Comparison of fondaparinux, low molecular-weight heparin and unfractionated heparin in preventing thrombus formation on mechanical heart valves: results of an in-vitro study.

ABSTRACT

BACKGROUND AND AIM OF THE STUDY The study aim was to investigate the efficacy of three different anticoagulants in preventing thrombus formation on mechanical heart valves, using an in-vitro system. METHODS: Blood samples (470 ml) were taken from young and healthy male volunteers and anticoagulated with unfractionated heparin (UFH; n=18), low molecular-weight heparin (LMWH; n=18) or fondaparinux (n=16). Bileaflet mechanical heart valves were placed in a new device--the 'Thrombosis Tester'--and exposed in a continuous circulation at a rate of 80 beats per min to the anticoagulated blood samples for a total exposure time of 60 min. Results for thrombus weight were skewed distributed and presented as log-transformed values. RESULTS: The weight of each valve was measured before and after 1 h of perfusion; subsequent mean (+/-SD) thrombus weights were 0.739 +/- 0.573 g for UFH, 0.789 +/- 0.099 g for LMWH, and 0.934 +/- 0.145 g for fondaparinux (p = 0.397 for comparison of all groups by ANOVA). Electron microscopy showed concordant results with regard to thrombus formation on heart valve surfaces. CONCLUSION: Fondaparinux and LMWH were as effective as UFH in preventing thrombus formation on mechanical heart valves in vitro. The 'Thrombosis Tester' proved to be a new, unique instrument for investigating the ability of anticoagulants to prevent valve thrombosis on mechanical heart valves under in-vitro conditions.