Three-dimensional 130) echo reconstruction can potentially allow us to address uniquely 3-dimensional questions of scientific interest: for example. the effect of 3D leaflet geometry proximal to the limiting orifice of a stenotic valve on the coefficient of orifice contraction (Cc) = the effective orifice area (venacontracta)lthe anatomic area. This is important because: 1) for a given flow rate and anatomic area. a lower Cc gives a higher maximal velocity, pressure gradient, and possible head loss; and 2) Cc. assumed constant in the Gorlin equation. may vary with valve shape (62% for a flat plate. 100% for a long tube). To date. it has not been possible to study this effect with the actual 3D shapes of valves in patients. We therefore used a spark gap system with respiratory and ECG gating to reconstruct leaflet funnel geometries typically seen in patients with mitral stenosis (MS) at maximal leaflet opening: a mobile. doming valve and an immobile valve with a flatter conical funnel. 3 models of each geometry were then constructed by stereolithography (computerized laser polymerization), with orifice areas of 0.5, 1.0 and 1.5 cm2. Effective area (flow rate/continuous wave Doppler velocity) and Cc were determined for flow rates producing velocities of 1–3 m/s. Results Cc varied minimally with flow rates. but prominantly with shape (averages of flow rates follow): Anat. Orifice area, cm2 Dome Flat funnel 1.5 0.89 0.79 1.0 0.82 0.71 0.5 0.76 0.66 1) For any anatomic area, Cc was larger for the longer tapered dome, which allows more gradual flow convergence proximal to the limiting orifice (less distal contraction). (2) For each funnel shape, Cc increased with increasing orifice to proximal funnel size (more tube-like). Conclusions Cc, which can alter net head loss, is importantly affected by the variations in leaflet geometry seen in patients. Echo stereolithography can allow us to address such uniquely 3D questions.