Myocardial infarction with non-obstructive coronary arteries: dealing with pears and apples

Myocardial infarction with non-obstructive coronary arteries (MINOCA) is a syndrome characterized by clinical evidence of acute myocardial infarction (AMI) according to the fourth universal definition with normal or near-normal coronary arteries on angiography. Data from large contemporary registries demonstrate that the prevalence of MINOCA among MI patients is 6–8%. The absence of obstructive coronary stenosis along with the results deriving from early studies supported the common feeling among physicians that the prognosis of MINOCA was benign. Results from more recent studies did not confirm this belief. Indeed, in an excellent meta-analysis, Pasupathy et al. demonstrated that allcause mortality at 1 year was lower in MINOCA compared with myocardial infarction and obstructive coronary artery disease (MICAD) (4.7% vs. 6.7%), but not negligible considering that patients with angina without recent AMI and obstructive coronary artery disease have an annual mortality of 0.3%. Of note, in the prospectively conducted Korean MI Registry, MINOCA patients had an equivalent 12-month all-cause mortality to those with an AMI associated with singleor double-vessel coronary artery disease. Furthermore, a retrospective analysis of 13 800 patients presenting with non-ST elevation MI enrolled in the ACUITY trial demonstrated that MINOCA had a higher mortality at 1 year (4.7% vs. 3.6%) compared with MICAD, although mainly driven by non-cardiac mortality. Longterm prognosis of MINOCA is also not favourable. Indeed, in an observational study of MINOCA patients recorded in the SWEDEHEART registry, at a mean follow-up of 4.1 years, mortality was 13.4% (with only 43.0% of deaths classified as cardiovascular), 7.1% of patients experienced another myocardial infarction, 4.3% had an ischaemic stroke, 6.4% were hospitalized for heart failure, and hospitalization for bleeding occurred in 3.6%. In this issue of the European Heart Journal, Dreyer et al. assessed the prognosis of MINOCA compared with MICAD at 1 year in an observational cohort study enrolling patients aged >65 years (mean age 75.6 years) from the National Cardiovascular Data Registry CathPCI Registry with linkage to the Centers for Medicare and Medicaid Services (CMS) claims data. This study included 286 780 patients admitted with a diagnosis of AMI, with 5.9% of patients presenting MINOCA. The authors have to be congratulated for publishing the hitherto largest study evaluating the prognosis of patients with MINOCA. The authors demonstrated that the 12-month rates of major adverse cardiac events (MACEs) (18.7% vs. 27.6%), mortality (12.3% vs. 16.7%), and re-hospitalization for AMI (1.3% vs. 6.1%) and for heart failure (5.9% vs. 9.3%) were significantly lower for MINOCA vs. MICAD patients, while they were similar for rehospitalization for stroke (1.6% vs. 1.4%). Thus, this study clearly confirms that MINOCA patients have a guarded prognosis, with a significant risk of mortality and recurrent MACEs, although this is lower as compared with that observed in MICAD. The study by Dreyer et al. enrolled patients >65 years old to enable linkage to CMS data and, as a consequence, the mean age of the study population ( 75 years) is significantly higher compared with that in previous MINOCA studies. Indeed, MINOCA patients are usually younger, and a large systematic review showed that the average age of patients with MINOCA was lower as compared with that of patients with MICAD. Not surprisingly, an older age represents an independent predictor for all-cause mortality and occurrence of MACEs in MINOCA. At the other extreme, in the VIRGO study enrolling 2690 younger patients aged <55 years, AMI patients demonstrated a similar low 12-month mortality for MINOCA and MICAD (0.6% vs. 2.3%), along with a higher prevalence of MINOCA (11.1%) compared with other registries.