Troponin Variability After CABG May Create Diagnostic Uncertainty, Reveals Research
Switzerland: After uneventful coronary artery bypass graft (CABG) surgery, elevations in cardiac troponins are common. According to a new study, significant differences exist between cTnT and cTnI levels, with cTnI consistently showing higher postoperative concentrations. This discrepancy means that cTnI more often exceeds thresholds used to define perioperative myocardial infarction (PMI). As a result, the choice of assay can alter PMI diagnosis rates by up to 300%, leading to considerable clinical uncertainty and potential misinformation for both physicians and patients.
These findings were reported in the Journal of the American Heart Association by Luca Koechlin from the Department of Cardiac Surgery, University Hospital Basel, Switzerland, and colleagues. The study aimed to directly compare the postoperative release patterns of cardiac troponin T (cTnT) and cardiac troponin I (cTnI), and to evaluate how differences between these biomarkers influence the diagnosis of PMI based on current clinical definitions.
The study included adult patients undergoing isolated CABG surgery, with both cTnT and cTnI measured from the same blood samples. Only those with an uncomplicated postoperative course—confirmed by patent grafts and preserved cardiac function without significant decline in left ventricular ejection fraction—were analyzed. Established PMI definitions, including the Universal Definition of Myocardial Infarction, Academic Research Consortium-2 criteria, and the VISION framework, were applied.
The following were the key findings:
- The study included 258 patients with a median age of 69 years.
- A clear difference in postoperative troponin levels was observed between the two assays.
- Peak troponin levels were significantly higher for cTnI than for cTnT.
- Both biomarkers generally reached their highest levels on the first postoperative day.
- The difference in levels led to notable variation in the number of patients exceeding diagnostic thresholds for PMI.
- Using the Universal Definition of Myocardial Infarction, more patients met PMI criteria based on cTnI than cTnT.
- Similar patterns were seen across other diagnostic criteria, with cTnI consistently identifying more cases.
- Even after incorporating ECG and echocardiographic findings, differences between cTnI and cTnT persisted, though to a lesser extent.
The findings highlight a critical issue in clinical practice and research: the reliance on biomarker thresholds that may not be directly comparable across assays. Since cTnI tends to rise to higher levels postoperatively, its use may lead to overestimation of PMI incidence, while cTnT may yield more conservative estimates. This inconsistency has important implications for patient diagnosis, clinical decision-making, and the interpretation of clinical trial outcomes.
The authors suggest that future definitions of PMI should account for assay-specific differences or incorporate additional diagnostic criteria, such as imaging and ECG findings, to improve accuracy. Standardizing these approaches could help reduce variability in diagnosis and avoid potential overdiagnosis or misclassification.
Overall, the study highlights that differences between cTnT and cTnI are not merely analytical but have significant clinical consequences, emphasizing the need for more refined and consistent diagnostic criteria in the postoperative cardiac setting.
Reference: https://doi.org/10.1161/JAHA.125.045234
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