Many patients with type 2 myocardial infarction (MI) have undiagnosed coronary artery disease (CAD) or left ventricular impairment on coronary and cardiac imaging, according to the results of the DEMAND-MI (Determining the Mechanism of Myocardial Injury and Role of Coronary Disease in Type 2 Myocardial Infarction) trial published in the journal Circulation.¹

The prospective observational cohort DEMAND-MI trial screened more than 8000 patients with raised high-sensitivity cardiac troponin I levels for type 2 MI. Frail patients or those with advanced liver or kidney failure were not included in the study. A total of 108 patients were enrolled, of whom 100 with a provisional diagnosis of type 2 MI underwent coronary (invasive or CT angiography) and cardiac (MRI or echocardiography) imaging. Subsequently, seven patients were reclassified as acute nonischemic myocardial injury (2 patients), type 4b MI due to stent thrombosis (1 patient) and type 1 MI due to atherosclerotic plaque rupture or thrombosis (4 patients); 93 patients were determined to have type 2 MI and were included in the final analysis; their average age was 66 years.

The median baseline cardiac troponin I levels were 195 ng/L (62–760 ng/L); these levels increased to a peak of 1165 ng/L (277–3782 ng/L) on repeat testing.

On imaging, 63 of the 93 patients (68%) had evidence of coronary artery disease, which was obstructive (plaque) in 28 out of the 93 (30%) patients. Thirty-nine patients (42%) had infarct-pattern late gadolinium enhancement or regional wall motion abnormalities, while 32 patients (34%) had left ventricular systolic dysfunction. Only 21 of the 63 patients with CAD were on treatment; likewise, only 6 of the 32 patients with left ventricular systolic dysfunction were being treated for it. CAD was undiagnosed in 60% of patients, while left ventricular systolic dysfunction was undiagnosed in 84%.

Just 10 patients had normal coronary and cardiac imaging.

Type 2 MI is characterized by the rise and decline of cardiac biomarkers. The myocardial injury is similar but does not meet clinical criteria for MI since the MI occurs secondary to ischemia due to either increased oxygen demand or decreased supply, e.g., coronary artery spasm, coronary embolism, anemia, arrhythmias, hypertension or hypotension.” ^2,3

The findings of this trial suggest that invasive or noninvasive coronary and cardiac imaging should routinely be considered in patients with clinical diagnosis of type 2 MI to detect hitherto undiagnosed CAD and left ventricular dysfunction. Most patients with type 2 MI had unrecognized and untreated coronary or cardiac disease and cardiac imaging led to reclassification of the diagnosis in 7 of the 100 patients evaluated. Imaging provides an opportunity for initiation of appropriate treatment to improve patient outcomes. In patients with no evidence of infarction or CAD on cardiac imaging, anti-atherosclerotic treatment may not help the patient and “in this setting, the value of a diagnosis of type 2 myocardial infarction is questionable”, write the authors.

References

1. Bularga A, et al. Coronary artery and cardiac disease in patients with type 2 myocardial infarction: a prospective cohort study. Circulation. 2022 Mar 28. doi: 10.1161/CIRCULATIONAHA.121.058542.
2. Diagnosing type 2 myocardial infarction. May 2016. https://www.acc.org/latest-in-cardiology/articles/2016/05/18/13/58/diagnosing-type-2-myocardial-infarction.
3. Smilowitz NR, et al. Treatment and outcomes of type 2 myocardial infarction and myocardial injury compared with type 1 myocardial infarction. Coron Artery Dis. 2018 Jan;29(1):46-52.