Early detection of coronary calcium can save lives
Experts press for wider use of EBCT as marker
A test that will detect markers for coronary heart disease earlier than any other test — a good thing, right?
Definitely, say some experts.
Probably, says the American Heart Association (AHA).
Electron-beam computerized tomography, or EBCT, measures coronary calcium and has the potential to motivate thousands of patients to save their own lives, says Daniel Berman, MD, FACC, chief of cardiac imaging at Cedars-Sinai Medical Center in Los Angeles, which has one of about 60 of the $1.5 million highly advanced CT scanners in the United States.
EBCT guidelines are changing
The AHA is currently broadening its 1996 guidelines on coronary calcium scans to reflect the latest information: Coronary calcium can be a marker for atherosclerosis. Old guidelines only called for EBCT for patients who complain of chest pain — particularly if the pain is atypical of coronary artery disease (CAD).
Berman thinks that is far too conservative.
"Half of coronary artery disease presents itself as sudden death or irreversible MI," he says. "Saving lives means saving heart muscle by defining the disease earlier than any other test. That’s what the EBCT does."
So far, so good, says William Stanford, MD, an AHA spokesman involved in re-writing the guidelines and a radiology professor and chief of chest and cardiovascular radiology at the University of Iowa College of Medicine in Iowa City.
"The greater the calcium, the greater the chance for a cardiac event. These things are all pretty well accepted," Stanford says.
Stanford says he would not personally oppose an EBCT for any patient with one or more risk factors for CAD:
• obesity
• smoking
• high cholesterol
• high blood pressure
• diabetes
• family history of heart disease
However, the AHA says more outcome data need to be presented to substantiate that coronary calcium is a predictor of cardiac events.
"There is still a considerable amount of controversy," Stanford says.
More studies needed
There certainly is controversy surrounding the procedure for several reasons.
The subject of EBCT is treated at some length in two studies, a letter to the editor and an editorial the Dec. 31, 1998, issue of the New England Journal of Medicine.
While saying EBCT is a "promising" and even "exciting" new diagnostic tool for patients with suspected coronary artery disease "that may contribute to overall risk assessment," the NEJM recommends more studies.
"Before routine clinical use of coronary CT scanning can be recommended for screening of asymptomatic patients or for the evaluation of patients with chest pain . . . more . . . basic studies are required to define the role of calcium in plaque stability and progression . . . and to demonstrate the cost effectiveness of these techniques and their potential impact on cardiovascular outcomes."
That issue of the NEJM features a 149-patient study from the Electron Beam Tomography Research Foundation and Vanderbilt University in Nashville, TN, which shows decreased volumes of atherosclerotic plaque when patients were treated with HMG-CoA reductase inhibitors, and the resulting serum LDL cholesterol levels for at least 12 months after an EBCT showing the need through a calcium-volume score.
A German study published in the same issue shows unevenness in the image quality, but concluded "when image quality is adequate, electron-beam CT may be useful to detect or rule out high-grade coronary artery stenoses and occlusions."
A letter to the editor from two physicians at Walter Reed Army Medical Center in Washington, DC, questions "centers performing electron-beam CT (that) advertise and generate business on the basis of patients referring themselves for the test."
Test isn’t cheap
Berman doesn’t think everyone — even those with risk factors — ought to have an EBCT.
"I think those who are at risk and not doing anything about it should have the screening," he says. "If they’re already doing everything they can, I wouldn’t recommend it."
The test is expensive (about $400 at Cedars-Sinai), and most health care providers will not cover the cost.
Berman believes the key to the value of the EBCT is that it buys time where it counts — on the front end of the disease.
If CAD is caught early enough, Berman says, it can be stopped in its tracks with a combination of lifestyle changes and drug therapy as shown in the Vanderbilt study.
"We know that the very first thing that happens with CAD is the development of fatty streaks in the lining of the arteries. There’s no calcium then — that may not be visible for some years — but over a period of years, the atherosclerosis plaque becomes larger and ends up obstructing the vessel," Berman says.
Motivating patients to change habits
He advocates the EBCT because it can detect occlusion of the artery from virtually zero percent, compared to a variety of other cardiac tests, such as stress ECGs and stress-thallium studies, which may not detect occlusions until the artery is 50% blocked or more, and the opportunity for a good outcome may be impaired or even lost.
An EBCT that shows the early markers for CAD is a powerful motivator for lifestyle changes, Berman argues.
"Just think about it. If you tell somebody their behavior puts them at risk for a disease they may or may not get unless they change their lifestyle, you’re not likely to get much response," Berman says. "But if you tell them they already have the earliest signs of the disease, which can be stopped before it becomes life threatening, they are much more likely to do what they need to do."
While the 1996 AHA guidelines recommend the EBCT only for patients already experiencing chest pain; even then panel members did not have any serious objections to the screening and conceded it "will be used as an early warning system for certain groups because it is simple to do, non-invasive, takes only a few minutes, and is comparable in cost to other tests."
Many insurance companies, including the giant Prudential Health Care in Roseland, NJ, don’t pay for the test because they still question its value, according to Arthur Levin, MD, Prudential’s chief medical officer.
"We don’t cover the EBCT for screening," Levin says. "We don’t really think that just because you show calcium it means anything. There is no consensus about it’s value. The procedure remains controversial."
Levin adds that EBCTs may be covered by his company to evaluate patients complaining of atypical chest pain.
For more information, Daniel Berman can be reached at (310) 855-4224; William Stanford can be reached at (319) 356-3393.
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