Introduction
The European society of cardiology (ESC) state that “for the detection of type 5 myocardial infarction (MI), a specific cut-off value for all procedures and all cardiac troponin (cTn) assays is difficult to define” [1]. According to them, coronary artery bypass grafting (CABG) - related MI is defined by an increase of cTn more than 10 times the 99th percentile upper reference limit (URL) during the first 48 hours after surgery (in patients with normal baseline cTn) with at least one of the following 1). Development of new Q waves, 2). Angiographic documented graft or coronary occlusion, 3). Imaging evidence of loss of viable myocardium or regional wall motion abnormality [1]. The authors point out the existing complexity of type 5 MI diagnosis: “Postoperatively observed ST-segment deviations and T-wave changes as well as isolated cTn elevations indicate direct procedural epicardial injury rather than myocardial ischemia” [1].
The introduction of high-sensitive cTn assays has led to additional ambiguity. Several assays exist for the detection of two different regulatory proteins of the tropomyosin complex based on high-affinity antibodies specific for troponin T or I. An increase in sensitivity of the corresponding tests is usually accompanied by a loss of specificity, despite improved analytical performance. Accordingly, it appears difficult to classify postoperative high-sensitive cTn values with regard to the clinical course.
The aim of this study, intentionally including different types of cardiac surgery, is to investigate associations between postoperative high-sensitive cardiac troponin T (hs-cTnT) rise and clinical outcome in terms of adverse events and other possible (surgery-related) factors. In addition, an attempt is made to define thresholds indicative of surgically induced myocardial ischemia, thus contributing to the general understanding of postoperatively elevated cardiac enzymes.