Repeat Ultrasounds Predict Heart Risk

Aug. 19, 2008 -- Repeat examinations using ultrasound could help identify patients at high risk of having strokes or heart attacks, according to a new study.

Researchers from Austria performed ultrasound exams of the carotid arteries, the vessels in the neck that supply the brain with blood, and then repeated the exams six to nine months later to see if they could predict which patients were at high risk of a heart attack or stroke.

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They zeroed in on changes in plaque -- the buildup of fat, cholesterol, and other substances that can narrow blood vessels. The researchers found that patients whose plaque appeared unstable were more likely to have a heart attack or stroke during the three-year follow-up.  

About 600,000 Americans have a new or first stroke each year, according to American Heart Association estimates, and another 600,000 have a first heart attack. The attacks often come without apparent warning, as in the case of NBC newsman Tim Russert, who died June 13 of a heart attack after plaque ruptured in an artery, according to his doctor.

Tracking Plaque

For years, physicians have performed ultrasound exams of arteries in high-risk patients to determine how much the plaque has caused a narrowing in the blood vessels, called stenosis.

But "the determination of the degree of stenosis alone is insufficient to predict patients' risk," says Markus Reiter, MD, a physician at Medical University of Vienna, and the study's lead author. That is because a significant number of heart attacks and strokes occur in those whose blood vessels may not be extremely narrowed.

So Reiter's team zeroed in on patients who did not have symptoms of heart attack or stroke but were known to be at high risk for such problems. They gave them two ultrasound exams to analyze in detail the type of plaque they had, and then followed the plaque over time to see if they could predict which patients were more likely to have a cardiovascular crisis.

Repeat Ultrasounds to Predict Heart, Stroke Risk

Reiter's team first did ultrasound exams of the carotid arteries of 1,268 patients at high risk of cardiovascular disease because of multiple risk factors, such as smoking, diabetes, high blood pressure, high cholesterol, or known blockages in other blood vessels such as the coronary arteries.

Then they focused on the 574 patients with clearly demonstrable plaque buildup in the carotid arteries.

Six to nine months later, these patients all had repeat ultrasounds to measure changes in their plaque.

Reiter's team used the ultrasound images and a computer-assisted evaluation (called gray-scale median or GSM) to evaluate the darkness of the plaque and its density. If plaque appears darker, it has a low GSM and is thought to be unstable, more likely to rupture or burst.