Computed tomography coronary calcium screening and myocardial perfusion imaging

Cardiac computed tomography (CT) has seen an exponential increase in interest as applications expanded from identification of coronary artery calcification to noninvasive coronary angiography and, more recently, identification of soft and noncalcified plaques. The interest arises from the well-known fact that cardiovascular disease remains the most prevalent cause of death in the Western hemisphere and the fact that in a large proportion of patients the initial event is either sudden death or a disabling myocardial infarction or stroke. Although traditional risk factors are extremely helpful in determining risk in a population, the prognostic ability of risk factors alone in the individual patient is limited. Hence, researchers have turned their attention to noninvasive modalities to image the atherosclerotic plaque in its preclinical stages, hoping to better address this ailment at its inception and change the natural history of the disease. Measurements of coronary artery calcium (CAC) serve as a quantitative reflection of the severity of coronary artery atherosclerosis, and greater calcium burdens correlate with more advanced disease. Indeed, CAC has been shown to add prognostic value to traditional risk factors in patients at intermediate risk, and in this group of patients, it is most cost-effective. Furthermore, CAC measurements providing an assessment of coronary atherosclerotic plaque burden appear to be complementary to myocardial perfusion single photon emission computed tomography that offers information regarding inducible ischemia. In this manner, a better assessment of risk in a patient suspected of harboring preclinical or early coronary artery disease can be achieved. In this article we review the most relevant literature regarding the utilization of CAC testing as a tool to refine risk assessment and use several case studies to exemplify the combination of CT imaging and functional myocardial perfusion studies, which may provide a better identification of patients in need of aggressive medical therapy and those needing invasive assessment for possible coronary revascularization.