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

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.

How thrombus model impacts the in vitro study of interventional thrombectomy procedures

RATIONALE AND OBJECTIVES

Numerous experimental models are used to investigate the effectiveness of thrombectomy devices. We aimed to study the systematic effects of different in vitro thrombus models on the results of experimental thrombectomy and examined how thrombi formed in vitro and ex vivo differ.

METHODS

Three variables involved in human in vitro thrombogenesis were investigated: spontaneous or thrombin-induced clotting, age (1 or 5 days old), and storage temperature (4 degrees C or 21 degrees C). The fibrin content of in vitro and fresh or old ex vivo thrombi was measured by histologic studies. Ten experiments were performed with each of 8 different in vitro thrombus types using (1) ultrasound thrombolysis, (2) Oasis thrombectomy, (3) Amplatz thrombectomy, and (4) Straub-Rotarex catheters. Thrombus weight was measured after standardized treatment.

RESULTS

The fibrin content was markedly lower in all in vitro than in fresh and old ex vivo thrombi. In vitro thrombus type had no impact on the effectiveness of ultrasound thrombolysis and Amplatz thrombectomy. Thrombogenesis type affected Oasis and Straub-Rotarex catheter use. Storage temperature had a systematic impact on the outcome of Oasis thrombectomies.

CONCLUSION

The fibrin content of in vitro thrombi differs substantially from that of fresh and old ex vivo human thrombi. Experimental conditions may systematically impact experimental evaluation of thrombectomy procedures. In vitro thrombi with thrombin-induced thrombogenesis should be favored for use in thrombectomy experiments.

Invasive approaches to treatment of venous thromboembolism

Deep vein thrombosis (DVT) occurs in one-quarter of a million individuals annually in the United States and results in significant disability from pulmonary embolism and chronic venous insufficiency, especially when the proximal iliofemoral is involved. Treatment has centered on early institution of adequate anticoagulation to prevent thrombus propagation and embolism, but anticoagulation alone does not always restore venous patency and many patients are left with venous outflow obstruction and valvular incompetence-the anatomic underpinnings of the postthrombotic syndrome. Various strategies have been used to restore patency of thrombosed veins, including open surgical thrombectomy, pharmacological thrombolysis, and percutaneous mechanical thrombectomy. Each modality has benefits and shortcomings. Surgical thrombectomy had previously been abandoned secondary to poor long-term results. More recently, with improved techniques and better patient selection, surgical thrombectomy has regained a therapeutic role in treating acute DVT in young patients with short segment occlusions. The advent of percutaneous techniques has allowed thrombolysis, percutaneous mechanical thrombectomy, and stenting to be used in conjunction with each other-allowing for better resolution of venous clot burden than when an individual modality is used alone. Practitioners who treat patients with DVT should be familiar with all the options available to restore venous patency, preserve valvular function, and thereby minimize the risk of late postthrombotic complications.

Comparison of the mechanical thrombectomy efficacy of the Amplatz thrombectomy device and the Cragg thrombolytic brush in vitro

RATIONALE AND OBJECTIVES

To determine the efficacy of thrombectomy (without thrombolytic agents) for the Amplatz thrombectomy device (ATD) and the Cragg thrombolytic brush catheter (CBC) in vitro.

METHODS

Thrombectomy was performed with the ATD or CBC (6F) in a flow model. Embolus sizes, weight, remaining thrombus, and activation time were evaluated.

RESULTS

No significant difference in the activation time was found. The CBC produced significantly less embolism (3.3% vs. 0.03% in the 5-mm and 89% vs. 0.5% in the 7-mm model), but also much more thrombus remained in the system than with the ATD (1% vs. 41% in the 5-mm and 0.1% vs. 62% in the 7-mm model).

CONCLUSIONS

The ATD can remove almost all thrombus (99%), whereas the CBC removes only up to 60%, producing fewer emboli than the ATD. This might be due to the lower rotational speed of the CBC compared with the ATD, which is 20 times greater. The soft nylon brush offers less resistance and shear force toward the thrombus than the stainless-steel impeller of the ATD. Because of the large amount of remaining thrombus, the CBC should not be used without lytic agents.