Interpretation of postoperative troponin elevations remains central to diagnosing perioperative myocardial infarction after coronary artery bypass grafting (CABG). A study published in the Journal of the American Heart Association found that cardiac troponin I (cTnI) and cardiac troponin T (cTnT) showed different release patterns after uncomplicated CABG, with cTnI more frequently exceeding current diagnostic biomarker thresholds.

Adults older than 18 years undergoing isolated CABG were included. Measurements of cTnT and cTnI were obtained in the same patients from the same blood samples. To define an uneventful postoperative course, patients included had patent bypass grafts on postoperative computed tomography and no decrease of at least 10% in left ventricular ejection fraction. Perioperative myocardial infarction criteria were assessed using the Universal Definition of Myocardial Infarction, Academic Research Consortium-2, and VISION frameworks.

The study included 258 patients with a median age of 69 years (interquartile range [IQR], 62-75). Median postoperative peak troponin values were 349 ng/L (IQR, 206-547) for cTnT and 1,517 ng/L (IQR, 752-2,897) for cTnI. Peak values occurred most often on the first postoperative day.

Biomarker cutoffs were exceeded more often for cTnI than for cTnT across definitions. Under the Universal Definition of Myocardial Infarction, thresholds were exceeded in 72.4% for cTnI versus 60.0% for cTnT (P<0.001). Under the Academic Research Consortium-2 criteria, rates were 69.2% versus 30.0%, respectively (P<0.001). Differences narrowed but remained after adding echocardiographic and electrocardiographic criteria.

The findings indicate that cTnT and cTnI are not interchangeable after CABG and may influence the classification of perioperative myocardial infarction under current definitions.