Abstract
A new method for the quantitative estimation of aortic regurgitation is reported in this paper. A mathematical model of the transport porcess of a radioisotope in a circulatory system with aortic regurgitation is developed and a simulation circuit of the transport process using analog computer is given. On the mathematical model, the regurgitation at the aortic valve is expressed as a back flow from the aorta with a transport delay equivalent to one cardiac cycle. The rate of regurgitant flow, as given by the ratio of regurgitant flow to the total outflow from the left heart, is determined after curve fitting between an actual radiocardiogram and a theoretical one produced by the simulation circuit for a moderate or large regurgitation, in cases where a definite change appears on the radiocardiogram. It is difficult to determine the rate of regurgitant flow for a small regurgitation of less than 30%. As a result of the simulation study of many radiocardiograms with aortic regurgitation, the following is made clear: (1) Rates of regurgitant flow obtained by the simulation are well correlated to those measured by left ventricular angiography; (2) A linear relationship exists between the computed mean left heart volume and the mean left ventricular volume by angiography; (3) In 31 radiocardiograms with isolated aortic regurgitation, the computed mean left heart volume increases linearly in proportion to the regurgitant volume per beat; (4) Pulmonary blood volume shows a slight but significant increase and it does not show any correlation with the grade of regurgitation; (5) Mean right heart volume does not increase and the ratio of mean right heart volume to mean left heart volume is inversely correlated with the rate of regurgitant flow.
