What is the initial management for a patient diagnosed with Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA)?

Initial Management of Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA)

For patients diagnosed with MINOCA, a systematic diagnostic algorithm is recommended to differentiate true MINOCA from alternative diagnoses, with cardiac magnetic resonance imaging (CMR) being essential for all patients without an obvious underlying cause. 1

Diagnostic Approach

Step 1: Confirm MINOCA Diagnosis

MINOCA is diagnosed when a patient meets all three criteria:

• Acute myocardial infarction (elevated troponin with clinical evidence of infarction)
• Non-obstructive coronary arteries on angiography (<50% stenosis in any major epicardial vessel)
• No specific alternate diagnosis for the clinical presentation 1

Step 2: Initial Assessment

• Perform proper assessment of left ventricular wall motion using:
  • LV angiography (if renal function permits)
  • Echocardiography
• Regional wall motion abnormalities may indicate an epicardial cause or other specific causes 1

Step 3: Advanced Imaging

• CMR is recommended for all MINOCA patients without an obvious underlying cause (Class I, Level B recommendation) 1
  • CMR can identify underlying causes in up to 87% of MINOCA patients
  • Helps differentiate between Takotsubo syndrome, myocarditis, and true MI 1

Step 4: Additional Diagnostic Tests

• Consider intracoronary imaging with IVUS or OCT when:
  • Thrombus is suspected
  • Plaque rupture or erosion is suspected
  • Spontaneous coronary artery dissection (SCAD) is suspected 1
• Consider provocative testing for coronary vasospasm 2
• Rule out pulmonary embolism with:
  • D-dimer testing
  • BNP
  • CT pulmonary angiography (when appropriate) 1

Management Approach

Immediate Management

1. Manage according to disease-specific guidelines once the underlying cause is established (Class I, Level C recommendation) 1
2. For MINOCA of unknown cause (occurs in 8-25% of cases):
   • Consider treatment targeting the most probable causes:
     • Vasospastic angina
     • Coronary plaque disruption
     • Thromboembolism 1

Pharmacological Management

• For MINOCA of unknown cause, secondary prevention with atherosclerotic disease medications may be considered (Class IIb, Level C recommendation) 1
• Consider dual antiplatelet therapy (DAPT) based on pathophysiological considerations, though evidence is limited 1
• Caution with intensified antiplatelet therapy: There is a signal of possible harm with double-dose clopidogrel compared to standard-dose in MINOCA patients 3

Important Considerations and Pitfalls

Common Pitfalls

1. Misclassification: MINOCA is often misclassified, limiting proper disease management and treatment 1
2. Overlooking alternative diagnoses: Conditions that can mimic MINOCA include:
   • Myocarditis
   • Takotsubo syndrome
   • Hypertensive crisis
   • Tachyarrhythmias
   • Sepsis
   • Severe anemia
   • Cardiac contusion 1

Prognostic Considerations

• Although MINOCA has better prognosis than MI with obstructive CAD, patients still have lower survival rates than healthy individuals matched for age and sex 1
• Annual mortality rate is approximately 2% 4
• Prognosis depends on the underlying etiology 5

Follow-up Management

• Manage patients according to the identified underlying cause
• For MINOCA of unknown cause:
  • Consider secondary prevention medications for atherosclerotic disease
  • Regular follow-up to monitor for recurrent events
  • Consider standard-dose rather than intensified antiplatelet therapy 3

By following this systematic approach to diagnosis and management, clinicians can properly identify the underlying cause of MINOCA and implement appropriate treatment strategies to improve outcomes for these patients.