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Eur J Cardiothorac Surg 1999;15:419-425
© 1999 Elsevier Science NL

The hemodynamic effects of double-orifice valve repair for mitral regurgitation: a 3D computational model¹

^a Cardiac Surgery Department, IRCCS, San Raffaele Hospital, Via Olgettina 60, 20132, Milan, Italy
^b CEBITEC, Politecnico di Milano, Milan, Italy

Received 22 September 1998; received in revised form 27 January 1999; accepted 2 February 1999.

Corresponding author. Tel.: +39-2-2643-7109; fax: +39-2-2643-7125; e-mail: maisano.francesco@hsr.it

Objectives: A 3D computational model has been implemented for the evaluation of the hemodynamics of the double orifice repair. Critical issues for surgical decision making and echo-Doppler evaluation of the results of the procedure are investigated. Methods: A parametric 3D computational model of the double-orifice mitral valve based on the finite elements model has been constructed from clinical data. Nine different geometries were investigated, corresponding to three total inflow areas (1.5, 2.25 and 3 cm²) and to three orifice configurations (two equal orifices, two orifices of different areas, i.e. one twice as much the other one, and a single orifice). The simulations were performed in transit; the fluid was initially quiescent and was accelerated to the maximum flow rate with a cubic function. For each case, some characteristic values of velocity and pressure were determined: velocities 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 (p_max) across the valve were compared with the estimations (p_Bernoulli) based on the Bernoulli formula (4 V²). Results; In each simulation, no notable difference was observed between V_cen1 and V_cen2, and between V_max1 and V_max2, regardless of the valve configuration. Maximum velocity and p_max were related to the total orifice area and were not influenced by the orifice configuration. p_Bernoulli calculated with V_max was well correlated with the p_max obtained throughout the simulations (y=0.9126x+0.3464, r=0.996); on the contrary the pressure drops estimated using V_cen underestimated (y=0.6757x+0.3073, r=0.999) the actual pressure drops. Conclusions: The hemodynamic behaviour of a double orifice mitral valve does not differ 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 reliable method for the calculation of pressure gradients across the repaired valve.

Key Words: Valve repair • Computer modelling • Mitral regurgitation • Echo-Doppler