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Canadian Journal of Cardiology

WHAT HS-TROPONIN LEVEL BEST CORRELATES WITH A PROGNOSTICALLY SIGNIFICANT CK-MB INCREASE POST-ELECTIVE PERCUTANEOUS INTERVENTION?

      Background

      In patients undergoing percutaneous coronary intervention (PCI), the cut-off value for high-sensitivity troponins (hs-cTn) has been set at over 5 times the 99th percentile upper reference limit (URL) by expert opinion in the 4th universal definition of MI. However, in contrast to post-procedural CK-MB isoenzyme elevation, for which a negative prognostic impact has been well documented when >3 times the URL, there is less evidence documenting the significance of post-PCI hs-cTn rise in relation to CK-MB. Some authorities have suggested using a threshold between 35 and 70 times the URL to differentiate non-significant myocardial injury from MI, but these thresholds have not been validated. We studied the incidence of type 4a MI and myocardial injury and the association between hs-cTn and CK-MB elevation.

      Methods and Results

      Following the adoption of hs-cTn (Troponin I, Siemens) at our institution, we studied consecutive patients who underwent a non-urgent PCI with post-procedural hs-cTn and CK-MB measurements. All patients were either admitted from home or had normal pre-PCI hs-cTn. Primary outcomes were the incidence of type 4a MI, of myocardial injury (defined as hs-cTn elevation >5 times the URL without other criteria of ischemia) and the rise of CK-MB >3 times the URL. Out of 214 patients undergoing PCI, significant hs-cTn elevation occurred in 52% of patients, among whom 15% had type 4a MI and 37% had myocardial injury, with a mean hs-cTn of 5530 and 955, respectively. Among 33 patients with type 4a MI, 39% had prolonged chest pain, 52% had ECG changes and 79% had an angiographic complication. Risk factors for peri-procedural type 4a MI were female sex (OR 2.5), intervention on a chronic total occlusion (OR 3.6), higher number of stents and longer total stent length. In patients with CK-MB >3 times the URL, mean troponin was 9320. Receiver operating characteristic curve (AUC = 0.98) showed that a hs-cTn value of 1830 for men, the equivalent of 34.5 times the URL, and 2535 for women, 74.6 times the URL, best correlated with a CK-MB elevation of >3 times the 99th percentile URL.

      Conclusion

      More than half (52%) of patients undergoing elective PCI have peri-procedural myocardial injury according to the current definition. The high sensitivity of hs-cTn likely leads to overdetection of myocardial injury. Our study supports the suggested use of a higher hs-cTn threshold to define prognostically significant myocardial injury, between 35 to 75 times the 99th percentile URL.
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