Abstract
Incidence and severity of thromboembolism (T. E.) associated with various types of valve prostheses were surveyed. A total of 576 patients who survived 1 month or longer after isolated mitral valve replacement was divided into three groups depending on flow characteristics of valve prosthesis implanted Group I had the lateral flow type valves, such as Starr-Edwards ball valve and SAM valve (85 cases); Group II had semi-central flow type valves of tilting disc prostheses (345 cases) and Group III had central flow type valve of porcine bioprostheses (146 cases). Severity of T. E. was classified as follows; I° when symptoms were improved within 1 month after onset, II° when they persisted 1 month or longer, and III° when T. E. caused fatality. T. E. occurred in 40 patients among the 576 operative survivors (6.9%). Incidence was highest in group I (16/85, 18.8%; 2.9%/patient-year). By contrast, both of groups II and III showed equally low incidence; that is, 16/345, 4.6%; 1.2%/pt-yr in group II and 11/146, 7.5%; 1.8%/pt-yr in group III. Prognosis of T. E, was poorest in group I in which 8 patients showed II° and the remaining 8 were in III°. Symptoms and prognosis of T. E. were milder in group III than in group II. None of the group III was subjected to fatal cerebral embolism, while two patients of group II were lost due to massive brain infarction.
These results suggest that the flow characteristics of the valve prosthesis is importantly involved not only in incidence but also in severity of thromboembolism following mitral valve replacement.
