Level 2: Mid-level evidence

Most patients visiting emergency departments (EDs) with symptoms consistent with acute coronary syndrome (ACS) are likely to have less serious conditions, but current diagnostic protocols are costly, lengthy and tend to require hospital admission.

The Asia-Pacific Evaluation of Chest Pain Trial (ASPECT) evaluated a two-hour accelerated diagnostic protocol to rule out ACS in a cohort of 3,582 patients with chest pain presenting to EDs in nine countries (Lancet. 2011;377:1077-1084).

Patients were evaluated by thrombolysis in myocardial infarction (TIMI) score, ECG, and a point-of-care triple biomarker panel at presentation and again at two hours. The TIMI score is comprised of seven factors, with one point given for each: aged >65 years, presence of at least three coronary artery disease risk factors (family history, hypertension, diabetes, hypercholesterolemia, current smoker), prior coronary stenosis >50%, ST-segment deviation on ECG at presentation, at least two anginal events in prior 24 hours, use of aspirin in prior seven days, and elevated serum cardiac markers, including creatine kinase MB or cardiac troponin (JAMA. 2000;284:835-842). The biomarker panel included troponin, creatine kinase MB (also part of the TIMI score) and myoglobin.

Patients were classified as having low risk for major cardiac events if they had all three of the following: TIMI score of zero, no evidence of ischemic changes on the ECG, and normal values for all biomarkers at zero and two hours after arrival. Major cardiac events included death, cardiac arrest, emergency revascularization, cardiogenic shock, acute MI, and ventricular arrhythmia or high-degree atrioventricular block requiring intervention.

Major cardiac events occurred in 11.8% of patients overall. A total of 370 patients were classified as low-risk, with three patients suffering major events in analysis of 352 patients who were followed for 30 days (18 patients were lost to follow-up, although they were reported to have had no in-hospital major cardiac events). For identifying low-risk patients, the accelerated protocol had 99.3% sensitivity and 99.1% negative predictive value. Specificity was 11% and positive predictive value was 12.9%. Of the individual components of the protocol, TIMI score = 0 had the highest sensitivity (96.7%).

Alan Ehrlich, MD, is an assistant clinical professor in family medicine at the University of Massachusetts Medical School in Worcester.