Doppler echocardiographic assessment of prosthetic aortic valve area: Estimation with the continuity equation compared to the Gorlin formula

Effective orifice area of 3 different designs of prosthetic valves implanted in the aortic position was determined by the continuity equation and the Gorlin formula using Doppler hemodynamic data.The orifice area by the two methods correlated well in the case of tilting disc prostheses (r = 0.75, P = 0.0001, N = 37, SEE = 0.17 cm2) but poorly in the case of bileaflet mechanical valves (r = 0.40, P = 0.17, N = 13) and ball-in-cage prostheses (r = 0.58, P = 0.06, N = 11). Estimation of prosthetic aortic valve area by the Gorlin formula is inappropriate in the latter two types of prostheses because of design-related variable empiric constant.