Background: Hip fracture surgery is associated with a significant incidence of postoperative myocardial infarction (postop-MI) up to 14% in the first 7 days after repair. Patients who sustain postop-MI have 1-year mortality rates up to 36%. However, the impact of risk factor modification and routine troponin monitoring on the incidence and prognosis of postop-MI remains to be fully elucidated. Furthermore, myocardial injury after noncardiac surgery (MINS), defined as peak postoperative troponin T level of ≥ 0.03 ng/mL from ischemic cause has been associated with higher 30-day mortality after hip fracture surgery. Recently, absolute increases between pre- and postoperative, or two postoperative troponin concentrations have been shown to better represent new ischemia and differentiate from chronic troponin elevations. These increases, characterized as perioperative myocardial injury (PMI), have been associated with higher mortality in noncardiac surgeries. Despite these findings, postop-MI, MINS and PMI have not been fully evaluated in regard to postoperative outcomes in hip fracture surgery patients.
Methods: 248 patients who underwent hip fracture repair from April 2016 to June 2021 were included. We defined MINS as peak postoperative troponin T level of ≥ 0.03 ng/mL from an ischemic cause within 30 days of surgery. PMI was defined as an increase in troponin T level of ≥ 0.03 ng/mL between preoperative (within 30 days prior to procedure) and postoperative (within 30 days after procedure), or two consecutive postoperative troponins. Postop-MI was defined as troponin T level of ≥ 0.03 ng/mL (within 30 days after procedure) and one of the following: a) ischemic symptoms, b) ischemic ECG changes, c) pathologic Q waves, d) new regional wall motion abnormality/loss of myocardium per nuclear stress test, or e) coronary thrombosis by angiography or autopsy. Chi-squared analysis was used to compare proportions.
Results: 1-year and 2-year postoperative mortality rates were 21% (n=52) and 32% (n=79) respectively. 64/248 patients met inclusion criteria for MINS evaluation. 1-year mortality was significantly higher in patients with MINS when compared to those without MINS (52.3% vs 18.2%; p < 0.0001). 52/248 patients met inclusion criteria for PMI evaluation. 1-year mortality was significantly higher in PMI patients when compared to those without PMI (59.1% vs 26.7%; p < 0.0001). 64/248 patients met inclusion criteria for postop-MI evaluation; 1-year mortality was significantly higher in patients with postop-MI compared to those without postop-MI (59.1% vs 31.0%; p < 0.0001). Among patients diagnosed with MINS, PMI, or postop-MI, no additional deaths were noted between one and two years.
Conclusions: MINS, PMI and postop-MI are associated with a significantly higher mortality after hip fracture surgery, with the incidence peaking around 1-year after surgery. As these ischemic syndromes often occur without typical symptoms in the setting of powerful perioperative analgesia, these adverse outcomes necessitate further research on troponin surveillance.
