Lipid apheresis: from a heroic treatment to routine clinical practice

The potential role of ischaemia-reperfusion injury in chronic, relapsing diseases such as rheumatoid arthritis, Long COVID, and ME/CFS: evidence, mechanisms, and therapeutic implications

Ischaemia–reperfusion (I–R) injury, initiated via bursts of reactive oxygen species produced during the reoxygenation phase following hypoxia, is well known in a variety of acute circumstances. We argue here that I–R injury also underpins elements of the pathology of a variety of chronic, inflammatory diseases, including rheumatoid arthritis, ME/CFS and, our chief focus and most proximally, Long COVID. Ischaemia may be initiated via fibrin amyloid microclot blockage of capillaries, for instance as exercise is started; reperfusion is a necessary corollary when it finishes. We rehearse the mechanistic evidence for these occurrences here, in terms of their manifestation as oxidative stress, hyperinflammation, mast cell activation, the production of marker metabolites and related activities. Such microclot-based phenomena can explain both the breathlessness/fatigue and the post-exertional malaise that may be observed in these conditions, as well as many other observables. The recognition of these processes implies, mechanistically, that therapeutic benefit is potentially to be had from antioxidants, from anti-inflammatories, from iron chelators, and via suitable, safe fibrinolytics, and/or anti-clotting agents. We review the considerable existing evidence that is consistent with this, and with the biochemical mechanisms involved.

Intraindividual Comparison of the Impact of two Selective Apheresis Methods (DALI and HELP) on the Coagulation System

We performed an intraindividual comparison of the effect on the coagulation system of two selective apheresis procedures: Direct Adsorption of Lipoproteins (DALI) and Heparin-induced Lipoprotein Fibrinogen Precipitation (HELP). Six patients suffering from heterozygous familial hypercholesterolemia have been treated with 2 sessions of each procedure. Anticoagulation was carried out according to usual recommendations. Blood samples were taken before, immediately after and on the second day after the sessions. We assessed global coagulation tests (prothrombin time, activated partial thromboplastin time), fibrinogen, prothrombin fragment F 1 + 2 and a variety of factors (Factors II, V, VII, XIII, IX, X, XI, XII, XIIa; von Willebrand Factor; collagen-binding activity, prekallikrein, high-molecular weight kininogen) and antagonists (antithrombin III, protein S activity, free protein S). In fact, all parameters measured have been influenced by the apheresis treatment. Fibrinogen is lowered more by HELP, which also has a more definite impact on factors belonging to the prothrombin complex (II, VII, X). In contrast, the major effects of the DALI system have been seen on the intrinsic pathway of the coagulation system (IX, XI, prekallikrein, high-molecular-weight kininogen). With both systems, no increases in activated Factor XII or in prothrombin fragment F1 + 2 have been observed. These data provide a solid basis for individual adaptations of anticoagulant doses.

Heparin-Free DALI LDL-Apheresis in Hyperlipidemic Patients: Efficacy, Safety and Biocompatibility

Background and Aim of Study

In routine DALI apheresis - the first technique for direct adsorption of lipoproteins from whole blood - heparin plus citrate (ACD-A) is used as anticoagulation regimen. However, recently several publications have warned of heparin-induced thrombocytopenia as a rare but potentially life-threatening complication of heparin administration (HIT type 2). The aim of the present study was therefore to test the efficacy and biocompatibility of DALI using a heparin-free anticoagulation regimen consisting exclusively of citrate.

Methods

Four symptomatic hypercholesterolemic patients on regular DALI apheresis were switched to the heparin-free protocol for two sessions each. Two of the patients were on oral anticoagulation using phenprocoumon. In the weekly sessions, 1.3 patient blood volumes were processed at a blood flow rate of 60 ml/min using ACD-A at a ratio of 1:20 (v/v) during adsorber priming and the session.

Results

Clinically, all sessions were essentially uneventful. Uncorrected lipoprotein reductions amounted to 65% for LDL-C, 62% for Lp(a), 53% for VLDL-C, 24% for HDL-C, 17% for triglycerides and 19% for fibrinogen. Cell counts remained virtually constant. No signs of hemolysis or clotting could be detected. Thromboplastin time (Quick) was slightly prolonged and partial thromboplastin time (PTT) moderately elevated in all patients. In constrast, whole blood coagulation time acc. to Lee-White and activated clotting times were increased only in orally anticoagulated patients. Biocompatibility in terms of complement, leukocyte and thrombocyte activation was excellent. Bradykinin activation was moderate peaking at 3038 pg/ml in the efferent line. Systemic thrombin-antithrombin complex (TAT) reflected perfect anticoagulation in orally anticoagulated patients and adequate anticoagulation in the patients without phenprocoumon.

Conclusion

In this pilot study, heparin-free DALI apheresis was safe and effective and may thus be performed in LDL-apheresis dependent patients who suffer from heparin intolerance.

Treatment of Hyperlipidemia With a Modified Low Density Lipoprotein Apheresis System With Dextran Sulfate

Many low density lipoprotein (LDL) apheresis systems have been applied to patients with hyperlipidemia, but these systems usually work on the basis of complicated equipment and the cost of treatment is expensive. In order to achieve effective treatment of hyperlipidemia at a lower cost, we developed a new LDL apheresis system with dextran sulfate (LAS-DS). In this study, 50 patients with hyperlipidemia were treated 120 times with the new LAS-DS. In each treatment, 600 +/- 100 mL of plasma (equal to approximately 25% of the total plasma of patients) was collected by apheresis, and DS solution and calcium chloride solution were added into the collected plasma as LDL absorber and catalyzer, respectively. DS selectively binds LDL cholesterol (LDL-C) under the catalysis of calcium ion and the LDL-C-DS complex is removed by centrifugation. The treated plasma was transfused back into the patients and the excessive calcium in the plasma was removed by the cation exchange column integrated in the transfusion set. After treatment with our new system, the acute mean LDL-C reduction was 97% in the apheresis plasma of hyperlipidemia patients. The corresponding reduction was 55.2% and 69.4% for total cholesterol and total triglyceride. There were insignificant reductions of high density lipoprotein cholesterol (HDL-C) and albumin. The new LDL apheresis system with DS that we developed is very simple to operate without relying on complicated equipment, and it can achieve significant clinical results at a much lower cost compared with existing systems. Based on this study we think the new system can provide a safe, effective and much cheaper means for the treatment of hyperlipidemia patients.

Hypercholesterolemia and LDL apheresis

Several trials have assessed the link between low-density lipoprotein cholesterol (LDL) and the development of coronary heart disease (CHD). LDL apheresis provides an effective role in treating patients with familial hypercholesterolemia (FH) and in preventing the progression of coronary artery disease (CAD). Five different techniques of LDL apheresis are in current use: immunoadsorption (IMA), dextran sulphate-cellulose adsorption (DSA), heparin extracorporeal LDL precipitation system (HELP), double filtration plasmapheresis (DFPP) or lipidfiltration and direct adsorption of lipoprotein using hemoperfusion (DALI). All methods are efficient,but their cost restricts LDL apheresis to the treatment of FH. Indications could include other diseases, but controlled trials are still lacking.

LDL apheresis

Low density lipoprotein (LDL) apheresis provides a safe and effective means of treating patients with homozygous familial hypercholesterolaemia (FH). It also has a role in preventing the progression of coronary artery disease in heterozygotes and others with severe dyslipidaemia who are refractory to or intolerant of high doses of lipid-lowering drugs. Established methods involve either adsorption of apolipoprotein B-containing lipoproteins by affinity columns containing anti-apolipoprotein B antibodies or dextran sulphate, or their precipitation at low pH by heparin, in each instance after first separating plasma from blood cells with a cell separator. The most recently developed method enables lipoproteins to be adsorbed directly from whole blood, using polyacrylate columns. All 4 methods have proved to be similarly efficient when used weekly or biweekly to lower LDL cholesterol and Lp(a) without unduly reducing HDL cholesterol. Economic constraints restrict the use of LDL apheresis to the treatment of potentially fatal disorders such as FH, where there is clear evidence of benefit compared with conventional therapy. Widening the indications to include the treatment of other dyslipidaemic disorders such as steroid-resistant nephrotic syndrome, post-transplant donor vessel disease, stroke and prevention of re-stenosis after coronary angioplasty requires evidence from controlled trials that is currently lacking.

Improvement of hemorheology by DALI apheresis: acute effects on plasma viscosity and erythrocyte aggregation in hypercholesterolemic patients

Plasma viscosity (PV) and erythrocyte aggregation (EA) are determinants of microcirculation, especially under the compromised hemodynamic conditions resulting from atherosclerosis. Direct adsorption of lipoproteins (DALI) apheresis is the first method for direct adsorption of lipoproteins; it drastically reduces low-density lipoprotein (LDL)-cholesterol and lipoprotein (a) (Lp[a]), and may therefore improve PV and EA. The current study was performed to test the effect of DALI on hemorheology. Six hypercholesterolemic patients who had been on regular LDL apheresis for at least several months were treated on a weekly or biweekly basis, on average 5 times each by DALI. Before and after each session, PV was measured by a capillary tube plasma viscosimeter and EA by rotational aggregometry. Single DALI sessions (n = 31) acutely decreased PV from 1.18 +/- 0.04 to 1.06 +/- 0.3 mPa (-10%) while EA improved from 22.8 +/- 4.4 to 13.3 +/- 4.5 (arbitrary units) (-42%). LDL-cholesterol, Lp(a), and very-low-density lipoprotein (VLDL)-cholesterol were effectively reduced while the decrease of triglycerides and fibrinogen was only moderate. DALI apheresis exerted an acute positive effect on blood hemorheology which may have beneficial effects on microcirculation. This hypothesis is in accordance with the clinical observation that in some patients, improvement of angina and/or exercise tolerance can be observed after only a few DALI sessions where changes of coronary stenoses cannot be expected yet.

DALI apheresis in hyperlipidemic patients: biocompatibility, efficacy, and selectivity of direct adsorption of lipoproteins from whole blood

Recently, the first apheresis technique for direct adsorption of low-density lipoprotein (LDL) and lipoprotein(a) [Lp(a)] from whole blood (DALI) was developed that does not require a prior plasma separation. That markedly simplifies the extracorporeal circuit. The aim of the present study was to test the acute biocompatibility, efficacy, and selectivity of DALI apheresis. In a prospective clinical study, 6 hypercholesterolemic patients suffering from angiographically proven atherosclerosis were treated 4 times each by DALI. 1.3 patient blood volumes were treated per session at blood flow rates of 60-80 ml/min using 750 or 1,000 ml of polyacrylate/polyacrylamide adsorber gel. The anticoagulation consisted of an initial heparin bolus followed by a citrate infusion. The sessions were clinically essentially uneventful. Mean corrected reductions of lipoproteins amounted to 65% for LDL-cholesterol, 54% for Lp(a), 28% for triglycerides, 1% for HDL-cholesterol, and 8% for fibrinogen. The selectivity of lipoprotein removal was high. Cell counts remained virtually unchanged and no signs of hemolysis or clotting were detected. Cell activation parameters elastase, beta-thromboglobulin, interleukin-1beta, and IL-6 showed no significant increase. Complement activation was negligible. There was significant, but clinically asymptomatic, bradykinin activation in the adsorber with mean maxima of 12,000 pg/ml in the efferent line at 1,000 ml of treated blood volume. In conclusion, DALI proved to be safe, selective, and efficient for the adsorption of LDL-C and Lp(a), which simplifies substantially the extracorporeal therapy in hypercholesterolemic patients.

LDL hemoperfusion--a new procedure for LDL apheresis: biocompatibility results from a first pilot study in hypercholesterolemic atherosclerosis patients

Current lipid apheresis techniques can remove atherogenic lipoproteins only from plasma. The initial mandatory separation of plasma and blood cells renders the extracorporeal circuit complex. We recently described the first clinical application of a new lipid adsorber that adsorbs low-density lipoprotein (LDL) and lipoprotein (a) (Lp[a]) directly from whole blood. In continuation of our work, this paper describes the clinical biocompatibility of this new LDL hemoperfusion system. In a 2 center phase II clinical trial, 12 hypercholesterolemic patients suffering from overt coronary or peripheral artery disease were treated once with LDL hemoperfusion. The new LDL adsorber (DALI, Fresenius, St. Wendel, Germany) contained 480 ml of polyacrylate coated polyacrylamide gel. The anticoagulation protocol consisted of an initial heparin bolus followed by an acid citrate dextrose-A (ACD-A) infusion during the treatment. One patient blood volume was treated per session. All sessions were clinically uneventful. No signs of hemolysis or extracorporeal clot formation could be detected, and cell counts remained virtually constant. In a subgroup of patients (n = 4-6), further biocompatibility parameters were studied. Activation of leukocytes (elastase release), thrombocytes (beta-thromboglobulin [beta-TG] extrusion), and monocytes (interleukin (IL)-1beta and IL-6) were minimal. Complement activation (C3a and C5a generation) was negligible. The chosen anticoagulation protocol was both safe (constant ionized calcium levels) and effective (low thrombin-antithrombin formation). In summary, within the scope of a first pilot study, this new LDL hemoperfusion procedure combined the features of excellent clinical tolerance, good biocompatibility, and ease of handling. Phase III clinical trials will have to show whether these encouraging preliminary results can be corroborated in a larger patient population.

Spin doctors: new innovations for centrifugal apheresis

The preparation of plasma from blood has a long history dating back to the early 1900s when the concept of blood washing replaced the traditional blood letting. Over the next 57 years landmark discoveries such as centrifugal and membrane filtration systems led to different and rapid plasma, solute, and cell separation. These were not singular events but rather events influenced by the converging chemical, physiological, and engineering advances that have characterized the latter half of the 20th century. These events have led to entire new fields of biomedical research. The biotechnology for on-line plasma separation and plasma treatment has opened a new era, expanding the application of extracorporeal technology to modern therapeutic medicine. The association of biochemical or cellular abnormalities with various disease states provides the rationale for therapeutic plasma exchange (the removal of large amounts of patient's plasma, alone or with replacement with crystalloid) and therapeutic cytopheresis (removal of cellular elements). The purpose of this review is to provide a historical picture of the innovative ideas of the spin doctors and their devices, which predate the centrifugal blood and cell separators commonplace to any hospital or blood bank worldwide. The emphasis is to define the historical events and their impacts on the development of centrifugal devices and apheresis technologies.