Hypothesis:
Serial creatine kinase-mb (ck-mb) levels provide more accurate predictive information regarding myocardial infarction than serial ecgs in emergency department patients with chest discomfort and no st-segment elevation on the initial ecg.
Design:
Prospective, observational study.
Setting:
University hospital and university-affiliated veterans affairs medical center eds.
Participants:
Two hundred sixty-one patients 30 years or older with chest discomfort warranting an ecg and consenting to observation. exclusions included hemodynamic or rhythm instability and st-segment elevation of 0.1 mv or more in two or more electrically contiguous leads at presentation.
Measurements:
Ecgs were obtained at presentation and three to four hours after presentation. significant serial ecg changes sought on comparison of initial and three- to four-hour ecgs were 0.05 mv or more st elevation or depression, q-wave development, or t-wave inversion changes in two or more electrically contiguous leads. ck-mb levels were obtained at presentation and hourly for three hours (positive level, 8 or more ng/ml). myocardial infarction was determined by record review and was based on independent ck-mb measurements.
Results:
Twenty-eight (11%) patients were diagnosed with a myocardial infarction. thirty-eight (15%) patients had a serial ecg change. eleven of the myocardial infarction patients (39%) had a serial ecg change compared with 27 (12%) of the non-myocardial infarction patients (p < .001). sensitivities and specificities of a serial ecg change versus serial ck-mbs for myocardial infarction were 39% versus 68% (sensitivity) and 88% versus 95% (specificity), respectively. serial ck-mbs were more accurate than a serial ecg change for predicting myocardial infarction (p < .03).
Conclusion:
Serial changes in ecgs during a three- to four-hour interval were associated with the diagnosis of myocardial infarction but were infrequent and less accurate than serial ck-mb levels obtained for the same interval.