Effect of high power ultrasound on the heart: in vitro and in vivo experiments

Author(s)

Olívia Campos Coiado

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Elétrica e de Computação
• Defense date: 2012-08-15

Examining board members

Eduardo Tavares Costa; Coelho de Albuquerque Pereira; Antonio Adilton Oliveira Carneiro; Pedro Xavier de Oliveira; Wilson Nadruz Junior

• Advisor: Rosana Almada Bassani; Eduardo Tavares Costa

Abstract

In recent years, the use of ultrasound in diagnosis and therapy is increasing and new techniques have been improved and developed for new applications as, for instance, in alternative treatment of heart failure. The goal of this study was to investigate the biological effects (in vitro and in vivo) on rat heart of ultrasound waves (1 MHz center frequency) in order to identify stimulatory patterns that may be damaging or that may be used therapeutically for heart rhythm disturbances. In the in vitro experiments, 7 isolated perfused rat hearts, were stimulated with ultrasound bursts for 30 s and intensity ranging from 0.6 to 8 W. Negative chronotropic effect was observed (without inotropic effect) more consistently (15-20%) at the stimulatory frequency of 3 Hz with intensities of 0.62 to 5.54 W but this effect was transient and not dependent on the duty cycle used. We observed arrhythmia in the presence of ultrasound, but no significant variation in temperature. In the in vivo experiments 20 rat hearts were stimulated for 10 s with ultrasound bursts of 2-3 MPa. The experiments were divided into five groups each consisting of 5 animals: 1) preliminary, 2) ultrasound control, 3) ultrasound, 4) vagotomy, control and 5) vagotomy, ultrasound. The preliminary group of experiments, we observed the negative chronotropic effect of ultrasound (~ 7% decrease in heart rate immediately after application of ultrasound), previously reported. In the other groups, in which we have tried to determine the possible variation in blood pressure and the influence of the parasympathetic system on the negative chronotropic effect, there were no significant changes in the variables studied. Additional studies are needed to clarify the effects of high power ultrasound application on rat heart (AU)