High-sensitivity cardiac troponin I and T kinetics after coronary artery bypass grafting in relation to current definitions of myocardial infarction: a systematic review and meta-anal
Authors: Denessen E J S , Heuts S , Daemen J H T , Vroemen W H M , Sels J W , Segers P , Van 'T Hof A W J , Maessen J G , Bekers O , Van Der Horst I C C , Mingels A M A 
Published: October 2021

Abstract

Background
Cardiac troponins – either cardiac troponin T (cTnT) or cardiac troponin I (cTnI) – are the preferred biomarkers for the diagnosis of myocardial infarction (MI), also after coronary artery bypass grafting (CABG), also known as type 5 MI. Two distinct arbitrarily chosen definitions of MI have been formulated, proposing different diagnostic cTn cut-off concentrations for both cTnT and cTnI (defined by multiples of the 99th percentile upper reference limit of 10x, 35x or 70x URL, with or without need for additional electrocardiographical or imaging findings). Remarkably, these cut-off values are not (yet) validated for the current high-sensitivity (hs-cTn) assays.

Purpose
Investigating the kinetics of hs-cTnT and hs-cTnI in relation to the current definitions of myocardial infarction type 5 in patients undergoing isolated CABG.

Methods
A systematic search was applied to MEDLINE and EMBASE. The search terms were “coronary artery bypass” AND “high-sensitivity cardiac troponin”, including alternative names and abbreviations. All studies reporting hs-cTnT or hs-cTnI on at least two different time points were included. Hs-cTn concentrations were extracted, stratified and normalized to the URL of the assay. The search was performed by 2 independent reviewers, in agreement with the PRISMA guidelines.

Results
For hs-cTnT, and hs-cTnI, 15 (2646 patients) and 18 studies (1760 patients) were included for meta-analysis, respectively. The mean age of the total hs-cTnT and hs-cTnI patient population was 65 (11) and 63 (11) years, 22% and 21% was female, respectively. Preoperative hs-cTnT and hs-cTnI was 1.2xURL (mean, 95% CI: 0.9–1.4) and 6.1xURL (4.9–7.2), respectively. Peak hs-cTnT and hs-cTnI was reached 6–8h postoperative up to 44.9xURL (28.6–61.1) and 135xURL (109–161), respectively (figure 1). For patients where MI-5 was ruled out, peak hs-cTnT and hs-cTnI level was 43.9xURL (20.1–67.6) and 97.1xURL (20.6–214) respectively. Peak hs-cTnT and hs-cTnI concentrations were dependent on surgical strategy. Patients undergoing off-pump CABG, reached a peak 16–24h post-operatively (hs-cTnT: 13.4xURL, 8.1–18.8) and (hs-cTnI: 60.6xURL, 47.0–74.2). This was notably different from on-pump CABG, where peak hs-cTnT and hs-cTnI was reached 6–8h postoperative (44.8xURL, 37.8–51.9) and (144xURL, 114–174) respectively. MI incidence was 2.7% (range 0–7.0%) and 6.9% (range 0–32%) and the 30-day mortality was ranging from 0–4% and 0–2.5% for hs-cTnT and hs-cTnI respectively.

Conclusion
Postoperative hs-cTn surpasses most of the proposed cut-off concentrations by current definitions of type 5 MI, for hs-cTnT but especially for hs-cTnI. Differences in hs-cTn release following on-pump versus off-pump CABG were also observed, implying the need for different cut-off values for different surgical strategies. Furthermore, future clinical studies should focus on the diagnostic accuracy of cTn in type 5 MI and the re-evaluation of hs-cTn cut-off values in particular.

Funding Acknowledgement
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): ZonMw Veni grant