Many coronary arteries with significant atherosclerotic plaque per multi-slice computed tomography deliver enough blood that there is no evidence of tissue ischemia with myocardial perfusion imaging, according to an article in the December 19 issue of the Journal of the American College of Cardiology.

The Dutch study, led by Jeroen J Bax, MD, PhD, Leiden University Medical Center, examined whether coronary arteries with significant plaque per multi-slice computed tomography also have evidence of tissue ischemia with myocardial perfusion imaging. The latter technique uses single-photon emission computed tomography to detect metabolic changes associated with ischemia.

Researchers enrolled 114 adults at moderate risk for coronary artery disease due to chest pain or risk factors, but with no prior history of disease. Patients underwent both noninvasive imaging procedures within 30 days of each other. Multi-slice computed tomography was performed using 16- and 64-slice technique in 28 and 86 patients, respectively. Myocardial perfusion imaging was performed using either physical exercise or pharmacological stress combined with a Tc-99m imaging agent. Invasive coronary angiography was also performed in a subset of 58 patients, confirming previous studies that the agreement between tomographic technique and invasive coronary angiography was excellent.

Only 45 percent of patients who had atherosclerosis with computed tomography were also found to have ischemia with myocardial perfusion imaging. In fact, only half of the patients who were shown to have obstructive coronary artery disease -- defined as fifty percent or more narrowing -- were shown to have tissue ischemia.

“The study shows that there’s a big discrepancy between atherosclerosis and ischemia,” said Bax. “These two different types of coronary imaging tests are clearly looking at different, yet complementary aspects of coronary artery disease. Multi-slice computed tomography detects atherosclerosis, while myocardial perfusion imaging identifies ischemia.”

“Future studies are needed on how to apply both techniques in the clinical setting in patients with intermediate likelihood of coronary artery disease,” Bax added.

Sharmila Dorbala, MD, Divisions of Nuclear Medicine/PET and Cardiovascular Imaging, Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School in Boston was not connected with the research but agreed that multi-slice computed tomography deserves further study. Dr. Dorbala wrote an editorial that will accompany publication of the new research.

In an accompanying editorial, Dorbala wrote "How this new test, MSCT fits into our existing clinical paradigm is not completely known. The findings of this study are important and add to the growing evidence that MSCT detects coronary plaque but not ischemia. Thus, relying on this test alone for making decisions about coronary revascularization could result in unnecessary revascularization procedures and higher costs without clear benefits to patients. The results of this and other similar studies will be important in guiding our decisions about management of patients with intermediate likelihood of coronary artery disease.”