Arterial and venous thrombosis in patients with von Willebrand’s disease: A critical review of the literature

Outcomes Following Total Hip Arthroplasty in Patients Who Have Von Willebrand Disease Depend on Postoperative Anticoagulation

BACKGROUND

Von Willebrand disease (VWD) is the most common congenital bleeding disorder. This autosomal dominant condition arises from quantitative or qualitative defects of Von Willebrand factor. To our knowledge, this study leveraged a national database to characterize the largest VWD cohort of total hip arthroplasty (THA) patients to date, assessing 90-day postoperative adverse events and 5-year revision-free survival.

METHODS

Adult patients who underwent primary THA for osteoarthritis were identified from January 2010 to October 2021 in a nationwide database. Patients who had and did not have VWD were matched (4:1) on age, sex, and Elixhauser Comorbidity Index and compared with multivariable logistic regression. Patients were then categorized based upon venous thromboembolism (VTE) chemoprophylaxis prescription patterns to compare bleeding and thrombotic adverse events.

RESULTS

Of 544,851 THA patients, VWD was identified in 309 patients (0.06%). The matched cohorts contained 1,221 patients who did not have VWD and 306 patients who have VWD. On multivariable analysis, VWD patients had increased odds of 90-day VTE (odds ratio [OR] = 1.86) and hematoma (OR = 3.40) (P < .05 for all). No difference in 5-year revision-free survival was found. The VWD patients receiving aspirin or no prescriptions had greater odds of VTE (OR = 2.39, P = .048). Those on other chemoprophylaxis agents had greater odds of hematoma (OR = 4.84, P = .006).

CONCLUSIONS

Patients with VWD undergoing THA had increased odds of 90-day VTE if using aspirin or no prescriptions, or hematoma if using other chemoprophylaxis. There is a delicate balancing act of clotting versus bleeding that must be considered in managing such patients, but it was reassuring that no difference in overall 5-year revision-free survival was found.

Congenital Bleeding Disorders and COVID-19-A Systematic Literature Review

Hypercoagulability is a prominent feature of coronavirus disease 2019 (COVID-19) and can lead to fatal consequences. Although the impact of COVID-19 on several disorders is well-established, its effect on congenital bleeding disorders (CBDs) is not well-documented. To address this ambiguity, a systematic review was conducted on the available studies to determine the impact of COVID-19 and vaccination aimed to prevent COVID-19 on patients with CBDs. We performed a systematic literature review using relevant keywords and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol. We conducted our search on the PubMed, Scopus, and Web of Science databases until July 2023. Out of 31 included studies, 12 case series covering 770 patients with CBD and COVID-19 were further analyzed. The majority of the patients had hemophilia A (n = 352, ∼46%) or hemophilia B (n = 74, ∼10%), while the remaining patients had von Willebrand disease (n = 43, 5.6%) or rare bleeding disorders (n = 27, 3.5%). A total of 25 deaths (3.2%) and 22 intensive care unit admissions (2.8%) were recorded. Bleeding complications were reported in the majority of the 12 case series (n = 7, 58.3%) and in most of the case reports (n = 8, ∼57%), while thrombotic complications were only reported in two studies (16.6%). The mortality rate ranged from 0% in five studies (41.6%) to 5.7% and the rate of hospitalization ranged from 0 to 40%. Bleeding complications were reported in a range of 0 to 81%, while the thrombotic complication rate in one study was 6.9%. The mortality rate varied from 0 to 5.7%, and the hospitalization rate ranged from 0 to 40%. Bleeding complications were reported in a range of 0 to 81%, while the rate of thrombotic complications in one study was 6.9%. Vaccination was reported in five case series, which included 821 patients with CBDs with the majority having hemophilia A (n = 479; 67.2%) and hemophilia B (n = 85; ∼12%). The most frequently reported side effects were myalgia (6.5%), flu-like symptoms (4.8%), fever (4.7%), and headache (4%). COVID-19 in patients with CBDs appears to provoke thrombotic complications and bleeding events more frequently, as well as a higher rate of hospitalization, which may be partially due to the increased risk of bleeding events. Although it seems that patients with CBD have lower mortality rates, further studies are necessary to fully understand this, especially considering comorbidities and low number of available studies.

Cerebral sinus venous thrombosis in children with inherited bleeding disorders: A case series

In patients with inherited bleeding disorders, thrombus development poses a challenge in balancing the management of thrombosis and bleeding. Pediatric antithrombotic therapy guidelines do not address the treatment of a thrombus in the setting of a bleeding disorder. We present a case series of four children with inherited bleeding disorders presenting with cerebral sinus venous thrombosis and bleeding, in order to summarize the different therapeutic approaches and outcomes of these patients.

Postpartum hemorrhage in women with von Willebrand disease: Consider other etiologies

OBJECTIVE

Higher rates of postpartum hemorrhage (PPH) have been reported for women with von Willebrand disease (VWD). Comprehensive multidisciplinary care reduces these rates; thus PPH may not be secondary to VWD.

METHODS

We conducted a retrospective review for the period of 2009-2018, including all VWD pregnancies at two tertiary care academic hospitals to determine rates, etiology, and timing of PPH.

RESULTS

A total of 63 women with 80 pregnancies were included. Three women had twin pregnancies. Sixty-six pregnancies (82.5%) involved type 1 VWD; 4 (5.0%), type 2 (unclear subtype); 3 (3.8%) type 2A; 3 (3.8%) type 2B; and 2 (2.5%), type 2M. Median age of patients was 32.9 years (range 19-43 y). Most patients were blood type O (65%), and 33 of 80 preganancies (41.3%) were nulliparous. The mean bleeding assessment score was 8 (range 0-16). Thirty-seven pregnancies (46.3%) received prophylactic hemostatic treatment prior to delivery. Seventy-four percent of pregnancies were delivered vaginally, and 88% received epidural anaesthesia. The majority of pregnancies (78.8%) had von Willebrand factor (VWF) levels assessed during the third trimester, with most (71.3%) achieving VWF levels above 1.00 IU/mL. Four pregnancies (5.2%) were complicated by primary PPH; uterine atony in 2 and placenta previa in 1. Delayed postpartum bleeding occurred in 5 pregnancies (6.3%).

CONCLUSION

Multidisciplinary care of pregnancies with VWD improves outcomes. Rates of primary and delayed PPH in this study are lower than previously described and are similar to those of women without VWD. In women with VWD, uterine etiologies for primary PPH need to be considered, in a manner similar to the assessment of women without VWD, to ensure hemostasis is achieved.

Endothelial Function in Patients With Von Willebrand Disease

In patients with von Willebrand disease (vWD) the interest in age-related comorbidities has grown, because the life expectancy of these patients has increased. The research question of this study was whether patients with vWD show a different endothelial function compared to the general population. A total of 37 patients with type 1 (n = 23), type 2 (n = 10) and type 3 (n = 4) vWD, 14 controls and 38 patients with coronary artery disease (CAD) were included in this study. Five markers of endothelial dysfunction (MOED) were determined. Moreover, the endothelial function was examined using the Itamar Endo-PAT. The reactive hyperemia index (RHI) was calculated from the results. The markers soluble intercellular adhesion molecule-1 (p = 0.171), P-Selectin (p = 0.512), interleukin-6 (p = 0.734) and monocyte chemoattractant protein-1 (p = 0.761) showed higher levels in patients with vWD, but were not significantly different compared to the control group. RHI was impaired in CAD-patients (1.855), whereas vWD patients had mean results of 1.870 and controls 2.112 (p = 0.367). In this study, the endothelial function measurements of patients with von Willebrand disease were not significantly different compared to healthy controls.

Retrospective Assessment of Desmopressin Effectiveness and Safety in Patients With Antiplatelet-Associated Intracranial Hemorrhage

OBJECTIVE

Current international guidelines offer a conditional recommendation to consider a single dose of IV desmopressin (DDAVP) for antiplatelet-associated intracranial hemorrhage based on low-quality evidence. We provide the first comparative assessment analyzing DDAVP effectiveness and safety in antiplatelet-associated intracranial hemorrhage.

DESIGN

Retrospective chart review.

SETTING

Single tertiary care academic medical center.

PATIENTS

Adult patients taking at least one antiplatelet agent based on presenting history and documented evidence of intracranial hemorrhage on cerebral CT scan were included. Patients were excluded for the following reasons: repeat cerebral CT scan not performed within the first 24 hours, noncomparative repeat cerebral CT scan, chronic anticoagulation, administration of fibrinolytic medications, concurrent ischemic stroke, and neurosurgical intervention. In total, 124 patients were included, 55 received DDAVP and 69 did not.

INTERVENTIONS

DDAVP treatment at recognition of antiplatelet-associated intracranial hemorrhage versus nontreatment.

MEASUREMENTS AND MAIN RESULTS

Primary effectiveness outcome was intracranial hemorrhage expansion greater than or equal to 3 mL during the first 24 hospital hours. Primary safety outcomes were the largest absolute decrease from baseline serum sodium during the first 3 treatment days and new-onset thrombotic events during the first 7 days. DDAVP was associated with 88% decreased likelihood of intracranial hemorrhage expansion during the first 24 hours ([+] DDAVP, 10.9% vs [-] DDAVP, 36.2%; p = 0.002; odds ratio [95% CI], 0.22 [0.08-0.57]). Largest median absolute decrease from baseline serum sodium ([+] DDAVP, 0 mEq/L [0-5 mEq/L] vs [-] DDAVP, 0 mEq/L [0-2 mEq/L]; p = 0.089) and thrombotic events ([+] DDAVP, 7.3% vs [-] DDAVP, 1.4%; p = 0.170; odds ratio [95% CI], 5.33 [0.58-49.16]) were similar between groups.

CONCLUSIONS

DDAVP was associated with a decreased likelihood of intracranial hemorrhage expansion during the first 24 hours. DDAVP administration did not significantly affect serum sodium and thrombotic events during the study period.

Electrophysiological Procedures in Patients With Coagulation Disorders - A Systemic Review

Catheter ablation (CA) is considered first-line treatment for many patients with symptomatic arrhythmias. Indications for CA are constantly increasing, as is the number of procedures. Although CA is nowadays regarded a safe procedure, there is a risk of complications, including both bleeding- and thrombosis-related events. Several factors contribute to periprocedural risk; of these, patient coagulation status is of considerable clinical relevance. In this context, even a simple procedure poses a considerable challenge in a patient with coagulation disorder. However, the level of evidence regarding CA in patients with coagulation disorders is very low. Neither experts' recommendations nor clinical guidelines have been presented so far. The aim of this article is to analyze potential procedure-related risks and provide clinicians with useful information and practical suggestions regarding optimization of procedural safety in patients with coagulation disorders.

Von Willebrand disease in the elderly: clinical perspectives

Von Willebrand disease (VWD) is an inherited bleeding disorder that affects up to 1% of the population. In most cases, VWD results from a mutation in the von Willebrand Factor (VWF) gene, which alters the amount and function of VWF, a key glycoprotein in both primary and secondary hemostasis. A comprehensive analysis of patients with VWD should include VWF activity, antigen levels, platelet function, and a careful bleeding history. Treatment options include antifibrinolytics, desmopressin, and VWF replacement therapy. VWF levels fluctuate due to age, stress, environmental exposures, and pharmacologic treatment. Treatment guidelines exist to treat and prevent bleeding for patients undergoing surgery and medical procedures, but often these must be reevaluated in the setting of age-related comorbidities including cardiovascular events, venous thrombosis, and malignancy. In addition, many age-related complications are associated with a secondary acquired von Willebrand syndrome (AVWS), including malignancies, hypothyroidism, cardiovascular diseases, and cardiac replacement devices. The current literature is limited by a lack of older patients in clinical trials. Larger studies are needed to determine if age-related comorbidities affect VWD patients at different frequencies than the general elderly population. There is also a significant need for registry-based studies to evaluate many age-related comorbidities in VWD patients.

Coagulation Management During Liver Transplantation: Use of Fibrinogen Concentrate, Recombinant Activated Factor VII, Prothrombin Complex Concentrate, and Antifibrinolytics

Coagulation management, and transfusion practice in liver transplantation (LT) have been evolving in the recent years due to better understanding of coagulation abnormalities in end-stage liver disease, and clinical management of LT patients. Avoidance of allogeneic blood components is feasible in some patients, but multi-modal coagulation therapies may be necessary in others who develop complex coagulopathy due to hemorrhage, hemodilution, hypothermia, and acid-base disturbances. Transfusions of plasma and cryoprecipitate remain to be the mainstay therapy for procoagulant factor replacement during LT. Clinical efficacy and safety of these products are limited by logistic issues (eg, thawing), and mostly noninfectious complications. Considering potential alternatives to conventional transfusion is thus important to improve hemostatic resuscitation in complex LT cases. The present review is mainly focused on procoagulant properties of plasma and platelet transfusion, and currently available plasma-derived and recombinant factor concentrates, and antifibrinolytic agents in LT patients. The role of viscoelastic coagulation tests to guide specific component therapies will be also discussed.

Stasis Promotes Erythrocyte Adhesion to von Willebrand Factor

OBJECTIVE

Venous thromboembolism is a major contributor to global disease burden. Leukocytes and platelets initiate thrombogenesis on blood stasis and initiate the formation of a fibrin, VWF (von Willebrand factor), and neutrophil extracellular trap scaffold for erythrocytes. However, there is little knowledge on how erythrocytes become stably incorporated into this scaffold. Recently, we described the adhesion of calcium-loaded erythrocytes to endothelial-derived VWF strings. Because VWF is part of the scaffold of venous thrombi, we questioned whether reduced flow or stasis promotes the adhesion of normal erythrocytes to VWF and whether venous thrombi show evidence of erythrocyte-VWF interactions.

APPROACH AND RESULTS

In the present work, we perfused, under controlled shear conditions, washed, normal erythrocytes over surface-immobilized plasma and extracellular matrix proteins and showed that normal erythrocytes specifically bind to VWF. The interaction between erythrocytes and VWF significantly increased when the wall shear stress was reduced. Next, we investigated whether erythrocyte-VWF interactions support the structure of venous thrombi. High-resolution immunofluorescence imaging of human venous thrombi showed a striking pattern between erythrocytes, VWF, and fibrin, which suggests that VWF plays a supporting role, linking erythrocytes to fibrin in the thrombus.

CONCLUSIONS

Our data suggest that erythrocyte retention in venous thrombi is mediated by erythrocyte-VWF or erythrocyte-VWF-fibrin interactions. Targeting erythrocyte retention could be a new strategy in the treatment or prevention of venous thrombosis.

Prevalence and Risk Factors Associated With Hypertension in von Willebrand Disease

BACKGROUND

von Willebrand factor (VWF) is a biomarker for endothelial damage. Increased VWF levels are observed in hypertension (HTN) and disorders of endothelial dysfunction, for example, atherosclerotic heart disease (ASHD) and diabetes. Whether low VWF protects against HTN is unknown.

METHODS

To determine prevalence and risk factors for HTN in patients with von Willebrand disease (VWD), we conducted a cross-sectional analysis of discharge data from the National Inpatient Sample, 2009 to 2011. Group comparisons were performed by Rao-Scott χ² test. Odds of HTN and HTN outcomes in VWD were estimated by weighted multivariable logistic regression.

RESULTS

The prevalence of hypertension in patients with VWD (N = 7556), 37.35%, was significantly lower than that in non-VWD patients (N = 19 918 970), 49.40%, P < .0001. Hypertension risk factors (hyperlipidemia, diabetes, smoking, hepatitis C, and HIV) and HTN outcomes (ASHD, myocardial infarction [MI], ischemic stroke, and renal failure) were less common in patients with VWD than in non-VWD patients, all P ≤ .0001. Patients with VWD were younger, 49.67 versus 57.30 years, Caucasian, 82.23% versus 68.35%, and female, 75.44% versus 59.61%, P < .0001. Patients with HTN were older, 67.55 versus 47.29 years, male, 45.99% versus 34.90%, and had more HTN risk factors and HTN outcomes than those without HTN, all P < .0001, including male and female subgroups, each P < .0001. The unadjusted odds of HTN in patients with VWD (odds ratio [OR] = 0.611, P < .0001) and of HTN outcomes in patients with VWD (ASHD, OR = 0.509; MI, OR = 0.422; ischemic stroke, OR = 0.521; renal failure, OR = 0.420, all P < .0001) became insignificant after adjustment for HTN risk factors plus demographics (age/race/gender), OR = 1.035, P = .260.

CONCLUSION

The risk of HTN is reduced in patients with VWD, but not after adjustment for HTN risk factors plus demographics, as patients with VWD not having HTN are also typically young, Caucasian, and female.

Drug-Induced Thrombophilic or Prothrombotic States: An Underestimated Clinical Problem That Involves Both Legal and Illegal Compounds

Vascular thrombosis, both arterial and venous, is a condition associated with significant morbidity and mortality. There are multiple risk factors for thrombosis, both congenital and acquired, and in the majority of cases, these risk factors are not modifiable. Over the past 2 decades, multiple drugs (both illegal and legal) have been associated with increased risk of thrombosis. However, due to limited scientific literature regarding the prothrombotic tendencies of these drugs, there is a concomitant limited understanding of the pathophysiology of drug-induced thrombosis. As drugs are one of the few modifiable risk factors for thrombosis, further study and dissemination of knowledge regarding drug-associated and drug-induced thrombosis are essential and have the potential to lead to decreased future incidence of thrombosis. The mechanisms at the basis of the thrombophilic activity of these drugs are variable and sometimes still ill recognized. Increased levels of clotting factors, reduction in coagulation natural inhibitors, decreased fibrinolysis, activated clotting factors, increased blood viscosity, endothelial damage, and increased platelet number and activation are the most frequent causes. Arterial steal or coronary arteries no flow has also been implicated. In some cases due to the intake of several drugs, more than one mechanism is present in a given patient. The purpose of the present review is to analyze all the drugs demonstrated to be potentially thrombotic. It is hoped that a prudent use or nonuse of these drugs might result in a reduction of thrombosis-associated diseases.

Utility of a high VWF: FVIII ratio in preventing FVIII accumulation: a study in VWF-deficient mice

Treatment of von Willebrand disease typically requires multiple infusions of von Willebrand factor (VWF)/factor VIII (FVIII) concentrate. Accumulation of FVIII is a clinical concern due to potential risk for thromboembolism. This study sought to determine whether VWF/FVIII concentrate of high VWF:FVIII ratio can prevent FVIII accumulation. VWF-deficient knockout mice received four 150 IU/kg VWF:ristocetin cofactor (RCo) infusions at 3-h intervals, with VWF/FVIII concentrates of a high (Haemate P/Humate-P) or low (Wilate) VWF:FVIII ratio. After each infusion, trough FVIII and VWF levels in plasma were determined. Separately, pharmacokinetic analysis was performed after single 250-IU/kg VWF:RCo infusions of each concentrate. Over the course of the four infusions, trough FVIII increased significantly in the group receiving Wilate (P < 0.001), but not Haemate P/Humate P (P = 0.058). After the first infusion, mean trough FVIII level in the Wilate group (31.7 IU/dl) was greater by 82% (P = 0.017) than that in the Haemate P/Humate P group (17.4 IU/dl). After the final infusion, mean trough FVIII of animals receiving Wilate (55.1 IU/dl) continued to exceed that of Haemate P/Humate P recipients (30.2 IU/dl) significantly (P < 0.001). Trough VWF levels were similar in the two groups. The VWF pharmacokinetics of the two concentrates coincided closely; however, the FVIII peak concentration and area under the curve were approximately twice as great in the mice treated with Wilate. In a murine model of severe von Willebrand disease, a VWF/FVIII concentrate with a high VWF:FVIII ratio prevented persistent exposure to elevated trough FVIII levels.

Reduced prevalence of arterial thrombosis in von Willebrand disease

BACKGROUND

High von Willebrand factor (VWF) levels are an established risk factor for arterial thrombosis, including coronary heart disease and ischemic stroke. It has been hypothesized that von Willebrand disease (VWD) patients are protected against arterial thrombosis; however, this has never been confirmed in clinical studies.

OBJECTIVES

To investigate the prevalence of arterial thrombosis in VWD patients relative to the general population.

PATIENTS/METHODS

We included 635 adult patients with VWF levels ≤ 30 U dL(-1) , aged 16-85 years, from the nationwide cross-sectional 'Willebrand in the Netherlands' (WiN) study and compared the prevalence of arterial thrombosis with two reference populations from the general Dutch population adjusted for age and sex as standardized morbidity ratios (SMRs).

RESULTS

Twenty-nine arterial thrombotic events occurred in 21 patients (3.3%). Five patients suffered an acute myocardial infarction and three an ischemic stroke. Unstable angina pectoris was recorded 12 times, transient ischemic attack nine. The prevalence of all arterial thrombotic events combined (acute myocardial infarction, ischemic stroke and coronary heart disease) was 39% and 63% lower than in the two reference populations. The prevalence of cardiovascular disease in VWD was lower than in the general population, SMR 0.60 (95% CI, 0.32-0.98) for coronary heart disease and SMR 0.40 (95% CI, 0.13-0.83) for acute myocardial infarction. For ischemic stroke the prevalence was 35-67% lower compared with two reference populations, SMR 0.65 (95% CI, 0.12-1.59) and 0.33 (95% CI, 0.06-0.80), respectively.

CONCLUSIONS

This is the first study showing that VWD patients have a reduced prevalence of arterial thrombosis and provides important insights into the role of VWF in the pathogenesis of arterial thrombosis.

Thrombosis in VonWillebrand disease

OBJECTIVE

To date, only a few case studies have reported occurrence of thrombosis in patients with VonWillebrand disease (VWD). No studies have looked at its incidence in this patient population. The aim of this study was to test our hypothesis that decreased VonWillebrand factor (VWF) levels confer a protective effect on arterial and venous thrombosis.

METHODS

This is a retrospective cohort study including patients (n=350) with the ICD-9 code of VWD who were identified from our hospital database over a period of 25 years, out of which 198 patients were included in the final sample. A parallel control sample without VWD matched for age, sex, hypertension, hyperlipidemia, atrial fibrillation and diabetes mellitus was also obtained from the hospital database. The primary outcomes were incidence of diagnosis of symptomatic arterial and venous thrombosis. The results were computed using multivariate conditional logistic regression analysis and proportions were compared using McNemer's Chi - square test.

RESULTS

Out of 198 patients (mean age 44.2 ± 17.5, women 72%) with VWD, 170 (86%) were VWD type 1, 21 (10%) were type 2 and 7 (3%) were type 3. VWD was found to be an independent protective predictor from arterial thrombosis (OR 0.28, 95% CI 0.14-0.54, p<0.0001), more so in CAD (OR 0.28, 95% CI 0.12-0.64, p=0.002) than in CVD (OR 0.28, 95% CI 0.10-0.77, p=0.01). However this was not the case in venous thrombosis (p=0.42).

CONCLUSION

In a population of relatively younger individuals with VWD, our study suggests a reduced incidence of arterial thrombosis but not of venous thrombosis. This brings up the possibility that there could be other pathways or factors involved in arterial and venous thrombosis. To our knowledge, this is the first large observational study that has provided insight into the thrombotic disease in this group of patients.

Evaluation of the new INNOVANCE® PFA P2Y cartridge in patients with impaired primary haemostasis

Recently, the INNOVANCE® PFA P2Y (P2Y) cartridge of the PFA-100® system (Siemens Healthcare Diagnostics, Marburg, Germany) has been developed for the monitoring of adenosine diphosphate (ADP) P2Y(12) receptor inhibition in patients under dual antiplatelet therapy. The aim of this study was to evaluate the influence of pre-existing defects in primary haemostasis on the P2Y cartridge independent from specific antiplatelet medication. Therefore, the closure time (CT) of the P2Y cartridge was measured in a cohort of 176 patients with assumed bleeding disorders and compared with the results of established methods for the assessment of primary haemostasis. Von Willebrand disease (VWD) was found in 25 patients (14%). The detection rate of the P2Y cartridge regarding VWD was 64% and lower compared to the two conventional cartridges (collagen/epinephrine cartridge, CEPI, 80%; collagen/ADP cartridge, CADP, 76%). In the subgroup of VWD patients with VWF:RCo < 60 IU/dL (n = 22), the correlation analysis and the inter-rater agreement revealed only limited accordance with the two established cartridges. The correlation with the CADP cartridge (C(r) = 0.767, R(2) = 0.461; Kappa = 0.41) was higher than the correlation with the CEPI cartridge. Except for severe forms, platelet function disorders (9 patients, 5%) did not prolong the CT of the P2Y cartridge. Interestingly, the P2Y cartridge was less interference-prone to unspecific medications (23 patients, 13%). As the main conclusion, it must be taken into account that low von Willebrand factor activity can significantly influence the CTs of the P2Y cartridge when using it for the monitoring of antiplatelet therapy.

Repeated infusions of VWF/FVIII concentrate: impact of VWF:FVIII ratio on FVIII trough and peak levels in a rabbit model

The ratio of von Willebrand factor (VWF) to FVIII differs among available VWF/FVIII concentrates. Repeated infusions of concentrates with a low VWF:FVIII ratio may expose patients with von Willebrand disease to supranormal FVIII levels. The aim of this study was to determine the effects of repeated infusions with two VWF/FVIII concentrates differing in VWF:FVIII ratio on attained FVIII trough and peak levels as well as other pharmacokinetic parameters. Rabbits were randomized to receive multiple 150 IU kg⁻¹ VWF:RCo infusions at 4 h intervals with VWF/FVIII concentrates of a high (Haemate® P/Humate-P®) or low (Wilate®) VWF:FVIII ratio. Trough plasma FVIII and VWF levels were measured after each infusion. Pharmacokinetic analysis was performed using samples collected frequently after infusion. Mean FVIII trough level after the first Wilate infusion was 50.6 IU dL⁻¹ with a 95% confidence interval (CI) of 43.1-58.2 IU dL⁻¹, compared with 31.8 IU dL⁻¹ (CI, 24.4-39.1 IU dL⁻¹) for Haemate P (P<0.001). Trough levels progressively increased over the 24 h treatment period in both groups. After the final infusion, mean trough FVIII remained significantly higher (P = 0.002) in recipients of Wilate. Mean peak FVIII concentration after infusion was 67% higher in the Wilate group (167 vs. 100 IU dL⁻¹ , respectively; P = 0.002). Mean cumulative exposure to FVIII, as measured by area under the curve, was 84% greater in Wilate-treated animals. Half-life did not differ between the two concentrates. Animal model data suggest that exposure to elevated FVIII levels can be reduced through use of VWF/FVIII concentrates with higher VWF:FVIII ratios.

Congenital prekallikrein deficiency

The congenital deficiency of prekallikrein (PK) is a rare condition in which there is a peculiar discrepancy between a severe in vitro defect and absence of bleeding. The gene controlling PK synthesis is located on chromosome 4 and consists of 14 exons and 15 introns. Only approximately 80 cases of PK deficiency have been described in the literature. Owing to the lack of bleeding, most cases go undetected or, if detected, go unreported. Occasional bleeding or thrombosis have been reported in a few patients but this was only due to the presence of associated risk factors. It is certain that the defect does not protect from thrombosis. Diagnosis is based on the presence of a great prolongation of partial thromboplastin time and normal prothrombin time and thrombin time. The long partial thromboplastin time is fully corrected by the addition of normal plasma or normal serum and presents the unusual feature of shortening on long incubation times. Platelet and vascular tests are normal. Immunological studies allow differentiation into two types, namely cases of true deficiency, which are approximately 70% of the total, and cases with abnormal forms. PK is a glycoprotein synthesized in the liver as a single-chain peptide of 88000 Da. It mostly circulates (∼75%) as a complex with high-molecular-weight kininogen. It is cleaved by FXIIa into a heavy chain and a light chain (catalytic domain), held together by disulfide bonds. Molecular biology techniques have so far only been applied to eleven families, and these studies do not yet allow definite phenotype/genotype conclusions. The exons involved are 5, 8, 11, 14 and 15. The noncoagulative effects of PK, mainly based on the effect of kallikrein, have been studied less, since they appear to be the result of the involvement of other components of the contact phase. Kallikrein can mainly affect the formation of bradykinin from high-molecular-weight kininogen and the activation of pro-urokinase to urokinase. Bradykinin causes inflammation, vasodilatation and an increase in vessel permeability. The activation of pro-urokinase results in enhanced fibrinolysis. However, fibrinolysis has been reported to be normal or defective in these patients.

The clinical significance of the lack of arterial or venous thrombosis in patients with congenital prothrombin or FX deficiency

Several reports have dealt with the occurrence of both arterial and venous thrombosis in patients with haemophilia A, haemophilia B, and von Willebrand disease. Similar thrombotic events have been occasionally reported also in rare congenital coagulation disorders, particularly in fibrinogen or FVII deficiencies. On the contrary no sure venous or arterial thrombotic event has ever been reported in congenital prothrombin or Factor X deficiency. The significance of this observation is discussed. This discrepancy cannot be explained on the basis of the rarity of the two conditions, since in similarly rare congenital bleeding disorders such as FV or FXIII deficiency a few patients with thrombosis have been described. It appears that only these two defects are able to allow a sure protection from thrombosis. These observations may indirectly support the rationale for the use of direct thrombin or Factor X inhibitors in the prophylaxis and/or therapy of thrombotic manifestations.

Impact of thrombogenic mutations on clinical phenotypes of von Willebrand disease

von Willebrand disease (VWD) is a most common inherited bleeding disorder. von Willebrand factor (VWF) exists as an extracellular adaptor molecule and generally involves in the hemostasis mechanism through binding with GP (Glycoprotein) Ib-IX-V platelet receptor. Clinical phenotype of bleeding disorders modulated to a decrease in bleeding symptoms by thrombogenic mutations. We made an attempt to investigate the impact of thrombogenic mutations/polymorphisms on the clinical phenotype of 114 different types of patients with VWD, and 120 healthy controls were screened for methylenetetrahydrofolate reductase (MTHFR) 677C/T, factor V (FV) Leiden (1691G/A), beta(3) integrin (HPA-I) (Human platelets antigen-I) gene (1565T/C), and prothrombin 20210G/A mutations. Genotypic analysis was performed using polymerase chain reaction (PCR) and restriction fragment length polymorphism. Forty-five patients (39.5%) were found to be positive for at least one of the prothrombotic risk factors screened. Prothrombin 20210G/A was not found in any patient with VWD as well as healthy control. Eight patients with VWD were carrying the defective alleles of different thrombogenic markers, showing milder phenotypes than expected. A high prevalence was observed for MTHFR 677C/T (677C/C 73.6%, 677C/T 24.6%, 677T/T 1.8%) and PLA1/A2 (1565T/T 88.6%, 1565T/C 10.5%, 1565C/C 0.87%) polymorphism followed by FV Leiden (1691G/G 97.4%, 1691G/ A 2.6%, 1691A/A 0.00%) in patients with VWD with allelic frequencies 11.4% (677T), 5% (1565C), and 1.3% (1691A). Hence, we concluded that thrombophilic markers were seen to be influencing the clinical phenotypes of patients with VWD.

Thrombocytosis and leukocytosis interaction in vascular complications of essential thrombocythemia

To elucidate the role of thrombocytosis, alone or in combination with standard (age, previous cardiovascular events) and novel (leukocytosis, JAK2(V617F) mutational status) risk factors, in the cardiovascular events of essential thrombocythemia (ET), we analyzed a cohort of 1063 patients. We found that a platelet count at diagnosis greater than 1000 x 10(9)/L was associated with significantly lower rate of thrombosis in multivariable analysis and, if combined with leukocytes less than 11 x 10(9)/L, pointed to a "low-risk" category with a rate of thrombosis of 1.59% of patients/year. On the contrary, the highest risk category (thrombosis rate, 2.95% of patients/year) was constituted of patients with leukocytosis, lower platelet count, and a JAK2(V617F) mutated genotype in most cases (77% vs 26% in the low-risk group), independently from standard risk factors. These data challenge the theory that elevated platelet count increases thrombosis risk in ET and suggest prospective clinical trials to support this hypothesis.

von Willebrand factor in cardiovascular disease: focus on acute coronary syndromes

von Willebrand factor (VWF) plays a pivotal role in platelet adhesion and aggregation at sites of high shear rates (eg, in coronary arteries that have stenotic or ruptured atherosclerotic plaque lesions). Numerous studies have investigated the relationship between VWF plasma levels and thromboembolic cardiovascular events. In contrast to the rather weak association in the general population, in patients with preexisting vascular disease, VWF is significantly predictive for adverse cardiac events, including death. Likewise, VWF typically rises during the course of acute coronary syndrome, and the extent of this VWF release is an independent predictor of adverse clinical outcome in these patients. Various lines of evidence indicate that VWF is not only a marker but also actually an important effector in the pathogenesis of myocardial infarction. This central role of VWF in thrombogenesis has made it a promising target for research into new antiplatelet therapies that specifically inhibit VWF. This review focuses on the role of VWF in acute coronary syndrome and further outlines the relevance of therapeutic interventions targeting VWF for acute coronary syndrome patients.

How do you treat bleeding disorders with desmopressin?

Desmopressin is an analog of vasopressin that exerts a substantial haemostatic effect by inducing the release of von Willebrand factor from its storage sites in endothelial cells. It has proved useful in treating or preventing bleeding episodes in patients with von Willebrand disease, haemophilia A and platelet function defects. Its efficacy in achieving a satisfactory level of haemostasis has reduced the use of blood products to treat bleeding episodes. Clinicians need to become familiar with the use of this drug that has become a home medication for many patients with inherited bleeding disorders.

Arterial and venous thrombosis in rare congenital bleeding disorders: a critical review

A thorough review of the literature and of personal files has allowed the gathering of 81 patients with rare congenital bleeding disorders and thrombotic phenomena. Sixteen of these patients had congenital afibrinogenemia, eight involved factor V deficiency, 20 factor VII defects, 33 factor XI deficiencies and only one, a factor XIII defect. Altogether 42 patients showed arterial thrombosis (myocardial infarction [MI] in 28 cases; ischemic stroke in 4; arterial occlusion in 8; 2 patients with disseminated intravascular coagulation (DIC)). Ages varied between 13 and 74. Twenty-two patients were males and 16 females. In four cases, sex was not reported. There were three fatalities: two after a MI and one because of heart failure. With regard to venous thrombosis: 9 patients had pulmonary embolism, 15 patients had deep vein thrombosis, 9 patients had both pulmonary embolism and deep vein thrombosis; 1 patient had superficial vein thrombosis, whereas, 5 cases had an unusual site venous thrombosis (two portal systems, two cerebral sinuses, one inferior vena cava) for a total of 39 cases. Age varied between 3 and 86. In this case, 20 patients were males and 17 were females. In two cases, sex was not reported. There were three fatalities: two because of pulmonary embolism and one because of inferior vena cava thrombosis. The fact that thrombosis has never been described in patients with factor II or factor X seems to underscore the central antithrombotic role that these two factors have in the coagulation system.