Clogged coronary arteries may not necessarily lead to poor blood perfusion to the heart muscle, a recent study that compares multislice CT with stress myocardial perfusion imaging confirms. Nor do test results that indicate good blood circulation to the heart always correlate to a low degree of coronary artery blockage.

Research led by Dr. Jeroen J. Bax of the University of Leiden in the Netherlands compared the relationship between results obtained from the two imaging procedures in 114 male and female patients with an intermediate pretest likelihood of coronary artery disease. The investigators also performed invasive coronary angiography in a subset of patients as an additional comparison. CT and invasive angiography test directly for the disease, whereas myocardial perfusion imaging detects the physiological manifestation of the malady -- ischemia.

Of patients whose CT was normal, 90 percent also demonstrated normal perfusion -- results that aligned well with the researchers’ expectations. Only 45 percent of patients who had abnormal CT, however, had correspondingly abnormal myocardial perfusion imaging results. Even patients with obstructive coronary artery disease -- defined as greater than 50 percent luminal narrowing -- showed normal perfusion in 20 out of 40 cases. Conversely, 52 percent of individuals with no demonstrable ischemia exhibited abnormal CT results. Invasive coronary angiography results generally corroborated those of the multislice procedure.

The outcome did not completely surprise the team. Preliminary investigations by other scientists point to the poor correlation between atherosclerosis and ischemia. But it indicates that CT allows detection of coronary artery disease at a significantly earlier stage than perfusion imaging, and that it might serve as a first test for patients with a mid-to-high risk of the disease. Other groups will have to conduct larger studies before clinicians can draw a definitive conclusion about the role of the high-resolution yet radiation-intensive procedure.

The Journal of the American College of Cardiology published the team’s results on Dec. 19.