Early CK-MB elevations predict ischemic events in stable chest pain patients.

OBJECTIVE

To demonstrate that creatine kinase-MB fraction (CK-MB) elevations within three hours of presentation in the emergency department (ED) are associated with subsequent ischemic events in clinically stable chest pain patients.

METHODS

Prospective cohort study at two university- affiliated teaching hospitals. Participants were consenting ED chest pain patients 25 years old or older without evidence of rhythm or hemodynamic instability (n = 449). Exclusions included ST-segment elevation > or = 0.1 mV in > or = 2 electrocardiogram leads, chest wall trauma, abnormal x-ray studies, and incomplete data collection. Measurements included presenting and three-hour CK-MB levels, presenting ECG, initial clinical impression of coronary care unit need, and clinical follow up. Monitored adverse events included myocardial ischemia necessitating coronary angioplasty or cardiac bypass surgery, recurrent in-hospital myocardial infarction, bradycardia requiring pacing, emergent cardioversion, cardiogenic shock, ventricular fibrillation, and death.

RESULTS

Overall, nine (2%) of 449 patients experienced an ischemic event within the first 48 hours. All nine patients required either coronary angioplasty or bypass surgery. Four (44%) of the nine patients with 48-hour ischemic events had elevated CK-MB levels. Of 23 patients who had complications within one week of ED presentation, seven (30%) had elevated ED CK-MB levels. An elevated CK-MB level was associated with an ischemic event both within 48 hours (risk ratio 9.5; 95% CI 2.7-33.7) and within one week (risk ration 5.2; 95% CI 2.3-11.7).

CONCLUSIONS

An elevated CK-MB level within three hours of ED presentation is associated with a subsequent ischemic event in the clinically stable chest pain patient without ST-segment elevation. However, the ED CK-MB identifies only a minority or otherwise low-risk patients who develop ischemic events; other markers for diagnosing myocardial ischemia in the ED are needed.