What causes myocardial infarction (MI) with non-obstructive coronary arteries (NOCAs)?

From the Guidelines

Myocardial infarction (MI) with non-obstructive coronary arteries (NOCAs) is primarily caused by disparate aetiologies that can be grouped into epicardial coronary artery disorders, imbalance between oxygen supply and demand, coronary endothelial dysfunction, and myocardial disorders without involvement of the coronary arteries 1.

Causes of MINOCA

• Epicardial coronary artery disorders: atherosclerotic plaque rupture, ulceration, fissuring, erosion, or coronary dissection with non-obstructive or no CAD, which can be classified as MI type 1 1
• Imbalance between oxygen supply and demand: coronary artery spasm and coronary embolism, which can be classified as MI type 2 1
• Coronary endothelial dysfunction: microvascular spasm, which can be classified as MI type 2 1
• Myocardial disorders without involvement of the coronary arteries: myocarditis or Takotsubo syndrome, although these are now excluded from the final diagnosis of MINOCA according to the most recent scientific statement from the AHA 1

Diagnostic Criteria

The diagnosis of MINOCA is made in patients with AMI fulfilling specific criteria, including detection of a rise or fall in cardiac troponin with at least one value above the 99th percentile upper reference limit and corroborative clinical evidence of infarction, as well as non-obstructive coronary arteries on angiography 1.

Treatment Strategies

The identification of the underlying cause of MINOCA should lead to specific treatment strategies, and the use of additional diagnostic tests beyond coronary angiography is recommended, including LV angiogram or echocardiography, and CMR to identify wall motion abnormalities, presence of oedema, and myocardial scar/fibrosis presence and pattern 1.

From the Research

Causes of Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA)

• Epicardial causes:
  • Rupture or fissuring of unstable nonobstructive atherosclerotic plaque 2
  • Coronary artery spasm 2, 3
  • Spontaneous coronary dissection 2, 4
  • Cardioembolism in-situ 2
• Microvascular causes:
  • Type-2 acute myocardial infarction (AMI) due to supply-demand mismatch 2, 3
  • Takotsubo syndrome 2, 4
• Other causes:
  • Thromboembolic events 3
  • Myocarditis 4, 3
  • Autoimmune diseases 5
  • Anxiety and depression 5
  • Pregnancy, cancer, and anti-cancer therapy 5

Diagnostic Approaches

• Clinical history, electrocardiogram, echocardiography, and coronary angiography as first-level diagnostic investigations 2
• Coronary imaging with intravascular ultrasound and optical coherent tomography, coronary physiology testing, and cardiac magnetic resonance imaging for additional information 2, 4
• Multimodality imaging approach, including cardiac magnetic resonance and invasive coronary imaging, to establish the underlying cause of MINOCA 4

Risk Factors and Associated Comorbidities

• Traditional cardiovascular risk factors have a lower prevalence in MINOCA patients 2, 5
• Atypical risk factors, such as anxiety, depression, and autoimmune diseases, are more frequent in MINOCA patients 5
• Female sex, absence of hypercholesterolemia, and normal left-ventricular ejection fraction are independently predictive for MINOCA 3