Myocardial injury after noncardiac surgery is silent

Why it matters

A patient in the PACU after noncardiac surgery who is comfortable, warm and talking can be in the middle of a myocardial injury that will not announce itself. The VISION high-sensitivity troponin analysis found that 93.1% of patients meeting MINS criteria (3633 of 3904) had no ischaemic symptom devereaux-2017. The injury is common, too: 17.9% of the cohort (95% CI 17.4 to 18.4) met the criteria devereaux-2017.

The consequence of getting this wrong is a category error. Symptoms are treated as the screen, so the absence of symptoms is read as the absence of injury, and the patient with the highest population-attributable risk of any perioperative complication goes home undiagnosed botto-2014.

Mechanism

Surgery imposes a sustained supply-demand stress on the myocardium: tachycardia, catecholamine release, inflammation, hypercoagulability, anaemia and hypotension, often together and often for days. Troponin leaks from myocytes that are injured under that stress. Whether most MINS represents supply-demand mismatch in a heart with fixed coronary disease, or plaque rupture, or a mixture whose proportions vary by patient, is not settled, and the status chip on this page says so. What is settled is that the injury is measurable by troponin and mostly not by symptoms, because the stress is diffuse and the patient is analgesed, sedated or both.

Evidence

The definition comes from the 2017 VISION analysis, in which fifth-generation high-sensitivity troponin T was measured on the first three postoperative days devereaux-2017. MINS was an hsTnT of 20 to less than 65 ng/L with an absolute change of at least 5 ng/L, or an hsTnT of 65 ng/L or more, judged due to ischaemia devereaux-2017. Thirty-day mortality rose with the peak value: 0.5% below 20 ng/L, 3.0% at 20 to less than 65 ng/L, 9.1% at 65 to less than 1000 ng/L, and 29.6% at 1000 ng/L or more, against an overall 30-day mortality of 266 patients (1.2%) devereaux-2017.

The earlier VISION analysis used a fourth-generation troponin T assay and is superseded by the 2017 thresholds; it is on this page only to mark that the assay generation, and therefore the numbers, changed devereaux-2012.

Botto 2014, in 15,065 patients aged 45 or older, defined MINS as a peak troponin T of 0.03 ng/mL or more judged due to ischaemia and found it in 1200 patients (8.0%) botto-2014. Of those, 58.2% would not have met the universal definition of myocardial infarction botto-2014. MINS carried an adjusted hazard ratio for 30-day mortality of 3.87 (95% CI 2.96 to 5.08), and the highest population-attributable risk of any perioperative complication, 34.0% (95% CI 26.6 to 41.5) botto-2014.

What follows a positive result is the subject of a scientific statement from the American Heart Association ruetzler-2021. Its surveillance population, surveillance interval and evidence classes have not yet been extracted from the held document, so this page does not quote them.

What this does not show

Every source on this page is a cohort or a consensus statement. VISION is a prospective cohort, Botto 2014 is a cohort, and the AHA document is a statement devereaux-2017 botto-2014 ruetzler-2021. The claim that MINS is mostly silent and strongly associated with death is fully carried by that evidence. The claim that finding MINS and acting on it improves anything is not carried by anything here, and no trial on this page tests it. The obligation the day describes is an obligation to know, not a demonstrated benefit from knowing.

The two VISION eras do not share numbers. The incidence, the thresholds and the symptom proportion all changed when the assay changed from fourth-generation to high-sensitivity troponin T devereaux-2012 devereaux-2017. A figure quoted for MINS without its assay generation is a figure without a denominator. The 2017 values are the current ones.

Botto 2014 has not yet been retrieved in full; its figures on this page are from the indexed abstract, and the 30-day outcome by troponin stratum from that paper is not available here botto-2014.

At the bedside

Do not use the absence of chest pain, dyspnoea or ECG change to rule out myocardial injury after noncardiac surgery. The sources on this day say that the large majority of injured patients have none of those devereaux-2017.

Know which assay your laboratory runs and which thresholds apply to it, because the definition is assay-specific devereaux-2017. [PRACTICE VARIES: whether and in whom postoperative troponin is measured routinely is an institutional decision; some centres screen high-risk patients on the first postoperative days, others measure only on clinical suspicion.]

If you decide not to measure, say what you are deciding: that you are willing not to know. If you decide to measure, know before the result arrives what you will do with a positive one, because the value of the test is entirely in what follows it, and the scientific statement that describes that pathway is the next thing to read ruetzler-2021.

Check yourself

Three items. Every option carries an explanation. Progress is not saved.