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With the “Universal Definition,” Measurement of Creatine Kinase-Myocardial Band Rather Than Troponin Allows More Accurate Diagnosis of Periprocedural Necrosis and Infarction After Coronary Intervention
Study Questions:
What is the best biomarker for defining post-percutaneous coronary intervention (PCI) myocardial infarction (MI)?
Methods:
The authors evaluated 32 patients who underwent multivessel PCI and cardiac magnetic resonance (CMR) imaging to assess periprocedural MI. All patients had cardiac troponin I, creatine kinase-myocardial band (CK-MB), and inflammatory markers measured at baseline, 1 hour, 6 hours, 12 hours, and 24 hours after the procedure. Patients were divided into three groups based on post-procedural markers of myonecrosis: group 1 (no injury with biomarker <99th percentile), group 2 (periprocedural myonecrosis with biomarker 1-3 x upper limit of normal [ULN]), and group 3 (post-PCI MI (>3 x 99th percentile). Differences in inflammatory profiles and injury detected on CMR as late gadolinium enhancement (LGE) were analyzed.
Results:
Troponin elevation was common, and 26 patients were defined as post-PCI MI based on the troponin level, but only a small minority had evidence of an abnormality on CMR-LGE. With CK-MB, there were 17, 10, and 5 patients in groups 1-3, respectively. Patients with CK-MB–defined post-PCI MI were more likely to demonstrate with new CMR-LGE injury. The receiver operating curve analysis for detection of CMR-LGE showed areas under the curve of 0.985 for cardiac troponin I versus 0.970 for CK-MB, with no significant difference between the two areas. While there was no difference in the choice of using cardiac troponin I versus CK-MB, the current cutoff of 3 x ULN had poor specificity for troponin (specificity = 22%) compared with CK-MB (specificity = 92%). Based on this study, the optimal troponin cutoff for defining post-PCI myonecrosis would be a troponin of >40 x ULN.
Conclusions:
Compared with a troponin level >3 x ULN, an elevation in CK-MB >3 x ULN is a more sensitive marker of post-PCI MI.
Perspective:
The universal definition of MI supports preferential use of troponin 3 x ULN as the definition of periprocedural MI, although this cutoff is arbitrary. This study, although small, suggests that the old CK-MB–based standard is remarkably superior to the universal definition. Studies evaluating post-PCI MI should continue to use a CK-MB–based definition until larger studies can define the optimal troponin cutoff for defining post-PCI MI.
Keywords: Myocardial Infarction, Infarction, Biomarkers, Troponin I, Creatine, Sensitivity and Specificity, Creatine Kinase, MB Form, Necrosis, Magnetic Resonance Spectroscopy, Troponin, Percutaneous Coronary Intervention
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