Coronary Artery and Cardiac Disease in Patients With Type 2 Myocardial Infarction: A Prospective Cohort Study

Abstract

Background: Type 2 myocardial infarction is caused by myocardial oxygen supply-demand imbalance, and its diagnosis is increasingly common with the advent of high-sensitivity cardiac troponin assays. Although this diagnosis is associated with poor outcomes, widespread uncertainty and confusion remain among clinicians as to how to investigate and manage this heterogeneous group of patients with type 2 myocardial infarction. Methods: In a prospective cohort study, 8064 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 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 years [interquartile range, 55–74 years]; 43% women), coronary and cardiac imaging reclassified the diagnosis in 7 patients: type 1 or 4b myocardial infarction in 5 and acute myocardial injury in 2 patients. In those with type 2 myocardial infarction, median cardiac troponin I concentrations were 195 ng/L (interquartile range, 62–760 ng/L) at presentation and 1165 ng/L (interquartile range, 277–3782 ng/L) on repeat testing. The prevalence of coronary artery disease was 68% (63 of 93), which was obstructive in 30% (28 of 93). Infarct-pattern late gadolinium enhancement or regional wall motion abnormalities were observed in 42% (39 of 93), and left ventricular systolic dysfunction was seen in 34% (32 of 93). Only 10 patients had both normal coronary and normal cardiac imaging. Coronary artery disease and left ventricular systolic dysfunction were previously unrecognized in 60% (38 of 63) and 84% (27 of 32), respectively, with only 33% (21 of 63) and 19% (6 of 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. 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. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03338504.

Left Ventricular Remodeling after Myocardial Infarction: From Physiopathology to Treatment

“…Adverse remodeling occurs to a lower extent in this group of patients, as demonstrated by a study that showed that in more than half of the patients with a diagnosis of type 2 myocardial infarction, there was no imaging evidence of any functional consequences of myocardial infarction, such as a regional wall motion abnormality or scar formation. However, it is a known fact that these patients have a prognosis similar to those with an atherothrombotic MI, with a similar rate of future cardiovascular events [ 17 ].…”

“…Furthermore, LGE can identify microvascular obstruction after MI, by visualizing the no-reflow phenomenon [ 22 ]. Finally, CMR is extremely useful in evaluating the etiology of MINOCA, and novel CMR techniques will bring further insight into ventricular remodeling after MI [ 17 , 22 , 107 , 108 ].…”

Zooming in on the Enigmas of Type 2 Myocardial Infarction

“…Bularga et al 5 state that their “novel observations provide useful insights that will encourage clinicians to consider imaging in these patients.” I agree. However, they also state “If cardiac imaging does not identify coronary artery disease or infarction, then it is unlikely the patient will benefit from therapies targeting coronary atherosclerosis.…”

“…Bularga et al 5 state that their "novel observations provide useful insights that will encourage clinicians to consider imaging in these patients. " I agree.…”

“…In the study by Bularga et al, 5 patients were defined as having type 2 MI if they fulfilled the UDMI (except for development of new Q waves and the requirement for new regional wall motion abnormalities; see Limitations and Effects on Interpretation) and there was evidence of supply/demand imbalance. Strict cutoffs for supply/demand clinical variables, such as blood pressure, oxygen saturations, or hemoglobin concentrations were not used.…”