Stress Test May Miss Some Heart Disease
Treadmill Tests May Not Catch All Who Have Significant Atherosclerosis
Aug. 17, 2004 -- Using only a stress tests to screen for heart
disease may not catch many people who have atherosclerosis, or hardening of the
arteries, and are at risk for heart attack or stroke.
A new study suggests that additional testing using computer
imaging that looks for calcium deposits on the arteries of the heart may be
necessary to determine the level of risk in people with suspected heart
disease. Calcium deposits may indicate atherosclerosis.
Researchers found 56% of people who had normal results on their
stress tests had calcium scores that put them at increased risk for heart
disease, and 31% had scores that placed them at highest risk for heart
"Our findings demonstrate that a
relatively high number of patients who had normal readings on their stress
tests had a calcium score of greater than 100, a score that is accepted as
implying the need for aggressive medical treatment," says researcher Daniel
Berman, MD, director of cardiac imaging at Cedars-Sinai Medical Center, in a
Comparing Heart Disease Screening Tests
Stress tests have been widely used for more than 50 years to
identify people with heart disease and help direct treatment. In a stress test,
heart rate and blood pressure is monitored before, during, and after exercise
on a treadmill. It helps determine how much work the heart can take and can
help diagnosis heart disease.
In the last 30 years, stress tests done with imaging techniques
have become the most common type of stress testing. These tests use a small
amount of radioactive material that's injected into the patient during
exercise, and the material sends signals to a camera that picks up
abnormalities in blood flow to the heart that indicate atherosclerosis.
More recently, computer-assisted imaging tests that use
computed tomography (CT) scans have been used to screen for the presence of
calcium within the arteries. These tests do not require an injection. Instead,
they use special X-ray equipment to get a cross-sectional picture of calcium
buildup in the arteries.
The calcium score from these tests represents the patient's
risk of future heart-related complications. A score of zero is the best. Scores
between 1 and 100 indicate a low level of risk, scores from 100 to 400 indicate
an increased risk with treatment recommended, and a score over 400 identifies
patients at highest risk for heart attack.
New Tests May Be More Accurate
In the study, published in the Journal of the American
College of Cardiology, researchers followed 1,195 people without known
heart disease who underwent both stress testing and CT scanning as recommended
by their doctor.
The study showed that among the 1,119 patients who had normal
results on their stress tests, 56% had calcium scores greater than 100, and 31%
had scores over 400, which puts them at increased risk for heart attack.
"Our study shows that patients who have normal imaging
stress test results frequently have extensive atherosclerosis as revealed by
coronary calcium scanning," says Berman. "These findings imply a
potential role for the coronary calcium scan, after an imaging stress test,
among patients whose results are normal.
"These patients could then be identified as needing an
aggressive treatment program of diet, exercise, and medications, something
which they often would not otherwise get based upon standard blood tests and
the imaging stress test results alone," says Berman.
Researchers say the study also showed that stress test
abnormalities were rare in people with calcium scores under 100 but increased
dramatically when scores were above 100.