MINOCA (Myocardial Infarction with Non-Obstructive Coronary Arteries)

Definition:

MINOCA is defined as an acute myocardial infarction fulfilling the universal MI criteria, with coronary angiography showing no obstructive coronary artery disease (no stenosis ≥50%) and no alternative non-ischemic explanation at the time of angiography. It is a working diagnosis rather than a final one.

Epidemiology

• Accounts for ~5–10% of all myocardial infarctions

• More common in women and younger patients

• Prognosis is not benign and carries a significant risk of recurrent events and mortality

Diagnostic Criteria (ESC-based)

According to the European Society of Cardiology, all of the following must be present:

1. Clinical evidence of acute myocardial infarction

– Ischemic symptoms

– ECG changes consistent with MI

– Rise and/or fall of cardiac troponin

2. Non-obstructive coronary arteries on angiography (<50% stenosis)

3. No overt alternative diagnosis at presentation (e.g. sepsis, pulmonary embolism)

Pathophysiological Mechanisms

MINOCA is heterogeneous and may result from coronary or non-coronary causes.

Coronary Causes

• Plaque disruption (rupture or erosion)

• Coronary artery spasm (epicardial vasospasm)

• Coronary microvascular dysfunction

• Coronary thromboembolism

• Spontaneous coronary artery dissection (SCAD)

Non-Coronary Cardiac Causes

• Myocarditis

• Takotsubo syndrome

• Other cardiomyopathies

Extra-Cardiac Mimickers (to exclude)

• Pulmonary embolism

• Severe anemia

• Sepsis

• Stroke or hypertensive emergency

Diagnostic Algorithm (Guideline-Directed)

Step 1: Confirm MI

• Symptoms + ECG + troponin dynamics

Step 2: Coronary Angiography

• No obstructive CAD (<50%)

Step 3: Exclude Non-Ischemic Injury

• Early Cardiac MRI (Class I recommendation)

– Differentiates infarction, myocarditis, and Takotsubo

– Assesses edema, fibrosis, and scar pattern

Step 4: Identify Coronary Mechanism (if CMR confirms MI)

• Intravascular imaging (OCT/IVUS)

– Detect plaque rupture or erosion

• Coronary vasomotor testing

– Acetylcholine or ergonovine for spasm

• Evaluation for embolic sources

– Atrial fibrillation

– LV thrombus

– Valvular disease

Management Principles

Management should be mechanism-specific rather than uniform.

General Measures

• Treat as MI until diagnosis clarified

• Aggressive risk factor modification

• Lifestyle optimization

Antiplatelet Therapy

• Aspirin recommended if plaque disruption suspected

• Dual antiplatelet therapy individualized (limited evidence)

Statins

• Recommended in most patients, especially if atherosclerosis is identified or suspected

Beta-Blockers

• Consider in LV dysfunction, arrhythmias, or Takotsubo (individualized)

ACE Inhibitors / ARBs

• Indicated in LV dysfunction, hypertension, or diabetes

Calcium Channel Blockers

• First-line for coronary vasospasm

Anticoagulation

• Reserved for documented thromboembolism or AF

Prognosis

• 1-year mortality ~3–5%

• Recurrent MI and heart failure risk comparable to obstructive MI

• Prognosis depends on underlying mechanism

Key Take-Home Points

• MINOCA is a diagnosis requiring systematic evaluation

• Cardiac MRI is central to diagnosis

• Treatment must be etiology-driven

• Prognosis is not benign and warrants close follow-up

• A structured, guideline-based approach improves outcomes

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