Echographic method for the estimation of cardiac output from mitral-valve area, heart rate, and diastolic-filling period in conditions of mitral stenosis: correlation with cardiac catheterization.

An orifice equation for the non-invasive measurement of mitral-valve area is demonstrated. It is shown that by combining this expression with the assumption of mitral-valve area invariance an orifice equation for the non-invasive assessment of cardiac output in conditions of mitral stenosis using simple echographically measureable variables can be developed. This equation is V = (21)-1 R X A X T2, where V = cardiac output in ml, R = heart frequency, A = mitral-valve area in cm2 and T = diastolic-filling period in sec X min-1. These results suggest that when mitral-valve area is accurately measured at one point in time, cardiac output may be measured at subsequent times at a clinically useful level from a knowledge of the echographically measurable variables of heart rate and diastolic-filling period.