The hemodynamic effects of double-orifice valve repair for mitral regurgitation: a 3D computational model

Objectives: A 3D computational model has been implemented for the evaluatio n of the hemodynamics of the double orifice repair. Critical issues for sur gical decision making and echo-Doppler evaluation of the results of the pro cedure are investigated. Methods: A parametric 3D computational model of th e double-orifice mitral valve based on the finite elements model has been c onstructed from clinical data. Nine different geometries were investigated, corresponding to three total inflow areas (1.5, 2.25 and 3 cm(2)) and to t hree orifice configurations (two equal orifices, two orifices of different areas, i.e. one twice as much the other one, and a single orifice). The sim ulations were performed in transit; the fluid was initially quiescent and w as accelerated to the maximum flow rate with a cubic function. For each cas e, some characteristic values of velocity and pressure were determined: vel ocities were calculated downstream of each orifice, at the centre of it (V- cen1, V-cen2). The maximum velocity was also determined for each orifice (V -max1, V-max2). Maximum pressure drops (Delta p(max)) across the valve were compared with the estimations (Delta p(Bernoulli)) based on the Bernoulli formula (4 V-2). Results; In each simulation, no notable difference was obs erved between V-cen1 and V-cen2, and between V-max1 and V-max2, regardless of the valve configuration. Maximum velocity and Delta p(max) were related to the total orifice area and were not influenced by the orifice configurat ion. Delta p(Bernoulli) calculated with V-max was well correlated with the Delta p(max) obtained throughout the simulations (y = 0.9126x + 0.3464, r = 0.996); on the contrary the pressure drops estimated using V-cen underesti mated (y = 0.6757x + 0.3073, r = 0.999) the actual pressure drops. Conclusi ons: The hemodynamic behaviour of a double orifice mitral valve does not di ffer from that of a physiological valve of same total area: pressure drops and flow velocity across the valve are not influenced by the configuration of the valve. Echo Doppler estimation of the maximum velocities is a reliab le method for the calculation of pressure gradients across the repaired val ve. (C) 1999 Elsevier Science B.V. All rights reserved.