Introduction The VISION study demonstrated an association between 30-day mortality after surgery and raised post-operative troponin levels.¹ Subsequently, diagnostic criteria for ‘ischaemic’ MINS were established excluding non-ischaemic aetiology.² We evaluated our initial experiences with post-operative troponin monitoring, to look in-depth at patients who suffer MINS events.

Methods Pre- and post-operative high-sensitive troponins were checked on all elective and emergency surgical patients over 45 years of age with an inpatient stay of more than 2 days between August 2014 and June 2015. A MINS event was defined as in the VISION (1) study as any positive post-operative troponin.

Thirty-day mortality after surgery was determined via HES data. Notes, pathology reports and discharge letters were reviewed for evidence of sepsis, prolonged tachycardia, multi-organ failure or significant bleeding (Hb loss of >5 g/l and/or total Hb <8 g/dl). Events were classified as ‘non MINS’, ‘unexplained MINS’ or ‘secondary MINS’ due to one of these provoking factors.

Cox regression analysis was performed to assess association between variables.

Results 388 patients were studied. 196 were male with a mean age of 69 years (range 45–95). 132 (34%) were emergency admissions. 245 (63.1%) had normal post-operative troponins (i.e. non MINS), with 81 (20.9%), 49 (12.6%) and 13 (3.4%) recording troponin levels of 17–50, 51–1000 and more than 1000 respectively. 21 of the positive post-op values represented a downward trend from pre-op tests, with a further 17 positive pre-op values falling into the normal range post-operatively.

The 30 day mortality rate was 2.8% compared to 1.9% in VISION. Of the 11 deaths, 10 (90.9%) were emergency admissions. Two (18.2%) deaths occurred in patients exhibiting a downward trend in troponin and 3 (27.3%) had a normal post-operative troponin (i.e. did not suffer a MINS event).

Discussion A raised post-operative troponin was associated with poor prognosis as suggested in the VISION study (p = 0.022 HR 0.213 [0.057–0.803]). Sepsis was also associated with a poor prognosis (p < 0.001 HR 0.08 [0.021–0.305]) as is emergency admission for surgery (p = 0.004 HR 0.05 [CI 0.006–0.392]). However, there was no mortality from ‘ischaemic’ MINS events (unexplained events and events secondary to tachycardia and bleeding).

Whether MINS events are a separate clinical entity related to unstable or significant coronary disease or a reflection of other poor prognostic factors remains unclear. Further studies assessing coronary anatomy may be useful in delineating this further.

References

1. Devereaux PJ, Chan MT, Alonso-Coello P, et al. Association between Post-operative Troponin Levels and 30-Day Mortality among Patients undergoing Noncardiac Surgery. JAMA. 2012;307(21)

2. Myocardial Injury After Noncardiac Surgery. VISION Study Investigators. Anaesthesiology, 2014;120: 564-–78