Acceleration of Fibrinolysis by High-frequency Ultrasound: The Contribution of Acoustic Streaming and Temperature Rise

doi:10.1016/S0049-3848(00)00319-4

Thrombosis Research

Volume 100, Issue 4, 15 November 2000, Pages 333-340

https://doi.org/10.1016/S0049-3848(00)00319-4 Get rights and content

Abstract

High-frequency ultrasound has been shown to accelerate enzymatic fibrinolysis. One of the supposed mechanisms of this effect is the enhancement of mass transport by acoustic streaming, i.e., ultrasound-induced macroscopic flow around the clot. In this study, which is aimed at further elucidating the mechanisms of the acceleration of fibrinolysis by ultrasound, we investigated whether ultrasound would accelerate fibrinolysis if the flow around the thrombus is already present, as may occur in vivo. The effect of the ultrasound-induced temperature rise was also studied. In a model of a plasma clot submerged in plasma, containing tissue-type plasminogen activator, mild stirring of the outer plasma producing a shear rate of 40 seconds⁻¹ at the surface of the clot resulted in a two-fold acceleration of lysis. A similar effect was obtained with ultrasound (1 MHz, 2 W/cm²). Furthermore, if ultrasound was applied together with stirring, only 30% acceleration by ultrasound was documented, fully attributable to the concomitant temperature rise. In a model with tissue-type plasminogen activator incorporated throughout a plasma clot, the effect of ultrasound (two-fold shortening of lysis time) was fully attributable to the concomitant temperature rise of a few degrees. We concluded that the acceleration of enzymatic plasma clot lysis by high-frequency ultrasound in the models we used can be largely explained by a combination of the effects of heating and acoustic streaming, equivalent to mild stirring. The thermal effects can hardly be utilized in vivo due to the danger of tissue overheat. The therapeutic advantage of transcutaneous high-frequency ultrasound as an adjunct to thrombolytic therapy may appear limited to the situations where there is no flow in the direct environment of the thrombus.

Section snippets

Materials

Human fibrinogen (Kabi) was labeled with FITC (Sigma-Aldrich Chemie BV, Zwijndrecht, The Netherlands) as described elsewhere [22], resulting in a preparation with a molar fluorescein/protein ratio of 1.9. TPA (Actilyse) was supplied by Boehringer Ingelheim (Ingelheim, Germany).

Experimental Set-up

We used the experimental system which has been described earlier [16] with the difference that in the present study the tube containing a plasma clot was not rotating, but stationary. Briefly, the system consisted of a

Temperature Rise During the Ultrasound Exposure

Exposure of a tube containing a non-compacted plasma clot to ultrasound was accompanied by a considerable temperature rise inside the clot. Within a minute after the start of the insonification of the tube in the water bath, maintained at 37°C, the temperature in the central part of the clot increased from 37°C to a steady level of 43°C. Next to the wall of the plastic tube the temperature rise was greater, up to 46°C, indicating that the heat was generated mainly by the walls of the tube. In

Discussion

Heating and acoustic streaming are two potential mechanisms that can contribute to the acceleration of fibrinolysis by ultrasound. In this paper, we tried to elucidate which part of the effect of ultrasound can be attributed to these two mechanisms.

Not much is published about the effects of heating on fibrinolysis. However, all available data show that fibrinolysis is accelerated by an increase in temperature in the range of 25°C–40°C 21, 24, 25, 26. A temperature rise during ultrasonic

Acknowledgements

This study was supported by Grant 96.022 from the Netherlands Heart Foundation. We are grateful to Dr. C. Kluft for the critical reading of the manuscript.

References (31)

S. Atar et al.
Ultrasonic thrombolysisCatheter-delivered and transcutaneous applications
Eur J Ultrasound
(1999)
U. Rosenschein et al.
Study on the mechanism of ultrasound angioplasty from human thrombi and bovine aorta
Am J Cardiol
(1994)
W. Steffen et al.
High intensity, low frequency catheter-delivered ultrasound dissolution of occlusive coronary artery thrombian in vitro and in vivo study
J Am Coll Cardiol
(1994)
A. Blinc et al.
Characterisation of ultrasound-potentiated fibrinolysis in vitro
Blood
(1993)
A. Kashyap et al.
Acceleration of fibrinolysis by ultrasound in a rabbit ear model of small vessel injury
Thromb Res
(1994)
D. Harpaz et al.
Ultrasound enhancement of thrombolysis and reperfusion in vitro
J Am Coll Cardiol
(1993)
D. Harpaz et al.
Ultrasound accelerates urokinase-induced thrombolysis and reperfusion
Am Heart J
(1994)
C.W. Francis et al.
Ultrasound accelerates transport of recombinant tissue plasminogen activator into clots
Ultrasound Med Biol
(1995)
S.B. Olsson et al.
Enhancement of thrombolysis by ultrasound
Ultrasound Med Biol
(1994)
F. Siddiqi et al.
Binding of tissue-plasminogen activator to fibrineffect of ultrasound
Blood
(1998)

A.A. Higazi et al.

The effect of ultrasonic irradiation and temperature on fibrinolytic activity in vitro

Thromb Res

(1993)

D.V. Sakharov et al.

Rearrangements of the fibrin network and spatial distribution of fibrinolytic components during plasma clot lysis. Study with confocal microscopy

J Biol Chem

(1996)

M.A. Yenari et al.

Thrombolysis with tissue plasminogen activator (tPA) is temperature dependent

Thromb Res

(1995)

S.V. Pislaru et al.

The current role of thrombolytic therapy in the treatment of acute myocardial infarction

Fibrinolysis & Proteolysis

(1999)

H. Luo et al.

Enhancement of thrombolysis in vivo without skin and soft tissue damage by transcutaneous ultrasound

Thromb Res

(1998)

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Citation Excerpt :
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Original articleAcceleration of Fibrinolysis by High-frequency Ultrasound: The Contribution of Acoustic Streaming and Temperature Rise

Abstract

Section snippets

Materials

Experimental Set-up

Temperature Rise During the Ultrasound Exposure

Discussion

Acknowledgements

Eur J Ultrasound

Am J Cardiol

J Am Coll Cardiol

Blood

Thromb Res

J Am Coll Cardiol

Am Heart J

Ultrasound Med Biol

Ultrasound Med Biol

Blood

Thromb Res

J Biol Chem

Thromb Res

Fibrinolysis & Proteolysis

Thromb Res

Original article
Acceleration of Fibrinolysis by High-frequency Ultrasound: The Contribution of Acoustic Streaming and Temperature Rise