By Genevra Pittman
NEW YORK (Reuters Health) - The proportion of patients who have blocked arteries show up during a stress test has dropped "enormously" over the past two decades, according to a new study.
However, researchers disagreed about why that might be the case - whether the tests are getting worse, people's heart problems are becoming less severe, or simply too many healthy people are being referred for testing they don't need.
On a stress test, doctors monitor a person's heart and blood vessels during exercise or after administering a combination of drugs that similarly stress the heart. The exams are used to make a more definitive diagnosis among patients who have some signs of a blockage but not enough to warrant treatment, such as with artery-opening stents.
For the new study, researchers tracked close to 40,000 people who underwent stress testing to look for blocked arteries at Cedars-Sinai Medical Center in Los Angeles between 1991 and 2009.
During that period, the proportion of referred patients with an abnormal test fell from about 41 percent to less than nine percent. Similarly, the proportion with moderate to severe blockage dropped from 21 percent to five percent, according to findings published Monday in the Journal of the American College of Cardiology.
In the study's later years, more patients undergoing testing were obese or had diabetes, the research team found, but fewer smoked.
The researchers, led by Dr. Alan Rozanski from St. Luke's Roosevelt Hospital in New York City, suggest the findings may mean fewer people with heart-related symptoms, such as chest pain, now have blockages. Or it could be that doctors need a better test to diagnose those patients.
Dr. Patrick O'Malley, an internist at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, had a different interpretation.
"The fact that the results are changing over time can only mean one thing, and that's that we're overusing this test," O'Malley, who wasn't involved in the new research, told Reuters Health.
"I think it represents a culture of testing that has been sort of an epidemic in this country."
It could be that more people with mild or non-traditional heart disease symptoms - such as shortness of breath - are being sent to stress testing when it's unlikely to reveal any problems, O'Malley said.
The majority of tests performed in the most recent years used medication rather than exercise to stress a patient's heart, Rozanski's team found. Rozanski did not respond to requests for comment before deadline.
So-called pharmacologic stress tests are typically three to four times more expensive than an exercise stress test, according to O'Malley. He thinks they should largely be limited to people who aren't able to walk on a treadmill.
According to the Healthcare Blue Book, an exercise stress test costs about $200, depending on the hospital.
The use of more expensive tests - in likely less appropriate patients - reflects how "obsessed" heart doctors have become with finding and treating any small abnormalities, O'Malley said.
"If the prevalence of (positive test) results are going down, it just means we're doing too many, and we're doing them on people we shouldn't be doing them on," he said.
SOURCE: http://bit.ly/P8Btq1 Journal of the American College of Cardiology, online March 4, 2013.