Myocardial infarction with non-obstructive coronary arteries (MINOCA) is a new entity recently trending in the field of interventional cardiology. According to the latest 2017 ESC guidelines, MINOCA is a working diagnosis and is defined as non-obstructive (< 50% stenosis) infarct-related artery (IRA) demonstrated in coronary angiography in a patient diagnosed to have acute myocardial infarction (AMI) as per Universal AMI criteria.
Around 1-14% of patients with acute myocardial infarction (AMI) may have non-obstructive coronaries in coronary angiography. MINOCA occurs commonly in young women with dyslipidemia. The following are the mechanisms for causing MINOCA: (1) plaque rupture, erosion, embolism or coronary dissection involving epicardial coronary arteries; (2) coronary vasospasm leading to the imbalance between oxygen supply and demand; (3) coronary microvascular spasm; and (4) myocardial injuries like myocarditis or Takotsubo syndrome.
A few additional tests, besides coronary angiography, may provide the etiological diagnosis of MINOCA.
- A detailed echocardiography may be performed initially.
- Apical ballooning in left ventricular angiography may suggest Takotsubo cardiomyopathy but normalization of findings during follow up is required for the diagnosis.
- Intravascular Ultrasound (IVUS) and Optical Coherence Tomography (OCT) may unravel coronary dissection, thrombosis, plaque rupture, plaque fissure etc.
- Provocative spasm tests with acetylcholine or ergonovine are useful to rule out coronary artery spasm. Pressure studies may reveal coronary microvascular dysfunction.
- Cardiac MRI may identify subendocardial infarction, myocarditis etc by providing information like wall motion abnormalities, delayed myocardial enhancement infarction, presence of edema, myocardial scar/fibrosis etc.
- Further useful investigations would be blood tests like D-dimer to rule out the possibility of pulmonary embolism, screening for thrombophilia disorders and inflammatory marker levels; screening for substance abuse like cocaine; endomyocardial biopsy for fulminant myocarditis.
The 1-year mortality of MINOCA is 3.5% and hence patients with MINOCA should not be ignored as those with the non-obstructive coronary disease because the prognosis is not great.3 Patients with MINOCA should be managed like AMI patients with the single-vessel disease or double-vessel disease.
Dr. Babu Ezhumalai
The author is MD, DM, FNB, FACC, FESC, FSCAI,(Cardiology) and is Consultant Heart Failure & Interventional Cardiologist, Fortis Malar Hospital. He is a member Editorial Board, Cardiology at Specialty Medical Dialogues.