In vivo platelet release reaction in patients with heart valve prosthesis.

Platelets play an important role in the genesis of thromboembolic episodes frequently observed in patients following cardiac valve replacement. No simple and reliable method as yet exists for quantitating platelet function in vivo. Platelet-specific proteins, serum beta-thromboglobulin related antigen and platelet factor 4 as well as thromboxane B2 were measured in 50 healthy subjects and in 100 patients who had cardiac valve replacement at least 6 months previously; these were related to the type, site and number of valves replaced. Highly significant differences were observed in the mean plasma beta-thromboglobulin related antigen, platelet factor 4 and thromboxane B2 levels in patients compared with healthy controls. The elevated levels of platelet release products observed 6 months after cardiac valve replacement suggest a continuous activation by the prosthesis. No significant differences were observed in patients with different types and site of valve prosthesis.