Management of Significant ST Elevation in Chest Leads
Immediately activate the STEMI protocol and pursue primary percutaneous coronary intervention (PCI) within 90-120 minutes of first medical contact, or initiate fibrinolytic therapy within 10 minutes if PCI cannot be achieved within 120 minutes of diagnosis. 1, 2
Immediate Actions at First Medical Contact
- Obtain and interpret a 12-lead ECG within 10 minutes of patient presentation to confirm ST elevation myocardial infarction (STEMI) 1, 2
- Initiate continuous cardiac monitoring immediately to detect life-threatening arrhythmias and allow prompt defibrillation 1, 2
- Administer aspirin 150-325 mg (oral or IV if unable to swallow) as soon as possible 1, 2
- Give morphine 4-8 mg IV with additional 2 mg doses at 5-minute intervals for pain relief, as pain causes sympathetic activation that increases cardiac workload 1, 2
- Provide oxygen only if SaO₂ <90%—routine oxygen is not recommended 2
ECG Diagnostic Criteria for STEMI
ST elevation is diagnostic when measured at the J-point in at least two contiguous leads with the following thresholds 1:
- ≥2.5 mm in men <40 years in leads V2-V3
- ≥2 mm in men ≥40 years in leads V2-V3
- ≥1.5 mm in women in leads V2-V3
- ≥1 mm in all other leads (excluding left ventricular hypertrophy or left bundle branch block)
Record additional leads V7-V9 for suspected posterior MI (indicated by ST depression in V1-V3 with positive terminal T-waves), and record V3R-V4R for inferior MI to identify right ventricular infarction 1
Common Pitfall: Equivocal or Non-Diagnostic ECGs
If the initial ECG is equivocal, repeat ECG recordings immediately and compare with previous records 1. Some patients with acute coronary occlusion (particularly circumflex territory) may not show classic ST elevation—suspicion of ongoing ischemia warrants primary PCI even without diagnostic ST elevation 1.
Reperfusion Strategy Decision Algorithm
Primary PCI (Preferred Strategy)
Primary PCI is the definitive reperfusion strategy when it can be performed within 90-120 minutes of first medical contact 1, 2:
- Administer a potent P2Y₁₂ inhibitor (prasugrel or ticagrelor preferred over clopidogrel) before or at the time of PCI 1, 2
- Give weight-adjusted unfractionated heparin as IV bolus followed by infusion 1, 2
- Transport immediately to PCI-capable center if not already at one 1
Fibrinolytic Therapy (When PCI Cannot Be Achieved in Time)
If primary PCI cannot be performed within 120 minutes of STEMI diagnosis, initiate fibrinolytic therapy immediately—preferably in the pre-hospital setting within 10 minutes 1, 3, 2:
Fibrinolytic Agent Selection
- Use a fibrin-specific agent: tenecteplase (TNK-tPA) is preferred as it is single-bolus, weight-adjusted, and equivalent to alteplase with fewer non-cerebral bleeds 1, 3
- Reduce tenecteplase dose by 50% in patients ≥75 years to minimize stroke risk 3
Adjunctive Therapy with Fibrinolysis
- Aspirin 150-325 mg (already given) 1, 3
- Clopidogrel loading dose in addition to aspirin 1, 3
- Anticoagulation with enoxaparin or unfractionated heparin until revascularization or up to 8 days 3
Post-Fibrinolysis Management (Pharmacoinvasive Strategy)
All patients receiving fibrinolysis must be transferred immediately to a PCI-capable center 1, 3, 2. At 60-90 minutes after fibrinolysis, assess reperfusion success by measuring ST-segment resolution in the lead with greatest initial ST elevation 1, 3:
- <50% ST resolution = failed fibrinolysis → perform rescue PCI immediately 1, 3
- ≥50% ST resolution = successful fibrinolysis → perform routine angiography and PCI between 2-24 hours (not immediate unless complications develop) 1, 3, 4
Emergency angiography is indicated immediately if: heart failure, cardiogenic shock, hemodynamic instability, electrical instability, recurrent ischemia, or evidence of reocclusion after initial successful fibrinolysis 1, 3, 2
Critical Timing Consideration
For patients presenting within 3 hours of symptom onset, both fibrinolysis and long-distance transport for PCI have similar mortality outcomes 4. For patients presenting >3 hours after symptom onset, transport for primary PCI significantly reduces mortality compared to fibrinolysis (6% vs 15.3%, P<0.02) 4.
Long-Term Antithrombotic Management
- Dual antiplatelet therapy (DAPT) with aspirin 75-100 mg plus ticagrelor or prasugrel (or clopidogrel if unavailable/contraindicated) for 12 months 1, 2
- Add a proton pump inhibitor for patients at high risk of gastrointestinal bleeding 2
- Avoid omeprazole or esomeprazole with clopidogrel as they significantly reduce its antiplatelet activity 5
Additional Monitoring and Risk Stratification
- Continue ECG monitoring for at least 24 hours or longer if high-risk features present (heart failure, shock, serious arrhythmias) 1
- Perform echocardiography during hospital stay to assess ventricular function, detect mechanical complications, and exclude left ventricular thrombus 1, 6
- Monitor ST-segment recovery during the first hours, as this provides important prognostic information 1
Critical Pitfalls to Avoid
Never delay reperfusion therapy waiting for cardiac biomarkers—treatment decisions are based on clinical presentation and ECG findings 1, 3. Do not routinely combine fibrinolysis with planned immediate PCI, as this increases mortality and adverse outcomes 2. Avoid intramuscular injections (use IV route for all medications) 1.