Troponin Criteria for Myocardial Infarction After Percutaneous Coronary Intervention
What levels of troponin following percutaneous coronary intervention (PCI) are associated with increased 1-year mortality rates?
Outcomes of 4,930 patients with elective coronary stent placement between 2004 and 2007 were analyzed to test the association between 1-year mortality and postprocedure elevation of either creatine kinase-myocardial band (CK-MB) or troponin.
Myocardial infarction (MI) occurred in 7.2% of patients by the CK-MB criteria and in 24.3% of patients by the troponin criteria of greater than 3 times the diagnostic level. Both CK-MB (hazard ratio [HR], 1.38) and troponin (HR, 1.35) as continuous values were associated with 1-year mortality. The mortality effect of a more than threefold increase was greater for CK-MB (adjusted HR, 2.5) than for troponin (adjusted HR, 1.7). A troponin threshold >20 times the diagnostic level provided similar frequency (7.0%) and mortality risk (adjusted HR, 2.6) as a threefold increase in CK-MB. A regression spline model of the relationship between troponin and 1-year mortality demonstrated that the hazard of mortality increased from 1.02 at threefold to 1.67 at 20-fold troponin elevation.
Troponin and CK-MB elevations after PCI are associated with increased 1-year mortality rates, but thresholds for similar event frequency and mortality hazard are much higher for troponin than for CK-MB.
While cardiac troponin measurements have been extremely valuable in the management of patients presenting with acute coronary syndrome, their clinical utility is less clear following elective PCI since minor elevations are common, but may not provide added prognostic information. Accordingly, this study demonstrates that it takes 20x troponin levels to reach a prognostic level of 3x CK-MB in terms of 1-year mortality. Although it would be informative to have baseline (pre-PCI) troponin levels and longer follow-up, these data will be useful when considering clinical implications of minor post-PCI troponin elevations.
Keywords: Myocardial Infarction, Acute Coronary Syndrome, Follow-Up Studies, Biological Markers, Creatine Kinase, MB Form, Stents, Troponin, Percutaneous Coronary Intervention
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