Experimental impeller fragmentation of iliocaval thrombosis under tulip filter protection: preliminary results

Treatment of Inferior Vena Cava Filter Thrombosis by Mechanical Thrombectomy and Temporary Vena Cava Filter Protection

Inferior vena cava (IVC) filter thrombosis presents a difficult management problem and is associated with a significant incidence of pulmonary embolism. Treatment options in less extensive clots include anticoagulant or thrombolytic therapy, often in combination with placement of a filter above the clot. However, propagation of the clot to the level of the right atrium or the existence of a free-floating thrombus and continued pulmonary embolism may require surgical intervention including vena caval ligation and thrombec tomy. A thrombus that extends to the right atrium may also require thoracotomy and cardiopulmonary bypass. Contraindications to anticoagulant or thrombolytic therapy, as in our patient with a significant bleeding risk from a colon carcinoma and heme-positive stools, further complicate treatment decisions. The authors report the first successful treatment of an IVC filter thrombosis using the combination of mechanical thrombec tomy and temporary vena cava filter protection.

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.

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.

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.

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

PURPOSE

To test the safety and efficacy of using the Arrow-Trerotola percutaneous thrombolytic device (PTD) for treating deep vein thrombosis (DVT) in an animal model.

MATERIALS AND METHODS

An established canine model of iliocaval subacute thrombosis was used. Thrombosis was caused by balloon occlusion of the infrarenal inferior vena cava (IVC) for 7 (n = 12), 10 (n = 1), or 17 (n = 1) days. Treatment was performed with use of an 8-F, over-the-wire (0.035-inch) PTD with a 15-mm-diameter basket. The procedure was performed without IVC filtration. Two acute procedures were performed and 12 procedures were intended as survival procedures with 30-day follow-up. Pulmonary arteriography, blood gases, and pulmonary artery pressure measurement were performed before and after the procedure, and at follow-up. The animals were killed after the follow-up procedure and their IVC, iliac veins, and lungs were removed and examined histologically. Heparin was used intraprocedurally but thrombolytic agents were not used. Low-molecular-weight heparin was given daily after the procedure.

RESULTS

Thrombolysis was completely (12 of 13) or partially (one of 13) successful in all animals in the 7- and 10-day groups, but was unsuccessful in the animal in the 17-day group (n = 1). Variable amounts of segmental and subsegmental pulmonary emboli were found in all animals with small increases in pulmonary artery pressure. Two animals died within 6 days of the procedure, possibly due to pulmonary emboli. At 30-day follow-up, IVC patency was preserved in 80% (eight of 10) of animals, but significant caval narrowing due to intimal hyperplasia was noted at follow-up. All pulmonary emboli had resolved angiographically at follow-up, but evidence of recanalized or resolving pulmonary thromboemboli was found in seven of the 12 surviving animals. No acute vascular injury (eg, perforation) occurred.

CONCLUSION

The modified PTD used in this study is effective in treating subacute (<7 days old) venous thrombosis, but temporary filtration will probably be necessary to keep pulmonary emboli to a minimum during the procedure. The 30-day patency is encouraging. The results in this animal model indicate that the Arrow-Trerotola PTD may be useful in the percutaneous treatment of DVT in humans.

Mechanical thrombectomy in patients with deep venous thrombosis

PURPOSE

To report our experience with mechanical thrombectomy in proximal deep vein thrombosis (DVT).

METHODS

Eighteen patients with a mean (+/- SD) age of 37.6 +/- 16.1 years who presented with DVT in the iliac and femoral vein (n = 3), inferior vena cava (n = 5), or inferior vena cava and iliac vein (n = 10), were treated with the Amplatz Thrombectomy Device after insertion of a temporary caval filter.

RESULTS

Successful recanalization was achieved in 15 of 18 patients (83%). Overall, the percentage of thrombus removed was 66 +/- 29%: 73 +/- 30% at caval level and 55 +/- 36% at iliofemoral level. Complementary interventions (seven patients) were balloon angioplasty (n = 2), angioplasty and stenting (n = 2), thrombo-aspiration alone (n = 1), thrombo-aspiration, balloon angioplasty, and permanent filter (n = 1), and permanent filter alone (n = 1). There was one in-hospital death. Follow-up was obtained at a mean of 29.6 months; three patients had died (two cancers, one myocardial infarction); 10 had no or minimal sequelae; one had post-phlebitic limb.

CONCLUSION

Mechanical thrombectomy is a potential therapeutic option in patients presenting with proximal DVT.

Percutaneous venous thrombectomy with the use of a balloon sheath: first in vitro investigations of a new low-tech concept

RATIONALE AND OBJECTIVES

To test mechanical thrombectomy of extensive iliofemoral and iliocaval thrombi in an in vitro flow model with the use of 12F and 18F balloon sheaths.

METHODS

Newly developed 12F and 18F sheaths were evaluated in four vessel models (simulation of femoral, iliofemoral, iliocaval, and caval thrombi by clotted bovine blood in a flow model). After retrograde insertion of the sheath and blocking of the vessel proximal to the thrombus by inflating the balloon, mechanical fragmentation was performed coaxially through the sheath lumen by using a 7F pigtail rotation device. With an occlusion balloon catheter, residual thrombi were withdrawn to the orifice of the sheath and aspirated. Twelve silicone tubes occluded by thrombi were recanalized in each setting. In the latex model, seven recanalizations were performed.

RESULTS

All clots were removed completely within a treatment duration of 2 to 14 minutes. Fluid loss during the procedure was 29.6 to 129.3 mL for the femoral flow model, 61.9 to 137.2 mL for the iliofemoral model, 74.5 to 163.4 mL for the iliocaval model, and 102.7 to 236.7 mL for the caval model. No fragments were washed downstream. In four settings, small residual thrombi were attached to the balloon after deflation of the sheath.

CONCLUSIONS

Clot amounts up to 171 g were removed quickly and completely by using these large-caliber balloon sheaths. Fluid loss from aspiration was negligible. Balloon occlusion prevented embolization of thrombus fragments proximal to the sheath. Further studies are needed to prove the efficacy of this technique in vivo.

Acute and delayed outcomes of mechanical thrombectomy with use of the steerable Amplatz thrombectomy device in a model of subacute inferior vena cava thrombosis

PURPOSE

To study the efficacy and delayed outcome of mechanical thrombectomy with the Amplatz thrombectomy device (ATD) in an experimental model of subacute inferior vena cava (IVC) thrombosis.

MATERIALS AND METHODS

Mechanical thrombectomy was performed in 23 dogs with subacute infrarenal IVC thrombosis (6-15 days old). Heparin was administered during thrombectomy in all procedures (activated clotting time > or = 300 sec). Thirteen animals were killed immediately after thrombectomy, and the remaining 10 were allowed to survive for up to 1 month with no anticoagulation therapy.

RESULTS

Venographic patency of the IVC was restored in all animals, although residual mural thrombus remained in nine dogs (< 20% narrowing in seven, 20%-30% narrowing in two). No histopathologic evidence of mechanical wall disruption attributed to mechanical thrombectomy was seen. However, foci of organizing residual thrombus with associated transmural phlebitic changes with round-cellular infiltration were present in all acute specimens, including those appearing clear at venography. Venography at 1 week or 1 month after thrombectomy showed IVC rethrombosis in eight dogs (80%) who were not receiving anticoagulants. During mechanical thrombectomy, a small increase in mean pulmonary artery pressure occurred, with a corresponding decrease in systemic arterial oxygen saturation. No acute emboli were noted on the post-thrombectomy pulmonary angiograms. However, histopathologic examination of acutely explanted lungs in 11 animals showed arteriolar microemboli (100-500 microm) in four.

CONCLUSION

Mechanical thrombectomy with use of the ATD can effectively clear subacute IVC thrombus. However, rethrombosis is common and may be due to the high prevalence of phlebitis and residual thrombus. Anticoagulation may need to be continued after successful thrombectomy to prevent progression of residual thrombus and allow mural phlebitic changes to subside.