Rate of disappearance of creatine kinase-MB after acute myocardial infarction: Clinical determinants of variability

The apparent rate of disappearance (K_d) of creatine kinase (CK)-MB is used in the calculation of the size of acute myocardial infarction (AMI), but littie is known about the determinants of variability of this parameter. We therefore evaluated the relationship between clinical characteristics and apparent K_d in 328 patients with AMI without evidence of recurrent infarction. Patients with a history of cigarette smoking within 6 months had higher rates of disappearance of CK-MB, but no relationship was found between renal function and apparent K_d. Slower rates of disappearance of CK-MB were correlated with longer times from the onset of symptoms to peak CK-MB value (p < 0.001), while higher peak CK-MB levels were not correlated with apparent rates of enzyme clearance. Decreased rates of disappearance of CK-MB were found in patients who had congestive heart failure during or after the hospitalization (both p < 0.05), and who died during the hospitalization or during study follow-up (both p < 0.05). Slower rates of disappearance were also significantly correlated with lower ejection franctions on radionuclide ventriculography at 10 days (p < 0.001) and at 3 months (p < 0.05) after AMI. These data suggest that patients with slower rates of disappearance of CK-MB may have poorer prognoses, perhaps reflecting continuing necrosis and enzyme release from jeopardized myocardium.