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