Ann Thorac Surg 2008;85:1354. doi:10.1016/j.athoracsur.2008.02.018
© 2008 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Invited Commentary
Valluvan Jeevanandam, MD
Section of Cardiothoracic Surgery, The University of Chicago Medical Center, 5841 S Maryland Ave, Chicago, IL MC5040
(Email: jeevan{at}uchicago.edu).
The authors [1] should be congratulated on a well-written article that evaluates the value of troponin T (TnT) elevation after cardiac surgery. They reviewed all patients undergoing cardiac surgery between 2002 and 2006. After excluding patients with recent myocardial infarction (< 30 days) and those having noncoronary artery bypass grafting along with or without valve surgery, there were 2,133 patients. There were 215 patients (10%) with incomplete data that were not included in the study. Using acceptable statistical analysis, the authors [1] conclude that levels of TnT > 0.8 for isolated coronary artery bypass grafting is associated with major cardiovascular adverse event (MACE) and can predict poor outcomes after cardiac surgery. The general observations are acceptable, but there are some caveats.
In this study, the predictive power of TnT regarding MACE is highly dependent on the definition of low-output syndrome (LOS). The LOS was defined as requiring inotropes or an intraaortic balloon pump to keep the cardiac index > 2.0. The LOS was the overwhelming component of MACE, but the authors did not a have a protocol directing the use of inotropes. There is no mention of volume status, right heart catheterization measurement, or the amount of inotropic support. If LOS is removed, the event rates become very small and the conclusions may have to be altered. In particular, the relevance of TnT decreases because myocardial infarction must be associated with elevated levels due to myocardial necrosis.
The troponin I (TnI) fraction studied must also be critically examined. The most commonly available assay is TnT. The authors make the observation that TnT is more consistent between laboratories because there is only one manufacturer, but it is less available and more expensive.
There is no doubt that elevated TnT is associated with poor outcomes. However, the absolute level that may predict poor outcome is debatable because the definition of LOS is not clear. On a practical note, what can the clinician do differently? If a patient is in LOS, support will be given to optimize the patient and the outcome will be expected to be inferior to a patient who is hemodynamically stable. The best role for TnT may be a quality assurance marker that can be considered a surrogate marker for a suboptimal procedure with significant myocardial injury. Unless laboratories standardize to TnT, each program will have to determine its own level that can define suboptimal outcomes. The most powerful value of TnT may be the ability to predict long-term survival (> 1 year) and allow for increased vigilance in follow-up of these patients, including possible therapies targeted toward their mode of death. The authors [1] have valuable data available; hopefully they will obtain long-term data and determine the true predictive value of TnT.
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References
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- Nesher N, Alghamdi AA, Singh SK, et al. Troponin after cardiac surgery: a predictor or a phenomenon? Ann Thorac Surg 2008;85:1348-1354.[Abstract/Free Full Text]
Related Article
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Troponin after Cardiac Surgery: A Predictor or a Phenomenon?
- Nahum Nesher, Abdullah A. Alghamdi, Steve K. Singh, Jeri Y. Sever, George T. Christakis, Bernard S. Goldman, Gideon N. Cohen, Fuad Moussa, and Stephen E. Fremes
Ann. Thorac. Surg. 2008 85: 1348-1354.
[Abstract]
[Full Text]
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