Thrombolytic effects of 120-kHz and 1-MHz ultrasound and tissue plasminogen activator on porcine whole blood clots

Abstract

Stroke is the third leading cause of death and the leading cause of disability in the United States. For patients with ischemic stroke, the thrombolytic drug tissue plasminogen activator (tPA) is the only FDA-approved treatment. To aid in the development of a stroke therapy, the synergistic thrombolytic effect of tissue plasminogen activator (t-PA) and ultrasound was assessed in vitro in a porcine clot model. Whole blood clots were prepared from fresh porcine blood by aliquoting 1.5 ml into 8-mm-i.d. glass tubes, immersing the tubes in a 37<th>°C water bath for 3 h and storing the clots at 5<th>°C for at least 3 days prior to use in comparative ultrasound and t-PA studies, which ensured complete clot retraction. The 120-kHz or 1-MHz ultrasound peak-to-peak pressure amplitude used for exposures was 0.35, 0.70, or 1.00 MPa. The range of duty cycles varied from 10% to 100% (continuous wave) and the pulse repetition frequency was 1.7 kHz. Clot mass loss was measured as a function of t-PA concentration (without ultrasound) from 0.25 to 8.5 times the human clinical dose. The mass loss increased monotonically as a function of [t-PA] and saturated at 4 times the clinical dose. The degree of the ultrasound enhancement of t-PA was also explored at 120 kHz and 1 MHz. With ultrasound exposure, clot mass loss increased by as much as 250% over sham (t-PA alone). A weak dependence of clot mass loss on duty cycle was noted. We conclude that 120-kHz and 1-MHz ultrasound enhances thrombolysis. [Work supported by Senmed Medical Ventures.]

Ultrasound-enhanced tissue plasminogen activator thrombolysis in an in vitro porcine clot model

“…In this study, two simple designs for ultrasound application at 120 kHz and 1 MHz were tested in an in vitro porcine clot model. The synergistic thrombolytic effect of recombinant tissue plasminogen activator (rt-PA) and either 120-kHz or 1-MHz pulsed or continuous wave ultrasound was assessed in vitro [27][28][29]. The objective of this study was to determine the thrombolytic efficacy of pulsed ultrasound over a range of duty cycles at moderate pressure amplitudes.…”

Ultrasound-facilitated thrombolysis using tissue-plasminogen activator-loaded echogenic liposomes

“…Whole porcine blood clots were used to evaluate thrombolysis [22]. Blood was obtained from non-heparinized Yucatan miniswine.…”

Correlation of cavitation with ultrasound enhancement of thrombolysis

“…This kilohertz ultrasound frequency regime with lower intensities has been investigated in several transcranial applications to enhance thrombolysis (Akiyama et al 1998;Behrens et al 1999). A 120-kHz ultrasound thrombolysis system (UTS) has also shown significant enhancement of thrombolysis in vitro when used adjuvant to rt-PA (Cheng et al 2004(Cheng et al ,2005Datta et al 2005;Holland et al 2002;Shaw et al 2001). A 2 MHz transcranial Doppler has also been shown to augment t-PA-induced arterial recanalization in patients (Alexandrov et al 2004b).…”

“…The addition of ultrasound with clinically relevant intensities and frequencies has enhanced the enzymatic rate of thrombolytic therapy in vitro (Blinc et al 1993;Francis et al 1992;Holland et al 2002;Lauer et al 1992;Olsson et al 1994;Shaw et al 2001), in animal models (Kashyap et al 1994;Lou et al 1996;Suchkova et al 2000) and in clinical trials (Alexandrov et al 2004a(Alexandrov et al ,2004b. Acceleration of thrombolysis is a particularly critical issue for acute treatment of ischemic stroke.…”