Long-term outcome after additional catheter-directed thrombolysis versus standard treatment for acute iliofemoral deep vein thrombosis (the CaVenT study): a randomised controlled trial

Fibrinolytic Agents in Thromboembolic Diseases: Historical Perspectives and Approved Indications

Fibrinolytic agents catalyze the conversion of the inactive proenzyme plasminogen into the active protease plasmin, degrading fibrin within the thrombus and recanalizing occluded vessels. The history of these medications dates to the discovery of the first fibrinolytic compound, streptokinase, from bacterial cultures in 1933. Over time, researchers identified two other plasminogen activators in human samples, namely urokinase and tissue plasminogen activator (tPA). Subsequently, tPA was cloned using recombinant DNA methods to produce alteplase. Several additional derivatives of tPA, such as tenecteplase and reteplase, were developed to extend the plasma half-life of tPA. Over the past decades, fibrinolytic medications have been widely used to manage patients with venous and arterial thromboembolic events. Currently, alteplase is approved by the U.S. Food and Drug Administration (FDA) for use in patients with pulmonary embolism with hemodynamic compromise, ST-segment elevation myocardial infarction (STEMI), acute ischemic stroke, and central venous access device occlusion. Reteplase and tenecteplase have also received FDA approval for treating patients with STEMI. This review provides an overview of the historical background related to fibrinolytic agents and briefly summarizes their approved indications across various thromboembolic diseases.

Fibrinogen levels and clot properties identify patients who benefit from catheter-directed thrombolysis after DVT

ABSTRACT

Ultrasound-accelerated catheter-directed thrombolysis (UA-CDT) to improve patency after deep vein thrombosis (DVT) has not conclusively been shown to prevent postthrombotic syndrome (PTS) but might benefit patients who are unlikely to obtain patency with standard treatment. We hypothesized that these patients could be selected based on their fibrin clot properties. To study this, patients with acute iliofemoral DVT from the CAVA (Ultrasound-Accelerated Catheter-Directed Thrombolysis Versus Anticoagulation for the Prevention of Post-thrombotic Syndrome) trial had blood samples taken at inclusion. Fibrin clot properties in plasma were determined by turbidimetric clotting (lag time and maximal turbidity) and lysis assays (time to 50% lysis and lysis rate), permeation assay, and confocal microscopy (fiber density), as well as levels of fibrin clot modifiers fibrinogen and C-reactive protein (CRP). Patency was defined as >90% iliofemoral vein compressibility at 12-month ultrasound. PTS was defined as ≥5 Villalta score at 6 or 12 months. In total, 91 of 152 patients were included, including 43 with additional UA-CDT and 48 with standard treatment. Patients with additional UA-CDT more often obtained patency (55.8 vs 27.1%) Patients who obtained patency had longer lag times and lower maximal turbidity, fibrinogen, and CRP; only maximal turbidity and fibrinogen remained associated when adjusting for treatment, thrombus load, and body mass index. Fibrinogen levels had an optimal cutoff at 4.85 g/L. Low fibrinogen levels best predicted patency. Additional UA-CDT decreased the risk of PTS only in patients with high fibrinogen. Therefore, additional UA-CDT might prevent PTS in selected patients based on routinely measured fibrinogen levels. This study was registered at www.ClinicalTrials.gov as #NCT00970619.

Preliminary clinical analysis and pathway study of S100A8 as a biomarker for the diagnosis of acute deep vein thrombosis

Herein, we aimed to identify blood biomarkers that compensate for the poor specificity of D-dimer in the diagnosis of deep vein thrombosis (DVT). S100A8 was identified by conducting protein microarray analysis of blood samples from patients with and without DVT. We used ELISA to detect S100A8, VCAM-1, and ICAM-1 expression levels in human blood and evaluated their correlations. Additionally, we employed human recombinant protein S100A8 to induce human umbilical vein endothelial cells and examined the role of the TLR4/MAPK/VCAM-1 and ICAM-1 signaling axes in the pathogenic mechanism of S100A8. Simultaneously, we constructed a rat model of thrombosis induced by inferior vena cava stenosis and detected levels of S100A8, VCAM-1, and ICAM-1 in the blood of DVT rats using ELISA. The associations of thrombus tissue, neutrophils, and CD68-positive cells with S100A8 and p38MAPK, TLR4, and VCAM-1 expression levels in vein walls were explored. The results revealed that blood S100A8 was significantly upregulated during the acute phase of DVT and activated p38MAPK expression by combining with TLR4 to enhance the expression and secretion of VCAM-1 and ICAM-1, thereby affecting the occurrence and development of DVT. Therefore, S100A8 could be a potential biomarker for early diagnosis and screening of DVT.

Calf deep veins are safe and feasible accesses for the endovascular treatment of acute lower extremity deep vein thrombosis

This study was designed to assess the optimal access route for the endovascular treatment of acute lower extremity deep vein thrombosis. This was a retrospective analysis of patients with acute lower extremity deep venous thrombosis who underwent endovascular treatment from February 2009 to December 2020. Patients underwent non-direct calf deep vein puncture (NDCDVP) from February 2009 to December 2011 and direct calf deep vein puncture (DCDVP) from January 2012 to December 2020. Catheter directed thrombolysis (CDT) was used to treat all patients in the NDCDVP group, whereas patients in the DCDVP group were treated with CDT or the AngioJet rhyolitic thrombectomy system. In patients exhibiting iliac vein compression syndrome, the iliac vein was dilated and implanted with a stent. Technical success rates and perioperative complication rates were compared between these two treatment groups. The NDCDVP group included 83 patients (40 males, 43 females) with a mean age of 55 ± 16 years, while the DCDVP group included 487 patients (231 males. 256 females) with a mean age of 56 ± 15 years. No significant differences were observed between these groups with respect to any analyzed clinical characteristics. The technical success rates in the NDCDVP and DCDVP groups were 96.4 and 98.2%, respectively (P > 0.05). In the NDCDVP group, the small saphenous vein (SSV)or great saphenous vein (GSV)were the most common access routes (77.1%, 64/83), whereas the anterior tibial vein (ATV) was the most common access route in the DCDVP group (78.0%, 380/487), followed by the posterior tibial vein (PTV) and peroneal vein (PV)(15.6% and 6.4%, respectively). Relative to the NDCDVP group, more patients in the DCDVP group underwent the removal of deep vein clots below the knee (7.2% [6/83] vs. 24.2% [118/487], P < 0.001). Moreover, relative to the NDCDVP group, significantly lower complication rates were evident in the DCDVP group (local infection: 10.8% vs. 0.4%, P < 0.001; local hematoma: 15.7% vs. 1.0%, P < 0.001). The position change rate was also significantly lower in the DCDVP group relative to the NDCDVP group (0% [0/487] vs. 60.2% [50/83], P < 0.001). The calf deep veins (CDVs) represent a feasible and safe access route for the endovascular treatment of lower extremity deep vein thrombosis.

Acute phase determinant of post-thrombotic syndrome: A review of the literature

BACKGROUND

Post-thrombotic syndrome (PTS) is the main long-term complication of deep vein thrombosis (DVT). Several therapies are being evaluated to prevent or to treat PTS. Identifying the patients most likely to benefit from these therapies presents a significant challenge.

OBJECTIVES

The objective of this review was to identify risk factors for PTS during the acute phase of DVT.

ELIGIBILITY CRITERIA

We searched the PubMed and Cochrane databases for studies published between January 2000 and January 2021, including randomized clinical trials, meta-analyses, systematic reviews and observational studies.

RESULTS

Risk factors for PTS such as proximal location of DVT, obesity, chronic venous disease, history of DVT are associated with higher risk of PTS. On the initial ultrasound-Doppler, a high thrombotic burden appears to be a predictor of PTS. Among the evaluated biomarkers, some inflammatory markers such as ICAM-1, MMP-1 and MMP-8 appear to be associated with a higher risk of developing PTS. Coagulation disorders are not associated with risk of developing PTS. Role of endothelial biomarkers in predicting PTS has been poorly explored. Lastly, vitamin K antagonist was associated with a higher risk of developing PTS when compared to direct oral anticoagulants and low molecular weight heparin.

CONCLUSIONS

Several risk factors during the acute phase of VTE are associated with an increased risk of developing PTS. There is a high-unmet medical need to identify potential biomarkers for early detection of patients at risk of developing PTS after VTE. Inflammatory and endothelial biomarkers should be explored in larger prospective studies to identify populations that could benefit from new therapies.

Histotripsy and Catheter-Directed Lytic: Efficacy in Highly Retracted Porcine Clots In Vitro

OBJECTIVE

Standard treatment for deep vein thrombosis (DVT) involves catheter-directed anticoagulants or thrombolytics, but the chronic thrombi present in many DVT cases are often resistant to this therapy. Histotripsy has been found to be a promising adjuvant treatment, using the mechanical action of cavitating bubble clouds to enhance thrombolytic activity. The objective of this study was to determine if histotripsy enhanced recombinant tissue plasminogen activator (rt-PA) thrombolysis in highly retracted porcine clots in vitro in a flow model of occlusive DVT.

METHODS

Highly retracted porcine whole blood clots were treated for 1 h with either catheter-directed saline (negative control), rt-PA (lytic control), histotripsy, DEFINITY and histotripsy or the combination of rt-PA and histotripsy with or without DEFINITY. Five-cycle, 1.5 MHz histotripsy pulses with a peak negative pressure of 33.2 MPa and pulse repetition frequency of 40 Hz were applied along the clot. B-Mode and passive cavitation images were acquired during histotripsy insonation to monitor bubble activity.

RESULTS

Clots subjected to histotripsy with and without rt-PA exhibited greater thrombolytic efficacy than controls (7.0% flow recovery or lower), and histotripsy with rt-PA was more efficacious than histotripsy with saline (86.1 ± 10.2% compared with 61.7 ± 19.8% flow recovery). The addition of DEFINITY to histotripsy with or without rt-PA did not enhance either thrombolytic efficacy or cavitation dose. Cavitation dose generally did not correlate with thrombolytic efficacy.

CONCLUSION

Enhancement of thrombolytic efficacy was achieved using histotripsy, with and without catheter-directed rt-PA, in the presence of physiologic flow. This suggests these treatments may be effective as therapy for DVT.

Mechanical Venous Thrombectomy for Deep Venous Thrombosis in Cancer Patients: A Single-Center Retrospective Study

PURPOSE

Venous thromboembolism (VTE) is a major contributor to the mortality of cancer patients. Mechanical thrombectomy (MT) is an endovascular technique that physically removes a thrombus without thrombolytics. The purpose of this study was to evaluate safety, efficacy, and clinical outcomes following MT for lower extremity DVT in cancer patients.

METHODS

This single-center, retrospective study evaluated outcomes following MT of lower extremity DVT in cancer patients from November 2019 to May 2023. The primary outcome measure was clinical success, defined as a decrease in Villalta score by at least 2 points following the intervention. Secondary outcomes included repeat intervention-free survival and overall survival. Technical success was defined as restoring venous flow with mild (< 10%) or no residual filling defect.

RESULTS

In total, 90 patients and 113 procedures were included. Technical and clinical success was achieved in 81% and 87% of procedures performed. Repeat intervention-free survival at 1 month, 3 months, and 6 months post-procedure was 92%, 82%, and 77%, respectively. The complication rate was 2.7%. Pathologic analysis of the extracted thrombus revealed tumor thrombus in 18.4% (18/98) samples. Overall survival for the study cohort was 87% at 1 month, 74% at 3 months, and 62% at 6 months. Patients who were found to have tumor thrombi were noted to have a decreased overall survival compared to patients with non-tumor thrombi (P = 0.012).

CONCLUSION

MT is safe and efficacious in reducing cancer patients' VTE-related symptoms. The high rate of tumor thrombus in thrombectomy specimens suggests this phenomenon is more common than suspected.

Experimental multiparametric magnetic resonance imaging characterization of iliocaval venous thrombosis pathological changes

OBJECTIVE

Iliocaval thrombotic obstruction is a challenging condition, especially because thrombus age and corresponding pathological remodeling at presentation are unknown, which directly impacts management. Our aim was to assess the ability of magnetic resonance imaging (MRI) in determining age thresholds of experimentally created inferior vena cava (IVC) thrombosis in pigs.

METHODS

We used a previously described swine model of IVC thrombosis. The animals underwent MRI at baseline, immediately after thrombosis creation, and after a follow-up period extending from 2 to 28 days. Thirteen pigs were divided into three groups according to disease chronicity: acute group (AG; n = 5), subacute group (SAG; n = 4), and chronic group (CG; n = 4), with a mean thrombosis age of 6.4 ± 2.5 days, 15.7 ± 2.8 days, and 28 ± 5.7 days, respectively. A T1-weighted volumetric interpolated breath-hold examination sequence was used to anatomically delineate IVC thrombus as a region of interest. Three other MRI sequences were used to assess the thrombus signal.

RESULTS

The Kruskal-Wallis test showed a statistically significant difference in T1 relaxation times after contrast injection (P = .026) between the three groups of chronicity. The AG (360.2 ± 102.5 ms) was significantly different from the CG (336.7 ± 55.2 ms; P = .003), and the SAG (354.1 ± 89.7 ms) was significantly different from the AG (P = .027). There was a statistically significant difference in native T2 relaxation times (P = .038) between the three groups. The AG (160 ± 86.7 ms) was significantly different from the SAG (142.3 ± 55.4 ms; P = .027), and the SAG was significantly different from the CG (178.4 ± 11.7 ms; P = .004).

CONCLUSIONS

This study highlighted MRI characteristics in a swine model that might have the potential to significantly differentiate subacute and chronic stages from an acute stage of deep vein thrombosis in humans. Further clinical studies in humans are warranted.

CLINICAL RELEVANCE

In addition to providing a better understanding of venous thrombosis remodeling over time, magnetic resonance imaging has the potential to be a tool that could allow us to characterize the composition of venous thrombus over an interval, allowing for a refined analysis of the local evolution of venous thrombosis. We propose a noninvasive and innovative method to characterize different thresholds of chronicity with magnetic resonance imaging features of central deep vein thrombosis of the inferior vena cava experimentally obtained using a totally endovascular in vivo swine model, mimicking human pathophysiology. Being able to determine these features noninvasively is critical for vascular specialists when it comes to choosing between fibrinolytic therapy, percutaneous thrombectomy, or surgical management.

Intraprocedural Use of the Novel Protrieve Sheath Removes Embolus During Mechanical Thrombectomy of a Complex Iliocaval Deep Vein Thrombosis

Extension of proximal deep vein thrombosis (DVT) into the inferior vena cava (IVC) complicates treatment with mechanical thrombectomy, as the presence of IVC thrombus increases embolization risks. In the case of a 39-year-old man with left-sided iliocaval DVT, the novel Protrieve sheath (Inari Medical, Irvine, California) was intraprocedurally placed in the IVC to ensure such complications would not outweigh the benefits of intervention. During successful thrombectomy, the sheath's wall-apposing funnel trapped and removed procedural embolus from the IVC, with no complications occurring. Studies to determine whether the device can broadly improve the safety of complex DVT procedures are warranted.

Ultrasound Combined With Continuous Microbubble Injection to Enhance Catheter-Directed Thrombolysis in Vitro and in Vivo

OBJECTIVES

To investigate the influence of microbubble perfusion mode on catheter-directed thrombolysis (CDT), we evaluated the effect of two different types of microbubble perfusion modes (continuous injection versus bolus injection) on the thrombolytic efficacy of CDT in vitro and further assessed the effect of continuous microbubble injection on CDT in vivo.

METHODS

In an in vitro experimental setup, 50 fresh bovine whole blood clots were randomized into five groups: ultrasound and continuous microbubble injection-enhanced CDT (US + cMB + CDT), ultrasound and bolus microbubble injection-enhanced CDT (US + bMB + CDT), US + CDT, US + cMB, and CDT. In a porcine femoral vein thrombosis model, 16 completely obstructive thrombi were randomly assigned to the CDT group and the US + cMB + CDT group, respectively. Thrombolysis rate, vascular recanalization rate, hematoxylin-eosin, and immunofluorescence staining were used to evaluate the thrombolytic effect in vitro and in vivo.

RESULTS

In vitro, US + cMB + CDT group resulted in a significantly higher thrombolysis rate compared with the other four groups (P < .05). Meanwhile, this group also demonstrated a looser clot structure and more disrupted fibrin structures. In vivo, US + cMB + CDT contributed to a significantly higher vascular recanalization rate compared with CDT (87.50% versus 25.00%, P < .05).

CONCLUSIONS

US + cMB + CDT was more effective than US + bMB + CDT in thrombolysis, and ultrasound combined with continuous microbubble injection could enhance the thrombolytic efficacy of CDT.

Aspiration Thrombectomy Using Inari FlowTriever System for Inferior Vena Cava Tumor Thrombus: A Case Report

Pharmacomechanical therapy and catheter-directed thrombolysis are potent treatments for venous thromboembolism. However, limited data exist regarding the management of thrombi in the inferior vena cava (IVC). IVC thrombus resulting from tumors is a particularly uncommon condition. Managing IVC tumor thrombi poses even greater challenges, as conventional therapies such as systemic anticoagulation and thrombolysis are often ineffective. In this report, we present the case of a 73-year-old male with an inferior vena cava tumor thrombus successfully managed through aspiration thrombectomy utilizing the Inari FlowTriever system.

Dual-Frequency Ultrasound Assisted Thrombolysis in Interventional Therapy of Deep Vein Thrombosis

Deep vein thrombosis (DVT) is one of the main causes of disability and death worldwide. Currently, the treatment of DVT still needs a long time and faces a high risk of major bleeding. It is necessary to find a rapid and safe method for the therapy of DVT. Here, a dual-frequency ultrasound assisted thrombolysis (DF-UAT) is reported for the interventional treatment of DVT. A series of piezoelectric elements are placed in an interventional catheter to emit ultrasound waves with two independent frequencies in turn. The low-frequency ultrasound drives the drug-loaded droplets into the thrombus, while the high-frequency ultrasound causes the cavitation of the droplets in the thrombus. With the joint effect of the enhanced drug diffusion and the cavitation under the dual-frequency ultrasound, the thrombolytic efficacy can be improved. In a proof-of-concept experiment performed with living sheep, the recanalization of the iliac vein is realized in 15 min using the DF-UAT technology. Therefore, the DF-UAT can be one of the most promising methods in the interventional treatment of DVT.

Drug-coated balloon therapy for in-stent restenosis in patients with iliofemoral deep vein thrombosis: A single-arm observational study

BACKGROUND

Iliofemoral deep vein thrombosis (IFDVT) causes severe symptoms and affect the quality of life to a great extent. Endovascular thrombectomy and stent implantation have been a feasible strategie to alleviate the signs and symptoms of IFDVT. However, venous in-stent restenosis (ISR) has become an emerging non-negligible problem.

METHODS

To evaluate the histological characteristics of venous ISR, neointima of arterial and venous ISR patients were collected and examed. To explore the effect of drug-coated balloon (DCB) on venous ISR lesions, we conducted a single-center retrospective case series study involving IFDVT patients with ISR after venous stenting who were treated with paclitaxel-coated balloon dilatation.

RESULTS

We found a collagen-rich matrix but not elastin, as well as fewer cells and less neovascularization in venous intimal hyperplasia compared with neointima in arteries. Thirteen IFDVT patients were involved in the study, with average preoperative stenosis degree of 87.69% ± 13.48%. After intervention, the stenosis degree was significantly reduced to 14.6% ± 14.36% immediately (p < 0.0001) and to 16.54% ± 15.73% during follow-up (p < 0.0001). During follow-up, the VEINES-QOL scores (p < 0.0001), VEINES-Sym scores (p < 0.0001), and Villalta scores (p = 0.04) of patients was improved significantly compared with those before intervention. No major adverse events were observed.

CONCLUSIONS

The use of DCB may have a positive effect in the treatment of venous ISR by targeting intimal hyperplasia. Moreover, the application of DCB dilatation in IFDVT stenting patients with ISR is deemed safe and effective.

Syringe-assisted test-aspiration with mechanical aspiration thrombectomy results in good safety and short-term outcomes in the treatment of patients with deep venous thrombosis

OBJECTIVE

To evaluate the short-term outcomes and safety of syringe-assisted test-aspiration with mechanical aspiration thrombectomy in the treatment of deep venous thrombosis.

METHODS

This was a single-center, retrospective study of hospitalized patients with iliofemoral and/or inferior vena caval deep venous thrombosis, excluding those with pulmonary embolism. We collected the following patient data from the electronic medical records: age, sex, provoked/unprovoked deep venous thrombosis, symptom duration, thrombosed segments, and the presence of a tumor, thrombophilia, diabetes, and/or iliac vein compression syndrome. Venography and computed tomographic venography were performed in all patients before the procedure. All patients underwent syringe-assisted test-aspiration with mechanical aspiration thrombectomy under local anesthesia and sedation, and all received low-molecular-weight heparin peri-operatively. All patients underwent implantation of an inferior vena caval filter. Rivaroxaban was administered post-procedure, instead of heparin, for 3-6 months, with lower extremity compression.

RESULTS

Overall, 29 patients with deep venous thrombosis underwent syringe-assisted test-aspiration with mechanical aspiration thrombectomy from January 2022 to October 2022 in our institution. Technical success (>70% thrombus resolution) was achieved in all patients, and using a single procedure in 25/29 patients (86%). Concomitant stenting was performed in 18/29 (62%) of the patients, and 21/29 (69%) underwent angioplasty. The median (interquartile range) procedure time was 110 min (100-122), the median intra-operative bleeding volume was 150 mL (120-180), and the median decrease in the hemoglobin concentration from pre- to post-operative was 7 g/L (4-14). The median follow-up duration was 7 months (5-9). All patients obtained symptomatic relief, and 27/29 achieved near-remission or full remission (combined total). No patients experienced peri-operative bleeding complications, or symptom recurrence or post-thrombectomy syndrome during follow-up.

CONCLUSION

The short-term outcomes following syringe-assisted test-aspiration with mechanical aspiration thrombectomy in the treatment of deep venous thrombosis were excellent, and the procedure was safe.

Initial experience with the ambulatory management of acute iliofemoral deep vein thrombosis with May-Thurner syndrome with percutaneous mechanical thrombectomy, angioplasty and stenting

OBJECTIVE

Patients undergoing intervention for acute iliofemoral deep vein thrombosis (IFDVT) with May-Thurner syndrome (MTS) typically require inpatient (IP) hospitalization for initial treatment with anticoagulation and management with pharmacomechanical thrombectomy. Direct oral anticoagulants and percutaneous mechanical thrombectomy (PMT) devices offer the opportunity for outpatient (OP) management. We describe our approach with these patients.

METHODS

Patients receiving intervention for acute IFDVT from January 2020 through October 2022 were retrospectively reviewed. Patients undergoing unilateral thrombectomy, venous angioplasty, and stenting for IFDVT with MTS comprised the study population and were divided into two groups: (1) patients admitted to the hospital and treated as IPs and (2) patients who underwent therapy as OPs. The two groups were compared regarding demographics, risk factors, procedural success, complications, and follow-up.

RESULTS

A total of 92 patients were treated for IFDVT with thrombectomy, angioplasty, and stenting of whom 58 comprised the IP group and 34 the OP group. All 92 patients underwent PMT using the Inari ClotTriever (Inari Medical), intravascular ultrasound, angioplasty, and stenting with 100% technical success. Three patients in the IP group required adjuvant thrombolysis. There was no difference in primary patency of the treated IFDVT segment at 12 months between the two groups (IP, 73.5%; OP, 86.7%; P = .21, log-rank test).

CONCLUSIONS

Patients with acute IFDVT and MTS deemed appropriate for thrombectomy and iliac revascularization can be managed with initiation of ambulatory direct oral anticoagulant therapy and subsequent return for ambulatory PMT, angioplasty, and stenting. This approach avoids the expense of IP care and allows for effective use of resources at a time when staffing and supply chain shortages have led to inefficiencies in the provision of IP care for nonemergent conditions.

The role and principles of stenting in acute iliofemoral thrombosis

Catheter-directed interventions for acute iliofemoral deep venous thrombosis (DVT) have been increasingly used over the past 15 years to target severe symptomatology and prevention of post-thrombotic syndrome incidence or reduce its severity if it were to develop. Aside from successful thrombus removal, adjunctive stents are frequently required to treat an uncovered lesion or significant residual thrombus to ensure quality of life improvement besides retarding DVT recurrence and post-thrombotic syndrome. As the evidence is mounting, the need and role for stenting, as well as the principles of an optimal technique, in the acute DVT setting are now better understood. Accumulating experience appears to favor stenting in the acute setting. The diameter of the stent, the length, the extent of overlapping, and the landing zones are crucial determinants of a successful durable outcome. This article endeavors to guide the interventionalist on stenting when encountering a patient with acute symptomatic iliofemoral DVT with concerns of quality of life impairment.

Single-session mechanical thrombectomy for iliofemoral deep vein thrombosis using a dual mechanism of action device combining basket and rotational thrombectomy

OBJECTIVE

Interventional treatments for acute iliofemoral deep vein thrombosis (DVT) remain controversial after publication of the Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) study. Interventions have been shown to reduce post-thrombotic syndrome severity and improve quality of life in DVT patients, but have been accompanied by risk of major bleeding from thrombolytics. We describe thrombus removal using a novel combined basket-rotational thrombectomy device that minimizes the need for thrombolytics or repeat procedures.

METHODS

The aim of this prospective, nonrandomized, multicenter, first-in-human study of 19 patients with acute iliofemoral DVT was to evaluate the safety and performance of the Pounce venous thrombectomy system ≤12 months after treatment. The primary performance end point was defined as procedural success through achievement of Society of Interventional Radiology (SIR) grade II lysis in treated vessels with freedom from procedural adverse events. Secondary end points included venous disease severity assessments using the Villalta scale and the Venous Clinical Severity Score, patient quality-of-life measurement using the Venous Insufficiency Epidemiological and Economic Study-Quality of Life questionnaire, and calf circumference measurements taken at baseline, 24 hours, and 1 month.

RESULTS

The primary end point of complete or near-complete thrombus removal (Society of Interventional Radiology grade II or III) was achieved in all patients. All study device-related safety end points were met, with no major bleeding or device-related adverse events. Of the 19 patients treated, 16 (84.2%) did not receive thrombolytics during the procedure. Post-thrombotic syndrome (Villalta scale >4) was identified in 17 of 19 patients (89.5%) at baseline, 4 of 13 patients (30.8%) available for follow-up at 6 months, and 2 of 11 patients (18.2%) at 12 months. The median Venous Clinical Severity Score decreased (P < .001) from 8.5 (interquartile range [IQR], 7-10) at baseline to 4 (IQR, 2-4) at 1 month after the procedure and was similar at 6 months (2; IQR, 2-5) and 12 months (2; IQR, 1.5-3) after the procedure. The median Venous Insufficiency Epidemiological and Economic Study-Quality of Life questionnaire score improved (P < .001) by 39 from baseline (57; IQR, 53.5-74) to 1 month (96; IQR, 86-101) after the procedure, and remained high at 6 months (99; IQR, 75-103) and 12 months (98; IQR, 94.5-100). The median calf circumference decreased (P = .089) from 39 cm (IQR, 35-47.8 cm) at baseline to 36 cm (IQR, 32.5-40.5 cm) at 24 hours after the procedure and was 34.5 cm (IQR, 33.2-38.5 cm) at 1 month.

CONCLUSIONS

The Pounce device is safe and effective for removal the of thrombus in patients with acute iliofemoral DVT. Initial results demonstrate improvements in venous disease severity and patient quality of life.

Pharmacomechanical thrombectomy of iliofemoral deep vein thrombosis is associated with a low incidence of post-thrombotic syndrome and perioperative complications

BACKGROUND

Iliofemoral deep venous thrombosis (IFDVT) is associated with an incidence of post-thrombotic syndrome (PTS) of up to 50%. PTS is associated with high morbidity, impaired quality of life and a significant economic burden. The aim of the current study was to assess the impact of a single session pharmacomechanical thrombectomy (PMT), dedicated venous stents and a risk mitigation protocol on the rate of PTS.

METHODS

Between 2015 and 2022, patients presenting with acute or subacute IFDVT treated with the same protocol of single session PMT, dedicated venous stents, and risk-mitigation measures were included. Procedural success rate, complications, stent patency and incidence of PTS were determined.

RESULTS

Of 60 patients (58 ± 19 years; 65% male), the procedural success rate was 93%, with 7% of patients experiencing complications but no long-term sequelae or mortality. Most (n = 52; 87%) patients were stented, including 46% across the inguinal ligament. At 3 months post-procedure, primary, assisted primary and secondary stent patency rates were 89%, 93% and 98%, respectively, with no loss of patency or re-interventions after that. At latest follow-up of a median 48 months (n = 32), stent patency rate was 97%, with only three patients (9%) experiencing symptoms of PTS.

CONCLUSION

Single session PMT, dedicated venous stents and a risk-mitigation protocol results in high success rate, excellent long-term stent patency and low incidence of PTS without compromising safety. These results support early intervention for iliofemoral DVT.

Cost Effectiveness of Early Endovenous Thrombus Removal for Acute Iliofemoral Deep Vein Thrombosis in the United Kingdom

OBJECTIVE

Early clot removal using endovascular intervention aims to reduce post-thrombotic syndrome (PTS) following iliofemoral deep venous thrombosis (DVT). This may reduce long term morbidity but incurs a higher initial cost. This study examined the cost effectiveness of catheter directed thrombolysis (CDT) and pharmacochemical thrombectomy (PMT) compared with oral anticoagulation (OAC) alone for treatment of acute iliofemoral DVT in the United Kingdom.

METHODS

A combined decision tree (acute DVT complications) and Markov model (long term complications [PTS]) was used for decision analytic modelling with five states: no PTS, mild PTS, moderate PTS, severe PTS, and dead. All patients started with acute DVT. Patients who survived acute complications transitioned into the Markov model. Cycle time was six months. A healthcare payer perspective and lifetime horizon was used, adjusting for excess mortality due to history of thrombosis. Data for probabilities, transition probabilities, mortality, and utilities were obtained from the published literature. Cost data were obtained from UK NHS tariffs and published literature. Outcomes were mean lifetime cost, quality adjusted life years (QALYs), and cost effectiveness.

RESULTS

Over a patient's lifetime, OAC was more costly (£37 206) than CDT (£32 043) and PMT (£36 288). Mean lifetime QALYs for OAC (12.9) were lower than CDT (13.5) and PMT (13.3). Therefore, in the incremental cost effectiveness analysis, both CDT and PMT were dominant: CDT was less costly (-£5 163) and more effective (+0.6 QALYs) than OAC, and PMT was also less costly (-£917) and more effective (+0.3 QALYs) than OAC. Results were robust to univariable sensitivity analyses, but probabilistic sensitivity analyses suggested considerable parameter uncertainty.

CONCLUSION

Early interventional treatment of iliofemoral DVT is cost effective in the UK. Future clinical and epidemiological studies are needed to characterise parameter uncertainty. Further analysis of modern practice, alternative treatments, and optimised care models is warranted.

Venous Thromboembolism: Review of Clinical Challenges, Biology, Assessment, Treatment, and Modeling

Venous thromboembolism (VTE) is a massive clinical challenge, annually affecting millions of patients globally. VTE is a particularly consequential pathology, as incidence is correlated with extremely common risk factors, and a large cohort of patients experience recurrent VTE after initial intervention. Altered hemodynamics, hypercoagulability, and damaged vascular tissue cause deep-vein thrombosis and pulmonary embolism, the two permutations of VTE. Venous valves have been identified as likely locations for initial blood clot formation, but the exact pathway by which thrombosis occurs in this environment is not entirely clear. Several risk factors are known to increase the likelihood of VTE, particularly those that increase inflammation and coagulability, increase venous resistance, and damage the endothelial lining. While these risk factors are useful as predictive tools, VTE diagnosis prior to presentation of outward symptoms is difficult, chiefly due to challenges in successfully imaging deep-vein thrombi. Clinically, VTE can be managed by anticoagulants or mechanical intervention. Recently, direct oral anticoagulants and catheter-directed thrombolysis have emerged as leading tools in resolution of venous thrombosis. While a satisfactory VTE model has yet to be developed, recent strides have been made in advancing in silico models of venous hemodynamics, hemorheology, fluid-structure interaction, and clot growth. These models are often guided by imaging-informed boundary conditions or inspired by benchtop animal models. These gaps in knowledge are critical targets to address necessary improvements in prediction and diagnosis, clinical management, and VTE experimental and computational models.

Nanomicrosphere sustained-release urokinase systems with antioxidant properties for deep vein thrombosis therapy

Deep vein thrombosis (DVT) is a venous return disorder caused by abnormal clotting of blood in deep veins. After thrombosis, most of the thrombus will spread to the deep vein trunk throughout the limb. If DVT is not treated in time, most of them will develop into thrombosis sequelae and even threaten life. Intravenous thrombolytic drugs are the most promising strategy for treating DVT, but current drugs used for thrombolysis suffer from short half-lives and narrow therapeutic indexes. To effectively manage DVT, it is necessary to develop a novel multifunctional drug-loading system to effectively prolong the treatment time and improve the therapeutic efficacy. In this study, a urokinase-loaded protocatechuic aldehyde-modified chitosan microsphere drug-loading platform was constructed for the treatment of DVT. This microsphere adsorbed urokinase well through electrostatic interaction, and the introduction of bovine serum albumin conferred stability to the microspheres. Therefore, the microsphere drug delivery system could achieve slow drug release to effectively dissolve blood fibrin. In addition, chitosan grafted with protocatechuic aldehyde imparted excellent antioxidant activity to the system to reduce free radicals in the blood vessels. Effective management of oxidative stress could avoid abnormal platelet activation and new thrombus formation. The experimental results showed that this microsphere had good biocompatibility, anti-inflammatory properties, and considerable thrombolytic activity. In conclusion, this study provided a new direction and developed a novel multi-functional nano microsphere drug delivery platform for the treatment of DVT.

In Vivo Porcine Model of Acute Iliocaval Deep Vein Thrombosis

CLINICAL IMPACT

The study establishes a rapid, technically straightforward, and reproducible porcine large animal model for acute iliocaval deep vein thrombosis (DVT). The procedure can be performed with basic endovascular skillsets. With its procedural efficiency and consistency, the platform is promising for comparative in vivo testing of venous thrombectomy devices in a living host, and for future verification and validation studies to determine efficacy of novel thrombectomy devices relative to predicates.

Catheter-Directed Thrombolysis Protocols for Deep Venous Thrombosis of the Lower Extremities-A Systematic Review and Meta-analysis

OBJECTIVE

 To summarize characteristics, complications, and success rates of different catheter-directed thrombolysis (CDT) protocols for the treatment of lower extremity deep venous thrombosis (LE-DVT).

METHODS

 A systematic review using electronic databases (MEDLINE, Scopus, and Web of Science) was performed to identify randomized controlled trials and observational studies related to LE-DVT treated with CDT. A random-effects model meta-analysis was performed to obtain the pooled proportions of early complications, postthrombotic syndrome (PTS), and venous patency.

RESULTS

 Forty-six studies met the inclusion criteria reporting 49 protocols (n = 3,028 participants). In studies that addressed the thrombus location (n = 37), LE-DVT had iliofemoral involvement in 90 ± 23% of the cases. Only four series described CDT as the sole intervention for LE-DVT, while 47% received additional thrombectomy (manual, surgical, aspiration, or pharmacomechanical), and 89% used stenting.Definition of venogram success was highly variable, being the Venous Registry Index the most used method (n = 19). Among those, the minimal thrombolysis rate (<50% lysed thrombus) was 0 to 53%, partial thrombolysis (50-90% lysis) was 10 to 71%, and complete thrombolysis (90-100%) was 0 to 88%. Pooled outcomes were 8.7% (95% confidence interval [CI]: 6.6-10.7) for minor bleeding, 1.2% (95% CI: 0.8-1.7%) for major bleeding, 1.1% (95% CI: 0.6-1.6) for pulmonary embolism, and 0.6% (95% CI: 0.3-0.9) for death. Pooled incidences of PTS and of venous patency at up to 1 year of follow-up were 17.6% (95% CI: 11.8-23.4) and 77.5% (95% CI: 68.1-86.9), respectively.

CONCLUSION

 Assessment of the evidence is hampered by the heterogeneity of protocols, which may be reflected in the variation of PTS rates. Despite this, CDT is a low-risk treatment for LE-DVT.

May-Thurner syndrome: A case of extensive unprovoked left lower extremity deep vein thrombosis (DVT)

May-Thurner syndrome (MTS) also known as iliac vein compression syndrome, is a congenital anatomical variant, that results from the extrinsic compression of the left common iliac vein by the right iliac artery with resultant formation of left venous thrombosis. We report a case of a young man with recurrent unprovoked left lower extremity DVT in the setting of May Thurner syndrome who required endovascular intervention and was discharged on oral anticoagulation.

The background and role of catheter-directed thrombolysis evolving procedures for acute iliofemoral deep venous thrombosis

Minimal invasive treatment such as early endovenous thrombus removal for iliofemoral deep venous thrombosis (DVT) emerged in the end of last century. The principle is catheter-directed thrombolysis (CDT) using either plasminogen activating agents alone, as ultrasound-assisted CDT, or in combination with mechanical devices as pharmaco-mechanical CDT. The interest for this treatment modality is the high rate of post-thrombotic syndrome (PTS) with anticoagulation (AC) alone, especially after iliofemoral DVT. Recently published randomized controlled trials (RCTs) comparing early thrombus removal with AC alone, as well as non-randomized studies, have demonstrated favorable rates, or at least a decrease of moderate and severe PTS, in favor of these procedures. This article will summarize the background and evolution of the procedures in the last three decades and discuss fundamental criteria for inclusion and exclusion, focusing on the procedures regarding thrombus age and location, technical issues, complications and results including different outcome measures for PTS, for which iliac DVT involvement is a massive risk factor to be prevented.

Randomized controlled trials of interventions for acute iliofemoral deep venous thrombosis

Venous thromboembolism (VTE), notably deep venous thrombosis (DVT), represents a significant cardiovascular disease with high morbidity from post-thrombotic syndrome (PTS). Recent advancements in early thrombus removal technologies have prompted randomized controlled trials (RCT) to assess their efficacy and safety, particularly for iliofemoral DVT (IF-DVT), which carries the greatest risk of developing PTS. This narrative review summarizes these trials and introduces upcoming innovations to evaluate acute intervention for IF-DVT. Specific technologies discussed include catheter-directed thrombolysis, pharmacomechanical catheter-directed thrombolysis, ultrasound-accelerated catheter-directed thrombolysis, and non-lytic mechanical thrombectomy. This review underscores the importance of patient selection, with those presenting with extensive, symptomatic IF-DVT likely to benefit most.

Plasma Fibrinogen Change as a Predictor of Major Bleeding During Catheter-Directed Thrombolysis

BACKGROUND

Our primary objective was to determine the relationship between plasma fibrinogen levels (PFLs) and major bleeding complications during catheter-directed thrombolysis, including final, nadir, and change over time. Furthermore, we sought to evaluate additional predictors of bleeding outcomes, including duration of lysis and total dose of tissue plasminogen activator received.

METHODS

In this multicenter retrospective cohort study, we reviewed all patients undergoing catheter-directed thrombolysis between January 2016 and August 2021. Patients undergoing thrombolysis for management of peripheral arterial or venous thromboses, as well as for submassive pulmonary embolism, were included. We examined the relationships between PFLs during catheter-directed lysis and the incidence of major bleeding-that is significant hemorrhage requiring transfusion, intracranial hemorrhage, or hemorrhage requiring adjunctive procedures. We also examined the duration of lysis and total lytic agent dose received to assess for association with major bleeding.

RESULTS

A total of 438 patients underwent catheter-directed lysis from January 1, 2016 through August 21, 2021, with a major bleeding rate of 16%. Patients who experienced major bleeding were more likely to be older (P = 0.022), experience in-stent thrombosis (P = 0.041), or have thrombosis in a lower extremity vessel (P = 0.011). There was no association between the incidence of major bleeding and a nadir PFL of <150 mg/dL (P = 0.194). Those who experienced major bleeding complications had a significantly greater decrease in PFL from baseline to nadir. This was true for both absolute (P = 0.029) and relative (P = 0.034) PFL decrease. Only percent decrease remained a significant predictor when adjusting for age, thrombosis type, and thrombosis location (P = 0.041). The PFL changes that were the best predictors of major bleeding complications were an absolute decrease of 146 mg/dL, or a relative decrease of 47%, giving a sensitivity and specificity of 71% and 48%, respectively. If neither were true, the negative predictive value for major bleeding was 89% regardless of absolute PFL.

CONCLUSIONS

In this large, multicenter cohort, there does not appear to be an association between absolute PFL and major bleeding during catheter-directed lysis. Specifically, the typical absolute threshold of < 150 mg/dL was not an independent predictor of major bleeding. There was an association between percent-change in plasma fibrinogen and major bleeding, which aligns with the underlying physiologic mechanism of fibrinogen degradation coagulopathy. Applying a so-called "50-150 Rule" to catheter-directed lysis may decrease bleeding complications. That is, continued lysis should be re-evaluated if PFL drops by ≥150 mg/dL or by ≥50% from baseline regardless of absolute PFL.

Comparison of anticoagulation vs mechanical thrombectomy for the treatment of iliofemoral deep vein thrombosis

OBJECTIVE

To compare the comparative effects of treatment with contemporary mechanical thrombectomy (MT) or anticoagulation (AC) on Villalta scores and post-thrombotic syndrome (PTS) incidence through 12 months in iliofemoral deep vein thrombosis (DVT).

METHODS

Patients with DVT in the Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) randomized trial and the ClotTriever Outcomes (CLOUT) registry were included in this analysis. Both studies evaluated the effects of thrombus removal on the incidence of PTS. Patients with bilateral DVT, isolated femoral-popliteal DVT, symptom duration of >4 weeks, or incomplete case data for matching covariates were excluded. Propensity scores were used to match patients 1:1 who received AC (from ATTRACT) with those treated with mechanical thrombectomy (from CLOUT) using nearest neighbor matching on nine baseline covariates, including age, body mass index, leg treated, provoked DVT, prior venous thromboembolism, race, sex, Villalta score, and symptom duration. Clinical outcomes, including Villalta score and PTS, were assessed. Logistic regression was used to estimate the likelihood of developing PTS at 12 months.

RESULTS

A total of 164 pairs were matched, with no significant differences in baseline characteristics after matching. There were fewer patients with any PTS at 6 months (19% vs 46%; P < .001) and 12 months (17% vs 38%; P < .001) in the MT treatment group. Modeling revealed that, after adjusting for baseline Villalta scores, patients treated with AC had significantly higher odds of developing any PTS (odds ratio, 3.1; 95% confidence interval, 1.5-6.2; P = .002) or moderate to severe PTS (odds ratio, 3.1; 95% confidence interval, 1.1-8.4; P = .027) at 12 months compared with those treated with MT. Mean Villalta scores were lower through 12 months among those receiving MT vs AC (3.3 vs 6.3 at 30 days, 2.5 vs 5.5 at 6 months, and 2.6 vs 4.9 at 12 months; P < .001 for all).

CONCLUSIONS

MT treatment of iliofemoral DVT was associated with significantly lower Villalta scores and a lower incidence of PTS through 12 months compared with treatment using AC. Results from currently enrolling clinical trials will further clarify the role of these therapies in the prevention of PTS after an acute DVT event.

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.

Comparative outcomes of catheter-directed thrombolysis versus AngioJet pharmacomechanical catheter-directed thrombolysis for treatment of acute iliofemoral deep vein thrombosis

OBJECTIVE

The objective of this study was to compare the outcomes of pharmacomechanical thrombolysis and thrombectomy (PCDT) plus catheter-directed thrombolysis (CDT) vs CDT alone for the treatment of acute iliofemoral deep vein thrombosis (DVT) and summarize the clinical experience, safety outcomes, and short- and long-term efficacy.

METHODS

We performed a 4-year retrospective, case-control study. A total of 95 consecutive patients with acute symptomatic iliofemoral deep vein thrombosis (DVT) with a symptom duration of ≤7 days involving the iliac and/or common femoral veins underwent endovascular interventions. The patients were divided into two groups according to their clinical indications: PCDT plus CDT vs CDT alone. Statistical analyses were used to compare the clinical characteristics and outcomes between the two groups. Additionally, the patients were followed up for 3 to 36 months after treatment, and the proportions of post-thrombotic syndrome (PTS) and moderate to severe PTS were analyzed using the Kaplan-Meier survival method.

RESULTS

A total of 95 consecutive patients were analyzed in this retrospective study, of whom, 51 underwent CDT alone and 44 underwent PCDT plus CDT. Between the two groups, in terms of immediate-term efficacy and safety, significant differences were found in the catheter retention time (60.64 ± 12.04 hours vs 19.42 ± 4.04 hours; P < .001), dosages of urokinase required (5.82 ± 0.81 million units vs 1.80 ± 0.64 million units; P < .001), the detumescence rate at 24 hours postoperatively (48.46% ± 8.62% vs 76.79% ± 7.98%; P = .026), the descent velocity of D-dimer per day (2266.28 ± 1358.26 μg/L/D vs 3842.34 ± 2048.02 μg/L/D; P = .018), total hospitalization stay (6.2 ± 1.40 days vs 3.8 ± 0.70 days; P = .024), number of postoperative angiograms (2.4 ± 0.80 vs 1.2 ± 0.30; P = .042), and grade III venous patency (>95% lysis: 54.5% vs 68.6%; P = .047). Furthermore, during the follow-up period, significant differences were found in the incidence of PTS (Villalta scale ≥5 or a venous ulcer: 47.0% vs 27.7%; P = .037), and the incidence proportion of moderate to severe PTS at 12 months (15.7% vs 4.5%; P = .024) and 24 months (35.3% vs 11.4%; P = .016).

CONCLUSIONS

Compared with CDT alone, in the iliofemoral DVT subgroup with a symptom duration of ≤7 days, PCDT plus CDT could significantly relieve early leg symptoms, shorten the hospitalization stay, reduce bleeding complications, promote long-term venous patency, and decrease the occurrence of PTS and the incidence proportion of moderate to severe PTS. Thus, the short- and long-term outcomes both support the superiority of PCDT plus CDT vs CDT in this subgroup.

Association of vena cava filters and catheter-directed thrombolysis for deep vein thrombosis with hospital readmissions

BACKGROUND

Acute deep vein thrombosis (DVT) affects >350,000 patients each year in the United States. Contemporary rehospitalization rates and predictors of acute DVT have not been well-characterized. We aimed to evaluate the all-cause 30-day readmission rate and its association with catheter-directed thrombolysis and vena cava filters in patients with proximal and caval DVT.

METHODS

Patients with an index hospitalization for acute proximal lower extremity DVT were evaluated for unplanned readmission rates at 30 days using the Nationwide Readmission Database from 2016 to 2017. We used Cox proportional hazard model to determine the predictors of 30-day readmissions and their association with inferior vena cava (IVC) filter and CDT use.

RESULTS

We identified 58,306 adult patients with an index hospitalization for acute proximal DVT. The unplanned 30-day rehospitalization rate was 14.7% (95% confidence interval [CI], 14.5-15.0%). There were 4995 patients (10.0%) who underwent CDT and 6085 (12.2%) who underwent IVC filter placement. In multivariable analysis, only CDT was associated with a lower hazard for rehospitalization (hazard ratio [HR], 0.77; 95% CI, 0.71-0.84; P < .001), whereas IVC filter placement (HR, 1.26; 95% CI, 1.19-1.34; P < .001), Charlson Comorbidity Index of >3 (HR, 1.47; 95% CI, 1.38-1.56; P < .001), malignancy (HR, 1.45; 95% CI, 1.34-1.57; P < .001), and length of stay >5 days (HR, 1.39; 95% CI, 1.33-1.46; P < .001), and acute kidney injury (HR, 1.18; 95% CI, 1.11-1.25; P < .001) were associated with higher readmission rates.

CONCLUSIONS

The 30-day unplanned rehospitalization rate continues to be high in patients with acute proximal DVT. CDT was associated with lower rehospitalization rates, whereas IVC filter placement was associated with increased rehospitalization rates.

Endovascular Thrombectomy for Acute Iliofemoral Deep Venous Thrombosis Through a Jugular Approach with a Rotational Device

PURPOSE

To report the effectiveness of pharmacomechanical catheter-directed thrombolysis (PCDT) in the management of acute iliofemoral deep venous thrombosis (DVT) via the jugular vein using a slow rotation and large-tip device (SRD) in a large cohort of patients.

MATERIAL AND METHODS

From 2011 to 2021, 277 patients (mean age 45 years, 59.2% women) were treated in 6 centres with PCDT for ilio-fémoral DVT. PCDT was performed via the jugular vein and consisted of one session of fragmentation-fibrinolysis, aspiration and, if needed, angioplasty with stenting. The aim of PCDT was to achieve complete clearance of the venous thrombosis and to restore iliofemoral patency. Residual thrombotic load was assessed by angiography, venous patency by duplex ultrasound and clinical effectiveness by the rate of post-thrombotic syndrome (Villalta score > 4).

RESULTS

All patients were treated via the jugular vein using an SRD, and all but one were treated with fibrinolysis. Angioplasty with stenting was performed in 84.1% of patients. After the procedure, the residual thrombotic load at the ilio-fémoral region was < 10% in 96.1% of patients. The rate of major complications was 1.8% (n = 5), the rate of minor complications was 4% (n = 11), and one patient died from pulmonary embolism (0.4%) At a median follow-up of 24 months, primary and secondary iliofemoral patency was 89.6% and 95.8%, respectively. The rate of PTS was 13.8% at 12 months.

CONCLUSION

PCDT via the jugular vein using an SRD is an efficient treatment for acute iliofemoral DVT and results in high long-term venous patency and low PTS rates. Level of evidence Level 4, Case series.

Case Report: It's not always about the veins; intervention of bilateral May-Thurner Syndrome secondary to iliac aneurysm

May-Thurner Syndrome (MTS) remains evasive because of the insidiousness and variable etiologies by which it can manifest. In this study, we examine a unique presentation of MTS resulting from compression of both common iliac veins by a right common iliac artery aneurysm that required complex endovascular venous and arterial intervention.

Single-center experience with the ClotTriever BOLD catheter for deep vein thrombosis percutaneous mechanical thrombectomy of the lower extremity

Background

The ClotTriever System is a percutaneous mechanical thrombectomy system used to treat deep vein thrombosis (DVT). The BOLD catheter is a newer compatible component with a modified coring element for which reported outcomes are limited. This retrospective study aims to assess the preliminary procedural safety and success data for patients treated with the BOLD catheter.

Methods

All consecutive patients with symptomatic lower extremity DVT who underwent thrombectomy with the BOLD catheter between 23 November 2021 and 26 June 2022 at a single center were included. Baseline and procedural characteristics were reported. The primary outcome, intraprocedural safety, was assessed by a chart review of recorded intraprocedural adverse events (AEs) or device malfunction. The secondary outcome, procedural success, was defined as ≥75% reduction in the total occlusion across treated venous segments. This was assessed by an interventionalist review of pre- and postprocedural venograms. Additional outcomes included length of postprocedural hospital stay and assessment of AEs at discharge and a 30-day follow-up visit.

Results

Eleven patient cases were reviewed. The median patient age was 65 years, the majority were women, and all were treated unilaterally. All procedures were completed in a single session without intraprocedural AEs or device malfunction. The median procedural blood loss was 50 ml. A review of pre- and postprocedural venograms showed that 35 venous segments were treated, including the femoral (n = 9), common femoral (n = 9), external iliac (n = 10), and common iliac (n = 7) veins. Procedural success was achieved in 10 patients (90.9%), and the median reduction rate in venous occlusion was 100%. The median length of postprocedural hospital stay was 1 day, and no AEs were noted at discharge (N = 11). One adverse event occurred among the eight patients who completed their follow-up visit. A patient with advanced-stage cancer and medication failure had a recurrent DVT 13 days postprocedure, which was not related to the device or procedure.

Conclusions

No safety concerns concerning the BOLD catheter were raised during the review of the cases included in this analysis, and the device was successful in reducing venous occlusion in patients with symptomatic proximal lower extremity DVT.

Mechanical thrombectomy of inferior vena cava filter-associated caval thrombosis using FlowTriever and ClotTriever systems

OBJECTIVE

Chronically indwelling inferior vena cava filters (IVCFs) can have multiple adverse sequelae, including IVCF-associated thrombosis. The Inari ClotTriever and FlowTriever mechanical and aspiration thrombectomy systems (Inari Medical) can be used for acute caval thrombosis associated with IVCFs if appropriate proximal IVCF protection is used intraprocedurally. The present study reports a single institution's outcomes after ClotTriever and FlowTriever thrombectomy of acute IVCF-associated iliocaval thrombus.

METHODS

A retrospective review was conducted of all patients who underwent ClotTriever or FlowTriever thrombectomy for IVCF-associated caval thrombosis. The patient demographics, clinical characteristics, and postprocedural outcomes of a 15-patient cohort were compiled and described.

RESULTS

A total of 15 patients were identified as presenting with acute IVCF-associated caval thrombosis and having undergone intervention with either the ClotTriever or FlowTriever system from 2019 to 2022. Of the 15 patients in the cohort, 3 (20%) had presented with a threatened extremity (phlegmasia cerulea dolens), and 12 had presented with severe, debilitating, but non-limb-threatening, lower extremity edema. The preprocedural clot burden was significant and involved the cava, iliac veins, and femoropopliteal veins in 7 of 15 patients (47%) in the cohort. The procedure was technically successful in 11 patients (73.33%). Resolution of acute symptoms was noted in 100% of the technically successful procedures. The 30-day mortality rate was 13% (2 of 15 patients). One intraprocedural death occurred from pulmonary embolism, and one patient died of malignancy complications. The surviving patients not lost to follow-up experienced stable or improving venous disease, with only one patient presenting with post-phlebitic syndrome.

CONCLUSIONS

Mechanical and aspiration thrombectomy of IVCF-associated thrombus with the FlowTriever and ClotTriever systems have good technical success and resulted in significant improvement in acute symptoms with adequate clot clearance. Proximal embolic protection maneuvers for pulmonary embolism prophylaxis and preexisting filter protection are required intraprocedurally.

Acute and chronic venous occlusion

This review article provides an overview of acute and chronic venous occlusion, a condition that can cause significant morbidity and mortality if not diagnosed and treated promptly. The article begins with an introduction to the anatomy of the venous system, followed by a discussion of the causes and clinical features of venous occlusion. The diagnostic tools available for the assessment of venous occlusion, including imaging modalities such as ultrasound, CT, and MRI, are then discussed, along with their respective advantages and limitations. The article also covers the treatment options for acute and chronic venous occlusion, including anticoagulant therapy and endovascular interventions. This review aims to provide radiologists with an updated understanding of the pathophysiology, diagnosis, and management of acute and chronic venous occlusion.

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.

Six-Month Outcomes of Mechanical Thrombectomy for Treating Deep Vein Thrombosis: Analysis from the 500-Patient CLOUT Registry

PURPOSE

Mechanical thrombectomy for the treatment of deep vein thrombosis (DVT) is being increasingly utilized to reduce symptoms and prevent postthrombotic syndrome (PTS), but more data on clinical outcomes are needed. Mechanical thrombectomy was studied in the ClotTriever Outcomes (CLOUT) registry with 6-month full analysis outcomes reported herein.

MATERIALS AND METHODS

The CLOUT registry is a prospective, all-comer study that enrolled 500 lower extremity DVT patients across 43 US sites treated with mechanical thrombectomy using the ClotTriever System. Core-lab assessed Marder scores and physician-assessed venous patency by duplex ultrasound, PTS assessment using Villalta score, venous symptom severity, pain, and quality of life scores through 6 months were analyzed. Adverse events were identified and independently adjudicated.

RESULTS

All-cause mortality at 30 days was 0.9%, and 8.6% of subjects experienced a serious adverse event (SAE) within the first 30 days, 1 of which (0.2%) was device related. SAE rethrombosis/residual thrombus incidence was 4.8% at 30 days and 8.0% at 6 months. Between baseline and 6 months, venous flow increased from 27.2% to 92.5% of limbs (P < 0.0001), and venous compressibility improved from 28.0% to 91.8% (P < 0.0001), while median Villalta scores improved from 9.0 at baseline to 1.0 at 6 months (P < 0.0001). Significant improvements in venous symptom severity, pain, and quality of life were also demonstrated. Outcomes from iliofemoral and isolated femoral-popliteal segments showed similar improvements.

CONCLUSION

Outcomes from the CLOUT study, a large prospective registry for DVT, indicate that mechanical thrombectomy is safe and demonstrates significant improvement in symptoms and health status through 6 months. Level of Evidence 3: Non-randomized controlled cohort/follow-up study.

TILE pilot trial study protocol: Tinzaparin Lead-in to Prevent the Post-Thrombotic syndrome study protocol

INTRODUCTION

The post-thrombotic syndrome (PTS) is a form of chronic venous insufficiency due to a prior ipsilateral deep venous thrombosis (DVT). This is a frequent complication that develops in 20%-50% of patients after a proximal DVT and is associated with significant healthcare, economic and societal consequences. In the absence of effective and well-tolerated treatment options for established PTS, effective preventative measures are needed. Anticoagulation itself reduces the risk of PTS, and low-molecular-weight heparin may reduce this further through anti-inflammatory properties targeting the initial acute inflammatory phase of DVT.

METHODS AND ANALYSIS

The Tinzaparin Lead-In to Prevent the Post-Thrombotic syndrome pilot trial is an investigator-initiated, multicentre, open-label assessor-blinded trial that will randomise patients with first acute symptomatic common femoral or iliac DVT to receive either a 3-week lead-in course of tinzaparin, followed by rivaroxaban (experimental arm) or rivaroxaban alone (control arm). Its primary objectives are to assess: (1) proportion of PTS at 6 months using the Villalta scale and (2) study feasibility, which consists of (a) the proportion of screened patients eligible for the study, (2) the proportion of eligible patients recruited and (c) the proportion of recruited patients adherent to treatment (defined as at least 80% of drug taken). This study will determine the feasibility of a subsequent larger definitive trial. Secondary outcomes include change of quality of life scores, PTS severity, global improvement, patient satisfaction, bleeding, recurrent venous thromboembolism, leg pain, death and lost to follow-up. Target recruitment will be a total of 60 participants, recruited at 5-6 centres.

ETHICS AND DISSEMINATION

Primary ethics approval was received from the Sunnybrook Health Sciences Center Research Ethics Board (approval ID 3315). Results of the study will be disseminated via peer-reviewed presentation at scientific conferences and open access publication.

TRIAL REGISTRATION NUMBER

NCT04794569.

New Therapeutic Targets for the Prevention and Treatment of Venous Thromboembolism With a Focus on Factor XI Inhibitors

FXI (factor XI) and FXII (factor XII) have emerged as targets for new anticoagulants that have the potential to be both more efficacious and safer than the currently available direct oral anticoagulants for the prevention and treatment of venous thromboembolism. In this review, we discuss the role of FXI and FXII in the pathogenesis of venous thromboembolism, explain why FXI is a better target, and explain why FXI inhibitors have potential advantages over currently available anticoagulants. Finally, we describe the FXI inhibitors under development and discuss their potential to address unmet needs in venous thromboembolism management.

Assessing outcomes after thrombectomy with or without iliac vein stenting for young provoked DVT patients with iliac vein stenosis

BACKGROUND

This study aimed to assess the outcomes of thrombectomy with/without iliac vein stenting for young and transiently provoked DVT patients with iliac vein stenosis.

METHODS

This is a retrospective analysis of a prospectively collected multicenter database. Acute, transiently provoked DVT patients between 18 and 45 years old with iliac vein stenosis were included. All patients underwent thrombectomy. Outcomes including the Villalta score, the VEINES-QOL score, and adverse events were evaluated.

RESULTS

The data of 522 patients were collected of whom 75 were included, 58 underwent thrombectomy alone (nonstenting group) and 17 underwent thrombectomy and stenting (stenting group). Within 6 months, the Villalta score of patients in stenting group is lower than that of patients in nonstenting group (6 mo: 0.73 ± 0.77 vs. 1.41 ± 0.56, p = .0004), and the VEINES-QOL score of stenting group is higher than that of nonstenting group (6 mo: 89.00 ± 2.94 vs. 87.47 ± 3.72, p = .2141). At the following follow-ups, the Villalta score (12 mo: 0.56 ± 0.49 vs. 0.60 ± 0.58, p = .8266) and VEINES-QOL score (12 mo: 88.36 ± 2.29 vs. 88.31 ± 3.36, p = .9604) between the two groups are similar.

CONCLUSION

The stenting group had better efficacy within 6 months after intervention, while there was no significant difference in the symptom, signs, and quality of life between two groups after 6 months within a 2-year follow-up.

TRIAL REGISTRATION

This study was registered in the Chinese Clinical Trial Registry (Registration Number: ChiCTR2200056073).

Comparison of Medical Treatment Efficiency With Shear Wave Elastography Values of Thrombus in Patients With Lower Extremity Deep Vein Thrombosis

ABSTRACT

In lower-extremity deep vein thrombosis (DVT), thrombus age is essential for successful treatment. The aim of our study was to compare the shear wave elastography (SWE) values measured before treatment and achieved lumen patency after treatment in lower-extremity DVT patients with total occlusion. Patients diagnosed with DVT in the acute-subacute stage (<4 week) with total thrombosis in lower extremity were included in this prospective study. Shear wave elastography measurements were performed where the thrombus was most prominent and homogeneous. To evaluate patient response to treatment, lumen patency (partial [>25%] or total recanalization) was examined using color Doppler imaging in the first and third months posttreatment. Shear wave elastography values with and without patency were compared using an independent t test. Among 75 patients in this study, at the first-month color Doppler imaging examination, the SWE values were 1.77 ± 0.49 (1.09-3.03) m/s in patients who achieved lumen patency (n = 42) and 2.21 ± 0.54 (1.24-3.36) m/s in those who did not show lumen patency (n = 33). The difference between the groups' mean elastography value was statistically significant ( P < 0.001). At the third-month examination, the SWE values were 1.76 ± 0.46 (1.09-3.03) m/s in patients with lumen patency (n = 55) and 2.52 ± 0.48 (1.74-3.36) in patients without lumen patency (n = 20). The difference between the 2 groups' mean elastography value was statistically significant ( P < 0.001). We concluded that it is more difficult to achieve lumen patency in veins occluded by thrombus with higher elasto values, and endovascular interventional procedures should be considered during the initial treatment of high SWE value thrombosis.

Long Term Follow Up, Causes for Re-intervention, and Consequences for Surveillance After Stenting for Proximal Deep Vein Obstruction

OBJECTIVE

Venous stenting is performed increasingly for acute deep vein thrombosis (DVT) and post-thrombotic syndrome (PTS) with good short term patency results, but long term data are scarce. The purpose of this study was to evaluate long term outcome of stenting for acute DVT and PTS and to study causes of re-intervention.

METHODS

All patients stented for acute DVT and PTS between May 2006 and November 2021 were included retrospectively in this single centre cohort study. Patency was studied by duplex ultrasound (DUS) or computed tomography. The primary endpoint was stent patency. Re-intervention free survival was calculated using Kaplan-Meier methods. Secondary endpoints were causes of re-intervention, using the Pouncey classification system (2022). Binary logistic regression was used to calculate odds ratios for predictors of re-intervention.

RESULTS

A total of 114 patients were included, with 129 limbs involved (acute DVT n = 53; 41%), PTS n = 76; 59%). Median follow up was 2.3 years (interquartile range [IQR] 2.3) for acute DVT and 5.2 years (IQR 7.1) for PTS. Primary patency, secondary patency, and permanent occlusion were 73.5%, 98.1%, and 1.9% for acute DVT, and 63.2%, 92.1%, and 7.9% for PTS limbs. Overall, 41 limbs underwent at least one re-intervention: 14 in the acute DVT group and 27 for PTS. Most re-interventions (82.9%) were performed within the first year after stenting. Missed inflow, insufficient flow, and thrombosis despite anticoagulation were the most common causes of re-intervention. The strongest predictor for re-intervention for PTS was inflow disease (odds ratio 3.57, 95% confidence interval 1.26 - 10.13, p= .017).

CONCLUSION

Long term patency of deep venous stenting is good. Re-interventions are typically performed in the first year and are potentially preventable by improving the procedure and patient selection. Since secondary patency rates are excellent, selected patients may be considered for discharge from long term surveillance.

Single-Session Percutaneous Mechanical Thrombectomy for Acute and Subacute Deep Vein Thrombosis: Clinical Outcomes and Predictive Factors of Recurrence

Objectives

To evaluate the efficacy and safety of single-session percutaneous mechanical thrombectomy (PMT) for deep vein thrombosis (DVT), to compare clinical outcomes and recurrences between acute and subacute DVT, and to identify factors predicting recurrence.

Materials and Methods

From January 2018 to March 2021, 100 consecutive patients (age: 64.64 ± 17.28 years; male, 42%) with symptomatic DVT who underwent single-session PMT were enrolled for this study. These patients were divided into an acute DVT group (< 14 days, n = 75) and a subacute DVT group (15-28 days, n = 25).

Results

A large-bore aspiration thrombectomy was used in 80 (80%) cases, Angiojet (Boston Scientific, Marlborough, MA, USA) device in one (1%) case, and a combination of both techniques in 19 (19%) cases. The anatomic success rate was 97% and the clinical success rate was 95%. There were no major complications. Clinical outcomes were not different between the two groups. The recurrence-free survival rate in the acute DVT group was significantly (p = 0.015) better than that in the subacute DVT group. The anatomic success (HR, 52.3; 95% CI, 3.82-715.21; p = 0.003) and symptom duration (HR, 17.58; 95% CI, 1.89-163.34; p = 0.012) were predictive factors associated with recurrence.

Conclusions

Single-session PMT is safe and effective for immediate symptom relief in acute and subacute DVT patients. However, recurrence occurred more frequently in patients with subacute DVT than in those with acute DVT. Anatomic success of the procedure and duration of symptoms were independent predictors of DVT recurrence.

Catheter-directed thrombolysis versus systemic anticoagulation in the treatment of symptomatic splanchnic venous thrombosis secondary to acute pancreatitis: a retrospective cohort study

BACKGROUND

Catheter-directed thrombolysis (CDT) has been an important therapy and seems effective in patients with splanchnic venous thrombosis (SVT) secondary to some diseases, but this intervention hasn't been formally evaluated in the setting of acute pancreatitis (AP).

METHODS

This was a retrospective study enrolled patients between January 2013 and December 2018. AP patients who developed SVT-induced symptoms, including intractable ascites and/or enteral nutrition intolerance, were included. Demographics, SVT associated parameters, clinical features and outcomes, long-term quality of life evaluated by using SF-36 questionnaire were compared between CDT group and systemic anticoagulation (SAC) group.

RESULTS

6 patients underwent CDT and 17 received SAC. Patients in CDT group had a higher recanalization rate (100% versus 35.3%; p = 0.014) and shorter time to symptoms resolution (median 8 days versus. 31.5 days, p = 0.004). Mortality and length of hospital stay were comparable between two groups. The association analysis indicated that CDT use exerted a significantly beneficial effect on recanalization rate (risk ratio, 2.833; 95% CI, 1.489 to 5.393; p = 0.002) and time to symptoms resolution (mean difference, -33.333; 95% CI, -64.612 to -2.055; p = 0.038). No SVT-related symptoms recurrence was recorded in survivors at six-month follow-up. There was no statistical difference in either item of SF-36 questionnaire between two groups.

CONCLUSIONS

Compared with SAC, CDT may facilitate vascular recanalization and shorten symptom resolution for symptomatic SVT.

Effectiveness and safety of catheter-directed thrombolysis in conjunction with percutaneous mechanical thrombectomy for acute iliofemoral deep vein thrombosis: A meta-analysis

BACKGROUND

Patients with severe acute low iliofemoral deep vein thrombosis (DVT), such as phlegmasia cerulea dolens, benefit from catheter-directed thrombolysis (CDT). This meta-analysis investigated the effectiveness and safety of adjuvant percutaneous mechanical thrombectomy (PMT) during CDT compared with CDT alone in the treatment of acute iliofemoral DVT.

METHODS

A meta-analysis was performed in accordance with the PRISMA guidelines. Medline, Embase, the Cochrane Library, China National Knowledge Internet, and Wanfang data were searched for studies on the management of acute iliofemoral DVT by means of CDT or CDT with adjuvant PMT. Randomized, controlled trials and nonrandomized studies were included. The primary outcomes were venous patency rate, major bleeding complications, and post-thrombotic syndrome occurrence within 2 years of the procedure. The secondary outcomes were thrombolytic time and volume, as well as the rates of thigh detumescence and iliac vein stenting.

RESULTS

The meta-analysis included 20 eligible studies with a total of 1686 patients. The rates of venous patency (mean difference, 10.11; 95% confidence interval [CI], 5.59-14.62) and thigh detumescence (mean difference, 3.64; 95% CI, 1.10-6.18) of the adjuvant PMT group were higher than those of the CDT alone group. Compared with CDT alone, the adjuvant PMT group experienced fewer incidences of major bleeding complications (odds ratio, 0.45; 95% CI, 0.26-0.77) and occurrences of post-thrombotic syndrome within 2 years of the procedure (odds ratio, 0.55; 95% CI, 0.33-0.92). Furthermore, the duration of thrombolytic therapy was shorter, and the total dose of administered thrombolytics was lower with adjuvant PMT.

CONCLUSIONS

Adjuvant PMT during CDT is associated with improved clinical outcomes and a lower incidence of major bleeding complications. The studies investigated were, however, single-center cohort studies, and future randomized controlled trials are needed to substantiate these findings.

Delphi Consensus on Reporting Standards in Clinical Studies for Endovascular Treatment of Acute Iliofemoral Venous Thrombosis and Chronic Iliofemoral Venous Obstruction

Acute iliofemoral deep vein thrombosis and chronic iliofemoral venous obstruction cause substantial patient harm and are increasingly managed with endovascular venous interventions, including percutaneous mechanical thrombectomy and stent placement. However, studies of these treatment elements have not been designed and reported with sufficient rigor to support confident conclusions about their clinical utility. In this project, the Trustworthy consensus-based statement approach was utilized to develop, via a structured process, consensus-based statements to guide future investigators of venous interventions. Thirty statements were drafted to encompass major topics relevant to venous study description and design, safety outcome assessment, efficacy outcome assessment, and topics specific to evaluating percutaneous venous thrombectomy and stent placement. Using modified Delphi techniques for consensus achievement, a panel of physician experts in vascular disease voted on the statements and succeeded in reaching the predefined threshold of >80% consensus (agreement or strong agreement) on all 30 statements. It is hoped that the guidance from these statements will improve standardization, objectivity, and patient-centered relevance in the reporting of clinical outcomes of endovascular interventions for acute iliofemoral deep venous thrombosis and chronic iliofemoral venous obstruction in clinical studies and thereby enhance venous patient care.