Platelet and blood clotting activation in patients with mitral valve prolapse.
In patients with mitral valve prolapse (MVP) a high incidence of valvular abnormalities with a history of previous cerebrovascular disease has been reported and an embolic mechanism has been proposed. Aim of this study is the study of platelet and coagulation activation in patients with MVP. Fifty-four patients affected by MVP (mean age 46 +/- 15 yrs, 22 males, 32 females) and 50 control subjects, age- and sex-matched, were tested for platelet activation [P-selectin and GpIIb-IIIa platelet surface expression at rest and after stimuli by flow cytometric analysis, Beta-Thromboglobulin (TG) and Platelet Factor 4 (PF4) plasma levels by ELISA, platelet-rich-plasma (PRP) and whole blood spontaneous platelet aggregation (SPA)] and for activation of blood coagulation (Prothrombin activation fragment F1+2 plasma levels by ELISA). P-selectin, GpIIb-IIIa expression, Beta-TG, PF4 and SPA were found similar in MVP patients and in controls. However, in patients with severe mitral regurgitation (MR) the percentage of activated platelets which express P-selectin after stimuli was slightly but significantly (p < 0.05) lower in comparison to MVP patients without or with mild to moderate MR and to controls. Moreover, in patients with severe MR F1+2 levels (median 1.6 nmol/L, range 0.6-2.6 nmol/L) were significantly higher (p < 0.001) than both in controls (median 0.95 nmol/L, range 0.2-1.4 nmol/L) and in patients without or with mild to moderate MR (median 1.0 nmol/L, range 0.4-2.3 nmol/L). Our findings suggest that MVP is not responsible per se for blood clotting activation, but in patients with severe mitral insufficiency an increase in thrombin generation can occur. These alterations in hemostatic system may represent a mechanism by which MR increases the risk of thromboembolic events in patients with MVP.