Rise and fall of high-sensitivity cardiac troponin T after coronary artery bypass grafting surgery in relation to current definitions of myocardial infarction: a systematic review and meta-analysis
Authors: Denessen E.J.S , Heuts S , Vroemen W.H.M , Sels J.W , Segers P , Bekers O , Van 't Hof A.W.J , Maessen J.G , Van Der Horst I.C.C , Mingels A.M.A 
Published: November 2020

Background

Cardiac troponins are the preferred biomarkers for the diagnosis of myocardial infarction (MI) and play an important role in coronary artery bypass grafting (CABG) related MI (type 5 MI). Different cut-off values, as defined by multiples of the 99th percentile upper reference limit (URL) for isolated and non-isolated troponin elevations have been proposed. Also, these definitions are based on arbitrarily chosen and varying values (3rd and 4th Universal definition: 10xURL, Society for Cardiovascular Angiography and Interventions (SCAI): 35 and 70xURL) and electrocardiographical or imaging findings. In addition to the controversy in MI definitions, the introduction of high-sensitivity cardiac troponin (hs-cTn) assays and their subsequent lower thresholds warrant a thorough re-assessment of hs-cTn dynamics after CABG.

Purpose

To evaluate the rise and fall of hs-cTn after CABG in relation to the definitions of myocardial infarction.

Methods

Studies published between 2008 and 2020 reporting hs-cTn concentrations in relation to CABG were searched through Pubmed and reviewed by 2 independent screeners. The search terms were “coronary artery bypass” AND “high-sensitivity cardiac troponin”, including alternative names and abbreviations. Inclusion criteria were the use of a hs-cTn assay in the postoperative phase, either for cardiac troponin T or I. This study was performed in agreement with the PRISMA guidelines.

Results

Out of 37 screened studies, 15 studies were included (2860 patients). The overall preoperative hs-cTnT concentration (median, 25th-75th percentile) was 43.5 (16.3–57.9) ng/L. Subsequently, in &gt;80% of CABG patients, preoperative hs-cTnT was elevated &gt;14 ng/L. Hs-cTnT was highly variable over time, with a peak of 408.7 (14.9–717.2) ng/L 6–8 h after CABG. Postoperative peak hs-cTnT concentrations rose &gt;10xURL (Universal definition) in 100% of CABG patients. Peak hs-cTnT &gt;35xURL and ±20% &gt;70xURL (SCAI definition) during the first 48 h was 30% and ∼20%, respectively (estimated from data depicted in Figure 1). Electrocardiographic and imaging findings were available for only 1 study (554 patients). Overall 30-day mortality was 1.7 (0.8–4.0)%, reported by 7 studies (2291 patients). Data regarding the association of hs-cTnT and clinical outcome was reported by 1 study. As only 4 studies (217 patients) reported on the results of hs-cTnI, using assays from different vendors, a meta-analysis for hs-cTnI could not be performed.

Conclusion

The different definitions of type 5 MI propose arbitrarily chosen cTn cut-off values, varying enormously between the definitions. The current thresholds may not apply to the majority of CABG patients, since &gt;80% had elevated preoperative hs-cTnT. Furthermore, hs-cTnT obtained within 48 h after CABG is highly variable over time. Therefore, further research is needed to establish clinically relevant hs-cTn thresholds and timing of sampling for a more accurate diagnosis of CABG procedure related MI.

Figure 1

Funding Acknowledgement

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