Preclinical in vivo testing of the Arrow-Trerotola percutaneous thrombolytic device for venous thrombosis

Critical Review of Large Animal Models for Central Deep Venous Thrombosis

OBJECTIVE

To review the existing literature on large animal models of central venous thrombosis (CVT) and to evaluate its relevance in regard to the development and testing of dedicated therapeutics applicable to humans.

METHODS

A systematic literature search was conducted in PubMed and Embase. Articles describing an in vivo experimental protocol of CVT in large animals, involving the iliac vein and/or the vena cava and/or the brachiocephalic vein, were included. The primary aim of the study, animal characteristics, experimental protocol, and thrombus evaluation were recorded.

RESULTS

Thirty-eight papers describing more than 30 different protocols were included. Animals used were pigs (53%), dogs (21%), monkeys (24%), and cattle (3%). The median number of animals per study was 12. Animal sex, strain, and weight were missing in 18 studies (47%), seven studies (18%), and eight studies (21%), respectively. CVT was always induced by venous stasis: solely (55%), or in addition to hypercoagulability (37%) or endothelial damage (10%). The size of the vessel used for thrombus creation was measured in four studies (10%). Unexpected animal death occurred in nine studies (24%), ranging from 3% to 37% of the animals. Twenty-two studies (58%) in the acute phase and 31 studies in the chronic phase (82%) evaluated the presence or absence of the thrombus created, and its occlusive characteristic was reported, respectively, in five and 17 studies. Histological examination was performed in 24 studies (63%) with comparison to human thrombus in one study.

CONCLUSION

This review showed advantages and weaknesses of the existing large animal models of CVT. Future models should insist on more rigour and consistency in reporting animal characteristics, as well as evaluating and comparing the thrombus created to human thrombus.

The radiological management of the thrombosed arteriovenous dialysis fistula

Patent vascular access is a prerequisite for adequate haemodialysis, and is a major determinant of quality of life and long-term survival of patients with end-stage renal disease. Autogenous haemodialysis fistulas (AVFs) have demonstrated superior clinical outcome when compared to synthetic grafts, but both types of access remain susceptible to venous stenoses, and consequent thrombotic occlusion. Recent publications have reported primary patency rates of up to 100% following percutaneous de-clotting of AVFs incorporating techniques such as pharmacological thrombolysis, mechanical thrombectomy, and thrombo-aspiration. Endovascular management also provides information regarding the underlying cause of access thrombosis, with option to treat. Consequently, there has been a paradigm shift in the management of fistula thrombosis, with interventional radiology assuming a lead role in initial salvage procedures. This article will attempt to provide the reader with an insight into the multiple radiological techniques that can be employed to salvage a thrombosed AVF based on current published literature.

Comparison of percutaneous ultrasound-accelerated thrombolysis versus catheter-directed thrombolysis in patients with acute massive pulmonary embolism

Acute massive pulmonary embolism (PE) is a life-threatening condition that requires prompt and aggressive interventions, including anticoagulation, catheter-directed thrombolysis (CDT), mechanical thrombectomy, or surgical thromboembolectomy. The aim of this study was to evaluate the treatment outcome in patients with massive PE who were treated with either ultrasound-accelerated thrombolysis using the EkoSonic Endovascular System (EKOS) or CDT intervention. During a recent 10-year period, the clinical records of all patients with massive PE undergoing catheter-directed interventions were evaluated. Patients were divided into two treatment groups: EKOS versus CDT interventions. Comparisons were made with regard to the treatment outcome between the two groups. Twenty-five patients underwent 33 catheter-directed interventions for massive PE during the study period. Among them, EKOS or CDT was performed in 15 (45%) and 18 (55%) procedures, respectively. In the EKOS group, complete thrombus removal was achieved in 100% cases. In the CDT cohort, complete or partial thrombus removal was accomplished in 7 (50%) and 2 (14%) cases, respectively. Comparing treatment success based on thrombus removal, EKOS treatment resulted in an improved treatment outcome compared with the CDT group (p < .02). The mean time of thrombolysis in EKOS and CDT group was 17.4 +/- 5.23 and 25.3 +/- 7.35 hours, respectively (p = .03). The mortality rate in the EKOS and CDT group was 9.1% and 14.2%, respectively (not significant). Treatment-related hemorrhagic complication rates in the EKOS and CDT group were 0% and 21.4%, respectively (p = .02). A significant reduction in Miller scores was noted in both groups following catheter-based interventions. No significant difference in relative Miller score improvement was observed between groups. Ultrasound-accelerated thrombolysis using the EkoSonic system is an effective treatment modality in patients with acute massive PE. When compared with CDT, this treatment modality provides similar treatment efficacy with reduced thrombolytic infusion time and treatment-related complications.

In vivo veritas: Thrombosis mechanisms in animal models

Experimental models have enhanced our understanding of atherothrombosis pathophysiology and have played a major role in the search for adequate therapeutic interventions. Various animal models have been developed to simulate thrombosis and to study in vivo parameters related to hemodynamics and rheology that lead to thrombogenesis. Although no model completely mimics the human condition, much can be learned from existing models about specific biologic processes in disease causation and therapeutic intervention. In general, large animals such as pigs and monkeys have been better suited to study atherosclerosis and arterial and venous thrombosis than smaller species such as rats, rabbits, and dogs. On the other hand, mouse models of arterial and venous thrombosis have attracted increasing interest over the past two decades, owing to direct availability of a growing number of genetically modified mice, improved technical feasibility, standardization of new models of local thrombosis, and low maintenance costs. To simulate rupture of an atherosclerotic plaque, models of arterial thrombosis often involve vascular injury, which can be achieved by several means. There is no animal model that is sufficiently tall, that can mimic the ability of humans to walk upright, and that possesses the calf muscle pump that plays an important role in human venous hemodynamics. A number of spontaneous or genetically engineered animals with overexpression or deletion of various elements in the coagulation, platelet, and fibrinolysis pathways are now available. These animal models can replicate important aspects of thrombosis in humans, and provide a valuable resource in the development of novel concepts of disease mechanisms in human patients.

Catheter-directed thrombolysis with the Endowave system in the treatment of acute massive pulmonary embolism: a retrospective multicenter case series

PURPOSE

To evaluate the efficacy of thrombolysis with the EndoWave peripheral infusion system in the treatment of patients with massive pulmonary embolism (PE) as compared to patients treated with catheter-directed thrombolysis.

MATERIALS AND METHODS

Ten patients (five men and five women; age range, 31-85 years; mean age, 54.20 years) with massive acute PE (17 lesions) were treated with ultrasonography (US)-assisted catheter-directed thrombolysis with the Endowave system. All patients had hypoxia and dyspnea. No patient had contraindication for thrombolysis. Angiographic findings, duration of lysis, dose of thrombolytics used, and procedural complications were recorded. Thrombolytics used were urokinase, tissue-type plasminogen activator (tPA), and Reteplase.

RESULTS

Complete thrombus removal was achieved in 13 of the 17 lesions (76%), near complete thrombolysis was achieved in three lesions (18%), and partial thrombolysis was achieved in one lesion (6%). The mean time of thrombolysis was 24.76 hours +/- 8.44 (median, 24 hours). The mean dose of tPA used for the Endowave group was 0.88 mg/h +/- 0.19 (13 lesions).

CONCLUSIONS

US-assisted catheter-directed thrombolysis is an effective method for treating massive thrombolysis. It has the potential to shorten the time of lysis and lower the dose of thrombolytics.

Use of the Arrow Percutaneous Thrombectomy Device and Transjugular Liver Biopsy Cannula for Mechanical Thrombectomy of the Inferior Vena Cava in a Patient with Budd-Chiari Syndrome

A 33-year-old woman with Budd-Chiari syndrome and hypercoagulability was sequentially treated with the placement of hepatic vein stents and transjugular intrahepatic portosystemic shunts (TIPS), all of which repeatedly thrombosed. Four months after TIPS revision with an endoprosthesis, a large inferior vena cava (IVC) thrombus developed caudal to an IVC stenosis. A percutaneous thrombectomy device was introduced coaxially through a transjugular liver biopsy cannula to extend its effective diameter range of attack and was steered within the IVC to successfully clear the thrombus. The condition recurred 9 months later, and the technique was repeated successfully. At subsequent 12-month follow-up, the IVC remains patient and symptoms resolved. This combination of cannula and percutaneous thrombectomy device proved essential in facilitating successful mechanical thrombectomy of the IVC.

Mechanical Thrombectomy of Acute Iliofemoral Deep Vein Thrombosis with Use of an Arrow-Trerotola Percutaneous Thrombectomy Device

PURPOSE

To evaluate the immediate and 1-year clinical outcomes of mechanical thrombectomy with use of the Arrow-Trerotola percutaneous thrombectomy device (PTD) with or without low-dose urokinase in the treatment of acute iliofemoral deep vein thrombosis (DVT).

MATERIALS AND METHODS

Mechanical thrombectomy with the PTD was performed in 25 patients with acute iliofemoral DVT. Thrombolytic therapy with low-dose urokinase was used in all patients without contraindications (n = 20). Other therapies used in combination included inferior vena cava filter insertion (n = 5), sheath aspiration thrombectomy (n = 25), and angioplasty and stent placement (n = 20).

RESULTS

Initial technical and clinical success was achieved in all cases. In the 20 patients who had no contraindications to the use of urokinase, the dosage of urokinase did not exceed 1 million IU (range, 360,000-1,000,000 IU; mean, 640,000 IU). The mean time of urokinase infusion was 16 hours (range, 12-20). In five patients who had a contraindication to the use of urokinase, mechanical thrombectomy with the PTD was successful without the use of urokinase. There were no major complications. Primary patency of the stent-implanted common iliac vein segment was achieved at 1 year in 17 of 20 patients (85%). The overall 1-year clinical success rate was 92% (23 of 25 patients). Valvular insufficiency occurred in two patients (8%).

CONCLUSION

The PTD is an effective mechanical thrombectomy device in the treatment of acute iliofemoral DVT with or without adjunctive urokinase thrombolysis.

Vascular injury caused by mechanical thrombectomy in porcine arteries: AKónya eliminator device versus Arrow-Trerotola percutaneous thrombolytic device

PURPOSE

To compare vascular injuries induced by a nonrotational thrombectomy device equipped with an adjustable basket (the AKónya Eliminator [AKE] device) and the Arrow-Trerotola percutaneous thrombolytic device (PTD) in porcine external iliac arteries (EIAs).

MATERIALS AND METHODS

The EIAs of nine domestic pigs underwent simulated thrombectomy with the AKE after the diameter of the basket had been adjusted to the vessel's diameter and with the PTD after motor activation. Three animals were euthanized immediately after treatment (group 1, acute), three after 1 week (group 2, subchronic), and three after 6 weeks (group 3, chronic). Vessel diameters were measured angiographically at four anatomic locations at the three time points. A histologic grading system was established to quantify the degree of vascular injury and lumen compromise. Four other EIAs were treated with an "oversized" AKE basket and followed for 6 weeks.

RESULTS

Histologically, the acute lesions in the AKE-treated vessels were more superficial than those in the PTD-treated vessels. In group 2, two of three PTD-treated arteries occluded, and their subchronic injuries were more serious than those in the AKE-treated arteries. In group 3, all AKE-treated arteries remained patent, but one of the PTD-treated vessels occluded, and the lumen sizes of the PTD- and AKE-treated arteries differed significantly. After 6 weeks, there was no significant difference between arteries treated with the PTD and those treated with the oversized AKE in terms of diameter or histologic grading.

CONCLUSIONS

The adjustable basket and hand-controlled operation of the AKE were significantly less injurious to the arterial wall than the constant-size PTD basket operated at 3,000 rpm. Damage produced by the oversized AKE basket was similar to that produced by the PTD.

The Case for Thrombolysis for Iliofemoral Venous Thrombosis

Deep venous thrombosis and its consequences remain a significant clinical challenge despite advances in the current healthcare system. The use of thrombolytic therapy has played an important role in the management of both arterial and venous thrombotic conditions. In this article, relevant clinical evidence and rationale in support of thrombolytic therapy in ileofemoral deep venous thrombosis are discussed.

Percutaneous Venous Thrombectomy Using the Arrow-Trerotola Percutaneous Thrombolytic Device (PTD) with Temporary Caval Filtration: In Vitro Investigations

PURPOSE

To evaluate the size and quantity of downstream emboli after thrombectomy using the Arrow-Trerotola Percutaneous Thrombolytic Device (PTD) with or without temporary filtration for extensive iliofemoral and iliocaval thrombi in an in vitro flow model.

METHODS

Iliocaval thrombi were simulated by clotted bovine blood in a flow model (semilucent silicone tubings, diameter 12-16 mm). Five experimental set-ups were performed 10 times each; thrombus particles and distribution were measured in the effluent. First, after retrograde insertion, mechanical thrombectomy was performed using the PTD alone. Then a modified self-expanding tulip-shaped temporary vena cava stent filter was inserted additionally at the beginning of each declotting procedure and removed immediately after the intervention without any manipulation within or at the filter itself. In a third step, the filter was filled with thrombus only. Here, two experiments were performed: Careful closure within the flow circuit without any additional fragmentation procedure and running the PTD within the filter lumen, respectively. In the final set-up, mechanical thrombectomy was performed within the thrombus-filled tubing as well as in the filter lumen. The latter was closed at the end of the procedure and both devices were removed from the flow circuit.

RESULTS

Running the PTD in the flow circuit without filter protection led to a fragmentation of 67.9% (+/-7.14%) of the clot into particles < or =500 microm; restoration of flow was established in all cases. Additional placement of the filter safely allowed maceration of 82.9% (+/-5.59%) of the thrombus. Controlled closure of the thrombus-filled filter within the flow circuit without additional mechanical treatment broke up 75.2% (+/-10.49%), while additional mechanical thrombectomy by running the PTD within the occluded filter led to dissolution of 90.4% (+/-3.99%) of the initial clot. In the final set-up, an overall fragmentation rate of 99.6% (+/-0.44%) was achieved.

CONCLUSIONS

The combined use of the Arrow-Trerotola PTD and a temporary vena cava stent filter proved to be effective for even large clot removal in this experimental set-up.

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.

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

Acute complications of deep vein thrombosis (DVT) of the lower extremities include pulmonary embolism and venous ischemia. Delayed complications include a spectrum of debilitating symptoms referred to as postthrombotic syndrome (PST). Anticoagulation therapy is recognized as the mainstay of therapy in acute DVT. However, there are few data to suggest any major beneficial effect on PTS, which is thought to be mediated by valve damage and/or occlusive chronic thrombus and venous scarring. Endovascular catheter-directed thrombolysis techniques with pharmacologic thrombolytic agents, used alone or in combination with mechanical thrombectomy devices, have been proven highly effective in clearing acute DVT, which may allow the preservation of venous valve function and prevention of subsequent venous occlusive disease. Definitive management of underlying anatomic occlusive abnormalities can also be undertaken.

Validation of US-guided percutaneous venous access and manual compression for studies in swine

PURPOSE

To validate, in swine, the feasibility, efficacy, and safety of ultrasound (US)-guided vascular access, with manual compression for hemostasis, as an alternative to surgical cutdown.

MATERIALS AND METHODS

US-guided femoral vein access was attempted 22 times in eight pigs. Bilateral access was performed in the initial procedure (eight pigs, 16 veins), and unilateral access was performed during follow-up procedures (six pigs, six veins). Two sheath sizes were used: 9 F (in eight veins) and 8 F (in 14 veins). At the completion of each procedure, the vascular sheaths were removed and hemostasis was attempted by manual compression. All animals were followed clinically for at least 24 hours after each access procedure. Bilateral US images of the femoral region were obtained in six pigs (12 puncture sites) 2 weeks after the initial procedure.

RESULTS

US-guided femoral vein access was successful in all 22 attempts, including 16 first-time insertions and six subsequent insertions. Hemostasis was achieved with 5 minutes of manual compression in all 22 procedures. No groin complications were identified on clinical follow-up or at necropsy. US imaging of the 12 femoral access points in the six pigs that underwent more than one procedure demonstrated normal femoral veins that compressed appropriately with no evidence of thrombosis or hematoma.

CONCLUSION

US-guided femoral vein access, with manual compression used for hemostasis, is a safe and effective method for venous interventions in swine. Moreover, this percutaneous technique allows the same vessel to be reused.

Mechanical thrombolysis of venous thrombosis in an animal model with use of temporary caval filtration

PURPOSE

To test the effect of temporary caval filtration on pulmonary emboli when a mechanical thrombolytic device is used to treat venous thrombosis and to test the effects of a modified device on caval patency at 30-day follow-up.

MATERIALS AND METHODS

In a canine model of iliocaval subacute thrombosis, mechanical thrombolysis was performed with use of an 8-F over-the-wire Arrow-Trerotola Percutaneous Thrombolytic Device (PTD) with a 9-mm (iliac) or 15-mm (inferior vena cava [IVC]) basket. In six procedures, the device was made of nitinol monofilament, and in another six, it was made of braided stainless steel. All procedures were performed with a nitinol expandable sheath (temporary filter) in the suprarenal IVC. Low-molecular-weight heparin was given daily after the procedure. Venography, pulmonary arteriography, measurement of blood gases, and pulmonary artery (PA) pressure measurement were performed before and after the procedure and at 30-day follow-up. Pulmonary arteriograms from the group treated with stainless-steel devices were compared to those from an earlier group of animals in which the identical procedure was performed without caval filtration. The IVC was examined histologically.

RESULTS

Thrombolysis was successful in all animals. Rare segmental and subsegmental pulmonary emboli (PE) were seen arteriographically; compared to procedures without filters, there was a significant reduction in PE (P <.002). However, a mild increase in pulmonary artery pressure, decrease in pH, and increase in pCO(2) were observed postprocedurally. At 30-day follow-up (n = 11), IVC patency was preserved in 45% (n = 5) of animals overall. Caval patency was significantly better in animals in which the combination of stainless-steel devices was used (five of six = 83% vs zero with nitinol device; P =.015). Histologically, the stainless-steel device caused little intimal injury and fibrosis-less than that seen with the nitinol device.

CONCLUSIONS

Temporary filtration reduces, but does not completely eliminate, PE during mechanical thrombolysis. The stainless-steel device results in less intimal injury and better caval patency than the nitinol device.