Development of a twin-flap, porous ceramic mitral valve prosthesis

The pressure drop in most existing cardiac valve prostheses is at least ten times greater than for healthy valves. Steady flow testing indicates that the causes are (i) poor orifice diameter/sewing ring diameter ratio; (ii) occluding mechanism causes obstruction in the region of highest blood velocity. A new mitral prosthesis was constructed to overcome these deficiencies. The significant features are (a) tubular construction to maximize flow area; (b) twin flaps with hinges well above the outlet to minimize obstruction; (c) divergent nozzle to aid pressure recovery. Prostheses were manufactured from porous alumina, promoting firmly anchored, thin tissue growth to reduce haemolysis and thromboembolism. Preliminary trials in mini-pigs show good valve function. The ceramic behaves especially well. Future models will use ceramic flaps to replace the delrin flaps used at present, which encourage fibrin deposits.