eComment: Is early assessment of cardiac troponin I a valuable predictor of mortality after cardiac surgery?

We read with considerable interest the recent article by Dr. van Geene and colleagues which aimed to investigate the role of troponin in predicting in-hospital mortality after cardiac surgery [1]. In this large study, the authors report that postoperative cardiac troponin I (cTnI) levels, measured within the first hour after cardiac surgery, can identify a subgroup of patients with increased risk for in-hospital mortality [1]. The routine measurement of cTnI is currently performed in many centers after cardiac surgery. However, the most important issues are whether a measured cTnI level in a particular patient is higher than might be expected when other factors, such as the type of operation [coronary artery bypass graft (CABG) or valve surgery], perioperative myocardial preservation, duration of cardiopulmonary bypass (CPB) and aortic cross-clamp time or offpump surgery are taken into account and whether such an elevation indicates that the patient is at increased risk of death. Croal et al. suggest that cTnI levels are usually elevated after cardiac surgery but that the degree of elevation varies depending on the nature of the operation [2]. Regardless of other factors, cTnI levels 24 h after surgery are strong predictors of short-, medium-, and long-term mortality. Levels of cTnI determined 2 h after surgery are also frequently elevated. However, the prognostic utility is inferior to the 24 h value, indicating that very early cTnI values may not be as useful as measurements taken later after surgery [2]. cTnI represents a sensitive and specific marker of myocardial damage in all types of cardiac surgery. Despite its value in predicting mortality after cardiac surgery, the determination of the threshold level, and the best timing for the assessment have been widely studied, the results published are inconsistent [2–5]. In our opinion, the cTnI increase depends on the type of surgery and the subsequent degree of direct surgical myocardial trauma. Valve surgery may induce more direct surgical trauma than CABG surgery and, therefore, higher cTnI release. Furthermore, we believe that the best timing for cTnI measurement in order to be a powerful predictor of mortality is 24 h after cardiac surgery. However, more studies using more sensitive assays are needed to further clarify the exact role of post-cardiac surgery troponin measurement in mortality prediction.