Application of the continuity equation and valve resistance to the evaluation of St. Jude Medical prosthetic aortic valve dysfunction

In summary, the application of the continuity equation and valve resistance provides a reliable method to distinguish whether high velocities and gradients through St. Jude aortic valves are secondary to obstruction or increased flow. The Doppler parameters that differentiate stenotic from regurgitant and normal valves were effective orifice area, Doppler velocity index, and valve resistance. Whether the use of valve resistance allows a better discrimination between stenotic and normal or regurgitant valves remains to be determined.