In conclusion a significant reduction of platelets activity and aggregation parameters ADP, collagen, restocetin and arachidonic acid levels and also platelets glycoproteins IIb/IIIa especially second reading intraoperatively. Significant lower values of platelets aggregation and surface expression of GPIIb/IIIa results in platelets dysfunction in both study groups and severity of postoperative blood loss and needs of blood components transfusion in addition to role of prosthesis and turbulence flow in platelets dysfunction.