On the Relationship between Changes in the Deep Veins Evaluated by Duplex Sonography and the Postthrombotic Syndrome 12 Years after Deep Vein Thrombosis

Bone marrow stromal cells transplantation promotes the resolution and recanalization of deep vein thrombosis in rabbits through regulating macrophage infiltration and angiogenesis

This study aims to validate whether bone marrow stromal cells (BMSCs) transplantation could promote the resolution and recanalization of deep vein thrombosis (DVT) and to explore the underlying mechanism. The right hind femoral vein was embolized to establish the DVT rabbit model. BMSCs from New Zealand white rabbits were isolated and identified, and then injected into DVT rabbits. After that, the extent of angiogenesis was determined by the amount of capillaries that were positive for antibody against vWF. Macrophage infiltration was measured by immunohistochemistry with F4/80 antibody. M1 or M2 macrophages were identified as F4/80 + CD11c ⁺ or F4/80 + CD206 ⁺ cells by using flow cytometry analysis, respectively. BMSCs were successfully isolated and identified. BMSCs transplantation promotes macrophage infiltration and angiogenesis in DVT rabbits. BMSCs transplantation causes M1/M2 polarization, altered cytokine production and increased monocyte chemotactic protein 1 (MCP-1) protein expression in DVT rabbits. However, injection of MCP-1 protein not only reversed the effects of BMSCs transplantation on macrophage infiltration and angiogenesis, but also reversed the effects of BMSCs transplantation on M1/M2 polarization and cytokine production in DVT rabbits. BMSCs transplantation promotes the resolution and recanalization of DVT in rabbits through regulating macrophage infiltration and angiogenesis, the underlying mechanism is associated with MCP-1 expression.

The postthrombotic syndrome

Following deep vein thrombosis (DVT), one of every two patients will develop postthrombotic syndrome (PTS), which causes remarkable consequences on the socioeconomic level. Residual thrombosis is an important predictor of PTS, and severe early symptoms, old age, obesity, improper anticoagulation, recurrent thrombosis and varicose veins are major risk factors. Diagnosis of PTS is mainly based on the clinical findings for patients with a history of DVT, while in those without it, instrumental diagnosis might help in detecting a previous DVT. Prompt administration of adequate compression elastic stockings (ECS) in patients with symptomatic DVT reduces the frequency of PTS by half. Usually, the management of an established PTS is demanding, and often discouraging. However, when carefully supervised and instructed to wear proper ECS, more than 50% of patients either remain quiescent or improve during long-term follow-up.

Aspects of anticoagulation in children

The number of children receiving anticoagulation is increasing. Thromboembolic events are associated with significant risk of morbidity and mortality although the optimal management of asymptomatic events remains unclear. Specific challenges in paediatrics include the diagnosis of thrombosis, delivery and monitoring of anticoagulation in a wide range of ages from neonates through to adolescents. The development of the haemostatic system as children age results in changing pathophysiology of thrombosis and response to anticoagulation agents. Although registry and observational studies have provided vital information, specific paediatric, prospective anticoagulation studies have been few and limited in design. The result is that much of current practice is extrapolated from adult studies. Traditional anticoagulants have significant limitations. Both heparin and warfarin are in widespread use but many fundamental questions regarding dose, therapeutic range, efficacy and optimum duration have not been fully answered. Alternative agents, such as direct thrombin inhibitors and the selective anti-factor Xa inhibitor fondaparinux, may have advantages for children. Clinical trials in adults and preliminary data in children are promising but caution should be applied until specific paediatric studies have demonstrated safety and efficacy.

Current prescribing patterns of elastic compression stockings post-deep venous thrombosis

Objectives

Post-thrombotic syndrome (PTS) is a complication of deep vein thrombosis (DVT) characterized by chronic pain, swelling and heaviness, and may result in ulceration. Elastic compression stockings (ECS) worn daily after DVT appear to reduce the incidence and severity of PTS. The aims of our study were to investigate practices and perceptions of DVT patients and physicians regarding the use of ECS after DVT.

Methods

Two surveys were conducted. The first was sent to 225 staff and trainee clinicians and the second was administered to 150 DVT patients.

Results

The results demonstrated that the majority of senior staff (75%) believed that ECS were effective in preventing PTS and in managing venous symptoms. However, this was in contrast with junior trainees (21%) ( P < 0.05). This resulted in only 63% of patients being prescribed ECS post-DVT. There was a lack of consensus as regards the optimal timing of initiation of ECS, duration of therapy and compression strength. Nearly all DVT patients who were prescribed ECS purchased them, 74% wore them daily, and most (61%) reported that ECS relieved swelling and symptoms. Physicians correctly predicted the main reasons for non-compliance, but misjudged the scale of patient compliance with ECS.

Conclusions

Our findings suggest that there is a lack of consensus among doctors regarding ECS use after DVT and widespread education regarding the latest evidence of the benefit of ECS after DVT.

Economic evaluation of dabigatran etexilate for the prevention of venous thromboembolism after total knee and hip replacement surgery

OBJECTIVE

This was an evaluation of the cost-effectiveness of oral dabigatran etexilate compared with subcutaneous low-molecular-weight heparin (enoxaparin) for the prevention of venous thromboembolism (VTE) after total knee replacement (TKR) and total hip replacement (THR) surgery from the perspective of the UK National Health Service.

METHODS

Dabigatran etexilate (220 mg once daily) was compared with enoxaparin (40 mg once daily) in patients undergoing TKR (duration of prophylaxis, 6-10 days) and THR (duration of prophylaxis, 28-35 days). The 10-week acute postsurgical phase was modeled using a decision tree. A Markov process (1-year cycle length) was used to model long-term events (recurrent VTE, postthrombotic syndrome, and consequences of intracranial hemorrhage) for patients' remaining lifetimes. Relative risks for VTE and bleeding events were derived from 2 Phase III studies that compared dabigatran etexilate with enoxaparin 40 mg once daily. The probabilities of long-term events were estimated using data from published longitudinal studies.

RESULTS

Rates of VTE and bleeding events did not differ significantly between dabigatran etexilate and enoxaparin. Dabigatran etexilate was less costly than enoxaparin in TKR and substantially less costly in THR, primarily due to differences in administration costs. The cost of prophylaxis for THR patients, including drugs and administration costs, was estimated at pound 137 for dabigatran etexilate and pound 237 for enoxaparin ( pound 7 for nursing time during the hospital stay, pound 91 for nurse home visits for administration after hospital discharge, and an additional pound 2 in drug costs). At a willingness-to-pay threshold of pound 20,000 per quality-adjusted life-year, the probability of cost-effectiveness for dabigatran etexilate was 75% in TKR and 97% in THR. These results were robust across a range of sensitivity analyses.

CONCLUSION

From the perspective of the UK National Health Service, thromboprophylaxis with dabigatran etexilate was cost-saving compared with enoxaparin 40 mg once daily, with comparable efficacy and safety profiles.

Cost-effectiveness of venous thromboembolism prophylaxis in total hip and knee replacement surgery: the evolving application of health economic modelling over 20 years

OBJECTIVES

In the last two decades, there has been considerable evolution of methods for cost-effectiveness modelling. Some of the first models were developed in the area of venous thromboembolism (VTE) prophylaxis. Hence, this area can serve as an important example to illustrate evolving standards. Our objectives are to document evolving methodology by describing VTE models, assess their critical strengths and weaknesses, and inform future advances for models in this therapeutic area.

RESEARCH DESIGN AND METHODS

A systematic review of economic models of primary VTE prevention following hip and knee replacement surgery was undertaken. Electronic searches of PubMed, EMBASE, the Cochrane library, and grey literature were conducted (1985-2006). Reference lists of included articles and reviews were examined for relevant studies.

RESULTS

Twenty-nine cost-effectiveness models were identified. Nineteen other cost-effectiveness analyses were excluded because they were not model-based; 16 were simple cost calculations and three were analyses of resource use data collected alongside clinical trials. The majority of models (24) were constructed as decision trees, frequently utilising previously published model structures, with some adaptation for new comparators, and/or addition of relevant events omitted by earlier models (e.g., bleeding due to prophylactic treatment). Later models have included Markov processes to model potential long-term consequences of VTE (recurrent VTE and post-thrombotic syndrome) over longer time horizons. Systematic identification of clinical evidence and more sophisticated analysis methods (e.g., Bayesian mixed-treatment comparisons and probabilistic sensitivity analyses) have recently been introduced.

CONCLUSIONS

Model structures have evolved substantially in this highly studied therapeutic area, with improvements made to the model structure, the comprehensiveness of clinical evidence included, and the underlying calculation methodology.

The U.S. Thrombosis and Hemostasis Centers pilot sites program

Venous thromboembolism (VTE) is a common disorder associated with significant morbidity and mortality. Despite important advances in understanding the etiology of VTE, delivery of care to patients with thrombosis and thrombophilia is frequently incomplete and highly variable. A comprehensive model of health care has been used successfully to treat and prevent complications for people with hemophilia and other chronic disorders. The effectiveness of an integrated healthcare model for patients with all coagulation disorders has yet to be evaluated. The Division of Hereditary Blood Disorders of the Centers for Disease Control and Prevention (CDC) is collaborating with eight Thrombosis and Hemostasis Centers (pilot sites) to provide health-related services and conduct research directed toward the reduction or prevention of complications of thrombosis and thrombophilia. The initial objectives of the collaboration are to (1) determine the efficacy of integrated multidisciplinary care and prevention services for people with hemostatic disorders, (2) assess unmet needs for service delivery and identify outreach strategies to improve access to care, (3) develop effective messages aimed at disease management and prevention, and (4) foster the development of training programs to enhance provider skills for the delivery of patient care. To address these objectives, the investigators and CDC have developed and implemented a web-based patient registry to follow prospectively service allocation and patient outcomes. Funding for the program began in October 2001. All eight funded centers are affiliated with U.S. medical schools. Principal investigators at the centers are hematologists (five adult, two pediatric) or cardiologists. Faculty in obstetrics-gynecology, surgery, and multiple other specialties are integral to the model of care at the centers. Other critical components at the centers are clinical laboratory services, training programs, research networks, and education and outreach programs. From August 2003 to March 2006, over 2,600 patients were enrolled in the registry, accounting for a total of more than 5,000 visits to the centers. Immediate goals of the data collection at the centers are to characterize patients receiving care at centers and document the state of health services provided. Long-term goals are to evaluate prospectively clinical outcomes for patients receiving multidisciplinary care and prevention services at centers. The network of data collection across centers will facilitate future collaborative clinical and epidemiologic investigations and enhance collective expertise in hemostasis and coagulation disorders.

Frequency and determinants of the postthrombotic syndrome after venous thromboembolism

PURPOSE OF REVIEW

Postthrombotic syndrome (PTS) is the most common complication of deep venous thrombosis (DVT). Identifying which patients are at high risk of developing PTS would help improve the management of patients with DVT and allow physicians to provide patients with individualized information on their expected prognosis. This review discusses the knowledge gained from key studies over the last decade on the incidence and determinants of PTS, with special emphasis on published studies from the last 2 years.

RECENT FINDINGS

About a third to half of DVT patients will develop PTS, in most cases within 1-2 years of acute DVT. Important risk factors for PTS appear to be ipsilateral recurrence of DVT, poor quality of initial anticoagulation for the treatment of DVT and increased body mass index.

SUMMARY

Preventing DVT recurrence by providing adequate intensity and duration of anticoagulation for the initial DVT and using effective thromboprophylaxis in high-risk settings is likely to reduce the frequency of PTS. Despite some advances in identifying risk factors for PTS, however, it is still not possible to reliably predict an individual patient's risk of developing PTS after an episode of DVT. Further studies of clinical determinants and biological markers of increased risk of PTS are needed to ultimately improve long-term prognosis after DVT.

Postthrombotic syndrome in children

The postthrombotic syndrome (PTS) is a clinical condition of limb pain along with physical findings that range from swelling to stasis ulcers following one or more episodes of deep vein thrombosis (DVT). While venous thromboembolism has recently gained increased recognition in children, the sequelae of limb thrombi are being recognized in a substantial proportion of affected children, and with varying degrees of severity. PTS is caused by both obstructed as well as refluxed venous blood flow, with combined effects of obstruction and reflux resulting in earlier, and more extensive symptoms. PTS can be diagnosed using an evaluation tool adapted from an international adult scale. Certain risk factors predispose children to PTS including elevations in factor VIII activity and D-dimer, clot occlusiveness, clot persistence, number of venous segments involved and duration of observation following DVT. Optimal prevention and treatment have not yet been determined, although antithrombotic therapy to facilitate rapid clot resolution, elevation, compression, moderate exercise and achievement of optimal body weight are likely to improve outcome.

The Post-thrombotic Syndrome: The Forgotten Morbidity of Deep Venous Thrombosis

The postthrombotic syndrome (PTS) is the most common complication of deep venous thrombosis (DVT) yet has received little attention from clinicians and researchers. Clinically, PTS is characterized by chronic pain, swelling, heaviness and other signs in the affected limb. In severe cases, venous ulcers may develop. PTS is burdensome and costly to patients and society because of its high prevalence, severity and chronicity. Preventing DVT with the use of effective thromboprophylaxis in high-risk patients and settings and minimizing the risk of ipsilateral DVT recurrence are likely to reduce the frequency of PTS. Compression stockings worn daily after DVT appear to reduce the incidence and severity of PTS but questions regarding their use and effectiveness remain. Future research should focus on identifying patients at high risk for PTS, assessing the role of thrombolysis in preventing PTS and evaluating the optimal use of compression stockings in preventing and treating PTS. In addition, new therapies to treat PTS should be sought and evaluated.

Cost effectiveness of bemiparin sodium versus unfractionated heparin and oral anticoagulants in the acute and long-term treatment of deep vein thrombosis

INTRODUCTION

Low-molecular-weight heparins (LMWHs) are at least as effective and well tolerated as unfractionated heparin (UFH) in the treatment of deep vein thrombosis (DVT), offering easier administration and obviating the need for anticoagulant monitoring, but have a higher acquisition cost than UFH.

OBJECTIVE

To quantify the potential economic impact of two regimens of subcutaneous bemiparin 115 IU/kg/day for 7-10 days (plus oral anticoagulants [OAC] or followed by long-term bemiparin 3500IU) versus dose-adjusted intravenous UFH for 7 days plus OAC for 3 months in the acute and long-term treatment of DVT. The representative patient was a 62-year-old, 77 kg male with proximal DVT of the lower limbs.

METHODS

A cost-effectiveness analysis was performed using a decision-tree modelling approach. The results were expressed in terms of costs (euro, 2002 values) and incremental cost effectiveness. The treatment costs (hospital stay, physician services, drug administration) and costs incurred due to complications (pulmonary embolism, recurrent DVT, bleeding events, thrombocytopenia and deaths) during the 3-month study period were considered for the primary analysis. Life expectancy and QALYs were considered for the secondary analysis. The study was performed in the setting of the Spanish National Health System.

RESULTS

Bemiparin plus OAC or long-term bemiparin for 3 months provided net cost savings of euro 769 and euro 908 per patient, respectively, compared with UFH plus OAC (UFH plus OAC euro 4128 vs bemiparin plus OAC euro 3359 vs long-term bemiparin euro 3220). Bemiparin plus OAC and long-term bemiparin for 3 months were calculated to avoid 27 and 7 additional VTE events, respectively, per 1000 patients treated. Bemiparin plus OAC or long-term bemiparin increased quality-adjusted life expectancy by approximately 1.72 and 0.74 years, respectively, compared with UFH plus OAC. The univariate sensitivity analysis supported the cost effectiveness of bemiparin in all the ranges tested for complications and costs.

CONCLUSIONS

Our model suggests that bemiparin plus OAC or long-term bemiparin for 3 months may be dominant strategies over UFH plus OAC in the treatment of DVT from the Spanish National Health System perspective, offering better outcomes and cost savings. Long-term bemiparin may be a cost-neutral alternative to bemiparin plus OAC.

Vascular endothelial growth factor naked DNA gene transfer enhances thrombus recanalization and resolution

OBJECTIVES

Enhancing thrombus resolution may reduce the long-term complications of venous thrombosis. The aim of this study was to examine whether a sustained release of vascular endothelial growth factor (VEGF) would further improve thrombus recanalization.

METHODS

Inferior caval vein thrombosis was induced in a cohort of 21 male Wistar rats. A plasmid encoding the human VEGF gene (phVEGF) was injected directly into thrombus (30 to 50 microg) and the muscle adjacent to the inferior vena cava (300 to 400 microg). A plasmid containing the gene encoding beta-galactosidase (pCMVbeta) was injected into the same sites of a separate cohort of rats to act as a control. Tissues were harvested after 1 and 2 weeks, and beta-galactosidase activity was measured to estimate transfection efficiency. Muscle and serum VEGF were measured by enzyme-inked immunosorbent assay. Thrombus size, recanalization, and organization were determined by computer-assisted image analysis.

RESULTS

The efficiency of control plasmid transfection into muscle was about 1%. No serum hVEGF was detected in phVEGF- or pCMVbeta-treated animals. Significantly raised levels of hVEGF (P < .01) were detected in the muscle injected with phVEGF after 2 weeks compared with control muscle. There was a significant reduction in thrombus size of 23% (P < .05) and 48% (P < .001) in phVEGF-treated animals compared with pCMVbeta-treated controls after 1 and 2 weeks, respectively. Thrombus recanalization was a significantly greater in the phVEGF-treated group after 2 weeks (mean 19% +/- 2% [SEM]) compared with controls (mean 13% +/- 2%, P < .01). There were no differences in the thrombus organization score.

CONCLUSION

VEGF gene therapy of venous thrombus resulted in smaller thrombi with greater recanalization. Angiogenic gene therapy may form the basis of a novel treatment that may improve the resolution of venous thrombi.

CLINICAL RELEVANCE

Deep vein thrombosis may lead to residual venous obstruction or reflux and result in post-thrombotic complications that are debilitating and have a substantial socioeconomic impact. Enhancing the resolution of venous thrombi may reduce post thrombotic complications.

Generalized changes in venous distensibility in postthrombotic patients

INTRODUCTION

In situ biomechanical properties of peripheral large veins were compared between asymptomatic young patients who had previously unilateral femoro-popliteal deep venous thrombosis (DVT) and age-matched, healthy controls; the aim of this study was to assess local or generalized alterations of venous wall biomechanics in postthrombotic patients.

PATIENTS AND METHODS

Inner diameters of both common femoral veins, right axillary vein, and right internal jugular veins were measured in two directions by ultrasonography. Venous pressure was altered by posture changes (standing and lying) and by application of graded and controlled Valsalva. Ten postthrombotic young patients without any symptoms and 11 age-matched control subjects were included.

RESULTS

In postthrombotic patients, both the affected and unaffected common femoral vein diameters and capacities were larger at low transmural pressures than those for the control group, but they demonstrated significantly less distensibility when higher pressures were applied. Similarly, in the internal jugular vein, capacity without Valsalva was significantly higher in postthrombotic patients and distensibility was reduced (statistically significant in the erect position). Pressure-induced changes in axillary vein diameter were negligible.

CONCLUSIONS

In situ diameter and capacity changes, and in situ distensibility of the femoral veins on both sides (i.e., the side of previous thrombosis as well as the disease-free side) and of the jugular veins are reduced in the young DVT patients compared to veins of the age-matched, healthy controls. The pathophysiological mechanism of generalized venous wall changes in these young DVT patients remains unknown.

Estudio prospectivo de los factores de riesgo de desarrollo de síndrome postrombótico tras una trombosis venosa profunda proximal

BACKGROUND AND OBJECTIVE

The incidence and risk factors for the development of post-thrombotic syndrome (PTS) are not well known, so the aim of our study is to evaluate the development of PTS after proximal deep vein thrombosis (DVT) and its relationship with several clinical, laboratory and therapeutic factors.

PATIENTS AND METHOD

Prospective, observational study.

INCLUSION CRITERIA

consecutive patients with acute symptomatic proximal DVT in the lower extremities diagnosed between February 2000 and July 2002.

EXCLUSION CRITERIA

life expectancy < 12 months, impossibility for follow-up, renal or hepatic failure, previous PTS or varicosis and recurrent thrombosis during follow up. Endpoint: PTS at 12 months. Explicative variables: clinical risk factors for DVT, D-dimer value, hypercoaguable state, anticoagulant therapy and compression stockings compliance. Multivariable analysis (logistic regression) was performed.

RESULTS

One hundred and seventy two patients with DVT were evaluated for inclusion. Sixty nine were excluded and 87 patients completed follow-up. PTS appeared in 47 patients (54%). Compliance of compression stockings was adequate in 57% of patients and decreased 45% the risk for PTS (p = 0.01). No significant associations were observed between PTS and others variables. Multivariable analysis confirmed the protective effect of compression stockings (RR = 0.3; p < 0.01) and previous ipsilateral DVT appeared significatively associated with PTS development (RR = 8; p = 0.01) CONCLUSIONS: About 50% of patients with proximal DVT develop PTS within 1 year. Previous ipsilateral DVT is the strongest risk factor for PTS. Regular compression stocking use decreases the risk of PTS by 50%.

Iliac compression syndrome and recanalization of femoropopliteal and iliac venous thrombosis: a prospective study with magnetic resonance venography

OBJECTIVES

Poor iliac vein recanalization has been associated with compression of the left common iliac vein by the right common iliac artery (RCIA/LCIV compression); however, this finding has been difficult to confirm. In a baseline study, RCIA/LCIV compression was detected with magnetic resonance imaging in patients with deep venous thrombosis. We compared recanalization of left femoropopliteal and iliac thrombosis with and without RCIA/LCIV compression.

METHODS

This was a prospective blinded study carried out in a 1355-bed university hospital. Thirty-one patients were recruited from consecutive cohorts of patients with iliofemoral and femoropopliteal DVT who underwent direct thrombus magnetic resonance imaging, venous enhanced peak arterial magnetic resonance venography, and magnetic resonance arteriography as part of the baseline study relating RCIA/LCIV compression to extent of thrombosis. Magnetic resonance venography was performed 6 weeks, 6 months, and 1 year after diagnosis of deep venous thrombosis. Femoropopliteal and iliac venous segments that were occluded at diagnosis were classified as occluded, partially occluded, or patent on follow-up scans.

RESULTS

At 6-week follow-up, recanalization of all segments was incomplete. At both 6-month and 1-year follow-up, recanalization of left iliac segments associated with RCIA/LCIV compression was poorer compared with recanalization of left iliac segments not associated with compression (6 of 6 occluded vs 1 of 6 occluded and 1 of 6 partially occluded at 6 months, P =.015; 6 of 6 occluded vs 5 of 5 patent at 1 year, P = .002). This was due to complete failure of recanalization of left common iliac veins associated with RCIA/LCIV compression in 6 of 6 cases. All other iliac and femoropopliteal segments including left external iliac veins associated with RCIA/LCIV compression had high rates of recanalization at both 6 months and 1 year.

CONCLUSION

RCIA/LCIV compression is associated with persistent occlusion of the left common iliac vein. The recanalization rate for all other femoropopliteal and iliac segments was high.

Prolonged enoxaparin therapy to prevent venous thromboembolism after primary hip or knee replacement. A cost-utility analysis

BACKGROUND

Among patients undergoing elective total hip or knee replacement, prolonged prophylaxis with low-molecular-weight heparin significantly reduces the risk of symptomatic venous thromboembolism. Whether implementing routine prolonged prophylaxis is cost-effective remains uncertain.

METHODS

We performed an economic modeling study to compare the costs and health outcomes of standard (12 days) with prolonged (42 days) enoxaparin prophylaxis against venous thromboembolism after elective total hip and knee replacement. The primary economic perspective was that of a societal healthcare payer, taking Belgium as a case country. We used cost-utility analysis, a form of cost effectiveness analysis in which costs are reported in monetary terms (euros) and health outcomes are converted into quality-adjusted life years (QALYs) gained, thereby incorporating a measure of quality of life (utility) into the health outcomes. Costs for diagnosis and treatment of proximal and distal deep vein thrombosis, pulmonary embolism, postphlebitic syndrome, and major bleeding were obtained from a Delphi panel (orthopaedic surgeons) and the official reimbursement rates (Federal Ministry of Health). QALYs for these health outcomes were based on utility scores as reported in the literature. The main outcome measure was the incremental cost-utility ratio, reported as the incremental cost per quality-adjusted life year gained (euros/QALY). The incremental cost-utility ratio refers to the amount of money needed to produce one additional QALY. We also performed sensitivity analyses on clinical and economic parameters to identify important model uncertainties.

RESULTS

In the base-case analysis, incremental costs of prolonged prophylaxis amounted to 58 euros and 114 euros per patient, with an additional gain in QALY of 0.0083 and 0.0018 after total hip and knee replacement, respectively. Thus, a strategy of prolonged enoxaparin prophylaxis was associated with a cost-utility ratio of 6,964 euros/QALY and 64,907 euros/QALY after total hip and knee replacement, respectively. This tenfold difference in incremental cost-utility ratios between hip and knee replacement might have important practical implications. According to recent European guidelines, an intervention costing less than 20,000 euros per QALY is said to exhibit strong evidence for adoption, whereas one costing 20,000-100,000 euros exhibits moderate evidence for adoption. By current European guidelines, the cost of 6,964 euros and 64,907 euros per QALY gained would give strong evidence for adoption of prolonged enoxaparin prophylaxis among total hip replacement patients, but moderate evidence for adoption among total knee replacement patients. Sensitivity analyses using 20% changes from the base-case analysis showed this outcome to be robust.

CONCLUSIONS

Our findings indicate that, among patients undergoing elective total hip or knee replacement, prolonged enoxaparin prophylaxis leads to increased health benefits at increased cost. Given the additional costs that healthcare decision makers in Europe are usually prepared to pay for a gain in utility, prolonged prophylaxis with enoxaparin is cost-effective after elective total hip replacement, and our data provide strong evidence for adoption of prolonged enoxaparin prophylaxis after elective total hip replacement.

Surgical disobliteration of postthrombotic deep veins—endophlebectomy—is feasible

OBJECTIVE

Partial obstruction of postthrombotic veins is caused by endovenous scar tissue, which creates synechiae and septae that narrow and sometimes block the lumen. We have performed surgical disobliteration, or endophlebectomy, of chronically obstructed venous segments during various kinds of deep venous reconstructions to increase the flow through previously obstructed segments. In this article we describe the endophlebectomy technique, and report the availability of this procedure as an adjunct to deep venous reconstructions for the treatment of postthrombotic chronic venous insufficiency. Patients and methods Between July 1996 and February 2003, surgical disobstruction of 23 deep venous segments was performed in 13 patients in association with 14 deep venous reconstructions to treat advanced postthrombotic chronic venous insufficiency. Postthrombotic veins were surgically exposed, and a longitudinal venotomy was carried out at a variable length. The synechiae and masses attached to the intimal layer were carefully excised. Mean duplex scanning follow-up was 10.8 +/- 8.2 months (median, 8 months; range, 1-28 months).

RESULTS

In 10 patients (77%) the treated segments remained primarily patent at median follow-up of 8 months (range, 1-28 months). Early thrombosis near the endophlebectomy site occurred in 3 patients, at 2, 5, and 12 days, respectively, after surgery. In 2 patients with early thrombosis further interventions were carried out with success. In a third patient with early postoperative thrombosis the final outcome was recanalization and reflux. These results yielded an overall secondary patency rate of 93%. No perioperative pulmonary embolism was observed.

CONCLUSION

This series demonstrates that surgical disobliteration of postthrombotic deep veins is technically feasible, and led to patency of the segments for the duration of follow-up for up to 28 months (mean, 10.8 +/- 8.2 months). We used this technique with the objective of disobstructing postthrombotic veins, to increase flow through a previously narrowed lumen. Postoperative thrombosis at the site of endophlebectomy occurred in 23% of patients. Although this early experience is encouraging, further studies and longer follow-up are necessary to assess the durability of the procedure.

Thromboembolism

Venous thomboembolism (VTE) causes only about 2% of maternal deaths in the developing world but is a leading cause of direct maternal deaths in developed countries. Pregnancy increases the risk of VTE through venous stasis, changes in blood coagulability and damage to vessels. Early diagnosis of VTE depends crucially on awareness of the condition but clinical diagnosis is unreliable in pregnancy and objective testing is essential. Compression or duplex ultrasonography is used to diagnose deep venous thrombosis and a ventilation/perfusion scan for pulmonary embolism. Low molecular weight heparins are safe and effective for treatment and for thromboprophylaxis in pregnancy. All women should undergo risk assessment in early pregnancy or preferably before pregnancy. Identifying risk factors such as obesity, or a past or family history of thromboembolism, allows at-risk women to be offered thromboprophylaxis. Guidelines on thromboprophylaxis have reduced deaths after caesarean section and are now being developed for all women.

Predictors of residual venous obstruction after deep vein thrombosis of the lower limbs: a prospective cohort study

INTRODUCTION

Delayed thrombus regression after deep vein thrombosis (DVT) of the lower limbs is associated with increased risk of DVT recurrence. Predictors of residual venous occlusion are unknown. We hypothesized that obesity, which causes reduced fibrinolytic activity, can predict delayed thrombus regression.

MATERIALS AND METHODS

In a prospective cohort study, 98 patients with objective diagnosis of DVT underwent compression ultrasonography (CUS) after 6 and 12 months. Persistent occlusion was arbitrarily defined as a thrombus occupying, at maximal point of compressibility, more than 20% of the vein area in the absence of compression. The body mass index (BMI) and waist circumference were measured at baseline and at follow up to assess individual patterns of body fat distribution. Information on antithrombotic treatment, family history of varicose veins, cigarette smoking, concomitant disorders, the presence of known risk factors for DVT, the duration of anticoagulant treatment and the use of elastic stockings was collected.

RESULTS

Post-thrombotic recanalization was documented in 34 patients (34.7%) at 6 months and in 44 patients (44.9%) at 12 months. There was no difference in the mean BMI (p=0.469 at 12 months), in the prevalence of obesity (p=0.479) and visceral pattern of body fat distribution (p=0.239) between patients who did and did not show thrombus regression. The presence of a permanent risk factor for DVT was the only predictor of delayed thrombus regression (OR 11.0, 95% CI 1.359-61.978).

CONCLUSIONS

Despite consistent evidence of impaired fibrinolysis, obesity is not associated with persistent venous obstruction.

The rationale and evidence for the treatment of lower-extremity deep venous thrombosis with thrombolytic agents

This article presents the rationale and evidence for the treatment of lower-extremity deep venous thrombosis (DVT) with thrombolytic agents. DVT is a common condition that has both acute and chronic complications. Standard treatment including anticoagulation therapy and compression stockings may not be entirely adequate, because a significant proportion of patients eventually develop severe post-thrombotic syndrome (PTS). Thrombolytic agents offer a potential advantage because they may reduce residual vein stenosis and valve damage. The authors performed a systematic review of published randomized trials evaluating thrombolytic agents for DVT. The authors determined that thrombolysis therapy results in greater lysis and complication rates than does anticoagulation alone. The authors also found that PTS incidence is lower in patients treated with thrombolytics. However, several methodological flaws limit the conclusions with respect to reduction in PTS. Therefore, the authors conclude that although the lysis rate is greater for thrombolytic agents, they cannot be recommended routinely for DVT treatment.

The post-thrombotic syndrome: current knowledge, controversies, and directions for future research

The post-thrombotic syndrome (PTS) is a long-term complication of deep venous thrombosis (DVT) that is characterized by chronic, persistent pain, swelling and other signs in the affected limb. PTS is common, burdensome and costly. It is likely to increase in prevalence, since despite widespread use of and improvements in the efficacy of thromboprophylaxis, the incidence of DVT has not decreased over time. About 20-50% of patients develop PTS within 1-2 years of symptomatic DVT, and severe PTS, which can include venous ulcers, occurs in 5-10% of cases. Although there is no gold standard for the diagnosis of PTS, the presence of typical clinical features in a patient with previous DVT provides strong supporting evidence. Objective evidence of venous valvular incompetence helps to confirm the diagnosis in symptomatic patients. Preventing ipsilateral recurrence of DVT, by ensuring an adequate duration and intensity of anticoagulation for the initial DVT and by prescribing situational thromboprophylaxis after discontinuation of oral anticoagulants, is likely to reduce the risk of developing PTS. There is no proven role for thrombolysis of the initial DVT to prevent PTS. Daily use of graduated compression stockings after DVT may reduce the risk of PTS, and may prevent worsening of established PTS. Pending the results of ongoing studies, stockings are recommended in patients with persistent symptoms or swelling after DVT. Future research should focus on standardizing criteria for PTS diagnosis, identification of DVT patients at high risk for PTS, and rigorously evaluating the effectiveness of stockings, thrombolysis, and venoactive drugs in preventing or treating PTS.

[Role of plasminogen activators in the treatment of deep venous thrombosis]

In deep vein thrombosis, thrombolytic agents can improve vein patency more rapidly than conventional anticoagulant therapy. The clinical benefit of thrombolytic use would be a reduction in the incidence and severity of the postthrombotic syndrome and limb salvage in "phlegmatia caerulea". A literature review suggests that streptokinase and rt-PA do better than heparin regarding vein patency. A clinical benefit on postthrombotic syndrome can only be suggested by available evidence. The risk of major bleeding is increased by thrombolytic agents as compared with heparin. Mortality for cerebral bleeding is about 0.5%. Currently, thrombolytic therapy is only recommended for limb salvage in phlegmatia caerulea.

Early thrombus remodelling of isolated calf deep vein thrombosis

OBJECTIVE

this prospective study was designed to evaluate the evolution of thrombus propagation and lysis in relation to patterns and distribution of isolated calf DVT.

METHODS

fifty-two limbs in 48 patients mean age 59+/-15, range 24-78 years, with isolated calf DVT that had at least one exam within 10 days of DVT detection were included in the study. Patients with a documented episode of prior DVT or evidence of post-thrombotic changes during the initial ultrasound exam were excluded. The initial thrombus length, patterns and location of the thrombi were recorded. On follow-up the propagation and lysis patterns of the clot were studied.

RESULTS

remodelling of the thrombus, excluding echotexture and vein diameter changes on ultrasound, occurred in 23 limbs, (44%). Ascending propagation only was seen in seven limbs (13%) descending propagation only in two (4%) and in both directions in five (10%). Propagation at least to popliteal vein was detected in seven limbs (13%). Thrombus developed or extended to initially uninvolved veins in six limbs (12%). Pulmonary embolism developed only in one patient (2%; 95% CI: 0-11%). The site and the size of thrombus or the number of veins involved in the baseline exam did not correlate with the remodeling of thrombus. Soleal and gastrocnemial veins were comparable with the posterior tibial and peroneal veins in terms of thrombus propagation and lysis.

CONCLUSIONS

early thrombus remodelling occurs in 44% of limbs with isolated calf DVT. This includes ascending and descending thrombus propagation and lysis. Thrombus development or propagation to initially uninvolved calf veins is found in 12%. Thrombus remodelling does not appear to be related to size, site and patterns of thrombosis.

Low molecular weight heparin versus oral anticoagulants in the long-term treatment of deep venous thrombosis

PURPOSE

The purpose of this study was to evaluate whether low molecular weight heparin (LMWH) could be equal or more effective than conventional oral anticoagulants (OAs) in the long-term treatment of deep venous thrombosis (DVT).

METHODS

One hundred fifty-eight patients with symptomatic DVT of the lower limbs confirmed by means of duplex ultrasound scan were randomized to receive 3 to 6 months' treatment with nadroparine calcium or acenocoumarol. Quantitative and qualitative duplex scan scoring systems were used to study the evolution of thrombosis in both groups at 1, 3, 6, and 12 months.

RESULTS

During the 12-month surveillance period, two (2.5%) of the 81 patients who received LMWH and seven (9%) of the 77 patients who received OAs had recurrence of venous thrombosis (not significant). In the LMWH group no cases of major bleeding were found, and four cases (5.2%) occurred in the OA group (not significant). The mortality rate was nine (11.1%) in the LMWH group and 7.8% in the OA group (not significant). The quantitative mean duplex scan score decreased in both groups during the follow-up and had statistical significance after long-term LMWH treatment on iliofemoral DVT (1, 3, 6, and 12 months), femoropopliteal DVT (1-3 months), and infrapopliteal DVT (first month). Duplex scan evaluation showed that the rate of venous recanalization significantly increased in the common femoral vein at 6 and at 12 months and during each point of follow-up in the superficial and popliteal veins in the LMWH group. Reflux was significantly less frequent in communicating veins after LMWH treatment (17.9% vs 32.2% in the OA group). The reflux rates in the superficial (22.4% in the LMWH group, 30.6% in OA group) and deep (13.4% vs 17.7%) venous system showed no significant differences between groups.

CONCLUSIONS

The unmonitored subcutaneous administration of nadroparine in fixed daily doses was more effective than oral acenocoumarol with laboratory control adjustment in achieving recanalization of leg thrombi. With nadroparine, there was less late valvular communicating vein insufficiency, and it was at least as efficacious and safe as oral anticoagulants after long-term administration. These results suggest that LMWHs may therefore represent a real therapeutic advance in the long-term management of DVT.

The effects of a mechanical thrombolytic device on normal canine vein valves

PURPOSE

To determine if the Arrow-Trerotola Percutaneous Thrombolytic Device (PTD) causes damage to normal vein valves.

MATERIALS AND METHODS

Ten lateral saphenous veins in five dogs were studied with descending venography with use of a wedge balloon catheter positioned above 48 valves (demonstrating 51 valves) before and after five antegrade passes each with an over-the-wire (0.025-inch), 6.5-F, 9-mm-diameter PTD. Vein diameters were 3.2-11.4 mm (mean, 5.9 mm). Contrast matter was injected at incremental rates from 3 to 15 mL/min during continuous pressure monitoring. Imaging was performed with digital subtraction angiography at a rate of 1 frame/sec. The time to valve reflux was determined by noting the frame at which reflux was first seen through the valve. The time to reflux and pressure required to reflux were compared before and after the PTD passes. All vessels were explanted and evaluated histologically for presence or absence of endothelial loss, thrombus formation, inflammation, or valve degeneration. Four veins in two animals were studied with venography to determine the variability of the venographic method. These veins thrombosed during venography and therefore served as positive pathologic controls. In two animals, one vein was studied with venography and one was not studied to provide pathologic controls.

RESULTS

With use of two physiologic tests of valve function, 77% of valves had minimal or no damage as assessed by valve competency and 80% had minimal or no damage as demonstrated by the change in the pressures the valve can withstand before reflux. Twenty-six of 51 valves (51%) had no difference or later reflux after PTD use. Thirteen (26%) refluxed 1 second earlier after PTD use and 12 (23%) refluxed > or =2 seconds earlier (six at 2, four at 3, and two at 4). Four of the six valves with more than a 2-second difference in reflux times were in valves with diameters less than 4.2 mm. All these vessels were smaller than 7 mm in diameter. Twenty-one of 48 valve levels (44%) had no difference or sustained higher pressures before reflux after PTD use. Seventeen (36%) had a pressure drop of <10 mm Hg; five (10%) had drops of 12-24 mm Hg; and five (10%) had drops of more than 40 mm Hg. There was a significant difference in endothelial loss, thrombus formation, and inflammation between experimental veins, the veins with thrombus, the venography controls, and the normal vein controls. There was significant difference only in terms of inflammation when the experimental group was compared to the thrombosis group.

CONCLUSION

The antegrade use of the PTD across normal canine vein valves does not cause physiologically significant damage in valves 7 mm or larger in diameter in this animal model.

The post-thrombotic syndrome

One of every three patients with deep-vein thrombosis of the lower extremities will develop, within 5 years, post-thrombotic sequelae that vary from minor signs to severe manifestations such as chronic pain, intractable edema, and leg ulceration. The post-thrombotic syndrome (PTS) develops as a result of the combination of venous hypertension due to persistent outflow obstruction or valvular incompetence and abnormal microvasculature or lymphatic function. Among factors potentially related to the development of PTS, recurrent ipsilateral thrombosis plays a major role. Whether the extent and the location of the initial thrombosis are associated with the development of PTS is still controversial. The diagnosis of PTS can be accepted on clinical grounds for patients with a history of venous thrombosis. The combination of a standardized clinical evaluation with the results of compression ultrasonography and Doppler ultrasonography helps diagnose or exclude a previous proximal-vein thrombosis. Prevention of recurrent thrombosis and use of compression elastic stockings are the cornerstones of PTS prevention. The management of this condition is demanding and often frustrating. Although several surgical procedures have been tested, conservative treatment is largely preferable, as more than 50% of patients either remain stable or improve during long-term follow-up, if carefully supervised and instructed to wear proper elastic stockings. Clinical presentation helps predict the prognosis, being the outcome of patients who refer with initially severe manifestations more favorable than that of patients whose symptoms progressively deteriorate over time.

Thrombolytic therapy for venous thrombosis and pulmonary embolism

Streptokinase, urokinase, tissue plasminogen activator and similar drugs can all cause lysis of venous thrombi and pulmonary emboli, but there is small evidence that accelerated lysis achieves a significantly better clinical outcome, on average, in the shorter or longer term, than heparin alone. Thrombolytic therapy for deep leg vein thrombosis aims to restore flow and to preserve venous valves, and so to prevent chronic post-phlebitic disability, but no trial has convincingly demonstrated that the last can be achieved in more than a few patients. Only a small minority of people with extensive proximal thrombosis develop disabling post-phlebitic venous insufficiency, and there are no good clinical predictors of this outcome. As a result, any widespread use of thrombolytics would bring an immediate risk of major bleeding to many people who will never be destined to develop a clinically important problem. Thrombolytic therapy after venous thrombosis should be avoided except, perhaps, in a few carefully selected patients with severe obstruction. The case for using thrombolytics after recent pulmonary embolism is strongest in the limited number of patients with ongoing hypoxia, respiratory distress, pulmonary hypertension and right heart failure, because thrombolytic therapy often achieves an impressive and almost immediate clinical benefit in this clinical setting. Whether early relief from pulmonary artery obstruction translates into longer-term advantage over heparin remains uncertain, however, because no comparative trial has ever shown these drugs to reduce mortality after pulmonary embolism. In all cases, both the physician and the patient must balance the certainty of an immediate bleeding risk against the uncertainty of a better than marginal real benefit.