Intravascular hemolysis after mitral and aortic valve replacement with different types of mechanical prostheses

Heart valve replacement with mechanical prosthesis is associated with mild intravascular hemolysis. In this study we evaluated the incidence of hemoly sis in patients with different combinations of two mechanical valves. Betwe en 1974 and 1996, 680 patients underwent mitral and aortic Valve replacemen t with mechanical prostheses; we selected 90 patients, divided into six gro ups according to the prosthetic model (Group A, ball and tilting disc; Grou p B, ball and bileaflet; Group C, tilting disc and tilting disc; Group D, t ilting disc and bileaflet; Group E, bileaflet and tilting disc; Group F, bi leaflet and bileaflet; respectively, in mitral and aortic position). Blood tests were performed to check blood hemoglobin serum lactic dehydrogenase, percent-correlated reticulocyte fraction, serum haptoglobin, and schistocyt es. Chi square test was performed for categorical data. ANOVA and Bonferron i tests were performed in order to evaluate significant statistical differe nces between media and variance of the hematological data. A mild degree of intravascular hemolysis was observed in 30% of patients with double mechan ical prostheses. LDH values were above the normal values in all groups, alt hough a significant difference was found only between Group B versus Groups C and D. Reticulocytes and schistocytes and serum haptoglobin values were within the normal range and no differences were found between the groups. L ow levels of blood hemoglobin were found in Groups D and F. The difference was statistically significant when compared with Groups A and E. In conclus ion, hemolysis is frequent but never severe in patients with mitral and aor tic mechanical prostheses. A higher incidence of subclinical hemolysis was found in patients with bileaflet valves regardless of the position of the i mplant. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.