Gorlin formulas for aortic regurgitant and mitral regurgitant orifice areas: experimental studies

The measurement of aortic regurgitant and mitral regurgitant orifice areas has recently been pioneered. The present study tried to establish Gorlin formulas for aortic regurgitant and mitral regurgitant orifice areas for evaluating the severity of aortic regurgitation and mitral regurgitation.

Seventeen stable hemodynamic states for mitral regurgitation and 22 for aortic regurgitation were studied in sheep. Aortic regurgitant and mitral regurgitant orifice areas were determined by dividing regurgitant volume per second by the time integrals of the continuous aortic regurgitant and mitral regurgitant wave velocities. Aortic regurgitant and mitral regurgitant orifice areas calculated by the formulas using echocardiographic data were compared with other measurements by electromagnetic flowmeters.

The Gorlin formulas were aortic regurgitant orifice area = per second valve flow/ 50.7 square root mean pressure gradient, and mitral regurgitant orifice area = per second valve flow/ 27.5 square root mean pressure gradient. Simple linear analysis between aortic regurgitant fractions, regurgitant volume per beat and peak aortic regurgitant flow rates, and aortic regurgitant orifice areas derived from the formula showed moderately good relationships (r = 0.73, 0.81 and 0.83). Mitral regurgitant orifice areas calculated by the formula also correlated with mitral regurgitant fractions, regurgitant volume per beat and peak mitral regurgitant flow rates (r = 0.86, 0.92 and 0.74).

The Gorlin formulas for aortic regurgitant and mitral regurgitant orifice area may provide an index for evaluating the severity of regurgitation.