Comparison of Different Ldl-Apheresis Techniques

LDL-apheresis is an extracorporeal technique which removes all apo B100-containing lipoproteins (VLDL, LDL, Lp(a)) from plasma, in patients whith homozygous, and double heterozygous, familial hypercholesterolemia (FH). One of the most significant technical characteristics of LDL-apheresis is the selectivity in the removal of atherogenic lipoproteins, namely LDLs, which has been improved in the most recently developed techniques. The oldest system for therapeutic plasmapheresis in the treatment of severe hyperlipoproteinemias, is plasma-exchange, where all plasma components are unselectively removed. More recently, the systems (dextransulphate cellulose LDL-apheresis [DSC/LDL-A], heparin induced LDL precipitation-apheresis [HELP/LDL-A], immunoadsorption LDL-apheresis [IMA/LDL-A], direct adsorption of lipids [DALI]) have permitted a selective removal of LDL and of other apo B100-containing lipoproteins. The higher selectivity, thus the higher efficacy and safety, has also allowed the treatment of high risk patients with severe cardiovascular conditions, and pediatric patients. Therefore, it is currently possible to begin treatment with LDL-apheresis, even at a very early age. The most recent system for LDL-apheresis (DALI: Direct Adsorption of Lipids) even permits the removal of LDL from whole blood, without previous cell/plasma separation. This system is promising for further progress in the technology related to LDL-apheresis.

A Process for Enhancing Selectivity and Limiting Plugging in Plasmafractionation for Apob Removal

A new process using pressure and flow pulsations was investigated in the second stage of cascade filtration for ApoB removal. Due to enhanced filtration by the pulsations, the retentate flow vanished naturally without clamping the line, which reduced albumin and ApoA1 losses. The performance of Eval 4A and cellulose PF100 filters in this case were compared with that of classical dead end mode at a plasma flux of 18 ml/(min m2). The apparent sieving coefficient for small proteins (albumin, ApoA1) under pulsed conditions increased with increasing pressure instead of dropping as in dead end mode. In both cases the ApoB sieving coefficients remained below 0.02. These encouraging results were accompanied by a slower rise of transmembrane pressure showing a decrease of membrane plugging. Thus, the recovery of albumin and ApoA1 is increased while ApoB removal remains constant, which improves the selectivity of the fractionation stage.

Cascade Filtration (CF) with the Haemonetics MCS+: A New Technical Adaptation

CF was introduced in clinical medicine in 1980. Up to now, exclusively two-vein procedures have been carried out with some limitations to expansion of this technique. In this report we describe the very first application of single-needle CF carried out with Haemonetics MCS + apparatus. Twenty procedures were completed without any untoward effect in patients suffering from TTP, post-hepatitic cryoblobulinemia, familial hypercholesterolemia and acute Guillan-Barrè Syndrome. From 1 to 4 sessions were carried out per patient with the expected laboratory and clinical results. The only limit is the procedure time that averages 231 +/- 48 min., approximately 40% longer than two needle procedures.

Comparison of two filter combinations for low-density lipoprotein apheresis by membrane differential filtration: a prospective crossover controlled clinical study

Membrane differential filtration is an accepted procedure for the extracorporeal removal of low-density lipoprotein (LDL). Reduction rates largely depend on the nature of the membranes and are ideally evaluated in a crossover study design. Four patients who had been treated by LDL apheresis for at least 6 months were included. Six consecutive weekly sessions (40 ml plasma/kg body weight) were scheduled per system (Plasmacure PS06/Evaflux Eval 5A [Kuraray] versus Plasmaflo OP05W/Cascadeflo AC1770 [Asahi]). Laboratory measurements indicated reductions of plasma concentrations for fibrinogen (37% [Kuraray] versus 44% [Asahi]), IgG (15% versus 20%), IgA (24% versus 28%), IgM (63% versus 53%), and total protein (11% versus 16%). Total cholesterol was eliminated by 52% versus 49%, LDL by 67% versus 66%, triglycerides by 56% versus 41%, and high-density lipoprotein by 10% versus 20%. Three therapies employing the Asahi filter combination were terminated prematurely due to saturation of the plasma fractionator. In conclusion, despite similar physical properties, the membranes differ significantly concerning selectivity and sensitivity to saturation.

A high selectivity cascade filtration technique for LDL-cholesterol and Lp(a) removal

This work proposes an improvement of the cascade filtration technique in the treatment of familial hypercholesterolemia. A model of the whole process permitted the definition of the parameters that could influence the selectivity of the fractionation: the pore size, the sieving coefficients of both fractionation and plasmapheresis membrane, and the final retentate flow rate. In vivo studies have shown that the dead-end mode for the secondary filter was not always practical because of severe membrane plugging except when a pulsatile pump was included in the extracorporeal circuit. This pump generated hydrodynamic instabilities which decreased membrane fouling and retarded the build up of the polarization concentration layer. Optimization of these specific operating conditions permitted increase in the selectivity index from 1.15 to 2.24. The performances of cascade filtration were then comparable to those of adsorption on dextran sulfate columns.

Effectiveness of cascade filtration plasmapheresis in two patients affected by familial hypercholesterolemia

Hypercholesterolemia has been recognised as a primary risk factor for coronary heart disease. Reduction of plasma levels of total and LDL cholesterol has been shown to decrease coronary atherosclerosis. Plasmapheresis represents an useful non-pharmacological tool to treat severe hypercholesterolemias. We have evaluated the effectiveness of a system of plasmapheresis using a cascade filtration method in two young male subjects (aged 16 and 26 years) with homozygous familial hypercholesterolemia. Both showed severe coronary atherosclerosis as determined by angiography. Procedures were performed at intervals of 7 days in each case. We observed a mean reduction of plasma levels of total cholesterol of 59.5% (range 31.0-75.5%); LDL-cholesterol, 61.6% (range 32.6-77.1%); triglycerides, 48.1%; HDL-cholesterol, 31.1%; apo A-I, 30.8%; and apo B, 57.6%. We also noted a reduction of other parameters, such as fibrinogen (49.9%) and Lp(a) (59.9%). At the end of each procedure about 8 g of cholesterol was removed from the total body pool. A decrease of total proteins (26.9%) and albumin (19.6%) was also observed, but this was completely restored before the next apheresis (1 week). These data show the effectiveness of the removal of LDL in a cascade filtration system, which obtains results not very different from other more selective methods. The lack of selectivity is not much of a problem, since it also reduces other risk factors such as Lp(a) and fibrinogen.