Platelet survival in patients with prosthetic heart valves

Chromium-51 platelet survival studies were carried out in 20 patients with a prosthetic heart valve. Only 1 of 10 patients with a prosthetic mitral valve had a significantly shortened platelet survival time, and the mean value of 8.3 ± 0.96 (±1 standard deviation) days was not significantly different from that of normal control subjects (8.9 ± 0.75 days). Four of 10 patients with an aortic prosthesis had a shortened platelet survival time, and the mean value of 7.8 ± 0.10 days in this group differed significantly from the normal control value (P < 0.05). Treatment with aspirin did not appear to alter platelet survival but, when combined with Coumadin therapy, resulted in marked prolongation of bleeding time. Our results do not support the concept that thrombus formation on the prosthesis is the cause of the shortened platelet survival time since thrombus formation is more likely to occur in mitral than aortic prostheses. Reduced platelet survival time secondary to damage by the prosthesis, similar to the problem of hemolysis in red blood cells, is a more likely explanation.