leveque at the University of Bordeaux, studied 16 sleep apnea patients who have bradycardia, a disorder in which the heart beats faster than it should because of overstimulation of the vagus nerve.
"What we found was that by increasing the atrial pacing rate, [the overstimulation of the nerve] is counteracted and number of sleep apnea episodes decreased," said Garrigue in an email interview. "By increasing the pacing rate 15 pulses per minute over the [patient's usual nighttime rate], we observed a significant reduction in all types of sleep apnea."
Gottlieb says that though the French team's findings are interesting, they need to be replicated in other studies.
"The benefits of pacing in this study were less than would be anticipated with the standard therapy for OSA -- namely, continuous positive airway pressure," he says. "Patients with symptomatic OSA should be advised to seek standard therapy for this condition."
He adds that patients who already have a dual-chamber cardiac pacemaker for sinus node dysfunction and who also have mild sleep apnea may want to talk to their cardiologists about pacing as therapy for obstructive sleep apnea.
"It's important to note that while the findings apply to a small group of people, it may point the way to the development of new therapies, including drug therapy, for this common medical condition," Gottlieb says.
"Common" may be an understatement.
"OSA is significantly underdiagnosed, and its consequences are a burden on the healthcare system," says David White, MD, associate professor at the Harvard University School of Medicine and director of the Sleep Disorders Program at Brigham and Women's Hospital in Boston.
According to the National Institutes of Health, obstructive sleep apnea affects more than 18 million people in the United States. In addition to the heart problems it causes, the disorder is associated with cognitive and behavioral impairment, daytime fatigue, and related motor vehicle and work accidents.
Doctors usually use what are called polysomnographic measures to evaluate patients with obstructive sleep apnea. This requires an overnight stay in a sleep lab while connected to multiple leads that monitor heart, respiratory, muscle, and brain functions.
But the FDA in January approved a new technology to make diagnosing sleep apnea much easier. Using a system called "Watch PAT100," a device is worn on the wrist and a noninvasive finger probe measures the patient's body functions during sleep. It is manufactured by Itamar Medical Co., based in Israel.
The device detects changes in peripheral arterial tone, or PAT. PAT is a newly identified physiological signal that reports changes in arterial volume in the fingertip from pulsing blood. These changes have been shown in clinical trials to be a reliable indicator of sleep-related breathing disorders. The device records signals and stores them in a removable memory card. The data are downloaded to a computer for analysis to detect sleep-related breathing disorders.
"The PAT is a sensitive indicator of sympathetic activity induced by acute periods of airflow obstruction, such as associated with OSA," says White.
The manufacturers of the Watch PAT100 expect the device to be commercially available in early 2002, but Gottlieb says that traditional ways of diagnosing sleep disorders aren't going to change that quickly.
"There have been a number of simplified tests for sleep apnea," he says. "Although the PAT is promising, it is unlikely that the PAT or any other such simplified test for sleep apnea will replace standard polysomnography in the near future."
Notwithstanding Gottlieb's reservations, with FDA approval, the PAT may well help more people get simpler, faster diagnoses -- and treatment -- of this common and dangerous sleep disorder.