Effect of externally applied focused acoustic energy on clot disruption in vitro

• Published in: Clinical science (1979) Vol. 97; no. 1; pp. 67 - 71
• Main Authors: WESTERMARK, S, WIKSELL, H, ELMQVIST, H, HULTENBY, K, BERGLUND, H
• Format: Conference Proceeding Journal Article
• Language: English
• Published: London Portland Press 01.07.1999
• Subjects: Biological and medical sciences; Diseases of the cardiovascular system; Humans; Medical sciences; Medicin och hälsovetenskap; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Thrombosis - therapy; Time Factors; Ultrasonic Therapy - methods; Sonography; Human; Acoustic energy; Instrumentation therapy; Cardiovascular disease; Experimental study; Fibrinolysis; In vitro; Thrombosis; Clot; Vascular disease; Treatment; Echography; Disruption
• ISSN: 0143-5221; 1470-8736
• DOI: 10.1042/CS19980379

Application of low-frequency ultrasound for clot disruption has been suggested as a potential therapy to enhance thrombus dissolution, but the optimal mode for delivery of ultrasound with clot-disruptive properties has not yet been extensively explored. Target-specific effects are desirable and may be accomplished by focusing the ultrasound. Adequate focusing, however, requires a short wavelength. The aim of this study was to compare the clot-disruptive effects of different modalities of focused acoustic energy. An in vitro model (10 blood clots for each modality) was used to test the clot-disruptive capacity of (i) shock waves generated in an electrohydraulic lithotriptor; (ii) focused continuous ultrasound of frequency 1.1 MHz, delivered from a specially constructed piezoelectric transducer; and (iii) focused pulse-modulated ultrasound of frequency 1.1 MHz delivered from the same transducer. Exposure to 30 s of focused pulse-modulated ultrasound caused a marked reduction (99+/-2%) in clot weight compared with 30 shock waves (11+/-5%) or 30 s exposure to focused continuous wave ultrasound (11+/-6%) (P<0.0001). The observed marked and rapid disruptive effect on blood clots of focused high-frequency ultrasound indicates an alternative approach for external ultrasound-mediated thrombus destruction in vivo. The focused pulse-modulated technique has potential to exhibit the desired effect in a well-defined target volume and provides the means for control of the average power.