Ball valve prostheses: current appraisal of late results.

Advanced actuarial techniques are used to analyze late results in 912 patients who had isolated mitral or aortic valve replacement with ball valve prostheses from 1965 to 1974. Experience with noncloth-covered and cloth-covered valves is compared in terms of late survival, rate of thromboembolic complications and reoperation and the influence of anticoagulation. The cloth-covered prostheses have substantially reduced the incidence of emboli after mitral valve replacement (1.9 vs. 6 emboli per 100 patient years) and have thus far eliminated emboli after aortic valve replacement in patients receiving warfarin. Patients with a cloth-covered aortic valve who did not receive warfarin had nine emboli per 100 patient years. The safety of cloth-covered valves is clearly enhanced by warfarin therapy; the efficacy of anti-platelet drugs is still uncertain. Strut cloth wear was found at reoperation in 10 patients. This should be prevented in the new model 2400 composite strut ("track") valve by a narrow metal track on the inner surface of each strut. The substantial recent reductions in operative mortality and in prosthesis-related complications pose important questions regarding timing of operations and selection of prostheses. These decisions must be individualized for each patient on the basis of a thorough analysis of late results using modern statistical methods.