Direct ultrasound application had no effect on cardiac hemodynamic performance in a baseline isolated rat heart model

Therapeutic ultrasound (US) has been used for more than 3 decades to promot e tissue healing in cases of tissue injury and muscle soreness. It was prev iously suggested that US may have vasorelaxatory and inotropic properties. However, the direct effect of therapeutic US in a whole heart model has not yet been investigated. Our hypothesis was that application of US might enh ance cardiac function. The Langendorf model was modified in a special manne r to allow application of US to the heart. Using this model, 20 male rats w ere equally divided into two groups. Group 1: the hearts were perfused for 15 min, to obtain baseline measurements, and then they were perfused for an other 15 min in a special bath full of perfusate. Group 2: after 15 min of baseline measurements, continuous US of 1 MHz 2 W/cm(2) was applied for ano ther 15 min. The parameters that were measured at 5-min intervals were: lef t ventricular pressure P(max), first derivative of the rise and fall in lef t ventricular pressure (dP/dt(max), dP/dt(min)), and pressure-time integral . There was no significant difference between the two groups in all paramet ers at baseline and during US application. P(max) and dP/dt(max) remained c onstant. After 15 min of US propagation, P(max) was 98% +/- 3 from baseline level vs. 98% +/- 7 in the control group, and dP/dt(max) was 98% +/- 3 vs. 99% +/- 9 in the control. In dP/dt(min), a gradual decline after 15 min of perfusion was measured. In the US- treated group, it declined to 80% +/- 1 0 vs. 83% +/- 5 in the controls. In conclusion, US radiation at the dose sp ecified does not improve healthy isolated heart hemodynamic performance. We established a model that may be used for further investigation. (C) 2000 W orld Federation for Ultrasound in Medicine & Biology.