Cardiac CT for acute chest pain in the emergency department: advantages of prospective triggering

Coronary CT angiography (CCTA) is emerging as a powerful tool for the diagnosis and characterization of coronary artery disease. In the emergency department (ED) setting, the high negative predictive value of CCTA has been shown to reduce the length of stay and the cost of care in the evaluation of patients at low and intermediate risk for an acute coronary syndrome (ACS). In addition, CCTA and triple-rule-out protocol CT examinations which simultaneously evaluate the coronary arteries, aorta and pulmonary arteries, have the potential to diagnose not only significant atherosclerotic coronary artery disease (CAD) and coronary artery anomalies, but noncoronary etiologies of chest pain, including pulmonary embolism, aortic dissection, infection, pleural and pericardial disease. Caution has been raised about the widespread use of CCTA in this setting, particularly given the prevalence of repeat ED visits for chest pain, due to the radiation exposure associated with retrospectively-gated CCTA. However, the recent development of prospectively-triggered coronary artery CTA makes the ED evaluation possible with a substantially lower radiation exposure to the patient. Although most studies of CCTA to date are performed with retrospective ECG gating, early reports on prospectively triggered CCTA demonstrate equivalent image quality and accuracy when compared to studies acquired with retrospective ECG gating.