Haemodynamics

Question 1

The gorlin formula utilises the Coeficient of orefice contraction in the formula. What is this, and why is it used?

Answer 1

The coefficient of orifice contraction makes
allowance for the fact that fluids moving through an orifice tend
to stream through its middle so that the physiological orifice is
smaller than the physical orifice. The velocity coefficient allows
for the fact that not all of the pressure gradient is converted to
flow because some of the velocity is lost to friction within the
valve.

Question 2

What is the Gorlin equation?

Answer 2

A=F/(CcCv √2gh), where Cc and
Cv are the coefficients of orifice contraction and velocity loss,
respectively.

Question 3

What are limitations of the Gorlin equation?

Answer 3

The coefficients for orifice contraction and velocity loss have never truly been established. Gorlins used an empirical constant to make their calculated mitral valve areas align better with actual valve areas obtained at autopsy or surgery.
For the other 3 valves, not even an empirical constant has been developed. Thus, the coefficients for the aortic, pulmonic, and tricuspid valves have been assumed to be 1, a theoretical impossibility.