Vein wall remodeling in patients with acute deep vein thrombosis and chronic postthrombotic changes

Luminal Changes in Patients with Inferior Vena Cava Filters and Development of Chronic Venous Disease

BACKGROUND

This study aimed to analyze the luminal changes in the iliocaval veins and their effects on the development of signs and symptoms of chronic venous disease manifesting from inferior vena cava (IVC) filter placement.

METHODS

This was a retrospective observations study; deidentified patients with an IVC filter placed with subsequent luminal changes were included. All patients had a computerized tomography (CT) scan with or without ultrasound and those who underwent an intervention for the obstruction had also venography and intravascular ultrasound (IVUS). The diameter of IVC and iliac veins was measured from the near wall to the far wall. IVC diameters measured less than 12 mm were considered to be retractions. Signs and symptoms of chronic venous disease were obtained from patient charts and were reported according to the highest CEAP class. The data were analyzed using descriptive statistics, presenting diameter changes as a mean with standard deviation and a range of diameters included.

RESULTS

Overall, 76 patients were included in this study, of whom 66 had occlusion of the IVC or the Iliac veins. Luminal changes of the IVC were observed in all patients. A total of 58 patients presented with chronic post-thrombotic changes in both the IVC and iliac veins. There were 4 patients that had a luminal reduction with no filling defects or post-thrombotic changes. Average IVC diameter and iliac vein diameter was measured to be 8.3 ± 1.4 mm and 4.6 ± 1.4 mm, respectively. Patients most frequently presented with extremity swelling, but other signs such as venous ulceration or skin damage were observed.

CONCLUSIONS

Permanent luminal changes of the IVC and iliac veins were observed as a result of IVC filter placement and such patients commonly present with signs and symptoms of chronic venous disease. Together, with other known filter complications, these observations add more reasons for a timely retrieval. When such changes occur, patients' appropriate symptoms can be successfully treated. The permanent changes made by filter placement in the IVC and iliac veins further support filter retrieval in a timely fashion. The luminal changes induced by filter placement should be recognized early, particularly in symptomatic patients who can be safely treated with endovenous procedures.

Overall haemostatic potential assay for prediction of outcomes in venous and arterial thrombosis and thrombo-inflammatory diseases

Thromboembolic diseases including arterial and venous thrombosis are common causes of morbidity and mortality globally. Thrombosis frequently recurs and can also complicate many inflammatory conditions through the process of 'thrombo-inflammation,' as evidenced during the COVID-19 pandemic. Current candidate biomarkers for thrombosis prediction, such as D-dimer, have poor predictive efficacy. This limits our capacity to tailor anticoagulation duration individually and may expose lower risk individuals to undue bleeding risk. Global coagulation assays, such as the Overall Haemostatic Potential (OHP) assay, that investigate fibrin generation and fibrinolysis, may provide a more accurate and functional assessment of hypercoagulability. We present a review of fibrin's critical role as a central modulator of thrombotic risk. The results of our studies demonstrating the OHP assay as a predictive biomarker in venous thromboembolism, chronic renal disease, diabetes mellitus, post-thrombotic syndrome, and COVID-19 are discussed. As a comprehensive and global measurement of fibrin generation and fibrinolytic capacity, the OHP assay may be a valuable addition to future multi-modal predictive tools in thrombosis.

Current challenges in the prevention and management of post-thrombotic syndrome-towards improved prevention

Post-thrombotic syndrome (PTS) is a common and potentially debilitating complication of deep vein thrombosis (DVT), affecting up to 50% of DVT patients. The consequence of this chronic condition includes reduced quality of life, increased use of the healthcare system and decreased productivity. The societal impact of this condition is projected to increase, given our ageing population and increased burden of thrombotic diseases. Despite significant recent advances in our understanding of PTS, many unanswered questions remain. Currently, there are few effective and proven options for established PTS; hence, the emphasis should be on instituting effective prevention to reduce the progression to PTS. Effective anticoagulation lowers the risk of PTS, with direct oral anticoagulants appearing to outperform vitamin-K antagonists. However, the evidence for elastic compression stockings and endovascular thrombolysis or thrombectomy techniques remains unclear. Accurate identification of individuals at high risk of developing PTS may also improve the targeting of preventative interventions. This review will examine the current body of evidence regarding PTS, with a focus on preventative strategies as well as novel biomarkers.

Immune cell-mediated venous thrombus resolution

Herein, we review the current processes that govern experimental deep vein thrombus (DVT) resolution. How the human DVT resolves at the molecular and cellular level is not well known due to limited specimen availability. Experimentally, the thrombus resolution resembles wound healing, with early neutrophil-mediated actions followed by monocyte/macrophage-mediated events, including neovascularization, fibrinolysis, and eventually collagen replacement. Potential therapeutic targets are described, and coupling with site-directed approaches to mitigate off-target effects is the long-term goal. Similarly, timing of adjunctive agents to accelerate DVT resolution is an area that is only starting to be considered. There is much critical research that is needed in this area.

The clinical application of venous ultrasound in diagnosis and follow-up of lower extremity deep vein thrombosis (DVT): a case-based discussion

Current clinical practice guidelines lack explicit guidance on the indications and appropriate timing of venous ultrasound (US) in lower extremity deep vein thrombosis (DVT) follow-up. Moreover, abnormal findings reported on venous US in DVT follow-up or suspected recurrent DVT may be difficult for clinicians to interpret, which carries risk of harm from inappropriate use of anti- coagulation and increased healthcare resource utilization. Due to the above factors, over-use of ultrasound in diagnosis and follow-up of lower extremity DVT has been reported in western health systems. We have undertaken a case-based discussion and a scoping review of existing guidelines on the use of venousUS following prior diagnosis of DVT, to guide appropriate interpretation of commonly reported US abnormalities and provide our suggestions in the light of best available evidence on appropriate timing to perform follow-up US in management of lower extremity DVT.

Diffuse generalized venulitis as the primary pathology of Behçet's disease: A comprehensive magnetic resonance venography study

OBJECTIVE

Behçet's Disease (BD) is a chronic multisystem vasculitis that manifests with destructive inflammation affecting the eyes, central nervous system, and blood vessels. The pathology of vein involvement in BD is poorly characterized. Magnetic resonance (MR) venography gives more comprehensive information about deep veins and adjacent tissues. In this study, we aimed to characterize vein involvement and evaluate the diagnostic utility of MR venography in BD.

METHODS

Sixty-five BD patients who fulfilled the International Study Group (ISG) criteria and 20 healthy control subjects were enrolled. Inferior vena cava (IVC), common iliac veins (CIV), external (EIV) and internal iliac veins (IVV), common femoral veins (CFV), femoral veins (FV), and greater saphenous veins (GSV) of BD patients and healthy controls were evaluated with MR venography and ultrasonography for the presence pathologic features, luminal thrombi, vessel wall changes, and perivascular abnormalities.

RESULTS

33 vascular and 32 non-vascular BD patients (mean age 39.3 ± 11.3 years and 48 [73.8%] male) were enrolled. MR venography revealed diffuse concentric thickening of the walls of IVC, CIV, EIV, IIV, CFV, FV, and GSV in BD (healthy controls vs. BD p<0.05 for all vein segments). MR venography provided additional information about veins and perivascular tissues like contrast enhancement, enlarged lymph nodes, and seminal vesicle vascularization, which were remarkably more frequent in vascular BD than non-vascular BD and healthy controls.

CONCLUSION

The results of our study suggest that the involvement of the venous system is diffuse and generalized in BD, and demonstration of venulitis might help diagnose the disease.

Nonmalignant portal vein thrombi in patients with cirrhosis consist of intimal fibrosis with or without a fibrin-rich thrombus

BACKGROUND AND AIM

Portal vein thrombosis (PVT) is a common complication of cirrhosis. The exact pathophysiology remains largely unknown, and treatment with anticoagulants does not lead to recanalization of the portal vein in all patients. A better insight into the structure and composition of portal vein thrombi may assist in developing strategies for the prevention and treatment of PVT.

APPROACH AND RESULTS

Sixteen prospectively and 63 retrospectively collected nonmalignant portal vein thrombi from patients with cirrhosis who underwent liver transplantation were included. Histology, immunohistochemistry, and scanning electron microscopy were used to assess structure and composition of the thrombi. Most recent CT scans were reanalyzed for thrombus characteristics. Clinical characteristics were related to histological and radiological findings. All samples showed a thickened, fibrotic tunica intima. Fibrin-rich thrombi were present on top of the fibrotic intima in 9/16 prospective cases and in 21/63 retrospective cases. A minority of the fibrotic areas stained focally positive for fibrin/fibrinogen (16% of cases), von Willebrand factor (VWF; 10%), and CD61 (platelets, 21%), while most of the fibrin-rich areas stained positive for those markers (fibrin/fibrinogen, 100%; VWF, 77%; CD61, 100%). No associations were found between clinical characteristics including estimated thrombus age and use of anticoagulants and presence of fibrin-rich thrombi.

CONCLUSION

We demonstrate that PVT in patients with cirrhosis consists of intimal fibrosis with an additional fibrin-rich thrombus in only one-third of cases. We hypothesize that our observations may explain why not all portal vein thrombi in patients with cirrhosis recanalize by anticoagulant therapy.

[Risk of post-thrombotic syndrome following direct oral anticoagulant intake: a systematic review and meta-analysis]

OBJECTIVE

To perform a systematic review and meta-analysis of data devoted to the risk of post-thrombotic syndrome (PTS) following direct oral anticoagulant (DOAC) intake.

MATERIAL AND METHODS

A systematic review and meta-analysis of trials available in the PubMed database were performed in March 2021. Analysis included the reports with known Villalta score for PTS in patients receiving DOACs or alternative anticoagulation. We analyzed the incidence and risk of any form of PTS.

RESULTS

We found 10 comparative studies comprising 3161 patients. Incidence of PTS under DOAC therapy was 30.8% (95% confidence interval (CI) 22.2-39.3%), severe PTS - 2.2% (95% CI 1.0-3.4%). DOACs were associated with significantly less risk of any form of PTS (odds ratio (OR) 0.57; 95% CI 0.48-0.68; p<0.001) and severe PTS (OR 0.56; 95% CI 0.36-0.87; p=0.010) compared to vitamin K antagonists. Among various DOACs, specified data were available only for rivaroxaban (OR 0.54, 95% CI 0.42-0.71, p<0.001 for any PTS; OR 0.49, 95% CI 0.27-0.89, p=0.019 for severe PTS). The use of flavonoids in adjunction to rivaroxaban was associated with additional risk reduction for PTS (OR 0.14; 95% CI 0.06-0.31; p<0.001).

CONCLUSION

Moderate quality evidence suggests that DOACs are associated with significant less risk of any PTS and severe PTS compared to VKA in patients with deep vein thrombosis. Among all DOACs, only rivaroxaban has clear data confirming PTS risk reduction. The use of flavonoids in adjunction to rivaroxaban can further improve treatment outcomes.

Impact of statin treatment on patients diagnosed with chronic venous disease. Morphological analysis of the venous wall and clinical implications

OBJECTIVES

The study evaluates the potential morphological changes that may occur in the venous wall in the case of the patients with chronic venous disease which associates treatment with statins for at least 2 years.

METHODS

Operated patients with chronic venous disease in the CEAP C2-C3 stage were included in the study. 215 venous fragments, collected from 50 patients within the study group and 179 venous fragments collected from 52 patients within the control group were microscopically analysed, evaluating a series of morpho-anatomical parameters.

RESULTS

In the study group, it was found that, venous reflux predominantly affects small veins, and also, a significant increase in collagen deposits in the adventitia and media tunics, proportional to the thickening of the venous wall.

CONCLUSION

Our results indicate possible effects of statins upon the venous morphology. Further studies are needed to determine the impact of these results on daily practice.

The aging venous system: from varicosities to vascular cognitive impairment

Aging-induced pathological alterations of the circulatory system play a critical role in morbidity and mortality of older adults. While the importance of cellular and molecular mechanisms of arterial aging for increased cardiovascular risk in older adults is increasingly appreciated, aging processes of veins are much less studied and understood than those of arteries. In this review, age-related cellular and morphological alterations in the venous system are presented. Similarities and dissimilarities between arterial and venous aging are highlighted, and shared molecular mechanisms of arterial and venous aging are considered. The pathogenesis of venous diseases affecting older adults, including varicose veins, chronic venous insufficiency, and deep vein thrombosis, is discussed, and the potential contribution of venous pathologies to the onset of vascular cognitive impairment and neurodegenerative diseases is emphasized. It is our hope that a greater appreciation of the cellular and molecular processes of vascular aging will stimulate further investigation into strategies aimed at preventing or retarding age-related venous pathologies.

Ultrasonographic measurement of the vascular wall thickness and intima-media thickness in patients with Behçet's disease with symptoms or signs of vascular involvement: A cross-sectional study

Objectives

This study aims to measure and compare bilateral carotid intima-media thickness (CIMT), bilateral jugular, common femoral, and main portal vein wall thicknesses (VWTs) in Behçet’s disease (BD) patients with and without vascular involvement to obtain a cut-off value for vascular complications and determine their relationship with disease activity.

Patients and methods

Sixty-three BD patients (41 males, 22 females; median age: 38.0 years; min 20 - max 71 years) and 30 healthy control subjects (14 males, 16 females; median age: 40.3 years; min 21 - max 60 years) were included in this cross-sectional study between February and March 2020. According to imaging findings, BD patients were divided into two groups as those with and without vascular complications. Disease duration, medical treatment and BD manifestations of patients were questioned. Disease activity was evaluated using the Behçet's Disease Current Activity Form (BDCAF) and the Behçet's Syndrome Activity Scale (BSAS). Two radiologists blinded to the diagnosis of BD used ultrasound to measure VWT and CIMT. Receiver operating characteristics were assessed to obtain sensitivity and specificity values for each VWT and CIMT.

Results

The groups were similar in terms of age, sex, and body mass index (p>0.05). There was a significant difference between the BD groups when the BDCAF and BSAS scores were compared, while there was no difference between them in terms of disease duration and medical treatment (p>0.05). All VWTs and CIMTs were significantly higher in patients with BD compared to healthy controls (p<0.05). There was no significant difference between the BD groups in terms of CIMT, jugular and common femoral VWTs (p>0.05). But portal VWT was significantly higher in patients with vascular involvement (p<0.05). A cut-off value of ≥1.35 mm yielded a sensitivity of 79.2% and a specificity of 82.4% for the diagnosis of vascular involvement with the highest Youden's index (area under the curve, 0.869; 95% confidence interval, 0.783 to 0.956).

Conclusion

Portal VWT has high sensitivity and specificity for the screening of vascular involvement in patients with BD.

Femoral vein wall thickness measurement: A new diagnostic tool for Behçet's disease

OBJECTIVES

Diagnosing Behçet's disease (BD) is a challenge, especially in countries with a low prevalence. Recently, venous wall thickness (VWT) in lower extremities has been shown to be increased in BD patients. In this study, we aimed to investigate the diagnostic performance of common femoral vein (CFV) thickness measurement in BD and whether it can be used as a diagnostic tool.

METHODS

. Patients with BD (n = 152), ankylosing spondylitis (n = 27), systemic vasculitides (n = 23), venous insufficiency (n = 29), antiphospholipid syndrome (APS; n = 43), deep vein thrombosis due to non-inflammatory causes (n = 25) and healthy controls (n = 51) were included in the study. Bilateral CFV thickness was measured with ultrasonography by a radiologist blinded to cases.

RESULTS

Bilateral CFV thickness was significantly increased in BD compared with all control groups (P < 0.001 for all). The area under the receiver operating characteristic curve for bilateral CFV thicknesses in all comparator groups was >0.95 for the cut-off value (0.5 mm). This cut-off value also performed well against all control groups with sensitivity rates >90%. The specificity rate was also >80% in all comparator groups except APS (positive predictive value: 79.2-76.5%, negative predictive value: 92-91.8% for right and left CFV, respectively).

CONCLUSION

Increased CFV thickness is a distinctive feature of BD and is rarely present in healthy and diseased controls, except APS. Our results suggest that CFV thickness measurement with ultrasonography, a non-invasive radiological modality, can be a diagnostic tool for BD with sensitivity and the specificity rates higher than 80% for the cut-off value ≥0.5 mm.

Time-Restricted Salutary Effects of Blood Flow Restoration on Venous Thrombosis and Vein Wall Injury in Mouse and Human Subjects

BACKGROUND

Up to 50% of patients with proximal deep vein thrombosis (DVT) will develop the postthrombotic syndrome characterized by limb swelling and discomfort, hyperpigmentation, skin ulcers, and impaired quality of life. Although catheter-based interventions enabling the restoration of blood flow (RBF) have demonstrated little benefit on postthrombotic syndrome, the impact on the acuity of the thrombus and mechanisms underlying this finding remain obscure. In experimental and clinical studies, we examined whether RBF has a restricted time window for improving DVT resolution.

METHODS

First, experimental stasis DVT was generated in C57/BL6 mice (n=291) by inferior vena cava ligation. To promote RBF, mice underwent mechanical deligation with or without intravenous recombinant tissue plasminogen activator administered 2 days after deligation. RBF was assessed over time by ultrasonography and intravital microscopy. Resected thrombosed inferior vena cava specimens underwent thrombus and vein wall histological and gene expression assays. Next, in a clinical study, we conducted a post hoc analysis of the ATTRACT (Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis) pharmacomechanical catheter-directed thrombolysis (PCDT) trial (NCT00790335) to assess the effects of PCDT on Venous Insufficiency Epidemiological and Economic Study quality-of-life and Villalta scores for specific symptom-onset-to-randomization timeframes.

RESULTS

Mice that developed RBF by day 4, but not later, exhibited reduced day 8 thrombus burden parameters and reduced day 8 vein wall fibrosis and inflammation, compared with controls. In mice without RBF, recombinant tissue plasminogen activator administered at day 4, but not later, reduced day 8 thrombus burden and vein wall fibrosis. It is notable that, in mice already exhibiting RBF by day 4, recombinant tissue plasminogen activator administration did not further reduce thrombus burden or vein wall fibrosis. In the ATTRACT trial, patients receiving PCDT in an intermediate symptom-onset-to-randomization timeframe of 4 to 8 days demonstrated maximal benefits in Venous Insufficiency Epidemiological and Economic Study quality-of-life and Villalta scores (between-group difference=8.41 and 1.68, respectively, P<0.001 versus patients not receiving PCDT). PCDT did not improve postthrombotic syndrome scores for patients having a symptom-onset-to-randomization time of <4 days or >8 days.

CONCLUSIONS

Taken together, these data illustrate that, within a restricted therapeutic window, RBF improves DVT resolution, and PCDT may improve clinical outcomes. Further studies are warranted to examine the value of time-restricted RBF strategies to reduce postthrombotic syndrome in patients with DVT.

Predictors for the risk and severity of post-thrombotic syndrome in vascular Behçet's disease

OBJECTIVE

Deep vein thrombosis (DVT) of the lower extremities is the most common form of vascular involvement in Behçet disease (BD), frequently leading to post-thrombotic syndrome (PTS) as a disabling complication. We have described the clinical characteristics and predictors of PTS presence among patients with BD and lower extremity DVT. We also used venous Doppler ultrasound (US) examinations in our assessment.

METHODS

Patients with BD (n = 205; 166 men, 39 women; age 39 ± 9.5 years) and a history of DVT were investigated. The Villalta scale was used to assess the presence and severity of PTS. Doppler US examinations were performed within 1 week of the clinical evaluation. The total number of vessels with reflux, thrombi, recanalization, and collateral vessels were calculated.

RESULTS

Of the 205 patients with BD, 62% had had PTS and 18% had had severe PTS. Patients with PTS had had greater reflux (P = .054) and thrombosis (P = .02) scores compared with patients without PTS. Treatment with anticoagulation (AC), immunosuppressive (IS) therapy, or AC combined with IS drugs did not affect the occurrence of PTS. However, patients treated with IS therapy, with or without AC drugs, had a decreased incidence of severe PTS compared with the AC-only group (P = .017). Patients treated with AC plus IS agents also had increased collateral scores compared with patients treated with only IS drugs. Interferon-α use seemed to provide better recanalization scores compared with azathioprine only (1.0 [range, 0-14] vs 2.5 [range, 0-10]; P = .010).

CONCLUSION

Patients with BD and DVT have a high risk of developing severe PTS. IS treatment decreases the development of severe PTS. AC therapy might influence the course of PTS by increasing the collateral scores, and the use of interferon-α also increased recanalization scores. Routine assessment with Doppler US examinations could be helpful in the prediction of severe PTS.

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.

Venous Biomechanics of Angioplasty and Stent Placement: Implications of the Poisson Effect

PURPOSE

To characterize the Poisson effect in response to angioplasty and stent placement in veins and identify potential implications for guiding future venous-specific device design.

MATERIALS AND METHODS

In vivo angioplasty and stent placement were performed in 3 adult swine by using an established venous stenosis model. Iron particle endothelium labeling was performed for real-time fluoroscopic tracking of the vessel wall during intervention. A finite-element computational model of a vessel was created with ADINA software (version 9.5) with arterial and venous biomechanical properties obtained from the literature to compare the response to radial expansion.

RESULTS

In vivo angioplasty and stent placement in a venous stenosis animal model with iron particle endothelium labeling demonstrated longitudinal foreshortening that correlated with distance from the center of the balloon (R² = 0.87) as well as adjacent segment narrowing that correlated with the increase in diameter of the treated stenotic segment (R² = 0.89). Finite-element computational analysis demonstrated increased Poisson effect in veins relative to arteries (linear regression coefficient slope comparison, arterial slope 0.033, R² = 0.9789; venous slope 0.204, R² = 0.9975; P < .0001) as a result of greater longitudinal Young modulus in veins compared with arteries.

CONCLUSIONS

Clinically observed adjacent segment narrowing during venous angioplasty and stent placement is a result of the Poisson effect, with redistribution of radially applied force to the longitudinal direction. The Poisson effect is increased in veins relative to arteries as a result of unique venous biomechanical properties, which may be relevant to consider in the design of future venous interventional devices.

Phlebosclerosis in lower extremities veins - a systematic review

Phlebosclerosis is a venous wall degenerative disease which has gained little popularity in the literature due to its uncertain clinical significance. The objective of this review is to evaluate the epidemiology, etiology and clinical significance of phlebosclerosis in lower extremities veins, particularly the effect of preexisting phlebosclerosis of the great saphenous vein on vein graft patency. Medline was searched from inception until November 1, 2019. Reference lists of included studies were scanned. Only articles published after 1949 were included. Two reviewers independently screened titles/abstracts and full-text papers for any study design in relation to phlebosclerosis in lower extremities veins and abstracted data. A total of 16 Cohort studies and one case-control study (3708 participants, mean age 61.8 years, 59.3 % men, and 40.7 % women) were included after screening 317 titles and abstracts, and 80 full-text articles. The incidence of phlebosclerosis ranged from 1.5-9.7 % depending on the radiological features. On the contrary, the incidence of the phlebosclerotic great saphenous vein prior to its use as a vein graft was 26.9-91 % on histological examination. The small saphenous vein was the most common location of phlebosclerosis followed by the great saphenous vein. There is a link between phlebosclerosis and age, venous insufficiency and haemodialysis. As for the vein graft patency seven studies demonstrated a correlation between preexisting phlebosclerosis and vein graft stenosis, whereas three studies failed to prove any association. In conclusion, the radiological incidence of phlebosclerosis depended on the ultrasound findings. Its presence in the great saphenous vein prior to its use as a vein graft is established on histological examination. The small saphenous vein is mainly affected. Risk factors included age, haemodialysis, and venous insufficiency. Preexisting wall thickness of the great saphenous vein graft seemed to affect negatively its patency in bypass surgery.

Resolution of Deep Venous Thrombosis: Proposed Immune Paradigms

Venous thromboembolism (VTE) is a pathology encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE) associated with high morbidity and mortality. Because patients often present after a thrombus has already formed, the mechanisms that drive DVT resolution are being investigated in search of treatment. Herein, we review the current literature, including the molecular mechanisms of fibrinolysis and collagenolysis, as well as the critical cellular roles of macrophages, neutrophils, and endothelial cells. We propose two general models for the operation of the immune system in the context of venous thrombosis. In early thrombus resolution, neutrophil influx stabilizes the tissue through NETosis. Meanwhile, macrophages and intact neutrophils recognize the extracellular DNA by the TLR9 receptor and induce fibrosis, a complimentary stabilization method. At later stages of resolution, pro-inflammatory macrophages police the thrombus for pathogens, a role supported by both T-cells and mast cells. Once they verify sterility, these macrophages transform into their pro-resolving phenotype. Endothelial cells both coat the stabilized thrombus, a necessary early step, and can undergo an endothelial-mesenchymal transition, which impedes DVT resolution. Several of these interactions hold promise for future therapy.

Acute experimental venous thrombosis impairs venous relaxation but not contraction

OBJECTIVE

Venous thrombosis (VT) damages the vein wall, both physically by prolonged distension and from inflammation. These factors contribute to post-thrombotic syndrome (PTS). Interleukin (IL)-6 might play a role in experimental PTS and vein wall responses. Previous assessments of post-thrombotic vein wall injury used static measures such as histologic examination and immunologic assays. The purpose of the present study was to use myography to quantify the changes in contraction and relaxation of murine vessels exposed to an acute VT.

METHODS

Wild-type (WT) C57BL/6 mice were used to determine the baseline vein wall passive tension on a DMT 610m myograph (DMT-USA, Inc., Ann Arbor, Mich), including dosing concentrations of phenylephrine (Phe) and acetylcholine (Ach). WT and IL-6^-/- mice underwent VT using inferior vena cava (IVC) ligation (complete stasis) and stenosis (partial stasis), with no-surgery mice used as controls. The mice were harvested at 2 days (2D) and analyzed using a myograph. The vessels were stimulated with Phe and Ach to stimulate a contraction and relaxation response. The endothelial responses to VT were quantified by CD31 immunohistochemistry, Greiss assay, polymerase chain reaction, and Evans blue assay.

RESULTS

Optimal passive tension was determined to be 2 mN, with an optimal concentration of Phe and Ach of 7E-3M and 1E-5M, respectively. No significant differences were found in the contractions when exposed to Phe between the WT control, WT 2D ligation, and WT 2D stenosis IVC segments and the IL-6^-/- mice with and without thrombus (P > .05 for all). When treated with Ach, significantly more relaxation was found in the nonthrombosed control IVC segments than in those IVC segments that had had a 2D thrombus from either ligation- or stenosis-derived thrombotic mechanisms in both WT and IL-6^-/- mice. CD31 staining showed ∼20% less luminal endothelium after stasis thrombosis (P ≤ .01) but no loss in the controls (P > .05). Evans blue staining showed a trend toward increased leakiness in post-thrombotic vein walls. No significant difference in the endothelial gene markers or nitric oxide production was found.

CONCLUSIONS

Compared with the controls, acute thrombosis in the total or partial stasis models did not impair IVC contractile responses, suggesting no effect on the medial vascular smooth muscle response. The relaxation response was significantly reduced in the post-thrombotic groups, likely from direct endothelial injury. These findings suggest, at acute points, that VT impairs the endothelial function of a vein wall while retaining the vascular smooth muscle cell function and might be a mechanism that promotes PTS.

Fibrinolysis and Inflammation in Venous Thrombus Resolution

Clinical observations and accumulating laboratory evidence support a complex interplay between coagulation, inflammation, innate immunity and fibrinolysis in venous thromboembolism (VTE). VTE, which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), and the subsequent complications of post-thrombotic syndrome (PTS), are significant causes of morbidity and mortality in patients. Clinical risk factors for VTE include cancer, major trauma, surgery, sepsis, inflammatory bowel disease, paralysis, prolonged periods of immobility, and aging. Abnormalities in venous blood flow or stasis initiates the activation of endothelial cells, and in concert with platelets, neutrophils and monocytes, propagates VTE in an intact vein. In addition, inflammatory cells play crucial roles in thrombus recanalization and restoration of blood flow via fibrinolysis and vascular remodeling. Faster resolution of the thrombus is key for improved disease prognosis. While in the clinical setting, anticoagulation therapy is successful in preventing propagation of venous thrombi, current therapies are not designed to inhibit inflammation, which can lead to the development of PTS. Animal models of DVT have provided many insights into the molecular and cellular mechanisms involved in the formation, propagation, and resolution of venous thrombi as well as the roles of key components of the fibrinolytic system in these processes. Here, we review the recent advances in our understanding of fibrinolysis and inflammation in the resolution of VTE.

Increased vein wall thickness in Behçet disease

OBJECTIVE

Lower extremity (LE) deep venous thrombosis (DVT) is the main feature of vascular involvement in Behçet disease (BD). We thought that vein wall thickness (VWT) could be a surrogate marker for venous inflammation and hence predict future vascular involvement. We assessed VWT in proximal LE veins in BD patients without DVT, BD patients with DVT, and healthy controls in a formal, masked protocol.

METHODS

We studied 50 (43 male and 7 female) BD patients with LE DVT (group 1), 50 (43 male and 7 female) BD patients without any vascular involvement (group 2), and 50 (43 male and 7 female) age- and sex-matched apparently healthy controls (group 3). Two radiologists blinded to the diagnosis of BD used ultrasound to measure VWT of common femoral vein, femoral vein, and great saphenous vein in both legs. Interobserver reliability was assessed using the intraclass correlation coefficient and Bland-Altman plots.

RESULTS

There was good agreement between the two observers. The mean VWT was significantly increased in both BD patients with LE DVT and those without apparent vascular involvement compared with the healthy controls, whereas those with LE DVT had the highest VWT.

CONCLUSIONS

VWT of proximal deep and superficial LE veins is increased among the BD patients without any clinical and radiologic vascular involvement. This information, after prospective work, might be useful in management and elucidating disease mechanisms in vascular BD.