[Development and experimental investigation of an ultrasound myocardial stimulator for clinical application]

Recently there has been considerable experiments on biological and clinical application of ultrasound. However, the effect of ultrasound on cardiac function has not been fully understood. We have already reported the effect of the ultrasound myocardial stimulation (U.M.S.) in isolated rat heart. This study was undertaken to examine the potentiality of U.M.S. in clinical application. Twenty four mongrel dogs were divided into four groups, group I: ultrasound was irradiated in front half of the reperfusion time, group II: it was irradiated in last half of the reperfusion time group III: it was irradiated fully during the reperfusion time, group IV: it was not irradiated. The stimulator has the intensity of 1.5 W/cm2 in group I, II 0.1 W/cm2 in group III at the frequency of 1.23 MHz continuous wave, during early systolic phase (200 msec.) for twenty minutes. The right heart bypass model was used in the constant mean aortic pressure (75 mmHg) and rate (120 beats/min). The change in left ventricular function was defined as percent of control in the center of mass of Sarnoff curve. The change in end-diastolic, end-systolic segmental length and % shortening were measured. The result of left ventricular function recovery rate were follows, 74.9 +/- 9.13% in group I, 61.0 +/- 8.95% in group II, 78.7 +/- 14.1% in group III, 58.4 +/- 13.5% in group IV in measurement 1 (twenty minutes after reperfusion), and 77.6 +/- 9.45% in group I, 86.7 +/- 8.85% in group II, 86.8 +/- 16.3% in group III, 64.8 +/- 10.6% in group IV in measurement 2 (fifty minutes after reperfusion), indicating that U.M.S. had a significantly better recovery rates. As for end-diastolic, end-systolic segmental length and % shortening, the group that ultrasound was irradiated had a significantly better recovery in both measurement 1 and 2. CPK flow levels per minutes at 15, 35 minutes after reperfusion were significantly lower in the group receiving U.M.S. (p less than 0.05). Lactate extraction were higher in the group receiving U.M.S. at 35 and 45 minutes after reperfusion (p less than 0.05). Redox potential at 45 minutes after reperfusion were also found to be significantly higher in the group receiving U.M.S. (p less than 0.01). In conclusion, 1) U.M.S. possesses positive inotropic action. 2) U.M.S. also effective in preventing the occurrence of myocardial damage. 3) Myocardial metabolism was more aerobic in the group receiving U.M.S. particularly in group III (0.1 W/cm2). 4) These data indicated that U.M.S. has the potentiality in clinical application.