Extrakorporale Lipidelimination (LDL-Apherese) in der Behandlung der familiären Hypercholesterinämie: Differentialfiltration versus Dextransulfat-Adsorption - Extracorporeal Lipid Elimination (LDL-apheresis) in the Treatment of Familial Hypercholesterolemia: Differential Filtration versus Dextran Sulfate Adsorption