What is the management paradigm for an occlusion myocardial infarction (MI)?

Management Paradigm for Occlusion Myocardial Infarction

Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for patients with occlusion myocardial infarction presenting within 12 hours of symptom onset, ideally performed within 90 minutes of first medical contact. 1

Initial Assessment and Management

• Obtain 12-lead ECG within 10 minutes of presentation
• Administer aspirin 162-325 mg (chewed) immediately
• Establish IV access and monitor oxygen saturation (provide oxygen only if saturation <90%)
• Place on cardiac monitor with emergency resuscitation equipment nearby
• Perform early risk stratification using clinical markers (age, heart rate, blood pressure, Killip class, infarct location, previous MI, renal function) 1

Reperfusion Strategy Decision Algorithm

Time-Based Approach:

1. Early presenters (<3 hours from symptom onset):

   • Primary PCI is preferred if PCI-capable facility is available within 120 minutes
   • If PCI delay >120 minutes, immediate fibrinolysis is indicated 1

2. Intermediate presenters (3-12 hours from symptom onset):

   • Primary PCI strongly preferred
   • The later the presentation, the more consideration should be given to primary PCI over fibrinolysis 1

3. Late presenters (12-48 hours from symptom onset):

   • Routine primary PCI strategy (urgent angiography with subsequent PCI if indicated) should be considered 1

4. Very late presenters (>48 hours from symptom onset):

   • Angiography should be performed
   • Routine PCI of totally occluded infarct-related artery is NOT recommended 1, 2

Clinical Presentation Override:

• Regardless of time from symptom onset, primary PCI is indicated for patients with:
  • Ongoing symptoms suggestive of ischemia
  • Hemodynamic instability
  • Life-threatening arrhythmias 1

Primary PCI Protocol

• Administer loading dose of potent P2Y12 inhibitor:
  • Prasugrel 60 mg (preferred if no history of stroke/TIA and age <75) 3
  • Ticagrelor 180 mg (alternative)
  • Clopidogrel 600 mg (if prasugrel/ticagrelor unavailable or contraindicated) 1
• Administer anticoagulation with unfractionated heparin (70-100 U/kg IV bolus)
• Use radial access when possible to reduce bleeding risk 1
• Consider bivalirudin as alternative anticoagulant for patients at high bleeding risk 1

Fibrinolysis Protocol (if PCI not available within appropriate timeframe)

• Administer fibrin-specific agent within 30 minutes of first medical contact:
  • Tenecteplase, alteplase, or reteplase 1
• Administer anticoagulation:
  • Enoxaparin IV followed by SC (preferred) or
  • Unfractionated heparin as weight-adjusted IV bolus followed by infusion 1
• Transfer to PCI-capable center immediately after fibrinolysis 1
• Perform emergency angiography if:
  • Fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes)
  • Hemodynamic or electrical instability occurs
  • Ischemia worsens 1
• If fibrinolysis is successful, perform angiography between 2-24 hours later 1

Management of Cardiogenic Shock

• Immediate transfer to PCI-capable hospital for coronary angiography is recommended for patients who develop cardiogenic shock within 36 hours of MI 1
• Primary PCI is strongly recommended for patients <75 years old with shock 1
• For selected patients ≥75 years with good prior functional status, primary PCI is reasonable 1

Post-Reperfusion Care

• Perform echocardiography to assess LV and RV function and detect complications 1
• Initiate evidence-based medications:
  • DAPT (aspirin plus P2Y12 inhibitor) for 12 months 1
  • ACE inhibitors within 24 hours (especially for anterior MI, heart failure, or LVEF <40%) 1
  • Beta-blockers within 24 hours if no contraindications 1
  • High-intensity statin therapy 1
  • Consider proton pump inhibitor for patients at high risk of GI bleeding 1

Special Considerations

• Renal dysfunction: Present in 30-40% of ACS patients and associated with worse outcomes

  • Ensure proper hydration during and after PCI
  • Limit contrast agent dose
  • Use low-osmolality contrast agents 1

• Diabetes: More likely to present with atypical symptoms and have diffuse disease

  • More potent P2Y12 inhibitors (prasugrel or ticagrelor) show greater benefit 1
  • Monitor glycemic status on admission and frequently thereafter 1

Long-term Management

• Cardiac rehabilitation program participation 1
• Smoking cessation counseling and support 1
• Regular follow-up to monitor medication adherence and clinical status
• Consider implantable cardioverter-defibrillator evaluation if sustained ventricular arrhythmias occur >48 hours post-STEMI or if LVEF remains significantly reduced 4

Common Pitfalls to Avoid

• Delaying reperfusion decision-making
• Failing to recognize STEMI equivalents (posterior MI, new LBBB with clinical symptoms)
• Overlooking high-risk features requiring immediate intervention regardless of time from symptom onset
• Routine PCI of totally occluded artery >48 hours after symptom onset in asymptomatic patients 1, 2
• Premature discontinuation of DAPT, which increases risk of stent thrombosis 3