Should All Orthopaedic Patients Undergo Postoperative Troponin Testing?

Commentary Thomas et al. analyzed the association between elevated values on postoperative non-high-sensitivity troponin T (TnT) assays and 30-day all-cause mortality in a group of 3,092 patients who underwent orthopaedic surgery at ≥45 years of age. The patients all had daily TnT testing on postoperative days 0 through 3 while hospitalized. A total of 12% had a postoperative TnT elevation of ≥0.3 ng/mL, termed “myocardial injury after noncardiac surgery” (MINS). The authors found a strong association between MINS and the 30-day mortality rate (9.8% for patients with MINS versus 1.0% for those without MINS). Of the patients with MINS, 81% were symptom-free, suggesting that the MINS would not have been identified clinically had TnT testing not been done. On the basis of their results, the authors recommend routine TnT measurement in all orthopaedic patients postoperatively. Is this supported by their data? This study represents a subanalysis of the Vascular Events in Noncardiac Surgery Patients Cohort Evaluation (VISION) study, which included >15,000 patients who underwent noncardiac surgery and similarly showed a strong association between MINS and 30-day mortality1. On the basis of that study, the Canadian Cardiovascular Society (CCS) recommended routine postoperative troponin testing for noncardiac patients2. (Of note, the lead VISION investigator, P.J. Devereaux, was a CCS guideline cochair.) In contrast, the American College of Cardiology/American Heart Association guideline has recommended against routine postoperative troponin measurement for noncardiac patients because “routine screening with troponin provides a nonspecific assessment of risk, [but] does not indicate a specific course of therapy…”3 Inpatient mortality after hip fracture surgery is >5 times that following elective hip arthroplasty4. In the study by Thomas et al., MINS occurred in 40% of the patients after above or below-the-knee amputation, 14% after “major hip or pelvic surgery” (which included both hip fracture surgery and total hip arthroplasty), and only 5% after knee arthroplasty. This wide variation suggests that routine TnT testing might be better targeted to patients at the highest risk based on comorbidities and surgery type. There are a variety of risk stratification tools that can be used preoperatively, such as the Revised Cardiac Risk Index (RCRI), American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) risk calculator, and measurement of N-terminal pro-B-type natriuretic peptide (NT-pro-BNP)/BNP concentrations, to identify patients at high risk of postoperative complications and/or death2. However, VISION demonstrated that MINS was an independent risk factor for 30-day mortality even after considering clinical variables such as underlying cardiovascular disease and type of surgery1. At issue is the fact that MINS is a biomarker, predictive of mortality but without a clear treatment algorithm. Usual clinical practice for a patient with an elevated TnT measurement after surgery is to assess left ventricular function (with echocardiography), perform stress testing, consider coronary angiography, and initiate/optimize statin and aspirin administration. In the current study, Thomas et al. do not specify how the patients with MINS were managed and, notably, one-third of deaths were non-vascular. A recent randomized trial comparing treatment of MINS with dabigatran (110 mg) versus a placebo in elderly patients with known vascular disease demonstrated a reduction in major vascular complications (a composite of vascular mortality, myocardial infarction, non-hemorrhagic stroke, peripheral arterial thrombosis, amputation, and symptomatic venous thromboembolism) over the 2 years after surgery5. This suggests that intermediate-dose anticoagulation may be a way to reduce long-term morbidity in these patients. Thirty-day mortality was not reported in that study, however. We are not aware of any randomized trials evaluating the role of revascularization for patients with MINS. However, postoperative myocardial ischemia is usually due to a supply-demand mismatch rather than acute coronary artery obstruction, so revascularization might not improve outcomes and could actually increase the risk of complications because of the need for dual antiplatelet therapy. Given the lack of clear guidance on how to act on MINS in a real-world setting, it is premature to recommend TnT testing for all orthopaedic patients postoperatively, although it could be justified for risk stratification purposes in patients undergoing above or below-the-knee amputation or hip fracture surgery. Additional randomized trials assessing the benefit of aspirin, statins, anticoagulants, and/or colchicine (which has been shown to reduce recurrent ischemia in patients with recent myocardial infarction) in patients with MINS is warranted.

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