Electron Beam Ct - Diagnosing Heart Disease: Heart Disease

Content provided by the Faculty of the Harvard Medical School

Electron beam CT

A different technology, electron beam CT, takes pictures with a rotating beam of electrons that circles the body far faster than an x-ray camera. The resulting images of the heart and arteries are clearer than those from a standard CT scan. More important, electron beam CT can precisely measure the amount of calcium in the coronary arteries. This is useful because normal arteries usually don't contain calcium, while arteries chock-full of it are usually clogged with atherosclerotic plaque. Simply put, the more calcium, the more atherosclerosis — and the greater the chances of having a heart attack or stroke.

But the test isn't perfect. First, most Americans have some degree of atherosclerosis and therefore some calcium deposits. That means that even people who have only minimal atherosclerosis, and a low risk for heart attack, are likely to have an abnormal electron beam CT scan. Yet the results of the scan could frighten them into seeking unnecessary medical procedures. Second, test results aren't always accurate. Some people with high calcium scores don't have atherosclerosis. Low scores are reassuring, but they don't guarantee freedom from heart disease. That's because relatively calcium-free pockets of cholesterol embedded in the lining of coronary arteries can still break open and trigger a heart attack or stroke.

In 2000, a panel assembled by the American College of Cardiology and the American Heart Association decided against recommending the test for diagnosing coronary artery disease. After analyzing the available data, the panel concluded that electron beam CT had a higher rate of false positives than other noninvasive tests and that it provided no additional information. More recent studies indicate that electron beam CT does add some information to the ability of doctors to predict risk for heart attack, but no study has shown yet that this information can actually change treatment in ways that improve patients' outcomes. For this reason, professional guidelines stop short of recommending the routine use of electron beam CT, and because it isn't a standard heart disease screening test, it generally isn't covered by insurance. Studies are under way to find out whether the test might be used to help prevent heart disease, and specifically, to see whether people with high calcium scores benefit from lipid-lowering treatment.

Last updated:	May 03, 2007