Serial ECGs are less accurate than serial CK-MB results for emergency department diagnosis of myocardial infarction.
OBJECTIVE
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.


METHODS
Prospective, observational study.


METHODS
University hospital and university-affiliated Veterans Affairs Medical Center EDs.


METHODS
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.


METHODS
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).


CONCLUSIONS
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.
Hedges
J R
JR
Department of Emergency Medicine, Oregon Health Sciences University, Portland.
Young
G P
GP
Henkel
G F
GF
Gibler
W B
WB
Green
T R
TR
Swanson
J R
JR
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002637:Chest Pain / Q000175:diagnosis; D003402:Creatine Kinase / Q000097:blood*; D004562:Electrocardiography; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007527:Isoenzymes; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis*; D009922:Oregon; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors
D007527:Isoenzymes; D003402:Creatine Kinase