New treadmill 'scores' may help physicians better diagnose heart disease

November 08, 1999

ATLANTA, Nov. 9 -- A new scoring system used in treadmill testing may help physicians improve their accuracy in diagnosing heart disease, according to a study presented today at the American Heart Association Scientific Sessions.

Treadmill tests have been used for decades to help diagnose atherosclerosis, the narrowing of coronary arteries that can lead to a heart attack or stroke. The treadmill test, also called an exercise stress test, helps physicians learn how well an individual's heart handles physical exertion. The test measures heart rate, blood pressure and the electrical function of the heart as the patient walks on a treadmill. The speed at which the patient walks gradually increases, requiring the body to use more oxygen and the heart to pump harder.

Treadmill test results can show if there's a lack of blood supply through the arteries that go to the heart.

A diagnosis of heart disease is made by using results of the treadmill test, along with other "clinical" information, such as medical problems and risk factors. An angiogram -- an X-ray of the blood vessel -- can be used to confirm the diagnosis.

According to Victor F. Froelicher, M.D., of Stanford University Medical School, lead researcher of the study, a new mathematical equation that uses information from the treadmill test provides a "score" that may improve the diagnosis of coronary heart disease and avoid the need for and expense of an angiogram.

"The scores are based on the same information that the physician has, but the information is put into a mathematical equation that provides a probability of disease. Our goal was to determine if these scores were as accurate as the physician's diagnosis. No one had studied this question before," he says.

The research, involving 599 male patients, none of whom had previously had a heart attack, was carried out at the Stanford/Palo Alto V.A. Health Center in Palo Alto, Calif., and William Beaumont Hospital in Birmingham, Mich. The study found that 58 percent of the patients had evidence of significant heart disease determined by an angiogram. The results of the treadmill tests and clinical data -- but not the angiogram -- were sent to a total of 142 physicians, including 44 "expert" cardiologists (defined as those with many years of experience in conducting studies and performing angiography), 48 less experienced cardiologists and 50 internists. All were chosen at random and asked to estimate whether the probability of coronary artery disease was high, intermediate or low, and estimate probability from 0 to 100 percent.

Froelicher and his fellow researchers found that treadmill scores produced diagnoses that were 77 percent accurate overall compared to 69 percent for the "expert" cardiologists, 65 percent for the other cardiologists, and 66 percent for the internists.

"While the treadmill scores were similar to the estimates provided by the expert cardiologists, they clearly outperformed all physician estimates of coronary disease," Froelicher says.

"Many cardiologists want the latest in high-tech diagnostic devices. But our study shows that treadmill test scores provide a more accurate diagnosis of heart disease than physicians and are at least as accurate as the most expensive new diagnostic equipment," he says.

"This information sends a very important message to both the public and physicians, especially at a time when we are trying to contain health care costs," he emphasizes. "The newest products of medical technology are adding tremendously to health care costs, yet our research shows they won't do a better job of diagnosing coronary disease than what we've got already."

For example, he says, electronic beam-computed tomography (EBCT) -- which uses X-rays to detect calcium in heart arteries -- is viewed by many as the "state of the art" for diagnosing heart disease. "Our findings show that these newer, more expensive tests have no real advantages over treadmill tests in producing an accurate diagnosis when scores are used," he says.

The research shows that for diagnosing heart disease, treadmill tests, with the new scoring system, benefit both physicians and patients. "It's like getting a second opinion," he says. "The scores help physicians decide who needs to see a cardiologist and who does not. The system may prevent the unnecessary use of angiogram and provides extra assurance to the patient who does need to see a cardiologist."

Co-authors are Michael J. Lipinski, Jeffrey West, M.D.; Lars Osterberg, M.D.; and John E. Atwood, M.D., of Stanford/PAVAHCS, Palo Alto, Calif. and Barry A. Franklin, M.D. of William Beaumont Hospital.
Media advisory: Dr. Froelicher can be reached at 650-493-5000 ext. 64605. (Please do not publish telephone numbers.)

American Heart Association

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