Multicenter study of creatine kinase-MB use: effect on chest pain clinical decision making

To determine whether creatine kinase-MB isomer (CK-MB) levels affect initial physician decisions regarding patients with potential cardiac chest pain.

A prospective, multicenter, observational cohort study was performed at seven university teaching hospital EDs. Hemodynamically stable chest pain patients > or = 25 years old and without ST-segment elevation on their ECGs were observed with one to two sets of CK-MB level determinations obtained three hours apart prior to disposition. The physicians committed to a dichotomous (yes/no) absolute decision regarding the diagnosis of myocardial infarction (MI), need for hospital admission, and need for coronary care unit (CCU) admission both before and after enzyme results were obtained. The physicians ranked the perceived importance of initial history and physical, serial clinical observation, initial ECG, and CK-MB level to their decision making (rank score: 1 = most important, 4 = least important).

Of the 1,042 patients enrolled, 777 (74.6%) were admitted to the hospital. For the 67 MI patients (8.6% of the admissions), changes in absolute decisions about the diagnosis of MI and planned CCU admission were associated with increased CK-MB importance (p = 0.04 and p = 0.02, respectively). Of the 146 patients who had new-onset angina or unstable angina, changes in absolute decisions were not associated with CK-MB importance. No patient who had MI or unstable angina was released from the ED. There were three of 67 (4%) MI patients and one of 146 (1%) unstable/new-onset angina patients initially slated for release home who were admitted to the hospital.

For a minority of the patients who had subsequently proven MI, the CK-MB result helped guide disposition decisions. The CK-MB availability did not adversely impact the disposition of the patients who had unstable or new-onset angina.