Abstract
A continuous recording of the changes in the right atrial diameter by ultrasonic method is a useful tool for a study of the mechanism of venous return including dynamic performances of right atrium. The technique of sonomicrometer for measuring right atrial dimension was reported by G. Recordati using H. F. Stegal's method for the time in the cat. His method meets with a difficulty of keeping accuracy and stability and, besides, it needs the complicated adjustment to measure fine change within a little distance such as the dynamic change of the right atrial diameter. These difficulties have been overcome by the method which converted the transit time of ultrasound to the phase differences of square wave due to the analog conversion with phase comparator.
With this technique of sonomicrometry, the dynamic change of right atrial diameter could be accurately measured and continuously recorded, so that the active contraction and passive filling phase of right atrium, which is an important performance of functional behavior of right atrium in the mechanism of venous return, was clearly discerned, and also, the effect of dopamine on these, phase was markedly recognized.
