Myocardial infarction with no obstructive coronary artery disease: angiographic and clinical insights in patients with premature presentation

Background - Premature myocardial infarction (MI) is an increasingly prevalent cause of morbidity and mortality worldwide. A subset of patients, predominantly young women, present with MI with no obstructive coronary artery disease (MINOCA), a nomenclature gaining recognition. However, few data exist on presentation and prognosis according to the severity of coronary artery disease (CAD). Methods - We studied patients with premature (younger than 55 years of age) acute MI enrolled in a large cohort in 24 centres across Canada. Baseline clinical, psychosocial, and coronary anatomy characteristics as well as 12-month outcomes were compared between patients with MINOCA (< 50% stenosis) and patients with MI with obstructive CAD (≥ 50% stenosis; MICAD). Results - From a cohort of 1210 patients with acute coronary syndrome, we examined 998 MI patients with available angiography core lab readings: 82 (8.2%) had a MINOCA and 916 (91.8%) had a MICAD. Forty percent of patients with MINOCA were women compared with one-third with MICAD. The prevalence of traditional risk factors and chest pain at presentation was lower in MINOCA patients, yet 37% had a ST-elevation MI and 10% presented with a cardiac arrest. No evident etiology was detected in > 70% of MINOCA, but 10% presented with either spontaneous coronary dissection or Takotsubo cardiomyopathy. Although combined major adverse cardiovascular events and all-cause readmission rate was lower in the MINOCA group (14% vs 25%; adjusted hazard ratio, 0.51; 95% confidence interval, 0.28-0.93), it was not negligible. Conclusions - Patients with MINOCA present with high-risk features despite the absence of obstructive CAD. A search for etiology and eventual treatment provides a rich avenue for improving prognosis in young women with premature MI.