At what ECG (electrocardiogram) changes should I initiate antiplatelet and anticoagulant treatment?

ECG Changes Warranting Antiplatelet and Anticoagulant Therapy

Initiate dual antiplatelet therapy (aspirin plus a P2Y12 inhibitor) and anticoagulation immediately when the ECG shows ST-segment elevation or new left bundle branch block (LBBB), as these findings indicate acute myocardial infarction requiring urgent reperfusion therapy. 1

Acute Coronary Syndrome with ST-Segment Elevation (STEMI)

When you identify ST-segment elevation or presumed new LBBB on ECG:

• Aspirin: Administer immediately at 150-300 mg oral loading dose (or 75-250 mg IV if unable to take orally), followed by 75-100 mg daily maintenance 1
• P2Y12 Inhibitor: Give a potent agent before or at the time of PCI 1:
  • Ticagrelor 180 mg loading dose, then 90 mg twice daily (preferred option) 1
  • Prasugrel 60 mg loading dose, then 10 mg daily (if P2Y12-inhibitor naïve and proceeding to PCI) 1
  • Clopidogrel 600 mg loading dose, then 75 mg daily (only if prasugrel or ticagrelor unavailable or contraindicated) 1
• Anticoagulation: Start immediately with unfractionated heparin (UFH), enoxaparin, or bivalirudin during PCI 1

The combination of antiplatelet and anticoagulant therapy is essential because platelet-rich thrombus formation on ruptured plaque is the underlying pathophysiology 2, 3.

Non-ST-Elevation Acute Coronary Syndrome (NSTE-ACS)

When the ECG shows ST-segment depression, T-wave inversions, or dynamic ECG changes without ST-elevation:

• Aspirin: Same dosing as STEMI (150-300 mg loading, 75-100 mg daily) 1
• P2Y12 Inhibitor: Initiate as soon as diagnosis is established 1:
  • Ticagrelor 180 mg loading dose preferred for pre-treatment 1
  • Clopidogrel 600 mg loading dose if ticagrelor not available 1
  • Avoid prasugrel pre-treatment until coronary anatomy is known 1
• Anticoagulation: Select based on bleeding and ischemic risk 1:
  • UFH (recommended) 1
  • Enoxaparin (should be considered) 1
  • Fondaparinux (acceptable alternative) 1

Continue dual antiplatelet therapy for 12 months unless excessive bleeding risk exists (PRECISE-DAPT score ≥25), in which case consider stopping at 6 months 1.

Critical Timing Considerations

The ECG must be obtained within 5 minutes of initial assessment in any patient with acute ischemic chest pain 3. This rapid ECG interpretation determines whether immediate reperfusion therapy is needed.

For STEMI patients, if transfer to hospital exceeds 30 minutes and symptom onset is less than 12 hours, pre-hospital fibrinolysis should be undertaken alongside antiplatelet therapy 3.

Important Caveats and Pitfalls

Avoid these common errors:

• Do not give prasugrel to patients with prior stroke/TIA (increased cerebrovascular event risk: 6.5% vs 1.2% with clopidogrel) or those >75 years old or <60 kg body weight 4
• Do not pre-treat with prasugrel before knowing coronary anatomy in NSTE-ACS 1
• Do not use GP IIb/IIIa inhibitors routinely for pre-treatment when coronary anatomy is unknown 1
• Do not crossover between UFH and low-molecular-weight heparin 1

For patients already on warfarin who present with ACS: Do not initiate additional anticoagulation until INR <2.0, but start antiplatelet therapy immediately even if therapeutically anticoagulated, especially if PCI with stenting is anticipated 1.

Duration of Therapy

Standard duration is 12 months of dual antiplatelet therapy for all ACS patients 1, 4. However:

• High bleeding risk (PRECISE-DAPT ≥25): Consider stopping P2Y12 inhibitor at 6 months 1
• High ischemic risk with low bleeding risk: May continue DAPT beyond 12 months (ticagrelor 60 mg twice daily can be considered) 1
• Anticoagulation should be discontinued immediately after PCI procedure 1

The evidence strongly supports that this aggressive antithrombotic approach reduces mortality and morbidity in acute coronary syndromes, with the most robust data coming from large randomized trials showing consistent benefit across different presentations 1, 4.