Coronary artery and cardiac disease in patients with type 2 myocardial infarction: A prospective cohort study

Background: Type 2 myocardial infarction is caused by myocardial oxygen supply-demand imbalance and its diagnosis is becoming increasingly common with the advent of high-sensitivity cardiac troponin assays. Although this diagnosis is associated with poor outcomes, there remains widespread uncertainty and confusion amongst clinicians as to how to investigate and to manage this heterogenous group of patients with type 2 myocardial infarction.
Methods: In a prospective cohort study, 8,064 consecutive patients with increased cardiac troponin concentrations were screened to identify patients with type 2 myocardial infarction. We excluded patients with frailty or renal or hepatic failure. All study participants underwent coronary (invasive or computed tomography angiography) and cardiac (magnetic resonance imaging or echocardiography) imaging, and the underlying causes of infarction were independently adjudicated. The primary outcome was the prevalence of coronary artery disease.
Results: In 100 patients with a provisional diagnosis of type 2 myocardial infarction (median age 65 [interquartile range, 55-74] years, 57% women), coronary and cardiac imaging reclassified the diagnosis in seven patients: type 1 or 4b myocardial infarction in five and acute myocardial injury in two patients. In those with type 2 myocardial infarction, median cardiac troponin I concentrations were 195 [62-760] ng/L at presentation and 1,165 [277-3,782] ng/L on repeat testing. The prevalence of coronary artery disease was 68% (63/93), which was obstructive in 30% (28/93). Infarct-pattern late gadolinium enhancement or regional wall motion abnormalities were observed in 42% (39/93) and left ventricular systolic dysfunction in 34% (32/93). Only ten patients had both normal coronary and normal cardiac imaging. Coronary artery disease and left ventricular systolic dysfunction were previously unrecognized in 60% (38/63) and 84% (27/32) respectively, with only 33% (21/63) and 19% (6/32) on evidence-based treatments.
Conclusions: Systematic coronary and cardiac imaging of patients with type 2 myocardial infarction identified coronary artery disease in two-thirds and left ventricular systolic dysfunction in one-third of patients respectively. Unrecognized and untreated coronary or cardiac disease is seen in most patients with type 2 myocardial infarction presenting opportunities for initiation of evidence-based treatments with major potential to improve clinical outcomes.