Abstract
BACKGROUND It was recently reported that highly elevated plasma activity of the ADP-scavenging enzyme creatine kinase (CK), to >10 times the upper reference limit (URL), is independently associated with fatal or non-fatal bleeding during treatment for ST-segment elevation myocardial infarction (OR 2.6 (95% CI, 1.8 to 2.7)/log CK increase). Evidence indicates that CK attenuates ADP-dependent platelet aggregation. This study investigates whether moderately elevated CK in non-ST-segment elevation acute coronary syndrome (NSTE-ACS) is associated with major bleeding. METHODS The Thrombolysis In Myocardial Ischemia (TIMI) 3B trial compared recombinant tissue-type plasminogen activator (rt-PA) (35-80 mg) with placebo and early catheterisation with conservative management in patients with NSTE-ACS. Main outcomes of the current study are the independent association of peak plasma CK (CKmax) with adjudicated fatal or non-fatal major bleeding (primary) and with combined major bleeding, stroke and hospital death (secondary), with covariables including age, sex, body mass index, systolic blood pressure, creatinine and assignment to add-on rt-PA versus placebo. Discrimination was assessed with C-statistics. RESULTS The study included 1473 patients (66% men, 80% white, mean age 59 years, SE 0.3). CKmax ranged between 15 and 19 045 IU/L (mean (SE), 450 (24) IU/L; two times URL). Major bleeding occurred in 2.0% (mean age 65 (1.3) years; mean CKmax 1015 (319) IU/L; six times URL), and the combined outcome in 4.3% of the patients, adjusted OR per log CK increase, respectively, 3.1 (1.6 to 5.9) for major bleeding and 3.9 (2.5 to 6.1) for the combined outcome; C-index 0.8 for both outcomes. The association between CK and bleeding was independent of the use of thrombolytic therapy. DISCUSSION The presented data add to the existing evidence that proportionate to its plasma activity, the ADP-binding enzyme CK is strongly and independently associated with non-fatal and fatal major bleeding during treatment for NSTE-ACS. CK might increase the accuracy of prediction models for major bleeding in patients with NSTE-ACS. TRIAL REGISTRATION NUMBER NCT00000472.
