What MINOCA Means
MINOCA stands for Myocardial Infarction with Non-Obstructive Coronary Arteries—a clinical syndrome where a patient experiences a true heart attack (meeting all criteria for acute myocardial infarction) but coronary angiography reveals no significant blockages (less than 50% stenosis) in the epicardial coronary arteries. 1
Diagnostic Criteria
To diagnose MINOCA, three specific requirements must be met 1:
Confirmed acute myocardial infarction per the Fourth Universal Definition:
- Elevated cardiac troponin (at least one value >99th percentile) with a rise and/or fall pattern
- PLUS at least one of:
- Symptoms of myocardial ischemia
- New ischemic ECG changes
- Development of pathological Q waves
- Imaging evidence of new loss of viable myocardium or new regional wall motion abnormalities
- Identification of coronary thrombus on angiography or autopsy
No obstructive coronary artery disease (≥50% stenosis) in any epicardial artery, and no overlooked forms of obstructive disease like spontaneous coronary artery dissection or embolus
No clinically overt alternative cause for the acute presentation (excludes myocarditis and Takotsubo cardiomyopathy—these are "MINOCA mimickers")
Clinical Context and Importance
MINOCA accounts for 6-8% of all myocardial infarctions and occurs more frequently in non-ST elevation MI than STEMI 2. Up to 60% of cases occur in women, disproportionately affecting younger and middle-aged women 2.
This is NOT a Benign Condition
MINOCA carries substantial prognostic risk despite the absence of obstructive coronary disease 3. The composite rate of mortality or nonfatal MI is more than twice that of patients without previous atherosclerotic cardiovascular disease (4.6% vs 2.2%), though approximately one-third that of MI with obstructive CAD (4.6% vs 14.3%) 1. The 5-year mortality hazard risk is 1.93 times higher in MINOCA patients compared to those with obstructive MI-CAD 1.
Underlying Mechanisms
MINOCA is a heterogeneous syndrome with multiple potential causes 1:
Atherosclerotic causes (approximately two-thirds of cases):
- Plaque rupture, erosion, or calcific nodules with thrombus formation and distal embolization
- These patients have similar pathophysiology and risk factors to obstructive MI
Non-atherosclerotic coronary causes:
- Epicardial coronary vasospasm (>90% demonstrable with acetylcholine or ergonovine provocative testing)
- Spontaneous coronary artery dissection (SCAD): Accounts for ~4% of all MIs, 40% of MIs in women <50 years, and 14-43% of pregnancy-related MIs
- Coronary microvascular dysfunction (CMD)
- Thromboembolism
Important exclusions:
- Type 2 MI (supply-demand mismatch from tachyarrhythmia, sepsis, anemia, hypotension)
- Non-ischemic causes (Takotsubo syndrome, myocarditis)
Evolving Nomenclature
Recent 2024 guidelines propose reclassifying MINOCA under the broader umbrella of "Non-Acute Myocardial Ischemic Syndromes" (NAMIS) rather than traditional "coronary syndromes," emphasizing that the term "non-acute" better conveys the persistent and substantial residual prognostic risk that occurs over time in these patients 3. This new classification system distinguishes between acute myocardial ischemic syndromes (AMIS) and NAMIS, with MINOCA falling under NAMIS alongside ischemia with non-obstructive coronary arteries (INOCA) 3.
Critical Clinical Pitfall
Despite optimal workup, the cause of MINOCA remains undiagnosed in 8-25% of cases 1. However, when both optical coherence tomography (OCT) and cardiac magnetic resonance (CMR) are performed, 85% of patients have an identified abnormality on one or both studies 1. CMR is particularly valuable for prognosis, with 10-year MACE rates varying dramatically by diagnosis: normal (3.5%), acute MI (47%), myocarditis (24%), or non-ischemic cardiomyopathy (50%) 1.