Calcium Scores Best Predictor of Heart Attack Risk

Scans can predict heart attack risk but often create uneccessary worry.

August 18, 2011, 2:40 PM

Aug. 18, 2011— -- Joanne Leahy, 59, of Fort Lauderdale, Fla., followed her cardiologist's recommendation and had a computer tomography, or CT, scan to check her heart attack risk, because of her family history of heart disease.

The procedure, called coronary artery calcium scoring -- or CAC -- checks for calcium buildup in the arteries. It rates heart attack risk and gauges the benefit of certain heart treatments, such as statins.

"It's quick, painless and an indicator of heart attack," Leahy said Dr. Wiliam O'Neill, her cardiologist and chief medical officer at the University of Miami Health System, told her at the time.

Doctors generally use a blood test to check for high levels of C-reactive protein, which can signal artery inflammation and is a potential predictor of a heart attack.

But Leahy's doctor went straight to the CAC scan as his first line of defense.

A study published Thursday in the Lancet now throws some data on O'Neill's confidence. The study suggests that screening for calcium buildup in coronary arteries, called atherosclerosis, may be a better method than a C-reactive protein test, which measures the amount of C-reactive protein in the blood, for not only predicting heart attack risk but whether a patient might benefit from statin therapy.

Researchers looked at 950 patients with no symptoms of heart disease and found that patients with the presence of calcium -– even those with low cholesterol levels -- had twice the risk for heart attack or stroke and four times the risk for heart disease than those with a calcium score of zero.

Statins, cholesterol-lowering medications, are prescribed to prevent or treat plaque buildup that could cause heart attacks. But many are prescribed statins because of such risk factors as age, high cholesterol, diabetes or a family history of heart attacks.

O'Neill said given the study findings, "You have to ask if they [those with no calcium] should be treated with statins."

While calcium scanning is helpful in seeing whether atherosclerosis has started, for many, calcium presence in the arteries does not necessarily indicate heart disease or even a looming heart attack. Studies have yet to show that calcium scans have reduced the risk of heart attack or death from heart disease.

Some experts do not support calcium scanning, saying that a patient may be exposed to high levels of radiation at extra out-of-pocket expense.

"Calcium scanning is one of the worst examples of medicine gone wild," said Dr. Steven Nissen, chairman of the department of cardiovascular medicine at the Cleveland Clinic. "It's taken on a 'cultlike' following."

Some experts said that since recommended heart attack prevention methods such as taking statins, losing weight or controlling blood pressure don't treat the calcium buildup, the test could lead to potentially unnecessary procedures.

"This test has led many to perform more invasive tests and then potentially act on its findings," said Dr. Howard Weintraub, clinical director of the New York University Center for Prevention of Cardiovascular Disease at the NYU School of Medicine. "Even though in the vast majority the intervention will do nothing to prevent MI [myocardial infarction -- a heart attack] or death and, in the absence of pre-existing symptoms, won't improve quality of life."

CAC may benefit adults who could be at an immediate risk of a heart attack within the next 10 years, according to American Heart Association guidelines. Those risk factors include obesity, prediabetes or a family history of heart disease.

Future guidelines for primary heart disease prevention should even include CAC for high risk patients with normal cholesterol levels, said the association.

"We think that it is time to move past traditional risk factors and blood tests and toward incorporation of direct measures of subclinical atherosclerosis in risk prediction," Dr. Michael Blaha, cardiologist at Johns Hopkins University and author of the study, said in a statement.

"This makes sense, because CAC uses modern technology to directly measure the disease we propose to treat with statins," said Blaha.

The Lancet study was actually a substudy of a previous trial by the researchers, who looked at C-reactive protein levels in asymptomatic patients.

In an accompanying editorial, German doctors said the case made for testing CAC over C-reactive protein was so strong that they now use CAC for treatment in their clinic.

The University of Miami hospital, where Leahy works, offers CAC scans to all of its employees over the age of 50. Still, some experts said that even if a calcium score could help some patients get on such preventive therapies as statins, it's premature to suggest that all would benefit from the findings of the test.

"For a call that everyone should have one, I think we need a randomized trial to show that it is beneficial to screen and then treat differently before it could be recommended for the public," said Dr. Christopher Cannon, a cardiologist at Boston's Brigham and Women's Hospital.

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