Medically Reviewed by Louise Chang, MD on November 05, 2007 From the WebMD Archives
Nov. 5, 2007 (Orlando, Fla.) — High-tech heart scans may help some people to avoid invasive, and sometimes unnecessary, procedures to check for blockages in the coronary arteries, researchers say.
In a new study, the sophisticated 64-slice computed tomography coronary angiography scan proved nearly as accurate as standard cardiac catheterization at spotting blocked coronary arteries.
The scans won’t replace cardiac catheterization, also known as coronary angiography, but they can help doctors rule out people who can skip the more invasive procedure, says researcher Julie Miller, MD, assistant professor of medicine at Johns Hopkins Hospital in Baltimore.
Studies suggest that as many as one in four of the 1.3 million cardiac catheterization procedures performed each year in the U.S. may be unnecessary, she says.
CT Heart Scans Quick, Noninvasive
Early detection of blockages is critical to preempting a heart attack, allowing time for drug therapy, angioplasty, or heart bypass surgery to be used to keep arteries open.
Cardiac catheterization is the gold standard for evaluating blood vessel obstructions. In the procedure, contrast material — a substance that makes it easier to see in an X-ray — is injected through the catheter. Then an X-ray is taken of the area to look for blockages.
While it sounds like a mouthful, the 64-slice computed tomography coronary angiography scan is rapidly joining the health lexicon. It’s a type of CT scan that gives doctors a detailed look at the coronary arteries, which supply blood to heart muscle.
The technique is quick, producing pictures within five to 10 seconds, compared with 30 to 45 minutes for catheterization, Miller says. It’s noninvasive, with potentially less risk and discomfort than catheterization, which often requires sedatives and sometimes a night in the hospital.
The potential complications of catheterization, while extremely rare, include infection, heart attack, and stroke, Miller says.
CT Heart Scans Relatively Accurate
The study involved 291 men and women over age 40 who were scheduled to have catheterization to check for blocked arteries. Each underwent a 64-CT scan prior to catheterization.
The findings were presented at the American Heart Association’s Scientific Sessions 2007.
After a year, Miller says that in spotting blockages, the results of the heart scans matched up with the catheterization results 90% percent of the time.
However, the CT scans were not very good at locating exactly which vessel was blocked, the study showed.
How Will Doctors Use CT Heart Scans?
“This is a very positive study in the sense it showed the effectiveness of the 64-slice CT to identify people with coronary artery disease,” Timothy Gardner, MD, tells WebMD. Gardner is an American Heart Association spokesman and a heart surgeon at Christiana Care Health Services in Wilmington, Del.
“The question that still remains is how it fit into the diagnostic workup of the patient without adding an additional test along the way,” he says.
Miller tells WebMD that the new scanners, which are four times faster than traditional 16-slice CT scans, may be a good alternative to exercise stress tests to look for coronary artery disease in some patients.
Exercise stress testing generally cannot safely be performed on a frail, elderly person, she says.
Also, “this can be an additive test for people who have equivocal results on a stress test but whose doctors don’t think there is anything wrong. Right now, they are referred for catheterization, but the CT scan could help avoid that,” Miller says.
CT Heart Scans’ Limits
CT scans are not for everybody. They fail to produce good images in people with a lot of calcium deposits in their artery plaque, Gardner says. Like sludge in a drain, the calcium interferes with a clear picture.
In fact, people with a lot of calcium deposits — who accounted for about one in four of people originally recruited — were excluded from the study.
Raymond J. Gibbons, MD, a past American Heart Association president and the Arthur and Gladys D. Gray professor of medicine at the Mayo Clinic in Rochester, Minn., tells WebMD that he’s also concerned about cancer risks.
A study published earlier this year showed that radiation from the scan may increase lifetime cancer risk, particularly in younger women.
All the doctors stressed that CT scans should not be used to screen for plaque in people who do not have symptoms of coronary artery disease.
The CT scan, including the doctors’ fee, costs about $1,000, according to Gardner. Angiography carries a price tag of $2,500 and up, he says.
But angiography is generally covered by insurance, while Medicare and other insurers are still evaluating whether to pay for the scans, Gardner notes.
Toshiba, which makes the CT scanner used in the study, provided funding for the research.
