Monitoring of coagulation factor therapy in patients with von Willebrand disease type 3 using a microchip flow chamber system

2017 ◽  
Vol 117 (01) ◽  
pp. 75-85 ◽  
Author(s):  
Margareta Holmström ◽  
David E. Schmidt ◽  
Kazuya Hosokawa ◽  
Margareta Blombäck ◽  
Paul Hjemdahl ◽  
...  
Keyword(s):  
Whole Blood ◽  
Thrombus Formation ◽  
Flow Chamber ◽  
Von Willebrand Disease ◽  
High Shear ◽  
Fviii Activity ◽  
Concentrate Treatment ◽  
Type 3 ◽  
Von Willebrand ◽  
Low Shear

SummaryPatients with type 3 von Willebrand disease (VWD-3) have no measurable levels of VW factor (VWF) and usually require treatment with VWF-FVIII concentrate to prevent and/or stop bleeding. Even though the patients are treated prophylactically, they may experience bleeding symptoms. The aim of this study was to evaluate the effect of VWF-FVIII concentrate treatment in VWD-3 patients with the Total Thrombus Analysis System (T-TAS®), which measures thrombus formation under flow conditions. Coagulation profiles of 10 VWD-3 patients were analysed using T-TAS before and 30 minutes after VWF-FVIII concentrate (Haemate®) injection. Results were compared to VWF- and FVIII activity in plasma, and results with thromboelastometry and ris-tocetin-activated platelet impedance aggregometry (Multiplate®) in whole blood. For comparison, 10 healthy controls were also analysed with T-TAS. A median dose of 27 (range 15–35) IU/kg of VWF-FVIII concentrate increased VWF- and FVIII activity as expected. T-TAS thrombus formation was enhanced when a tissue factor/collagen-coated flow chamber was used at low shear, but treatment effects at high shear using a collagen-coated flow chamber were minimal. Whole blood coagulation assessed by thromboelastometry was normal and did not change (p > 0.05) but ristocetin-induced platelet aggregation improved (p < 0.001). In conclusion, T-TAS detects effects of VWF-FVIII concentrate treatment on coagulation-dependent thrombus formation at low shear, but minor effects are observed on platelet-dependent thrombus formation at high shear. The poor prediction of bleeding by conventional laboratory monitoring in VWD-3 patients might be related to insufficient restoration of platelet-dependent thrombus formation.

scholarly journals Distinct Localization of Coagulation Factor VIII, Von Willebrand Factor and Factor VIIIa-Mimetic Bispecific Antibody Contributing to Thrombus Formation Under Whole Blood Flow Conditions

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1483-1483
Author(s):  
Yasuaki Shida ◽  
Keiji Nogami ◽  
Hiroaki Minami ◽  
Hiroaki Yaoi ◽  
Tomoko Matsumoto ◽  
...  
Keyword(s):  
Shear Flow ◽  
Research Funding ◽  
Hemophilia A ◽  
Thrombus Formation ◽  
Flow Chamber ◽  
High Shear ◽  
Flow Conditions ◽  
Von Willebrand ◽  
Low Shear

Abstract Background Factor VIII (FVIII) is an essential factor for coagulation system in the intrinsic pathway. Due to the short survival of FVIII in the plasma circulation, it requires von Willebrand factor (VWF) as a carrier protein to maintain the optimal level for hemostasis. VWF also plays an important role in primary hemostasis by bridging platelets to exposed subendothelial collagens, especially under high shear flow environment. Since VWF carries FVIII, it is conceivable that VWF takes FVIII to the sites of vascular injury. However, the role of FVIII at the local sites under flow conditions is not fully understood despite of the fact that increased level of FVIII is associated with the risk of venous thrombosis and the deficiency of FVIII is the pathology of the bleeding disorder, hemophilia A. The treatment of hemophilia A largely depends on the infusion of FVIII concentrates, which is often complicated by the development of the inhibitor. Recently, bispecific antibody（ACE910）that mimics the role of FVIIIa by recognizing FIXa and FX has been developed and is currently under clinical trial. This antibody theoretically works regardless of the presence of devastating inhibitors against FVIII. Furthermore, it could also improve the clinical outcome of the other bleeding disorders, such as von Willebrand disease (VWD). Aim To analyze the role of FVIII and VWF, and impact of ACE910 at the sites of vascular injury under various shear conditions, we have developed the flow-mediated thrombosis model using flow chamber system. Method Whole blood obtained from healthy donors, hemophilia A and VWD patients were perfused into the collagen coated flow chamber under high (2,500s-1) or low shear (50s-1) flow conditions with/without FVIII concentrate, FVIII/VWF concentrate and ACE910. Formed thrombus was fixed and immunostaining was performed with phalloidin (Platelet), anti-FVIII antibody (FVIII) and anti-thrombin antibody (Thrombin). For the detection of ACE910, anti-human IgG or anti-ACE antibody (rAQ8 or rAJ540) were used. Size of thrombi and distribution of platelet, FVIII, thrombin and ACE910 were analyzed. Result 1) Under high shear flow, thrombus formation of VWD blood was significantly impaired while blood from Hemophilia A demonstrated nearly normal thrombus formation. Addition of FVIII/VWF but not FVIII concentrate to the blood of these patients rescued the impaired thrombus formation. ACE910 enhanced the thrombus formation of blood from both VWD and hemophilia A. Under low shear flow, blood from both hemophilia A and VWD demonstrated decreased thrombus formation. FVIII, FVIII/VWF concentrates and ACE910 improved the size of thrombus. 2) Localization of FVIII was evaluated with thrombin as a marker for the activation of coagulation. Platelets and thrombin demonstrated complete co-localization and intensity of thrombin staining was associated with thrombus size. VWF localized mainly outer layer of thrombus and FVIII localized in and around thrombus. At high shear condition, FVIII and VWF mostly existed with platelets. By contrast, FVIII and VWF demonstrated less co-localization with platelets under low shear condition. ACE910 demonstrated similar tendency to FVIII localization although ACE910 did not appear around thrombus. Conclusion We have developed the flow chamber system to evaluate the extent of thrombogenesis under various shear environment. VWF showed dominant role under high shear conditions while FVIII plays a key role under low shear conditions. FVIII, VWF and ACE910 demonstrated distinct localization. Interestingly, the distribution of FVIII was broader than VWF and platelet. FVIII localized to platelets presumably prior to its activation and contributed for the subsequent thrombin generation at local sites. Finally, ACE910 demonstrated consistent enhancement of thrombus formation of blood from both hemophilia A and VWD and, therefore, is prompted for the treatment of these bleeding disorders. Disclosures Shida: Chugai Pharmaceutical Co., Ltd.: Research Funding. Nogami:Chugai Pharmaceutical Co., Ltd.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Minami:Chugai Pharmaceutical Co., Ltd.: Research Funding. Yaoi:Chugai Pharmaceutical Co., Ltd.: Research Funding. Matsumoto:Chugai Pharmaceutical Co., Ltd.: Research Funding. Kitazawa:Chugai Pharmaceutical Co., Ltd.: Employment, Equity Ownership, Patents & Royalties. Hattori:Chugai Pharmaceutical Co., Ltd.: Employment, Equity Ownership, Patents & Royalties. Shima:Chugai Pharmaceutical Co., Ltd.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Usefulness of Whole Blood Thromboelastography for the Diagnosis and Characterisation of Von Willebrand Disease.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2274-2274
Author(s):  
Catherine Lambert ◽  
Cedric R. Hermans
Keyword(s):  
Factor Viii ◽  
Whole Blood ◽  
Alpha Angle ◽  
Von Willebrand Disease ◽  
Factor Viii Deficiency ◽  
Closure Time ◽  
Significant Prolongation ◽  
Type 3 ◽  
Von Willebrand

Abstract Whole blood coagulation tests such as thromboelastography and platelet function analyser (PFA-100) are increasingly used for the investigation of haemostatic disorders. These global tests offer the advantages of a simple use and fast results. Although PFA-100 using the ADP cartridge has been validated as a useful tool to assess primary haemostatic disturbancies and has a high sensitivity to detect Von Willebrand disease (VWD), this test is neither specific for, nor predicitve of, any particular disorder of primary haemostasis. On the other hand, the potential usefulness of thromboelastography for the evaluation of VWD has so far not been investigated. The present study was undertaken in order to determine alterations of the thromboelastogram tracing in patients with VWD and evaluate its usefulness in adjunction to PFA-100 for the diagnosis and characterisation of VWD. Thromboelastographic analysis (Pentafarm RoTEM® ) was performed, as previously described by Sorensen et al. (J Thromb Haemost. 2003 Mar;1(3):551–8), over a 36 months period on all consecutive patients referred for bleeding work-up to the Haemostasis and Thrombosis Unit of the Cliniques universitaires Saint-Luc, Brussels, Belgium. Ninety-three patients fulfilling the diagnosis criteria of VWD were analysed (38 ± 18 year, 29 males-64 females). The distribution of VWD types was as follows: type 1 (59), type 2 (31) with subtypes 2A (12), 2M (17), 2B (2) and type 3 (3). The control population included 43 healthy individuals (24 females, 19 males, mean age: 38 ± 10 yr). For each patient, the following tests were performed: closure time measured by PFA-100 using the ADP cartridge, Von Willlebrand factor antigen (VWF:Ag) and activity (VWF:Ac) (collagen binding assay), factor VIII level (one-stage assay) and RoTEM®. The following parameters of the RoTEM® tracing were analysed: clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF), alpha angle and maximum clot lysis (ML). VWD was associated with a significant prolongation of the CT and the CFT. By contrast, the MCF, the alpha angle and the ML were not significantly different between patients and controls. By multiple regression analysis, the CT and CFT prolongation was found to be influenced only by the reduction of the factor VIII levels. The most important prolongations of the CT and the CFT were found in type 3 VWD reflecting the severe factor VIII deficiency. No significant differences of the RoTEM® parameters were found between type 1, subtypes 2A and 2M, which altogether represent the majority (94%) of the VWD population. CT and CFT prolongation was not correlated with other parameters (closure time, VWF:Ag and VWF:Ac). As expected, the closure time was determined by the level of VWF activity. In conclusion, although we observed a significant prolongation of the CT and the CFT in patients with VWD, RoTEM® appears to be of limited value for the diagnosis and characterization of VWD. Nevertheless, RoTEM® could be used as a screening tool to identify factor VIII deficiency present in a subset of patients with VWD.

Reduced Effect of Aspirin on Thrombus Formation at High Shear and Disturbed Laminar Blood Flow

1996 ◽  
Vol 75 (05) ◽  
pp. 827-832 ◽  
Author(s):  
R Marius Barstad ◽  
Una Ørvim ◽  
Maria J A.G Hamers ◽  
Geir E Tjønnfjord ◽  
Frank R Brosstad ◽  
...  
Keyword(s):  
Blood Flow ◽  
Thrombus Formation ◽  
Secondary Prophylaxis ◽  
Significant Inhibition ◽  
Von Willebrand Disease ◽  
Shear Stresses ◽  
High Shear ◽  
Cross Sectional ◽  
Wall Shear ◽  
Von Willebrand

SummaryAspirin is the most commonly used antithrombotic drug in primary and secondary prophylaxis against cardio- and cerebrovascular disease. In previous studies from our laboratory it was demonstrated that the effect of aspirin on collagen-induced thrombus formation in a parallelplate perfusion device with laminar blood flow is shear rate dependent. Although aspirin did not affect collagen-induced thrombus formation at 650 s-1 (medium sized arteries), a significant inhibition of thrombus formation by approximately 38% at 2,600 s-1 (moderately stenoses in medium sized arteries) was observed. At present we have extended these studies to thrombus formation at the apex of eccentric stenoses in a parallel-plate perfusion chamber device. The stenoses reduced the cross-sectional area of the blood flow channel of the perfusion chambers by 60 or 80%, introducing disturbed laminar flow and apex wall shear rates of 2,600 and 10,500 s-1, respectively. The corresponding wall shear stresses were 80 and 315 dynes/cm2, respectively.Aspirin reduced the platelet thrombus volume at the 60% stenosis by 45% (p <0.03), and the fibrin deposition by 70% (p <0.004). However, none of these parameters were affected by aspirin at the 80% stenosis. These observations may at least partly explain why aspirin has a limited clinical effect in preventing arterial thrombus formation in atherosclerotic vessels at high shear and disturbed blood flow. In contrast, thrombus formation in blood from one patient with Glanzmann’s thrombasthenia and two patients with von Willebrand disease subtype 2M was almost abolished at this blood flow condition. Thus, blocking the function of either von Willebrand factor or glycoprotein IIb/IIIa may represent better antithrombotic approaches for such critical events than blocking the prostaglandin metabolism by aspirin. The lack of effect of aspirin on thrombus formation at the 80% stenosis may reflect shear-induced platelet activation at the stenosis inlet region, since shear-induced platelet aggregation in rotational viscometers is not affected by aspirin at shear stresses exceeding 100 dynes/cm2.

Recombinant Human Von Willebrand Factor (rhVWF): First-In-Human Study Evaluating Pharmacokinetics, Demonstrating Safety and Tolerability In Type 3 Von Willebrand Disease

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 237-237 ◽  
Author(s):  
Tobias Suiter ◽  
Michael Laffan ◽  
Pier M. Mannucci ◽  
Christine L. Kempton ◽  
Edward H Romond ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Von Willebrand Factor ◽  
Phase 1 ◽  
Von Willebrand Disease ◽  
Fviii Activity ◽  
Post Infusion ◽  
Type 3 ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Abstract 237 Von Willebrand Disease (VWD) is an inherited rare bleeding disorder caused by a deficiency of von Willebrand factor (VWF). VWF is the largest soluble multimeric plasma glycoprotein, which facilitates platelet aggregation and stabilizes FVIII in the circulation. Patients with type 3 disease display severe hemorrhagic symptoms, mainly in mucosal tissues, muscle and joints. Replacement of VWF stabilizes endogenous FVIII to hemostatic levels within hours. Commercially available VWF/FVIII concentrates are plasma-derived (pd) and subject to limitations such as donor dependency, risk of blood-borne pathogen transmission, lack of high molecular weight VWF multimers, and variation in multimer composition. A novel recombinant human VWF (rhVWF) has been developed using a plasma-free method, which represents the largest protein ever produced using recombinant technology. Safety, tolerability and pharmacokinetics of the rhVWF combined at a fixed ratio with rFVIII were investigated in a Phase 1 multicenter, international clinical study in 31 patients with type 3 VWD and severe type 1 VWD. Four concentrations of rhVWF (2, 7.5, 20 and 50 IU VWF:RCo/kg) were administered in a dose-escalating manner in separate cohorts. rhVWF was well tolerated, and no thrombotic events, VWF inhibitors or other serious adverse reactions were observed. Pharmacokinetics of rhVWF/rhFVIII (50 IU VWF:RCo/kg and 38.5 IU FVIII/kg) compared with pdVWF/pdFVIII (50 IU VWF:RCo/kg and 21 IU/kg FVIII/kg) were evaluated in a sub-group of 8/31 patients using a randomized, crossover design (8-day minimum washout period). Interim data in 8 subjects show a higher degree of secondary FVIII activity with rhVWF/rhFVIII compared to pdVWF/pdFVIII (see Figure 1) that is not solely due the difference in the rhVVF:FVIII infusion ratio (1.3:1 rhVWF/rhFVIII vs. approximately 2:1 pdVWF/pdFVIII). The pharmacokinetics of the rhVWF:RCo and pdVWF:RCo were comparable and were also reflected in the VWF:Ag and collagen binding activity. Evidence is also provided for the in vivo cleavage of the ultra-high molecular weight multimers of rhVWF by endogenous ADAMTS13. In summary, interim data from the ongoing Phase 1 study, demonstrate that rhVWF is safe and well tolerated, has VWF:RCo pharmacokinetics that are comparable to pdVWF and enhances stabilization of endogenous FVIII. Multiple doses of rhVWF/rhFVIII would be expected to have beneficial effects in major surgery and severe mucosal bleeding events. These data would also support the treatment concept to administer rhVWF alone once a therapeutic baseline level of endogenous FVIII is achieved (after 1–2 doses).Figure 1:Preliminary PK data from 8 subjects post-infusion of either rhVWF/rhFVIII or pdVWF/pdFVIII. Endogenous FVIII activity reached a plateau after 6 hours and remained stable for at least 30 hours. FVIII was still elevated well above baseline at 96 hoursFigure 1:. Preliminary PK data from 8 subjects post-infusion of either rhVWF/rhFVIII or pdVWF/pdFVIII. Endogenous FVIII activity reached a plateau after 6 hours and remained stable for at least 30 hours. FVIII was still elevated well above baseline at 96 hours Disclosures: Suiter: Baxter BioScience: Employment. Laffan:Baxter BioScience: Consultancy. Mannucci:Baxter BioScience: Consultancy. Kempton:Baxter BioScience: Consultancy. Romond:Baxter BioScience: Consultancy. Shapiro: Baxter BioSci- ence: Consultancy. Birschmann:Baxter BioScience: Consultancy. Gill:Baxter BioScience: Consultancy. Ragni:Baxter BioScience: Consultancy. Turecek:Baxter BioScience: Employment. Ewenstein:Baxter Bioscience: Employment. Baxter BioScience:Baxter BioScience: Employment.

scholarly journals Calin from Hirudo medicinalis, an inhibitor of von Willebrand factor binding to collagen under static and flow conditions

Blood ◽  
1995 ◽  
Vol 85 (3) ◽  
pp. 705-711 ◽  
Author(s):  
J Harsfalvi ◽  
JM Stassen ◽  
MF Hoylaerts ◽  
E Van Houtte ◽  
RT Sawyer ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Adhesion ◽  
Thrombus Formation ◽  
High Shear ◽  
High Shear Stress ◽  
Flow Conditions ◽  
Shear Rates ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Low Shear

Calin from the saliva of the medicinal leech, Hirudo medicinalis, is a potent inhibitor of collagen mediated platelet adhesion and activation. In addition to inhibition of the direct platelet-collagen interaction, we presently demonstrate that binding of von Willebrand to coated collagen can be prevented by Calin, both under static and flow conditions in agreement with the occurrence of binding of Calin to collagen, confirmed by Biospecific Interaction Analysis. To define whether Calin acted by inhibiting the platelet-collagen or the platelet- von Willebrand factor (vWF)-collagen-mediated thrombus formation, platelet adhesion to different types of collagens was studied in a parallel-plate flow chamber perfused with whole blood at different shear rates. Calin dose-dependently prevented platelet adhesion to the different collagens tested both at high- and low-shear stress. The concentration of Calin needed to cause 50% inhibition of platelet adhesion at high-shear stress was some fivefold lower than that needed for inhibition of vWF-binding under similar conditions, implying that at high-shear stress, the effect of Calin on the direct platelet- collagen interactions, suffices to prevent thrombus formation. Platelet adhesion to extracellular matrix (ECM) of cultured human umbilical vein endothelial cells was only partially prevented by Calin, and even less so at a high-shear rather than a low-shear rate, whereas the platelet binding to coated vWF and fibrinogen were minimally affected at both shear rates. Thus, Calin interferes with both the direct platelet- collagen interaction and the vWF-collagen binding. Both effects may contribute to the inhibition of platelet adhesion in flowing conditions, although the former seems to predominate.

Type 3 von Willebrand Disease in Pregnancy: A Systematic Literature Review

2019 ◽  
Author(s):  
Mona M. Makhamreh ◽  
Stephanie L. Kass ◽  
Melissa L. Russo ◽  
Homa Ahmadzia ◽  
Huda B. Al-Kouatly
Keyword(s):  
Pregnant Women ◽  
Bleeding Disorder ◽  
Von Willebrand Disease ◽  
Maternal Characteristics ◽  
Pregnancy And Delivery ◽  
Concentrate Treatment ◽  
Rare Phenotype ◽  
Type 3 ◽  
Von Willebrand ◽  
In Pregnancy

Abstract Objective von Willebrand disease (VWD) is a hereditary bleeding disorder. Type 3 VWD is the most severe and rare phenotype that presents many challenges for management of pregnant women. The aim of this study was to review the maternal characteristics and complications in pregnant women with Type 3 VWD. Study Design A systematic literature search was performed to include all publications that address Type 3 VWD in pregnancy. Results Thirteen studies met the inclusion criteria. There were 28 pregnancies with Type 3 VWD in 17 women. All were diagnosed with Type 3 VWD prior to pregnancy. Concentrate treatment was administered before delivery for 19 pregnancies and postpartum for 26 pregnancies. Eight pregnancies required blood products postpartum. Primary postpartum hemorrhage (PPH) was reported in 48% (10/21) and secondary PPH was reported in 56% (5/9). Secondary PPH occurred between 7 and 22 days. No study reported hysterectomies, intensive care unit admissions, or maternal mortality. All 28 pregnancies resulted in 28 live births at term. Conclusion Our review highlights the maternal outcomes in patients with Type 3 VWD and the different approaches in management during pregnancy and delivery. Despite prior knowledge of this bleeding disorder, PPH was still a significant complication.

Evaluation of the PFA-100® System in the Diagnosis and Therapeutic Monitoring of Patients with von Willebrand Disease

1999 ◽  
Vol 82 (07) ◽  
pp. 35-39 ◽  
Author(s):  
Augusto Federici ◽  
Anna Lecchi ◽  
Barbara Agati ◽  
Rossana Lombardi ◽  
Federica Stabile ◽  
...  
Keyword(s):  
Platelet Function ◽  
Bleeding Time ◽  
Von Willebrand Disease ◽  
Therapeutic Monitoring ◽  
High Shear ◽  
Before And After ◽  
Type 3 ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryWe have evaluated platelet function at high shear with the PFA-100® system in different subtypes of von Willebrand disease (vWD), before and after the intravenous infusions of desmopressin or a factor-VIII/von Willebrand factor (vWF) concentrate. Closure times with the PFA-100® system were determined for both the collagen/ADP and the collagen/epinephrine cartridges in 52 patients with vWD (9 type 1 “platelet normal”, 5 type 1 “platelet-discordant”, 8 type 1 “platelet-low”, 6 type 2A, 9 type 2B, 6 type 2M Vicenza, 6 type 3 and 3 acquired vWD) and 40 controls. Measurements were repeated 1 and 4 h after the i.v. infusion of desmopressin (0.3 μg/Kg) in 26 patients with types 1, type 2M Vicenza or type 2A vWD, or of a factorVIII/vWF concentrate (Alphanate HT, 60 U/Kg) in 4 patients with type 3 vWD. At all time points, vWF plasma levels and the bleeding time (Symplate II) were also determined. Baseline closure times were longer in vWD patients than in controls with both the collagen/ADP and the collagen/ epinephrine cartridges. The sensitivity of the PFA-100® system (88% and 87% with the two cartridges) was higher than that of the bleeding time (65%). Treatment with desmopressin normalized the closure times in patients with type 1 “platelet-normal” or type 2M Vicenza vWD, had no significant effects in patients with type 1 “platelet-low”, type 1 “platelet-discordant” or type 2A vWD. Infusion of a factorVIII/vWF concentrate in patients with type 3 vWD slightly shortened their prolonged closure times. In general, changes in PFA-100® were paralleled by shortenings of the bleeding times and increases in plasma vWF levels. The PFA-100® test reflects vWF-dependent platelet function under high shear stress and could be useful in the diagnosis and therapeutic monitoring of patients with vWD.

Emicizumab improves thrombus formation of type 2A von willebrand disease under high shear condition

Haemophilia ◽  
2021 ◽  
Author(s):  
Hiroaki Yaoi ◽  
Yasuaki Shida ◽  
Takehisa Kitazawa ◽  
Midori Shima ◽  
Keiji Nogami
Keyword(s):  
Thrombus Formation ◽  
Von Willebrand Disease ◽  
High Shear ◽  
Von Willebrand ◽  
Shear Condition

scholarly journals Decreased Platelet Thrombus Size, Due to a Heightened Proteolysis of VWF By ADAMTS13, Is Quickly Restored after Valve Replacement in Aortic Stenosis Patients

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2857-2857
Author(s):  
Hideo Yagi ◽  
Masaki Hayakawa ◽  
Naoko Yamaguchi ◽  
Keigo Yamashita ◽  
Shigeki Taniguchi ◽  
...  
Keyword(s):  
Shear Stress ◽  
Aortic Valve ◽  
Valve Replacement ◽  
Thrombus Formation ◽  
Flow Chamber ◽  
High Shear ◽  
Chamber System ◽  
High Shear Stress ◽  
Platelet Thrombus ◽  
Von Willebrand

Abstract Background: The patients with severe aortic-valve stenosis (AS) are often complicated with bleeding episodes. The association between AS and gastrointestinal bleeding due to angiodysplasia is reported as Heyde's syndrome, which is categorized as one of the acquired von Willebrand disease (AVWD) in cardiovascular disorders. An international survey has shown that Type 2A is the common subtype of AVWD in the patients with AS. AVWD Type 2A is characterized by impaired platelet-dependent VWF function caused by marked decrease or absence of the most hemostatically active HMW-VWFM. In the patients with AS, a significant correlation between the increased high shear stress and loss of HMW-VWFM in vivo. Further, the absence of HMW-VWFM and bleeding tendency are normalized after valve replacement. These results suggest that enhanced proteolysis of von Willebrand factor (VWF) as it passes through the stenotic valve may induce the loss of HMW-VWFM because high shear stress can induce structure changes in VWF, which is sensitive form to the VWF cleaving protease, termed ADAMTS13. Here, we performed investigation of plasma levels of VWF antigen (VWF:Ag), ADAMTS13 activity (ADAMTS13:AC), and platelet thrombus formation in the patients with AS by valve replacement to confirm the pathophysiological mechanism of this rare disease. Patients and Methods: Ten consecutive patients who underwent aortic valve replacement for AS in Nara Medical University Hospital were enrolled in this study. The severity of AS was judged by the American Heart Association guideline. All patients had no bleeding history and received bovine tissue valves replacement followed by administration of warfarin and/or anti-platelet agents for prevention of thrombosis a week after surgery. We collected a series of blood samples from these patients before and day1, 8, 15, 22 after valve replacement. Excluding one patient who developed critical cardiac failure just after valve replacement, 9 patients were eventually evaluated by analyses of VWF:Ag, VWF multimers, ADAMTS13:AC, and mural thrombus formation using flow chamber system. VWF:Ag was measured by sandwich ELISA using a rabbit anti-human VWF polyclonal antiserum. Analysis of VWF multimers was performed according to the method of Ruggeri and Zimmerman. ADAMTS13:AC was measured by a chromogenic ADAMTS13-act-ELISA. Platelet thrombus formation was evaluated by thrombus generation under a high shear stress in a parallel plate flow chamber system. Briefly, whole blood anti-coagulated with argatroban was incubated with the fluorescent dye DiOC6 (1uM), and these samples containing DiOC6 -labeled platelets were perfused for 7 min over a type I collagen-coated glass surface under a high shear rate (1500 s-1). The DiOC6 fluorescence corresponding to the platelets was examined at an excitation wavelength of 488 nm with a barrier filter at 500 nm. The percentage of the area covered by adhering platelets (surface coverage) and each thrombus volume were evaluated. Results: Plasma levels of VWF:Ag before surgery were 78.1 % (median) and those on day 1, 8, 15, 22 after surgery were 130, 224, 155, and 134 %, respectively (Fig 1). Conversely, these levels of ADAMTS13:AC were 50.5, 35.5, 25.5, 25.1, and 30.3 %, respectively (Fig 2). The ratio of VWF:Ag/ADAMTS13:AC at before and day 1, 8, 15, 22 after surgery were 1.6, 4.5, 8.1, 6.1, and 4.1, respectively. In VWF multimer analysis, we found the obvious defect of HMW-VWFM in 7 of 9 patients before surgery, who were diagnosed with severe AS. The remaining two patients had moderate AS with the slight defect of HMW-VWFM. These defects were improved within 14 days after surgery. In platelet thrombus formation, the amount of thrombus volumes significantly increased at day 8, 15, and 22 after compared with before surgery (Fig 3). Conclusion: The dramatic recovery of platelet thrombus formation was observed in the patients with AS by valve replacement. The rapid increment of VWF and normalization of VWFM pattern, together with reduction of ADAMTS13 after valve replacement suggested heightened proteolysis of VWF by ADAMTS13 under high shear stress would be a major cause of this unique bleeding complication. The highest ratio of VWF:Ag/ADAMTS13:AC at day 8 after surgery might imply the necessity of blockade of heightened VWF function with anti-platelet agents. Figure 1 Figure 1. Disclosures Matsumoto: Alfresa Pharma Corporation: Patents & Royalties. Fujimura:Alfresa Pharma Corporation: Patents & Royalties.

scholarly journals Emicizumab Augments Thrombus Formation in Whole Blood from Patients with Hemophilia A under High Shear Flow Conditions

2020 ◽  
Author(s):  
Hiroaki Yaoi ◽  
Yasuaki Shida ◽  
Takehisa Kitazawa ◽  
Midori Shima ◽  
Keiji Nogami
Keyword(s):  
Whole Blood ◽  
Hemophilia A ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Flow Chamber ◽  
High Shear ◽  
Bypassing Agents ◽  
High Doses ◽  
Recombinant Fviii ◽  
Activated Prothrombin Complex Concentrates

Abstract Background Emicizumab is a bispecific antibody to factor (F) IXa and FX that mimics the FVIIIa cofactor function. Emicizumab prophylaxis markedly decreases bleeding episodes in patients with hemophilia A (PwHAs), irrespective of the presence of FVIII inhibitors. However, thrombotic microangiopathy (TMA) was reported when repeated high doses of activated prothrombin complex concentrates (aPCC) were concomitantly used with emicizumab. Although bypassing agents (BPAs) are vital in the hemostatic treatment for PwHAs with inhibitors, the mechanism of emicizumab-related TMA remains unclear. Aim To assess the risk of excessive thrombus formation associated with BPAs and emicizumab under high shear conditions. Methods Perfusion flow-chamber experiments under high shear conditions were performed using whole blood from PwHAs in the presence of emicizumab without or together with FVIII or BPAs ex vivo. Results Emicizumab (100 μg/mL) added ex vivo to whole blood from PwHAs improved defective thrombus formation in a similar manner to that observed with the addition of recombinant FVIII at the early phase, while FVIII continued to be important at the later stages. aPCC (1.2 U/mL equivalent to 100 U/kg) or recombinant FVIIa (1.1 µg/mL; equivalent to 90 µg/kg) together with emicizumab further promoted platelet interactions and fibrin formation ex vivo but did not induce excessive thrombus formation. Conclusion Emicizumab enhanced thrombin generation at local sites and improved defective hemostasis in whole blood from PwHAs under high shear conditions. Simple concomitant use of BPAs with emicizumab did not mediate excessive thrombus formation and remains an option for hemostatic management of emicizumab-treated PwHAs with inhibitors.

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