What is the management protocol for a patient presenting with myocardial infarction (MI)?

STEMI Management Protocol

For patients presenting with ST-elevation myocardial infarction (STEMI), immediate reperfusion therapy via primary PCI within 90-120 minutes of first medical contact is the definitive treatment, combined with dual antiplatelet therapy (aspirin plus potent P2Y12 inhibitor), anticoagulation, and morphine for pain control. 1, 2

Immediate Actions Upon First Medical Contact

Diagnostic Evaluation (Target: ≤10 minutes)

• Obtain 12-lead ECG within 10 minutes of first medical contact to identify ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block 1, 2
• Place patient on continuous cardiac monitoring with defibrillator capacity immediately 1
• Do not wait for cardiac biomarkers to initiate reperfusion therapy 3

Initial Pharmacotherapy (Administer Immediately)

• Aspirin 150-325 mg orally or IV (if unable to swallow) - give without delay even in hypotensive patients 1, 2, 3
• Potent P2Y12 inhibitor loading dose before or at time of PCI: prasugrel 60 mg or ticagrelor 180 mg (clopidogrel 300-600 mg only if prasugrel/ticagrelor unavailable or contraindicated) 1, 2, 4
• Morphine sulfate 4-8 mg IV with additional 2 mg doses at 5-15 minute intervals for pain control and anxiety reduction 5, 2, 3
• Oxygen only if SaO2 <90% - routine oxygen is not recommended 1

Reperfusion Strategy Selection

Primary PCI (Preferred Strategy)

Primary PCI is indicated for all STEMI patients with symptoms <12 hours duration when it can be performed within target times 1, 2

Timing Targets from First Medical Contact:

• ≤90 minutes if presenting to PCI-capable hospital 1
• ≤120 minutes if requiring transfer to PCI-capable center (≤60 minutes if early presenter with large area at risk) 1

Pre-PCI Anticoagulation:

• Unfractionated heparin: weight-adjusted IV bolus followed by infusion 1, 2, 3
• Alternatives: enoxaparin or bivalirudin 1
• Do not use fondaparinux for primary PCI 3

Logistics:

• Patients transferred for primary PCI should bypass emergency department and go directly to catheterization laboratory 1
• PCI-capable centers must deliver 24/7 service 1
• Prehospital activation of catheterization laboratory team reduces door-to-balloon time by approximately 18-20 minutes 6

Fibrinolytic Therapy (When Primary PCI Cannot Be Performed Timely)

If primary PCI cannot be performed within 120 minutes of STEMI diagnosis, initiate fibrinolytic therapy within 12 hours of symptom onset 1, 2

Target: ≤30 minutes from first medical contact to fibrinolysis 1

Fibrinolytic Regimen:

• Fibrin-specific agent (tenecteplase, alteplase, or reteplase) preferably in pre-hospital setting 2, 3
• Enoxaparin as anticoagulant (unfractionated heparin as alternative) 1
• Clopidogrel loading dose (prasugrel/ticagrelor not studied with fibrinolysis) 1

Post-Fibrinolysis Management:

• Transfer all patients to PCI-capable center immediately after fibrinolysis administration 2
• Angiography 3-24 hours after successful fibrinolysis 1
• Emergency angiography and rescue PCI immediately if:
  • Heart failure or cardiogenic shock develops 2
  • Failed fibrinolysis (persistent ST-elevation or ongoing symptoms) 1

Special Timing Considerations

Late Presenters (>12 hours from symptom onset)

• Reperfusion therapy (preferably primary PCI) is indicated if evidence of ongoing ischemia exists, regardless of time from symptom onset 1
• Primary PCI may be considered in stable patients presenting 12-24 hours after symptom onset 1
• Routine PCI of totally occluded artery >48 hours after symptom onset in stable, asymptomatic patients is NOT indicated 1

The Occluded Artery Trial (n=2166) demonstrated no clinical benefit from routine PCI in stable patients with persistent occlusion 3-28 days post-MI 1

STEMI Without Chest Pain

• Treat ST-elevation without chest pain as true STEMI requiring immediate reperfusion therapy - absence of chest pain does not change urgency or management approach 2
• Do not delay reperfusion based on atypical symptoms 2

Post-Reperfusion Management

Monitoring (Minimum 24 Hours)

• Continuous cardiac monitoring for arrhythmias and hemodynamic instability 5, 2
• Monitor for recurrent ischemia (ECG changes, symptom recurrence) 2

Long-Term Antithrombotic Therapy

• Dual antiplatelet therapy (DAPT) for 12 months: aspirin 75-100 mg daily plus ticagrelor 90 mg twice daily or prasugrel 10 mg daily (5 mg if <60 kg) 1, 2, 4
• Proton pump inhibitor in combination with DAPT for patients at high gastrointestinal bleeding risk 2

Additional Guideline-Directed Medical Therapy

• Beta-blocker, ACE inhibitor, and statin per standard post-MI protocols 2

Special Populations and Pitfalls

Hypotensive Patients

• Do not withhold aspirin or P2Y12 inhibitor 3
• Assess volume status; cautious IV fluid administration if volume-depleted while monitoring for heart failure 3
• Emergency cardiac catheterization with primary PCI is definitive treatment 3
• Be cautious with morphine dosing due to potential for worsening hypotension 3

Resuscitated Cardiac Arrest

• Primary PCI strategy is recommended in patients with resuscitated cardiac arrest and ECG consistent with STEMI 1
• Targeted temperature management (32-36°C for ≥24 hours) is indicated in patients remaining unresponsive after resuscitation 1
• Do not delay primary PCI for cooling - can be started in parallel in catheterization laboratory 1

Elderly Patients (≥75 years)

• Prasugrel generally not recommended except in high-risk patients (diabetes or prior MI) 4
• Consider dose adjustments for renal insufficiency 1

Critical Pitfalls to Avoid

• Do not give NSAIDs for pain relief - use morphine instead due to prothrombotic effects of NSAIDs 3
• Do not delay reperfusion waiting for cardiac biomarkers 3
• Do not routinely administer oxygen unless SaO2 <90% 1
• Do not perform routine PCI of occluded artery >48 hours post-STEMI in stable, asymptomatic patients 1
• If possible, manage bleeding without discontinuing antiplatelet therapy - stopping increases risk of subsequent cardiovascular events 4