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The biomarker CK-MB should be preferred over cardiac troponin (cTn) to identify coronary angioplasty-related myocardial injury that predicts later events, a new consensus statement said.

When clinicians switched to cTn from CK-MB, they didn't have a thorough understanding of the prognostic implications of rising levels of cTn following percutaneous coronary intervention (PCI), according to of the Mayo Clinic in Jacksonville, Fla., and colleagues.

Cardiac troponin, for example, can be overly sensitive, resulting in unfounded suspicion that many patients have suffered a clinically relevant myocardial infarction (MI) than the objective evidence would support, they wrote in the paper published online in Catheterization and Cardiovascular Interventions.

The writing committee of the , noted that the cTn thresholds were "arbitrarily chosen and of uncertain clinical relevance, and not grounded on substantial scientific evidence linking their occurrence to subsequent adverse outcomes," Moussa and colleagues pointed out.

However, in its defense, the Third Universal Definition employed higher thresholds of biomarkers than its predecessor and more stringent criteria for PCI-related MIs, wrote Hani Jneid, MD, of Baylor College of Medicine in Houston, in a commentary along with the publication of the new definition.

"This reflects the recognition that very and/or imaging tools, but that not all of them necessarily constitute revascularization-related MIs," he said.

Nevertheless, Moussa and colleagues argued that the Third Universal Definition criteria are too sensitive and will misclassify many patients as having a type 4a MI (peri- or postoperative).

A study by Igor Klem, MD, from Duke University Medical Center, found that only the of longer-term adverse events.

The new high-sensitivity assays detect very low levels of cTn, resulting in many false positives, they said.

In fact, the new expert consensus statement, developed by the Society for Cardiovascular Angiography and Interventions (SCAI), recommends against the use of high-sensitivity assays for post-PCI (and post-CABG) MI.

Another cardiac MRI study found the sensitivity, specificity, and positive predictive value of cTn I to rule in or out MI were 100%, 22%, and 19%, respectively. When CK-MB was used, the analogous findings were 60%, 93%, and 60%, respectively, according to Chris Lim, MBBS, from the Oxford Heart Centre in England, and colleagues.

when the corresponding MRI scans found no such evidence. In contrast, CK-MB correlated well with MRI findings.

The definition of MI for both biomarkers in the study was levels greater than three times the 99th percentile of the upper reference limit (URL).

To increase the specificity of cTn to equal that of CK-MB (93%), Lim and colleagues said the cTn threshold would need to be 40 times the 99th percentile URL -- however, the sensitivity would not change.

Also of note, the new expert consensus document calls for biomarker assessment before as well as after PCI.

Moussa and colleagues said that cTn may be falsely elevated in 10% or more of patients post-PCI for various reasons including analytical errors or cTn presence due to non-cardiac causes. Also, evidence suggests that pre-PCI cTn elevations correlate better with subsequent mortality.

If possible, two biomarker assessments should be taken within 24 hours of PCI, even if the procedure is uncomplicated. Rarely, however, is even one measurement taken after a uncomplicated PCI, the authors noted.

Current guidelines from the American Heart Association, the American College of Cardiology, and SCAI assign a class IIb recommendation to biomarker assessment following uncomplicated PCI.

Nevertheless, the new consensus document, the authors said, is a first step in addressing the limitations of the current definition of clinically relevant MI.

From the American Heart Association:

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