In vitro and in vivo studies with different precipitate filter cartridges for H.E.L.P.-LDL-apheresis. Optimization of precipitate filter cartridges.

Heparin-induced extracorporeal LDL-precipitation has successfully been used in lowering high serum cholesterol in patients with coronary heart disease due to familial hypercholesterolemia. In the continuous search to improve treatment facilities we attempted to increase the filtration capacity of low density lipoprotein by the precipitate filter of the H.E.L.P.-system. Therefore, the nominal filtration area was varied by decreasing the pleat count as well as the configuration of the precipitation filter membrane. The device was tested in vitro using fresh frozen plasma from healthy donors as well as in vivo treating 6 patients suffering from familial hypercholesterolemia and 18 patients with the nephrotic syndrome. The data show that the drop in pressure on the filtration side depended on the filtration volume and the filter configuration. Reducing the pleat number and in parallel the nominal filtration area by replacing the standard support on the outside of the membrane by a double or triple thick support results in an increase in plasma volume which can be treated. The optimal results were obtained using filters with a nominal filtration area of 0.8 +/- 0.1 m2 and a triple thick support on the retention side compared to the standard configuration. Therefore, even patients with extreme plasma viscosity such as patients with the nephrotic syndrome can effectively be treated by heparin-induced LDL-precipitation.