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.