Determinants of chronic venous disease after acute deep venous thrombosis

Time-dependent ultrastructural changes during venous thrombogenesis and thrombus resolution

BACKGROUND

Deep vein thrombosis is a common vascular event that can result in debilitating morbidity and even death due to pulmonary embolism. Clinically, patients with faster resolution of a venous thrombus have improved prognosis, but the detailed structural information regarding changes that occur in a resolving thrombus over time is lacking.

OBJECTIVES

To define the spatial-morphologic characteristics of venous thrombus formation, propagation, and resolution at the submicron level over time.

METHODS

Using a murine model of stasis-induced deep vein thrombosis along with scanning electron microscopy and immunohistology, we determine the specific structural, compositional, and morphologic characteristics of venous thrombi formed after 4 days and identify the changes that take place during resolution by day 7. Comparison is made with the structure and composition of venous thrombi formed in mice genetically deficient in plasminogen activator inhibitor type 1.

RESULTS

As venous thrombus resolution progresses, fibrin exists in different structural forms, and there are dynamic cellular changes in the compositions of leukocytes, platelet aggregates, and red blood cells. Intrathrombus microvesicles are present that are not evident by histology, and red blood cells in the form of polyhedrocytes are an indicator of clot contraction. Structural evidence of fibrinolysis is observed early during thrombogenesis and is accelerated by plasminogen activator inhibitor type 1 deficiency.

CONCLUSION

The results reveal unique, detailed ultrastructural and compositional insights along with documentation of the dynamic changes that occur during accelerated resolution that are not evident by standard pathologic procedures and can be applied to inform diagnosis and effectiveness of thrombolytic treatments to improve patient outcomes.

Management of iliofemoral deep vein thrombosis with distal involvement

Endovascular treatment of iliofemoral deep vein thrombosis (IF DVT) can become more complex when thrombus extends below the knee. This article discusses various techniques that can be used to treat IF DVT with distal involvement.

Effects of Deep Venous Thrombosis Treatments on Early and Long-term Quality of Life: Medical Therapy vs. Systemic Thrombolysis vs. Pharmacomechanical Thrombolysis

OBJECTIVES

The present study aimed to compare the effects of medical therapy (MT), systemic thrombolysis (ST), and pharmacomechanical thrombolysis (PMT) methods used in our clinic for the treatment of deep venous thrombosis (DVT) on symptom reduction, the incidence of post-thrombotic syndrome (PTS) development, and quality of life.

METHODS

Data from160 patients diagnosed with acute DVT between January 2012 and May 2021 and treated and followed up in our clinic were retrospectively analyzed. The patients were divided into three groups according to treatment method. The patients who received MT treatment were defined as Group 1, anticoagulant treatment after ST as Group 2, and anticoagulant treatment after PMT as Group 3. The patients were called to the outpatient clinic, informed consent was obtained, EuroQol-5D-3 L (EQ-5D-3 L) scoring and Villalta scoring were performed, and anamnesis was taken.

RESULTS

A total of 160 patients were included, with 71 (44.4%) patients in Group 1, 45 (28.1%) in Group 2, and 44 (27.5%) in Group 3. The mean age was 48.9 ± 14.9 years for Group 1, 42.2 ± 10.8 for Group 2, and 29.0 ± 7.2 for Group 3. When the time to return to normal life and the EQ-5D-3 L score index were compared, the differences between Groups 1 and 2 and between Groups 1 and 3 were statistically significant (P = .000 and P = .000, respectively). However, the differences between Groups 2 and 3 were statistically insignificant (P = .213 andp = .074, respectively). When Villalta scores and EQ Visual Analogue Scale (EQ-VAS) scores were compared between groups, the difference between all groups was statistically significant (P = .000).

CONCLUSIONS

The medical treatment alone was observed to be insufficient in terms of symptomatic improvement, development of PTS, quality of life, and long-term complications. When the ST and PMT groups were compared, it was determined that PMT treatment was more advantageous in terms of EQ-VAS score and PTS development, although there was no statistical difference regarding complications, such as return to normal life and long-term quality of life, the incidence of recurrent DVT development, and pulmonary thromboembolism incidence.

Insights from experimental post-thrombotic syndrome and potential for novel therapies

Post-thrombotic syndrome (PTS) is an end stage manifestation of deep vein thrombosis. This is an inherently inflammatory process, with consequent fibrosis. Multiple cellular types are involved, and are likely driven by leukocytes. Herein, we review the current gaps in therapy, and insights from rodent models of venous thrombosis that suggest possible targets to treat and prevent PTS.

Ultrasound Aspects and Recanalization Rates in Patients with Lower-Limb Deep Venous Thrombosis Treated with Rivaroxaban

BACKGROUND

In this article, we report the ultrasound aspects and recanalization rates of patients with deep venous thrombosis (DVT) in the lower limbs treated with the rivaroxaban, focusing on the recanalization rate and the ultrasonographic aspects.

METHODS

This was a prospective and consecutive cohort study of patients admitted with DVT who were submitted to treatment with rivaroxaban for 6 months at the Division of Vascular and Endovascular Surgery, Hospital do Servidor Público Estadual, São Paulo, Brazil, between March 2016 and July 2018.

RESULTS

Fifty-one patients with DVT were admitted to the Vascular Surgery Department and received rivaroxaban for 6 months. The follow-up time was 360 days. Analyses were performed at 180 and 360 days. The rate of total venous recanalization at 360 days was 76.4% (39 patients). The incidence of partial venous recanalization was 23.5% (12 patients). At the first month, 11 patients (21.7%) continued with total occlusion of the vein, with 4 patients (6.5%) with no residual thrombi. However, at 6 months, only 2 patients (2.2%) continued with total occlusion of the vein, with 26 patients (47.8%) with no residual thrombi. At 12 months, there were 39 patients (76.4%) with no residual thrombi. Univariate and multivariate logistic regression identified the following factors related to total venous recanalization: the absence of popliteal vein reflux (odds ratio [OR], 0.386; P = 0.007), no residual thrombi (OR, 3.213; P = 0.008), femoropopliteal clot length at 1 month (OR, 3.021; P = 0.016), femoropopliteal clot length at 6 months (OR, 2.234; P = 0.008). The incidence of post-thrombotic syndrome (PTS) at 12 months was 8.3%.

CONCLUSIONS

In this study, patients who received oral rivaroxaban displayed satisfactory total vein recanalization rate after 6 months and 12 months. The factors associated with better total recanalization rates were the absence of popliteal vein reflux, the absence of residual thrombi in the veins, femoropopliteal clot length at 1 month (OR, 3.021; P = 0.016), and femoropopliteal clot length at 6 months (OR, 2.234; P = 0.008). Moreover, the incidence of PTS at 12 months was 8.3%.

Relationships between the use of pharmacomechanical catheter-directed thrombolysis, sonographic findings, and clinical outcomes in patients with acute proximal DVT: Results from the ATTRACT Multicenter Randomized Trial

Few studies have documented relationships between endovascular therapy, duplex ultrasonography (DUS), post-thrombotic syndrome (PTS), and quality of life (QOL). The Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) trial randomized 692 patients with acute proximal deep vein thrombosis (DVT) to receive anticoagulation or anticoagulation plus pharmacomechanical catheter-directed thrombolysis (PCDT). Compression DUS was obtained at baseline, 1 month and 12 months. Reflux DUS was obtained at 12 months in a subset of 126 patients. Clinical outcomes were collected over 24 months. At 1 month, patients who received PCDT had less residual thrombus compared to Control patients, evidenced by non-compressible common femoral vein (CFV) (21% vs 35%, p < 0.0001), femoral vein (51% vs 70%, p < 0.0001), and popliteal vein (61% vs 74%, p < 0.0001). At 12 months, in the ultrasound substudy, valvular reflux prevalence was similar between groups (85% vs 91%, p = 0.35). CFV non-compressibility at 1 month was associated with higher rates of any PTS (61% vs 46%, p < 0.001), a higher incidence of moderate-or-severe PTS (30% vs 19%, p = 0.003), and worse QOL (difference 8.2 VEINES-QOL (VEnous INsufficiency Epidemiological and Economic Study on Quality of Life) points; p = 0.004) at 24 months. Valvular reflux at 12 months was associated with moderate-or-severe PTS at 24 months (30% vs 0%, p = 0.01). In summary, PCDT results in less residual thrombus but does not reduce venous valvular reflux. CFV non-compressibility at 1 month is associated with more PTS, more severe PTS, and worse QOL at 24 months. Valvular reflux may predispose to moderate-or-severe PTS. ClinicalTrials.gov Identifier NCT00790335.

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.

Inhibition of prolyl hydroxylase domain proteins selectively enhances venous thrombus neovascularisation

BACKGROUND

Hypoxia within acute venous thrombi is thought to drive resolution through stabilisation of hypoxia inducible factor 1 alpha (HIF1α). Prolyl hydroxylase domain (PHD) isoforms are critical regulators of HIF1α stability. Non-selective inhibition of PHD isoforms with l-mimosine has been shown to increase HIF1α stabilisation and promote thrombus resolution.

OBJECTIVE

The aim of this study was to investigate the therapeutic potential of PHD inhibition in venous thrombus resolution.

METHODS

Thrombosis was induced in the inferior vena cava of mice using a combination of flow restriction and endothelial activation. Gene and protein expression of PHD isoforms in the resolving thrombus was measured by RT-PCR and immunohistochemistry. Thrombus resolution was quantified in mice treated with pan PHD inhibitors AKB-4924 and JNJ-42041935 or inducible all-cell Phd2 knockouts by micro-computed tomography, 3D high frequency ultrasound or endpoint histology.

RESULTS

Resolving venous thrombi demonstrated significant temporal gene expression profiles for PHD2 and PHD3 (P < 0.05), but not for PHD1. PHD isoform protein expression was localised to early and late inflammatory cell infiltrates. Treatment with selective pan PHD inhibitors, AKB-4924 and JNJ-42041935, enhanced thrombus neovascularisation (P < 0.05), but had no significant effect on overall thrombus resolution. Thrombus resolution or its markers, macrophage accumulation and neovascularisation, did not differ significantly in inducible all-cell homozygous Phd2 knockouts compared with littermate controls (P > 0.05).

CONCLUSIONS

This data suggests that PHD-mediated thrombus neovascularisation has a limited role in the resolution of venous thrombi. Directly targeting angiogenesis alone may not be a viable therapeutic strategy to enhance venous thrombus resolution.

Development of a clinical prediction model for the postthrombotic syndrome in a prospective cohort of patients with proximal deep vein thrombosis

Essentials We developed a prediction model for postthrombotic syndrome (PTS) after deep vein thrombosis (DVT). High risk predictors were iliac vein DVT, BMI>35 and moderate-severe Villalta category. Patients with a score ≥4 had an odds ratio of 5.9 (95% CI 2.1-16.6) for PTS. SOX-PTS score may select DVT patients for close monitoring or aggressive strategies to treat DVT.

SUMMARY

Background Postthrombotic syndrome (PTS) is a chronic complication that develops in 20-50% of patients after deep vein thrombosis (DVT). Although individual risk factors for PTS have been characterized, the ability to predict which DVT patients are likely to develop PTS remains limited. Objective To develop a clinical prediction score for PTS in patients with DVT. Methods The derivation cohort consisted of participants in the SOX Trial, a randomized double-blind placebo-controlled trial of elastic compression stockings versus placebo stockings worn for 2 years after DVT to prevent PTS in patients with a first proximal DVT, enrolled in 24 community and tertiary-care hospitals from 2004 to 2010. Multivariable logistic regression analysis of baseline characteristics was performed. The outcome was the occurrence of PTS, diagnosed starting from 6 months or later according to Ginsberg's criteria. Results Seven hundred and sixty-two patients were included in the analysis. The median follow-up was 728 days. The model includes three independent predictors, and has a range of possible scores from 0 to 5. High-risk predictors were: index DVT in the iliac vein; body mass index of ≥ 35 kg m-2 ; and moderate-severe Villalta severity category at DVT diagnosis. As compared with patients with a score of 0, those with a score of ≥ 4 had an odds ratio of 5.9 (95% confidence interval 2.1-16.6) for developing PTS. Conclusions To our knowledge, this is the first clinical prediction score for PTS. We identified three independent predictors that, when combined, predicted PTS risk after a first proximal DVT. The SOX-PTS score requires external validation before it can be considered for clinical use.

Serpins in Venous Thrombosis and Venous Thrombus Resolution

Several serpins function as potent inhibitors of thrombolytic serine proteases. Venous thrombosis is a common and debilitating condition whose incidence is on the rise. Studies using genetically modified mice and inhibitors have shown that the plasminogen activator inhibitors (PAI), PAI-1 and PAI-2, are primary regulators of plasminogen activation and contribute to regulating the resolution of experimental venous thrombi, via inflammatory mechanisms, vascular remodeling, and inhibition of fibrinolysis. Therapies to accelerate venous thrombus resolution would be beneficial, since delayed or incomplete clot resolution frequently leads to postthrombotic syndrome, a long-term complication associated with debilitating limb swelling, pain, and recurrent skin ulceration. Here we describe a useful and reproducible mouse model for the study of venous thrombus resolution involving ligation of the inferior vena cava and elucidation of the molecular and cellular determinants of venous thrombus formation and resolution.

The predictive value of markers of fibrinolysis and endothelial dysfunction in the post thrombotic syndrome

The post thrombotic syndrome (PTS) develops in 20–40% of deep venous thrombosis (DVT) patients. Risk factors for PTS have not been well elucidated. Identification of risk factors would facilitate individualised risk assessment for PTS. We conducted a systematic review to determine whether biomarkers of fibrinolysis or endothelial dysfunction can predict the risk for PTS among DVT patients. Studies were identified by searching the electronic databases PubMed, EMBASE, Scopus and Web of science. We included studies published between 1990 and 2013, measured biomarker levels in adult DVT patients, and reported rates of PTS development. Fourteen studies were included: 11 investigated the association between D-dimer and PTS; three examined fibrinogen; two measured von Willebrand factor; one measured plasminogen activator inhibitor-1; one assessed ADAMTS-13 (A Disintegrin and Metalloprotease with Thrombospondin type 1 repeats) and one measured factor XIII activity. Studies varied with regards to inclusion criteria, definition of PTS, time point and method of biomarker measurement. We were unable to meta-analyse results due to marked clinical heterogeneity. Descriptively, a significant association with PTS was found for D-dimer in four studies and factor XIII in one study. Further prospective research is needed to elucidate whether these markers might be useful to predict PTS development.

Risk factors of postthrombotic syndrome before and after deep venous thrombosis treatment

Postthrombotic syndrome is the most common complication after deep venous thrombosis. Postthrombotic syndrome is a debilitating disease and associated with decreased quality of life and high healthcare costs. Postthrombotic syndrome is a chronic disease, and causative treatment options are limited. Prevention of postthrombotic syndrome is therefore very important. Not all patients develop postthrombotic syndrome. Risk factors have been identified to try to predict the risk of developing postthrombotic syndrome. Age, gender, and recurrent deep venous thrombosis are factors that cannot be changed. Deep venous thrombosis location and extent seem to predict severity of postthrombotic syndrome and are potentially suitable as patient selection criteria. Residual thrombosis and reflux are known to increase the incidence of postthrombotic syndrome, but are of limited use. More recently developed treatment options for deep venous thrombosis, such as new oral factor X inhibitors and catheter-directed thrombolysis, are available at the moment. Catheter-directed thrombolysis shows promising results in reducing the incidence of postthrombotic syndrome after deep venous thrombosis. The role of new oral factor X inhibitors in preventing postthrombotic syndrome is still to be determined.

Surgical Technique for Deep Venous Reflux Suppression in Femoral Vein Duplication

BACKGROUND

Deep venous surgery is a challenging field with limited indications. Femoral vein duplication (FVD) is a frequent anatomical variant (55% prevalence). The aim was to describe a simple technique for managing deep venous reflux in FVD, when just one of the two segments exhibits deep venous reflux.

METHODS

The technique consists of closing the refluxing femoral branch with a titanium clip. In this way abolition of reflux along the duplicated vessel is achieved, together with the restoration of femoral vein drainage.

RESULTS

The technique is feasible and associated with improvement in limb haemodynamics.

CONCLUSIONS

Thanks to the high prevalence of FVD, the proposed technique provides an opportunity to treat a larger number of cases affected by primary or post-thrombotic deep venous reflux.

Cancer-Associated Thrombosis: Regulatory Mechanisms and Emerging Directions

Venous thrombosis is a common complication in cancer patients, and some cancer chemotherapies are associated with an increased risk of venous thromboembolism. The regulatory mechanisms that control thrombus formation and subsequent resolution in patients with cancer, however, are incompletely understood, and novel treatments for cancer-associated thrombosis may arise from a better understanding of such mechanisms. In this chapter, pathways that regulate cancer-associated thrombus formation are outlined, and the effects of anti-angiogenic cancer chemotherapies on venous thrombus resolution are highlighted. Potentially pro-thrombotic effects of anti-angiogenic agents are important considerations when managing the complications of venous thrombosis in cancer patients.

Association between inflammation biomarkers, anatomic extent of deep venous thrombosis, and venous symptoms after deep venous thrombosis

OBJECTIVE

Inflammation may play a role in pathogenesis of venous thromboembolism, but the nature of this relationship is not yet understood. The objective of this study was to assess whether inflammation marker levels measured at diagnosis of deep venous thrombosis (DVT) and change in levels during the first month after DVT are associated with anatomic extent of DVT and severity of venous signs and symptoms at baseline and 1 month.

METHODS

The BioSOX study is a biomarker substudy of the Compression Stockings to Prevent the Post-Thrombotic Syndrome (SOX) trial, a multicenter, randomized controlled trial that included patients with a first, acute, symptomatic, proximal DVT. Blood samples were collected from participants at baseline and 1 month, and C-reactive protein (CRP), intercellular adhesion molecule 1, interleukin (IL)-6, and IL-10 were measured by established assays. Linear regression was used to assess the association between continuous log-transformed baseline biomarker levels and anatomic extent of DVT, classified as iliac or common femoral DVT vs femoral or popliteal DVT (reference). Proportional odds ordinal logistic regression models were used to analyze the association between biomarker level and Villalta score (as a measure of severity of venous signs and symptoms) at baseline and 1 month.

RESULTS

Among 717 patients, 60.2% were male, and the mean age was 55.2 years. There was a significant association between more extensive DVT (common femoral or iliac) and levels of CRP and IL-6 at DVT diagnosis. Median (interquartile range) CRP level was 11.6 mg/L (3.84-39.5) in patients with common femoral or iliac DVT vs 6.86 mg/L (3.11-22) in patients with popliteal or femoral DVT, and median IL-6 level was 6.36 pg/mL (1.09-14.37) vs 4.40 pg/mL (2.35-8.27), respectively. These differences were statistically significant in linear regression analyses. In addition, compared with those in the lowest quartile, each higher quartile of baseline CRP concentration was associated with an odds ratio of 2.89 (1.93-4.33) for having a more severe Villalta category at baseline and 1.98 (1.28-3.08) for having a more severe Villalta category 1 month after DVT. Higher baseline levels of IL-6 were associated with Villalta severity category at baseline (odds ratio, 2.40 [1.61-3.59]). Change in biomarker levels during the first month after DVT was not strongly associated with the 1-month Villalta score.

CONCLUSIONS

Levels of CRP and IL-6 at DVT diagnosis were associated with thrombotic disease burden, as measured by DVT extent, and severity of DVT symptoms and signs. Further studies are required to more fully elucidate the role of inflammation in DVT and its clinical course.

Predictive value of markers of inflammation in the postthrombotic syndrome: a systematic review: inflammatory biomarkers and PTS

BACKGROUND

The postthrombotic syndrome (PTS) is a chronic complication of deep vein thrombosis (DVT). Inflammation may contribute to its pathophysiology.

OBJECTIVES

We conducted a systematic review of studies that analyzed the association between biomarkers of inflammation and PTS in DVT patients.

METHODS

The electronic databases PubMed, EMBASE, Medline, Scopus and Web of Science were searched for studies published until March 2015 that measured blood inflammation biomarker levels in adult DVT patients and reported their association with PTS development. Two reviewers independently performed full text assessment and data extraction.

RESULTS

Ten studies were included. Nine reported on the association between C-reactive protein and PTS; Interleukin (IL)-6 was measured in six studies; IL-8 in four studies; Intracellular adhesion molecule (ICAM)-1 in three studies; IL-10 and vascular cell adhesion molecule-1 in two studies; and monocyte chemotactic protein-1, matrix metalloprotease-9, P-Selectin, tumor necrosis factor α and erythrocyte sedimentation rate were measured in one study. Studies differed in terms of populations included, exclusion criteria, methods used for biomarker measurement and statistical measures of association between biomarkers and PTS. We were able to metaanalyze results only for IL-6 and found no significant association. Descriptively, ICAM-1 was significantly associated with PTS in two out of three studies that measured it. Other biomarkers did not demonstrate a significant association with PTS.

CONCLUSIONS

Our systematic review found conflicting results regarding the role of inflammatory biomarkers as predictors of PTS. ICAM -1 appears to be a promising marker for further investigation.

Inflammation markers and their trajectories after deep vein thrombosis in relation to risk of post-thrombotic syndrome

BACKGROUND

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

OBJECTIVE

In the BioSOX study, we investigated whether inflammation markers predict the risk of PTS after DVT.

METHODS

We measured C-reactive protein (CRP), ICAM-1, interleukin (IL)-6, and IL-10, at baseline, and 1 month and 6 months after a first proximal DVT, among 803 participants in the SOX trial. Participants were prospectively followed for 24 months for development of PTS.

RESULTS

Median CRP levels at 1 month, ICAM-1 levels at baseline, 1 month and 6 months, IL-6 levels at 1 month and 6 months and IL-10 levels at 6 months were higher in patients who developed PTS than in those who did not. Multivariable regression with the median as a cutoff showed risk ratios (RRs) for PTS of 1.23 (95% confidence interval [CI] 1.05-1.45) and 1.25 (95% CI 1.05-1.48) for ICAM-1 at 1 month and 6 months, respectively, and 1.27 (95% CI 1.07-1.51) for IL-10 at 6 months. Quartile-based analysis demonstrated a dose-response association between ICAM-1 and PTS. ICAM-1 and IL-10 were also associated with PTS severity. Analysis of biomarker trajectories after DVT demonstrated an association between the highest-trajectory group of ICAM-1 and PTS.

CONCLUSIONS

In this prospective study, ICAM-1 over time was most consistently associated with the risk of PTS. Further study is required to confirm these findings and assess their potential clinical relevance.

Hemodynamic significance of collateral blood flow in chronic venous obstruction

Introduction

Complaints related to the post-thrombotic syndrome do not always correlate well with the extent of post-thrombotic changes on diagnostic imaging. One explanation might be a difference in development of collateral blood flow. The aim of this study is to investigate the hemodynamic effect of collateralisation in deep venous obstruction.

Methodology

Resting intravenous pressure of the common femoral vein was measured bilaterally in the supine position of patients with unilateral iliofemoral post-thrombotic obstruction. In addition, pressure in control limbs was also measured in the common femoral vein after sudden balloon occlusion in the external iliac vein.

Results

Fourteen patients (median age 42 years, 12 female) were tested. In eleven limbs post-thrombotic disease extended below the femoral confluence. Median common femoral vein pressure was 17.0 mmHg in diseased limbs compared to 12.8 mmHg in controls (p = 0.001) and 23.5 mmHg in controls after sudden balloon occlusion (p = 0.009). Results remained significant after correcting for non-occlusive post-thrombotic disease.

Conclusion

This study shows that common femoral vein pressure is increased in post-thrombotic iliofemoral deep venous obstruction, though not as much as after sudden balloon occlusion. The latter difference could explain the importance of collateralisation in deep venous obstructive disease and the discrepancy between complaints and anatomical changes; notwithstanding, the presence of collaterals does not eliminate the need for treatment.

Enhanced venous thrombus resolution in plasminogen activator inhibitor type-2 deficient mice

BACKGROUND

The resolution of deep vein thrombosis requires an inflammatory response and mobilization of proteases, such as urokinase-type plasminogen activator (uPA) and matrix metalloproteinases (MMPs), to degrade the thrombus and remodel the injured vein wall. Plasminogen activator inhibitor type 2 (PAI-2) is a serine protease inhibitor (serpin) with unique immunosuppressive and cell survival properties that was originally identified as an inhibitor of uPA.

OBJECTIVE

To investigate the role of PAI-2 in venous thrombus formation and resolution.

METHODS

Venous thrombus resolution was compared in wild-type C57BL/6, PAI-2(-/-) , and PAI-1(-/-) mice using the stasis model of deep vein thrombosis. Formed thrombi were harvested, thrombus weights were recorded, and tissue was analyzed for uPA and MMP activities, PAI-1 expression, and the nature of inflammatory cell infiltration.

RESULTS

We found that the absence of PAI-2 enhanced venous thrombus resolution, while thrombus formation was unaffected. Enhanced venous thrombus resolution in PAI-2(-/-) mice was associated with increased uPA activity and reduced levels of PAI-1, with no significant effect on MMP-2 and -9 activities. PAI-1 deficiency resulted in an increase in thrombus resolution similar to PAI-2 deficiency, but additionally reduced venous thrombus formation and altered MMP activity. PAI-2-deficient thrombi had increased levels of the neutrophil chemoattractant CXCL2, which was associated with early enhanced neutrophil recruitment.

CONCLUSIONS

These data identify PAI-2 as a novel regulator of venous thrombus resolution, which modulates several pathways involving both inflammatory and uPA activity mechanisms, distinct from PAI-1. Further examination of these pathways may lead to potential therapeutic prospects in accelerating thrombus resolution.

Deletion of cysteine-cysteine receptor 7 promotes fibrotic injury in experimental post-thrombotic vein wall remodeling

OBJECTIVE

Deep vein thrombosis (VT) can result in vein wall injury, which clinically manifests as post-thrombotic syndrome. Postinjury fibrosis may be modulated in part through cellular cysteine-cysteine receptor 7 (CCR7)-mediated events. We tested the hypothesis that late vein wall fibrotic remodeling is dependent on CCR7.

APPROACH AND RESULTS

CCR7(-/-) and C57BL/6 wild-type mice had inferior vena cava VT induced by nonstasis or stasis mechanisms. In both models, VT size was largest at day 1 and trended down by day 21, and CCR7(+) cells peaked at day 8 in wild-type mice. No significant differences in VT resolution were found in CCR7(-/-) as compared with wild type in either model. In the nonstasis VT model, vein wall changes consistent with fibrotic injury were evidenced by significant increases in collagen I, III, matrix metalloproteinase 2, and transforming growth factor-β gene expression, increases in α-smooth muscle actin and fibroblast specific protein-1 antigen, and total collagen at 8 days. Correspondingly, SM22α and fibroblast specific protein-1, but not DDR2(+) cells, were increased at 8 days. Early wild-type thrombus exposure inhibited profibrotic gene expression in CCR7(-/-) in ex vivo vein wall culture. Bone marrow chimera experiments further showed that circulating CCR7(+) leukocytes partially rescued midterm profibrotic changes in CCR7(-/-) mice. In human histological sections of chronic thrombosed femoral veins, CCR7(+) cells were present in the fibrotic areas.

CONCLUSIONS

Post-thrombotic vein wall remodeling is impaired in CCR7(-/-) mice, with a profibrotic phenotype, is dependent on the thrombotic mechanism, and is mediated by circulating CCR7(+) cells. Unlike other postinjury fibrotic responses, CCR7(+) signaling may be important for positive vein wall remodeling after VT.

Contribution of recurrent venous thrombosis and inherited thrombophilia to the pathogenesis of postthrombotic syndrome

Postthrombotic syndrome (PTS) is a common complication of deep vein thrombosis. This study aims to assess the role of recurrent venous thrombosis and inherited thrombophilia in the pathogenesis of PTS. A series of 206 patients diagnosed with lower extremity venous thrombosis were retrospectively reviewed. The PTS was observed in 30.58% of the patients. Recurrent venous thrombosis was identified in 3.4% of the patients without PTS and in 33.3% of patients with PTS (P < .001). Inherited thrombophilia alone or in association with recurrent venous thrombosis was more commonly detected when PTS was moderate to severe (P = .04 and <.001) or severe (P < .001). Recurrent venous thrombosis increases the incidence of PTS significantly. The severity of PTS raises when an underlying thrombophilia is present either alone or in association with recurrent venous thrombosis.

Magnetic resonance T1 relaxation time of venous thrombus is determined by iron processing and predicts susceptibility to lysis

BACKGROUND

The magnetic resonance longitudinal relaxation time (T1) changes with thrombus age in humans. In this study, we investigate the possible mechanisms that give rise to the T1 signal in venous thrombi and whether changes in T1 relaxation time are informative of the susceptibility to lysis.

METHODS AND RESULTS

Venous thrombosis was induced in the vena cava of BALB/C mice, and temporal changes in T1 relaxation time correlated with thrombus composition. The mean T1 relaxation time of thrombus was shortest at 7 days following thrombus induction and returned to that of blood as the thrombus resolved. T1 relaxation time was related to thrombus methemoglobin formation and further processing. Studies in inducible nitric oxide synthase (iNOS(-/-))-deficient mice revealed that inducible nitric oxide synthase mediates oxidation of erythrocyte lysis-derived iron to paramagnetic Fe3+, which causes thrombus T1 relaxation time shortening. Studies using chemokine receptor-2-deficient mice (Ccr2(-/-)) revealed that the return of the T1 signal to that of blood is regulated by removal of Fe3+ by macrophages that accumulate in the thrombus during its resolution. Quantification of T1 relaxation time was a good predictor of successful thrombolysis with a cutoff point of <747 ms having a sensitivity and specificity to predict successful lysis of 83% and 94%, respectively.

CONCLUSIONS

The source of the T1 signal in the thrombus results from the oxidation of iron (released from the lysis of trapped erythrocytes in the thrombus) to its paramagnetic Fe3+ form. Quantification of T1 relaxation time appears to be a good predictor of the success of thrombolysis.

Post-thrombotic syndrome: a clinical review

Up to half of patients with proximal deep vein thrombosis (DVT) will develop post-thrombotic syndrome (PTS) despite optimal anticoagulant therapy. PTS significantly impacts upon quality of life and has major health-economic implications. This narrative review describes the pathophysiology, risk factors, and diagnosis, prevention and treatment of PTS, to improve our understanding of the disease and guide treatment. Relevant articles were identified through systematic searches of the PubMed, EMBASE and Cochrane databases between 1966 and November 2011. Studies were included for detailed assessment if they met the following criteria: published in English, human study participants, study population aged > 18 years, and lower limb post-thrombotic syndrome. All non-systematic reviews and single patient case reports were excluded. Recurrent thrombosis, thrombus location and obesity are major risk factors, whereas the importance of gender and age remain uncertain. The diagnosis of PTS is based on clinical findings in patients with a known history of DVT. Several clinical scales have been described, with the Villalta Score gaining increasing popularity. Adequate anticoagulation and use of elastic compression stockings (ECS) following DVT can reduce the incidence of PTS. Catheter-directed thrombolysis and mechanical thrombectomy of acute DVT may preserve valvular function. Studies to date of these techniques are encouraging, and have reported improved hemodynamics and a reduced incidence of PTS. The management of established PTS is challenging. Compression therapy, aimed at reducing the underling venous hypertension, remains the mainstay of treatment. This is despite a paucity of high-quality evidence to support its use. Pharmacologic and surgical treatments have also been described, with a number of studies citing symptomatic improvement.

Hypoxia-inducible factor pathway and diseases of the vascular wall

BACKGROUND

Hypoxia may contribute to the pathogenesis of various diseases of the vascular wall. Hypoxia-inducible factors (HIFs) are nuclear transcriptional factors that regulate the transcription of genes that mediate cellular and tissue homeostatic responses to altered oxygenation. This article reviews the published literature on and discusses the role of the HIF pathway in diseases involving the vascular wall, including atherosclerosis, arterial aneurysms, pulmonary hypertension, vascular graft failure, chronic venous diseases, and vascular malformation.

METHODS

PubMed was searched with the terms "hypoxia-inducible factor" or "HIF" and "atherosclerosis," "carotid stenosis," "aneurysm," "pulmonary artery hypertension," "varicose veins," "venous thrombosis," "graft thrombosis," and "vascular malformation."

RESULTS

In atherosclerotic plaque, HIF-1α was localized in macrophages and smooth muscle cells bordering the necrotic core. Increased HIF-1α may contribute to atherosclerosis through alteration of smooth muscle cell proliferation and migration, angiogenesis, and lipid metabolism. The expression of HIF-1α is significantly elevated in aortic aneurysms compared with nonaneurysmal arteries. In pulmonary hypertension, HIF-1α contributes to the increase of intracellular K(+) and Ca(2+) leading to vasoconstriction of pulmonary smooth muscle cells. Alteration of the HIF pathway may contribute to vascular graft failure through the formation of intimal hyperplasia. In chronic venous disease, HIF pathway dysregulation contributes to formation of varicose veins and venous thromboembolism. However, whether the activation of the HIF pathway is protective or destructive to the venous wall is unclear. Increased activation of the HIF pathway causes aberrant expression of angiogenic factors contributing to the formation and maintenance of vascular malformations.

CONCLUSIONS

Pathologic vascular wall remodelling of many common diseases of the blood vessels has been found to be associated with altered activity of the HIF pathway. Therefore, understanding the role of the HIF pathway in diseases of the vascular wall is important to identify novel therapeutic strategies in the management of these pathologies.

The role of urokinase plasminogen activator and plasmin activator inhibitor-1 on vein wall remodeling in experimental deep vein thrombosis

OBJECTIVE

Deep vein thrombosis (DVT) resolution instigates an inflammatory response, resulting in vessel wall damage and scarring. Urokinase-plasminogen activator (uPA) and its inhibitor, plasminogen activator inhibitor-1 (PAI-1), are integral components of the fibrinolytic system, essential for venous thrombosis (VT) resolution. This study determined the vein wall response when exposed to increased and decreased plasmin activity.

METHODS

A mouse inferior vena cava (IVC) ligation model in uPA -/- or PAI-1 -/- and their genetic wild types (B6/SvEv and C57/BL6, respectively) was used to create stasis thrombi, with tissue harvest at either 8 or 21 days. Tissue analysis included gene expression of vascular smooth muscle cells (alpha smooth muscle actin [αSMA], SM22) and endothelial marker (CD31), by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, matrix metalloproteinase (MMP)-2 and -9 activity by zymography, and vein wall collagen by picro-Sirius red histologic analysis. A P < .05 was considered significant.

RESULTS

Thrombi were significantly larger in both 8-day and 21-day uPA -/- as compared with wild type (WT) and were significantly smaller in both 8-day and 21-day PAI-1 -/- as compared with WT. Correspondingly, 8-day plasmin levels were reduced in half in uPA -/- and increased three-fold in PAI-1 -/- when compared with respective WT thrombi (P < .05; n = 5-6). The endothelial marker CD31 was elevated two-fold in PAI-1 -/- mice at 8 days, but reduced 2.5-fold at 21 days in uPA -/- as compared with WT (P = .02; n = 5-6), suggesting less endothelial preservation. Vein wall vascular smooth muscle cell (VSMC) gene expression showed that 8-day and 21-day PAI-1 -/- mice had 2.3- and 3.8-fold more SM22 and 1.8- and 2.3-fold more αSMA expression than respective WT (P < .05; n = 5-7), as well as 1.8-fold increased αSMA (+) cells (P ≤ .05; n = 3-5). No significant difference in MMP-2 or -9 activity was found in the PAI-1 -/- mice compared with WT, while 5.4-fold more MMP-9 was present in 21-day WT than 21-day uPA -/- (P = .03; n = 5). Lastly, collagen was ∼two-fold greater at 8 days in PAI-1 -/- IVC as compared with WT (P = .03; n = 6) with no differences observed in uPA -/- mice.

CONCLUSIONS

In stasis DVT, plasmin activity is critical for thrombus resolution. Divergent vein wall responses occur with gain or loss of plasmin activity, and despite smaller VT, greater vein wall fibrosis was associated with lack of PAI-1.

Rationale and Indications for Aggressive Early Thrombus Removal

Randomized clinical trials have defined anticoagulation with unfractionated or low-molecular-weight heparin followed by warfarin as a standard therapy for acute deep venous thrombosis (DVT). Such treatment is highly effective in preventing recurrent venous thromboembolism with a low risk of bleeding, but provides imperfect protection against development of the post-thrombotic syndrome. Several strategies of early thrombus removal, including surgical venous thrombectomy, catheter-directed thrombolysis and pharmacomechanical thrombectomy have been developed with the goal of reducing the incidence of the post-thrombotic syndrome by restoring venous patency and preserving valvular function. Although clinical judgement and a consideration of the individual patient's medical condition and values are required, early thrombus removal strategies should be considered in selected patients with phlegmasia cerulea dolens and those with a first episode of acute iliofemoral thrombosis of less than 14 days duration.

Incidence and Risk Factors of the Post-thrombotic Syndrome

Annually 1–2 in every 1000 adults will develop a deep venous thrombosis of the lower extremity. A third to half of these patients will develop the post-thrombotic syndrome (PTS). However, predicting which patients will develop the PTS remains elusive. Ipsilateral thrombosis recurrence seems to be the most important risk factor. Moreover, residual venous occlusion and valvular reflux seem to predict PTS incidence to some degree. Laboratory parameters, including D-dimers and inflammatory markers, have shown promise in predicting development of the PTS in patients and are currently under investigation. Creating a model based on all combined risk factors and patient characteristics might aid in risk stratification in individual patients.

Evaluating the Role of Compression Stockings in Preventing Post thrombotic Syndrome: A Review of the Literature

Background. Postthrombotic syndrome (PTS) is a burdensome and costly complication of deep vein thrombosis (DVT). Up to 50% of patients with DVT will develop the disease within two years following the diagnosis of acute DVT. Various risk factors for developing PTS have been identified and different modalities have been used to prevent its development. Compression stockings have been studied for the prevention of PTS in patients diagnosed with proximal DVT. Methods. MEDLINE and EMBASE databases were searched to identify relevant original articles. Results. Several trials including two metaanalyses have examined the role of compression stockings for the prevention of PTS. Although most trials showed significant reduction in the development of PTS with the use of compression stockings, limitations in study design prevent the generalizability of the data. Two studies supported an individualized tailored duration especially in patients at low risk for developing the syndrome. A randomized double-blind placebo-controlled trial involving 800 patients is currently ongoing and may confirm the results of older studies. Conclusions. Clinical trials support the use of compression stockings in patients diagnosed with proximal DVT for the prevention of PTS.

Pathophysiology of Post-Thrombotic Syndrome: The Effect of Recurrent Venous Thrombosis and Inherited Thrombophilia

Post-thrombotic syndrome is an important chronic complication of deep vein thrombosis. This syndrome can be debilitating to patients and has a major economic impact on health care services. The pathophysiology of post-thrombotic syndrome is currently incompletely understood. Because therapeutic options for post-thrombotic syndrome are extremely limited and results are often disappointing, recognizing of the pathophysiology and risk factors of this syndrome is essential to prevent the disabling consequences of this disease. The present paper focuses on risk determinants of post-thrombotic syndrome after deep vein thrombosis. The contribution of recurrent venous thrombosis and inherited thrombophilia to the pathogenesis of this syndrome is reviewed and discussed in details.

Percutaneous options for acute deep vein thrombosis

Anticoagulant therapy is associated with poor late limb outcomes in many patients with deep vein thrombosis (DVT). Because systemic thrombolysis and surgical thrombectomy have inherent limitations, image-guided percutaneous thrombus removal is currently favored. Pharmacologic thrombolysis is effective in removing thrombus, but long-term benefit has not been conclusively demonstrated and major bleeding rates appear to be higher than those observed with anticoagulation alone. Percutaneous mechanical thrombectomy is limited as a stand-alone DVT treatment method by inability to clear large thrombosed veins completely and by pulmonary embolism. Pharmacomechanical thrombolysis represents the most promising currently available method to treat DVT. Randomized trials with long-term follow-up are needed to determine the appropriate indications for these procedures. In the meantime, a highly individualized approach to selection of patients is recommended, taking into account the chronicity and anatomic extent of DVT, the presence of circulatory compromise, the patient's bleeding risk profile, life expectancy, and anticipated activity level.

Lower extremity venous anatomy

The lower extremity venous system includes the superficial, deep, and perforating veins. The antegrade flow of blood within these veins is ensured by a system of muscular venous pumps and bicuspid valves. Dysfunction of the system may result from degeneration of the vein wall, post-thrombotic valvular damage, chronic venous obstruction, or dysfunction of the muscular pumps. Although chronic venous disease often receives less attention than arterial disease, it includes an array of manifestations resulting from a complex interaction of anatomy and hemodynamic failure. A thorough understanding of the highly variable venous anatomy is essential to understanding the underlying pathophysiology as well as in directing treatment.

Upregulation of hypoxia-inducible factor 1 alpha in local vein wall is associated with enhanced venous thrombus resolution

Introduction

Venous thrombus resolution may be regulated by an angiogenic process that involves the surrounding vein wall. The aims of this study were to determine whether: (i) thrombosis stimulates activation of the angiogenic transcription factor, hypoxia-inducible factor (HIF) 1α, and downstream expression of growth factors in vein wall; and (ii) upregulation of HIF1α in vein wall leads to increased growth factor expression and enhanced thrombus resolution.

Materials and methods

HIF1α, vascular endothelial growth factor (VEGF), and placental growth factor (PLGF) were quantified in mouse inferior vena cava (IVC) at days 1, 3, 7, and 14 after thrombus formation (n = 10-13 per group). An additional group of thrombosed mice were treated with the prolyl-hydroxylase domain (PHD) inhibitor, L-mimosine (L-mim) or vehicle control. HIF1α, VEGF, and PLGF in IVC were measured at days 1 and 7; and vein recanalisation and thrombus resolution were measured at days 7 and 10 (n = 6-7 per group).

Results

HIF1α was expressed in thrombosed IVC and its levels remained relatively constant throughout natural resolution. The levels of VEGF in thrombosed IVC were elevated at days 1 (P < 0.0001) and 3 (P < 0.05); and PLGF at days 1 (P < 0.0001), 3 (P < 0.0001), and 7 (P < 0.0001). Treatment with L-mim led to: increased HIF1α (P < 0.05), VEGF (P < 0.005), and PLGF (P < 0.001) levels in the IVC; decreased thrombus size (P < 0.01); and increased vein recanalisation (P < 0.001).

Conclusions

HIF1α levels in vein wall are not affected by thrombosis and it appears that the angiogenic drive in the vein surrounding resolving thrombus is regulated independently of HIF1α. Stimulating HIF1α levels in the vein wall leads to an increased angiogenic drive and promotes vein recanalisation and thrombus resolution.

Leukocytes and the natural history of deep vein thrombosis: current concepts and future directions

Observational studies have shown that inflammatory cells accumulate within the thrombus and surrounding vein wall during the natural history of venous thrombosis. More recent studies have begun to unravel the mechanisms that regulate this interaction and have confirmed that thrombosis and inflammation are intimately linked. This review outlines our current knowledge of the complex relationship between inflammatory cell activity and venous thrombosis and highlights new areas of research in this field. A better understanding of this relationship could lead to the development of novel therapeutic targets that inhibit thrombus formation or promote its resolution.

Vein wall remodeling after deep vein thrombosis: differential effects of low molecular weight heparin and doxycycline

BACKGROUND

Venous thrombus resolution sets up an early intense inflammatory reaction, from which vein wall damage results. Tissue response to injury includes matrix metalloproteinase (MMP) activation and extracellular matrix protein turnover. This study sought to determine the effect of exogenous MMP inhibition and its potential attenuation of early vein wall injury.

METHODS

Rats received treatment beginning 24 hr after a stasis venous thrombosis by near occlusive ligation and until harvest at day 7. Three groups were evaluated: (1) vehicle saline controls (NaCl), (2) low molecular weight heparin (LMWH; Lovenox, 3 mg/kg daily SQ), and (3) doxycycline (DOXY, 30 mg/kg daily PO). Thrombus size (mg/mm), levels of tumor necrosis factor alpha (TNF alpha) and D-dimer by colorimetric assay, and monocytes counts by immunohistochemistry were assessed. Vein wall assessment included stiffness by tensiometry, interleukin 1beta (IL-1 beta protein levels by enzyme-linked immunosorbent assay, MMP2 and -9 by zymography, and histological analysis of intimal thickness (IT). Comparisons were by t-test to control. p < 0.05 was considered significant.

RESULTS

Thrombus sizes were similar at days 2 and 7 for all three groups, while thrombus TNFalpha was increased in 2-day LMWH- and DOXY-treated groups (NaCl = 1.0 +/- 0.8, LWMH = 9 +/- 3, DOXY = 27 +/- 5 pg/mg protein, n = 6-8, p < 0.05) and at 7 days in the DOXY group (NaCl = 3.0 +/- 2.5, DOXY = 23 +/- 4.2 pg/mg protein, n = 5, p < 0.05). Vein wall stiffness at 7 days was less with LMWH treatment, but not with DOXY, compared to controls (NaCl = 0.33 +/- 0.05, LMWH = 0.17 +/- 0.03, DOXY = 0.43 +/- 0.09 N/mm, n = 5-7, p < 0.05). Vessel-wall IL-1 beta was reduced only in the DOXY group at 7 days (NaCl = 26 +/- 3, LMWH = 38 +/- 17, DOXY = 6 +/- 3 pg/mg protein, n = 4-6, p < 0.05), as was the IT score versus controls (NaCl = 2.2 +/- 0.6, LMWH =1.7 +/- 0.3, DOXY = 0.8 +/- 0.20, n = 4-6, p < 0.05). Zymographic MMP9 activity was significantly reduced at 2 days in the LMWH and DOXY groups (NaCl = 85 +/- 24, LMWH = 23 +/- 7( *), DOXY = 13 +/- 5 U/mg protein, n = 6-8, p < 0.05). MMP2 zymographic activity, thrombus monocyte cell counts, and D-dimer activity were not significantly different across groups.

CONCLUSION

Treatment with LMWH or DOXY did not alter the size of deep vein thrombosis, mildly altered thrombus composition, and differentially affected vein wall injury, despite similar reductions in early MMP9 activity. Whether exogenous MMP inhibition affects long-term vein wall fibrosis will require further study.

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.