But the test's cost may still be prohibitive, experts say
MONDAY, June 23 (HealthDay News) -- Scanning the heart's arteries for calcium deposits accurately predicts the overall death risk for American adults, a new study suggests.
"So far, this is the best predictor we have of who will have a problem and who will not," said study co-researcher Dr. Matthew Budoff, associate professor of medicine at the Harbor-UCLA Medical Center.
He and his colleagues reported the finding in the July 1 issue of the Journal of the American College of Cardiology.
A calcium scan looks for calcification, a hardening of the arteries caused by high blood fats and calcium deposits that can eventually block blood vessels, causing heart attacks, strokes and other major problems.
But calcium scans can be controversial, partly because they are promoted vigorously by for-profit centers, where they often cost $300 or more.
The new study might help end that controversy, because it shows that coronary artery calcium levels are directly associated with the risk of death, Budoff said.
"I think it better validates the technique with an endpoint that people can rely on," he said. "There has been a lot of criticism of coronary calcium studies, because they have been short-term, with endpoints such as angiography or bypass surgery. Those are endpoints that are more up to the doctor to decide."
Some previous studies have been more definite. One, reported earlier this year by cardiologists at the University of California, Irvine, who looked at more than 6,700 men and women, found that the risk of a coronary event such as a heart attack was 10 times higher for people with the highest calcium deposit scores than for those with the lowest.
The newly reported study enrolled more than 35,000 people ages 40 to 80, in the cities of Torrance, Calif., and Nashville, Tenn., who were followed for an average of 5.8 years after having a coronary artery calcium scan by electron beam tomography.
"Increasing coronary artery calcium was associated with decreasing survival across all age deciles [10-year intervals]," the researchers reported.
Scanning not only indicated those at higher risk, but also could be used to indicate a better chance of survival in persons with major risk factors such as obesity, high blood pressure and diabetes, the team wrote.
"The use of coronary calcium scanning allowed us to reclassify more than 40 percent of the patients, 70 or more years old, often by excluding risk," the report said.
"It is clear that coronary artery calcium is a good predictor of cardiovascular events and cardiovascular mortality, and since cardiovascular events are a major cause of mortality, it does not surprise me that it is a good predictor of all-cause mortality," said Dr. Robert Detrano, professor of radiological sciences, who led the University of California, Irvine, study.
Calcium scanning is useful, "because you want assistance in deciding what you can do to keep the patient health," Detrano said.
The American Heart Association and the American College of Cardiology have recommended calcium scans only for persons at intermediate risk of heart disease, not for those at high or low risk. Risk is determined by considering such factors as age, family history, obesity, diabetes and cholesterol levels. Presence of one or two of those factors indicates intermediate risk, Budoff said.
"That would be a man over 45 or a women past menopause with diabetes or high blood pressure or a family history or who smokes," he said.
Budoff defended the cost of a calcium scan as "about the same as a treadmill test and cheaper than a colonoscopy." Coverage of the procedure by Medicare and medical insurers differs from region to region and company to company, he said. A calcium scan can save money in some cases by showing that someone might not need medication such as cholesterol-lowering statins, he said. "The cost is lower than the co-pay for a cholesterol pill for one year," Budoff said.
But Detrano disagreed. "That issue is still standing and still needs to be addressed, and not by a study that shows that it predicts all-cause mortality," he said.
Detrano noted that he has been working to bring better medical care to poor people in China. Americans might be able to afford calcium scanning, but "it is beyond the means of the great majority of people on this planet," he said.
Meanwhile, a study being published in the June 23 issue of Archives of Internal Medicine provided more proof of the value of calcium scanning. The study, done by a multi-institutional group and led by Dr. Aaron Folsom of the University of Minnesota, compared the prognostic value of calcium scans with measurements of the wall of the carotid artery, the major artery leading from the heart to the brain.
The study of almost 6,700 middle-aged and older Americans who were followed for up to five years found that "coronary artery calcium score is a better predictor of subsequent cardiovascular events than carotid intima-media thickness [measuring the artery's wall]," the researchers reported. But they noted that whether and how to clinically use bioimaging tests of early atherosclerosis remains a topic of debate.
There's more on coronary calcification at the American Heart Association.
SOURCES: Matthew Budoff, M.D., associate professor, medicine, Harbor-UCLA Medical Center, Torrance, Calif; Robert Detrano, M.D., professor, radiological sciences, University of California, Irvine; June 24, 2008, Archives of Internal Medicine; July 1, 2008, Journal of the American College of Cardiology
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