Augmentation of in-stent clot dissolution by low frequency ultrasound combined with aspirin and heparin. An ex-vivo canine shunt study.
ABSTRACT Ultrasound can accelerate clot dissolution in vitro and in vivo. We used an ex vivo canine shunt to investigate low frequency ultrasound effects on platelet-rich stent thrombosis.
Nitinol stents were expanded to 2 mm in diameter in two perfusion chambers in a parallel shunt and exposed to flowing arterial blood at 2100 s(-1) to generate stent thrombi (n=224 perfusion runs). Dethrombotic effects were assessed during treatment with saline and combined treatment with aspirin and heparin. One stent was exposed to ultrasound (27 kHz, 1.4 W/cm2), while the other was not. Stent thrombi were weighed before and after treatment. There was no significant effect of ultrasound during saline infusion. Treatment with aspirin+heparin alone reduced thrombus weight by 37+/-25% (18.9+/-6.1 to 11.8+/-7.7 mg, p<0.0001). Combined treatment with aspirin+heparin+ultrasound produced a 49+/-23% reduction in thrombus weight (19.0+/-6.3 to 9.6+/-7.8 mg, p<0.0001). The reduction in thrombus weight was significantly greater in aspirin+heparin+ultrasound compared with aspirin+heparin alone (p=0.04).
Transcutaneous ultrasound significantly enhances dethrombotic effect of aspirin plus heparin on preformed stent thrombi. These findings suggest the potential of ultrasound as an adjunct to antithrombotic therapy to improve effectiveness without increasing the risk of bleeding complications during treatment of vascular thrombosis.
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ABSTRACT: The MIST Therapy wound healing device (Celleration, Eden Prairie, MN, USA), which uses low-frequency ultrasound to deliver an atomized saline spray to acute wounds, was evaluated in a laboratory environment. The output of the MIST device was characterized by its frequency, transmission in the presence and absence of the saline spray and intensity. When measured up to 500 mm away from the transducer tip, the transmission of 39.5 kHz ultrasound was not significantly attenuated by the saline itself. In the absence of the saline spray, the acoustic intensity range of the MIST device was calculated to be 429-188 mW cm(-2) across the manufacturer-specified treatment range (12.5-20 mm). Because of the acoustic impedance mismatch between air and soft tissue, the MIST Therapy device would deliver only 0.1% of this incident intensity into the wound site.Ultrasound in medicine & biology 04/2013; · 2.46 Impact Factor