A 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. 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.
A study published Thursday in the Lancet 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.
For the study the 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 build-up 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.
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 build-up, 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, pre-diabetes 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 a sub-study 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. JUPITER found that patients with normal cholesterol benefited from treatment with statins when they had elevated levels of inflammation, as measured by CRP. Patients in the study with normal cholesterol and elevated CRP who took statins had fewer heart attacks than patients with the same characteristics who did not take the drugs. Based on the findings, it was estimated that an additional 6.5 million adults in the U.S. might benefit from treatment with statins.
But the new study suggests that far fewer patients would actually benefit. “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.
Cardiologist Robert Bonow, who is a past president of the American Heart Association (AHA), says until such a trial is done it will not be clear if coronary calcium screening influences treatment and changes outcomes. Bonow, who is a professor of medicine at Chicago's Northwestern Feinberg School of Medicine, says one potential downside to the screening test is that it might lead to even more testing and potentially unnecessary invasive treatments like angioplasty. “It is human nature to want to do something about a blockage when it is found, even if that blockage is not causing any symptoms,” he says.
Commenting on the study, cardiologist Dr. Vijay Nambi, an assistant professor at Baylor College of Medicine, said that most insurance companies don't cover the calcium tests, which cost in the range of $200-$400. “Sometimes people have to pay for it out of pocket,” said Nambi, who thinks it's a useful test. “It helps physicians in a lot of respects.” Test results can also help patients make decisions when they're worried about taking anticholesterol drugs, Nambi added.