High-Sensitivity Cardiac Troponin I and T Kinetics Differ following Coronary Bypass Surgery: A Systematic Review and Meta-Analysis

Background Cardiac troponin I and T are both used for diagnosing myocardial infarction (MI) after coronary artery bypass grafting (CABG), also known as type 5 MI (MI-5). Different MI-5 definitions have been formulated, using multiples of the 99th percentile upper reference limit (10x, 35x, or 70x URL), with or without supporting evidence. These definitions are arbitrarily chosen based on conventional assays and do not differentiate between troponin I and T. We therefore investigated the kinetics of high-sensitivity cardiac troponin I (hs-cTnI) and T (hs-cTnT) following CABG. Methods A systematic search was applied to MEDLINE and EMBASE databases including the search terms coronary artery bypass grafting AND high-sensitivity cardiac troponin. Studies reporting hs-cTnI or hs-cTnT on at least 2 different time points were included. Troponin concentrations were extracted and normalized to the assay-specific URL. Results For hs-cTnI and hs-cTnT, 17 (n = 1661 patients) and 15 studies (n = 2646 patients) were included, respectively. Preoperative hs-cTnI was 6.1x URL (95% confidence intervals: 4.9-7.2) and hs-cTnT 1.2x URL (0.9-1.4). Mean peak was reached 6-8 h postoperatively (126x URL, 99-153 and 45x URL, 29-61, respectively). Subanalysis of hs-cTnI illustrated assay-specific peak heights and kinetics, while subanalysis of surgical strategies revealed 3-fold higher hs-cTnI than hs-cTnT for on-pump CABG and 5-fold for off-pump CABG. Conclusion Postoperative hs-cTnI and hs-cTnT following CABG surpass most current diagnostic cutoff values. hs-cTnI was almost 3-fold higher than hs-cTnT, and appeared to be highly dependent on the assay used and surgical strategy. There is a need for assay-specific hs-cTnI and hs-cTnT cutoff values for accurate, timely identification of MI-5.

Automated summary

Studies have shown that postoperative levels of high-sensitivity cardiac troponin I (hs-cTnI) and T (hs-cTnT) following CABG exceed most current diagnostic cutoff values. Hs-cTnI was nearly 3 times higher than hs-cTnT, and its levels appeared to be highly dependent on the assay used and surgical strategy. There is a need for assay-specific cutoff values for hs-cTnI and hs-cTnT to accurately identify MI-5 in a timely manner.