The concentration of troponin is elevated in almost all patients after bypass surgery, with marked increases in 20-40% of patients (7,49-54). Several studies have shown lower postoperative troponin levels with minimally invasive and off-pump surgical techniques (55-62). The type and route of delivery of cardioplegia may also influence the perioperative release of troponin (63-65).
Postoperative troponin levels have greater sensitivity and specificity for the diagnosis of perioperative MI (based on electrocardiographic changes, wall motion abnormalities, and/or scintigraphic perfusion defects) than CK-MB (50,51,66-69). However, CK-MB may be more sensitive than troponin in the first 12 h after surgery (70). Postoperative troponin levels are higher in patients with documented early graft occlusion (71,72). Nevertheless, owing to considerable overlap oftroponin values between patients with and without graft occlusion, troponin levels may not reliably predict graft occlusion in individual patients (71). The most appropriate troponin cutoff values for defining perioperative MI have not clearly been defined.
Several studies have supported a relationship between marked postoperative elevation of CK-MB and subsequent survival (Fig. 7). The relationship between postoperative levels oftroponin and clinical outcomes has not been extensively studied. However, a relationship to adverse outcomes does appear to exist. Eigel et al. measured troponin I immediately after bypass surgery in 540 patients and found troponin I release to be a significant predictor of death and reinfarction (95). In another series of 202 patients undergoing CABG, high postoperative troponin I levels were associated with increased risk of cardiac death at 2 yr (73). In 224 patients undergoing cardiac surgery (bypass surgery in 171 patients), a postoperative troponin T level © 1.58 ng/mL was an independent predictor of in-hospital complications, including death, shock, and MI (74); a prolonged length of stay in the intensive care unit (75); and mortality at 1 yr (76). This observation is consistent with the findings of other studies documenting the association between high postoperative troponin I or troponin T levels and postoperative short- and long-term morbidity and mortality (Fig. 8) (77-80).
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