The post-thrombotic syndrome: progress and pitfalls

Low-dose systemic thrombolytic therapy for deep vein thrombosis in pediatric patients

Reduction of thrombus size and recanalization of vessels after deep vein thrombosis (DVT) are important goals to prevent recurrent thrombosis and development of postthrombotic syndrome. Thrombolysis is effective but concern for bleeding complications has limited its use in children. We retrospectively analyzed data for children with DVT treated with a low-dose systemic tissue plasminogen activator (tPA) regimen. Twenty-three pediatric patients (12 males and 11 females, median age 12 y) received low-dose systemic tPA, initiated at 0.03 to 0.06 mg/kg/h for a median of 24 hours (range 12 to 48 h). Of the 20 patients imaged within 24 hours of therapy, 6 (30%) showed partial to complete thrombus resolution. Eight patients subsequently received increased tPA at 0.12 mg/kg/h for an additional 24 hours (range 12 to 36 h). Six of these 8 (75%) patients responded to the increased dose. The overall response at the end of thrombolytic therapy was 59% (13/22). Two bleeding complications occurred without serious sequelae. Low-dose tPA administration leads to a substantial response rate although the risk of bleeding remains unclear. A prospective multicenter trial of low-dose thrombolytic therapy in children with acute DVT is warranted.

Effect of early physical activity on long-term outcome after venous thrombosis

OBJECTIVE

To determine if the level of self-reported physical activity 1 month after deep vein thrombosis (DVT) is associated with the risk of post-thrombotic syndrome (PTS) in the first 2 years post-DVT.

DESIGN

Prospective cohort study.

SETTING

Multicenter study (8 hospitals).

PARTICIPANTS

Patients presenting with objectively diagnosed acute DVT to 8 hospitals in Quebec and Ontario, Canada.

ASSESSMENT OF RISK FACTORS

We used validated questionnaires to measure physical activity (Godin questionnaire) and venous disease severity [generic physical quality of life (SF-36 PCS scale) or VEINES-QOL]. We adjusted for potential confounding effects of age, sex, and body mass index. We used multiple imputation to account for missing data.

MAIN OUTCOME MEASURES

Post-thrombotic syndrome (validated Villalta scale).

RESULTS

For the 387 patients enrolled, univariate analysis suggested no association between 1-month activity and risk of PTS. After adjusting for missing data and potential confounders, there was no evidence of a trend toward increasing risk of PTS with increasing physical activity [1.65 (95% confidence interval, 0.87-3.14) for mild-moderate activity and 1.35 (95% confidence interval, 0.69-2.67) for high activity]. The results were similar when PTS was dichotomized as none/mild versus moderate/severe. Finally, patients with PTS had lower levels of activity at 2 years post-DVT.

CONCLUSIONS

The level of self-reported exercise in the first month post-DVT is not associated with an increased risk of PTS in the first 2 years after DVT. Post-thrombotic syndrome is associated with decreased levels of physical activity 2 years after DVT.

Contemporary issues in the prevention and management of postthrombotic syndrome

OBJECTIVE

To provide an evidence-based review and clinical summary of postthrombotic syndrome (PTS).

DATA SOURCES

A literature review was performed via MEDLINE (1950-July 1, 2009) and International Pharmaceutical Abstracts (1970-June 2009) searches using the terms post-thrombotic syndrome, post-phlebitic syndrome, deep vein thrombosis, and compression stockings.

DATA SYNTHESIS

PTS is best characterized as a chronic syndrome of clinical signs and symptoms including pain, swelling, parasthesias, and ulceration in the affected limb following deep vein thrombosis (DVT). It occurs in up to half of patients with symptomatic DVT, usually within the first 2 years. Although the pathophysiology of PTS is not well understood, a thrombus may cause venous hypertension and valvular incompetence resulting in edema, tissue hypoxia, and in severe cases, ulceration. Risk factors for PTS include recurrent ipsilateral DVT, obesity, and poor quality of anticoagulant therapy. PTS diagnosis is based on the presence of typical signs and symptoms and may be made using one of several clinical scoring systems. Prevention of PTS should focus on DVT prevention and the use of elastic compression stockings following DVT, while fibrinolysis remains under investigation as an effective method for PTS prevention. The treatment of PTS may include either pharmacologic or mechanical modalities, although none of these regimens has been rigorously tested. Pharmacists have the opportunity to provide more comprehensive antithrombotic management by educating patients and providers on PTS, recommending appropriate preventive therapy, assisting patients in obtaining and adhering to this therapy, and assisting providers with the management of PTS.

CONCLUSIONS

Providers should be proactive in preventing PTS, with pharmacists taking an active role in optimal DVT prevention, identifying patients at risk for PTS, and counseling and directing preventive therapies.

Catheter-directed thrombolysis vs. anticoagulant therapy alone in deep vein thrombosis: results of an open randomized, controlled trial reporting on short-term patency

BACKGROUND

Approximately one in four patients with acute proximal deep vein thrombosis (DVT) given anticoagulation and compression therapy develop post-thrombotic syndrome (PTS). Accelerated removal of thrombus by thrombolytic agents may increase patency and prevent PTS.

OBJECTIVES

To assess short-term efficacy of additional catheter-directed thrombolysis (CDT) compared with standard treatment alone.

PATIENTS AND METHODS

Open, multicenter, randomized, controlled trial. Patients (18-75 years) with iliofemoral DVT and symptoms < 21 days were randomized to receive additional CDT or standard treatment alone. After 6 months, iliofemoral patency was investigated using duplex ultrasound and air-plethysmography assessed by an investigator blinded to previous treatment.

RESULTS

One hundred and three patients (64 men, mean age 52 years) were allocated additional CDT (n = 50) or standard treatment alone (n = 53). After CDT, grade III (complete) lysis was achieved in 24 and grade II (50%-90%) lysis in 20 patients. One patient suffered major bleeding and two had clinically relevant bleeding related to the CDT procedure. After 6 months, iliofemoral patency was found in 32 (64.0%) in the CDT group vs. 19 (35.8%) controls, corresponding to an absolute risk reduction (RR) of 28.2% (95% CI: 9.7%-46.7%; P = 0.004). Venous obstruction was found in 10 (20.0%) in the CDT group vs. 26 (49.1%) controls; absolute RR 29.1% (95% CI: 20.0%-38.0%; P = 0.004). Femoral venous insufficiency did not differ between the two groups.

CONCLUSIONS

After 6 months, additional CDT increased iliofemoral patency from 36% to 64%. The ongoing long-term follow-up of this study will document whether patency is related to improved functional outcome.

What happens after venous thromboembolism?

Venous thromboembolism (VTE) comprises deep vein thrombosis (DVT) with or without symptomatic pulmonary embolus (PE). The incidence of a first episode of VTE is 1.5 per 1000 person-years [1] (J Thromb Haemost, 2007;5:692-9) with a per-person lifetime incidence of 5% [2] (Arch Intern Med 1998;158:585-93). The risk of recurrence after DVT and PE is similar but the pattern of recurrence tends to reflect the initial event, for example recurrence with PE is more common in patients with previous PE [3] (Circulation 2003;107:122-30). At least 50% of patients, who present with symptomatic DVT, have asymptomatic PE and conversely, a majority presenting with symptomatic PE have asymptomatic DVT [3] (Circulation 2003;107:122-30). This suggests that whilst DVT and PE are manifestations of the same pathology, the phenotypic expression of the disease is predetermined. This may be an important consideration for long-term anticoagulant therapy as the risk of fatal PE is the greatest in patients with previous PE [4] (Ann Intern Med 2007;147:766-74). At present, the only factor reported to be associated with the pattern of VTE is the factor V Leiden mutation [5] (Thromb Haemost 1999;81:345-8). This suggests that the kinetics of thrombin generation and the resulting fibrinolytic response may influence clot structure and likelihood of embolization.

Measurement properties of the Villalta scale to define and classify the severity of the post-thrombotic syndrome

SUMMARY

The post-thrombotic syndrome (PTS) is a frequent and important complication of deep venous thrombosis (DVT). The diagnosis of PTS is based primarily on the presence of typical symptoms and clinical signs. In the 1990s, a clinical scale known as the Villalta scale was proposed as a measure that could be used to diagnose and classify the severity of PTS. The objective of the present paper was to review the published evidence on the measurement properties of the Villalta scale. Results of the review demonstrate that the Villalta scale is a reliable and valid measure of PTS in patients with previous, objectively confirmed DVT. The scale is acceptable to research subjects and research personnel, and shows responsiveness to clinical change in PTS. Aspects of the Villalta scale that merit further evaluation include test-retest reliability, more detailed assessment of ulcer severity and assessment of responsiveness across the full range of PTS severity. Research aimed at improving the measurement of PTS will also help to improve the overall validity of findings generated by clinical studies of PTS.

Inflammation in deep vein thrombosis and the development of post-thrombotic syndrome: a prospective study

BACKGROUND

The aim of this study was to investigate whether inflammatory markers (interleukin-6 [IL-6] and C-reactive protein [CRP]) in the acute phase of deep vein thrombosis (DVT) are associated with elevated venous outflow resistance (VOR), thrombosis score (TS), reflux and the development of clinical post-thrombotic syndrome (PTS).

METHODS

In 110 patients with a first DVT, plasma concentrations of IL-6 and CRP were determined on the day of admission. VOR, TS and reflux were measured 7 days, 1 and 3 months after diagnosis. After 1 year patients were evaluated for PTS using the Clinical, Etiologic, Anatomic and Pathophysiologic (CEAP) classification and Villalta scale.

RESULTS

Median levels of IL-6 and CRP were 7 pg mL(-1) and 21 mg L(-1), respectively. After 3 months, VOR was elevated in 33 patients (30%), TS in 33 (30%) and reflux in 57 (52%). Incidence of PTS was 36.7% using CEAP>or=3 and 35.4% using Villalta-scale>or=5. Elevated levels of IL-6 and CRP were related to higher outcomes of VOR after 3 months [relative risks (RR) 2.4 (95% CI 1.5-3.9) and 1.4 (1.1-3.3), respectively] and for IL-6 to TS [1.5 (1.1-2.1)]. For reflux no relation was found. After 90 days, elevated outcomes of VOR, TS and reflux were related to PTS after 1 year. The association of IL-6 and CRP with PTS was weak using the CEAP classification with a RR of 1.2 (0.7-2.2) and 1.8 (0.9-3.3) and absent according to the Villalta scale 0.6 (0.2-1.4) and 1.2 (0.6-2.5), respectively.

CONCLUSION

The results of this study suggest that inflammation might play a role in incomplete thrombus clearance, venous outflow obstruction and the development of PTS after 1 year.

Thrombolysis for intravascular thrombosis in neonates and children

PURPOSE OF REVIEW

Plasminogen activators stimulate the fibrinolytic pathway to accelerate thrombus resolution and can be used to treat serious and life-threatening arterial and venous thrombosis in neonates and children. The main disadvantage of these drugs is the risk of bleeding associated with their use. This article reviews the fibrinolytic pathway and discusses the current agents available for thrombolytic therapy, as well as indications for their use, dosing regimens, safety, and efficacy.

RECENT FINDINGS

There is great variation in the drug dosing regimens used for thrombolysis and in the incidence of bleeding complications that have been reported in pediatric series. Increased experience with these drugs, appropriate patient selection, and careful monitoring appear to have reduced the risk of major bleeding over time. The use of thrombolysis for occlusive deep vein thrombosis, in attempt to reduce the long-term complication of postthrombotic syndrome, is controversial and deserves further investigation.

SUMMARY

The use of thrombolytic therapy in pediatrics has increased over the past two decades. Urokinase and recombinant tissue plasminogen activator are the currently available thrombolytic agents. Catheter-related arterial thrombi that threaten life, organ or limb are the most common indication for their use. There is a tremendous need for well designed clinical studies to improve the safety and efficacy of these drugs in neonates and children.

Risk factors for post-thrombotic syndrome in patients with a first deep venous thrombosis

BACKGROUND

Post-thrombotic syndrome (PTS) is a chronic complication of deep venous thrombosis (DVT).

OBJECTIVES

To determine the risk of PTS after DVT and to assess risk factors for PTS.

METHODS

Patients were recruited from the Multiple Environmental and Genetic Assessment (MEGA) study of risk factors for venous thrombosis. Consecutive patients who suffered a first DVT of the leg were included in a follow-up study. All patients completed a questionnaire and DNA was obtained. PTS was ascertained in a structured interview using a clinical classification score.

RESULTS

The 1-year cumulative incidence of PTS was 25% and 7% for severe PTS. Elastic compression stockings were prescribed in 1412 (85%) patients. The majority used their stockings every day. Women were at an increased risk compared with men [risk ratio (RR) 1.5, 95% confidence interval (CI) 1.3-1.8]. Similarly, obese patients had a 1.5-fold increased risk of PTS compared with normal weight patients (RR 1.5, 95% CI 1.2-1.9), with a 1-year cumulative incidence of 34% compared with 22%. Patients who already had varicose veins had an increased risk (RR 1.5, 95% CI 1.2-1.8) of PTS. DVT in the femoral and iliac vein was associated with a 1.3-fold increased risk of PTS compared with popliteal vein thrombosis (RR 1.3, 95% CI 1.1-1.6). Patients over 60 years were less likely to develop PTS than patients below the age of 30 (RR 0.6, 95% CI 0.4-0.9). Malignancy, surgery, minor injury, plaster cast, pregnancy or hormone use did not influence the risk of PTS neither did factor (F)V Leiden nor the prothrombin 20210A mutation.

CONCLUSIONS

PTS is a frequent complication of DVT, despite the widespread use of elastic compression stockings. Women, obese patients, patients with proximal DVT and those with varicose veins have an increased risk of PTS, whereas the elderly appeared to have a decreased risk.

Low molecular weight heparin for prevention of venous thromboembolism in patients with lower-leg immobilization

BACKGROUND

Immobilization of the lower leg is associated with venous thromboembolism. Low molecular weight heparin (LMWH) is an anticoagulant treatment which might be used in adult patients with lower-leg immobilization to prevent deep venous thrombosis and its complications.

OBJECTIVES

To investigate the current literature on thromboprophylactic practice for patients with lower-limb injuries who are immobilized in plaster casts or braces, to assess the need for concrete guidelines, and to assess whether it is possible to come to an evidence-based conclusion.

SEARCH STRATEGY

The Cochrane Peripheral Vascular Disease Group searched their Specialized Register (last searched 20 May 2008) and the Central Register of Controlled Trials (CENTRAL) (last searched The Cochrane Library 2008, Issue 2). We searched MEDLINE (until May 2008) and EMBASE (until May 2008) and reference lists of articles. We contacted pharmaceutical companies of LMWHs for relevant studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that described thromboprophylaxis by means of LMWH compared with no prophylaxis or placebo in adult patients with lower-leg immobilization. Immobilization was by means of a plaster cast or brace.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. The review authors contacted the trial authors for additional information if required. Statistical analysis was carried out using Review Manager (RevMan 5).

MAIN RESULTS

We included six RCTs fulfilling the above criteria with a total of 1490 patients. We found an incidence of venous thromboembolism ranging from 4.3% to 40%, in patients who had a leg injury that had been immobilized in a plaster cast or a brace for at least one week and who received no prophylaxis, or placebo. This number was significantly lower in patients who received daily subcutaneous injections of LMWH during immobilization (event rates ranging from 0% to 37%; odds ratio (OR) 0.49; fixed 95% confidence interval (CI) 0.34 to 0.72; with minimal evidence of heterogeneity with an I(2) of 20%, P = 0. 29). Comparable results were seen in the following subcategories: operated patients, conservatively treated patients, patients with fractures, patients with soft-tissue injuries, patients with proximal thrombosis, patients with distal thrombosis and patients with below-knee casts. Complications of major bleeding events were extremely rare (0.3%) and there were no reports of heparin-induced thrombocytopenia.

AUTHORS' CONCLUSIONS

Use of LMWH in outpatients significantly reduces VTE when immobilization of the lower leg is required.

Determinants of health-related quality of life during the 2 years following deep vein thrombosis

BACKGROUND/OBJECTIVES

We prospectively measured change in quality of life (QOL) during the 2 years after a diagnosis of deep vein thrombosis (DVT) and evaluated determinants of QOL, including development of the post-thrombotic syndrome (PTS).

PATIENTS/METHODS

Consecutive patients with acute DVT were recruited from 2001 to 2004 at eight hospitals in Canada. At study visits at baseline, and 1, 4, 8, 12 and 24 months, clinical data were collected, standardized PTS assessments were performed, and QOL questionnaires were self-completed. Generic QOL was measured using the Short-Form Health Survey-36 (SF-36) questionnaire. Venous disease-specific QOL was measured using the Venous Insufficiency Epidemiological and Economic Study (VEINES)-QOL/Sym questionnaire. The change in QOL scores over a 2-year follow-up was assessed. The influence of PTS and other characteristics on QOL at 2 years was evaluated using multivariable regression analyses.

RESULTS

Among the 387 patients recruited, the average age was 56 years, two-thirds were outpatients, and 60% had proximal DVT. The cumulative incidence of PTS was 47%. On average, QOL scores improved during follow-up. However, patients who developed PTS had lower scores at all visits and significantly less improvement in QOL over time (P-values for PTS*time interaction were 0.001, 0.012, 0.014 and 0.006 for PCS, MCS, VEINES-QOL and VEINES-Sym). Multivariable regression analyses showed that PTS (P < 0.0001), age (P = 0.0009), proximal DVT (P = 0.01) and inpatient status (P = 0.04) independently predicted 2-year SF-36 PCS scores. PTS alone independently predicted 2-year VEINES-QOL (P < 0.0001) and VEINES-Sym (P < 0.0001) scores.

CONCLUSIONS

Development of PTS is the principal determinant of health-related QOL 2 years after DVT. Our study provides prognostic information on patient-reported outcomes after DVT and emphasizes the need for effective prevention and treatment of the PTS.

Current treatment of acute lower extremity deep venous thrombosis

The long-term complications of acute deep venous thrombosis (DVT) include recurrence, increased mortality, and the development of the postthrombotic syndrome. Rates of recurrent venous thromboembolism (VTE) are elevated in patients with cancer and thrombophilia. Heparin, administered either as unfractionated or low-molecular weight, is indicated for at least five days for acute DVT. Long-term treatment is currently a vitamin K antagonist with a variable duration depending on the etiology of the DVT and risk of bleeding. Novel anticoagulant agents that target factor Xa and directly inhibit thrombin are being studied in clinical trials and may one day replace vitamin K antagonists for the long-term treatment of VTE. Interventional approaches such as percutaneous mechanical thrombectomy have the potential to reduce clot burden in acute DVT with lower bleeding risks and help prevent development of the postthrombotic syndrome, a common and potentially debilitating complication of DVT.

Physical activity in patients with deep venous thrombosis: a systematic review

OBJECTIVES

We performed a systematic review to assess the benefits or risks of physical activity in patients with an acute or previous DVT of the leg.

DATA SOURCES

PubMed, EMBASE and Science Citation Index were searched without language restrictions up to July 2007. Bibliographies of retrieved articles and personal files were also searched.

REVIEW METHODS

Randomized trials and prospective cohort studies that included patients with acute or previous DVT, described an exercise intervention or exercise exposure, and described any related clinical outcome were selected. Data were independently extracted by 2 investigators.

RESULTS

Seven randomized trials and two prospective observational studies were included. Early exercise, compared with bed rest, was associated with a similar short-term risk of pulmonary embolism in patients with acute DVT and led to more rapid resolution of limb pain. In patients with acute DVT, a 6 month daily walking program led to similar degrees of vein recanalization and improvement in quality of life as controls. In patients with previous DVT, 30 min of vigorous treadmill exercise did not worsen venous symptoms and improved calf muscle flexibility; a 6 month exercise training program improved calf muscle strength and pump function; and high levels of physical activity at one month tended to be associated with reduced severity of postthrombotic symptoms during the subsequent 3 months.

CONCLUSIONS

Early walking exercise is safe in patients with acute DVT and may help to reduce acute symptoms. Exercise training does not increase leg symptoms acutely in patients with a previous DVT and may help to prevent or improve the postthrombotic syndrome.

Compression stockings to prevent post-thrombotic syndrome: a role for anticoagulation clinics?

Anticoagulation clinics are increasingly used to manage oral anticoagulant therapy in patients with venous thromboembolic disease (VTE). Such clinics may be in a position to assume greater responsibility for other aspects of the long-term management of VTE, including prevention of post-thrombotic syndrome (PTS). Current guidelines suggest use of graduated elastic compression stockings with a pressure of 30-40 mm Hg at the ankle for 2 years following the diagnosis of deep vein thrombosis (DVT) to prevent PTS. A survey of anticoagulation clinic providers was conducted to determine to what extent patients with DVT are prescribed compression stockings and by whom, and the degree of compression and duration of therapy prescribed. Survey results show a very low rate of use of compression stockings in patients with DVT, and limited adherence to current recommendations for strength and duration of use. We believe that healthcare providers practicing in anticoagulation clinics should be encouraged to expand their scope of practice into a more comprehensive model of antithrombosis care, including prevention of PTS. By doing so, the extent of use of compression stockings might be increased, and adherence to current guidelines for strength and duration of compression might be improved.

Catheter-directed Venous Thrombolysis in acute iliofemoral vein thrombosis--the CaVenT study: rationale and design of a multicenter, randomized, controlled, clinical trial (NCT00251771)

BACKGROUND

The conventional treatment of acute deep vein thrombosis (DVT) is anticoagulation and compression therapy, as recommended in the international guidelines. Anticoagulation prevents recurrent venous thrombosis, pulmonary embolism, and death. Compression therapy reduces the risk of developing long-term sequelae, that is, postthrombotic syndrome (PTS). Evaluation of systemic thrombolysis has shown effective thrombolysis and a likely reduction in PTS but at the cost of increased risk of bleeding complications. Catheter-directed thrombolysis (CDT) was introduced for rapid removal of thrombi and salvage of venous valves with less systemic thrombolytic effect, and is being offered to selected patients with iliofemoral DVT to prevent development of PTS. Case series have shown technical and thrombolytic success; however, no randomized studies have evaluated the long-term clinical effects of venous CDT. The aim of the CaVenT study is to investigate the role of adjunctive CDT by evaluating its clinical efficacy and safety compared with conventional treatment alone in patients with acute iliofemoral DVT.

METHODS

The CaVenT study is an open, randomized, controlled, clinical trial. We plan to include 200 patients who will receive either CDT, in addition to conventional treatment, or conventional treatment alone. The primary outcome measures are patency at 6 months and prevalence of PTS at 2 years.

CONCLUSION

Implementation of the CaVenT study will be a contribution toward evidence-based medicine in the treatment of acute proximal DVT of the leg. Any documentation of improved functional outcome will have a significant impact on clinical practice for this patient group and may lead to a modification of existing international guidelines.

Molecular characterization of post-thrombotic syndrome

The post-thrombotic syndrome represents a poorly understood and significant vascular health problem. This review focuses on our current understanding of the pathogenesis of post-thrombotic syndrome. We emphasize the cellular and molecular mechanisms that are responsible for the critical components of post-thrombotic syndrome. These include the initiation of deep venous thrombosis, the pathogenesis of elevated venous pressure, and the factors responsible for nonhealing of venous stasis ulcers.

Effectiveness of compression stockings to prevent the post-thrombotic syndrome (the SOX Trial and Bio-SOX biomarker substudy): a randomized controlled trial

Background

Post thrombotic syndrome (PTS) is a burdensome and costly complication of deep venous thrombosis (DVT) that develops in 20–40% of patients within 1–2 years after symptomatic DVT. Affected patients have chronic leg pain and swelling and may develop ulcers. Venous valve disruption from the thrombus itself or thrombus-associated mediators of inflammation is considered to be a key initiating event for the development of venous hypertension that often underlies PTS. As existing treatments for PTS are extremely limited, strategies that focus on preventing the development of PTS in patients with DVT are more likely to be effective and cost-effective in reducing its burden. Elastic compression stockings (ECS) could be helpful in preventing PTS; however, data on their effectiveness are scarce and conflicting.

Methods/Design

The SOX Trial is a randomized, allocation concealed, double-blind multicenter clinical trial. The objective of the study is to evaluate ECS to prevent PTS. A total of 800 patients with proximal DVT will be randomized to one of 2 treatment groups: ECS or placebo (inactive) stockings worn on the DVT-affected leg daily for 2 years. The primary outcome is the incidence of PTS during follow-up. Secondary outcomes are severity of PTS, venous thromboembolism (VTE) recurrence, death from VTE, quality of life and cost-effectiveness. Outcomes will be evaluated during 6 clinic visits and 2 telephone follow ups. At baseline, 1 and 6 months, blood samples will be obtained to evaluate the role of inflammatory mediators and genetic markers of thrombophilia in the development of PTS (Bio-SOX substudy).

Discussion

The SOX Trial will be the largest study and the first with a placebo control to evaluate the effectiveness of ECS to prevent PTS. It is designed to provide definitive data on the effects of ECS on the occurrence and severity of PTS, as well as DVT recurrence, cost-effectiveness and quality of life. This study will also prospectively evaluate the predictive role of biomarkers that are reflective of putative underlying pathophysiological mechanisms in the development of clinical PTS. As such, our results will impact directly on the care of patients with DVT.

Trial Registration

NCT00143598 and ISRCTN71334751

The importance of monophasic Doppler waveforms in the common femoral vein: a retrospective study

OBJECTIVE

The purpose of this study was to assess the importance of monophasic waveforms encountered in the common femoral vein during deep venous thrombosis evaluation by a retrospective review of lower extremity venous Doppler (VD) sonography and correlative studies, such as computed tomography (CT) and magnetic resonance imaging.

METHODS

A retrospective review was conducted of lower extremity VD studies performed from September 1, 2000, through September 1, 2005. All satisfactory VD studies, which were in compliance with the Intersocietal Commission for the Accreditation of Vascular Laboratories standard protocol, were evaluated for the presence of monophasic waveforms and correlated with CT of the abdomen and pelvis. Studies were evaluated for the causes of monophasic waveforms. Patients younger than 18 years were excluded.

RESULTS

A total of 2963 VD examinations were reviewed. One hundred twenty-four of 2963 showed monophasic waveforms. Eighty-nine of the 124 had additional CT examinations within 1 week; 19 had CT within 2 months; and 16 had no additional examinations. Forty-seven of 124 cases revealed deep venous thrombosis extending into the iliac veins, of which 23 were identified by VD sonography; 26 were due to extrinsic compression; 6 showed a hypoplastic or stenosed common iliac vein; and the remaining 45 had no apparent causes for the monophasic waveforms.

CONCLUSIONS

Monophasic waveforms in the common femoral veins are reliable indicators of proximal venous obstruction. Because iliac vein thrombosis is clinically important, we recommend routine sonographic evaluation of external iliac veins in the presence of monophasic waveforms and CT or magnetic resonance imaging, if necessary, to determine the cause of the monophasic waveforms.

Latest medical treatment strategies for venous thromboembolism

Anticoagulant therapy with unfractionated heparin (UFH) followed by warfarin prevents thrombus extension, reduces the risk of recurrent thrombosis and prevents death in patients with venous thromboembolism (VTE). Low-molecular-weight heparin (LMWH) has replaced UFH as the preferred initial anticoagulant therapy for VTE because it is as effective and safe as UFH, but does not require laboratory monitoring and is less likely to cause immune thrombocytopenia and osteoporosis. More recently, fondaparinux has been shown to be an effective and safe alternative to LMWH and several new parenteral anticoagulants are being evaluated. The most important unmet need in the anticoagulant management of VTE is a replacement for warfarin. New oral anticoagulants that selectively target individual steps in the coagulation cascade have been shown to be effective for the long-term treatment of VTE in Phase II and III trials and are likely to become available in the near future.