Analysis of creatine kinase, CK-MB, myoglobin, and troponin T time-activity curves for early assessment of coronary artery reperfusion after intravenous thrombolysis

Abstract

Background: Thrombolysis has become the standard therapeutic approach in patients with acute myocardial infarction. To identify patients who may benefit from early invasive procedures, reliable noninvasive assessment of success or failure of thrombolytic therapy is mandatory.

Methods and results: In a prospective study in 63 consecutive patients undergoing thrombolysis for their first myocardial infarction, serial measurements of creatine kinase (CK), its isoenzyme CK-MB, myoglobin, and troponin T were done to determine their value for noninvasive prediction of coronary artery patency. Blood samples were drawn every 15 minutes during the first 90 minutes, every 30 minutes during the first 4 hours, every 4 hours during the first 24 hours, and every 8 hours during the first 72 hours. The perfusion status of the infarct-related artery was assessed angiographically 90 minutes after initiation of thrombolysis. For each marker, time to its peak concentration and its early initial slope (start of thrombolysis to 90 minutes thereafter) were determined. Areas under receiver operator characteristic (ROC) curves were 0.83, 0.76, 0.82, and 0.80 for maxima of CK, CK-MB, myoglobin, and troponin T, respectively (p = NS by univariate Z test). The corresponding values for early slopes of CK, CK-MB, myoglobin, and troponin T were 0.79, 0.82, 0.89, and 0.80 (p = 0.23 for comparison between myoglobin and CK-MB; p = 0.07 between myoglobin and CK). Sensitivity, specificity, and positive and negative predictive values regarding noninvasive prediction of coronary artery patency after 90 minutes were 80%, 82%, 95%, and 61% for time to CK maximum; 91%, 77%, 91%, and 77% for time to myoglobin maximum; 87%, 71%, 89%, and 67% for early CK slope; and 94%, 88%, 94%, and 82% for myoglobin slope, respectively. When myoglobin slope was assessed together with other clinical reperfusion markers (resolution of chest pain or ST segment elevation, occurrence of reperfusion arrhythmias) by logistic regression analysis, only the myoglobin slope was an independent predictor of coronary artery patency (p < 0.0001).

Conclusions: With regard to noninvasive prediction of coronary artery patency after thrombolytic therapy, measurement of the early initial slopes of the serum markers within only 90 minutes after the initiation of therapy is as accurate as the determination of the time to their peak concentration. Compared with the other markers examined, myoglobin appears to have advantages because of its earlier rise, yielding a better negative predictive value and a higher area under the ROC curve for determination of its early initial slopes.