Recommended Doses of Thrombolytics for Catheter-Directed Thrombolysis in Pulmonary Thromboembolism
For catheter-directed thrombolysis (CDL) of pulmonary embolism, alteplase is the preferred agent with a recommended dose of approximately 20-24 mg total (about one-fourth of the systemic dose), typically delivered at 1 mg/hour/catheter over 5-24 hours. 1
Alteplase (tPA) Dosing
Standard Approach
- Dose: 20-24 mg total (approximately one-fourth of systemic dose)
- Rate: 1 mg/hour/catheter
- Duration: 5-24 hours
- Administration: Through multi-sidehole infusion catheter directly into the pulmonary artery thrombus
Ultrasound-Assisted Thrombolysis (USAT)
- Dose: 10-24 mg total
- Rate: 1 mg/hour/catheter
- Duration: 5-12 hours
- Device: EKOSonic catheter system 1, 2
Recent evidence suggests that even very low-dose USAT with 10 mg alteplase administered over 5 hours (1 mg/hour/catheter) can effectively improve pulmonary hemodynamics with minimal bleeding risk in intermediate-high risk PE patients 2.
Alternative Thrombolytics
Urokinase
- Dose: 10,000 U/kg once daily for 7 days (intermittent low-dose regimen)
- Alternative regimen: Higher doses of 1,600-4,400 U/kg/hour for 12-24 hours have been used historically 3, 4
Streptokinase
- Dose: 1.5 million IU total
- Duration: 2 hours
- Note: Similar hemodynamic efficacy to alteplase at 2 hours but with slightly slower initial response 5
Technical Considerations
Catheter Selection
- For USAT: 5F EKOSonic catheter
- For standard CDL: 4F-5F catheters (Unifuse or Cragg-McNamara) 1
Anticoagulation During Procedure
- Unfractionated heparin: 70 IU/kg IV bolus, then titrate to maintain ACT >250 seconds
- Alternative: Bivalirudin 0.75 mg/kg IV bolus, then 1.75 mg/kg/h 1
Monitoring
- Continuous hemodynamic monitoring during procedure
- Assess for bleeding complications
- Monitor fibrinogen levels and platelet count
Efficacy and Safety Considerations
- CDL aims to achieve similar or improved effectiveness compared to systemic thrombolysis while decreasing major bleeding risk by delivering a significantly lower total dose 1
- The optimal dosing strategy is still being actively investigated, with recent studies showing efficacy with doses as low as 10 mg over 5 hours 2
- Alteplase stability during USAT decreases to approximately 90% of original concentration after 2 hours, 80% after 4 hours, and 70% after 6 hours 6
Patient Selection and Indications
CDL is most appropriate for:
- Patients with massive PE who have contraindications to systemic thrombolysis
- Patients with massive PE who remain unstable after receiving systemic thrombolysis
- Selected patients with submassive PE with evidence of adverse prognosis (worsening respiratory failure, severe RV dysfunction) 1
Cautions and Contraindications
- Only operators experienced with these techniques should perform catheter-based intervention
- Interventionalists must be comfortable managing cardiogenic shock, bradyarrhythmias, anticoagulation, and cardiac tamponade
- Invasive arterial access is recommended for patients with shock or hypotension 1
- CDL is not recommended for patients with low-risk PE or submassive PE with minor RV dysfunction and no clinical worsening 1
Remember that the optimal dosing strategy for catheter-directed thrombolysis in PE continues to evolve, with a trend toward lower doses to minimize bleeding risk while maintaining efficacy.