(September 14, 2009 - Insidermedicine)

The causes of stroke following cardiac surgery are more complicated than expected, according to research published in the latest issue of the Archives of Neurology.

Some probable causes of stroke following cardiac surgery include:

•    Narrowing of the carotid artery, which runs along the neck and feeds the brain

•    Low blood pressure

•    Irregular heartbeat

Researchers from Lehigh Valley Health Network in Allentown looked at the incidence and type of stroke that occurred among over 4,000 patients during a hospital admission for major cardiac surgery. Some of these patients had combined surgery on the heart and carotid artery, in an effort to reduce the risk of postoperative stroke.

Overall, less than 2% of the patients experienced a stroke, and only about 5% of these strokes involved large blood vessels. While patients with stenosis, or narrowing, in their carotid artery were at higher risk for developing a stroke, more than three-quarters of the strokes occurred in patients who did not have significant stenosis in their carotid artery. Undergoing combined carotid and cardiac surgery actually increased the risk of stroke, compared with undergoing surgery alone.

Today's research demonstrates that the condition of the carotid artery is only one of many factors that impact the risk for stroke in patients undergoing cardiac surgery. It also demonstrates that combining carotid with cardiac surgery is not an effective means of preventing stroke and may even increase the risk.