Does external ultrasound accelerate thrombolysis? Results from a rabbit model

Area of Science:

• Cardiovascular Research
• Biomedical Engineering
• Thrombosis and Hemostasis

Background:

• External ultrasound has shown potential in accelerating thrombolysis at low intensities.
• Previous studies suggest ultrasound can aid clot dissolution without direct lytic effects.
• This study investigates ultrasound's impact on thrombolysis and reocclusion in a rabbit model.

Purpose of the Study:

• To evaluate the effect of external ultrasound on thrombolysis in a rabbit femoral artery thrombosis model.
• To assess the impact of ultrasound on reocclusion rates when used with recombinant tissue-type plasminogen activator (rTPA).

Main Methods:

• A rabbit femoral artery thrombosis model was created with endothelial damage and stenosis.
• Recombinant tissue-type plasminogen activator (rTPA) was administered intravenously.
• Rabbits were divided into groups with and without continuous wave ultrasound (1 MHz, 6.3 W/cm²) and aspirin.
• Femoral artery flow was monitored for 2 hours to assess reflow and reocclusion.

Main Results:

• Ultrasound significantly shortened the time to initial reflow (21-33 minutes) compared to no ultrasound (46-74 minutes).
• However, ultrasound use was associated with worse overall femoral artery patency and increased reocclusion rates (P = .002).
• Reocclusion was observed in 5/5 and 2/4 rabbits with ultrasound, versus 0/8 and 0/5 without.

Conclusions:

• While ultrasound accelerates initial thrombolysis, it leads to more reocclusion in this rabbit model.
• Ultrasound-induced platelet activation may counteract its thrombolytic benefits.
• The findings suggest caution when using ultrasound adjunctively with rTPA for treating thrombosis.