Mechanical fragility of erythrocytes in normals and in patients with heart valve prostheses.

Abstract

Abstract. Hemolysis following insertion of heart ball valves shows great individual differences. Besides the mechanical properties of the prosthetic valves, individual variations in the mechanical fragility (MF) of the erythrocytes might be important in this respect. The MF has been studied with the hemoresistometer of Fleisch and Fleisch, which exposes the cells to a standardized trauma by rotation of the blood in a cylindrical chamber. The MF is defined as the amount of heme liberated. A normal material is presented, and the error of the method and the normal variation of the MF are estimated, using two different rotors. The hemoresistometer seems to be a valuable tool for evaluation of the MF, offering several advantages compared to other methods. Reference has been made to a material of nine consecutive patients with heart valve disease examined before and after prosthetic ball valve implantation. All had a normal MF before the operation, and the mean MF remained normal in spite of moderate intravascular hemolysis developing in all but one patient postoperatively. In four patients with valve prostheses readmitted for hemolytic anemia the plasma heme concentrations were markedly increased, but the MF was normal. The question whether a lowered MF may be the cause of the severe intravascular hemolysis developed by some patients remains unsettled, but the present study suggests that individual differences in MF are of minor importance for the development of severe hemolytic anemia in these patients.