Usefulness of postoperative high-sensitive troponin T measurement and implications for defining type 5 infarction

Background and aim of the study: Guidelines indicate for type 5 myocardial infarction (MI) that postoperative troponin need not be exclusively ischemic but may also be caused by epicardial injury. Complexity arises from the introduction of high-sensitive troponin. This study attempts to contribute to the understanding of postoperative high-sensitive cardiac troponin T (hs-cTnT) increase.

Methods: The median enzyme increase of different cardiac operations was compared. Linear regression analyses were used to determine correlations between enzyme rise and independent parameters. Receiver-operating characteristics (ROC) served to evaluate the discriminatory power of enzyme rise in detecting ischemia and to determine possible thresholds.

Results: Among 400 patients, 2.8% had intervention-related ischemia analogous to type 5 MI definition. The median postoperative hs-cTnT/creatine kinase myocardial band (CK-MB) increase varied according to types of surgery, with highest increase after mitral valve and lowest after off-pump coronary surgery. After ruling out patients with preoperatively elevated hs-cTnT, regression analysis confirmed Maze procedure (p < .001), intra-pericardial defibrillation (p = .002), emergency intervention (p = .01), blood transfusions (p = .02), and cardiopulmonary bypass time (p = .03) as significant factors associated with hs-cTnT increase. In addition, CK-MB increase was associated with mortality (p = .002). ROC confirmed good discriminatory power for hs-cTnT and CK-MB with ischemia-indicating thresholds of 1705.5 ng/L (hs-cTnT) and 113 U/L (CK-MB) considering different types of operations.

Conclusions: The Influence of the type of surgery and intervention-related parameters on hs-cTnT increase was confirmed. Potential thresholds indicating perioperative ischemia appear to be significantly elevated for high sensitive markers.