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

Doppler echocardiography was applied to the assessment of patients with surgically documented St. Jude medical aortic valve dysfunction. Derivation of effective orifice area and Doppler velocity index with the continuity equation and calculation of valve resistance accurately differentiated stenotic from regurgitant and normal valves.