Multislice Computed Tomography Has Potential to Offer Accurate, Safer
Method For Detecting Coronary Artery Disease

CHICAGO - Multislice computed tomography appears to provide high
accuracy for detecting coronary artery disease and may represent a
useful complement to conventional coronary angiography, according to a
study in the May 25 issue of JAMA.

Conventional invasive coronary angiography is currently the diagnostic
standard for clinical evaluation of known or suspected coronary artery
disease (CAD), according to background information in the article. The
risk of adverse events is small, but serious and potentially
life-threatening events may occur, including arrhythmia, stroke,
coronary artery dissection, and access site bleeding (total
complication rate, 1.8 percent; death rate, 0.1 percent). Furthermore,
angiography catheterization induces some discomfort and mandates
routine follow-up care. Guidelines recommend that conventional invasive
diagnostic angiography be restricted to stringent clinical indications.

A recently developed procedure that may potentially complement invasive
coronary angiography is multislice computed tomography (MSCT), which
may achieve a high level of reliability and accuracy in the
visualization of the coronary arteries. MSCT is a sophisticated x-ray
imaging technique, in which a CT tube and multiple layered detector
rows rotate around the patient, taking numerous images of the body in
seconds. A computer processes this information into three-dimensional
images composing volumetric representations of anatomy. The coronary
arteries can be extracted from these images and are presented in
arbitrarily oriented sectional cuts. This procedure eliminates much of
the risk and discomfort associated with invasive coronary artery
catheterization, although it retains the risks inherent in radiation
exposure and use of contrast agents.

Martin H. K. Hoffmann, M.D., of University Hospital, Ulm, Germany and
colleagues assessed the diagnostic accuracy of 16-slice MSCT scanning
vs. invasive coronary angiography in a large group of patients with
known or suspected CAD. The study, which included 103 patients (average
age, 61.5 years), was conducted from November 2003-August 2004. The
patients underwent both invasive coronary angiography and MSCT using a
scanner with 16 detector rows.

The researchers found that compared with invasive coronary angiography
for detection of significant lesions (greater than 50 percent stenosis
[narrowing]), segment-based sensitivity, specificity, and positive and
negative predictive values of MSCT were 95 percent, 98 percent, 87
percent, and 99 percent, respectively. Quantitative comparison of MSCT
and invasive coronary angiography showed good correlation, with MSCT
systematically measuring greater-percentage stenoses. Per-patient based
analysis indicated high discriminative power to identify patients who
might be candidates for revascularization.

"In conclusion, we found that MSCT shows reasonably high accuracy for
detecting significant obstructive CAD when assessed at a patient level.
At its current stage of development, it may therefore be used to
substantially reduce likelihood of clinically important CAD in patients
with suspected disease. The appeal of MSCT compared with conventional
coronary angiography is that it is noninvasive, avoiding most
catheter-associated risks and discomforts with the exception of
exposure to iodinated contrast agents and radiation. With rapidly
improving technology, MSCT may well evolve from a useful complement to
invasive angiography to a clinically viable alternative," the authors
write.

(JAMA. 2005;293:2471-2478. www.jamamedia.org)

Editor's Note: This study was funded by the State Government of
Baden-Wuerttemberg, Germany. The computed tomography equipment was
partially provided by Philips Medical Systems, Best, the Netherlands,
on the basis of a beta-site contract.

Editorial: Noninvasive Coronary Angiography - Hype or New Paradigm?

In an accompanying editorial, Mario J. Garcia, M.D., of the Cleveland
Clinic Foundation, comments on the findings by Hoffmann et al.

"Despite these promising results, several important limitations of MSCT
must be considered. First, MSCT requires ionizing radiation," Dr.
Garcia writes. "This dose [in this study] is equivalent to 2 to 3 times
the dose typically administered during a diagnostic invasive angiogram.
Although the long-term risks associated with this level of radiation
exposure are relatively low, it raises a concern about repetitive use
or use in younger individuals and women of childbearing age."

"Second, the extent and severity of coronary calcifications in the
population studied by Hoffmann et al is not known definitively."

"Despite [these and other limitations], there is an important segment
of the population at risk for heart disease in whom MSCT angiography
could provide coronary anatomic information with sufficient diagnostic
quality. Indeed, MSCT may offer another advantage over conventional
angiography, which is the potential ability to detect and quantify
atherosclerotic plaques in the coronary vessel walls. Nevertheless, in
the absence of outcome and cost analysis studies, it is not yet clear
how MSCT coronary angiography should be integrated in the clinical
practice. Should it be used as a first test for the evaluation of chest
pain or as a complementary test in patients with equivocal stress test
results? In either case, adequate patient selection will be critically
important."

". the growing enthusiasm for MSCT in the community must be matched
with adequate training, proper credentialing and, above all,
appropriate utilization," Dr. Garcia concludes.

(JAMA. 2005;293:2531-2533. www.jamamedia.org)

Editor's Note: Dr. Garcia receives institutional research funding from
Philips Medical Systems.