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May 26, 1997

An Evaluation of a Chest Pain Diagnostic Protocol to Exclude Acute Cardiac Ischemia in the Emergency Department

Author Affiliations

From the Department of Emergency Medicine (Drs Zalenski, Roberts, Rydman, and McDermott), Department of Medicine (Dr Das), and Division of Cardiology (Drs Mendez and El-Khadra), Cook County Hospital, Chicago, Ill; and Center for Health Services Research, School of Public Health, University of Illinois at Chicago (Drs Zalenski, McCarren, Rydman, and Jovanovic); Departments of Emergency Medicine and Medicine, Wayne State University School of Medicine, Detroit, Mich (Dr Zalenski); and Department of Emergency Medicine, College of Medicine, University of Illinois at Chicago (Dr Fraker).

Arch Intern Med. 1997;157(10):1085-1091. doi:10.1001/archinte.1997.00440310049005

Background:  Although accelerated diagnostic protocols are being increasingly used in emergency departments to diagnose acute cardiac ischemia, there have been no prospective evaluations of a chest pain diagnostic protocol with serial determinations of creatine kinase MB isoenzyme and mandatory exercise electrocardiography (ExECG).

Methods:  Prospective cross-sectional study in which chest pain protocol results were compared with final (reference) diagnoses of acute cardiac ischemia (including acute myocardial infarction and unstable angina). Patients in need of hospital admission but at low probability (by a validated algorithm) for acute myocardial infarction were examined for exclusions: known coronary artery disease, cardiac complications, severe comorbidities, or inability to perform exercise testing. A 12-hour diagnostic protocol included serial measurements of creatine kinase MB, ECG, and clinical assessments followed by ExECG for those with negative initial serial testing. Reference diagnoses were established during hospitalization and diagnostic accuracy was assessed.

Results:  The study group of 317 patients was 54% male and 65% black, and had a mean age of 46.6 years; 9.5% had a final diagnosis of acute cardiac ischemia. For this diagnosis, the protocol had a sensitivity of 90.0% (95% confidence interval, 72.3%-97.4%); specificity, 50.5% (95% confidence interval, 44.6%-56.4%); positive predictive value, 16.0%; and negative predictive value, 98.0%. Creatine kinase MB, serial ECGs, and ExECG each made a contribution to improved sensitivity and accuracy, whereas clinical reassessments were less discriminating, as indicated by protocol's receiver operating characteristic curve.

Conclusions:  A chest pain diagnostic protocol achieved high sensitivity and improved specificity over the standard emergency department workup. There were no adverse advents associated with early ExECG.Arch Intern Med. 1997;157:1085-1091