Tuesday, November 11, 2008

Obstructive Sleep Apnea (OSA): Caution Raised for Sudden Cardiac Death (SCD)

This news story brings to mind how annoying it is for the medical profession to constantly use jargon and acronyms to describe medical conditions. In this case, OSA may cause SCD.

A very large study on people with obstructive sleep apnea (OSA), in which the sleep characteristics of nearly 11,000 adults were examined in an overnight sleep laboratory, shows that OSA - and, in particular, the low nighttime oxygen saturation of the blood it causes - may be a risk factor for SCD, or "sudden cardiac death."

OSA is a condition that disrupts breathing during sleep and is associated with obesity. SCD can occur when the heart's electrical system malfunctions. When treatment such as defibrillation is not administered quite quickly, that person dies.

If further studies validate these recent findings, OSA would join established risk factors such as smoking, obesity, high cholesterol and high blood pressure. Mayo Clinic cardiologist Apoor Gami, M.D., the lead researcher on the study, has shown thatlow oxygen alters the blood vessels in a way that promotes heart disease. Gami says that the new Mayo work is the first large study to rigorously test the hypothesis.

“Nighttime low oxygen saturation in the blood is an important complication of obstructive sleep apnea,” says Virend Somers, M.D., Ph.D., the study’s principal investigator. “Our data showed that an average nighttime oxygen saturation of the blood of 93 percent and lowest nighttime saturation of 78 percent strongly predicted sudden cardiac death, independent of other well-established risk factors, such as high cholesterol. These findings implicate OSA, a relatively common condition, as a novel risk factor for SCD.”

Dr. Somers says these early results are relevant to clinical care. He urges physicians to watch for OSA in their heart patients and consider treating severe cases. “It is possible that diagnosing and treating sleep apnea may prove to be an important opportunity to advance our efforts at preventing and treating heart disease,” he says.


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