When should thrombolysis be given in a patient with ST‑segment elevation myocardial infarction?

Thrombolysis in STEMI: Timing and Indications

Administer thrombolytic therapy immediately when primary PCI cannot be performed within 120 minutes of first medical contact in patients presenting within 12 hours of symptom onset with persistent ST-segment elevation and no contraindications. 1

Primary Decision Algorithm: PCI Timing Determines Thrombolysis

The fundamental decision point is straightforward:

• If primary PCI achievable within 90-120 minutes of first medical contact: Proceed directly to catheterization laboratory—fibrinolysis is NOT indicated 1
• If primary PCI will be delayed beyond 120 minutes: Initiate fibrinolytic therapy immediately, preferably in the pre-hospital setting 1, 2

This time-based algorithm reflects the reality that while primary PCI is the preferred reperfusion strategy, it cannot be delivered timely to all patients, particularly those in areas with long transfer delays 2, 3, 4

Essential Prerequisites Before Thrombolysis

Before administering thrombolytics, verify these mandatory criteria:

• Symptom duration ≤12 hours with persistent ST-segment elevation 1
• No contraindications to fibrinolytic therapy, including: 1, 5
  • Active internal bleeding 5
  • History of cerebrovascular accident 5
  • Intracranial or intraspinal surgery/trauma within 2 months 5
  • Intracranial neoplasm, arteriovenous malformation, or aneurysm 5
  • Known bleeding diathesis 5
  • Severe uncontrolled hypertension 5

Mandatory Adjunctive Therapy with Thrombolysis

When administering thrombolytics, you must simultaneously give:

• Aspirin (oral or IV if unable to swallow) immediately 1
• Clopidogrel (not prasugrel or ticagrelor initially) in addition to aspirin 1
• Anticoagulation until revascularization or up to 8 days of hospitalization 1

This triple therapy is non-negotiable and reduces the risk of re-occlusion that occurs because fibrinolysis activates platelets and promotes thrombin activity 6

Post-Thrombolysis Management: The Pharmaco-Invasive Strategy

All patients receiving thrombolysis require immediate transfer to a PCI-capable center regardless of apparent success 1. This pharmaco-invasive approach has been shown to be non-inferior to primary PCI in patients with long transfer delays (>60 minutes) 2

The timing of subsequent PCI follows this algorithm:

• Routine angiography and PCI between 2-24 hours after thrombolysis administration (Class I, Level A recommendation) 1, 7
• Rescue PCI immediately if <50% ST-segment resolution at 60-90 minutes, indicating failed thrombolysis 1

Early PCI within 24 hours after successful thrombolysis improves cardiovascular outcomes without significant increase in bleeding complications 7

Critical Situations Where Thrombolysis is NOT Indicated

Do not administer thrombolytics in these scenarios:

• Any patient who can receive primary PCI within 120 minutes 1
• Asymptomatic patients with occluded infarct-related artery >48 hours after STEMI onset (Class III, Level A) 1
• Patients with contraindications to fibrinolysis 1

Common Pitfall: Pre-Hospital Administration

The guidelines emphasize that fibrinolytic therapy should preferably be started in the pre-hospital setting when indicated 1, 2. This pre-hospital initiation is crucial for minimizing total ischemic time in patients who cannot access timely PCI, yet it remains underutilized in many systems 3