Left ventricular assist system recipients exposed to bovine thrombin preparations have a higher frequency of antiphospholipid antibodies than nonexposed recipients.

After left ventricular assist system (LVAS) placement, recipients often develop antiphospholipid antibodies (aPL) that are associated with thrombosis. Fibrin glue containing a bovine thrombin preparation is used routinely in LVAS placement surgery. We investigated whether exposure to the thrombin preparation is responsible for stimulating aPL development in LVAS recipients. Pre-LVAS and weekly post-LVAS sera from six fibrin glue-exposed LVAS recipients and five nonexposed recipients were tested by enzyme-linked immunosorbent assay for IgG, IgA, and IgM anti-phosphatidylserine (aPS), anticardiolipin (aCL), anti-phosphatidylethanolamine (aPE), and anti-phosphatidylcholine (aPC). Fibrin glue exposed recipients developed a significantly greater number of aPL than the nonexposed recipients (24 vs. 8; p = 0.0069). In particular, a higher frequency of IgG aCL (6/6 vs. 1/5; p = 0.015) and IgG aPE (4/6 vs. 0/5; p = 0.045) were noted. Exposure to the bovine thrombin component of fibrin glue seems to stimulate aPL development in LVAS recipients.

Risk of early renal allograft failure is increased for patients with antiphospholipid antibodies.

Renal allograft thrombosis can cause transplant failure. Because antiphospholipid antibodies (aPA) are associated with thrombosis, we investigated pretransplant sera from patients with early renal allograft failure to determine if aPA were present. Fifty-six final cross-match (FxM) sera from patients whose transplant failed within 16 days were compared to FxM sera from the next sequential transplant patients. The sera were tested for IgG, IgM, and IgA antibodies to cardiolipin, phosphatidylserine, and phosphatidylethanolamine. aPA were identified in 57% of FxM sera from patients with early non-function versus 35% of FxM sera from patients with functioning grafts (P = 0.02). Historical sera from 11 aPA-positive patients contained aPA up to 18 months prior to transplantation. Since aPA were present in historical sera, testing for aPA can identify certain patients at risk for early allograft failure. The involvement of aPA in early allograft loss is supported by studies demonstrating aPA recovery from an explanted failed transplant.

Immunochemical analysis of polyspecific antibodies in patients exposed to bovine fibrin sealant.

BACKGROUND: Patients exposed to bovine thrombin preparations in fibrin sealant often develop antibodies to bovine coagulation proteins, which cause significant bleeding by cross-reacting with human homologues. Recipients of our left ventricular assist system (LVAS) routinely are exposed to fibrin sealant; therefore, we determined whether they developed antibodies. METHODS: We compared sera from 6 LVAS recipients exposed to fibrin sealant (THROMBOGEN, Johnson & Johnson, Arlington, TX ) during LVAS placement to that of 5 nonexposed LVAS recipients. Pre-LVAS and weekly post-LVAS sera were tested for immunoglobulin (Ig)G, IgA, and IgM reactivity to THROMBOGEN by enzyme-linked immunosorbent assay. Peak IgG and IgA reactive sera were characterized by immunoblotting. RESULTS: All patients exposed to THROMBOGEN developed antibodies: 5 developed IgG, 4 IgA, and 3 IgM. In contrast, nonexposed patients did not develop antibodies. Only some antibody reactivity was contributed by antithrombin or antifactor V antibodies. Silver stain sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses of THROMBOGEN showed more than 18 bands, many of which were recognized in Western blot by positive patient sera. CONCLUSIONS: We found both IgG and IgA polyspecific antibody responses in patients exposed to bovine thrombin preparations.

Changes in platelet activation associated with left ventricular assist system placement.

BACKGROUND: Thromboembolic and hemorrhagic complications are common in patients after left ventricular assist system (LVAS) placement. Platelet physiology may be involved in these complications. METHODS: Using flow cytometry, expression of CD62P and CD63 were analyzed as markers of platelet activation. Binding of annexin V was analyzed to determine platelet membrane asymmetry. Results from two patients who received a Novacor LVAS as a bridge to transplantation are reported. RESULTS: Patients' platelets showed increased CD62P and CD63 expression, yet annexin V binding was not increased. They also revealed suppression of thrombin activation following LVAS placement, which approached normal after transplantation. Heparin suppressed thrombin activation, whereas aspirin or dipyridamole did not. Suppression was attenuated by protamine sulfate and heparinase. CONCLUSIONS: Following LVAS placement, resting platelets demonstrate increased expression of activation markers.

Immunohistochemical analysis of vascular prostheses implanted with the left ventricular assist system.

BACKGROUND: Dacron vascular prostheses are associated with thromboembolic complications and inflammatory responses; impregnation with bovine collagen reportedly stimulates additional inflammatory/immunologic complications. The Novacor (Baxter Healthcare Corp., Oakland, CA, USA) left ventricular assist system uses Dacron inflow and collagen-impregnated Dacron outflow prostheses. METHODS: Explanted inflow and outflow prostheses were evaluated for inflammatory/immunologic, hemostatic, anticoagulant, and fibrinolytic pathways. Non-implanted prostheses immersed in whole blood or plasma were used as controls. RESULTS: Immunoglobulins and complement components were observed in all prostheses with activated macrophages being present only in implanted prostheses. Antithrombin III was observed in all prostheses whereas fibrin, tissue plasminogen activator, and alpha-2 plasmin inhibitor were present only in implanted prostheses. Endothelial and smooth muscle cells associated with vascular structures containing collagen type IV and laminin were observed solely in implanted prostheses. CONCLUSION: An inflammatory response occurs and key components of hemostatic, anticoagulant, and fibrinolytic pathways are present within implanted prostheses. These processes are accompanied by endothelial and smooth muscle cell infiltration which appear to lay the foundation for neovessel development.

Increased incidence of antiphospholipid antibodies in left ventricular assist system recipients.

BACKGROUND: Antiphospholipid antibodies are associated with thrombosis. Because thromboembolic complications are often observed in recipients of a left ventricular assist system, we questioned if antiphospholipid antibodies were present in these patients. We report results from 10 patients who received a Novacor left ventricular assist system. METHODS: Serum samples were collected before left ventricular assist system placement and weekly thereafter until discharge after cardiac transplantation. Samples were tested for IgG, IgA, and IgM antiphosphatidylserine, anticardiolipin, and antiphosphatidylethanolamine using an enzyme-linked immunosorbent assay. RESULTS: Development of phospholipid-binding plasma protein-dependent antiphospholipid antibodies was observed in 9 of the 10 patients. Before placement of the assist system, 3 patients had IgG antiphospholipid antibodies, and 9 were positive after placement. None had IgA antiphospholipid antibodies before placement, whereas 5 seroconverted for IgA after placement. One patient had IgM antiphospholipid antibodies before placement, and 1 additional patient became positive after placement. In patients with a preexisting antibody, increased titers and additional specificities developed subsequent to placement. CONCLUSIONS: All but 1 patient showed development of phospholipid-binding plasma protein-dependent antiphospholipid antibodies after left ventricular assist system placement.

The pre-conditioning incidence of antiphospholipid antibodies is not significantly increased in patients with bone marrow transplant-related organ dysfunction.

Hepatic dysfunction resulting from hepatic veno-occlusive disease (VOD) is a common complication of bone marrow transplantation (BMT). Some investigators believe that hepatic dysfunction, along with pulmonary and central nervous system (CNS) dysfunction, is part of a systemic disorder called multiple organ dysfunction syndrome (MODS). Endothelial damage by pretransplant chemo-radiation and activation of hemostasis are considered early events in the development of hepatic VOD. The pathological mechanism leading to fibrous obliteration of hepatic vessels may also take place in pulmonary and CNS vessels. Since antiphospholipid antibodies (aPA) are associated with venous and arterial thrombosis, which can lead to vessel occlusion, we asked if the incidence of aPA before conditioning was greater in patients who developed MODS following BMT. Samples drawn before pretransplant chemo-radiation from 57 patients who subsequently developed MODS and 55 control patients who did not develop MODS were studied blindly for aPA by ELISA. The number of aPA-positive patients who developed MODS (10/57), compared to the number of aPA-positive patient controls who did not develop MODS (7/55) was not statistically significant (P = 0.48). Our data indicate that the incidence of aPA before conditioning was not greater in patients who developed MODS, including hepatic VOD, following BMT.