Revision of Gorlin constant for calculation of mitral valve area from left heart pressures.

The constant (C= 3I) in the hydraulicformulafor calculation of mitral valve area was originally empirically determined by comparison of measured valve area at operation or necropsy with right heart catheterization data. This constant corrects, among other things, for overestimation of the diastolic filling and mitral valve gradient derived from a peripheral arterial tracing and pulmonary capillary wedge pressure, respectively. With left heart catheterization these measurements can be made directly and more accurately. In this study through simultaneous measurement of pulmonary capillary wedge, peripheral arterial, left atrial, and left ventricular pressures, a new constant (K= 40) was derived which should provide a more accurate estimation of mitral valve orifice area when left heart data are used.