More sudden deaths after left-sided stroke than after right-sided

American Heart Association
Friday, 21 November 2003

Strokes that attack the left side of the brain significantly increase the five-year risk for sudden cardiac death, according to research reported in today's rapid access issue of Stroke: Journal of the American Heart Association.

A stroke in the left side of the brain affects the right side of the body.

The study also suggests that left-handed or ambidextrous individuals may have a lower risk of sudden cardiac death than right-handers, said principal investigator Ale Algra, M.D., associate professor of clinical epidemiology, department of neurology and Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, Netherlands.

After correcting for other risk factors for sudden death, such as previous heart attack or high blood pressure, the risk for sudden death for people who had suffered a left-sided stroke was 45 percent higher than those with a right-sided stroke and 40 percent higher for those with a bilateral stroke, Algra said. Death within 24 hours was almost one and a half times more frequent in patients with left-sided infarctions (ischemic strokes) than in patients with lesions in other brain regions or those without such lesions.

Left-handed or ambidextrous patients had a 76 percent lower risk of sudden death than right-handers.

Sudden cardiac death occurs when the heart stops abruptly. It is most often related to underlying coronary heart disease but is not uncommon in stroke patients.

Algra and colleagues studied strokes called brain infarctions in which blood clots block the brain's blood supply, usually on just one side of the brain. He said that the association between left-sided strokes and sudden death "was quite the opposite of what we expected to find."

He said that a number of small studies and several animal studies suggested that right-sided strokes were more likely to increase risk of sudden death. But unlike those earlier studies that reported only events that occurred during the acute phase of stroke, Algra was assessing results after the stroke had "progressed from acute to chronic phase."

If the link between left-sided strokes and sudden death is confirmed in other studies, "the use of beta-blockers, which lower the risk of sudden death, may be considered for patients with left-sided lesions. But such should be sorted out further in a clinical trial," he said.

Algra said he is more cautious about the role of handedness in stroke. "This is a preliminary additional finding that is based on small numbers since only about 200 patients were left-handed or ambidextrous. But still, among those patients there were only three sudden deaths, so that is rather remarkable since it appears that these people are at a quarter of the risk of others," Algra said.

It is possible that the observation about handedness is "only a chance finding," Algra said, but added that left-handed people are believed to have "more reserve networks in the brain, so it is possible that when damage is done, these reserve networks compensate for the damage."

Algra and colleagues studied medical records from 2,885 patients with symptomatic carotid disease who were enrolled in the North American Symptomatic Carotid Endarterectomy Trial from 1987 to 1996. Of these, 663 patients died, including 217 within 24 hours of symptom onset. At entry, 2,778 patients had brain scans that identified at least one area of infarction in 1,483 patients. Of those, 471 patients had one or more left-sided lesions and 477 had one or more right-sided infarctions. In 535 patients there was evidence of stroke damage on both sides.

Each year about 700,000 Americans experience a new or recurrent stroke, a rate of about one stroke every 45 seconds. Exact statistics for sudden cardiac death are not available but about 250,000 people die of coronary heart disease each year without being hospitalized. The American Heart Association estimates that most of these are sudden deaths caused by cardiac arrest.

Co-authors are Peter C. Gates, M.D.; Allan J. Fox, M.D.; Vladimir Hachinski, M.D.; and Henry J.M. Barnett M.D.

The study was partly funded by the National Institute of Neurological Disorders and Stroke.

For more information, or to contact American Heart Association, see their website at: www.americanheart.org