COMBINED CARDIAC MARKER APPROACH WITH ADJUNCT 2-DIMENSIONAL ECHOCARDIOGRAPHY TO DIAGNOSE ACUTE MYOCARDIAL-INFARCTION IN THE EMERGENCY DEPARTMENT

Study objective: To evaluate a combined cardiac marker approach with a djunct two-dimensional echocardiography in diagnosing acute myocardial infarction (AMI) in the emergency department. Methods: This prospecti ve, cohort study enrolled 190 patients aged 18 years and older who pre sented to the ED of a county teaching hospital and were admitted with chest pain suggestive of AMI. A standardized history and physical exam ination were performed. Serum sampling for myoglobin and creatine kina se-MB (CK-MB) was done at the time of presentation (time 0) and 3 hour s later (time 3 hours). An echocardiographic study was obtained, and a left ventricular wall motion score was derived. Results: Using World Health Organization criteria, 21 patients (11.2%) with AMI were identi fied. The serum markers were found to be clinically and statistically different between AMI and non-AMI groups at both time 0 and time 3 hou rs. Receiver operator characteristic curves were used to determine a ' 'positive'' myoglobin level at 88.7 ng/mL or higher at either time poi nt, and a ''positive'' CK-MB level at 11.9 ng/mL or higher; these were used as the optimal cutoff values to predict AMI in the ED. Serum myo globin was a more sensitive marker (90.5%) than CK-MB (81.0%). However , CK-MB was more specific (99.4%) than myoglobin (88.4%). A combinatio n of both tests, which was rated positive if either test was positive, was a superior predictor overall, with a 100% capture rate of AMI pat ients and a 91.2% specificity. No significant difference in echocardio graphic scores was appreciated in the AMI group compared with the non- AMI group (16.9+/-1.5 versus 15.3+/-.5, respectively; P=.3252). Conclu sion: Serum myoglobin shows greater sensitivity but is less specific t han CK-MB in the early detection of AMI. Use of a combination of both rapid assays during a 3-hour time period in the ED appears to be super ior to use of either enzyme assay alone. Two-dimensional echocardiogra phy does not appear to be helpful in diagnosing AMI in the ED.