Most patients with type 2 myocardial infarction (T2MI) have non-obstructive coronary artery disease (CAD), as opposed to obstructive CAD, a new study shows. This information was reported by Cian P. McCarthy, MB, BCh, BAO, SM, of Massachusetts General Hospital, Boston, and colleagues, in a manuscript published Friday online in the Journal of the American College of Cardiology. Coronary blood flow is unbalanced in patients with T2MI, and the prognosis is often grim for the roughly 250,000 patients in the U.S. with T2MI. Patients with T2MI are less likely to be evaluated for CAD despite the high risk of cardiovascular events associated with CAD. This study investigated the characteristics and comorbidity rates of CAD in patients with T2MI. Patients (n=50, 50% female, mean age=68.0±11.4 years; 84.0% white, 14.0% Black, 2.0% other) in this prospective, single-center, investigator-initiated, observational cohort study were enrolled if they met the Fourth Universal Definition of Myocardial Infarction criteria for T2MI. Patients with other MI subtypes were excluded from the study. Computed tomography angiography (CTA), fractional flow reserve derived with coronary CTA (FFRCT) and plaque volume analyses were performed on each patient. Coronary plaque was observed in 92% of patients, and atherosclerotic risk factors were common overall. Moderate or greater stenosis (≥50%; 42% of patients) and obstructive disease (≥50% left main stenosis or ≥70% stenosis in any other epicardial coronary artery; 26% of patients) were also observed. Diagnosis of CAD did not change based on the cause of T2MI (p=0.54). Hemodynamically focal stenosis was seen in 13 patients by use of FFRCT, and 21 patients had ≥50% stenosis. Of these 21 patients, FFRCT excluded lesion-specific hemodynamically significant stenosis in eight patients. There are several limitations to this study. First, its prospective nature does not eliminate selection bias. Second, reasons for nonenrollment in the study were multifactorial, potentially influencing the investigation of CAD prevalence. Additionally, the results may not be generalizable to MI patients who met the exclusion criteria for this study. The investigators concluded that patients with T2MI frequently have CAD but do not often have obstructive CAD or hemodynamically significant stenosis. Multifactorial mediators likely contribute to ischemia in patients with T2MI. In an accompanying editorial, C. Noel Bairey Merz, MD, Martha Gulati, MD, and Janet Wei, MD, of the Cedar-Sinai Medical Center, Los Angeles, discussed ST-segment elevation MI (STEMI) and the increasing prevalence of CAD in this patient population. “Because intracoronary imaging with intravascular ultrasound or optical coherence tomography and cardiac magnetic resonance imaging were not performed in the current study, mechanisms of T1MI such as atherosclerotic plaque rupture, plaque erosion with thrombosis, embolization, and dissection cannot be ruled out,” the editorialists wrote. They also noted that the diagnosis of T2MI is underestimated. The editorialists added that the current guidelines for T2MI, statins with or without low-dose aspirin therapy, needs to be developed more with these studies. They said a large study—Women’s Ischemia Syndrome Evaluation (WISE)—gave more evidence for different treatment options and observing the prevalence of CAD in patients with T2MI, especially in women. “Do we have sufficient knowledge currently to create guidelines for basic T2MI diagnosis and treatment? Understanding T2MI pathophysiologies shown by the WISE and other studies suggest that we may. Thank goodness for the women!” concluded the editorialists. Sources: McCarthy CP, Murphy SP, Amponsah DK, et al. Coronary Computed Tomographic Angiography in Patients With Type 2 Myocardial Infarction. J Am Coll Cardiol. 2023 September 29 (Article in Press). Bairey Merz CN, Gulati M, Wei J. Understanding T2MI: Thank Goodness for the Women. J Am Coll Cardiol. 2023 September 29 (Article in Press). Image Credit: Photographee.eu – stock.adobe.com