MYOCARDIAL INFARCTION WITH NONOBSTRUCTIVE CORONARY ARTERIES, acute myocardial infarction in the absence of significant coronary artery obstruction.
What is MINOCA?
Diagnosis and management of such cases have been challenging, so frequently MINOCA remains under-recognised, under-diagnosed and under-treated.
Patients with MINOCA present similarly to those with acute myocardial infarction with obstructive coronary arteries including symptoms of cardiac ischemia and elevated troponins. However, MINOCA patients lack angiographically significant coronary artery obstruction and an immediately clear cause of presentation.They typically present with non-ST segment elevation myocardial infarction (NSTEMI) on ECG.
In addition, MINOCA patients are typically younger and more often women. There are many etiologies of MINOCA including coronary artery spasm, coronary microvascular dysfunction, plaque disruption, spontaneous coronary thrombosis or emboli, spontaneous coronary artery dissection, or cardiomyopathies.
MINOCA mechanisms can be thought of as malfunctions of epicardial vessels and/or coronary microcirculation. Epicardial causes include coronary artery spasms or transient and partial thrombosis at the site of a nonobstructive plaque. Microvascular causes include coronary microvascular dysfunctions like Cardiac Syndrome X and angina pectoris with normal coronary arteries.
This does not provide an exhaustive list of possible causes; other etiologies include spontaneous coronary artery dissection, coronary artery embolism, or even pulmonary embolism. It should be noted that other pathologies, particularly stress-induced cardiomyopathy (Takotsubo syndrome) and myocarditis, can mimic MI/MINOCA. While excluded from the definition of MINOCA, these syndromes should remain on the differential when evaluating patients with presentations suggesting MI/MINOCA.
congenital variant where epicardial coronary arteries dive into the myocardium and undergo dynamic compression during systole. While initially thought to be a benign condition, it has more recently been investigated as a cause of angina and MINOCA.
Coronary plaque disruption
Coronary plaque disruption patophysiology is similar to that of MI with obstructive coronary artery disease; however, to be considered MINOCA, the obstruction must be less than 50% and the transient and partial thrombosis at the site of the non-obstructive plaque must be followed by subsequent spontaneous fibrinolysis of the clot.
Coronary microvascular dysfunction
Also known as cardiac syndrome X, microvascular angina is a coronary microvascular dysfunction characterized by transient myocardial ischemia, as seen by ST-segment changes, in the absence of obstructive coronary artery disease and epicardial spasms.
Spontaneous coronary artery dissection
Spontaneous coronary artery dissection (SCAD) is an uncommon cause of acute MI overall, it is a relatively common mechanism of acute MI in women under age 50. SCAD should be considered in younger women with an unexplained ACS or sudden cardiac death.
Coronary artery spasm
Also known as vasospastic angina and previously known as Prinzmetal or variant angina characterized by transient episodes of resting angina that is attributed to focal or diffuse epicardial coronary artery vasospasms resulting in a high-grade obstruction.
MI attributed to coronary thromboembolism is more common in younger women, and prevalence also varies with race and ethnicity, especially those that are associated with hypercoagulable disorders.