**4.1 Catheter directed thrombolysis**

To date, the largest DVT thrombolytic database is the venous registry (Mewissen 1999), which is a prospective registry of patients with a DVT who underwent CDT with urokinase. 473 patients were enrolled with 287 patients followed up at 1 year. 83% of patients had thrombolysis >50%. There were also a strong relationship between early thrombus removal and 1- year patency (primary patency rate of 60%). Major bleeding complications occurred in 11%, most often at the puncture site. 1% of patients developed a PE. Two patients (<1%) died (one from PE and one from intracranial haemorrhage).

Endovascular Therapies in Acute DVT 65

level is of any benefit. However, chronic lesions do benefit as well as acute obstructions

The procedure is similar to angioplasty of the arterial system. Once access is achieved, heparin is given if anticoagulation has not been already instituted. A wire is passed across the lesion, followed by a catheter. Any wire can be used however 0.035in wires are preferred. This is usually not too difficult in an acute thrombus, which is soft, and has not had time to organise. Contrast is injected beyond the lesion to ensure intraluminal position. The catheter is then exchanged for a balloon which is usually sized approximately 20% greater than the expected calibre of the vein. Angioplasty of the venous system is different from the arterial system, in that the balloons can be oversized to a greater extent than in the arteries. There is also a greater propensity for veins to have elastic recoil, such that even with aggressive angioplasty using high pressure balloons, the veins collapse back to their obstructed state. In other cases there is persistent stenosis in the vein post angioplasty. When this is the case, stenting is performed. These are also

The use of CDT and mechanical thrombectomy devices carry the theoretical increased risk of pulmonary embolisation. This has not been proven in any large scale study, and it is unclear based on current data whether this is true. In a review study by Grossman 1998, 2 out of 263 (0.7%) patients developed a PE post CDT. This is compared to the incidence of PE in patients treated with heparin alone for DVT ranging from 0-56% for symptomatic emboli, and 0-8% for asymptomatic emboli (Leizorovicz et al 1994, Sirgusa et al 1996, Levine et al

In addition, no large studies are available that looks at whether IVC filters reduce the incidence of PE following CDT or mechanical thrombectomy. Given the lack of data on their use, prophylactic IVC filters prior to commencement of CDT and/or mechanical

In a systematic review (Karthikesalingam et al 2011) of mechanical thrombectomy between 1999 and 2009, the use of prophylactic IVC filters was variable between the various authors. Almost all authors report 0% PE on follow up CTPA whether IVC filters were inserted or not. One author (Arko et al 2007) reports a 17% PE rate, all asymptomatic, in patients where no IVC filter was placed. In those that had a filter, Arko found no PE. All deaths were unrelated to the

The role IVC filters therefore is not known and there are no current recommendations regarding their use. However they are not without risk, albeit small. Filter migration, filter fracture, break through PE have all been described, as well as complications associated with

Placement of IVC filters remain at the discretion of the interventionist. In the presence of free-floating IVC thrombus or in patients with limited cardiopulmonary reserve who are unlikely to tolerate minor embolic events, IVC filtration may be appropriate with use of

permanent (Tarry WC Ann Vasc Surg 1994) or temporary filters (Lorch et al 2000).

thrombectomy (either myocardial infarct or cancer) and no patients died of PE.

(Titus 2011).

oversized in relation to the vein.

**6. Use of IVC filters** 

1995, Piccioli et al 1996).

their retrieval.

thrombectomy has been debated.

Grunwald and Hofmann (2004) retrospectively analysed 74 patients who underwent CDT for DVT and compared Urokinase, Alteplase and Reteplase. They found that there was no statistical difference between infusion times, success rates and complication rates between the three agents. However, they did find that the new recombinant agents are significantly less expensive than Urokinase in the United States.

No RCTs have been published looking at CDT in acute DVT. However, currently the TORPEDO trial is underway which is a large scale RCT looking at the efficacy of CDT vs anticoagulation in treatment of DVT. Mid term results show that CDT is superior to anticoagulation therapy alone in the prevention of recurrence of DVT, reduction in PTS, and reduction of hospital stays.

Similarly the ATTRACT Trial is currently underway looking at the efficacy of CDT.
