March 10, 2010 -- A large percentage of patients without known heart disease who undergo invasive cardiac catheterization to check for dangerous artery blockages do not have them, a new study suggests.
Duke University Medical Center researchers found that almost two-thirds of patients with stable chest pain who had catheterization procedures did not have significant artery disease.
More than 10 million Americans experience chest pain each year and many have not been diagnosed with heart disease.
Cardiac catheterization is commonly performed in an effort to determine the cause of the pain, but the findings suggest a need for better ways to identify which of these patients will benefit from the invasive procedure, Duke University Medical Center cardiology professor Pamela S. Douglas, MD, tells WebMD.
The study appears in the March 11 issue of the New England Journal of Medicine.
"We want to be clear that if someone is having a heart attack and their doctor sends them to a cath lab, they shouldn't argue," she says. "But a stable patient who has not been diagnosed with heart disease and who does not need catheterization for pain control may want to ask about the risks and benefits."
How Cardiac Catheterizations Work
Cardiac catheterization is performed to examine how well the heart and arteries are functioning. A thin plastic tube, or catheter, is inserted into a blood vessel in the arm or leg and the tube is then guided into the coronary arteries or the heart.
When dye is injected through the catheter into the coronary arteries to check for blockages, the procedure is known as coronary angiography.
In the newly published study, the researchers used a national cardiology registry to identify 2 million people who had cardiac catheterization at 663 hospitals across the U.S. between January 2004 and April 2008.
They determined that roughly 400,000 of these people, or one in five, had stable chest pain without a previous diagnosis of heart disease.
Most of these patients had undergone noninvasive cardiac testing, such as an exercise stress test or electrocardiogram, before having a coronary angiography. But only 38% ended up having significant coronary artery blockages.
"This suggests that our ability to identify disease prior to sending patients to the cardiac cath lab is not as good as it should be," Duke assistant professor of medicine and study co-researcher Manesh R. Patel, MD, tells WebMD.
Douglas points out that the widely used noninvasive tests are not very accurate in moderate- to low-risk patients.
"These patients are more likely to have a false positive finding than a true positive finding, and end up having the invasive testing when they don't need it," she says.
Both researchers say more research is needed to determine how to best manage patients with stable chest pain without a diagnosis of heart disease.
Douglas is leading one of the first major trials to do this: a 10,000-patient, $5.5 million study funded by the National Heart Lung and Blood Institute that will compare traditional exercise stress testing to the noninvasive imaging procedure known as CT angiogram.
American Heart Association president Clyde Yancy, MD, agrees that such studies are needed, but he says it is not clear from the current research that too many cardiac catheterizations are being done.
"A test that fails to find something may be just as valuable as a positive test," he says. "A negative test can reassure both the patient and the doctor. It can also lead to less unnecessary treatment, which can save health care dollars."
The biggest predictors of clinically significant artery blockages in the study were recognized risk factors for heart disease, such older age, being male, tobacco use, and having diabetes, high cholesterol or high blood pressure.
Yancy says understanding these risk factors and addressing those that are modifiable is the most important thing patients can do to lower their heart attack and stroke risk.