Endovascular management of venous thrombotic and occlusive diseases of the lower extremities

Up-and-over access is not an optimal pathway for percutaneous catheter-directed thrombolysis in acute iliofemoral popliteal venous thrombosis

OBJECTIVE

To analyze the feasibility and results of up-and-over access (UOA) for catheter-directed thrombolysis (CDT) in acute iliofemoral popliteal venous thrombosis (IFPVT).

METHODS

From June 2020 to June 2021, a total of 26 patients (26 lower limbs) undergoing CDT for IFPVT were included. According to the vascular access, the patients were divided into UOA group (n = 11, 10 left limbs and 1 right limb) and ipsilateral popliteal vein (ILPV) (n = 15, 15 left limbs) access group. The differences in preoperative characteristics and technical details between the two groups were compared.

RESULTS

Patients in UOA group were older than those in ILPV access group (67.64 ± 4.11 years VS. 52.73 ± 15.63 years, p = .003). The BMI of UOA group was significantly higher than that of ILPV access group (26.03 ± 1.62 kg/m² VS 24.71 ± 1.46 kg/m², p = .039). There were significantly more patients with simultaneous three comorbidities in UOA group than in ILPV access group (45.5% vs. 0, p = .043). Compared with ILPV access group, the duration of operation and fluoroscopy of UOA group were significantly longer (20.64 ± 3.41 min vs. 10.20 ± 1.42 min, p < .001; 18.18 ± 2.99 min vs. 6.13 ± 0.92 min, p < .001), but the technical success rate was significantly lower (54.5% vs. 100%, p = .007). In UOA group, the operation-related complications occurred, including catheter straying into lateral sacral vein (9.1%), retroperitoneal hematoma (9.1%), and thrombus shedding into filter (9.1%).

CONCLUSION

The UOA may be attempted in patients who are unable to be prone, but this access is not an optimal pathway for CDT.

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.

Cavitation Emissions Nucleated by Definity Infused through an EkoSonic Catheter in a Flow Phantom

The EkoSonic endovascular system has been cleared by the U.S. Food and Drug Administration for the controlled and selective infusion of physician specified fluids, including thrombolytics, into the peripheral vasculature and the pulmonary arteries. The objective of this study was to explore whether this catheter technology could sustain cavitation nucleated by infused Definity, to support subsequent studies of ultrasound-mediated drug delivery to diseased arteries. The concentration and attenuation spectroscopy of Definity were assayed before and after infusion at 0.3, 2.0 and 4.0 mL/min through the EkoSonic catheter. PCI was used to map and quantify stable and inertial cavitation as a function of Definity concentration in a flow phantom mimicking the porcine femoral artery. The 2.0 mL/min infusion rate yielded the highest surviving Definity concentration and acoustic attenuation. Cavitation was sustained throughout each 15 ms ultrasound pulse, as well as throughout the 3 min infusion. These results demonstrate a potential pathway to use cavitation nucleation to promote drug delivery with the EkoSonic endovascular system.

Thrombolytic strategies versus standard anticoagulation for acute deep vein thrombosis of the lower limb

BACKGROUND

Standard treatment for deep vein thrombosis (DVT) aims to reduce immediate complications. Use of thrombolytic clot removal strategies (i.e. thrombolysis (clot dissolving drugs), with or without additional endovascular techniques), could reduce the long-term complications of post-thrombotic syndrome (PTS) including pain, swelling, skin discolouration, or venous ulceration in the affected leg. This is the fourth update of a Cochrane Review first published in 2004.

OBJECTIVES

To assess the effects of thrombolytic clot removal strategies and anticoagulation compared to anticoagulation alone for the management of people with acute deep vein thrombosis (DVT) of the lower limb.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase, CINAHL and AMED and the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registries to 21 April 2020. We also checked the references of relevant articles to identify additional studies.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) examining thrombolysis (with or without adjunctive clot removal strategies) and anticoagulation versus anticoagulation alone for acute DVT.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as recommended by Cochrane. We assessed the risk of bias in included trials with the Cochrane 'Risk of bias' tool. Certainty of the evidence was evaluated using GRADE. For dichotomous outcomes, we calculated the risk ratio (RR) with the corresponding 95% confidence interval (CI). We pooled data using a fixed-effect model, unless we identified heterogeneity, in which case we used a random-effects model. The primary outcomes of interest were clot lysis, bleeding and post thrombotic syndrome.

MAIN RESULTS

Two new studies were added for this update. Therefore, the review now includes a total of 19 RCTs, with 1943 participants. These studies differed with respect to the thrombolytic agent, the doses of the agent and the techniques used to deliver the agent. Systemic, loco-regional and catheter-directed thrombolysis (CDT) strategies were all included. For this update, CDT interventions also included those involving pharmacomechanical thrombolysis. Three of the 19 included studies reported one or more domain at high risk of bias. We combined the results as any (all) thrombolysis interventions compared to standard anticoagulation. Complete clot lysis occurred more frequently in the thrombolysis group at early follow-up (RR 4.75; 95% CI 1.83 to 12.33; 592 participants; eight studies) and at intermediate follow-up (RR 2.42; 95% CI 1.42 to 4.12; 654 participants; seven studies; moderate-certainty evidence). Two studies reported on clot lysis at late follow-up with no clear benefit from thrombolysis seen at this time point (RR 3.25, 95% CI 0.17 to 62.63; two studies). No differences between strategies (e.g. systemic, loco-regional and CDT) were detected by subgroup analysis at any of these time points (tests for subgroup differences: P = 0.41, P = 0.37 and P = 0.06 respectively). Those receiving thrombolysis had increased bleeding complications (6.7% versus 2.2%) (RR 2.45, 95% CI 1.58 to 3.78; 1943 participants, 19 studies; moderate-certainty evidence). No differences between strategies were detected by subgroup analysis (P = 0.25). Up to five years after treatment, slightly fewer cases of PTS occurred in those receiving thrombolysis; 50% compared with 53% in the standard anticoagulation (RR 0.78, 95% CI 0.66 to 0.93; 1393 participants, six studies; moderate-certainty evidence). This was still observed at late follow-up (beyond five years) in two studies (RR 0.56, 95% CI 0.43 to 0.73; 211 participants; moderate-certainty evidence). We used subgroup analysis to investigate if the level of DVT (iliofemoral, femoropopliteal or non-specified) had an effect on the incidence of PTS. No benefit of thrombolysis was seen for either iliofemoral or femoropopliteal DVT (six studies; test for subgroup differences: P = 0.29). Systemic thrombolysis and CDT had similar levels of effectiveness. Studies of CDT included four trials in femoral and iliofemoral DVT, and results from these are consistent with those from trials of systemic thrombolysis in DVT at other levels of occlusion.

AUTHORS' CONCLUSIONS

Complete clot lysis occurred more frequently after thrombolysis (with or without additional clot removal strategies) and PTS incidence was slightly reduced. Bleeding complications also increased with thrombolysis, but this risk has decreased over time with the use of stricter exclusion criteria of studies. Evidence suggests that systemic administration of thrombolytics and CDT have similar effectiveness. Using GRADE, we judged the evidence to be of moderate-certainty, due to many trials having small numbers of participants or events, or both. Future studies are needed to investigate treatment regimes in terms of agent, dose and adjunctive clot removal methods; prioritising patient-important outcomes, including PTS and quality of life, to aid clinical decision making.

Safety and Efficacy of Aspiration Thrombectomy or Pharmacomechanical Thrombectomy after Catheter-Directed Thrombolysis for the Treatment of Acute Iliofemoral Deep Vein Thrombosis

PURPOSE

To evaluate the safety and efficacy of additional aspiration thrombectomy (AT) or pharmacomechanical thrombectomy (PMT) after catheter-directed thrombolysis (CDT) for the treatment of acute iliofemoral deep vein thrombosis (AIFDVT).

MATERIALS AND METHODS

Between May 2017 and December 2018, 40 patients with AIFDVT were enrolled. Twenty underwent AT after CDT (CDTAT), while the remaining 20 underwent PMT using an AngioJetTM device after CDT (CDTPMT). Thrombus clearance was assessed using computed tomography venography at 1 week after the procedure, as follows: grade I, ≤50%; grade II, 51% to 75%; grade III, >75%. Grade III was considered a successful outcome. Treatment outcomes (thrombus clearance, thrombolytic therapy duration, urokinase dose, major complications, residual filter thrombosis, and Villalta score) were compared between the groups.

RESULTS

Successful thrombus clearance was achieved in 95% of the patients in both groups. Significant decreases in the thrombolytic therapy duration (P=0.018) and urokinase dose (P=0.014) were noted in the CDTPMT group. Major complications were not noted in both groups. Residual filter thrombi >10 mm were found in 6 filters in the CDTAT group and in 1 filter in the CDTPMT group (P=0.038). The Villalta scores at 6 months were 1.47±1.24 and 1.12±0.92 in the CDTAT and CDTPMT groups, respectively (P=0.372).

CONCLUSION

Both methods may be safe and effective management options for patients with AIFDVT. CDTPMT can reduce urokinase dosage, time and remained filter thrombus compared to CDTAT. Studies conducted in the future should compare the effects of overnight CDT followed by PMT with those of single-session PMT on patients with AIFDVT.

[Thrombectomy for acute iliofemoral thrombosis in prevention of pulmonary embolism]

BACKGROUND

Acute thrombosis in the system of the inferior vena cava is one of the most common vascular diseases and is of serious danger as a potential source of one of the most severe complications. In order to assess efficacy of open thrombectomy for embologenic iliofemoral venous thromboses we carried out comparison of the results of open thrombectomy and implantation of cava filters in a total of 119 patients presenting with iliofemoral thrombosis.

PATIENTS AND METHODS

Open thrombectomy was performed in a total of 59 patients. Of these, 12 patients with segmental thromboses underwent radical thrombectomy and 47 patients with disseminated forms of thrombosis were subjected to partial thrombectomy with plication of the femoral vein. In 5 patients, the operation was supplemented with applying an arteriovenous fistula. Efficacy of operations was assessed with the help of ultrasonographic duplex angioscanning and regression of clinical manifestations. In the remote period, the degree of manifestations of post-thrombotic disease was assessed by means of the Villalta scale.

RESULTS

After radical thrombectomy, patency of the iliofemoral segment was preserved in all patients during the whole follow-up period. In the group of patients with partial thrombectomy, 5 (9.5%) patients developed rethrombosis above the placation site at terms from 8 to 12 months. Four-year patency of the iliofemoral segment in this group of patients amounted to 81.5%. In patients with implanted cava filters, neither femoral vein nor iliac segment were patent completely. During the first year, thrombosis of cava filter developed in 9 cases; after 2 years, occlusion of the cava filter was diagnosed in 7 patients. In clinical assessment of the remote results with the use of the Villalta scale in patients after open thrombectomy the symptoms of post-traumatic disease were absent or weakly pronounced. After implantation of the cava filter all patients demonstrated the clinical course of post-traumatic disease, corresponding to 10-15 points.

CONCLUSION

Open thrombectomy for iliofemoral embologenic thromboses performed at specialized departments is a radical method of preventing thromboembolic complications and promotes restoration or improvement of venous blood flow in the extremity.

Integrated Histotripsy and Bubble Coalescence Transducer for Thrombolysis

After the collapse of a cavitation bubble cloud, residual microbubbles can persist for up to seconds and function as weak cavitation nuclei for subsequent pulses in a phenomenon known as cavitation memory effect. In histotripsy, the cavitation memory effect can cause bubble clouds to repeatedly form at the same discrete set of sites. This effect limits the efficacy of histotripsy-based tissue fractionation. Our previous studies have indicated that low-amplitude bubble-coalescing (BC) ultrasound sequences interleaved with high-amplitude histotripsy pulses can coalesce the residual bubbles into one large bubble quickly. This reduces the cavitation memory effect and may increase treatment efficacy. Histotripsy has been investigated for thrombolysis by breaking up clots into debris smaller than red blood cells. However, this treatment has low efficacy for aged or retracted clots. In this study, we investigate the use of histotripsy with BC to improve the efficacy of treatment of retracted clots. An integrated histotripsy and bubble-coalescing (HBC) transducer system with specialized electronic driving system was built in-house. One high-amplitude (32 MPa), one-cycle histotripsy pulse followed by 36 low-amplitude (2.4 MPa), one-cycle BC pulses formed one HBC sequence. Results indicate that HBC sequences successfully generated a flow channel through the retracted clots at scan speeds of 0.2-0.5 mm/s. The channel size created using the HBC sequence was 128% to 480% larger than that created using histotripsy alone. The clot debris particles generated during HBC treatments were within the tolerable range. These results illustrate the concept that BC improves the treatment efficacy of histotripsy thrombolysis for retracted clots.

Non-Invasive Thrombolysis Using Microtripsy in a Porcine Deep Vein Thrombosis Model

Histotripsy is a non-invasive therapeutic technique that uses ultrasound generated from outside the body to create controlled cavitation in targeted tissue, and fractionates it into acellular debris. We have developed a new histotripsy approach, termed microtripsy, to improve targeting accuracy and to avoid collateral tissue damage. This in vivo study evaluates the safety and efficacy of microtripsy for non-invasive thrombolysis in a porcine deep vein thrombosis model. Acute thrombi were formed in left femoral veins of pigs (∼35 kg) by occluding the vessel using two balloon catheters and infusing with thrombin. Guided by real-time ultrasound imaging, microtripsy thrombolysis treatment was conducted in 14 pigs; 10 pigs were euthanized on the same day (acute) and 4 at 2 wk (subacute). To evaluate vessel damage, 30-min free-flow treatment in the right femoral vein (no thrombus) was also conducted in 8 acute pigs. Blood flow was successfully restored or significantly increased after treatment in 13 of the 14 pigs. The flow channels re-opened by microtripsy had a diameter up to 64% of the vessel diameter (∼6 mm). The average treatment time was 16 min per centimeter-long thrombus. Only mild intravascular hemolysis was induced during microtripsy thrombolysis. No damage was observed on vessel walls after 2 wk of recovery, venous valves were preserved, and there was no sign of pulmonary embolism. The results of this study indicate that microtripsy has the potential to be a safe and effective treatment for deep vein thrombosis in a porcine model.

Midterm Outcomes of Pharmacomechanical Thrombectomy in the Treatment of Lower Extremity Deep Vein Thrombosis With a Rotational Thrombectomy Device

Background:

The purpose of this study was to assess the safety and efficacy with midterm outcomes of pharmacomechanical thrombectomy (PMT) performed by using a relatively new thrombectomy device in the treatment of lower extremity deep vein thrombosis (DVT).

Methods:

Between February 2014 and February 2016, a total of 46 patients with lower extremity DVT were treated with PMT by using Cleaner rotational thrombectomy system. Preprocedural, intraprocedural, postprocedural, and follow-up records of patients were collected and retrospectively analyzed.

Results:

Mean age of patients was 50.5 (14.8) years, and 58.7% of them were female. Technical success rate of procedure was 91.3%. Mean procedure time was 81.8 (40.3) minutes. Early clinical improvement was observed in all patients with successful treatment. No serious adverse event related to procedure and mortality was observed. Mean follow-up time was 16.0 (7.9) months. Reocclusion was observed in 7 (17.5%) patients during the follow-up period. Venous patency rates of patients at 1-, 3-, 6-, and 12-month follow-up visits were 95%, 92.5%, 89.7%, and 79.5%, respectively. Mild, moderate, and severe postthrombotic syndrome were observed in 8 (20%) patients, 4 (10%) patients, and 1 (2.5%) patient, respectively. Postthrombotic syndrome–free survival rate was 67.5%.

Conclusion:

Cleaner rotational thrombectomy system appears to be safe and effective in the treatment of lower extremity DVT. Further larger randomized studies are needed to determine the long-term outcomes of this treatment modality.

Effect of pulse repetition frequency of high-intensity focused ultrasound on in vitro thrombolysis

Vascular occlusion by the thrombi is the main reason for ischemic stroke and deep vein thrombosis. High-intensity focused ultrasound (HIFU) and histotripsy or microtripsy pulses can effectively dissolve the blood clot with no use of thrombolytic agent and ultrasound contrast agent (microbubbles). In this study, HIFU bursts at the same duty cycle (2%) but varied pulse repetition frequency (PRF) from 1Hz to 1000Hz were delivered to in vitro porcine blood clot for 30s. Thrombolysis efficiency initially increases slightly with the PRF, 86.4±10.3%, 89.9±11.9, and 92.9±12.8% at the PRF of 1Hz, 10Hz, and 100Hz, respectively, without significant difference (p>0.05), but then drops dramatically to 37.9±6.9% at the PRF of 1000Hz (p<0.05). The particle size in the supernatant of dissolution is 547.1±129.5nm, which suggests the disruption of thrombi into the subcellular level. Thrombi motion during HIFU exposure shows violent motion and significant curling at the low PRF, rotation about its axis with occasional curling at the moderate PRF, and localized vibration at the high PRF due to the generation of acoustic radiation force and streaming. Quantitative analysis of recorded motion shows the axial displacement decreases with the PRF of delivered HIFU bursts, from 3.9±1.5mm at 1Hz to 0.7±0.4mm at 1000Hz. Bubble cavitation during HIFU exposure to the blood clot was also monitored. The increase of PRF led to the increase of inertial cavitation but the decrease of stable cavitation. In summary, the PRF of delivered HIFU bursts at the same output energy has a significant effect on the thrombi motion, bubble cavitation activities, and subsequently thrombolysis efficiencies.

Microbubble-Based Sonothrombolysis Using a Planar Rectangular Ultrasonic Transducer

BACKGROUND

The aim of the proposed study was to evaluate in an in vitro flow model the ability of small planar rectangular (2 × 10 mm²) ultrasonic transducer to enhance thrombolysis induced by the thrombolytic agent tenecteplase (TNK-tPA).

METHODS

To provide a more realistic clinical environment of stroke, the study was conducted under realistic flow conditions and TNK-tPA concentrations. Fully retracted porcine blood clots were used to determine the thrombolytic efficacy of ultrasound (US) waves as an adjunct to TNK-tPA or in combination with microbubbles (MBs). Two ultrasonic flat rectangular transducers were used in the experiments, operating at 3.7 and 5.2 MHz respectively. A pulsed US protocol that maintained temperature elevation at the target of 1°C was applied. Thrombolysis efficacy was measured in milligrams of mass clot removed.

RESULTS

The effect of experimental parameters, such as power, frequency, and MBs administration, on thrombolysis efficacy was explored.

CONCLUSIONS

The results revealed that thrombolysis efficacy decreases at higher frequency, and therefore, the possibility of using lower frequency to improve efficacy should be further investigated. Additionally, study findings demonstrated that the combination of 3.7 MHz with MBs as an adjunct to TNK-tPA strongly enhanced thrombolysis efficacy, because with 30 minutes of treatment, 700 mg of clot was removed through nonthermal mechanisms. As a final point, this study has shown that MBs dose influences thrombolysis enhancement, because higher thrombolytic efficacy was observed with higher doses of MBs.

Diagnosis and Treatment of Lower Extremity Deep Vein Thrombosis: Korean Practice Guidelines

Lower extremity deep vein thrombosis is a serious medical condition that can result in death or major disability due to pulmonary embolism or post-thrombotic syndrome. Appropriate diagnosis and treatment are required to improve symptoms and salvage the affected limb. Early thrombus clearance rapidly resolves symptoms related to venous obstruction, restores valve function and reduces the incidence of post-thrombotic syndrome. Recently, endovascular treatment has been established as a standard method for early thrombus removal. However, there are a variety of views regarding the indications and procedures among medical institutions and operators. Therefore, we intend to provide evidence-based guidelines for diagnosis and treatment of lower extremity deep vein thrombosis by multidisciplinary consensus. These guidelines are the result of a close collaboration between interventional radiologists and vascular surgeons. The goals of these guidelines are to improve treatment, to serve as a guide to the clinician, and consequently to contribute to public health care.

Multimodal Therapy for Acute and Chronic Venous Thrombotic and Occlusive Disease

Critical deep venous thrombosis and occlusion constitutes a small percentage of patients with venous disease. However, these patients exhibit severe symptomatology including pain and extensive edema that may progress to limb-or life-threatening complications such as phlegmasia cerulea dolens and superior vena cava syndrome. This paper reviews the different multimodal percutaneous interventions currently available for the treatment of complex critical venous thrombotic and occlusive disease.

Endoluminal Recanalization in a Patient with Phlegmasia Cerulea Dolens Using a Multimodality Approach

Phlegmasia cerulea dolens is a limb-threatening form of deep venous thrombosis and should be treated aggressively. The authors report a patient who presented with iliocaval and femoral deep venous thrombosis and posed an additional therapeutic challenge based on a recent history of heparin-induced thrombocytopenia. Catheter-directed pharmacologic thrombolysis and balloon venoplasty were applied in treatment. The direct thrombin inhibitor argatroban was used in place of heparin for concurrent anticoagulation. This multimodality endovascular approach (chemical and mechanical interventions) was successful in relieving the venous occlusion and salvaging the limb, while maintaining appropriate treatment for heparin-induced thrombocytopenia.

Histotripsy Thrombolysis on Retracted Clots

Retracted blood clots have been previously recognized to be more resistant to drug-based thrombolysis methods, even with ultrasound and microbubble enhancements. Microtripsy, a new histotripsy approach, has been investigated as a non-invasive, drug-free and image-guided method that uses ultrasound to break up clots with improved treatment accuracy and a lower risk of vessel damage compared with the traditional histotripsy thrombolysis approach. Unlike drug-mediated thrombolysis, which is dependent on the permeation of the thrombolytic agents into the clot, microtripsy controls acoustic cavitation to fractionate clots. We hypothesize that microtripsy thrombolysis is effective on retracted clots and that the treatment efficacy can be enhanced using strategies incorporating electronic focal steering. To test our hypothesis, retracted clots were prepared in vitro and the mechanical properties were quantitatively characterized. Microtripsy thrombolysis was applied on the retracted clots in an in vitro flow model using three different strategies: single-focus, electronically-steered multi-focus and dual-pass multi-focus. Results show that microtripsy was used to successfully generate a flow channel through the retracted clot and the flow was restored. The multi-focus and the dual-pass treatments incorporating the electronic focal steering significantly increased the recanalized flow channel size compared to the single-focus treatments. The dual-pass treatments achieved a restored flow rate up to 324 mL/min without cavitation contacting the vessel wall. The clot debris particles generated from microtripsy thrombolysis remained within the safe range. The results of this study show the potential of microtripsy thrombolysis for retracted clot recanalization with the enhancement of electronic focal steering.

Prophylactic Placement of an Inferior Vena Cava Filter During Aspiration Thrombectomy for Acute Deep Venous Thrombosis of the Lower Extremity

Purpose:

To evaluate the effect of an inferior vena cava (IVC) filter during aspiration thrombectomy for acute deep vein thrombosis (DVT) in the lower extremity.

Materials and Methods:

From July 2004 to December 2013, a retrospective analysis of 106 patients with acute DVT was performed. All patients received an IVC filter and were treated initially with aspiration thrombectomy. Among the 106 patients, DVT extension into the IVC was noted in 27 but was not evident in 79. We evaluated the presence of trapped thrombi in the filters after the procedure. The sizes of the trapped thrombi were classified into 2 grades based on the ratio of the maximum transverse length of the trapped thrombus to the diameter of the IVC (Grades I [≤ 50%] and II [> 50%]).

Results:

A trapped thrombus in the filter was detected in 46 (43%) of 106 patients on final venograms. The sizes of the trapped thrombi were grade I in 12 (26.1%) patients and grade II in 34 (73.9%). Among the 27 patients with DVT extension into the IVC, 20 (74.1%) showed a trapped thrombus in the filter, 75% (15 of 20) of which were grade II. Among the 79 patients without DVT extension into the IVC, 26 (32.9%) showed a trapped thrombus in the IVC filter, 73% (19 of 26) of which were grade II.

Conclusions:

Thrombus migration occurred frequently during aspiration thrombectomy of patients with acute DVT in the lower extremity. However, further studies are needed to establish a standard protocol for the prophylactic placement of an IVC filter during aspiration thrombectomy.

A phantom model study to identify the most effective manual aspiration thrombectomy for acute deep-vein thrombosis of the lower extremity

AIM

To identify the most effective manual aspiration thrombectomy (MAT) method for the initial endovascular management of acute deep-vein thrombosis (DVT) in the lower extremity using a phantom model.

MATERIALS AND METHODS

An acute DVT phantom model was created by infusing a bovine acute thrombus in a 20-mm diameter, 120-cm long plastic tube with banding of the distal portion. A total of 32 types of aspiration methods using combinations of two aspiration catheters (8 and 10 Fr), four syringes (10, 20, 40, and 50 ml), and four different aspiration methods (I, II, III, and IV) were performed. Each method was performed 10 times. The total weight of the aspirated thrombus was measured and compared among the 32 aspiration methods. The aspiration methods were classified based on the length of the dynamic catheter withdrawal (0 cm [method I], 15 cm [II], 30 cm [III], or >45 cm [IV]) while maintaining continuous negative pressure using a syringe. Analysis of variance and Student's t-test were used for statistical analysis.

RESULTS

There were no statistically significant differences in the total amount of aspirated thrombus among the various types of aspiration catheters and syringes; however, different aspiration methods showed significantly different results. Acute thrombus was most effectively aspirated by method IV irrespective of the catheter and syringe used. The longer the length of dynamic catheter withdrawal, the greater the amount of total thrombi that could be aspirated, irrespective of the type of aspiration catheter and syringe used (IV > III > II > I; p<0.05).

CONCLUSION

MAT can be performed most effectively using method IV. Effective MAT relies on the length of the dynamic catheter withdrawal while maintaining continuous negative pressure using a syringe in the initial endovascular management of acute DVT in the lower extremity.

Noninvasive thrombolysis using microtripsy: a parameter study

Histotripsy fractionates soft tissue by well-controlled acoustic cavitation using microsecond-long, high-intensity ultrasound pulses. The feasibility of using histotripsy as a noninvasive, drug-free, and image-guided thrombolysis method has been shown previously. A new histotripsy approach, termed microtripsy, has recently been investigated for the thrombolysis application to improve treatment accuracy and avoid potential vessel damage. In this study, we investigated the effects of pulse repetition frequency (PRF) on microtripsy thrombolysis. Microtripsy thrombolysis treatments using different PRFs (5, 50, and 100 Hz) and doses (20, 50, and 100 pulses) were performed on blood clots in an in vitro vessel flow model. To quantitatively evaluate the microtripsy thrombolysis effect, the location of focal cavitation, the incident rate of pre-focal cavitation on the vessel wall, the size and location of the resulting flow channel, and the generated clot debris particles were measured. The results demonstrated that focal cavitation was always well confined in the vessel lumen without contacting the vessel wall for all PRFs. Pre-focal cavitation on the front vessel wall was never observed at 5Hz PRF, but occasionally observed at PRFs of 50 Hz (1.2%) and 100 Hz (5.4%). However, the observed pre-focal cavitation was weak and did not significantly affect the focal cavitation. Results further demonstrated that, although the extent of clot fractionation per pulse was the highest at 5 Hz PRF at the beginning of treatment (<20 pulses), 100 Hz PRF generated the largest flow channels with a much shorter treatment time. Finally, results showed fewer large debris particles were generated at a higher PRF. Overall, the results of this study suggest that a higher PRF (50 or 100 Hz) may be a better choice for microtripsy thrombolysis to use clinically due to the larger resulting flow channel, shorter treatment time, and smaller debris particles.

Histotripsy methods in mechanical disintegration of tissue: towards clinical applications

In high intensity focused ultrasound (HIFU) therapy, an ultrasound beam is focused within the body to locally affect the targeted site without damaging intervening tissues. The most common HIFU regime is thermal ablation. Recently there has been increasing interest in generating purely mechanical lesions in tissue (histotripsy). This paper provides an overview of several studies on the development of histotripsy methods toward clinical applications. Two histotripsy approaches and examples of their applications are presented. In one approach, sequences of high-amplitude, short (microsecond-long), focused ultrasound pulses periodically produce dense, energetic bubble clouds that mechanically disintegrate tissue. In an alternative approach, longer (millisecond-long) pulses with shock fronts generate boiling bubbles and the interaction of shock fronts with the resulting vapour cavity causes tissue disintegration. Recent preclinical studies on histotripsy are reviewed for treating benign prostatic hyperplasia (BPH), liver and kidney tumours, kidney stone fragmentation, enhancing anti-tumour immune response, and tissue decellularisation for regenerative medicine applications. Potential clinical advantages of the histotripsy methods are discussed. Histotripsy methods can be used to mechanically ablate a wide variety of tissues, whilst selectivity sparing structures such as large vessels. Both ultrasound and MR imaging can be used for targeting and monitoring the treatment in real time. Although the two approaches utilise different mechanisms for tissue disintegration, both have many of the same advantages and offer a promising alternative method of non-invasive surgery.

Catheter-directed thrombolysis in deep vein thrombosis: Which procedural measurement predicts outcome?

The post-thrombotic syndrome (PTS) as a long-term consequence of deep vein thrombosis (DVT) is caused by a venous obstruction and/or chronic insufficiency of the deep venous system. New endovascular therapies enable early recanalization of the deep veins aiming reduced incidence and severity of PTS. Extended CDT is associated with an increased risk of bleeding and stenting of residual venous obstruction is indispensable to avoid early rethrombosis. Therefore, this article focuses on measurements during or after thrombolysis indicating post procedural outcome.

The results of aspiration thrombecomy in the endovascular treatment for iliofemoral deep vein thrombosis

Purpose

The aim of this study is to evaluate the results of aspiration thrombectomy (AT) in the endovascular treatment for iliofemoral deep vein thrombosis (DVT) through the comparison of catheter directed thrombolysis (CDT) alone group and CDT with AT group.

Methods

From November 2001 to April 2011, 100 patients received endovascular treatment with CDT alone or CDT with AT for iliofemoral DVT at Yeungnam University Medical Center. We compared procedure, clinical outcomes and complications between the two groups.

Results

The mean age of patients was 60.48 ± 14.57 years. The patients consisted of 41 men and 59 women. CDT alone and CDT with AT were performed in 29 and 71 patients, respectively. The mean procedural time of the CDT-alone group was longer than the CDT with AT group (P < 0.001) and dose of urokinase used during the procedure significantly decreased in the CDT with AT group (P < 0.001). There were no statistically significant differences in clinical outcomes between the two groups. Cases of pulmonary embolism was not noted in each group in our series, but entrapped thrombus during procedure was noted in 6 of 37 in the CDT with AT group and 0 of 9 in the CDT-alone group among 46 patients with prophylactic inferior vena cava (IVC) filter insertion.

Conclusion

In conclusion, CDT with AT is safe and effective for the treatment of an acute iliofemoral DVT. In AT treatment, prophylactic IVC filter insertion should be considered for the prevention of pulmonary embolism by floating thrombi.

Prophylactic Implantation of Inferior Vena Cava Filter during Endovascular Therapies for Deep Venous Thrombosis of the Lower Extremities

Patients with deep venous thrombosis (DVT) of the lower extremities have an increased risk of pulmonary emboli and post-thrombotic syndrome. Traditionally, they are treated medicinally, with anticoagulation therapy. Currently, endovascular therapies, with their higher efficiency, have replaced previously attempted systemic fibrinolytic therapies. There is a continuing controversy in the temporary use of filters in the inferior vena cava during these endovascular therapies, which may include catheter-directed thrombolysis, manual aspiration, mechanical thrombectomy, percutaneous transluminal angioplasty and placement of self-expandable metallic stents. Here, we present an overview of the literature and analysis on the application of prophylactic implantation of an inferior vena cava filter during endovascular therapy for DVT of the lower extremities.

Noninvasive treatment of deep venous thrombosis using pulsed ultrasound cavitation therapy (histotripsy) in a porcine model

PURPOSE

This study evaluated histotripsy as a noninvasive, image-guided method of thrombolysis in a porcine model of deep vein thrombosis. Histotripsy therapy uses short, high-intensity, focused ultrasound pulses to cause mechanical breakdown of targeted soft tissue by acoustic cavitation, which is guided by real-time ultrasound imaging. This is an in vivo feasibility study of histotripsy thrombolysis.

METHODS AND MATERIALS

Acute thrombi were formed in the femoral vein of juvenile pigs weighing 30-40 kg by balloon occlusion with two catheters and thrombin infusion. A 10-cm-diameter 1-MHz focused transducer was used for therapy. An 8-MHz ultrasound imager was used to align the clot with the therapy focus. Therapy consisted of five cycle pulses delivered at a rate of 1 kHz and peak negative pressure between 14 and 19 MPa. The focus was scanned along the long axis of the vessel to treat the entire visible clot during ultrasound exposure. The targeted region identified by a hyperechoic cavitation bubble cloud was visualized via ultrasound during treatment.

RESULTS

Thrombus breakdown was apparent as a decrease in echogenicity within the vessel in 10 of 12 cases and in 7 cases improved flow through the vein as measured by color Doppler. Vessel histology found denudation of vascular endothelium and small pockets of hemorrhage in the vessel adventitia and underlying muscle and fatty tissue, but perforation of the vessel wall was never observed.

CONCLUSIONS

The results indicate histotripsy has potential for development as a noninvasive treatment for deep vein thrombosis.

Deep vein thrombosis: endovascular management

Deep vein thrombosis is a condition that affects hundreds of thousands of patients each year. The major complications include pulmonary embolus with the potential for loss of life and post-thrombotic syndrome with the potential for loss of function of the limb. Extensive clinical research over the last 40 years has improved the techniques to remove the thrombus from the affected limb and reduce the likelihood of developing post-thrombotic syndrome. These treatments have included intravenous systemic thrombolysis, catheter-directed thrombolysis, surgical thrombectomy, and most recently pharmacomechanical thrombectomy to rapidly fragment, lyse, and remove the thrombus from the affected limb. This last technique may finally transform the treatment of acute deep vein thrombus from strictly conservative medical therapy to a minimally invasive procedure that can remove the thrombus to improve the quality of life of millions of individuals suffering from the symptoms of deep vein thrombosis. Mt Sinai J Med 77:286-295, 2010. (c) 2010 Mount Sinai School of Medicine.

Endovascular thrombolysis using monteplase for non-chronic deep venous thrombosis

This study was designed to evaluate the usefulness of endovascular thrombolysis using monteplase for deep venous thrombosis (DVT). Between December 2005 and October 2009, at our institution nine endovascular thrombolysis treatments with monteplase were performed for symptomatic DVT in eight patients (6 women, 2 men; mean age, 56 (range, 15-80) years). In all, systemic anticoagulation administered by the peripheral intravenous route with heparin and/or thrombolysis with urokinase followed by anticoagulation with orally administered warfarin had been performed, and subsequently six endovascular treatments without monteplase were administered. However, DVT persisted, and endovascular treatments with monteplase were tried. In six (67%) of the nine procedures, DVT completely or almost completely disappeared after endovascular thrombolysis with monteplase. Mean dose of monteplase used was 2,170,000 IU. There was only one procedure-related complication. In one patient, just after thrombolysis with monteplase, bleeding at the puncture site and gingival bleeding occurred. Bleeding was stopped by manual astriction only. Endovascular thrombolysis with monteplase may be an effective treatment for DVT, even in cases resistant to traditional systemic anticoagulation and thrombolysis and endovascular procedures without monteplase.

Noninvasive thrombolysis using pulsed ultrasound cavitation therapy - histotripsy

Clinically available thrombolysis techniques are limited by either slow reperfusion (drugs) or invasiveness (catheters) and carry significant risks of bleeding. In this study, the feasibility of using histotripsy as an efficient and noninvasive thrombolysis technique was investigated. Histotripsy fractionates soft tissue through controlled cavitation using focused, short, high-intensity ultrasound pulses. In vitro blood clots formed from fresh canine blood were treated by histotripsy. The treatment was applied using a focused 1-MHz transducer, with five-cycle pulses at a pulse repetition rate of 1kHz. Acoustic pressures varying from 2 to 12MPa peak negative pressure were tested. Our results show that histotripsy can perform effective thrombolysis with ultrasound energy alone. Histotripsy thrombolysis only occurred at peak negative pressure >or=6MPa when initiation of a cavitating bubble cloud was detected using acoustic backscatter monitoring. Blood clots weighing 330mg were completely broken down by histotripsy in 1.5 to 5min. The clot was fractionated to debris with >96% weight smaller than 5mum diameter. Histotripsy thrombolysis treatment remained effective under a fast, pulsating flow (a circulatory model) as well as in static saline. Additionally, we observed that fluid flow generated by a cavitation cloud can attract, trap and further break down clot fragments. This phenomenon may provide a noninvasive method to filter and eliminate hazardous emboli during thrombolysis.

Endovascular treatment for iliac vein compression syndrome: a comparison between the presence and absence of secondary thrombosis

Objective

To evaluate the value of early identification and endovascular treatment of iliac vein compression syndrome (IVCS), with or without deep vein thrombosis (DVT).

Materials and Methods

Three groups of patients, IVCS without DVT (group 1, n = 39), IVCS with fresh thrombosis (group 2, n = 52) and IVCS with non-fresh thrombosis (group 3, n = 34) were detected by Doppler ultrasonography, magnetic resonance venography, computed tomography or venography. The fresh venous thrombosis were treated by aspiration and thrombectomy, whereas the iliac vein compression per se were treated with a self-expandable stent. In cases with fresh thrombus, the inferior vena cava filter was inserted before the thrombosis suction, mechanical thrombus ablation, percutaneous transluminal angioplasty, stenting or transcatheter thrombolysis.

Results

Stenting was performed in 111 patients (38 of 39 group 1 patients and 73 of 86 group 2 or 3 patients). The stenting was tried in one of group 1 and in three of group 2 or 3 patients only to fail. The initial patency rates were 95% (group 1), 89% (group 2) and 65% (group 3), respectively and were significantly different (p = 0.001). Further, the six month patency rates were 93% (group 1), 83% (group 2) and 50% (group 3), respectively, and were similarly significantly different (p = 0.001). Both the initial and six month patency rates in the IVCS patients (without thrombosis or with fresh thrombosis), were significantly greater than the patency rates of IVCS patients with non-fresh thrombosis.

Conclusion

From the cases examined, the study suggests that endovascular treatment of IVCS, with or without thrombosis, is effective.

Midterm Follow-up After Pharmacomechanical Thrombolysis for Lower Extremity Deep Venous Thrombosis

Objective: To provide follow-up in patients treated with pharmacomechanical thrombolysis (PhMT) for lower extremity deep venous thrombosis (DVT). Methods: Retrospective analysis of prospectively collected data. Patients underwent clinical evaluation, duplex ultrasound, venous clinical severity scoring, venous segmental disease scoring, and venous disability scoring. Results: Fourteen patients were available for evaluation. Median age was 40 years (19—58). Median follow-up was 24 months (13—69 months). Thirteen of 14 patients (93%) had a venous disability score < 1 and 13 of 14 patients (93%) had a venous clinical severity scoring < 5. In all but 1 patient the venous segmental disease scoring score was < 5. All iliac segments were patent, all but 3 patients had partial infrainguinal obstruction and 5 of 14 (36%) had reflux. Conclusions: Our data demonstrate that the good early clinical results after PhMT can be sustained on longer follow-up and may prevent the development of advanced postthrombotic syndrome.

Rheolytic pharmacomechanical thrombectomy in experimental chronic deep vein thrombosis: effect of L-arginine on thrombogenicity and endothelial vasomotor function

PURPOSE

Endovascular removal of intravascular thrombus using the AngioJet rheolytic thrombectomy (RT) system has been shown to be clinically effective. This system also permits the concomitant infusion of thrombolytic agent followed by thrombectomy, thus creating a novel strategy known as pharmacomechanical thrombectomy (PMT). Although these interventions have gained wide clinical application, little is known regarding the vessel wall response following thrombectomy therapy. The aims of this study were to assess the effect of thrombectomy interventions on endothelial function in a porcine model of deep venous thrombosis (DVT) and to evaluate the effect of nitric oxide (NO) precursor L-arginine on endothelial function following thrombectomy therapy.

METHODS

Deep vein thrombosis was created in bilateral iliac veins by deploying a self-expanding stent-graft incorporating an intraluminal stenosis from a groin approach. Five pigs underwent sham operation. Following 14 days of DVT, animals were randomized to three groups: the first group received RT treatment (RT group, n = 5); the second group received pharmacomechanical thrombectomy (PMT) with tissue plasminogen activator (alteplase 10 mg; PMT group, n = 5); and the third group received PMT with tPA plus intravenous L-arginine (20 mmol/l) (arginine group, n = 5). Iliac vein patency was evaluated by venography and intravascular ultrasound at 1 week. Nitric oxide level was determined by a chemiluminescent assay of the nitrite/nitrate metabolites (NO(x)). Thrombogenicity was evaluated by radiolabeled platelet and fibrin deposition. Veins were harvested and evaluated with light microscopy and scanning electron microscopy (SEM). Endothelial function was evaluated using organ chamber analysis.

RESULTS

The luminal areas in the sham, RT, PMT, and arginine groups were 34 +/- 10 mm(2), 21 +/- 13 mm(2), 35 +/- 18 mm(2), and 37 +/- 16 mm(2), respectively. All iliac veins remained patent at 2 weeks. No difference in endothelial cell structure was observed between the three treatment groups by means of light microscopic or SEM examination. A decrease in platelet deposition occurred in the arginine group compared to the RT and PMT groups (P < 0.05). The arginine group also showed a greater endothelium-dependent relaxation compared to the RT or PMT groups in response to A23187, bradykinin, and ADP (P < 0.05). Local NO(x) level was higher in the arginine group than in the RT or PMT group (2.6 +/- 0.6 micromol/l versus 0.3 +/- 0.1 micromol/l and 0.3 +/- 0.2 micromol/l; P < 0.01).

CONCLUSIONS

AngioJet RT and PMT interventions resulted in similar attenuated endothelium-dependent vasoreactivity and morphologic effect. L-Arginine supplementation preserves endothelial vasoreactivity and reduces platelet deposition following PMT in iliac DVT. Additionally, L-arginine enhances NO production at sites of venous thrombosis. The NO precursor L-arginine may have a therapeutic potential in preserving endothelial function following mechanical thrombectomy.

Transpopliteal removal of an OptEase inferior vena cava filter after treatment of symptomatic filter thrombosis

PURPOSE

To describe a case of transpopliteal retrieval of an inferior vena cava (IVC) filter.

CASE REPORT

A paraplegic patient had an IVC filter placed for deep venous thrombosis (DVT) after anticoagulant therapy was stopped. Two weeks later, he developed massive scrotal and bilateral lower extremity swelling due to iliocaval thrombosis, which was treated by power pulse-spray thrombectomy and catheter-directed thrombolytic infusion via bilateral popliteal approaches. Following successful thrombus removal, the filter was uniquely retrieved via the right popliteal access; the patient was discharged on warfarin anticoagulation.

CONCLUSION

Transpopliteal IVC filter retrieval is feasible and may be a useful alternative technique in selected instances.

Ultrasound-enhanced Thrombolysis

PURPOSE

To report a single-center clinical experience with ultrasound-enhanced thrombolysis in the treatment of both arterial and venous thromboses.

METHODS

From January 2005 to June 2006, 33 patients (23 men; age range 39-90 years) with 36 occlusions were treated using ultrasound-enhanced thrombolytic therapy for acute and chronic arterial and venous occlusions. After diagnostic angiography, the occlusions were crossed with an appropriately sized Lysus infusion catheter for infusion of urokinase (80,000-120,000 IU/h).

RESULTS

Technical success and complete lysis was achieved in 96% of the arterial and 83% of the venous occlusions. Two patients with chronic occlusions (one superficial femoral artery and one iliac vein) were refractory to lytic therapy. Average time for complete lysis was 16.4 hours (range 3-25) for arterial occlusions and 21.2 hours (range 6-43) in patients with deep vein thrombosis.

CONCLUSION

Successful clot lysis can be achieved with a high rate of success in a shorter time than conventional thrombolysis using ultrasound-enhanced thrombolysis in both acute and chronic arterial and venous thromboses.