With all the hype about the best way to detect heart disease before it finds you, many people wonder whether a heart scan is the way to go.
A coronary calcium scan, or heart scan, can determine heart disease risk with no sweating on a treadmill or injecting of dyes. It’s a type of CT scan–a computerized X-ray–that detects and measures calcium in the arteries, the marker for plaque buildup.
The painless, non-invasive test is available at centers nationwide for around $400, often without a doctor’s prescription. But some claim the test may be no better at predicting heart disease than risk factors alone. The test carries a small risk of radiation, and the cost is most often picked up by the patient.
Physicians rely on risk factors to determine risk for heart disease–increased age, obesity, high blood pressure, high cholesterol, smoking, diabetes, inactivity and family history. The more risk factors you have, the greater your chances for a heart attack.
“The coronary calcium scan is a good test for people at `intermediate’ risk of heart attack, meaning they have a few risk factors,” said Dr. Andrew Hamilton, chief of cardiac imaging at Evanston Northwestern Healthcare. Studies show the test is less useful for people at high risk or low risk, he said.
Those at low risk are unlikely to have a heart attack anyway, Hamilton said. Modifying one’s lifestyle by losing weight or stopping smoking may be all that’s needed. On the flip side, people at high risk most likely already have coronary calcium, so a heart scan tells them nothing they couldn’t assume from their risk factors.
Choice of tests
For patients at intermediate risk, Hamilton chooses either a stress echocardiogram, a stress nuclear test or a heart scan.
“I’ll do a stress test in patients with symptoms, but some people without symptoms have used heart scans to determine their risk too,” he said. A stress echo looks at the heart with ultrasound before and after exercise, while a stress nuclear test involves injecting a radioactive tracer at peak exercise. Both imaging tests are more accurate than a treadmill stress test.
If either stress test is normal, the chance of having a heart attack is less than 1 percent during the next 12 months, said Hamilton. He starts these patients on cholesterol-lowering drugs. If a stress test shows a blockage, the patient will start medication and in some cases have an angiogram, or X-ray of the blood vessels, to determine where and how severe the blockage is.
If a heart scan detects a high level of coronary calcium, the patient will need a stress echo or a stress nuclear test to find out whether any blood flow is restricted. If the heart scan is negative, or shows a low level of coronary calcium, the patient can focus on reducing risk factors, Hamilton said.
Although all stress tests can detect blockages or narrowings in the heart that are significant–more than 50 percent blocked–a normal stress test cannot rule out early-stage coronary disease. A heart scan that shows no coronary calcium, however, most likely means the heart arteries are normal.
“Most heart attacks occur when there is less than a 50 percent blockage,” said Dr. James Ehrlich, clinical assistant professor of medicine at George Washington University in Washington, D.C. Therefore, the majority of heart attack victims would have passed all stress tests in the weeks before their heart attack.
“The stress test is a valuable tool in symptomatic patients with suspected coronary blockage, but it has no . . . ability to detect early coronary heart disease,” he said.
The heart scan may be the best way to identify patients who need further imaging tests. Its major drawback is that the presence of calcium represents a later stage of disease. “We cannot determine who is developing early-stage coronary artery disease because calcium shows up only later in the disease process, and narrowing of the coronary arteries can occur without coronary calcium buildup,” Hamilton said.
Still, some say the heart scan picks up coronary calcium earlier than any other test. “The CT coronary calcium scan detects coronary disease 10 years earlier than any type of stress test, earlier than an angiogram and earlier than any non-invasive procedure,” said Bruce C. Friedman, president of Heart Check America Inc., which offers heart scans at private centers across the country.
Heart Check America’s guidelines call for scanning men over 35 and women over 40. “We don’t scan those who are younger and have no risk factors, unless they have a referral from their personal physician,” Friedman said. If someone younger but with risk factors requests the test, the clinic’s medical director decides whether it’s medically appropriate, he said.
John Thames, 37, of Libertyville recently had a CT scan at his wife’s urging. His “good cholesterol,” or HDL, was a little low, and his grandfather had had a stroke. Thames decided to have a treadmill stress test and CT scan. No blockages were found, he said.
“I wasn’t experiencing symptoms, but I wanted to put my wife’s anxieties to rest,” Thames said. “I wanted an overall physical workup, because you hear so many bad stories.”
Bypass time
When any disease is present, the patient will start medication to lower cholesterol and blood pressure, as well as modify his lifestyle, Hamilton said. Narrowing in one or more arteries may be fixed with a stent that props open an artery. Severe disease of multiple arteries may require a heart bypass, in which a healthy blood vessel is grafted around the blockage.
“Bypass is not a cure-all,” Hamilton said. “It gets more blood past blockages, but the patient still has disease in the arteries themselves requiring lifestyle changes and medication.”
The more aggressively you treat risk factors, the more you can lower your risk for a heart attack, said Dr. David Faxon, chief of cardiology at the University of Chicago Hospitals and former president of the American Heart Association.
If you lower your cholesterol to suggested guidelines, you reduce your risk by 25 percent. Walk briskly three times a week for 30 minutes and reduce the risk by 25 percent. Take a baby aspirin a day and reduce the risk by 25 percent.
Although studies have linked full-body scans to cancer, the long-term risk of radiation exposure from a heart scan is minimal if used in moderation, said Dr. Robert Edelman, chair of the department of radiology at Evanston Northwestern Healthcare. The risk would likely accumulate if the scans are repeated at frequent intervals, such as yearly.
