Isolated mitral valve replacement with the Björk-Shiley tilting disc valve prosthesis. A six-year review and a comparison between the Delrin and the pyrolytic carbon disc models.

Replacement of the mitral valve with the Björk-Shiley tilting disc valve prosthesis was performed in 203 consecutive patients with isolated mitral valvular disease at Karolinska Sjukhuset, Stockholm, Sweden, during the 6-year period ending December 1975. Results with the Delrin and pyrolytic carbon disc prostheses were analysed with actuarial techniques and compared in terms of mortality rate, incidence of thrombo-embolism and frequency of re-operation. Early (4%) and late mortality rates (7.5 deaths per 100 patient years) were similar with both types of prostheses. No case of primary mechanical prosthetic failure was encountered. The pyrolytic carbon disc prostheses have obviously decreased the incidence of systemic emboli from 9.6 to 5.3 per 100 patient years and so far eliminated mortality due to embolization. This benefit is probably related to the increased opening angle from 50 degrees to 60 degrees in the pyrolytic carbon disc model, which causes less resistance to blood flow. Thrombotic obstruction of the prosthetic valve, however, has been a persistent problem in the order of 3.3 incidences per 100 patient years. Only one patient in twelve involved was referred to our clinic and could be saved by an emergency re-operation. The development of the ring-shaped radiopaque marker in the tilting disc occluder provides a valuable tool for instant diagnosis of partly or completely obstructed disc motion caused by thrombosis. Disc motion can be easily visualized by cineradiography or fluoroscopy. Early diagnosis of and emergency operation for thrombotic obstruction of the prosthesis will reduce the mortality due to this dangerous complication.