**4. Anatomical evaluation**

Multidetector computed tomography (MDCT) provide noninvasive evaluation of coronary anatomy and atherosclerosis. Due to the high negative predictive value of coronary computed tomography angiography (CCTA), evidence suggests that CCTA is useful in patients with low to moderate risk of NSTEMI where a normal scan excludes CAD. When compared with the standard care (observation, serial enzymes followed by stress testing) for low-risk patients, CCTA reduced time to diagnosis, reduced length of emergency department stay, and had similar safety [60]. CCTA had high negative predictive values to exclude ACS and excellent outcome in patients presenting to the emergency department with low to intermediate pre-test probability for ACS and a normal coronary CT angiogram [61]. CCTA was proven

**Figure 2.** Myocardial nuclear perfusion scan showing anterior, lateral and inferior reversible scan. Coronary angiogram confirmed three vessel disease.

beneficial in the triage of low- to intermediate-risk patients presenting with acute chest pain to emergency departments without signs of ischemia on ECG and/or inconclusive cardiac troponins. At 6 months follow-up, there were no difference in the incidence of MI, post discharge emergency department visits or rehospitalizations, and no deaths in comparison to traditional management. Also, there were reduction in the cost and length of stay associated with MDCT [60, 62–65]. But there was an increase in the use of invasive angiography [65]. CCTA is not indicated for patients with high-risk features and it is not useful in patients with known CAD [66]. Other factors limiting CCTA include severe calcifications and tachycardia. CT imaging can effectively exclude other causes of acute chest pain that, if untreated, are associated with high mortality, namely pulmonary embolism, aortic dissection and tension pneumothorax [67].
