David Brill
Treating obstructive sleep apnea (OSA) could help to prevent nighttime heart attacks, according to new research.
Professor Virend Somers and colleagues found that patients who had a myocardial infarction (MI) between midnight and 6 a.m. were six times more likely to have OSA than those whose attack happened at other times.
Although definitive evidence of cause and effect is presently lacking, the study suggests that OSA could be a trigger for nighttime MI.
"If your patient has a heart attack waking them from sleep you might want to get them checked out for sleep apnea, then individualize decisions regarding treatment," said Somers, a cardiologist at the Mayo Clinic in Rochester, Minnesota, US.
Randomized controlled trials are now needed to prove whether treating OSA can actually prevent MI and strokes, he said, adding that the observational data so far is "strongly suggestive" of a causative link.
The study involved 92 patients with a recent MI. Twenty out of 22 patients whose attack occurred at night were subsequently found to have OSA when assessed by overnight polysomnography. [J Am Coll Cardiol 2008 Jul 29;52(5):343-6]
Dr. Anne Hsu, a senior consultant in the sleep disorders unit at Singapore General Hospital, agreed that patients with nocturnal MI should be evaluated for OSA in light of the study.
She also recommended that patients with coronary artery disease with or without myocardial ischemia or infarction be screened for OSA.
"Ask for a history of habitual loud snoring and excessive daytime sleepiness, and
examine for habitus of OSA such as narrowed oropharynx, receding or small lower jaw or short and obese neck," she said.
OSA can be treated with continuous positive airway pressure therapy, surgery and oral appliances. Patients should also be encouraged to cut down on cigarettes and alcohol, maintain an ideal body weight and sleep lying on their side, Hsu said.
She added that GPs can refer their patients to specialist medical centers and sleep disorder clinics for treatment of OSA.
The research adds to a growing volume of literature linking OSA to cardiovascular
disease. A joint statement on the subject was released recently by the American Heart Association and the American College of Cardiology. [Circulation 2008 Jul 28 Epub ahead of print]
Somers, who is also lead author of the statement, estimates that around 20 percent of MIs occur at night.
Patients with OSA effectively stop breathing at certain times while sleeping, causing their oxygen levels to drop, he said. This could prompt a reflex increase in sympathetic activity which sends the adrenaline system into overdrive, causing blood vessels to tighten and blood pressure to increase as a result.
These conditions are stressful for the cardiovascular system and could explain how OSA leads to MI, Somers said.
A limitation of the present study is that only patients who survived their MI and came to hospital were included, so the data may not be applicable to fatal events he added.
No comments:
Post a Comment