Background: The universal definition of myocardial infarction specifies creatine kinase-MB fraction (CKMB) or troponin values more than 3 times the 99th percentile of the upper reference limit as diagnostic after percutaneous coronary intervention, with a preference for the use of troponin.
Methods: Outcomes of 4930 patients with elective coronary stent placement between July 1, 2004, and September 30, 2007, as part of the EVENT (Evaluation of Drug Eluting Stents and Ischemic Events) registry were analyzed to test the association between 1-year mortality and postprocedure elevation of either CKMB or troponin. All values were normalized to the individual clinical center myocardial infarction diagnostic levels.
Results: Myocardial infarction occurred in 7.2% of patients by the CKMB criteria and in 24.3% of patients by the troponin criteria of greater than 3 times the diagnostic level. Both CKMB (hazard ratio [HR], 1.38; 95% CI, 1.22-1.55) and troponin (HR, 1.35; 95% CI, 1.18-1.54) as continuous values were associated with 1-year mortality. The mortality effect of a more than 3-fold increase was greater for CKMB (adjusted HR, 2.5; 95% CI, 1.5-4.1) than for troponin (adjusted HR, 1.7; 95% CI, 1.1-2.5). A troponin threshold more than 20 times the diagnostic level provided similar frequency (7.0%) and mortality risk (adjusted HR, 2.6; 95% CI, 1.6-4.3) as a 3-fold increase in CKMB. A regression spline model of the relationship between troponin and 1-year mortality demonstrated that the hazard of mortality increased from 1.02 at 3-fold to 1.67 at 20-fold troponin elevation.
Conclusion: Troponin and CKMB elevations after percutaneous coronary intervention are associated with increased 1-year mortality rates, but thresholds for similar event frequency and mortality hazard are much higher for troponin than for CKMB.