Cardiac Biomarker Kinetics in Patients after Coronary Artery Bypass Grafting with an Uncomplicated Course

BACKGROUND: The definition of periprocedural myocardial infarction (PMI) after coronary artery bypass grafting (CABG) remains debated, particularly regarding the use of cardiac troponins vs creatine kinase MB isoform (CK-MB), and biomarker thresholds seem outdated [10×, 35×, or 70× multiples of upper reference limits (URL)]. We studied high-sensitivity cardiac troponin T (hs-cTnT) and I (hs-cTnI), and CK-MB, following CABG patients with an emphasis on those with an uncomplicated course. METHODS: Patients undergoing isolated on-pump CABG and minimally invasive direct CABG (MIDCAB) were prospectively included. Blood was collected preoperatively and then postoperatively at intensive care unit (ICU) arrival, 5 h and 8 h subsequently, and postoperative days 1 and 3. hs-cTnT (Roche), hs-cTnI (Abbott), and CK-MB (Roche) were measured and normalized using URLs according to package inserts or the Universal Sample Bank. RESULTS: Sixty-one on-pump CABG and 22 MIDCAB patients were included. On-pump CABG patients showed a median (interquartile range) hs-cTnT peak of 610 (466-879) ng/L, hs-cTnI 3918 (2154-6713) ng/L, and CK-MB 22.0 (14.9-34.8) µg/L 5 h after ICU arrival. When normalized according to package inserts, this corresponds to 44× (33×-63×) URL, 150× (82×-256×) URL, 4.5 × (3.0×-7.1×) URL, respectively. These values slightly differ when sex-specific or other URL definitions are used (P > 0.05). In subgroup analyses, MIDCAB patients had reduced biomarker concentrations, and significant differences were observed between cardioplegia regimens (P < 0.001). CONCLUSION: The postoperative kinetics of hs-cTnT, hs-cTnI, and CK-MB in CABG patients with an uncomplicated course illustrate that hs-cTn, in particular, surpasses current diagnostic cutoffs for PMI. This varies in time, across hs-cTn assays, surgical approaches, and cardioplegia regimens.