By Professor Stefan Agewall
A sizeable proportion of MIs, ranging between 1% and 14%, occur in the absence of obstructive coronary artery disease. The diagnostic criteria of MINOCA fulfill the universal criteria of myocardial infarction, but without coronary artery stenosis ≥50% in any potential IRA and with no clinically overt specific cause for the acute presentation.
MINOCA is a working diagnosis and should lead the treating physician to investigate underlying causes. Failure to identify the underlying cause may result in inadequate and inappropriate therapy in these patients. There are disparate aetiologies causing MINOCA and they can be grouped into:
- Secondary to epicardial coronary artery disorders (e.g. atherosclerotic plaque rupture, ulceration, fissuring, erosion, or coronary dissection with non-obstructive or no CAD) (MI type 1)
- Imbalance between oxygen supply and demand (e.g. coronary artery spasm, and coronary embolism) (MI type 2)
- Coronary endothelial dysfunction (e.g. microvascular spasm) (MI type 2)
- Secondary to myocardial disorders without involvement of the coronary arteries (e.g. myocarditis or Takotsubo cardiomyopathy).
The identification of the underlying cause of MINOCA should lead to specific treatment strategies. Although the outcome of MINOCA strongly depends on the underlying cause, its overall prognosis is serious, with a 1-year mortality of about 3.5%. To determine the cause of MINOCA, the use of additional diagnostic tests beyond coronary angiography is recommended. In general, after ruling out obstructive CAD in a patient presenting with MI, a LV angiogram or echocardiography should be considered in the acute setting to assess wall motion or pericardial effusion. In addition, if any of the possible aetiologies described above is suspected, additional diagnostic tests may be considered.
Cardiac magnetic resonance (CMR) is a very helpful imaging technique due to its unique non-invasive tissue characterization, allowing the identification of wall-motion abnormalities, presence of oedema, and myocardial scar/fibrosis presence and pattern. Performing CMR within 2 weeks after onset of symptoms should be considered to increase the diagnostic accuracy of the test for identifying the aetiological cause of MINOCA.
Presented at the 22nd Annual Meeting of the International Society of Cardiovascular Pharmacotherapy (ISCP), 24th-25th August 2017. Barcelona, Spain.