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ECHONOMY
Tools for Echocardiographic Calculations
Muhamed Saric, MD, PhD
New York University
 

Gorlin Eq.

Purpose
To calculate the mitral or aortic valve based on a formula that combines the fundamental equation of fluid mechanics (flow = velocity * area), and the Bernoulli equation (which expresses velocity in terms of pressure). The formula was devised by a father and son team: S.G. Gorlin (father, an engineer), and Dr. Richard Gorlin (1926-1991; son, a cardiologist).

Technical Hints
The original Gorlin formula is used for the aortic valve area. Based on an empiric constant, the mitral valve area is 85% of the valve area calculated by the original Gorlin formula.

Calculator

Cardiac output  (CO)

 milliliters/minute

Flow period (FP)
SEP (systolic ejection period for aortic valve)
DFP (diastolic flow perior for mitral valve)

 seconds

Mean pressure gradient (MPG):

 mm Hg

Heart rate (HR):

 beats per minute


 		  

Answers
Aortic valve area  cm2

Mitral valve area

 cm2

Formula

Valve area = k * [CO / (44.3 * HR * FP * sq root of MPG)]

k = 1 for aortic valve

k = 0.85 for mitral valve

References

Gorlin R, Gorlin SG. Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valves, and central circulatory shunts. I. Am Heart J. 1951 Jan;41(1):1-29. Reevaluated in J Am Coll Cardiol. 1990 Jan;15(1):246-7.