Study of platelet diameter distribution in patients with valvular heart disease and with prosthetic heart valve replacement.

We have studied the platelet count and the megathrombocyte index (MI), or percentage of platelets that have a diameter greater than 2.9 micrometers, in 100 patients with valvular heart disease. The mean platelet count is significantly lower than in controls (p less than 0.0005) and the MI is significantly increased (p less than 0.01). No difference was observed in these two parameters according to the variety of the valvular heart disease. 45 of the same patients were studied after prosthetic heart valve replacement. Our results show a significant elevation of platelet count and a significant decrease of MI compared with the presurgical values in all groups except in the mitral one in which MI remains increased. This work demonstrates the presence of platelet abnormalities which reveal a compensated thrombocytolytic state in patients with valvular heart disease and its partial correction after aortic, but not mitral, valve replacement.