Calculation of Valvular Area

Question 1

Gorlin Formula

Valve orifice area is =

Answer 1

Flow across the valve / (constant x sq rt pressure gradient)

Question 2

Gorlin’s equation for MVA

Answer 2

MVA = CO (ml/min) / (DFP in s/beat x HR bpm) / 37.7 x sq rt mean transmitral gradient

Question 3

Gorlin’s equation for AVA

Answer 3

AVA = CO (ml/min) / (SEP in s/beat x HR bpm) / 44.3 x sq rt mean transaortic gradient

Question 4

These equations show that for a fixed valvular area, gradient is dependent on the square of the CO. Thus, a 2-fold increase in CO almost translates into a ___________ increase in gradient, whereas a low CO translates into a low gradient even if stenosis is severe.

Answer 4

4 fold increase in gradient

Question 5

In case of atrial fibrillation, average the mean valvular gradient over ___________

Answer 5

10 beats

Question 6

True or False

In case of moderate or severe regurgitation of the same valve being evaluated for stenosis, the CO in the Gorlin’s equation falsely decreases the valve area.

Answer 6

True

CO obtained by Fick or thermodilution cannot be used in Gorlin’s equation.
This CO is the net forward systemic flow, whereas at the level of the valve, the total flow is a summation of the net forward and the backward regurgitant flow

In addition, knowing that in severe regurgitation the regurgitant flow is usually at least as large as the net forward flow, the total flow across the valve is at least twice the CO, and therefore, twice the CO may be used in Gorlin’s equation in severe regurgitation, and 1.3–1.5 times the CO may be used in moderate regurgitation.

Question 7

Give the Hakki equation

Answer 7

Valve area = CO / sq rt gradient

This formula is not well tested in patients with bradycardia (<40), tachycardia (>100), or atrial fibrillation.