Catheter-directed thrombolysis of deep vein thrombosis: literature review and practice considerations

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.

Single-procedure 8Fr rheolytic pharmacomechanical thrombectomy for treatment of acute iliofemoral deep venous thrombosis

PURPOSE

We hypothesize that single-procedure venous-specific rheolytic thrombectomy for treatment of acute iliofemoral deep venous thrombosis (DVT) will result in improved clinical symptoms as measured by the venous clinical severity score (VCSS), as well as durable venous patency, with decreased hemorrhagic risks and costs associated with conventional catheter-directed therapy and prolonged lytic exposure.

MATERIALS AND METHODS

Thirty-three consecutive patients with symptomatic, unilateral, iliofemoral DVT who were treated with single-procedure therapy using the 8Fr rheolytic thrombectomy catheter were retrospectively analyzed from 2012-2021. Abstracted data included technical success (> 95% clearance of acute thrombus), adverse events (AEs), and clinical and imaging outcomes at 1-month and 1-year.

RESULTS

Technical success was achieved in all 33 patients. Mean pre-procedure VCSS was 7.5 with mean edema and pain sub-scores of 2.6 and 1.8, respectively. Post-procedural total mean VCSS at one month was significantly improved (mean post-procedure VCSS = 0.3, mean reduction of 7.2, P < 0.01). Clinical improvement was sustained at 1-year (mean total VCSS = 0.2, P < 0.01). Primary patency was achieved in all patients at 1-month and 30 (91%) patients at 1-year. Among the 3 patients in which primary patency was not achieved at 1-year, primary-assisted patency was achieved in 2 patients. Secondary patency was achieved in the remaining patient at 1-year. No hemorrhagic AEs occurred in this study.

CONCLUSION

This study suggests that single-procedure venous-specific rheolytic thrombectomy for treatment of acute iliofemoral DVT is safe and effective, resulting in durable clinical and radiographic results at one year, while also limiting hemorrhagic risks, mitigating costs of admission, and expediting patient discharge.

Case of Circulating Tumor Cells Discovered in Extensive Deep Venous Thrombosis in a Patient with Known Urothelial Carcinoma

Background

Currently, minimal data are available to explore the composition of venous thromboembolism in patients with cancer. This case report discusses a presentation of venous thromboembolism in a patient with high-grade urothelial carcinoma and highlights the pathology findings in thrombi. Case Presentation. A 55-year-old female who was diagnosed with high-grade urothelial carcinoma with multiple metastases developed an extensive deep vein thrombosis in her left lower extremity. Endovascular revascularization was indicated due to left lower extremity pain and swelling not responsive to anticoagulation. A mechanical thrombectomy was performed, and samples were sent for pathology. Pathologic examination discovered minute fragments of metastatic carcinoma, admixed with laminated blood clots (thrombus). The morphology of metastatic carcinoma and the immunostain profile were compatible with metastatic carcinoma of bladder origin.

Conclusion

Cancer is a well-known risk factor for developing VTEs, and it is estimated that approximately 4-20% of cancer patients will experience VTE at some stage, the rate being the highest in the initial period following diagnosis. Annually, 0.5% of cancer patients will experience thrombosis compared with a 0.1% incidence rate in the general population (Elyamany et al., 2014). Despite knowing the increased incidence of VTEs in cancer patients, there are few studies to date that analyze the composition of thrombi in patients with cancer.

Central Venous Catheter as a Novel Approach to Postoperative Thrombolysis in Patients with Acute Iliofemoral Deep Venous Thrombosis

BACKGROUND AND AIMS

Percutaneous mechanical thrombectomy (PMT) along with postoperative thrombolysis (POT) has been the standard treatment for acute iliofemoral deep venous thrombosis (IFDVT). However, commonly used catheter directed thrombolysis (CDT) approaches for POT carry certain disadvantages, including the need for a sheath, inferior comfortability, and catheter-related complications. Therefore, we propose a new simplified method of POT using a central venous catheter (CVC).

METHODS

The retrospective study analyzed patients with IFDVT who underwent POT using CVC from January 2020 to August 2021. The treatment modalities included filter placement, thrombus removal, iliac vein obstruction release, postoperative CVC thrombolysis, filter retrieval, and adequate full course anticoagulation.

RESULTS

A total of 39 patients were included in this retrospective study. All patients underwent PMT surgery with a procedure success rate of 100%. In the post-PMT CVC thrombolysis, the puncture sites were located in the below-knee vein, including 58.97% in the peroneal vein. The mean duration of CVC-directed thrombolysis was 3.69 ± 1.08 days, and the total urokinase dose was 2.27 ± 0.71 MIU. A total of 37 patients (94.87%) had successful thrombolysis with a length of hospital stay of 5.82 ± 2.21 days. During CVC-directed thrombolysis, only four minor bleeding complications occurred, two of which were indwelling catheter-related. During the 12-month follow-up period, the patency rate and post-thrombotic syndrome incidences were 97.44% and 2.56%, respectively.

CONCLUSION

Thrombolysis through a CVC is a feasible, safe, and effective POT method, and could be an alternative to the conventional CDT approach for patients with IFDVT.

Vortex-ultrasound for microbubble-mediated thrombolysis of retracted clots

Endovascular sonothrombolysis has gained significant attention due to its benefits, including direct targeting of the thrombus with sonication and reduced side effects. However, the small aperture of endovascular transducers restricts the improvement of their potential clinical efficiency due to inefficient acoustic radiation. Hence, in an earlier study, we used vortex ultrasound with an endovascular ultrasound transducer to induce shear stress and enhance the clot lysis. In this study, the vortex acoustic transduction mechanism was investigated using numerical simulations and hydrophone tests. Following this characterization, we demonstrated the performance of the vortex ultrasound transducer in thrombolysis of retracted clots in in vitro tests. The test results indicated that the maximum lysis rates were 79.0% and 32.2% with the vortex ultrasound for unretracted and retracted clots, respectively. The vortex ultrasound enhanced the efficiency of the thrombolysis by approximately 49%, both for retracted and unretracted clots, compared with the typical non-vortex ultrasound technique. Therefore, the use of endovascular vortex ultrasound holds promise as a potential clinical option for the thrombolysis of retracted clots.

Miniaturized Stacked Transducer for Intravascular Sonothrombolysis With Internal-Illumination Photoacoustic Imaging Guidance and Clot Characterization

Thromboembolism in blood vessels can lead to stroke or heart attack and even sudden death unless brought under control. Sonothrombolysis enhanced by ultrasound contrast agents has shown promising outcome on effective treatment of thromboembolism. Intravascular sonothrombolysis was also reported recently with a potential for effective and safe treatment of deep thrombosis. Despite the promising treatment results, the treatment efficiency for clinical application may not be optimized due to the lack of imaging guidance and clot characterization during the thrombolysis procedure. In this paper, a miniaturized transducer was designed to have an 8-layer PZT-5A stacked with an aperture size of 1.4 × 1.4 mm2 and assembled in a customized two-lumen 10-Fr catheter for intravascular sonothrombolysis. The treatment process was monitored with internal-illumination photoacoustic tomography (II-PAT), a hybrid imaging modality that combines the rich contrast of optical absorption and the deep penetration of ultrasound detection. With intravascular light delivery using a thin optical fiber integrated with the intravascular catheter, II-PAT overcomes the penetration depth limited by strong optical attenuation of tissue. In-vitro PAT-guided sonothrombolysis experiments were carried out with synthetic blood clots embedded in tissue phantom. Clot position, shape, stiffness, and oxygenation level can be estimated by II-PAT at clinically relevant depth of ten centimeters. Our findings have demonstrated the feasibility of the proposed PAT-guided intravascular sonothrombolysis with real-time feedback during the treatment process.

Meta-analysis of lytic catheter-based intervention for acute proximal deep vein thrombosis in the reduction of post-thrombotic syndrome

OBJECTIVE

Post-thrombotic syndrome (PTS) is a common complication of deep vein thrombosis (DVT) that can result in significant morbidity for the patient with detrimental impact on their quality of life. Evidence supporting lytic catheter-based interventions (LCBI) undertaken for early thrombus reduction in acute proximal DVT for the prevention of PTS is conflicting. Despite this, rates of LCBIs are increasing. To summaries the existing evidence and pool treatment effects, a meta-analysis of randomized controlled trials assessing the efficacy of LCBIs in proximal acute DVT for the prevention of PTS was undertaken.

METHODS

This meta-analysis was undertaken aligning with PRISMA guidelines following a protocol pre-registered on PROSPERO. Online searches of Medline and Embase databases, as well as the gray literature, were performed up to December 2022. Included articles were randomized controlled trials that studied the use of LCBIs with additional anticoagulation vs anticoagulation alone and had determined follow-up periods. Outcomes of interest were PTS development, moderate to severe PTS, major bleeding episodes, and quality-of-life measures. Subgroup analyses were performed for DVTs involving the iliac vein and/r common femoral vein. Meta-analysis was performed using a fixed effects model. Quality assessment was performed using the Cochrane Risk of Bias and GRADE assessment tools.

RESULTS

Three trials were included in the final meta-analysis, the Post-thrombotic Syndrome after Catheter-directed Thrombolysis for Deep Vein Thrombosis (CaVenT), Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT), and Ultrasound-accelerated Catheter-directed Thrombolysis Versus Anticoagulation for the Prevention of Post-thrombotic Syndrome (CAVA) trials, comprising 987 patients. Patients undergoing LCBIs had a reduced risk of PTS (relative risk [RR], 0.84; 95% confidence interval [CI], 0.74-0.95; P = .006) and a lower risk of developing moderate to severe PTS (RR, 0.75; 95% CI, 0.58-0.97; P = .03). LBCIs increased the risk of having a major bleed (RR, 2.03; 95% CI, 1.08-3.82; P = .03). In the iliofemoral DVT subgroup analysis, there was a trend toward decreasing the risk of developing PTS and moderate to severe PTS (P = .12 and P = .05, respectively). There was no significant difference in quality-of-life score (as measured by the Venous Insufficiency Epidemiological and Economic Study - Quality of Life/Symptoms) between the two groups (P = .51).

CONCLUSIONS

Pooling of current best evidence suggests that LCBIs in acute proximal DVT decreases the rate of PTS and moderate to severe PTS with a number needed to treat of 12 and 18, respectively. However, this is complicated by a significantly higher rate of major bleeding with a number needed to treat of 37. This evidence supports the use of LCBIs in selected patients, including those who are at low risk of major bleeding.

Catheter-directed thrombolysis compared with systemic thrombolysis and anticoagulation in patients with intermediate- or high-risk pulmonary embolism: systematic review and network meta-analysis

BACKGROUND

Therapeutic options for intermediate- or high-risk pulmonary embolism (PE) include anticoagulation, systemic thrombolysis and catheter-directed thrombolysis (CDT); however, the role of CDT remains controversial. We sought to compare the efficacy and safety of CDT with other therapeutic options using network meta-analysis.

METHODS

We searched PubMed (MEDLINE), Embase, ClinicalTrials.gov and Cochrane Library from inception to Oct. 18, 2022. We included randomized controlled trials and observational studies that compared therapeutic options for PE, including anticoagulation, systemic thrombolysis and CDT among patients with intermediate- or high-risk PE. The efficacy outcome was in-hospital death. Safety outcomes included major bleeding, intracerebral hemorrhage and minor bleeding.

RESULTS

We included data from 44 studies, representing 20 006 patients. Compared with systemic thrombolysis, CDT was associated with a decreased risk of death (odd ratio [OR] 0.43, 95% confidence interval [CI] 0.32-0.57), intracerebral hemorrhage (OR 0.44, 95% CI 0.29-0.64), major bleeding (OR 0.61, 95% CI 0.53-0.70) and blood transfusion (OR 0.46, 95% CI 0.28-0.77). However, no difference in minor bleeding was observed between the 2 therapeutic options (OR 1.11, 95% CI 0.66-1.87). Compared with anticoagulation, CDT was also associated with decreased risk of death (OR 0.36, 95% CI 0.25-0.52), with no increased risk of intracerebral hemorrhage (OR 1.33, 95% CI 0.63-2.79) or major bleeding (OR 1.24, 95% CI 0.88-1.75).

INTERPRETATION

With moderate certainty of evidence, the risk of death and major bleeding complications was lower with CDT than with systemic thrombolysis. Compared with anticoagulation, CDT was associated with a probable lower risk of death and a similar risk of intracerebral hemorrhage, with moderate certainty of evidence. Although these findings are largely based on observational data, CDT may be considered as a first-line therapy in patients with intermediate- or high-risk PE.

PROTOCOL REGISTRATION

PROSPERO - CRD42020182163.

Clinical Observation of Uninterrupted Thrombolytic Therapy via Indwelling Catheter for Lower Limb Deep Vein Thrombosis

Purpose

Observe uninterrupted thrombolytic therapy via indwelling catheter for lower limb deep vein thrombosis.

Methods

We retrospectively studied data from 32 patients with lower extremity deep vein thrombosis who received comprehensive treatment, consisting of general treatment, inferior vena cava filter implantation, interventional thrombolysis, angioplasty, stenting, and post-operative monitoring.

Results

The efficacy and safety of the comprehensive treatment were observed for a follow-up period of 6-12 months. The treatment was 100% effective; patient results indicated no serious bleeding, acute pulmonary embolism, or death after surgery.

Conclusion

The combination of intravenous and healthy side femoral vein puncture and directed thrombolysis to treat acute lower limb deep vein thrombosis is safe, effective, and minimally invasive while still achieving a good therapeutic effect.

Current Status of Sub-micron Cavitation-Enhancing Agents for Sonothrombolysis

Thrombosis in cardiovascular disease is an urgent global issue, but treatment progress is limited by the risks of current antithrombotic approaches. The cavitation effect in ultrasound-mediated thrombolysis offers a promising mechanical alternative for clot lysis. Further addition of microbubble contrast agents introduces artificial cavitation nuclei that can enhance the mechanical disruption induced by ultrasound. Recent studies have proposed sub-micron particles as novel sonothrombolysis agents with increased spatial specificity, safety and stability for thrombus disruption. In this article, the applications of different sub-micron particles for sonothrombolysis are discussed. Also reviewed are in vitro and in vivo studies that apply these particles as cavitation agents and as adjuvants to thrombolytic drugs. Finally, perspectives on future developments in sub-micron agents for cavitation-enhanced sonothrombolysis are shared.

Endovascular Venous Interventions - A State-of-the-Art Review

Venous vascular diseases are an important clinical entity estimated to affect several million people worldwide. Deep vein thrombosis (DVT) is a common venous disease with a population variable prevalence of 122 to 160 persons per 100,000 per year, whereas pulmonary embolism (PE) affects up to 60 to 70 per 100 000 and carries much higher mortality. Chronic venous diseases, which cause symptoms like leg swelling, heaviness, pain, and discomfort, are most prevalent in the elderly and significantly impact their quality of life. Some estimate that chronic vascular diseases account for up to 2% of healthcare budgets in Western countries. Treating venous vascular disease includes using systemic anticoagulation and interventional therapies in some patient subsets. In this comprehensive review, we discuss endovascular treatment modalities in the management of venous vascular diseases.

The effects of pharmacomechanical thrombectomy on novel complete blood count parameters in deep vein thrombosis: A retrospective study

This study aimed to investigate the effects of pharmacomechanical thrombectomy on novel complete blood count parameters in deep venous thrombosis. This retrospective study included 242 patients aged >18 years who were treated for deep venous thrombosis. Patients were grouped as follows: group 1 was accepted as having interventional operations (n = 123) and group 2 was accepted as having only medical advice (n = 119). Routine complete blood count parameters, the neutrophil-to-lymphocyte ratio (NLR), and the platelet-to-lymphocyte ratio (PLR) were compared. There was no difference between the groups in terms of admission hemoglobin, hematocrit, mean platelet volume, NLR and PLR (P = .11, P = .24, P = .55, P = .93, and P = .96, respectively). In the pharmacomechanic thrombectomy group, NLR and PLR were significantly reduced after intervention when compared to the admission values (P < .001 and P < .001, respectively). However, the NLR and PLR values of medically treated patients did not differ significantly from their baseline values (P = .16 and P = .08, respectively). In this study, we effectively removed the thrombus load in blocked proximal veins using pharmacomechanical thrombectomy and observed a significant decrease in NLR and PLR, which are current, inexpensive, and accessible parameters.

Exploration of risk factors for hemoglobinuria and acute kidney injury following iliofemoral venous mechanical thrombectomy

Objective

To evaluate the risk factors for hemoglobinuria and acute kidney injury (AKI) after percutaneous mechanical thrombectomy (MT) with or without catheter-directed thrombolysis (CDT) for iliofemoral deep vein thrombosis (IFDVT).

Methods

Patients with IFDVT who had MT with the AngioJet catheter (group A), MT plus CDT (group B), or CDT alone (group C) from January 2016 to March 2020 were retrospectively evaluated. Hemoglobinuria was monitored throughout the treatment course, and postoperative AKI was assessed by comparing the preoperative (baseline) and postoperative serum creatinine (sCr) levels from the electronic medical records of all patients. AKI was defined as an elevation in the sCr level exceeding 26.5 ​μmol/L within 72 ​h after the operation according to the Kidney Disease Improving Global Outcomes criteria.

Results

A total of 493 consecutive patients with IFDVT were reviewed, of which 382 (mean age, 56 ​± ​11 years; 41% of them were females; 97 in group A, 128 in group B, and 157 in group C) were finally analyzed. Macroscopic hemoglobinuria was evident in 44.89% of the patients of the MT groups (101/225, 39 in group A, and 62 in group B), with no significant difference between the groups (P ​= ​0.219), but not in the patients in group C. None of the patients developed AKI (mean sCr difference -2.76 ​± ​13.80 ​μmol/L, range ​= ​-80.20 to 20.60 ​μmol/L) within 72 ​h after surgery.

Conclusions

Rheolytic MT is an independent risk factor for hemoglobinuria. A proper aspiration strategy, hydration, and alkalization following thrombectomy are particularly favorable for preventing AKI.

Thrombolysis Through Punctured Coronary Balloon and 014 Wire Mediated Guitaring After IVC Filter Insertion in Iliofemoral Deep Vein Thrombosis

This is a report of a patient who presented with iliofemoral deep vein thrombosis, and was treated with pharmaco-invasive and pharmaco-mechanic methods using coronary balloon and mechanical disruption of clots with coronary 014 wire. A 65-year-old male presented with acute deep vein thrombosis extending from the left common iliac to the popliteal vein. The patient had significant swelling and pain. An inferior vena cava (IVC) filter was inserted, and catheter-directed thrombolysis was planned. A technical difficulty was encountered entering the proximal common iliac vein. Hence, a 014 balance middle weight (BMW) wire with coronary balloon support was introduced through a Cordis^® 6 F. diagnostic catheter, and the 014 wire was advanced with guitaring technique up to the femoral vein. Thereafter, the coronary balloon was ruptured at high pressure, and thrombolysis using streptokinase was performed along the balloon tract up to the ostium of the common iliac vein. The patient symptomatically improved significantly and is currently on anticoagulants. Follow-up after one year showed minimal residual oedema, and less pain in the ankle region. Pharmaco-mechanical treatment is possible using coronary balloon dilatations and thrombolysis through a ruptured coronary balloon. Mechanical disruption of clots to some extent is feasible using 014 wire by a guitaring technique.

LEARNING POINTS

In difficult cases with deep vein thrombosis, coronary hardware could be used for balloon angioplasty, especially when the iliac bifurcation cannot be crossed.Even suboptimal results can lead to significant symptomatic improvement in deep venous thrombosis treatment.

ClotTriever system for mechanical thrombectomy of deep vein thrombosis

There is increasing evidence that early and comprehensive removal of thrombus in deep vein thrombosis is associated with improved outcomes, including decreased incidence of post-thrombotic syndrome and debilitating long-term symptoms. Catheter-directed thrombolysis is effective for the rapid removal of clot, but it is associated with high bleeding risk. Percutaneous mechanical thrombectomy is a highly effective method for the removal of clot without the use of systemic or catheter-directed thrombolytic therapy. The Inari ClotTriever system (Inari Medical Inc., CA, USA) is a thrombectomy device, which is approved for deep vein thrombosis by the US FDA in 2017. Herein we review the current treatment strategies using the ClotTriever system, its specifications, indications and current state of literature.

Catheter-Directed Interventions for the Treatment of Lower Extremity Deep Vein Thrombosis

Lower extremity deep vein thrombosis (DVT) leads to significant morbidity including pain, swelling, and difficulty walking in the affected limb. If left untreated, DVT increases the risk of pulmonary embolism (PE), recurrent venous thromboembolism (VTE), and post thrombotic syndrome (PTS). The objective of this review was to identify catheter-directed interventions and their success rates for the treatment of lower extremity DVT. A comprehensive search of current and emerging catheter-directed interventions for lower extremity DVT treatment was conducted in PubMed and Google Scholar. Clinical trials, retrospective and prospective observational studies, and case reports were identified to classify percutaneous mechanical thrombectomy (PMT), catheter-directed thrombolysis (CDT), and pharmacomechanical CDT (PCDT) devices based on their mechanism of action and indication of use. Catheter-directed interventions such as PMT, CDT, and PCDT offer an alternative therapeutic strategy for DVT management, particularly in patients with limb-threatening conditions and absolute contraindications to anticoagulants. Currently, there are limited guidelines for the use of mechanical and pharmacomechanical devices because of the lack of clinical evidence available for their use in treatment. Future studies are required to determine the short and long-term effects of using catheter-directed interventions as well as their effectiveness in treating acute versus subacute and chronic DVT.

May–Thurner Syndrome: A Forgotten Cause of Deep Vein Thrombosis

May–Thurner syndrome (MTS) is a relatively rare vascular condition that is characterized by external compression of the left common iliac vein by the right common iliac artery against the fifth lumbar vertebra. This condition slows the blood flow and is a predisposing factor for deep vein thrombosis (DVT). The key to its successful treatment is to remove the clot and fix the anatomical lesion. If this MTS diagnosis is missed, the recurrence of thrombosis will lead to significant morbidity and mortality. We report a case of 70-year-old female who had left leg DVT caused by MTS and was treated with catheter-directed thrombolysis along with long-term anticoagulation.

Subclavian Effort Thrombosis: Pathophysiology, Diagnosis, and Management

Subclavian vein (SCV) effort thrombosis, also known as Paget-Schroetter syndrome or venous thoracic outlet syndrome, is an uncommon condition that affects individuals with an irregularly narrow thoracic outlet who engage in repetitive overhead motions of the affected arm. Venous injury arises from microtraumas that occur from the repetitive compression of the SCV between the first rib and the overlying clavicle. Additional sources of extrinsic compression can be due to the anterior scalene muscle, subclavius muscle, and costoclavicular ligament. SCV effort thrombosis is a distinct entity from other forms of deep venous thrombosis and requires unique diagnostic and treatment considerations. Early catheter-directed therapy in the form of pharmacomechanical or catheter-directed thrombolysis combined with prompt surgical thoracic outlet decompression offers patients the best chances for early and durable symptom relief.

Ultrasound-Guided Intravascular Sonothrombolysis With a Dual Mode Ultrasound Catheter: In Vitro Study

Thromboembolism in vessels often leads to stroke or heart attack and even sudden death unless brought under control. Sonothrombolysis based on ultrasound contrast agents has shown promising outcome in effective treatment of thromboembolism. Intravascular sonothrombolysis transducer was reported recently for unprecedented sonothrombolysis in vitro. However, it is necessary to provide an imaging guide during thrombolysis in clinical applications for optimal treatment efficiency. In this article, a dual mode ultrasound catheter was developed by combining a 16-MHz high-frequency element (imaging transducer) and a 220-kHz low-frequency element (treatment transducer) for sonothrombolysis in vitro. The treatment transducer was designed with a 20-layer PZT-5A stack with the aperture size of 1.2×1.2 mm², and the imaging transducer with the aperture size of 1.2×1.2 mm² was attached in front of the treatment transducer. Both transducers were assembled into a customized 2-lm 10-Fr catheter. In vitro experiment was carried out using a bovine blood clot. Imaging tests were conducted, showing that the backscattering signals can be obtained with a high signal-to-noise ratio (SNR) for the 16-MHz imaging transducer. Sonothrombolysis was performed successfully that the volume of clot was reduced significantly after the 30-min treatment. The size changes of clot were observed clearly using the 16-MHz M-mode imaging during the thrombolysis. The findings suggest that the proposed ultrasound-guided intravascular sonothrombolysis can be enhanced since the position of treatment transducer can be adjusted with the target at the clot due to the imaging guide.

Invasive and Pharmacological Treatment of Deep Vein Thrombosis: a Scoping Review

The annual occurrence of venous thromboembolism (VTE) is 300,000-600,000 cases in the United States and 700,000 in Europe. VTE includes deep venous thrombosis (DVT) of upper or lower extremities, superior and inferior vena cava thrombosis, and pulmonary embolism (PE) as well. The primary treatment of DVT includes oral anticoagulation to prevent the progression of the thrombus and decrease the risk of pulmonary embolism. Depending on the symptoms, more invasive treatments can be applied to target the iliofemoral thrombus and its removal. However, less emphasis is given to acute symptomatology, early recovery of function, quality of life improvement, and the individualized likelihood of developing post-thrombotic syndrome. While invasive therapy has been used to enhance the acute management of iliofemoral DVT, our knowledge about the overall outcomes associated with the invasive treatment of VTE is still limited. In this review, we illustrate the available data on pharmacological and endovascular management of iliofemoral VTE, including therapies such as catheter-directed thrombolysis (CDT), mechanical thrombectomy (PMT), and pharmacomechanical catheter-directed thrombolysis (PCDT).

Multimodal thrombectomy device for treatment of acute deep venous thrombosis

Deep vein thrombosis (DVT) is a potentially deadly medical condition that is costly to treat and impacts thousands of Americans every year. DVT is characterized by the formation of blood clots within the deep venous system of the body. If a DVT dislodges it can lead to venous thromboembolism (VTE) and pulmonary embolism (PE), both of which can lead to significant morbidity or death. Current treatment options for DVT are limited in both effectiveness and safety, in part because the treatment of the DVT cannot be confined to a defined sequestered treatment zone. We therefore developed and tested a novel thrombectomy device that enables the sequesteration of a DVT to a defined treatment zone during fragmentation and evacuation. We observed that, compared to a predicate thrombectomy device, the sequestered approach reduced distal DVT embolization during ex vivo thrombectomy. The sequestered approach also facilitated isovolumetric infusion and suction that enabled clearance of the sequestered treatment zone without significantly impacting vein wall diameter. Results suggest that our novel device using sequestered therapy holds promise for the treatment of high risk large-volume DVTs.

Management of iliofemoral vein injury during open inguinal hernia repair

BACKGROUND

Vascular injuries during inguinal hernia repair are rarely reported. Especially in children, we have little information about vascular management.

CASE REPORT

In this article, we present a 6-year-old girl with right iliac vein ligation during inguinal hernia repair who was referred to our center and managed at the day of surgery. We recommended prior surgeon to order therapeutic heparin in dispatch time. The patient was treated with primary anastomosis of iliac vein and was admitted to pediatric intensive care unit (PICU). On the day following the operation, she had minimal dyspnea with low oxygen saturation and the investigations revealed pulmonary micro-embolization. Blood flow in lower extremity was normal and after a few days, she was discharged with good health and oral anticoagulation.

CONCLUSION

Any unusual bleeding at the time of inguinal hernia repair should be considered as major vascular injury by the surgeon, and to prevent more injuries, minimum attempt must be performed to control the bleeding.

High-Pressure Low-Frequency Lateral Mode Phased-Array Transducer System for the Treatment of Deep Vein Thrombosis: An In Vitro Study

Deep vein thrombosis (DVT) can lead to a fatal disease known as pulmonary embolism. Application of high-power ultrasound has been successful in studies to mechanically fragment the clots. Single-element ultrasound transducers were used in most of the studies. Challenges associated with phased arrays, such as high electrical impedance and element breakdown at high voltages, were addressed in the previous study, and a high-power 64-element transducer module was designed and fabricated. In this study, a cylindrical array of 16 modules with the frequency of 260 kHz was modeled and constructed for DVT thrombolysis. The maximum pressure, focal size, and steering ability of the array were examined. In vitro experiments were conducted to assess the performance of the array. The simulated pressure amplitude of 34 MPa at the depth of 55 mm (average femoral vein (FV) distance from the inner surface of the thigh) was in consistent with the experiments and satisfied the purpose of this study. Moreover, the employed module distribution resulted in a focal spot dimension of 2.4×2.8×7.3 mm³ (at the 75% pressure amplitude level) that can be confined in a human FV with the average diameter of 12 mm. In vitro experiments manifested a partial and complete clot breakdown at 11.5- and 15-MPa pressure at the focus. The design and engineering of the array system was succeeded in maintaining the desired pressure and focal size even when steered. The results presented in this study suggest the potential of the designed array system for clinical applications.

Breaking the fibrinolytic speed limit with microwheel co-delivery of tissue plasminogen activator and plasminogen

BACKGROUND

To reestablish blood flow in vessels occluded by clots, tissue plasminogen activator (tPA) can be used; however, its efficacy is limited by transport to and into a clot and by the depletion of its substrate, plasminogen.

OBJECTIVES

To overcome these rate limitations, a platform was designed to co-deliver tPA and plasminogen based on microwheels (µwheels), wheel-like assemblies of superparamagnetic colloidal beads that roll along surfaces at high speeds.

METHODS

The biochemical speed limit was determined by measuring fibrinolysis of plasma clots at varying concentrations of tPA (10-800 nM) and plasminogen (1-6 µM). Biotinylated magnetic mesoporous silica nanoparticles were synthesized and bound to streptavidin-coated superparamagnetic beads to make studded beads. Studded beads were loaded with plasminogen and tPA was immobilized on their surface. Plasminogen release and tPA activity were measured on the studded beads. Studded beads were assembled into µwheels with rotating magnetic fields and fibrinolysis of plasma clots was measured in a microfluidic device.

RESULTS

The biochemical speed limit for plasma clots was ~15 µm/min. Plasminogen-loaded, tPA-immobilized µwheels lyse plasma clots at rates comparableto the biochemical speed limit. With the addition of a corkscrew motion, µwheels penetrate clots, thereby exceeding the biochemical speed limit (~20 µm/min) and achieving lysis rates 40-fold higher than 50 nM tPA.

CONCLUSIONS

Co-delivery of an immobilized enzyme and its substrate via a microbot capable of mechanical work has the potential to target and rapidly lyse clots that are inaccessible by mechanical thrombectomy devices or recalcitrant to systemic tPA delivery.

Contrast enhanced sonothrombolysis using streptokinase loaded phase change nano-droplets for potential treatment of deep venous thrombosis

Current thrombolytic therapies for deep venous thrombosis are limited due to the wide side effect profile. Contrast mediated sonothrombolysis is a promising approach for thrombus treatment. The current study examines the effectiveness of in vitro streptokinase (SK) loaded phase-change nanodroplet (PCND) mediated sonothrombolysis at 7 MHz for the diagnosis of deep venous thrombosis. Lecithin shell and perfluorohexane core nanodroplets were prepared via the thin-film hydration method and morphologically characterized. Sonothrombolysis was performed at 7 MHz at different mechanical indexes of samples i.e., only sonothrombolysis, PCND mediated sonothrombolysis, sonothrombolysis with SK and SK loaded PCND mediated sonothrombolysis. Thrombolysis efficacy was assessed by measuring clot weight changes during 30 min US exposure, recording the mean gray intensity from the US images of the clot by computer software ImageJ, and spectrophotometric quantification of the hemoglobin in the clot lysate. In 15 minutes of sonothrombolysis performed at high mechanical index (0.9 and 1.2), SK loaded PCNDs showed a 48.61% and 74.29% reduction of mean gray intensity. At 0.9 and 1.2 MI, 86% and 92% weight loss was noted for SK-loaded PCNDs in confidence with spectrophotometric results. A significant difference (P < 0.05) was noted for SK-loaded PCND mediated sonothrombolysis compared to other groups. Loading of SK inside the PCNDs enhanced the efficacy of sonothrombolysis. An increase in MI and time also increased the efficacy of sonothrombolysis. This in vitro study showed the potential use of SK-loaded perfluorohexane core PCNDs as sonothrombolytic agents for deep venous thrombosis.

Contrast enhanced sonothrombolysis using streptokinase loaded phase change nano-droplets.

Dual-Frequency Intravascular Sonothrombolysis: An In Vitro Study

Thrombo-occlusive disease is one of the leading causes of death worldwide. There has been active research on safe and effective thrombolysis in preclinical and clinical studies. Recently, the dual-frequency transcutaneous sonothrombolysis with contrast agents [microbubbles (MBs)] has been reported to be more efficient in trigging the acoustic cavitation, which leads to a higher lysis rate. Therefore, there is increasing interest in applying dual-frequency technique for more significant efficacy improvement in intravascular sonothrombolysis since a miniaturized intravascular ultrasound transducer typically has a limited power output to fully harness cavitation effects. In this work, we demonstrated this efficacy enhancement by developing a new broadband intravascular transducer and testing dual-frequency sonothromblysis in vitro. A broadband intravascular transducer with a center frequency of 750 kHz and a footprint size of 1.4 mm was designed, fabricated, and characterized. The measured -6-dB fractional bandwidth is 68.1%, and the peak negative pressure is 1.5 MPa under the driving voltage of 80 V_pp. By keeping one frequency component at 750 kHz, the second frequency component was selected from 450 to 650 kHz with an interval of 50 kHz. The in vitro sonothrombolysis tests were conducted with a flow model and the results indicated that the MB-mediated, dual-frequency (750+500 kHz) sonothrombolysis yields an 85% higher lysis rate compared with the single-frequency treatment, and the lysis rate of dual-frequency sonothrombolysis increases with the difference between the two frequency components. These findings suggest a dual-frequency excitation technique for more efficient intravascular sonothrombolysis than conventional single-frequency excitation.

Deep venous thrombosis in an individual with statin-exposed anti-SRP myopathy: case report and review of literature

Background

Immune-mediated necrotizing myopathy (IMNM) is characterized by proximal muscle weakness, elvated serum muscle enzyme levels, myopathic electromyography findings, and necrotic muscle fiber with few inflammatory cell infiltration in muscle biopsies. Statins, the first line drug to lower triglyceride and cholesterol level in blood, have been reported to be associated with statins-induced necrotizing autoimmune myopathy (SINAM). Although anti-3-hydroxy-3-methylglutarylcoenzyme-A reductase (anti-HMGCR) myopathy is considered as the leading myopathy related to the statins medication, anti-signal recognition particle (SRP) myopathy were also identified in several cases with statin exposure. The risk of deep venous thrombosis (DVT) is substantially high in individuals with autoimmune inflammatory diseases. But few studies have reported the occurrence and recommendation for treatment of DVT in patients with anti-SRP myopathy. Here, we reported a statin-exposed anti-SRP myopathy individual developed DVT who was successfully treated with catheter-directed thrombolysis (CDT) and systemic anticoagulants therapy.

Case presentation

A 56-year-old Chinese female came to the outpatient room with gradually progressive bilateral lower-extremity weakness. Magnetic resonance imaging revealed myopathy in bilateral thighs. Serum anti-SRP antibody was positive. She was diagnosed with anti-SRP myopathy. When treated with corticosteroids and immunosuppressants, the patient developed mild edema and pain of left lower extremity. Angiography and ultrasound revealed diffuse venous thrombosis of left lower extremity. Therapy was initiated with CDT and lower molecular weight heparin, then switched to once daily oral rivaroxaban. Meanwhile, steroids combined with tacrolimus were also carried on while simvastatin was discontinued. One month later, patient’s symptoms were resolved and only partial thrombosis in left femoral vein was remained.

Conclusion

The prevalence of DVT in patient with anti-SRP myopathy was rare. No well-established treatment strategy is available to manage the IMNM and DVT at the same time. The systemic anticoagulants therapy combined CDT can be an effective therapeutic approach to address extensive DVT in patient with anti-SRP myopathy.

Assessment of histological characteristics, imaging markers, and rt-PA susceptibility of ex vivo venous thrombi

Venous thromboembolism is a significant source of morbidity and mortality worldwide. Catheter-directed thrombolytics is the primary treatment used to relieve critical obstructions, though its efficacy varies based on the thrombus composition. Non-responsive portions of the specimen often remain in situ, which prohibits mechanistic investigation of lytic resistance or the development of diagnostic indicators for treatment outcomes. In this study, thrombus samples extracted from venous thromboembolism patients were analyzed ex vivo to determine their histological properties, susceptibility to lytic therapy, and imaging characteristics. A wide range of thrombus morphologies were observed, with a dependence on age and etymology of the specimen. Fibrinolytic inhibitors including PAI-1, alpha 2-antiplasmin, and TAFI were present in samples, which may contribute to the response venous thrombi to catheter-directed thrombolytics. Finally, a weak but significant correlation was observed between the response of the sample to lytic drug and its magnetic microstructure assessed with a quantitative MRI sequence. These findings highlight the myriad of changes in venous thrombi that may promote lytic resistance, and imaging metrics that correlate with treatment outcomes.

Anticoagulation Treatment in Venous Thromboembolism: Options and Optimal Duration

Venous thromboembolism (VTE), clinically presenting as deep-vein thrombosis (DVT) or pulmonary embolism (PE), constitutes a major global healthcare concern with severe complications, long-term morbidity and mortality. Although several clinical, genetic and acquired risk factors for VTE have been identified, the molecular pathophysiology and mechanisms of disease progression remain poorly understood. Anticoagulation has been the cornerstone of therapy for decades, but there still are uncertainties regarding primary and secondary VTE prevention, as well as optimal therapy duration. In this review we discuss the role of factor Xa in coagulation cascade and the different choices of anticoagulation therapy based on patients' predisposing risk factors and risk of event recurrence. Further, we compare newer agents to traditional anticoagulation treatment, based on most recent studies and guidelines.

Management of Acute Iliofemoral Deep Venous Thrombosis in Inflammatory Bowel Disease - Transitioning From Conservative Management to Early Intervention

Deep vein thrombosis (DVT) is a frequent complication in patients suffering from inflammatory bowel disease (IBD), especially in those with frequent relapses of the disease or extensive inflammatory lesions. The aetiology for the increased risk is multifactorial.

Current evidence on management of acute iliofemoral DVT in IBD patients is scarce. This case series highlights two cases of active IBD, who developed acute iliofemoral DVTs and were treated with catheter-directed thrombolysis (CDT).

This report demonstrates that CDT is effective in clearing the clot burden and producing significant symptomatic improvement in the absence of major complications. An individualised approach must be taken for the management of IBD patients with acute iliofemoral DVT.

A multi-pillar piezoelectric stack transducer for nanodroplet mediated intravascular sonothrombolysis

We aim to develop a nanodroplet (ND)-mediated intravascular ultrasound (US) transducer for deep vein thrombosis treatments. The US device, having an efficient forward directivity of the acoustic beam, is capable of expediting the clot dissolution rate by activating cavitation of NDs injected onto a thrombus. We designed and prototyped a multi-pillar piezoelectric stack (MPPS) transducer composed of four piezoelectric stacks. Each stack was made of five layers of PZT-4 plates, having a dimension of 0.85 × 0.85 × 0.2 mm3. The transducer was characterized by measuring the electrical impedance and acoustic pressure, compared to simulation results. Next, in-vitro tests were conducted in a blood flow mimicking system using the transducer equipped with an ND injecting tube. The miniaturized transducer, having an aperture size of 2.8 mm, provided a high mechanical index of 1.52 and a relatively wide focal zone of 3.4 mm at 80 Vpp, 0.96 MHz electric input. The mass-reduction rate of the proposed method (NDs + US) was assessed to be 4.1 and 4.6 mg/min with and without the flow model, respectively. The rate was higher than that (1.3-2.7 mg/min) of other intravascular ultrasound modalities using micron-sized bubble agents. The ND-mediated intravascular sonothrombolysis using MPPS transducers was demonstrated with an unprecedented lysis rate, which may offer a new clinical option for DVT treatments. The MPPS transducer generated a high acoustic pressure (~3.1 MPa) at a distance of approximately 2.2 wavelengths from the small aperture, providing synergistic efficacy with nanodroplets for thrombolysis without thrombolytic agents.

Clot Degradation Under the Action of Histotripsy Bubble Activity and a Lytic Drug

Deep vein thrombosis is a major source of morbidity worldwide. For critical obstructions, catheter-directed thrombolytics are the frontline therapy to achieve vessel recanalization. Techniques that aid lytic therapy are under development to improve treatment efficacy and reduce procedure-related complications. Histotripsy is one such adjuvant under development that relies on focused ultrasound for in situ nucleation of bubble clouds. Prior studies have demonstrated synergistic effects for clot dissolution when histotripsy is combined with lytic therapy. The success of this combination approach is hypothesized to promote thrombolytic efficacy via two mechanisms: erythrocyte fractionation (hemolysis) and increased lytic activity (fibrinolysis). In this study, the contributions of hemolysis and fibrinolysis to clot degradation under histotripsy and a lytic were quantified with measurements of hemoglobin and D-dimer, respectively. A linear regression analysis was used to determine the relationship between hemoglobin, D-dimer, and the overall treatment efficacy (clot mass loss). A similar analysis was conducted to gauge the role of bubble activity, which was assessed with passive cavitation imaging, on hemolysis and fibrinolysis. Tabulation of these data demonstrated hemolysis and fibrinolysis contributed equally to clot mass loss. Furthermore, bubble cloud activity promoted the generation of hemoglobin and D-dimer in equal proportion. These studies indicate a multifactorial process for clot degradation under the action of histotripsy and a lytic therapy.

Anatomical consideration of deep calf veins: application to catheter-directed thrombolysis

Purpose

An antegrade approach is frequently used in catheter-directed thrombolysis to remove deep-vein thrombosis. However, the antegrade approach is difficult when accessing veins with small diameters; therefore, understanding the variation of deep calf vein is important.

Methods

This study measured the diameters and surface areas of the proximal and distal posterior tibial vein, peroneal vein, and anterior tibial vein to determine which are preferable for venous access. This study dissected 132 legs from Korean and Thai cadavers. The proximal and distal posterior tibial vein, peroneal vein, and anterior tibial vein were scanned and measured.

Results

The mean diameter and surface area were largest for the proximal tibial vein, at 6.34 mm and 0.312 cm², respectively, followed by the anterior tibial vein (5.22 mm and 0.213 cm²), distal posterior tibial vein (3.29 mm and 0.091 cm²), and peroneal vein (3.43 mm and 0.081 cm²). The proximal posterior tibial vein and anterior tibial vein have large diameters and surface areas, which make them ideal for applying an antegrade approach in catheter-directed thrombolysis.

Conclusions

The distal posterior tibial vein and peroneal vein are not recommended due to their smaller surface areas and also the anatomical variations therein.

May-Thurner Syndrome: A Case Report and a Concise Review

We report a case of a 31-year-oldman who presented to the hospital with extensive deep vein thrombosis (DVT) complicated by pulmonary embolism (PE) after a recent trauma and prolonged immobilization. He underwent contrast venography that revealed features of May-Thurner syndrome (MTS). He was managed with therapeutic anticoagulation, inferior vena cava filter placement, mechanical clot aspiration, catheter-directed thrombolytic therapy, and left common iliac vein stenting.

MTS is a vascular condition caused by the compression of the left common iliac vein by an overlying right common iliac artery against a vertebral body. This results in indolent endothelial changes secondary to the pulsating nearby artery as well as the compression increasing the susceptibility to venous thrombosis. Females are thought to be more prone to the condition due to the nature of their pelvic anatomy. Most patients are asymptomatic or present with unspecific symptoms, rendering the condition underdiagnosed. The gold standard diagnostic modality is contrast venography that reveals collaterals and a pressure gradient greater than 2 mmHg at rest across the stenotic region. Treatment is revolved around the removal of the thrombus along with the correction of the anatomical defect through interventional or surgical treatment to prevent a recurrence.

Untreated MTS complicated with DVT carries a risk of potentially life-threatening complications, such as PE, iliac vein rupture, retroperitoneal hematoma, or refractory DVT that is difficult to treat. Due to the chronicity of this syndrome, its management plan differs from that of other causes of DVT. Proper identification of MTS carries a positive outcome in treating DVT secondary to MTS. Here we are going to discuss a case diagnosed with MTS complicated by saddle PE outlying the possible pathophysiology, clinical manifestation, diagnostic tools, and management of complicated MTS.

Endovascular Therapy for the Management of Acute Ilio-femoral Deep Vein Thrombosis

Ilio-femoral deep vein thrombosis (DVT) has a high rate of long-term morbidity in the form of the postthrombotic syndrome (PTS). Therefore, management of acute thrombosis should not only focus on the prevention of acute complications such as propagation or embolisation of the initial clot but also on preventing recurrent thrombosis and PTS. Contemporary catheter-based treatments of deep vein thrombosis have proven to be safe and effective in selected patients. Current guidelines recommend medical therapy with anticoagulation alone for all but the most severe, limb-threatening thrombosis. They additionally allow for consideration of endovascular catheter-based treatment in selected patients with acute proximal ilio-femoral DVT and low risk of bleeding complications to prevent PTS. 

Imaging-guided, catheter-based endovascular therapy has been used in selected patients to alleviate these sequelae, but important questions remain about their optimal use. In this article, we review the available evidence and summarize the rationale for use of catheter-based therapy in specific patient groups with acute iliofemoral DVT.

Permanent IVC filter strut penetration into an abdominal aortic aneurysm

An 85-year-old man with a known history of abdominal aortic aneurysm (AAA) presented to a vascular surgery clinic with a severely swollen, tender and erythematous left leg. An urgent CT angiogram demonstrated a left-sided, proximal deep vein thrombosis, and a permanent, Bird's Nest inferior vena cava (IVC) filter (Cook, Inc., Bloomington, Ind.) penetrating his AAA. The patient was treated with a course of apixaban 5 mg two times per day and the decision was made to closely observe his IVC filter and AAA, given his numerous comorbidities and age. This case highlights the unique considerations associated with an approach to permanent IVC filter complications among patients with AAAs.

Catheter-directed thrombolysis and mechanical intervention in deep venous thrombosis: what is the status after the ATTRACT trial?

Deep venous thrombosis (DVT) is a major cause of acute and chronic morbidity, mortality, and increased healthcare costs. Endovascular methods for thrombus removal and reestablishing venous patency are increasing in both scope and usage. The most commonly used method for endovascular thrombectomy is catheter-directed thrombolysis (CDT). Several studies have shown promise for CDT in alleviating acute symptomatology in acute lower extremity DVT as well as mitigating potential long-term consequences of DVT, such as post-thrombotic syndrome (PTS). The Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) trial is the largest and most comprehensive randomized-controlled trial to date evaluating CDT compared to anticoagulation alone for the treatment of acute symptomatic proximal lower extremity DVT. This review discusses the current status of CDT and adjunctive endovascular interventions for DVT, particularly in the context of the ATTRACT trial.

Outcomes of Catheter-Directed Thrombolysis for Arteriovenous Fistula Thrombosis in Singapore: Is It Still Relevant Today?

Objective: To review the outcomes of catheter-directed thrombolysis (CDT) for salvage of thrombosed arteriovenous fistula (AVF) in a single centre in Southeast Asia.

Methods: A retrospective study of CDT in AVF between January 2015 and July 2018 at a tertiary university hospital was carried out.

Results: Within the study period, 85 patients underwent CDT for AVF thrombosis. Of these patients, 78% underwent CDT for 24 h and 12% required CDT for 48 h. Moreover, 14% of patients had bleeding during CDT and hence required a decrease in dosing or complete cessation. Incidence of intracranial haemorrhage was 1%, and technical success was 92%. Post CDT, primary patency rates at 12, 24 and 36 months were 87%, 62% and 36%, respectively; assisted primary patency rates at 12, 24 and 36 months were 96%, 82% and 69%, respectively; and secondary patency rates at 12, 24 and 36 months were 99%, 93% and 86%, respectively. Multivariate analysis did not identify any predictive factors for patency post CDT.

Conclusion: Within our study population, CDT for AVF salvage conferred good technical results with low rates of complications. There was good primary patency at 12 months, and the results were sustained up to 36 months. It remains a useful modality for fistula salvage, avoiding surgical intervention.

Phlegmasia Alba Dolens Complicating Rhabdomyolysis

A 57-year-old woman with obesity, severe dyslipidemia and hypertension presented with acute onset of excruciating pain at left leg followed by entire leg swelling without a specific provocation. Physical examination revealed a significant left lower limb oedema along with pale skin, livedo reticularis, poikilothermia, and diminished distal artery pulsation. Urgent vascular Doppler sonography of left lower limb showed obstructive venous thrombus and non-compressible vessel at level of iliofemoral vein. Arterial systems were without any obliteration but with relatively reduced flow to distal part. Blood test resulted in significantly raised creatinine and creatine kinase (CK) level. Diagnosis of phlegmasia alba dolens with complication of rhabdomyolysis and acute kidney injury had been made initially. The patient was treated with heparin as well as rehydration using saline solution and bicarbonate. Eventually, she had clinical improvement during hospitalization and been discharged with resolution of creatinine and CK level.

A thermosensitive material coated resonant stent for drug delivery on demand

An electromagnetic energy source in the radio-frequency range delivers power to a stent circuit via resonant inductive coupling, allowing a thermally triggered release of gel via Joule heating. A gold-electroplated, medical-grade stainless steel stent, serving as the base of the prototype device, melts a coating made from an emulsion composed mainly of dodecanoic acid. These coated devices produce wirelessly controllable releases of a gel into thermally regulated, stirred water that is near body temperature. The gel is made from salt, water, and gelatine from porcine skin and used to simulate drug release in this study. Thus, this system serves as a proof of concept to show the viability of controlling local drug delivery using this prototype device. Dodecanoic acid, a fatty acid, has a phase transition from solid to liquid near 43[Formula: see text]C and has relatively good biocompatibility. The average melting temperature of two different emulsions was 40.8±0.7[Formula: see text]C, a suitable value for the targeted application. Demonstration of controllable releases used electromagnetic pulses of approximately 180 seconds in duration, illustrating reproducibility of a controllable release phase while remaining relatively inert in the absence of stimuli. Releases were observable through measuring the conductivity of the water, the water temperature, and the stent temperature. This electrothermally active stent device enables wirelessly controlled local delivery with controlled dosage and timing, a concept with a wide range of potential applications. Some relevant examples include inhibiting restenosis or cancer treatment via targeted chemotherapy.

Feasibility of anticoagulation using low molecular-weight heparin during catheter-directed thrombolysis for lower extremity deep venous thrombosis

Background

The optimal anticoagulant scheme during catheter-directed thrombolysis (CDT) for deep venous thrombosis (DVT) remains unknown. This study was performed to evaluate the feasibility of anticoagulation therapy using low molecular-weight heparin (LMWH) during CDT for DVT.

Methods

The clinical data of DVT patients who underwent CDT during the past six years was retrospectively collected and reviewed. Patients were divided into therapeutic-dose anticoagulation (TPDA) and sub therapeutic-dose anticoagulation (sub-TPDA) groups according to LMWH dosage.

Results

A total of 61 patients involving 61 limbs were comprised. Acute and subacute DVT were identified in 39 (63.9%) and 22 (36.1%) patients, respectively. Thrombosis involving the iliac vein was identified in 34 (55.7%) patients. Inferior vena cava filter placement was performed in 38 (62.3%) patients. Intraoperatively, adjunctive balloons, stents, and thrombectomy were provided for nine (14.8%), four (6.6%), and one (1.6%) patients, respectively. Twenty (32.8%) patients accepted TPDA therapy, while 41 (67.2%) patients were administrated with sub-TPDA therapy. Median urokinase infusion rate was 2.5 (0.83 to 5) × 10⁴ U/h. Median infusion duration time was 4 (2 to 14) days, and median urokinase dose infused was 2.4 (0.6 to 10.80) × 10⁶ U. During CDT, five (8.2%) cases of minor bleeding were observed, and blood transfusion was not required. No major bleeding, symptomatic pulmonary embolisms, or death occurred. Complete (> 90%) and partial thrombolysis (50 ~ 90%) were achieved in 56 (91.8%) patients. In comparison with sub-TPDA group, TPDA group exhibited no significant differences in baseline characteristics, clinical improvement, thrombolysis results, and complications.

Conclusions

Anticoagulation therapy using low molecular-weight heparin during CDT with low infusion rate for DVT is likely to be feasible and safe. Sub-therapeutic-dose anticoagulation and therapeutic-dose could be used for CDT with similar clinical outcome and bleeding complications.

Referral patterns for catheter-directed thrombolysis for iliofemoral deep venous thrombosis

OBJECTIVES

Post thrombotic syndrome (PTS) is a serious complication of deep venous thromboses (DVTs). PTS occurs more frequently and severely following iliofemoral DVT compared to distal DVTs. Catheter directed thrombolysis (CDT) of iliofemoral DVTs may reduce PTS incidence and severity.We aimed to determine the rate of iliofemoral DVT within our institution, their subsequent management, and compliance with NICE guidelines.

METHODS

Retrospective review of all DVTs diagnosed over a 3-year period was conducted. Cases of iliofemoral DVT were identified using ICD-10 codes from patient notes, and radiology reports of Duplex scans. Further details were retrieved, such as patient demographics and referrals to vascular services. NICE guidance was applied to determine if patients would have been suitable for CDT. A survey was sent to clinicians within medicine to identify awareness of CDT and local guidelines for iliofemoral DVT management.

RESULTS

225 patients with lower limb DVTs were identified. Of these, 96 were radiographically confirmed as iliofemoral DVTs. The median age was 77. 67.7% of iliofemoral DVTs affected the left leg. Right leg DVTs made up 30.2% and 2.1% were bilateral DVTs. Of the 96 iliofemoral DVTs, 21 were deemed eligible for CDT. Only 3 patients (14.3%) were referred to vascular services, and 3 received thrombolysis.From our survey, 95.5% of respondents suggested anticoagulation alone as management for iliofemoral DVT. Only one respondent recommended referral to vascular services. There was a knowledge deficiency regarding venous anatomy, including superficial versus deep veins.

CONCLUSIONS

CDT and other mechanochemical procedures have been shown to improve outcomes of patients post-iliofemoral DVT, however a lack of awareness regarding CDT as a management option results in under-referral to vascular services. We suggest closer relations between vascular services and their "tributary" DVT clinics, development of guidelines and robust care pathways in the management of iliofemoral DVT.

Percutaneous thrombectomy using a novel single session device for acute iliofemoral deep vein thrombosis

A 74-year-old woman presented with acute symptomatic left thigh and calf swelling; imaging demonstrated evidence of occlusive thrombosis from the upper left common iliac vein to the mid-thigh. Single session zero-thrombolysis venous thrombectomy was performed using the ReVene^TM Thrombectomy Catheter.

Ten-year trends in iliofemoral deep vein thrombosis treatment and referral pathways

OBJECTIVES

Iliofemoral deep venous thrombosis is associated with an increased risk of developing post-thrombotic syndrome resulting in reduced quality of life. As there is debate about best management practices, this study aimed to examine the referral and treatment pathways for patients presenting with iliofemoral deep venous thrombosis over an 11-year period at our institution.

METHODS

We conducted a retrospective review of patients diagnosed with lower limb deep vein thrombosis between 2010 and 2020. Ultrasound report findings were reviewed for the presence of iliofemoral deep venous thrombosis with acute, occlusive, or proximal clot. Multiple factors were extracted, including patient demographics, risk factors, diagnostic methods, interventions, referrals, and details of follow-up. The CaVenT and ATTRACT trials studied the benefit of thrombolysis in the early phase of iliofemoral deep venous thrombosis management as compared to anticoagulation alone. An analysis was conducted of patients requiring thrombolysis to determine whether these trials impacted physician practice patterns for thrombolysis. Data were organized and examined by year for trends in treatment and referral pathways.

RESULTS

The review yielded 2792 patients assessed for lower limb deep venous thrombosis by ultrasound. Four hundred and sixty-seven (16.7%) patients were confirmed to have an occlusive iliofemoral deep venous thrombosis. The average age was 62.7 years (18-101 years). Half (50.4%) of the patients were male. The most common etiology for clot was malignancy-induced hypercoagulable state (39.0%). There was no difference in incidence of iliofemoral deep venous thrombosis diagnosed by ultrasound per year, with an average of 42.5 per year and a peak of 61. There was a trend towards increased rates of computed tomography imaging, ranging between 9.1% and 52.9%. The rate thrombolysis per year ranged between 1.8% and 8.9%, with a range of 4.3% (n = 20) to 8.9% (n = 5) in 2018. The use of pharmacomechanical thrombolysis increased, from 25% (n = 1) in 2010-2012 to 87.5% (n = 7) in 2018-2020. The rate of inferior vena cava filter insertion alone decreased from 18.2% in 2010 (n = 4) to 5.9% (n = 1) in 2020. The length of thrombolysis treatment also decreased, from 100% of patients (n = 4) receiving treatment duration greater than 24 h in 2010-2012 to 0% (n = 0) in 2018-2020. About 45% of patients receiving thrombolysis (n = 9) had venous stenting. No difference in treatment outcomes were observed, with greater than 87.5% of patients reaching intermediate to full resolution of clot burden. No patients experienced intracranial hemorrhage.

CONCLUSIONS

The results of this analysis highlight the change in practice in our institution over time. The low rate of intervention likely reflects the current lack of consensus in published guidelines. It is important for future work to elicit the most appropriate management pathways for patients with iliofemoral deep venous thrombosis.

Assessment of Aptamer-Targeted Contrast Agents for Monitoring of Blood Clots in Computed Tomography and Fluoroscopy Imaging

Objective: Random formation of thrombi is classified as a pathological process that may result in partial or complete obstruction of blood flow and limited perfusion. Further complications include pulmonary embolism, thrombosis-induced myocardial infraction, ischemic stroke, and others. Location and full delineation of the blood clot are considered to be two clinically relevant aspects that could streamline proper diagnosis and treatment follow-up. In this work, we prepared two types of X-ray attenuating contrast formulations, using fibrinogen aptamer as the clot-seeking moiety. Methods: Two novel aptamer-targeted formulations were designed. Iodine-modified bases were directly incorporated into a fibrinogen aptamer (iodo-FA). Isothermal titration calorimetry was used to confirm that these modifications did not negatively impact target binding. Iodo-FA was tested for its ability to produce concentration-dependent contrast enhancement in a phantom CT. It was subsequently tested in vitro with clotted human and swine blood. This allowed for translation into ex vivo testing, using fluoroscopy. FA was also used to functionalize gold nanoparticles (FA-AuNPs), and contrast capabilities were confirmed. This formulation was tested in vitro using clotted human blood in a CT scan. Results: Unmodified FA and iodo-FA demonstrated a nearly identical affinity toward fibrin, confirming that base modifications did not impact target binding. Iodo-FA and FA-AuNPs both demonstrated excellent concentration-dependent contrast enhancement capabilities (40.5 HU mM^-1 and 563.6 HU μM^-1, respectively), which were superior to the clinically available agent, iopamidol. In vitro CT testing revealed that iodo-FA is able to penetrate into the blood clots, producing contrast enhancement throughout, while FA-AuNPs only accumulated on the surface of the clot. Iodo-FA was thereby translated to ex vivo testing, confirming target-binding associated accumulation of the contrast material at the location of the clot within the dilation of the external carotid artery. This resulted in a 34% enhancement of the clot. Conclusions: Both iodo-FA and FA-AuNPs were confirmed to be effective contrast formulations in CT. Targeting of fibrin, a major structural constituent of thrombi, with these novel contrast agents would allow for higher contrast enhancement and better clot delineation in CT and fluoroscopy.