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DEFINITION AND CHARACTERISTICS OF MINS

Myocardial injury is defined as an elevated troponin above the 99th percentile upper reference level and is classified into three groups: 1) acute myocardial infarction (MI) in which there is a rise and fall of troponin with at least one elevated value plus symptoms, ECG changes, or imaging suggesting an ischemic etiology; 2) acute nonischemic myocardial injury (NIMI) in which there is a similar rise and fall in troponin but no signs or symptoms of ischemia; and 3) chronic myocardial injury in which there is an elevated troponin but no rise and fall pattern. Acute MI is further defined as Type I with acute plaque rupture or Type II where there is an oxygen supply-demand mismatch. Myocardial injury after noncardiac surgery (MINS) is defined as an elevated troponin with a rise and fall pattern occurring within 30 days of surgery and presumed to be of ischemic etiology but not required to meet criteria for MI.1 Definitions vary somewhat among investigators based on troponin used, specific criteria defining an elevated value, and need for absolute change in levels.2 Troponin elevations can be seen in many conditions, both ischemic and nonischemic (Table 36-1).

FIGURE 36-1

Postoperative Myocardial Injury. Adapted from Cohn SL, Rohatgi N, Patel P, Whinney C. Clinical Progress Note: Myocardial Injury After Noncardiac Surgery. J Hosp Med. 2020 Jul 1;15(7):412-415.

The incidence of MINS varies based on the specific troponin used, the patient group studied, and whether there was systematic or routine screening as opposed to only testing symptomatic patients.3,4 It has been reported to be between 10% and 20% but higher with systematic screening, and as high as 65% using fifth generation hsTnT, depending on variable diagnostic criteria.5,6 Preoperative risk factors for MINS include older age, emergency surgery, heart disease, hypertension, and chronic kidney disease. Intraoperative risk factors include hypotension and tachycardia.

TABLE 36-1Etiologies of Troponin Elevation

The importance of MINS is that it is associated with an increased 30-day risk of mortality, heart failure, and stroke. The mortality rate ranges from 8% to 13% and increases with increasing levels of troponin.7 Most patients are asymptomatic.

MANAGEMENT

Because there are multiple causes for troponin elevation, MINS cannot be treated as a single entity, and treatment needs to ...

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