Silent Sleep Apnea Common Among Pacemaker Patients

GRENOBLE, France, March 13 -- Nearly 60% of patients with pacemakers have undiagnosed sleep apnea, according to a small European study.

This rate was significantly higher than that reported in prior studies in the general population (59% versus 21%, P<0.01), found Patrick Lvy, M.D., Ph.D., of Grenoble University and Joseph Fourier University here, and colleagues.

However, sleep apnea could not be predicted by the traditional symptoms and complaints for the most part, the researchers wrote in the April 3 issue of the journal Circulation.

The high prevalence suggests that patients referred for a pacemaker should first be screened for sleep apnea, which is known to contribute to cardiovascular disease risk, they said.

"In clinical practice, the suggestion is to search for sleep apnea in patients requiring pacemaker implantation or currently treated by pacemakers," they wrote.

"This is still recommended in patients with very few symptoms of sleep-disordered breathing (eg, the absence of excessive daytime sleepiness, as well as in young and lean subjects)," they added.

Previous studies have suggested that treating sleep disordered breathing problems to restore consistent positive pressure in the airways may reduce or reverse arrhythmia.

The study, though, included only patients who already had pacemakers implanted. None of the 98 consecutive patients (mean age 64) from 11 European cardiology centers had known sleep apnea before the sleep test.

The indication for the pacemaker was severe heart failure for 29%, high-degree atrioventricular block for 34%, and symptomatic sinus node disease for 37%.

Each completed the Epworth Sleepiness Scale questionnaire and underwent polysomnography with their pacemaker programmed to give a nearly spontaneous heart rhythm with respect to individual indications for pacing during the sleep test.

Hypopnea was defined as a reduction in flow or amplitude of thoracic and abdominal signals by at least 50% for at least 10 seconds or at least 30% and associated with arousal from sleep or oxygen desaturation of 3%. Sleep apnea was defined at having at least 10 of these episodes per hour; severe sleep apnea as having at least 30 episodes per hour.

Among the results, the researchers reported:

• Overall, 59% of patients had sleep apnea (95% confidence interval 49% to 69%).
• 50% of heart failure patients had sleep apnea.
• 68% of atrioventricular block patients had sleep apnea.
• 58% of sinus node disease patients had sleep apnea (58% clinically silent to themselves and their physicians).
• Overall, 21.4% of patients had severe sleep apnea.
• In the three groups, more than 70% of the sleep respiratory events were hypopnea.
• Patients mainly had obstructive sleep apnea rather than central sleep apnea (16% versus 8% of total events, P=0.03).

Hypertension, diabetes, and stable coronary heart disease did not affect the prevalence rates. Also, there was no correlation of hypopnea index scores with age or body mass index.

Only 25% had abnormal sleepiness scores. The mean Epworth score was low at seven on a scale of 24, where 10 is the cutoff for sleep excessive sleepiness and 16 the average for untreated obstructive sleep apnea.

Since the sleep apnea appeared to be asymptomatic among patients already implanted with pacemakers, the question of whether to treat it becomes trickier, Dr. Lvy and colleagues said.

"On the one hand, obstructive sleep apnea represents a recognized cardiovascular risk factor, including for arrhythmias," they wrote.

"On the other hand, however, treating obstructive sleep apnea patients with no or few symptoms remains much discussed and sometimes difficult because the perceived clinical benefit may prove insufficient to justify continuous positive airway pressure," they added.

Although further study will be needed to define the optimal treatment strategy, screening for symptoms should be done due to the potential cardiovascular consequences, the investigators said.

Abnormally slow heart rhythms are common among patients with obstructive sleep apnea.

Therefore, the simplest explanation for the high prevalence of sleep apnea in pacemaker patients may be that it is associated with these potentially symptomatic bradycardia episodes that lead to pacemaker implantation.

"Whether treating sleep apnea would have altered the pacing indication is unknown," the researchers cautioned, "however, a nasal continuous positive airway pressure trial, the first-line treatment of sleep apnea, could be evaluated on the basis of tolerance, treatment compliance, and treatment efficacy on cardiac rhythm."

The researchers said that their study may have been limited in the lack of a healthy control group, but said they believed comparison with recent, large epidemiologic studies is valid.