What is the role of streptokinase in treating acute pulmonary thromboembolism (PTE)?

Streptokinase in Acute Pulmonary Thromboembolism

Streptokinase should be reserved only for high-risk pulmonary thromboembolism (PTE) patients with hemodynamic instability, particularly those with hypotension, as it carries significant bleeding risks while showing limited mortality benefit in non-high-risk patients. 1

Role of Streptokinase in PTE Management

Indications

• High-risk PTE: Streptokinase is indicated primarily for patients with hemodynamic instability, particularly those with hypotension 1
• Contraindicated in patients with:
  • History of hemorrhagic stroke or stroke of unknown origin
  • Ischemic stroke in previous 6 months
  • Central nervous system neoplasm
  • Major trauma, surgery, or head injury in previous 3 weeks
  • Bleeding diathesis
  • Active bleeding 1

Dosing Regimen

The recommended dosing for streptokinase in PTE is:

• 250,000 IU as a loading dose over 30 minutes, followed by
• 100,000 IU/hour over 12-24 hours, or
• Accelerated regimen: 1.5 million IU over 2 hours 1

Efficacy and Mechanism of Action

Streptokinase rapidly resolves thromboembolic obstruction and improves hemodynamic parameters:

• Increases cardiac index by up to 80%
• Decreases pulmonary arterial pressure by approximately 40% 1
• Accelerates normalization of pulmonary artery pressure and pulmonary perfusion more rapidly than heparin alone 1

However, despite these physiological improvements, mortality benefit is primarily observed in high-risk patients with hemodynamic compromise rather than in all PTE patients 1, 2.

Comparison with Other Thrombolytics

• rtPA (Alteplase): Has largely replaced streptokinase as the preferred agent due to:
  • Shorter infusion time (2 hours vs. 12-24 hours)
  • Lower risk of hypotension and systemic symptoms (fever, chills)
  • Equal efficacy with fewer allergic reactions 1, 3
• Urokinase: Similar efficacy to streptokinase but less antigenic 1

Risk-Benefit Assessment

Benefits

• Rapid resolution of pulmonary emboli
• Improved pulmonary perfusion
• Reduced pulmonary hypertension
• Improved right ventricular function 1

Risks

• Major bleeding occurs in approximately 10% of high-risk patients 1
• Allergic reactions (streptokinase is highly antigenic)
• Hypotension and systemic symptoms 1

Clinical Approach Algorithm

1. Risk Stratification:

   • High-risk PTE: Hemodynamic instability with shock/hypotension
   • Intermediate-risk PTE: RV dysfunction and/or myocardial injury without hypotension
   • Low-risk PTE: No RV dysfunction or myocardial injury 1, 2

2. Treatment Decision:

   • High-risk PTE: Immediate thrombolysis (preferably rtPA over streptokinase if available) unless contraindicated 1, 2
   • Intermediate-risk PTE: Standard anticoagulation with rescue thrombolysis if clinical deterioration occurs 1
   • Low-risk PTE: Standard anticoagulation only 1, 2

3. If streptokinase is chosen:

   • Screen thoroughly for contraindications
   • Consider hydrocortisone administration to reduce allergic reactions
   • Monitor closely for bleeding complications
   • Be aware that streptokinase cannot be reused in subsequent episodes due to antibody formation 1

Important Caveats

• Streptokinase is highly antigenic and can only be used once due to antibody formation 1
• The risk of bleeding is higher in patients who have undergone surgery, obstetric delivery, or invasive procedures within the past 7 days 1
• Thrombolytic therapy appears to be effective for up to 14 days after symptom onset, but greatest benefit is observed when initiated within 48 hours 1
• In pregnancy, thrombolysis may be appropriate for massive PTE but not within six hours of delivery or in the early postpartum period due to bleeding risk 1

Current Practice Trends

The use of streptokinase for PTE has declined in favor of rtPA (alteplase) due to:

1. Shorter infusion time with rtPA
2. Lower risk of allergic reactions
3. Comparable efficacy with potentially fewer systemic side effects 1, 3

For patients not eligible for systemic thrombolysis, catheter-directed thrombolysis may be an alternative approach, potentially allowing for lower doses of thrombolytic agents 3.