NEW YORK, July 02 (Reuters) -- Researchers say a new imaging method can safely rule out coronary artery disease without having to insert a catheter into the heart via blood vessels.
Known as electron beam computed tomography (EBCT), the new "noninvasive" method delivers a detailed image of the moving heart in less than a tenth of a second -- 10 times faster than older CT scanning procedures.
"With a negative scan, you can be very sure that the patient has no coronary artery disease," says cardiologist Dr. Dietrich Baumgart, of the University of Essen in Germany.
According to the researcher and his colleagues, EBCT is good at spotting areas of injury (lesions) in the coronary arteries that contain calcium. Autopsy studies have identified these lesions as being closely associated with the likelihood of a heart attack. The new method can identify calcified plaques even when they are sparse.
"When you find calcification, you can assume the patient has atherosclerosis (narrowing) of the coronary arteries," Baumgart says. "But the new technique can't yet tell us to what degree the artery is narrowed."
The study compared the results of EBCT with two "gold standard" imaging procedures: coronary angiography and the newer intravascular ultrasound (IVUS). Both procedures are highly invasive and riskier than EBCT, in that they require a catheter to be threaded through the blood vessels and into the arteries supplying the heart.
EBCT requires neither catheter insertion nor injection of X-ray dye, which can cause damage to blood vessels or an allergic reaction to the dye. In EBCT, the patient is placed under the scanner and asked to hold his or her breath for about 45 seconds.
The study is said to be the first comparison of all three methods in beating hearts in humans. The imaging methods were used to analyze 267 artery segments in 57 patients.
EBCT was more sensitive at detecting presence or absence of calcification than either of the other methods.
In addition, early signs of atherosclerosis (soft plaques without apparent ultrasound signs of calcification on IVUS) can also be detected by EBCT, but with less accuracy.
"In the individual patient, a negative EBCT finding excludes significant coronary artery disease with excellent accuracy," write the researchers in the Journal of the American College of Cardiology.
But the authors note that EBCT is not yet ready to replace invasive imaging techniques like coronary angiography and IVUS.
"We think it is a good screening tool for those with risk factors for coronary artery disease like high cholesterol levels, or a positive family history (for heart disease)," Baumgarten says.
"For the first time, cardiologists can diagnose coronary atherosclerosis noninvasively," he adds.
But the researcher recommends that patients with "significant calcification" undergo a stress test in order to determine if narrowed coronary arteries are causing "ischemia" -- a cutoff of blood to surrounding heart tissue. And if so, this "would be regarded as an indication for coronary angiography. Thus, unnecessary invasive tests could be avoided," Baumgarten says.
SOURCE: Journal of the American College of Cardiology (1997;30:57-64)
