Effects of ultrasound energy application on cardiac performance in open-chest guinea pigs - An in vivo pilot study

Background: Although ultrasound (US) is widely used in cardiology, little is known about the effects of US energy on cardiac performance. This study aimed to investigate the mechanical effects of high-intensity continuous US energy (1.0 MHz with 3 different intensities) on cardiac performance. Methods and Results: Either left ventricular (LV) pressure or aortic blood flow (ABF) was evaluated in open-chest guinea pigs (n=30) under surface ECG monitoring. LV systolic pressure and ABF increased significantly (ie, maximum percent increases in these parameters were 2.5%, 3.1% and 7.1% for LV systolic pressure and 9.4%, 4.9% and 8.8% for mean ABF at intensities of 0.06, 0.67 and 2.90 W/cm ², respectively). LV end-diastolic pressure was reduced significantly by US (5.3±0.9 to 4.8±0.8, 5.5±1.3 to 4.8±1.0 and 5.8±2.0 to 5.0±1.2 mmHg, respectively), indicating positive inotropic and lusitropic effects and resultant ABF augmentation. Local temperature was not significantly changed. ECG showed neither chronotropic action nor arrhythmogenesis. Conclusions: Although the basic mechanisms of these phenomena remain unclear, this pilot study of the short-term effects of US energy on cardiac performance suggests the possibility of physical therapy for heart failure.