Determination of Cardiac Output and Pressure Gradients at Operation

Abstract

PRECISE evaluation of the results of mitral or aortic commissurotomy has been dependent upon the measurement of pressure gradients by means of left-sided heart catheterization and of cardiac output before operation and in the postoperative period.^{1 2 3 4} The immediate effectiveness of the commissurotomy can be determined to some extent by measurements of the gradient in the course of the operation.^{5 , 6} In the presence of valvular stenosis, however, blood flow is turbulent, and pressure gradients are proportional to the square of the flow rate.⁷ Thus, relatively small alterations in flow through the valve may result in large changes in the pressure gradient. . . .