What is the recommended thrombolysis protocol for patients with Acute Coronary Syndrome (ACS), specifically ST-segment elevation myocardial infarction (STEMI), who are not candidates for primary Percutaneous Coronary Intervention (PCI)?

Thrombolysis Protocol for STEMI Patients Not Eligible for Primary PCI

For STEMI patients who cannot receive primary PCI within 120 minutes of first medical contact, fibrinolytic therapy should be initiated immediately (within 10 minutes of STEMI diagnosis) using a fibrin-specific agent such as tenecteplase, alteplase, or reteplase. 1, 2

Patient Selection and Timing

• Thrombolysis is indicated for patients with:
  • STEMI presenting within 12 hours of symptom onset 1
  • When primary PCI cannot be performed in a timely manner (>120 minutes from first medical contact) 1, 2
  • Greatest benefit occurs when administered within the first 3 hours (51% mortality reduction within first hour, decreasing to 20% between 3-6 hours) 2

Pre-Thrombolysis Assessment

• Verify absence of contraindications:
  • Active internal bleeding
  • History of cerebrovascular accident
  • Intracranial/intraspinal surgery or trauma within 2 months
  • Intracranial neoplasm, arteriovenous malformation, or aneurysm
  • Known bleeding diathesis
  • Severe uncontrolled hypertension 3

Recommended Fibrinolytic Regimen

Medication Selection

• Preferred agents: Fibrin-specific agents 1, 2
  • Tenecteplase (TNKase): Single IV bolus over 5 seconds, weight-adjusted dosing 3
  • Alteplase: Accelerated dose protocol
  • Reteplase: Double bolus administration

Adjunctive Therapy

1. Antiplatelet therapy:

   • Aspirin: 162-325 mg (non-enteric coated, chewed) immediately 2
   • Clopidogrel: 300 mg loading dose (75 mg daily for patients ≥75 years) 1

2. Anticoagulation (continue until revascularization or hospital discharge up to 8 days):

   • Enoxaparin: Preferred over UFH - 30 mg IV bolus followed by 1 mg/kg SC every 12 hours 1
   • OR Unfractionated heparin: 60 U/kg IV bolus (maximum 4,000 U) followed by infusion of 12 U/kg/hour (maximum 1,000 U/hour) 1

Post-Thrombolysis Management

Immediate Transfer Strategy

• All patients should be transferred to a PCI-capable center immediately after fibrinolysis 1
• Angiography and PCI of the infarct-related artery is recommended between 2-24 hours after successful fibrinolysis 1

Rescue PCI Indications

• Failed fibrinolysis (<50% ST-segment resolution at 60-90 minutes)
• Hemodynamic or electrical instability
• Worsening ischemia 1

Emergency Angiography Indications

• Heart failure/cardiogenic shock
• Recurrent ischemia
• Evidence of reocclusion after initially successful fibrinolysis 1

Monitoring and Complications Management

• Continuous ECG monitoring with defibrillator capacity 1
• Monitor for bleeding complications (occurs in 4-13% of patients) 2
• Have anti-arrhythmic therapy available for bradycardia and/or ventricular irritability 3
• Monitor for hypersensitivity reactions during and for several hours after infusion 3
• Avoid intramuscular injections and nonessential handling of the patient 3

Special Considerations

• Elderly patients (≥75 years) may require dose adjustment of thrombolytics and antiplatelet agents 4
• Patients with renal insufficiency require dose adjustment of anticoagulants 1
• For patients with cardiogenic shock, immediate transfer for PCI is preferred regardless of time delay from MI onset 2

Clinical Pitfalls to Avoid

1. Delayed administration: Every effort must be made to minimize time delays; efficacy decreases significantly with time 1, 2
2. Overlooking contraindications: Carefully screen for absolute and relative contraindications to minimize bleeding risk 3
3. Inadequate anticoagulation: Ensure proper dosing and duration of anticoagulation therapy 1
4. Failure to transfer: All patients should be transferred to a PCI-capable center after fibrinolysis for potential rescue or routine PCI 1
5. Missing reperfusion failure: Monitor for signs of failed fibrinolysis and be prepared for rescue PCI 1

This protocol emphasizes the importance of rapid assessment, immediate thrombolysis when PCI is not timely available, and subsequent transfer to a PCI-capable facility to optimize outcomes for STEMI patients.