A prospective study of platelet metabolism in rheumatic heart disease. Effect of prosthetic heart valve

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Abstract
The metabolic activity of platelets in patients with advanced rheumatic heart disease (RHD) was estimated by measurement of heat production in a microcalorimeter. Twenty-nine patients were randomly selected and prospectively followed before and after valve replacement with Bjork-Shiley prosthesis. Before the operation a significantly (P<0-02) elevated platelet heat production wasfound compared with normal subjects, 63 ±5 fW/cell and 59 ±4 fW/cell, respectively, probably due to the presence of a younger and metabolically more active platelet population. Platelet count before the operation was significantly lower than normal (P<0-001).Platelet heat production did not correlate with either type of valvular disease, the presence of valvular calcification or atrial fibrillation. After valve replacement the platelet heat productionsignificantly decreased (P<0-001) to 58±5 fW/cell and the platelet count normalized. The highest incidence of thromboembolic manifestations was in the immediate postoperative period. The greatest reductions in platelet heal production. 19% and 27% were observed in two patients with thromboembolic events, as compared with an average of 4% for therest of the operated patients without complications. The possible relationship between changes in platelet heat production and thromboembolism in patients with RHD is discussed.