For the identification of either symptomatic individuals or asymptomatic individuals with “high” cardiovascular risk who would benefit from more aggressive preventive measures, non-invasive diagnostic tests like treadmill exercise test and myocardial perfusion scintigraphy are recommended. The prognostic value of myocardial perfusion scintigraphy in symptomatic coronary artery disease patients is obvious, as demonstrated in the COURAGE trial. It has been shown that the absence of inducible ischemia in myocardial perfusion scintigraphy is associated with a very low rate of major cardiovascular events in the next 5 years. However, for asymptomatic individuals, the use of myocardial perfusion scintigraphy as first-line testing modality for risk stratification is not recommended in primary prevention subjects at low to intermediate cardiovascular risk. The only exception is possibly first-degree relatives of patients with premature coronary artery disease. In fact, myocardial perfusion scintigraphy has not been proved to significantly improve clinical outcomes of primary prevention subjects in prospective controlled studies.

　　Computed tomography (CT), particularly multirow detector CT (MDCT), is quickly evolving into a remarkably useful imaging tool for evaluating the severity and characters of coronary artery disease (CAD). In general, segment-based positive and negative predictive values of MDCT in detecting diameter stenosis ?50% are 85-90% and 95-99%, respectively. However, calcium can obscure the vessel lumen and make it difficult to determine the severity of coronary stenoses. Coronary CTA may not be done if calcium score is greater than 1000 units and diffuse.

　　American guidelines for the use of coronary CTA were published in 2010. The most widely agreed indication is the evaluation of symptomatic patients with a low to intermediate pre-test probability of CAD who present with no electrocardiographic or biomarker evidence of acute ischemia. In these patients, a normal CTA can reliably exclude obstructive CAD given its excellent negative predictive value. It should be emphasized that assessment of coronary calcium score alone is not sufficient to exclude CAD.

　　The other indications for coronary CTA include asymptomatic patients with high global cardiovascular risk and patients who have equivocal results with conventional stress testing, including discordance between symptoms, ST segment analysis, and wall motion or perfusion. A normal coronary CTA can obviate the need for invasive angiography. One study showed that approximately two-thirds of patients with equivocal stress tests have no obstructive CAD by coronary CTA, thus avoiding further expenditure.