MINS: Myocardial Injury After Noncardiac Surgery
MINS stands for Myocardial Injury After Noncardiac Surgery, a condition defined by elevated cardiac troponin levels (>99th percentile upper reference limit) of presumed ischemic origin occurring during or within 30 days after noncardiac surgery. 1
Definition and Diagnostic Criteria
MINS requires at least one elevated cardiac troponin (cTn) measurement above the 99th percentile of the upper reference limit, attributed to ischemic causes rather than nonischemic etiologies like pulmonary embolism, sepsis, acute heart failure, or stroke. 1
The critical distinction of MINS is that it encompasses both symptomatic and asymptomatic myocardial injury, including both Type 1 and Type 2 myocardial infarction. This broad definition exists because surgical patients often cannot report ischemic symptoms due to anesthesia, analgesics, or overwhelming surgical site pain. 1
Clinical Significance and Mortality Impact
MINS carries substantial mortality risk with approximately 10% 30-day mortality overall, making it a major contributor to postoperative deaths. 1 The mortality risk is directly proportional to peak troponin concentrations:
- 17% mortality in the highest troponin quartile
- 1% mortality in the lowest quartile
- 34% population attributable risk for 30-day postoperative mortality 1
Critically, even among the 80-90% of MINS patients without any ischemic symptoms or ECG changes, 30-day mortality remains substantial. 1 Patients with elevated postoperative troponin without ischemic features have a 3-fold increased hazard of 30-day mortality, while those with ischemic features have a 5-fold increased hazard. 1
Epidemiology
MINS occurs in approximately 20% of patients undergoing major noncardiac surgery. 1 The incidence increases dramatically with age, reaching 23.8% in patients aged 75 years or older. 2
Most importantly, 68-90% of MINS cases would go completely undetected without routine troponin monitoring, as the majority are asymptomatic. 2, 3
Risk Factors and Predictors
Key predictors include:
- Cardiovascular risk factors and established cardiovascular disease
- Chronic kidney disease
- Urgent or emergent surgery
- Heart failure
- ASA Score ≥3
- Hemoglobin ≤12 g/dL (pre- and postoperatively) 1, 3
Atherosclerotic coronary artery disease is the presumed underlying mechanism in most cases. 1
Surveillance Recommendations
For high-risk patients (those with cardiovascular risk factors, established disease, or undergoing major surgery), postoperative troponin surveillance is recommended. 1 Serial measurements during the first 3 postoperative days are optimal, with baseline preoperative values helpful for determining if injury is acute or chronic. 1
For low-risk patients undergoing low-risk noncardiac surgery, routine troponin screening is not indicated unless signs or symptoms of myocardial ischemia develop. 1
Both conventional fourth-generation and high-sensitivity troponin assays are acceptable for surveillance. 1
Management Approach
Patients diagnosed with MINS should receive outpatient cardiology follow-up for cardiovascular risk factor optimization, particularly those not previously known to have excess cardiovascular risk. 1
Management considerations include:
- Antithrombotic therapy may be considered to reduce thromboembolic events 1
- Intensification of guideline-directed medical therapy (statins, antiplatelet agents, beta-blockers)
- Cardiac imaging (echocardiography shows regional wall motion abnormalities in 23% of previously undiagnosed patients; nuclear stress imaging shows ischemia in 39%) 4
- Minimizing ongoing triggers: hypotension, tachycardia, anemia, inadequate pain control 5, 6
Early cardiology consultation after MINS diagnosis is associated with reduced mortality. 1
Critical Clinical Pitfall
The most dangerous pitfall is assuming that absence of chest pain or ECG changes means absence of myocardial injury. The vast majority of MINS is silent, and without systematic troponin surveillance in at-risk patients, these high-mortality events will be missed entirely. 2, 3