Nowhere has the pace of technological change been faster than in the field of imaging. "Fast" CT (computed tomography) made it possible to take images of the heart fast enough to detect calcium in the coronary arteries (calcium score).
Now we have something even faster: the 64-slice CT scanner that is so fast that heart motion and patient movement generally don't blur the image, because almost all people can hold their breath for the 15 seconds it takes to make this image. Large amounts of calcium in the coronary arteries can diminish the clarity of these images, however.
The 64-slice CT scanners first measure the calcium score. Injection of a radio-opaque contrast material into a vein then provides something even more valuable, clear images of plaques in the coronary arteries, much like those obtained with coronary angiography, an invasive procedure in which a catheter is inserted leading from the femoral artery into the heart. In fact, studies have shown that these CT images can be better than angiography of the coronary arteries.
This noninvasive technique will be able to tell many people whether or not they have significant narrowings in their coronary arteries. And 64-slice CT, or even more advanced CT techniques in the future, may largely replace angiography.
There are some disadvantages to 64-slice CT. The intravenous injection of contrast material is invasive and can cause side effects such as allergic reactions and kidney failure.
The dose of radiation is also four to six times greater than the average annual amount a person is normally exposed to and several times greater than during coronary angiography. The imaging technique's cost of approximately $1,000 is not yet covered by insurance.
The problem now is to decide who should undergo 64-slice CT, and there is concern that it will be overused. Cardiologists generally agree that the test is not suitable for a worried but healthy man or woman who has neither symptoms of heart disease nor major risk factors like cigarette smoking or hypertension.
The danger is that a false positive test will lead doctors to order unnecessary additional studies that are also costly and potentially hazardous.
Among the best candidates for a 64-slice CT are people with multiple risk factors, a positive exercise stress test result, or evidence of atherosclerotic disease at other sites.