What is the immediate emergency management for a patient presenting with an acute myocardial infarction (ST‑segment elevation or high‑risk non‑ST‑segment elevation)?

Immediate Emergency Management of Acute Myocardial Infarction

For patients presenting with acute STEMI, immediately obtain a 12-lead ECG within 10 minutes of first medical contact, initiate dual antiplatelet therapy with aspirin plus a potent P2Y12 inhibitor (prasugrel or ticagrelor), and proceed directly to primary PCI within 90-120 minutes—or initiate fibrinolysis within 30 minutes if PCI cannot be achieved within 120 minutes of diagnosis. 1

Initial Diagnostic Actions

ECG Acquisition and Monitoring

• Obtain a 12-lead ECG within 10 minutes of first medical contact and interpret immediately for ST-segment elevation or equivalent patterns 1
• Initiate continuous ECG monitoring with defibrillator capacity immediately for all suspected STEMI patients 1
• Recognize STEMI equivalents including new bundle branch block, ventricular pacing, hyperacute T-waves, isolated ST-depression in anterior leads, or universal ST-depression with ST-elevation in aVR 1

Symptom Management

• Avoid routine oxygen unless oxygen saturation is <90% 1
• Administer morphine sulfate 4-8 mg IV for pain control and anxiety reduction, with additional 2 mg doses at 5-15 minute intervals as needed 2, 3
• Never administer nitrates if the patient has taken phosphodiesterase-5 inhibitors (e.g., tadalafil) within 48 hours due to risk of fatal hypotension 2

Reperfusion Strategy Selection

Time-Based Algorithm

The reperfusion strategy depends on the anticipated time from STEMI diagnosis to PCI-mediated reperfusion 1:

If PCI can be performed ≤120 minutes from diagnosis:

• Proceed with primary PCI strategy 1
• Target door-to-balloon time ≤90 minutes (≤60 minutes if presenting within 120 minutes of symptom onset or directly to PCI-capable hospital) 1
• Transfer patient directly to catheterization laboratory, bypassing the emergency department 1

If PCI cannot be performed within 120 minutes:

• Initiate fibrinolytic therapy immediately within 10 minutes of STEMI diagnosis, preferably in the pre-hospital setting 1
• Target door-to-needle time ≤30 minutes 1

Reperfusion Indication

• Reperfusion therapy is mandatory for all patients with ischemic symptoms <12 hours duration and persistent ST-segment elevation 1
• Consider reperfusion even beyond 12 hours if there is clinical or electrocardiographic evidence of ongoing ischemia 1

Antithrombotic Therapy

For Primary PCI Strategy

• Aspirin (oral or IV if unable to swallow) loading dose immediately 1
• Potent P2Y12 inhibitor: prasugrel or ticagrelor preferred over clopidogrel, administered before or at time of PCI 1, 2
• Unfractionated heparin as weight-adjusted IV bolus followed by infusion (enoxaparin or bivalirudin are alternatives) 1, 2
• Avoid fondaparinux for primary PCI 1

For Fibrinolytic Strategy

• Aspirin (oral or IV) loading dose 1
• Clopidogrel in addition to aspirin 1
• Fibrin-specific agent: tenecteplase, alteplase, or reteplase 1
• Enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) 1, 2
• Mandatory transfer to PCI-capable center immediately after fibrinolysis 1

Post-Fibrinolysis Management

Rescue PCI Indications

• Perform rescue PCI immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) 1
• Proceed to emergency angiography and PCI for hemodynamic instability, electrical instability, or worsening ischemia at any time 1

Routine Angiography After Successful Fibrinolysis

• Perform angiography and PCI of infarct-related artery between 2-24 hours after successful fibrinolysis 1, 2
• Emergency angiography is indicated for heart failure or shock 1, 2

Transport and System Considerations

Pre-Hospital Triage

• Emergency medical services should transport patients directly to 24/7 high-volume PCI centers, bypassing non-PCI-capable hospitals when feasible 1, 4
• EMS transport reduces symptom-onset-to-arrival time (median 89 vs 120 minutes for self-transport) and door-to-reperfusion time significantly 5
• Alert the PCI center immediately after reperfusion strategy selection 1

Special Circumstances

• Post-cardiac arrest with ST-elevation: proceed with primary PCI strategy 1
• Post-cardiac arrest without ST-elevation but high suspicion of ischemia: perform urgent angiography within 2 hours after excluding non-coronary causes 1
• Consider neurological prognosis factors when deciding on urgent coronary angiography post-arrest 1

Technical Aspects of Primary PCI

• Radial access is the standard approach 1
• Drug-eluting stent implantation is routine 1
• Routine thrombus aspiration is contraindicated 1
• Deferred stenting is contraindicated 1

Critical Pitfalls to Avoid

• Do not delay reperfusion for routine laboratory results or imaging—every minute increases myocardial necrosis 2
• Do not administer nitrates without confirming no recent phosphodiesterase-5 inhibitor use 2
• Do not use benzodiazepines for anxiety—they can cause respiratory depression, hypotension, and obscure clinical signs of complications 3
• Do not send patients to the emergency department if transferring for primary PCI—go directly to the catheterization laboratory 1
• Do not perform routine PCI of occluded infarct-related artery >48 hours after STEMI onset in asymptomatic patients 1

Monitoring and Early Care

• Monitor patients for at least 24 hours after reperfusion therapy 1
• Perform routine echocardiography during hospital stay to assess LV/RV function, detect mechanical complications, and exclude LV thrombus 1, 2
• Initiate dual antiplatelet therapy for 12 months (aspirin plus prasugrel/ticagrelor) unless excessive bleeding risk 1