In vitro effectiveness of mechanical thrombectomy devices for large vessel diameter and low-pressure fluid dynamic applications

Construction and Validation of a Benchtop Model for Testing of Mechanical Thrombectomy Devices for Pulmonary Embolism

PURPOSE

This study aims to define the process of designing and manufacturing 3D printed and glass models of the pulmonary artery (PA) and utilizing them in a test bed for evaluation of devices for mechanical thrombectomy of pulmonary embolism (PE).

MATERIALS AND METHODS

Patient derived computed tomography angiography (CTA) images of the PA were digitally converted into a hollowed-out structure and translated into clear 3D printed and glass models. A test bed was created using a peristaltic pump and silicone tubing connected to the models. Human clot analogs were then prepared and injected within the models. Thrombectomy testing was done using clinically used predicates and baseline characteristics of the models were evaluated by independent interventionalists.

RESULTS

The mean sizes of the main pulmonary artery (MPA) for the 3D printed model and glass model were 30.4 mm and 29.2 mm, mimicking those of the patient's PA obtained on CTA. Heterogeneous human clot analogs were created with fibrin composition ranging from 60 to 30%. Mechanical thrombectomy was successfully attempted by independent interventionalists. Both the 3D printed, and glass model were appraised as very good for multiple attributes.

CONCLUSION

A complete test bed using 3D printed and glass models of the PA with human clot analogs was created for testing of mechanical thrombectomy devices for PE.

Comparison of Aspiration Catheters with Modified Standard Catheters for Treatment of Large Pulmonary Embolism Using an In-vitro Patho-Physiological Model

PURPOSE

The presented in-vitro study provides a comparison of various catheters for mechanical treatment of large-burden pulmonary embolism (PE) under standardized conditions, using a new test rig. Dedicated aspiration catheters (JETi®, Penumbra Indigo®, Aspirex®) were compared with standard catheters (Pigtail, Multi-Purpose, Balloon Catheter) applied for embolus fragmentation.

MATERIALS AND METHODS

Emboli prepared from porcine blood were washed into the test rig which consists of anatomical models of the pulmonary artery (PA) and of the right heart in combination with a pulsatile drive system. For all catheters, the duration of the recanalization procedure and the weight percentage (wt%) of the remaining, removed and washed-down clot fractions were evaluated. For aspiration catheters, the aspirated volume was measured.

RESULTS

All catheters achieved full or partial recanalization. The aspiration catheters showed a significantly (p < 0.05) lower procedure time (3:15 min ± 4:26 min) than the standard fragmentation catheters (7:19 min ± 4:40 min). The amount of thrombus removed by aspiration was significantly (p < 0.001) higher than that by fragmentation, averaging 86.1 wt% ± 15.6 wt% and 31.7 wt% ± 3.8 wt%, respectively. Nonetheless, most of the residue was fragmented into pieces of ≥ 1 mm and washed down. Only in 2 of 36 tests, a residual thrombus of 11.9 wt% ± 5.1 wt% remained in the central PA.

CONCLUSION

Comparison under standardized in-vitro patho-physiological conditions showed that embolus fragmentation with standard catheters is clearly inferior to aspiration with dedicated catheters in the treatment of large-burden PE, but can still achieve considerable success.

LEVEL OF EVIDENCE

No level of evidence, experimental study.

Safety Evaluation of a Forward-Viewing Intravascular Transducer for Sonothrombolysis: An in Vitro and ex Vivo Study

Recent in vitro work has revealed that a forward-viewing intravascular (FVI) transducer has sonothrombolysis applications. However, the safety of this device has yet to be evaluated. In this study, we evaluated the safety of this device in terms of tissue heating, vessel damage and particle debris size during sonothrombolysis using microbubbles or nanodroplets with tissue plasminogen activator, in both retracted and unretracted blood clots. The in vitro and ex vivo sonothrombolysis tests using FVI transducers revealed a temperature rise of less than 1°C, no vessel damage as assessed by histology and no downstream clot particles >500 µm. These in vitro and ex vivo results indicate that the FVI transducer poses minimal risk for sonothrombolysis applications and should be further evaluated in animal models.

Reduced clot debris size in sonothrombolysis assisted with phase-change nanodroplets

Thrombosis-related diseases such as stroke, deep vein thrombosis, and others represent leading causes of mortality and morbidity around the globe. Current clinical thrombolytic treatments are limited by either slow reperfusion (drugs) or invasiveness (catheters) and carry significant risks of bleeding. High intensity focused ultrasound (HIFU) has been demonstrated to be a non-pharmacological, non-invasive but yet efficient thrombolytic approach. However, clinical concerns still remain related to the clot debris produced via fragmentation of the original clot potentially being too large and hence occluding downstream vessels, causing hazardous emboli. In this study, we introduced phase-change nanodroplets into pulse HIFU-mediated thrombolysis. The size distribution of the clot debris generated in sonothrombolysis with and without nanodroplets was compared. The effects of nanodroplet concentration, acoustic power and pulse repetition frequency on the clot debris size were further evaluated. It was found that the volume percentage of the large clot debris particles (above 10 μm in diameter) was smaller and the average diameter of the clot debris reduced significantly in nanodroplets-assisted sonothrombolysis. The stable cavitation dose was higher in sonothrombolysis without nanodroplets but the inertial cavitation dose showed no significant differences under two conditions. Besides, the average diameter decreased with increasing nanodroplet concentration and acoustic power when calculated by number percentage, but was found to be similar when calculated by volume percentage. In addition, the number percentage of the clot debris above 30 μm was demonstrated to be larger upon applying a higher pulse repetition frequency. Taken in concert, this study demonstrated that the introduction of phase-change nanodroplets could provide a safer sonothrombolysis method by reducing the overall clot debris size.

Rheolytic thrombectomy in patients with massive and submassive acute pulmonary embolism

OBJECTIVES

To appraise the impact of AngioJet rheolytic thrombectomy (RT) on angiographic and clinical endpoints in patients with acute pulmonary embolism (PE).

BACKGROUND

The management of patients with acute PE and hemodynamic compromise, based mainly on anticoagulant and thrombolytic therapies, is challenging and still suboptimal in many patients. In such a setting, mechanical removal of thrombus from pulmonary circulation holds the promise of significant clinical benefits, albeit remains under debate.

METHODS

We retrospectively report on 51 patients referred to our catheterization laboratory and treated with AngioJet RT. Patients were classified according to the degree of hemodynamic compromise (shock, hypotension, and right ventricular dysfunction) to explore thoroughly the degree of angiographic pulmonary involvement (angiographic massive PE was defined as the presence of a Miller index >or= 17) and the impact on angiographic (obstruction, perfusion, and Miller indexes) and clinical (all-cause death, recurrence of PE, bleeding, renal failure, and severe thrombocytopenia) endpoints of AngioJet RT.

RESULTS

Angiographic massive PE was present in all patients with shock, whereas patients with right ventricular dysfunction and hypotension showed a similar substantial pulmonary vascular bed involvement. Technical success was obtained in 92.2% of patients, with a significant improvement in obstruction, perfusion and Miller indexes in each subgroup (all P < 0.0001). Four patients reported major bleedings and eight (15.7%) died in-hospital. Laboratory experience was significantly associated to a lower rate of major bleedings. All survivors were alive at long-term follow-up (35.5 +/- 21.7 months) except three who expired due to cancer and acute myocardial infarction.

CONCLUSIONS

In experienced hands AngioJet RT can be operated safely and effectively in most patients with acute PE, either massive or submassive, and substantial involvement of pulmonary vascular bed.

Early and long-term clinical results of AngioJet rheolytic thrombectomy in patients with acute pulmonary embolism

Anticoagulant and thrombolytic therapies are a mainstay in the management of acute pulmonary embolism (PE), especially when hemodynamic compromise is present. However, systemic drugs cannot achieve timely and effective treatment of acute PE in all patients. In such a setting, mechanical removal of thrombus from the pulmonary circulation holds the promise of significant clinical benefits, although it remains untested. We report early and long-term outcome of patients with massive or submassive acute PE treated with rheolytic thrombectomy by means of the 6Fr Xpeedior AngioJet device at our institution. Three main groups were defined pre hoc: subjects with severe (i.e., shock), moderate, or mild hemodynamic compromise. Technical and procedural successes, obstruction, perfusion and Miller indexes, and clinical events were appraised. In total 25 patients were treated with thrombectomy (8 in severe, 12 in moderate, and 5 in mild hemodynamic compromise). Technical and procedural successes were obtained in all patients, as confirmed by the significant improvement in obstruction, perfusion and Miller indexes overall, and in each subgroup (all p values <0.001). Improvement in obstruction, perfusion, and Miller indexes at the end of the procedure could also be confirmed in patients (n = 8) treated with local fibrinolysis and in the absence of concomitant thrombolysis (n = 17, p <0.05). Four patients died in hospital, all other patients but 1 were safely discharged after an appropriate hospital stay, and all were alive at long-term follow-up (median 61 months). In conclusion, this study supports at early and long-term follow-up the effectiveness and safety of rheolytic thrombectomy for PE.

A sequential approach to the management of a massive intracoronary thrombus in ST elevation myocardial infarction: a case report

Thrombus-laden coronary lesions present a particular challenge to the interventional cardiologist. Despite the development of multiple strategies to attack this problem, lesions with angio-graphically visible thrombus still carry a high risk of complications when coronary intervention is attempted. The authors present a case of acute inferior ST elevation myocardial infarction with a massive thrombus in an ectatic right coronary artery. Sequential treatment with intra-coronary glycoprotein IIb/IIIa inhibitor, rheolytic thrombectomy with 2 different-sized catheters, and transcatheter thrombus aspiration with a Pronto aspiration catheter was required to achieve a satisfactory result. This case illustrates the potential benefit of combining various mechanical strategies to treat intracoronary thrombus.

Bradyarrhythmias during use of the AngioJet system

The AngioJet system is an effective thrombectomy device, but it may cause chest discomfort and provoke bradyarrhythmias that range from mild bradycardia to asystole. The cause of AngioJet-induced bradyarrhythmia is unknown, although several hypotheses have attempted to explain the phenomenon. Herein several cases will be described, followed by a review of the relevant literature. The literature review suggests that the cause may be related to the effects of the hydrodynamic jets on stretch-activated receptors present on the vascular endothelium, and that pretreatment with gadolinium or streptomycin might prevent activation of these receptors.

Evaluation of a Newly Developed Percutaneous Thrombectomy Basket Device in Sheep With Central Pulmonary Embolisms

OBJECTIVE

The authors studied the development of a thrombectomy device that is adequately steerable and quickly placeable in case of extensive pulmonary embolism.

MATERIALS AND METHODS

The device consists of a self-expandable nitinol basket mounted at a catheter-tip, which allows suction and extraction of thrombus material. Five in vitro tests were performed followed by tests in 6 sheep. In vivo thrombus material was introduced through a jugular vein to produce pulmonary embolism. After catheter insertion over the right femoral vein, the basket was placed adjacent to the pulmonary embolus and the extraction procedure was performed.

RESULTS

In in vitro tests, the extracted thrombus amount varied between 60% and 95%. In animal experiments, the extracted amount varied between 30% and 95% as determined angiographically. Limiting factors were steerability and optimal positioning of the basket in relation to the embolus.

CONCLUSIONS

Extraction of pulmonary embolism with the self-expanding suction basket is feasible. However, successful recanalization is limited by catheter maneuverability in the pulmonary arterial system.

Catheter-Directed Thrombolysis with Percutaneous Rheolytic Thrombectomy Versus Thrombolysis Alone in Upper and Lower Extremity Deep Vein Thrombosis

PURPOSE

To compare the efficacy of catheter-directed thrombolysis (CDT) alone versus CDT with rheolytic percutaneous mechanical thrombectomy (PMT) for upper and lower extremity deep vein thrombosis (DVT).

METHODS

A retrospective cohort of consecutive patients with acute iliofemoral or brachiosubclavian DVT treated with urokinase CDT was identified, and a chart review was conducted. Demographic characteristics, treatment duration, total lytic dose, clot lysis rates and complications were compared in patients treated with urokinase CDT alone or combined CDT and rheolytic PMT.

RESULTS

Forty limbs in 36 patients were treated with urokinase CDT alone. Twenty-seven limbs in 21 patients were treated with urokinase CDT and rheolytic PMT. The mean treatment duration for urokinase CDT alone was 48.0 +/- 27.1 hr compared with 26.3 +/- 16.6 hr for urokinase CDT and rheolytic PMT (p = 0.0004). The mean urokinase dose required for CDT alone was 5.6 +/- 5.3 million units compared with 2.7 +/- 1.8 million units for urokinase CDT with rheolytic PMT (p = 0.008). Complete clot lysis was achieved in 73% (29/40) of DVT treated with urokinase CDT alone compared with 82% (22/27) treated with urokinase CDT with rheolytic PMT.

CONCLUSION

Percutaneous CDT with rheolytic PMT is as effective as CDT alone for acute proximal extremity DVT but requires significantly shorter treatment duration and lower lytic doses. Randomized studies to confirm the benefits of pharmacomechanical thrombolysis in the treatment of acute proximal extremity DVT are warranted.

Treatment of Acute Pulmonary Embolism: Local Effects of Three Hydrodynamic Thrombectomy Devices in an Ex Vivo Porcine Model

PURPOSE

To report an ex vivo study on the local effects of hydrodynamic thrombectomy for the treatment of acute pulmonary embolism (off-label use).

METHODS

Three devices (6-F AngioJet Xpeedior and 6-F and 8-F Oasis) were used for hydrodynamic thrombectomy inside the arteries of 24 inflated and perfused porcine lung explants. Each system was used at multiple positions inside 4 intact and 4 embolized lungs in vessels measuring 2 to 4 mm, 4 to 6 mm, 6 to 8 mm, and 8 to 10 mm. Angiograms prior to, during, and after catheter positioning and system operation were used to detect arterial wall trauma and to measure local clot removal per 30-second cycle. A total of 21 vessel wall samples were subjected to scanning electron microscopy (SEM) to evaluate non-perforating lesions.

RESULTS

All systems were able to remove clot material. The average recanalized vessel length normalized to 30 seconds for vessel diameters of 2 to 4 and 8 to 10 mm, respectively, was 1.17 and 1.75 cm (AngioJet), 0.97 and 0.25 cm (6-F Oasis), and 2.2 and 1.05 cm (8-F Oasis). Perforations occurred during positioning of the 6-F Oasis (4/78 maneuvers) and 8-F Oasis (13/60), but not the AngioJet (0/89); perforations were also seen during system operation (AngioJet: 21/89 activations, 6-F Oasis: 4/78, and 8-F Oasis: 9/60; all lesions inside vessels <6 mm in diameter). SEM showed 35 lesions, 14 with perforation (contrast extravasation) and 21 without perforation (induced by the tip of the guidewire).

CONCLUSION

The AngioJet was most efficient in clot removal, followed by the 8-F Oasis. The 6-F Oasis was least efficient, but had fewest complications. According to these experiments, the tested hydrodynamic thrombectomy devices may cause perforations in vessels <6 mm in diameter. Changes in catheter design to reduce system-specific complication rates or to improve the efficacy of clot removal are warranted.

Adjunctive Percutaneous Mechanical Thrombectomy for Lower-extremity Deep Vein Thrombosis: Clinical and Economic Outcomes

PURPOSE

To assess the clinical and economic benefits of catheter-directed thrombolysis (CDT) alone versus CDT with rheolytic percutaneous mechanical thrombectomy (PMT) for lower-extremity deep vein thrombosis (DVT).

MATERIALS AND METHODS

Consecutive patients with acute iliofemoral DVT treated with CDT with urokinase between 1997 and 2003 were identified. Demographic characteristics and clinical and economic outcomes were compared between patients treated with CDT alone versus CDT plus PMT.

RESULTS

Twenty-six limbs in 23 patients received CDT with urokinase, whereas 19 limbs in 14 patients were treated with CDT plus PMT. Mean treatment duration for CDT was 56.5 +/- 27.4 hours, compared with 30.3 +/- 17.8 hours for CDT plus PMT (P = .001). Mean urokinase dose for CDT was 6.70 +/- 5.9 million U compared with 2.95 +/- 1.82 million U for CDT plus PMT (P = .011). Urokinase CDT achieved complete clot lysis in 80.7% of limbs (n = 21) compared with 84.2% of limbs (n = 16) treated with CDT plus PMT (P = .764). The incidences of major bleeding (CDT, 7.7%; CDT plus PMT, 5.3%; P = .749) and pulmonary embolism (CDT, 3.8%; CDT plus PMT, 5.3%; P = .818) were similar. The mean urokinase and PMT device cost for CDT alone was $10,127 compared with $5,128 for CDT plus PMT (P = .026).

CONCLUSIONS

Percutaneous CDT with rheolytic PMT is as effective as CDT alone for acute iliofemoral DVT but requires significantly shorter treatment and lower lytic agent dose, resulting in lower costs. Randomized studies to confirm the benefits of pharmacomechanical thrombolysis in the treatment of DVT are warranted.

Mechanical thrombectomy of occluded hemodialysis native fistulas and grafts using a hydrodynamic thrombectomy catheter: preliminary experience

The purpose of this study was to evaluate the efficacy and safety of a new hydrodynamic percutaneous thrombectomy catheter in the treatment of thrombosed hemodialysis fistulas and grafts. Twenty-two patients (median age: 47 years; range: 31-79 years) underwent mechanical thrombectomy for thrombosed hemodialysis fistulas or polytetrafluoroethylene (PTFE) grafts. In all cases, an Oasis hydrodynamic catheter was used. Five patients had native fistulas and 17 had PTFE grafts. Six patients required repeat procedures. All patients with native fistulas and 15 of the 17 with PTFE grafts also underwent angioplasty of the venous limb following the thrombectomy. Major outcome measures included technical success, clinical success, primary and secondary patency, and complication rates. Twenty-eight procedures were performed in total. The technical success rate was 100% and 90% and clinical success was 86% and 76% for native fistulas and grafts, respectively. The primary patency at 6 months was 50% and 59% for fistulas and grafts, respectively, and the secondary patency at 6 months was 75% and 70% for fistulas and grafts, respectively. Two patients died of unrelated causes during the follow-up period. The Oasis catheter is an effective mechanical device for the percutaneous treatment of thrombosed hemodialysis access. Our initial success rate showed that the technique is safe in the treatment of both native fistulas and grafts.

AngioJet rheolytic thrombectomy versus local intrapulmonary thrombolysis in massive pulmonary embolism: a retrospective data analysis

PURPOSE

To compare the efficacy of full-dose local intrapulmonary thrombolysis (LIT) versus AngioJet rheolytic thrombectomy (ART) in the treatment of massive pulmonary embolism.

METHODS

A retrospective review was conducted of 8 consecutive patients (5 women; mean age 66.0+/-5.9 years, range 56-74) who underwent LIT with high-dose intrapulmonary urokinase (4400 IU/kg over 10 minutes followed by a 2000-IU/kg/h infusion) and a subsequent 6 consecutive patients (4 men; mean age of 59.2+/-17.0 years, range 26-69) who underwent ART plus adjunctive low-dose urokinase infusions (100,000 IU) until hemodynamic recovery was achieved. Pre and postprocedural Miller scores were calculated, and relative Miller score improvement, total urokinase doses, and duration of therapy were compared.

RESULTS

Hemodynamic stability was restored in all 8 LIT patients and in 5 (83%) of the 6 ART patients; 1 (16.7%) patient died during the ART procedure due to recurrent MPE. In the LIT group, the mean Miller score prior to intervention was 17.38+/-2.67, which was reduced to 6.13+/-1.46 after the intervention (p<0.0001) compared to scores of 18.83+/-2.86 and 6.83+/-2.79, respectively, in the ART group (p<0.0001). The mean urokinase dose was 2.07+/-0.44 million IU in the LIT group versus 0.70+/-0.36 million IU in the ART group (p<0.0001). The mean duration of therapy was 11.45+/-2.94 hours in the LIT group versus 3.37+/-1.41 hours in the ART group (p<0.0001). No significant difference in relative Miller score improvement was observed.

CONCLUSION

By accelerating the fragmentation of thrombus, ART plus adjunctive low-dose urokinase seems to be more rapidly effective compared to LIT. ART achieves both rapid cardiovascular relief and reduces the dose of thrombolytic agent necessary in patients with massive pulmonary embolism.

Thrombolysis and mechanical thrombectomy for arterial disease

Thrombolytic therapy has been around for close to 30 years now,but its exact role in the treatment of acute and chronic arterial occlusive disease continues to be debated. Studies have produced varying and contradictory results. We are still not sure if thrombolysis has any true advantages over surgical thromboembolectomy,or which lytic agent is the best. Nonetheless, the technique still plays an important role in the treatment of arterial occlusions.

Mechanical thrombectomy for DVT

Deep venous thrombosis is a common source of morbidity and mortality in the United States. Complications include pulmonary embolism and chronic post-thrombotic syndrome. Chronic post-thrombotic syndrome is characterized by extremity pain, edema, venous claudication, skin changes, and skin ulceration. This syndrome is attributed to venous obstruction and valvular damage due to thrombus. The standard treatment of deep venous thrombosis consists of medical management with anticoagulation. Anticoagulation has proven efficacy in prevention of thrombus extension, pulmonary embolus, and re-thrombosis. The role of anticoagulation in post-thrombotic syndrome is unclear. Aggressive endovascular techniques for managing DVT have evolved as a result. Catheter-directed thrombolysis was the first such procedure with demonstrated efficacy, however its acceptance has been limited by perceived risks, time to lysis, and cost. As a result, alternative measures for managing DVT have evolved including mechanical thrombectomy. Mechanical thrombectomy for DVT has the potential to shorten the time for lysis, reduce the risk of thrombolytic agents, and potentially impact cost savings.