Myocardial infarction with non-obstructive coronary arteries as compared with myocardial infarction and obstructive coronary disease: outcomes in a Medicare population

Aim

To assess the prognostic relevance of MINOCA (myocardial infarction with non-obstructive coronary arteries).

Methods

This large observational study of patients ≥56 years presenting with an acute myocardial infarction (AMI) included a total of 286 780 admissions with AMI, of which 276 522 were unique patients, from the National Cardiovascular Data Registry CathPCI Registry for the period 2009 – 2013. MINOCA was present in 16 849 patients (5.9%)

Main results

• Mean age of the overall population was 75.6 years and female patients were more likely to present with MINOCA (77.0% vs. 41.5%; P< 0.001).
• 12-month MACE (mortality, AMI, HF and stroke) was significantly lower in MINOCA patients as compared with patients with obstructive disease (18.7% vs. 27.6%).
• Mortality (12.3% vs. 16.7%), rehospitalization for AMI (1.3% vs. 6.7%) and heart failure (5.9% vs. 9.3%) were also significantly lower, whereas the stroke rates were similar (1.6% vs. 1.4%).

Main messages

This is likely the so far largest study on the prognostic relevance of MINOCA. The main finding seems to be that although MINOCA is associated with lower rates of MACE when compared with the presence of coronary obstructive disease, it cannot be considered a benign clinical entity.

When interpreting the here presented data set, there are at least 2 issues of interest. First, mean age in this study was 75 years, which suggests that a portion of everyday MINOCA patients may have not been included in the analysis, since previous studies had shown that MINOCA patients were on average younger than patients with obstructive disease. Secondly, the underlying causes of MINOCA were not investigated. This is pertinent since patients presenting with MINOCA are notoriously a heterogenous population that have encompassed different causative mechanisms ranging from coronary athero-thrombosis (e.g. plaque fissure or erosions) to non-coronary entities such as myocarditis or Takotsubo cardiomyopathy. Importantly, these different underlying causes of MINOCA may entail different prognosis and thus warrant different treatment strategies.

In summary, this hitherto largest real-world data pool on MINOCA appears to deliver a practical message that in a patient with the discharge diagnosis of AMI but no obstructive disease on angiography, a search for an underlying cause, as well as close follow-up are mandated, considering the documented 1-year mortality rate of 12%.