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. Author manuscript; available in PMC: 2012 Jan 1.
Published in final edited form as: J Vasc Surg. 2010 Sep 24;53(1):139–146. doi: 10.1016/j.jvs.2010.07.043

Post Thrombotic Vein Wall Remodeling

Kristopher B Deatrick, Megan Elfline, Nichole Baker, Catherine E Luke, Susan Blackburn, Catherine Stabler, Thomas W Wakefield, Peter K Henke
PMCID: PMC3010467  NIHMSID: NIHMS230516  PMID: 20869834

Abstract

Background

Post-thrombotic syndrome (PTS) is characterized by a fibrotic vein injury following deep vein thrombosis (DVT). We sought to quantify the change in vein wall thickness in patients who fail to resolve DVT by 6 months and whether there were differences in blood or plasma levels of inflammatory proteins associated with venous remodeling.

Methods

Patients presenting with confirmed lower extremity DVT were prospectively recruited for this study. Duplex imaging of the lower extremity venous system was performed, and blood was collected at entrance and repeat evaluation with blood draw and ultrasound imaging at 1 and 6 months. DVT resolution and thickness of the vein wall was quantified by ultrasound imaging in each segment affected by thrombus, and a contralateral, unaffected vein wall served as a control. Gene and protein expression of inflammatory markers were examined from leukocytes and serum, respectively. ANOVA or Student’s t-tests were used, and a P <.05 was significant. N = 10 – 12 for all analyses.

Results

32 patients (12 patients with DVT resolution at 6 months, 10 patients with persistent thrombus at 6 months, and 10 healthy controls) were compared. Both resolving and non-resolving DVT were associated with 1.5 – 1.8 fold increased vein wall thickness at 6 months (P = .008) as compared with non affected vein wall segments. However, the thickness of the affected segments was 1.4 fold greater in patients who had total resolution of the DVT by 6 months than in patients who had persistent chronic thrombus 6 months after presentation (P = .01). There was a 4 – 5 fold increased level of matrix metalloproteinase-9 (MMP9) in thrombosed patients compared with non-thrombosed patient controls (P <.05), while Toll like receptor-9 (TLR-9) expression was 3 fold less than controls (P <.05) at enrollment. D-dimer and P-selectin were higher in thrombosed as compared to controls at diagnosis, but not at 6 months. Both TLR4 (marker of inflammation) and P-selectin gene expression were higher in leukocytes from patients with chronic DVT compared to those who resolved at one month after diagnosis (P <.05).

Conclusions

This preliminary study suggests ongoing vein wall remodeling after DVT, measurable by ultrasound and associated with certain biomarkers. At 6 months, the vein wall is markedly thickened, and directly correlates with resolution. This suggests that the vein wall response is initiated early following thrombus formation, and persists even in the presence of total resolution.

Introduction

Deep vein thrombosis (DVT) continues to affect 900,000 patients a year in the United States.1, 2 Somewhere between 30 and 50 percent of these patients will subsequently be affected by the post-thrombotic syndrome (PTS), which is defined clinically by the presence of leg swelling, pain, and ulceration.3, 4 Despite best medical management with anticoagulation, many will be affected by PTS.4 Once these symptoms begin, there is no specific treatment for the pathologic changes that occur within the vein wall, and treatment is entirely supportive, consisting of compression therapy and wound care if ulcers develop.5

The process of thrombus resolution in humans is still unclear, in part due to lack of human deep vein pathological specimens for study. While the association between DVT and postthrombotic changes is well recognized,6 the progression from acute thrombosis to chronic fibrosis is still unclear. Multi-segment DVT, recurrent DVT, and early onset of symptoms predict long-term PTS.4 Predicting those patients with acute DVT who may develop PTS is important for focusing aggressive therapy such as pharmacomechanical thrombolysis (PMT) to maximize benefit to risk and therapeutic success.7

Several reports have correlated serum inflammatory markers, such as intracellular adhesion molecular -1 (ICAM-1) and C-reactive protein, (CRP), with development of venous insufficiency and PTS.8 Although not necessarily causal, there is evidence from animal models to suggest the importance of the inflammatory response in the process of thrombus resolution.9 In a model of stasis DVT, prolonged thrombus-vein wall contact is associated with most severe vein wall injury.10 The cell adhesion molecule, P-selectin, is also involved with vein wall injury and is also a marker of thrombosis.11, 12 Modification of the post-thrombotic vein wall injury response is possible with P-selectin inhibition.11

In order to characterize circulating markers of vein wall injury after DVT, and correlate this with thrombus resolution and the ultrasonographic changes in the vein wall, we undertook a prospective study of patients with acute DVT, and hypothesized that biomarkers would be elevated and vein wall thickening would be greater in those with chronic DVT as a marker of greater injury, as compared to those who resolved their DVT within 6 months.

Methods

Patient enrollment

Patients 18 years old, but younger than 80 years of age, presenting to the diagnostic vascular unit at the University of Michigan with signs and symptoms of acute DVT were enrolled, and agreed to undergo repeat vascular ultrasound and phlebotomy. The study was approved by the University of Michigan Institutional Review Board (IRB) for Human Subjects Research and informed consent was obtained.

Inclusion criteria included those with an acute DVT in the popliteal, femoral or iliac system, who had at least an estimated 6 months to live, no known prior history of DVT, and be able to try to make follow-up appointments. Anticoagulation was heparin either low molecular weight (LMWH) or unfractionated heparin (UFH) followed by a vitamin K antagonist (VKA), and was directed by their admitting or treating physician. Exclusion criteria included those with a prior history of DVT, limited life expectancy, and inability to give consent.

Note that healthy controls were those with no history of DVT or any current DVT. This group was used for comparison of serum and leukocyte gene expression with those affected by an acute DVT. For duplex ultrasound comparisons, vein wall thickness determination was within the DVT groups, such that each patient was their own control. Thus, only for vein wall imaging comparison was the same patient used as their own control to decrease bias from inherent baseline vein morphology differences.

Blood collection and storage

On enrollment in the study, patients underwent phlebotomy of 5 – 10 mL of blood. Of this, 2.5 mL was collected in PaxGene (BD Biosciences, Becton Lakes, NJ) storage tubes, and 5 mL was fractionated with processing and analysis of the plasma fraction.

Diagnostic vascular ultrasound

The initial duplex study and patient accrual took place in an Intersociety Commission for Accredition of Vascular Laboratories certified vascular laboratory as entry point and is the only vascular lab at the University of Michigan. Duplex ultrasonography was performed to evaluate the presence of acute DVT. The limbs were evaluated by the standard protocol for those with a clinical suspicion of DVT, prior to consideration for study inclusion. Tissue Doppler imaging (TDI) was performed to define the presence of thrombus with a linear multi-hertz (7.5MHz) transducer with the Siemens Sonoline Antares (Siemens Medical Systems Inc, Issaquah, WA, USA) unit, the Toshiba Aplio, (Toshiba ultrasound systems SSA 790) unit, and Zonare Z.one (ZONARE Medical Systems Inc, CA, USA) unit. Typical criteria for a clinical human evaluation of DVT were used, including: a lack of compression, absence of flow, presence of dilated vein void of echoes (acute), and presence of a shrunken vein full of echoes (chronic).13 Images were performed in the sagittal and transverse planes in a detailed fashion. In the contralateral limb, similar imaging was done and recorded. After the diagnosis of DVT was confirmed, follow up duplex ultrasound was performed at one and six months (± 2 weeks). At the time of the follow up appointments, duplex images were obtained in the transverse and sagittal scan planes at each segment of the initially affected vein bilaterally, including the non-affected contralateral side (3 segments along affected and non-affected vein per patient). Notation of location and extent of the DVT was made at initial enrollment scan to allow for same venous segment evaluation at follow-up. All follow up images being analyzed were obtained in gray scale.

Image analysis was conducted using an open-source DICOM viewer (Osirix, Pixmeo-Sarl., Switzerland). Following the completion of a pilot study where inter-observer reliability (>90%) was confirmed by measurements of three independent, blinded observers, measurements of the vein walls were conducted in a standardized fashion. Three separate measurements of the most clearly identified vein wall in each segment of interest were made, recorded, and averaged by two independent observers, to provide a vein wall thickness measurement for each segment. For purposes of analysis, segments were compared to non-affected contralateral vein segments in the same patient. Both affected and non-affected veins were imaged in the, common femoral, femoral and popliteal veins of each patient analyzed.14, 15

Bioplex ELISA

After centrifugation, patient plasma was aliquoted and frozen at −70° C for storage. Quantification of peptides of interest was performed using a Bioplex multi-antigen ELISA (Biorad, Hercules, CA).16, 17 Antigens of interest were CRP, secondary leukocyte chemokine (SLC), P-selectin, D-dimer, matrix metalloproteinase (MMP)-2, and interleukin-6 (IL-6). Results were standardized to the total amount of protein in the sample, by a commercially available modified Bradford assay using serial dilutions of bovine serum albumin as a standard (Pierce, Inc., Rockford, IL).

Real time RT-PCR

A sample of the collected blood was placed in PAXgene Blood RNA System collecting tubes (BD Biosciences, Becton Lakes, NJ) according to the manufacturers’ instructions. The mRNA obtained was subject to reverse transcription by incubation with Oligo-dT primer and M-MLV reverse transcriptase (Life Technologies, Carlsbad, CA) at 94° C for 3 minutes, and then incubated at 40° C for 70 minutes. The cDNA obtained was amplified using TaqPolymerase (Promega, Madison, WI) in the Rotor-Gene quantitative real-time polymerase chain reaction system (Quiagen, Hilden, Germany). SYBR green intercalating dye was used to monitor levels of DNA amplification for each gene.18 Commercially available primers were purchased for the following genes of interest: B-Actin RefSeq# NM_001101.3, CRP RefSeq# NM_000567.2, IL-6 RefSeq# NM 000600.3, MMP9 RefSeq# NM_004994.2, MMP2 RefSeq# NM_004530.2, SELP, RefSeq# NM_003005.3, SELPLG RefSeq# NM_003006.3, TLR4 RefSeq# NM_138554.3, and TLR9 RefSeq# NM_017442.2.

Statistical Analysis

Comparisons were made between groups by ANOVA and paired and unpaired t-test where appropriate. A P<.05 was considered significant. The data are derived from N = 10 controls, 12 resolved DVT, and 10 non-resolved DVT patients.

Results

Acute Deep Vein Thrombosis is associated with vein wall thickening

Demographics of the patients are listed in Table I, and no significant differences found were between groups. No patients in those presenting with a DVT had a documented recurrent DVT at 6 month follow-up, based on symptoms or ultrasound characteristics in follow-up studies. Not surprisingly, the Wells score19 and Caprini risk score20 were higher in those with DVT than controls.

Table 1.

Patient Characteristics.

Characteristic Control (10) Resolved (12) Chronic (10) P Value
Female (%) 5 (50) 7 (58) 3 (30) 0.69
Age 49 (3.2) 52.1 (4.7) 59.9 (4.5) 0.21
Weight 190.7 (14.6) 206.3 (13.6) 186.5 (12.0) 0.78
White (%) 8 (80) 12 (100) 10 (100) 1.0
Smoker (%) 1 (10) 1 (8.3) 0 (0) 1.0
Recent Illness 1 (10) 8 (66) 7(70) 0.99
Hypercoagulable 0 1 2 0.97
Wells Criteria 2 (0.3) 3 (1.5) 4.3 (1.5) 0.066
Caprini Score 3.6 (1.1) 4.2 ( 0.6) 5.8 (1.0) 0.179
Anticoagulation 0 (0) 12 (100) 10 (100) 0.99
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Recent illness included pneumonia, myocardial infarction, urinary tract infection, or newly diagnosed malignancy.

Segmental duplex analysis included the popliteal, femoral, and common femoral veins. The segmental distribution of DVT was similar between those who did and did not resolve their DVT over 6 months. Patients with non-resolved DVT had an average of 2.9 +/− .34 vein segment affected compared with 2.1 +/− .33 vein segments in those who fully resolved their DVT (P = .09). All patients with a DVT were treated with heparin anticoagulation, followed by Coumadin. No patient had to prematurely stop their anticoagulation. Lower extremity compression was at the discretion of the treating physician, but neither compliance with, nor strength of the compression, was assessed.

The affected vein wall segment thickness in patients with acute DVT measured 1.5 - fold greater than those in unaffected contralateral non thrombosed segments at the time of enrollment (P = .005). At 6 months, this difference was even more profound, with a thickness 1.9 – fold greater than the measurable thickness in unaffected contralateral non-thrombosed vein segments (P = .001, Figure 1a – c). There was no significant difference in the mean thickness of the unaffected vein segments from patients with resolved or non-resolved DVT at enrollment (data not shown). Affected segments from patients with resolving thrombi were modestly thicker than those from patients with chronic thrombi at enrollment, with a significant difference achieved at 6 months (P = .011, Figure 1d).

Figure 1.

Figure 1

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A. Example of grey scale image of un-affected contralateral vein image in longitudinal segment. B. Example of a post thrombotic thickened vein wall segment in a patient with a resolved thrombus at 6 months. Arrows indicate the vein wall hyperechogenicity. C. Vein wall thickness in non thrombosed subjects and those with an acute DVT over time. D. Comparison of patient’s vein wall thickness in those who did and did not resolve their DVT at 6 months. * P < .05.

Plasma from patients with DVT at enrollment contains higher levels of MMP9 and d-dimer

Plasma from patients with acute DVT had circulating MMP9 levels in plasma that were 4.2 fold higher than healthy non DVT controls (P = .008, Figure 2a). Not surprisingly, circulating levels of D-dimer were 2 fold higher in DVT patients than in healthy non DVT controls, consistent with D-dimer as a sensitive (though not specific) measure of DVT19 (P= .04, Figure 2b). However, no differences between controls and those with an acute DVT in leukocyte gene expression of MMP9, P-selectin, IL6 or TLR4 were found (data not shown).

Figure 2.

Figure 2

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A. Comparison of serum MMP9 in patients without DVT as compared with patients with acute DVT. B. Comparison of serum D-dimer in subjects without DVT versus DVT patients. * = P < .05.

Serum biomarkers at enrollment and over time in patients with resolved versus chronic DVT

Patients with acute DVT as compared with non DVT controls had higher levels of circulating P-selectin, as measured by ELISA (Figure 3a). Patients with complete resolution of DVT had higher levels of circulating P-selectin at one month than patients with chronic thrombus (P = .041) (Figure 3b). By 6 months, there were no differences in circulating P-selectin between patients with resolution and patients with chronic occlusion (data not shown). Sera levels of IL6 and MMP9 were not different at enrollment or overtime between those who resolved and those who did not (data not shown).

Figure 3.

Figure 3

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A. P-selectin trended toward an increase at enrollment, but no difference was observed at 6 months. B. P-selectin was higher at one month in those patients who resolved their DVT as compared to those who had a chronic thrombus. * = P < .05.

Leukocyte gene expression at enrollment and over time in patients with resolved versus chronic DVT

Given the lack of vein wall pathologic specimens to evaluate, we analyzed gene expression of peripheral leukocytes in study patients. Leukocytes are both critical for DVT resolution as well as play a role in thrombogenesis, experimentally.10, 21 Circulating leukocytes in patients with acute DVT demonstrate significant alterations in the expression of genes associated with inflammation. Patients with acute thrombosis have only 45% of the level of P-selectin ligand gene expression (SELPG) of non DVT controls (P = .0012, Figure 4a). Toll-like receptor–9 (TLR-9) expression in circulating leukocytes from patients with acute DVT was only 18% of that in non DVT controls (P <.0001, Figure 4b). There were no significant differences in the leukocyte gene expression profiles of MMP9, MMP2, P-selectin, or IL-6 at enrollment between controls and acute DVT patients (data not shown).

Figure 4.

Figure 4

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A. Peripheral leukocyte P-selectin ligand gene expression was reduced in DVT patients compared with non DVT subjects at enrollment. B. TLR-9 expression was reduced in DVT patients as compared with non DVT subjects at enrollment. C. P-selectin was increased in at enrollment in those who resolved their thrombus as compared to those with chronic thrombus. D. TLR4 expression was reduced at enrollment in those patients who had persistent thrombus. * P = < .05

Circulating leukocytes from patients who resolved their DVT had lower levels of P-selectin gene expression (P = .01) (Figure 4c) at enrollment, as compared with those with chronic thrombosis. However, these differences had abrogated by 1 month and levels remained similar at 6 months. Additionally, the circulating leukocytes from patients who had a resolved thrombus at 6 months expressed lower levels of TLR-4 gene expression at enrollment (P = .019), but no differences were observed at 1 or 6 months. As compared to those who resolved and did not resolve their DVT, no differences were observed in leukocyte gene expression at enrollment or at one or 6 month follow up of IL6, TLR9, MMP2 or MMP9 (data not shown).

Discussion

In this prospective pilot study, we have shown via gene, serum, and ultrasound measures, several important associations between patients with acute DVT, those with DVT resolution, and those with persistent occlusive DVT at 6 months following initial thrombosis. To be able to predict, using biomarkers and thrombus characteristics, those most likely not to spontaneously recanalize would be beneficial, not only to determine length of anticoagulation, but also those most likely to gain benefit from PMT.7, 22 A recent retrospective study suggests the number of eligible patients for PMT may be smaller than anticipated;23 thus, patient selection is paramount. Further, treatment with LMWH compared with VKA may also decrease risk of PTS.24 As the extent and duration of thrombosis have previously been shown to correlate with the risk of PTS, patients with chronic DVT may have higher long term risk,5 as well as greater disability.25 These same patients also have higher risk of recurrent DVT.26, 27 Lastly, many patients have evidence of PTS by one month after an inciting DVT, and early events predict long term results.4

The finding that vein wall thickness was greater early in those segments affected by DVT supports the hypothesis that alterations in the vein wall (which can be of the extracellular matrix, the cellular fraction, or both) are a direct result of the DVT, rather than simply venous hypertension, which usually occurs over time.28 However, it is possible patients with thicker vein walls are primarily more likely to develop DVT. Contrary to our initial hypothesis, those who resolved their DVT had a thicker vein wall at 6 months. This may reflect scarring in those segments as the thrombus resolved, with thrombus adherence, luminal opening and fibrosis. Conversely, those with chronic DVT may have a thinner vein wall due to incomplete thrombus resolution, whereby the thrombus doesn’t fully attach to the vein wall, and thus full resolution does not occur. The vein wall itself is a source of plasmin and other proteases/proteinases that promote thrombus resolution.9, 29 Although by different pathology, venous varicosities show increases in histologically measured vein wall thickness.15, 30 Vein wall thickening has been observed in a stasis rat model of DVT; and the vein wall damage is greater with prolonged DVT contact, but no determination of thickness has yet been made in this model to corroborate the human data.10

We differentiated vein wall thickness from persistent thrombus by the following measures; first, we used standard criteria of thrombus echogenicity and one primary experienced sonographer (NB, RVT) performed most studies. Second, a pilot analysis evaluating the inter-observer reliability of vein wall segment measurements was performed, confirming reproducibility. Third, standardized criteria for evaluating the vein wall and thrombosis were developed prior to the initiation of this study. For example, in areas of persistent thrombosis, the wall is visualized as a more hyperechoic structure than adjacent thrombus. Only areas with clearly observable transition from a hypoechoic (thrombus) to hyperechoic (wall) area were measured, and when necessary, comparisons between longitudinal and transverse sections were made. Additionally, observers were trained to identify and follow the vein wall throughout the course of the US image, yielding reliable vein segments for analysis. Finally, comparative areas on the non-affected side were made to account for individual patient differences. While vein wall thickening is clinically apparent to surgeons treating venous disease operatively, no reported attempt to quantify this change has been made to date. We did not specifically assess for valvular reflux in this group, as this measure perse does not correlate with PTS or severity, while chronic obstructing DVT does.25, 31, 32

While elevation of serum P-selectin and D-dimer were not surprising in those with acute DVT as compared to patients without DVT,12 the elevation of serum circulating MMP9 is novel. The association of venous pathology with elevated MMP9 expression, however, has been observed human injured veins.33–35 Additionally, serum levels of MMP9 have been shown to be elevated in other nonthrombotic venous injury, including varicose veins and venous stasis ulcers.36, 37 Experimental data suggests that MMP9 may play a role in DVT resolution and possibly vein wall injury.10, 29 In the vascular system, MMP9 has elastinolytic and collagenolytic (primarily Type IV) activity.38 Thus, inflammatory cells that invade the peri-thrombotic space may release MMP9 (activated by plasmin) and mediate vein wall injury. However, as no differences in MMP9 gene or serum levels were found at enrollment nor at later time points between resolved and chronic DVT, this suggests this proteinase is likely most important acutely. Recent experimental studies suggest that genetic deletion of MMP9 is associated with less vein wall collagen deposition, but does not seem to play a role in DVT resolution (K. Barry Deatrick, unpublished data, 2010). What cells release this systemically is not defined by this study, but probably circulating leukocytes, which release it preformed, are the likely source.

Since thrombosis is associated with a localized sterile immune response,9 we have examined the response of the innate immune system, mediated by toll-like receptors, in response to thrombosis.39 Expression of the receptor TLR9 was significantly down regulated in patients with DVT, as compared with healthy patients without thrombosis. Though we cannot say whether this association represents a causal interaction, it does imply a relationship between the innate immune response and the host reaction to thrombosis. For example, the occurrence of DVT may impair TLR9 signaling processes, inhibiting the resolution of sterile inflammation. Alternatively, impaired TLR9 signaling may predispose to clinical DVT. Recent experimental data suggest that genetic deletion of TLR9 is associated with impaired thrombus resolution. (Henke, PK paper in submission). As TLR4 is an innate receptor for lipopolysaccharide as well as inflammation, it is not immediately clear why this marker was elevated in those patients with chronic DVT.

P-selectin has been long studied by our group and is both a sensitive and specific biomarker for DVT,12 as well causal in some models of experimental thrombosis.11, 40 In the current study, P-selectin was elevated early in patients with DVT as compared with normal patients without thrombosis, and confirms similar findings in a prior study.12 Interestingly, leukocyte P-selectin ligand (SELPG, the P-selectin receptor) gene expression was decreased in the setting of acute thrombosis. Again, whether the elevation of P-selectin and reduction of P-selectin ligand implies a causal relationship to DVT, or whether this pattern is only associated with the process of DVT resolution is not directly addressed in this study. However, as patients who resolved their DVT had higher serum P-selectin at one month after enrollment, this suggests that active thrombus metabolism is occurring compared with those with a chronic thrombus.

Limitations of this study include the relatively small number of patients enrolled and short 6 month duration of follow-up. Thus, the development and severity of PTS was not able to be evaluated in this study. Secondly, although all patients were on anticoagulation, compliance with long-term anticoagulation was not directly assessed and is a factor for both recurrence of DVT and PTS.41 All positive patients in this segment of the study were treated initially with therapeutic heparin or LMWH, and transitioned to oral vitamin K-antagonist (warfarin) therapy long term. The risk of PTS, however, is not entirely eliminated even in the presence of appropriate anticoagulation, and we were not able to determine the level of anticoagulation or intensity of compliance. Longer patient follow-up will allow better assessment of the hard clinical endpoint of PTS using quality of life measures. Lastly, other systemic co-founders such as active malignancy, infection or other non-tested hypercoagulable disorders may have been present. Further, our data does not allow us to say anything about causation – namely, whether the ultrasound changes observed in the vein wall are caused or only associated with inflammation and the markers described here.

These data have several potential clinical applications. First, good data exists that lack of recanalization of a proximal DVT is associated with a significantly increased risk of severe PTS.4, 32 Second, characterizing leukocyte and serum biomarkers that correlate with resolution may allow prediction of those who may develop PTS. Although very preliminary, these data indicate increased gene expression of P-selectin and TLR-4 are associated with chronic thrombosis. Similarly, patients with acute DVT have increased serum MMP9 levels and decreased TLR9 and P-selectin ligand leukocyte expression, as compared to non DVT subjects. Third, the ability to predict which patients are predisposed to impaired thrombus resolution may allow physicians to selectively treat only those patients most likely to benefit with expensive, higher risk therapies, such as PMT. On a more immediate level, those with persistent thrombus on ultrasonography should probably be maintained on anticoagulation, as compared to those without as the risk of recurrent DVT is significantly greater.26 Finally, long-term evaluation of the host response to sterile inflammation (e.g. TLR) may provide a mechanism to accelerate DVT resolution without the hemorrhagic risk of anticoagulation or thrombolysis.

Acknowledgments

Supported in part by NIH HL092129 (PKH) and UL1RR024986, and T32 HL076123 (TW)

Footnotes

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Presented at the 26th Annual Meeting of the American Venous Forum. February 14, 2010. Amelia Island, FL

REFERENCES

  • 1.Heit JA, Silverstein MD, Mohr DN, et al. The epidemiology of venous thromboembolism in the community. Thromb Haemost. 2001 Jul;86(1):452–463. [PubMed] [Google Scholar]
  • 2.Anderson FA, Jr, Wheeler HB, Goldberg RJ, et al. The Worcester DVT Study. A population-based perspective of the hospital incidence and case-fatality rates of deep vein thrombosis and pulmonary embolism. Arch Intern Med. 1991 May;151(5):933–938. [PubMed] [Google Scholar]
  • 3.Prandoni P, Lensing AW, Cogo A, et al. The long-term clinical course of acute deep venous thrombosis. Ann Intern Med. 1996 Jul 1;125(1):1–7. doi: 10.7326/0003-4819-125-1-199607010-00001. [DOI] [PubMed] [Google Scholar]
  • 4.Kahn SR, Shrier I, Julian JA, et al. Determinants and time course of the postthrombotic syndrome after acute deep venous thrombosis. Ann Intern Med. 2008 Nov 18;149(10):698–707. doi: 10.7326/0003-4819-149-10-200811180-00004. [DOI] [PubMed] [Google Scholar]
  • 5.Kahn SR. How I manage the post thrombotic syndrome. Blood. 2009 Sep 9; [Google Scholar]
  • 6.Meissner MH, Manzo RA, Bergelin RO, Markel A, Strandness DE., Jr Deep venous insufficiency: the relationship between lysis and subsequent reflux. J Vasc Surg. 1993 Oct;18(4):596–605. discussion 606-598. [PubMed] [Google Scholar]
  • 7.Patterson BO, Hinchliffe R, Loftus IM, Thompson MM, Holt PJ. Indications for catheter-directed thrombolysis in the management of acute proximal deep venous thrombosis. Arterioscler Thromb Vasc Biol. Apr;30(4):669–674. doi: 10.1161/ATVBAHA.109.200766. [DOI] [PubMed] [Google Scholar]
  • 8.Roumen-Klappe EM, Janssen MC, Van Rossum J, et al. Inflammation in deep vein thrombosis and the development of post-thrombotic syndrome: a prospective study. J Thromb Haemost. 2009 Apr;7(4):582–587. doi: 10.1111/j.1538-7836.2009.03286.x. [DOI] [PubMed] [Google Scholar]
  • 9.Wakefield TW, Myers DD, Henke PK. Mechanisms of venous thrombosis and resolution. Arterioscler Thromb Vasc Biol. 2008 Mar;28(3):387–391. doi: 10.1161/ATVBAHA.108.162289. [DOI] [PubMed] [Google Scholar]
  • 10.Henke PK, Varma MR, Moaveni DK, et al. Fibrotic injury after experimental deep vein thrombosis is determined by the mechanism of thrombogenesis. Thromb Haemost. 2007;98(5):1045–1055. [PubMed] [Google Scholar]
  • 11.Myers DD, Jr, Henke PK, Bedard PW, et al. Treatment with an oral small molecule inhibitor of P selectin (PSI-697) decreases vein wall injury in a rat stenosis model of venous thrombosis. J Vasc Surg. 2006 Sep;44(3):625–632. doi: 10.1016/j.jvs.2006.05.021. [DOI] [PubMed] [Google Scholar]
  • 12.Rectenwald JE, Myers DD, Jr, Hawley AE, et al. A pilot study. D-dimer, P-selectin, and microparticles: novel markers to predict deep venous thrombosis. Thromb Haemost. 2005 Dec;94(6):1312–1317. doi: 10.1160/TH05-06-0426. [DOI] [PubMed] [Google Scholar]
  • 13.Wheeler H, Anderson F. Use of Noninvasive Tests as a Basis for Treatment of DVT. In: Bernstein E, editor. Vascular Diagnosis. 4th ed. Vol. St. Loius: Mosby; [Google Scholar]
  • 14.Phillips DJ, Hossack J, Beach KW, Strandness DE., Jr Testing ultrasonic pulsed Doppler instruments with a physiologic string phantom. J Ultrasound Med. 1990 Aug;9(8):429–436. doi: 10.7863/jum.1990.9.8.429. [DOI] [PubMed] [Google Scholar]
  • 15.Bruschi E, Como G, Zuiani C, et al. Ultrasonographic analysis in vitro of parietal thickness of lower limb varicose veins. Radiol Med. 2006 Sep;111(6):846–854. doi: 10.1007/s11547-006-0079-3. [DOI] [PubMed] [Google Scholar]
  • 16.Ito T, Schaller M, Hogaboam CM, et al. TLR9 regulates the mycobacteria-elicited pulmonary granulomatous immune response in mice through DC-derived Notch ligand delta-like 4. J Clin Invest. 2009 Jan;119(1):33–46. doi: 10.1172/JCI35647. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Schaller MA, Neupane R, Rudd BD, et al. Notch ligand Delta-like 4 regulates disease pathogenesis during respiratory viral infections by modulating Th2 cytokines. J Exp Med. 2007 Nov 26;204(12):2925–2934. doi: 10.1084/jem.20070661. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Moaveni DK, Lynch EM, Luke C, et al. Vein wall re-endothelialization after deep vein thrombosis is improved with low-molecular-weight heparin. J Vasc Surg. 2008 Mar;47(3):616–624. doi: 10.1016/j.jvs.2007.11.040. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Wells PS, Anderson DR, Rodger M, et al. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. N Engl J Med. 2003 Sep 25;349(13):1227–1235. doi: 10.1056/NEJMoa023153. [DOI] [PubMed] [Google Scholar]
  • 20.Caprini JA. Thrombosis risk assessment as a guide to quality patient care. Dis Mon. 2005 Feb–Mar;51(2–3):70–78. doi: 10.1016/j.disamonth.2005.02.003. [DOI] [PubMed] [Google Scholar]
  • 21.Henke PK, Varma MR, Deatrick KB, et al. Neutrophils modulate post-thrombotic vein wall remodeling but not thrombus neovascularization. Thromb Haemost. 2006 Feb;95(2):272–281. doi: 10.1160/TH05-02-0099. [DOI] [PubMed] [Google Scholar]
  • 22.Geerts W. Antithrombotic and Thrombolytic Therapy. Chest. 2008;133:381s–451s. (8th Ed: ACCP Guidelines) [Google Scholar]
  • 23.Klein SJ, Gasparis AP, Virvilis D, Ferretti JA, Labropoulos N. Prospective determination of candidates for thrombolysis in patients with acute proximal deep vein thrombosis. J Vasc Surg. Apr;51(4):908–912. doi: 10.1016/j.jvs.2009.11.043. [DOI] [PubMed] [Google Scholar]
  • 24.Hull RD, Pineo GF, Brant R, et al. Home therapy of venous thrombosis with long-term LMWH versus usual care: patient satisfaction and post-thrombotic syndrome. Am J Med. 2009 Aug;122(8):762–769. e763. doi: 10.1016/j.amjmed.2008.12.023. [DOI] [PubMed] [Google Scholar]
  • 25.Delis KT, Bountouroglou D, Mansfield AO. Venous claudication in iliofemoral thrombosis: long-term effects on venous hemodynamics, clinical status, and quality of life. Ann Surg. 2004 Jan;239(1):118–126. doi: 10.1097/01.sla.0000103067.10695.74. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Prandoni P, Prins MH, Lensing AW, et al. Residual thrombosis on ultrasonography to guide the duration of anticoagulation in patients with deep venous thrombosis: a randomized trial. Ann Intern Med. 2009 May 5;150(9):577–585. doi: 10.7326/0003-4819-150-9-200905050-00003. [DOI] [PubMed] [Google Scholar]
  • 27.Labropoulos N, Gasparis AP, Tassiopoulos AK. Prospective evaluation of the clinical deterioration in post-thrombotic limbs. J Vasc Surg. 2009 Oct;50(4):826–830. doi: 10.1016/j.jvs.2009.05.059. [DOI] [PubMed] [Google Scholar]
  • 28.Abai B, Labropoulos N. Duplex ultrasound scanning for chronic venous obstriction and valvular incompetence. In: Gloviczki P, Forum AV, editors. Handbook of venous disorders : guidelines of the American Venous Forum. 3rd ed. London: Hodder Arnold; 2009. pp. 142–155. [Google Scholar]
  • 29.Dewyer NA, Sood V, Lynch EM, et al. Plasmin inhibition increases mmp-9 activity and decreases vein wall stiffness during venous thrombosis resolution. J Surg Res. 2007 Oct;142(2):357–363. doi: 10.1016/j.jss.2007.03.064. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30.Badier-Commander C, Couvelard A, Henin D, Verbeuren T, Michel JB, Jacob MP An in situ study. Smooth muscle cell modulation and cytokine overproduction in varicose veins. J Pathol. 2001 Mar;193(3):398–407. doi: 10.1002/path.819. [DOI] [PubMed] [Google Scholar]
  • 31.Kahn SR, Partsch H, Vedantham S, Prandoni P, Kearon C. Definition of post-thrombotic syndrome of the leg for use in clinical investigations: a recommendation for standardization. J Thromb Haemost. 2009 May;7(5):879–883. doi: 10.1111/j.1538-7836.2009.03294.x. [DOI] [PubMed] [Google Scholar]
  • 32.Labropoulos N, Waggoner T, Sammis W, Samali S, Pappas PJ. The effect of venous thrombus location and extent on the development of post-thrombotic signs and symptoms. J Vasc Surg. 2008 Aug;48(2):407–412. doi: 10.1016/j.jvs.2008.03.016. [DOI] [PubMed] [Google Scholar]
  • 33.Irwin C, Synn A, Kraiss L, Zhang Q, Griffen MM, Hunter GC. Metalloproteinase expression in venous aneurysms. J Vasc Surg. 2008 Nov;48(5):1278–1285. doi: 10.1016/j.jvs.2008.06.056. [DOI] [PubMed] [Google Scholar]
  • 34.Raffetto JD, Qiao X, Koledova VV, Khalil RA. Prolonged increases in vein wall tension increase matrix metalloproteinases and decrease constriction in rat vena cava: Potential implications in varicose veins. J Vasc Surg. 2008 Aug;48(2):447–456. doi: 10.1016/j.jvs.2008.03.004. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 35.Kowalewski R, Sobolewski K, Wolanska M, Gacko M. Matrix metalloproteinases in the vein wall. Int Angiol. 2004 Jun;23(2):164–169. [PubMed] [Google Scholar]
  • 36.Woodside KJ, Hu M, Burke A, et al. Morphologic characteristics of varicose veins: possible role of metalloproteinases. J Vasc Surg. 2003 Jul;38(1):162–169. doi: 10.1016/s0741-5214(03)00134-4. [DOI] [PubMed] [Google Scholar]
  • 37.Kosugi I, Urayama H, Kasashima F, Ohtake H, Watanabe Y. Matrix metalloproteinase-9 and urokinase-type plasminogen activator in varicose veins. Ann Vasc Surg. 2003 May;17(3):234–238. doi: 10.1007/s10016-003-0005-2. [DOI] [PubMed] [Google Scholar]
  • 38.Galis ZS, Khatri JJ. Matrix metalloproteinases in vascular remodeling and atherogenesis: the good, the bad, and the ugly. Circ Res. 2002 Feb 22;90(3):251–262. [PubMed] [Google Scholar]
  • 39.Beutler B. Toll-like receptors and their place in immunology. Where does the immune response to infection begin? Nat Rev Immunol. 2004 Jul;4(7):498. doi: 10.1038/nri1401. [DOI] [PubMed] [Google Scholar]
  • 40.Myers DD, Hawley AE, Farris DM, et al. P-selectin and leukocyte microparticles are associated with venous thrombogenesis. J Vasc Surg. 2003 Nov;38(5):1075–1089. doi: 10.1016/s0741-5214(03)01033-4. [DOI] [PubMed] [Google Scholar]
  • 41.van Dongen CJ, Prandoni P, Frulla M, Marchiori A, Prins MH, Hutten BA. Relation between quality of anticoagulant treatment and the development of the postthrombotic syndrome. J Thromb Haemost. 2005 May;3(5):939–942. doi: 10.1111/j.1538-7836.2005.01333.x. [DOI] [PubMed] [Google Scholar]

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