Weak diagnostic performance of troponin,creatine kinase and creatine kinase-MB to diagnose or exclude myocardial infarction after successful resuscitation

Background

The aim of this study is to evaluate the diagnostic accuracy of the cardiac injury markers troponin (TNT), creatine kinase (CK) and creatine kinase-MB (CK-MB) to diagnose or exclude acute myocardial infarction after cardiac arrest.

Methods

226 patients who underwent diagnostic coronary angiography after sudden cardiac arrest were analyzed retrospectively. Levels of TNT, CK and CK-MB on admission and 6 h, 24 h and 36 h later were retrieved from the files and compared with the results of coronary angiography.

Results

Acute myocardial infarction (AMI) as well as non-AMI patients showed increasing levels of TNT and CK after resuscitation, although the AMI group showed significantly higher TNT and CK levels. Receiver operator curves were calculated to determine the diagnostic precision of TNT, CK and CK-MB to differentiate AMI and non-AMI patients. All analyzed markers yielded mediocre diagnostic precision with an area under the ROC curve of 0.7020, 0.6802 and 0.6508 for 6 h TNT, CK and CK-MB, respectively. Applying a modified cut-off of 1 μg/l the 6 h TNT measurement had a sensitivity of 70.9% and specificity of 61.2% to diagnose AMI after cardiac arrest. Using CK 800 U/l as cut-off level resulted in a sensitivity of 62.5% and specificity of 73.7%, CK-MB levels higher than 100 U/l yielded a sensitivity of 58.8% and specificity of 72.7%.

Conclusion

Cardiac injury markers cannot be used to reliably diagnose or rule out AMI after resuscitation. Consequently we propose that indication for coronary angiography should be extended to all patients without a certain alternative diagnosis explaining the occurrence of cardiac arrest.