**3.1 Introduction**

Despite advances in diagnostic techniques and therapeutic approaches, DVT remains a potentially life threatening disorder. Anticoagulation, which is the current standard of treatment for patients with acutely diagnosed above knee DVT, involves treatment with low molecular weight heparin followed by a 6 month course of warfarin (Hyers et al., 1998). This treatment is designed to stop further progression and potential embolisation, but does not treat or remove the existing thrombus and may be insufficient in treatment of extensive iliofemoral thrombosis. A large clot burden in the proximal veins in the acute phase can lead to local complications including venous oedema, acute compartment syndrome, tissue necrosis and venous gangrene, and systemic complications such as PE.

Over time normal fibrinolytic mechanisms will result in a variable degree of recanalisation of the thrombosed segment but this may not be sufficient for resolution of clinical symptoms. Chronic DVT and venous insufficiency has been shown to diminish a person`s quality of life and socioeconomic activity (Vedantham et al., 2004).

There are a number of endovascular treatment options in DVT which aim to achieve thrombus removal, restoring patency and potentially limiting the acute complications associated with DVT. It is important to appreciate the limitations of these treatments and the relative lack of randomised controlled trials evaluating the efficacy of these interventions.

## **3.2 Catheter directed thrombolysis treatment**

This technique involves infusion of a thrombolytic agent in and around the thrombus via an infusion catheter. This leads to high dose delivery of the thrombolytic agent locally, reducing the systemic complications, and has been shown to have almost double the venous patency rate at one year, compared to systemic thrombolysis (Comerota et al., 2007). This has been sanctioned by the American College of Chest Physicians (ACCP) as a first line treatment in "selected patients with extensive acute proximal DVT who have a low risk of bleeding" (Kearon et al., 2008). Further criteria include a young patient with a good functional status, life expectancy greater than one year and symptoms for ideally less than 14 days.

Although the administration of the thrombolytic agent is local, the lytic agent can migrate systemically and can increase the risk for major bleeding complications requiring the patient to be monitored aggressively in a high dependency/intensive care setting.

The route for catheter placement is usually decided depending on the thrombus location and burden. This may be placed via the jugular, contralateral femoral or ipsilateral popliteal vein, ideally using ultrasound guided access. Catheters with multiple side - holes and long infusion length can be used for drug delivery and although there is no single drug that has been approved for this use, streptokinase and more recently alteplase (rt-PA) have been

The limitations of MR are the relative expense limiting availability, and for some patients the claustrophobic environment preventing completion of the examination. At present, MRI should be considered when there is a strong clinical suspicion of pelvic DVT, and in young women requiring investigation for PE with abnormal chest X – ray precluding a V/Q scan.

Despite advances in diagnostic techniques and therapeutic approaches, DVT remains a potentially life threatening disorder. Anticoagulation, which is the current standard of treatment for patients with acutely diagnosed above knee DVT, involves treatment with low molecular weight heparin followed by a 6 month course of warfarin (Hyers et al., 1998). This treatment is designed to stop further progression and potential embolisation, but does not treat or remove the existing thrombus and may be insufficient in treatment of extensive iliofemoral thrombosis. A large clot burden in the proximal veins in the acute phase can lead to local complications including venous oedema, acute compartment syndrome, tissue necrosis

Over time normal fibrinolytic mechanisms will result in a variable degree of recanalisation of the thrombosed segment but this may not be sufficient for resolution of clinical symptoms. Chronic DVT and venous insufficiency has been shown to diminish a person`s

There are a number of endovascular treatment options in DVT which aim to achieve thrombus removal, restoring patency and potentially limiting the acute complications associated with DVT. It is important to appreciate the limitations of these treatments and the relative lack of randomised controlled trials evaluating the efficacy of these interventions.

This technique involves infusion of a thrombolytic agent in and around the thrombus via an infusion catheter. This leads to high dose delivery of the thrombolytic agent locally, reducing the systemic complications, and has been shown to have almost double the venous patency rate at one year, compared to systemic thrombolysis (Comerota et al., 2007). This has been sanctioned by the American College of Chest Physicians (ACCP) as a first line treatment in "selected patients with extensive acute proximal DVT who have a low risk of bleeding" (Kearon et al., 2008). Further criteria include a young patient with a good functional status, life

Although the administration of the thrombolytic agent is local, the lytic agent can migrate systemically and can increase the risk for major bleeding complications requiring the patient

The route for catheter placement is usually decided depending on the thrombus location and burden. This may be placed via the jugular, contralateral femoral or ipsilateral popliteal vein, ideally using ultrasound guided access. Catheters with multiple side - holes and long infusion length can be used for drug delivery and although there is no single drug that has been approved for this use, streptokinase and more recently alteplase (rt-PA) have been

expectancy greater than one year and symptoms for ideally less than 14 days.

to be monitored aggressively in a high dependency/intensive care setting.

**3. Role of interventional radiology in venous thrombosis** 

and venous gangrene, and systemic complications such as PE.

quality of life and socioeconomic activity (Vedantham et al., 2004).

**3.2 Catheter directed thrombolysis treatment** 

**3.1 Introduction** 

used for this purpose. Venography at the time of the procedure can help assess the clot burden, plan adjunctive treatments (venoplasty, pharmaco-mechanical disruption) and also help define a suitable end point.

There is however a lack of prospective randomised data assessing the benefits of thrombolysis as compared to anticoagulant therapy (Pianta & Thomson, 2011). This, in combination with haemorrhagic complications and lack of awareness among physicians has limited acceptance of this procedure.
