2 Tests May Improve Heart Patients' Care, Studies Suggest
But experts say coronary artery calcium scans, best at predicting disease, have drawbacks
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Tuesday, August 21, 2012
A special type of CT scanning can produce images that show if there are calcium deposits in the coronary arteries. Someone with signs of coronary artery calcium has 2.6 times greater odds of having a heart attack than someone who doesn't have these deposits, according to one of the studies.
"Coronary artery calcium is far superior [at predicting heart attack] to all of the other top-tier markers we studied," said Dr. Joseph Yeboah, the lead author of one of the studies and an assistant professor of cardiology at Wake Forest Baptist Medical Center in Winston-Salem, N.C.
Results from both studies appear in the Aug. 22 issue of the Journal of the American Medical Association.
Doctors currently rely on a test called the Framingham Risk Score to assess a person's heart disease risk. According to Yeboah, however, this test is only good for those in the low- and high-risk categories. If someone falls in the middle on the Framingham score, the best course of action is not always clear.
Many other seemingly useful tests have been studied on their own, but Yeboah and his colleagues wanted to know how these tests would fare if they were compared to one another. So they compared coronary artery calcium scans, ankle-brachial index, high-sensitivity C-reactive protein (CRP), family history, carotid intima-media thickness and brachial flow-mediated dilation to see how well each predicted heart disease.
The ankle-brachial index compares the blood pressure in your arm to the blood pressure at your ankle. High-sensitivity CRP is a blood test that looks for CRP, a marker of cardiovascular disease. Carotid intima-media thickness measures the thickness of the inner lining of the carotid artery. Brachial flow-mediated dilation uses ultrasound to see how well the blood vessels in the arm work.
The study included almost 7,000 people from six centers in the United States. About 1,300 were considered intermediate risk and had complete data on all of the tests. After almost eight years of follow up, 94 people had a heart attack, were treated for chest pain, were resuscitated after cardiac arrest or died from a heart event.
A positive finding on the coronary artery calcium test translated to 2.6 times greater odds of having a heart event. Results from the ankle-brachial index indicated 21 percent lowered odds of a heart event. The high-sensitivity CRP findings indicated 28 percent higher odds of a heart event, and those with a family history of heart disease had more than double the odds of having a heart event.
The carotid intima-media thickness test and the brachial flow-mediated dilation weren't found useful in predicting heart risk in this study.
The second study, led by Dutch researcher Hester Den Ruijter, also looked at the usefulness of carotid intima-media thickness. The researchers reviewed data from 14 studies involving nearly 46,000 participants and found that the carotid intima-media thickness test was associated with a small improvement in heart disease prediction, but that the improvement was so small it's likely not to be helpful in clinical practice.
"There seems to be little information gained from [the carotid intima-media thickness test] that would alter current decision making, and it appears that the extra cost isn't justified," wrote the authors of an accompanying editorial in the same journal issue.
"On the other hand," they wrote, the "coronary artery calcium score, which did improve the [risk prediction] substantially, requires additional assessment to determine whether the added information from this testing is truly useful."
The authors added that radiation exposure and costs are of concern when considering this test.
Dr. Tara Narula, a cardiologist at Lenox Hill Hospital in New York City, agreed that radiation and cost need to be considered.
"There are important limitations to mass promotion of the use of [coronary artery calcium] scoring," Narula said. "First, coronary calcium screening implies a small dose of radiation exposure to patients with possible longer-term cancer risk. Second, there are financial costs to consider from the cost of [the test] itself to the cost of chasing down incidental findings with further testing."
Yeboah said further studies need to be done to define the risks of radiation and the benefits of the information gleaned from coronary artery calcium scans. As for the cost, he said, in his center the test is less than $200, although it varies around the country.
Still, "the amount of money society loses will be more than if we could have prevented a heart attack with the test," he said. "Preventing a heart attack is priceless."
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