Complementary roles of coronary calcium scanning and myocardial perfusion SPECT.

The assessment of coronary artery calcium (CAC) by electron beam tomography (EBT) or multidetector spiral computed tomography (CT) and the evaluation of myocardial perfusion and function by use of myocardial perfusion single photon emission computed tomography (SPECT) (MPS) are both valuable in the noninvasive assessment of patients with suspected coronary artery disease (CAD). CAC provides unique anatomic information regarding coronary atherosclerotic burden, whereas MPS assesses the physiologic significance of coronary stenosis and provides information regarding stress-induced ischemia. These fundamental differences in the measurements result in the techniques being highly complementary. Many reports have demonstrated that EBT testing can be of clinical value by providing a marker of atherosclerotic burden in patients with risk factors for CAD but not yet clearly needing aggressive medical therapy. Frequently, this occurs at a stage of atherosclerosis before there is a stenosis, a time at which the results of stress testing would usually be negative. MPS has proved useful in risk stratification and in identifying patients who require coronary angiography for purposes of possible coronary revascularization. Although several reports have shown that CAC is also useful in risk stratification, ischemia determined by MPS provides unique information regarding the likelihood of benefit from a revascularization procedure. The wide use of MPS, coupled with the increasingly recognized utility and growing availability of CAC scanning, raises a new clinical problem for clinicians as to how to integrate CAC scanning with conventional stress imag-