**3.3 Percutaneous mechanical thrombectomy and pharmacomechanical thrombolysis**

This involves use of a mechanical clot removal device such as a Trerotola (Arrow-Trerotola™ PTD®, Arrow, Reading, PA) which is a rotational device or a hydrodynamic device such as Angiojet (AngioJet® Rheolytic Thrombectomy system: Medrad Intervention, Warrendale, PA) . Other devices such as Trellis (Cividien, Santa Clara, California) or the Clot Buster Amplatzer Thrombectomy Device (ATD, Minneapolis, MN) are also available.

The aim is to achieve maceration/disruption of the clot, thus facilitating thrombus aspiration and removal. This is a much less invasive option than open surgical thrombectomy and other advantages include improved clot removal and more rapid restoration of flow. Intensive patient monitoring is also not necessary unlike catheter directed thrombolysis (fig. 10).

Fig. 10. Catheter thrombectomy. (a) Catheter tip within the right main pulmonary artery, adjacent to embolus (*arrow*). (b) Post – treatment shows disruption of the clot. Note the striking difference in contrast opacification of the pulmonary arterial tree pre – and post – treatment.

Radiological Imaging and Intervention in Venous Thrombosis 93

These percutaneously implantable devices are placed in the infra-renal inferior vena cava to reduce the risk of a significant pulmonary embolism (fig. 11). Specific indications include venous thromboembolism with a contraindication to oral anticoagulation or pulmonary embolism despite adequate anticoagulation (Kaufman et al., 2006). There are further uses including patients with DVT who have cancer or burns, and also in high risk trauma and surgical patients. Case selection is paramount and the risks of device implantation and

Device implantation is usually via the femoral or the internal jugular vein in a suitable infrarenal position. Cavograms are performed to delineate the renal veins, asses the extent of thrombus and exclude contraindications such as dilated IVC which may not be suitable for standard filter deployment. Suprarenal placement is undertaken if there is thrombus

IVC filters are classified as temporary or permanent (Streiff, 2000) and there are various devices available that are approved for use. To cite a few examples, the Bird`s Nest Filter and the Trapease filter are permanent whereas the Gunther Tulip and the Cook Celect Filter are retrievable. Timely removal of retrievable filters is important to reduce the long term

**3.5 Inferior vena cava filters** 

removal must be carefully assessed.

extension into or above the renal veins.

Fig. 11. Temporary IVC filter (*arrow*).

Complications include vessel wall and valve injury and kidney failure due to haemolysis. Although patients can experience transient shortness of breath presumably due to pulmonary microemboli, experience gained from thrombectomy of clotted fistulas has shown that concomitant use of a plasminogen activator significantly reduced the risk of symptomatic pulmonary embolism from the procedure (O'Sullivan, 2010).

Pharmacomechanical thrombolysis involves the combined use of a thrombectomy device in combination with catheter directed infusion of a thrombolytic agent. The advantages of this combination include better permeation of the thrombolytic agent and a smaller duration of treatment. Although some devices can lower the systemic dose of the drug, others do not do so.

A retrospective study of 93 patients showed that pharmacomechanical thrombolysis was an effective treatment modality in patients with significant DVT and compared to catheter directed thrombolysis alone, it provided similar treatment success, reduced length of intensive care and hospital stay, and reduced hospital costs (Lin et al., 2006). However, another study has shown that that use of the Trerotola device alone constituted effective treatment of acute ilio-femoral DVT independent of adjunct pharmacological thrombolysis (Lee et al., 2006).

There is, however, a relative lack of randomised data on the use of these devices and further randomised studies are necessary.

#### **3.4 Venoplasty and stenting**

Balloon venoplasty is usually performed in patients in combination with catheter directed thrombolysis or pharmacomechanical treatment to help macerate the existing clot or to dilate a venous stenosis which may have been a contributory factor in the development of the DVT. Venous stenosis can occur due a number of aetiologies. Benign causes include May-Thurner syndrome (Ferris et al., 1983), where long standing pulsatile compression of the left common iliac vein by the left common iliac artery leads to development of a venous web. Malignant compression or invasion can be another cause. Chronic deep vein thrombosis can lead to vessel wall fibrosis and development of stenosis.

Unlike arteries, veins have a high elastic recoil and lower rates of flow which leads to less satisfactory results with long term stent patency, in the iliac veins, with a greater than 50% re-stenosis in up to 15% of patients (Hood & Alexander, 2004). These figures are much worse for patients who are hypercoagulable, have longer stent lengths and need infrainguinal stents.

Stenting an underlying lesion has, however, shown to help prevent or prolong the interval to recurrence and can result in 50% increased patency rate than thrombolysis alone (Hood & Alexander, 2004) and lower recurrence rates of ilio-femoral DVT (up to 73% lower) in patients with May-Thurner syndrome (Oguzkurt et al., 2004). Most experience has been gained with Wallstents (Boston Scientific, Hemel Hempstead, Herts, UK) which are self expanding stents with a good radial strength. Studies have also shown the efficacy and durability of stents in the IVC (Ing et al., 2001; Razavi et al., 2000).

### **3.5 Inferior vena cava filters**

92 Deep Vein Thrombosis

Complications include vessel wall and valve injury and kidney failure due to haemolysis. Although patients can experience transient shortness of breath presumably due to pulmonary microemboli, experience gained from thrombectomy of clotted fistulas has shown that concomitant use of a plasminogen activator significantly reduced the risk of

Pharmacomechanical thrombolysis involves the combined use of a thrombectomy device in combination with catheter directed infusion of a thrombolytic agent. The advantages of this combination include better permeation of the thrombolytic agent and a smaller duration of treatment. Although some devices can lower the systemic dose of the drug,

A retrospective study of 93 patients showed that pharmacomechanical thrombolysis was an effective treatment modality in patients with significant DVT and compared to catheter directed thrombolysis alone, it provided similar treatment success, reduced length of intensive care and hospital stay, and reduced hospital costs (Lin et al., 2006). However, another study has shown that that use of the Trerotola device alone constituted effective treatment of acute ilio-femoral DVT independent of adjunct pharmacological thrombolysis

There is, however, a relative lack of randomised data on the use of these devices and further

Balloon venoplasty is usually performed in patients in combination with catheter directed thrombolysis or pharmacomechanical treatment to help macerate the existing clot or to dilate a venous stenosis which may have been a contributory factor in the development of the DVT. Venous stenosis can occur due a number of aetiologies. Benign causes include May-Thurner syndrome (Ferris et al., 1983), where long standing pulsatile compression of the left common iliac vein by the left common iliac artery leads to development of a venous web. Malignant compression or invasion can be another cause. Chronic deep vein

Unlike arteries, veins have a high elastic recoil and lower rates of flow which leads to less satisfactory results with long term stent patency, in the iliac veins, with a greater than 50% re-stenosis in up to 15% of patients (Hood & Alexander, 2004). These figures are much worse for patients who are hypercoagulable, have longer stent lengths and need infra-

Stenting an underlying lesion has, however, shown to help prevent or prolong the interval to recurrence and can result in 50% increased patency rate than thrombolysis alone (Hood & Alexander, 2004) and lower recurrence rates of ilio-femoral DVT (up to 73% lower) in patients with May-Thurner syndrome (Oguzkurt et al., 2004). Most experience has been gained with Wallstents (Boston Scientific, Hemel Hempstead, Herts, UK) which are self expanding stents with a good radial strength. Studies have also shown the efficacy and

thrombosis can lead to vessel wall fibrosis and development of stenosis.

durability of stents in the IVC (Ing et al., 2001; Razavi et al., 2000).

symptomatic pulmonary embolism from the procedure (O'Sullivan, 2010).

others do not do so.

(Lee et al., 2006).

inguinal stents.

randomised studies are necessary.

**3.4 Venoplasty and stenting** 

These percutaneously implantable devices are placed in the infra-renal inferior vena cava to reduce the risk of a significant pulmonary embolism (fig. 11). Specific indications include venous thromboembolism with a contraindication to oral anticoagulation or pulmonary embolism despite adequate anticoagulation (Kaufman et al., 2006). There are further uses including patients with DVT who have cancer or burns, and also in high risk trauma and surgical patients. Case selection is paramount and the risks of device implantation and removal must be carefully assessed.

Device implantation is usually via the femoral or the internal jugular vein in a suitable infrarenal position. Cavograms are performed to delineate the renal veins, asses the extent of thrombus and exclude contraindications such as dilated IVC which may not be suitable for standard filter deployment. Suprarenal placement is undertaken if there is thrombus extension into or above the renal veins.

Fig. 11. Temporary IVC filter (*arrow*).

IVC filters are classified as temporary or permanent (Streiff, 2000) and there are various devices available that are approved for use. To cite a few examples, the Bird`s Nest Filter and the Trapease filter are permanent whereas the Gunther Tulip and the Cook Celect Filter are retrievable. Timely removal of retrievable filters is important to reduce the long term

Radiological Imaging and Intervention in Venous Thrombosis 95

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risk of filter deployment. In terms of safety and efficacy, there is no significant difference between the two types of devices (Nazir et al., 2009). Complications associated with the device include those encountered at the time of insertion such as access site haematoma, pneumothorax, inadvertent arterial puncture and misplacement. Delayed complications include IVC thrombosis, occlusion, venous insufficiency and pulmonary embolism.
