Hydraulic orifice formula for echographic measurement of the mitral valve area in stenosis. Application to M-mode echocardiography and correlation with cardiac catheterisation.

A mitral valve orifice equation has been formulated which allows the computation of mitral valve area (A) from the echographically measurable variables of stroke volume (SV) and diastolic filling period (DFP) in seconds per minute by the formula, A=21 (SV)/(DFP)2. Mitral valve areas computed from M-mode echographic measurements are shown to correlate with areas computed by the Gorlin formula (r-0.90) for resting state conditions of predominant mitral stenosis of clinical grades 2 to 4. The results suggest that, in the absence of wall motion irregularities, M-mode echocardiography can quantitatively assess the mitral valve area in stenosis.