Clinical Implications

Perioperative MI, whether clinically apparent or silent, is associated with increased mortality in both the short and long term. Most perioperative infarctions are asymptomatic and detected only by serial ECG and myocardial enzyme monitoring. Likewise, in-hospital mortality is uncommon in the setting of perioperative MI, with hospital survival rates typically greater than 90%, similar to rates for MI in the nonoperative setting. However, in a manner analogous to clinically silent MI detected after PCI, even smaller infarcts detected after noncardiac surgery are associated with striking increases in medium- to late-term mortality. In one series of 229 patients who had routine serial myocardial enzyme determinations performed over a 3-day period after major vascular surgery, elevated serum troponin levels were detected in 12% of the patients. Whereas increased troponin levels were not associated with a greater likelihood of in-hospital mortality, by 6 months those patients with perioperative troponin elevations demonstrated a sixfold increase in mortality and a 27-fold excess rate of subsequent MI compared with patients without a perioperative troponin rise. A dose-response relationship was noted within this cohort, whereby higher postoperative troponin concentrations were associated with progressively greater likelihoods of adverse events during follow-up.4 In a longer-term surveillance study of 447 patients who underwent vascular surgery, elevations in serum tro-ponin and/or creatine kinase (CK) levels were associated with a highly significant twofold to fourfold increase in mortality during a mean follow-up period of 32 months, independent of other clinical factors such as age or prior cardiac history. Even minor elevations in biomarker levels during the initial 72 hours after surgery were predictive of late mortality (Fig. 7-3).5 Similarly, in a separate group of 391 patients who underwent vascular surgery, postoperative troponin elevation was associated with significant elevations in death or MI, both at 30 days (hazard ratio [HR] = 5.5; 95% confidence interval [CI]: 3.2 to 9.4) and at 18 months (HR = 4.7; 95% CI:

Figure 7-3. Relationship between degree of troponin elevation after vascular surgery and subsequent mortality among 447 patients. cTn-I, cardiac troponin-I; cTn-T, cardiac troponin-T. (From Landesberg G, Shatz V, Akopnik I, et al: Association of cardiac troponin, CK-MB, and postoperative myocardial ischemia with long-term survival after major vascular surgery. J Am Coll Cardiol 2003;42:1547-1554.)

Months after surgery

0.6 < cTn-I <1.5 and/or 0.03 < cTn-T <0.1 -

1.5 < cTn-I <3.1 and/or 0.1 < cTn-T <0.2 -

2.9 to 7.6), even after adjustment for other clinical predictors of adverse events.6

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