Acute Myocardial Infarction: Immediate Management and Reperfusion Strategy
For adults presenting with STEMI, immediately administer aspirin 150–325 mg orally (or 250–500 mg IV if unable to swallow) and pursue primary percutaneous coronary intervention (PCI) within 90–120 minutes of first medical contact; if this timeline cannot be met, initiate fibrinolytic therapy within 10–30 minutes of diagnosis. 1, 2
Time-Critical Initial Actions (First 10 Minutes)
Obtain and interpret a 12-lead ECG within 10 minutes of first medical contact to confirm ST-segment elevation ≥0.1 mV in two contiguous leads (or ≥0.2 mV in men >40 years or ≥0.25 mV in men <40 years in leads V2–V3, ≥0.15 mV in women in V2–V3). 1, 2
Initiate continuous ECG monitoring with defibrillator capacity immediately to detect life-threatening arrhythmias. 1, 2
Administer aspirin 150–325 mg orally or 250–500 mg IV (if unable to swallow) at first medical contact—this is non-negotiable regardless of bleeding risk because the mortality benefit in STEMI supersedes bleeding concerns. 1, 2
Avoid routine supplemental oxygen unless peripheral oxygen saturation falls below 90%. 2
Reperfusion Strategy Selection: The 120-Minute Rule
The choice between primary PCI and fibrinolysis hinges on a single critical threshold:
Primary PCI Pathway (Preferred)
Primary PCI is the preferred reperfusion strategy when first-medical-contact-to-device time can be achieved within 120 minutes. 1, 2
For patients presenting directly to a PCI-capable hospital, the target is ≤90 minutes from first medical contact to balloon inflation. 1, 2
For patients at non-PCI-capable facilities, immediate transfer is indicated if the anticipated first-medical-contact-to-device time is ≤120 minutes (maintain door-in-door-out time ≤30 minutes). 1, 2
Transfer patients directly to the catheterization laboratory, bypassing the emergency department and coronary care unit entirely—PCI-capable centers must provide 24/7 service without delay, even at 2 AM. 1, 2
Before or at the time of PCI, administer:
- A potent P2Y12 inhibitor: prasugrel 60 mg loading dose OR ticagrelor 180 mg loading dose (use clopidogrel only if these are unavailable). 1, 2
- Unfractionated heparin 100 U/kg IV bolus (reduce to 60 U/kg if GPIIb/IIIa inhibitors are used); enoxaparin or bivalirudin are acceptable alternatives, but fondaparinux is contraindicated for primary PCI. 1, 2
Technical standards during PCI:
- Use routine radial arterial access to minimize bleeding. 2
- Implant drug-eluting stents as the default device. 2
- Routine thrombus aspiration and deferred stenting are contraindicated. 2
Fibrinolytic Pathway (When PCI Delay >120 Minutes)
If primary PCI cannot be performed within 120 minutes, initiate fibrinolytic therapy within 10–30 minutes of diagnosis, preferably in the pre-hospital setting (e.g., ambulance). 1, 3
Fibrinolytic regimen:
- Fibrin-specific agent: tenecteplase (preferred for single-bolus administration), alteplase, or reteplase. 1, 3, 4
- Clopidogrel 300–600 mg loading dose immediately—clopidogrel is the only P2Y12 inhibitor recommended with fibrinolysis; do NOT use prasugrel or ticagrelor initially. 3, 4
- Enoxaparin (IV bolus followed by subcutaneous dosing) is preferred over unfractionated heparin; continue anticoagulation until revascularization or for the duration of hospital stay (up to 8 days). 1, 3, 4
Post-fibrinolysis management:
- Transfer all patients to a PCI-capable center immediately after fibrinolysis—do not wait to assess reperfusion success. 3, 4
- Perform routine angiography 2–24 hours after successful fibrinolysis (defined as ≥50% ST-segment resolution at 60–90 minutes, hemodynamic stability, symptom relief). 1, 3, 4
- Perform emergency (immediate) angiography for failed fibrinolysis (<50% ST-segment resolution), cardiogenic shock, hemodynamic/electrical instability, or recurrent ischemia. 3, 4
- At the time of angiography/PCI, switch from clopidogrel to prasugrel or ticagrelor and continue dual antiplatelet therapy for 12 months. 3, 4
Special ECG Patterns Requiring Urgent Reperfusion
Several STEMI-equivalent patterns mandate the same urgent reperfusion approach despite lacking classic ST-elevation:
New or presumed new left bundle branch block (LBBB) with ongoing ischemic symptoms—look for concordant ST-elevation (in leads with positive QRS deflections) as the best indicator of acute occlusion. 1
Isolated ST-depression in leads V1–V3 with positive terminal T-waves (posterior STEMI)—confirm with ST-elevation ≥0.1 mV in leads V7–V9. 1, 2
ST-elevation in aVR with diffuse ST-depression (suggests left main or multivessel disease). 2
Hyperacute T-waves that may precede ST-elevation in very early presenters—repeat the ECG or monitor ST-segments continuously. 1
For all these patterns, pursue emergency coronary angiography with a view to primary PCI even without diagnostic ST-elevation, because acute coronary occlusion may be present. 1, 2
Absolute Indications for Primary PCI (Regardless of Time Delay)
The following scenarios mandate primary PCI irrespective of the 120-minute threshold:
Cardiogenic shock or acute severe heart failure at any time after symptom onset. 1, 2
Contraindications to fibrinolytic therapy (active bleeding, recent stroke, terminal illness, etc.). 1, 2
Failed fibrinolysis (persistent symptoms or <50% ST-segment resolution at 60–90 minutes). 3, 4
Resuscitated cardiac arrest with ST-elevation on post-resuscitation ECG—perform immediate primary PCI. 2
Late Presentation (>12 Hours from Symptom Onset)
Reperfusion therapy (preferably primary PCI) is indicated if there is evidence of ongoing ischemia, even if symptoms may have started >12 hours beforehand or if pain and ECG changes have been stuttering. 1
Primary PCI may be considered in stable patients presenting 12–24 hours after symptom onset. 1
Routine PCI of a totally occluded artery >24 hours after symptom onset in stable patients without signs of ischemia is not recommended (based on the Occluded Artery Trial showing no clinical benefit). 1
In-Hospital Pharmacotherapy
Continue dual antiplatelet therapy (aspirin 75–100 mg daily plus prasugrel 10 mg daily or ticagrelor 90 mg twice daily) for 12 months after PCI unless contraindicated by high bleeding risk. 2
Additional evidence-based medications:
- Beta-blockers should be started orally in patients with heart failure and/or left ventricular ejection fraction <40% unless contraindicated. 2
- ACE inhibitors should be initiated within 24 hours in patients with heart failure, left ventricular systolic dysfunction, diabetes, or anterior infarction. 2
- High-intensity statin therapy should be initiated as early as possible. 2
Routine echocardiography should be performed during hospitalization to assess LV and RV function, detect mechanical complications, and exclude LV thrombus. 2
Critical Pitfalls to Avoid
Do not postpone PCI to "stabilize" other conditions (e.g., active GI bleeding)—the mortality risk from untreated STEMI exceeds that from procedural bleeding, and primary PCI is the only option when fibrinolysis is contraindicated. 2
Do not delay fibrinolysis to assess whether primary PCI might become available—if the 120-minute threshold will be exceeded, administer fibrinolysis within 10–30 minutes of diagnosis. 1, 3, 4
Do not use prasugrel or ticagrelor as the initial P2Y12 inhibitor with fibrinolytic therapy—clopidogrel is specifically indicated in this setting; switch to prasugrel or ticagrelor only at the time of subsequent PCI. 3, 4
Do not delay transfer to a PCI-capable center after fibrinolysis to assess reperfusion success—all patients require angiography regardless of clinical response. 3, 4
Do not miss the 2–24 hour window for routine angiography after successful fibrinolysis—adherence to this timeline improves outcomes. 3, 4
Do not withhold aspirin or P2Y12 inhibitors because of bleeding concerns—the immediate threat of stent thrombosis is greater than manageable bleeding complications. 2