NEW YORK (Reuters Health) - Stress appears to inhibit the ability of blood vessels to expand--a problem that may explain why extremely stressful events can precipitate heart attacks, new study findings suggest.

Sudden stress, such as that related to anger, bereavement or war, can trigger heart attacks or sudden cardiac death, according to Dr. Georg Noll of the University Hospital in Zurich, Switzerland. However, it is not clear how such stressful events affect the heart.

In the study, Noll and his team used ultrasound to look at the blood vessels of 23 healthy people as they performed a stressful task--quickly pushing buttons in response to flashing lights. Typically, the endothelium--the lining of the blood vessels--can boost blood flow as needed to supply oxygen to muscle, including the heart.

The investigators found that the stress cut the ability of the endothelium to respond by 50% for about 45 minutes. The 3-minute mental stress test also caused both blood pressure and heart rate to temporarily increase, according to the report released May 21st in the rapid access issue of Circulation: Journal of the American Heart Association.

Further tests suggested that blocking a receptor called ETa, which is found on cells of the endothelium, could block the blood vessel-constricting effects of stress.

"This study provides the first evidence that sudden mental stress induces prolonged endothelial dysfunction via activation of ETa receptors," the authors report.

The finding provides a clue as to why stressful events could spell trouble for people who already have narrowed or blocked arteries. Stress may act to compound already restricted blood flow that could lead to a heart attack or stroke.

Blocking ETa receptors could "represent a new therapeutic strategy" in the prevention of heart disease-related problems, Noll and colleagues conclude.

SOURCE: Circulation 2002;10.1161/01.CIR.0000021598.15895.34.

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