Elementary echographic estimation of cardiac output independent of the symmetry and kinetic state of the left ventricle in mitral stenosis. Potential application to the determination of the circulation of pregnancy

Abstract

An orifice equation is demonstrated which is independent of the symmetry and kinetic state of the left ventricle. The expression allows calculation of the cardiac output in conditions of mitral stenosis when the mitral valve area is known. This equation is Q = (1/21) R A T2, where Q = cardiac output in ml/min, R = heart rate, A = mitral valve area and T = diastolic filling period in sec/min. Ten patients whose gynecologic or obstetric exam suggested a diagnosis of mitral stenosis were evaluated by conventional cardiac catheterization and M-mode echocardiography. Cardiac output computed using the new equation and the Fick principle corresponded at r = 0.95, SE = 340 ml, N = 10. These results suggest that cardiac output may be conveniently estimated for serial studies by the readily measurable echographic variables of heart rate and diastolic filling period once the mitral valve area has been measured by conventional catheterization or bi-dimensional echographic methods.