Abstract 6102: Integration of Non-Contrast Cardiac Computed Tomography and Stress Myocardial Perfusion Imaging in the Emergency Department: Identifying Which Patients with Chest Pain Can be Safely Discharged Home

Abstract

Over 5 million emergency department (ED) visits occur annually for evaluation of chest pain. A rapid simple imaging algorithm is needed to identify patients with noncardiac chest pain so as to avoid unnecessary hospital admission. We conducted a prospective trial in 1031 low risk patients (60% women; mean age 54±13 years) admitted through the ED to our chest pain unit who had no prior cardiac history, a nondiagnostic ECG for ischemia, and a normal initial troponin. All patients had stress myocardial perfusion imaging (SPECT) with a coronary artery calcium score (CACS) by noncontrast cardiac computed tomography (CT) within 24 hours. Mean patient follow-up was 7.4±3.3 months. SPECT and CT studies were interpreted independently and the CACS quantified as an Agatston score. The mean TIMI risk score was 1.5±0.7. Cardiac events occurred in 29 patients (2.8%): acute myocardial infarction (N=4) or an acute coronary syndrome (ACS, N=21) during admission; or ACS following hospital discharge (N=4). Abnormal SPECT and cardiac events significantly increased with CACS (p<.001), with over a 40-fold increase in event rates for patients with a CACS>400 vs 0(Table ). Only 5 (0.8%) patients with CACS=0 had an abnormal SPECT and none had significant coronary artery disease by angiography. The 2 patients who had a CACS=0 and a cardiac event during their hospitalization both had a normal gated SPECT and no subsequent event in follow-up. The sensitivity of an abnormal CT was significantly higher than an abnormal SPECT for identifying patients with events (93% vs 65%, p<.01, respectively). A sizeable percentage (61%) of our low risk patient cohort had CACS=0 by CT which predicted both a normal SPECT and an excellent short-term outcome. Our data support that low risk patients with chest pain and a CACS=0 can be safely discharged home from the ED, with SPECT reserved for those with an abnormal CT result.