Does pharmacomechanical catheter-directed thrombolysis (PCDT) reduce the development of post-thrombotic syndrome after proximal deep vein thrombosis (DVT)?

Why is post-thrombotic syndrome after DVT important?

Post-thrombotic syndrome is a common complication that occurs in 25-50% of patients with a proximal lower-extremity DVT. Symptoms of PTS include lower-extremity pruritus, edema, pain, heaviness, venous stasis dermatitis, and skin ulceration. Most patients who develop post-thrombotic syndrome do so within 2 years of being diagnosed with DVT. The development of post-thrombotic syndrome can impair quality of life, interfere with ability to work, and is costly to the health care system. Therefore, reducing the rate of post-thrombotic syndrome PTS is a clinically important outcome.

What is pharmacomechanical catheter-directed thrombolysis?

Previous studies have looked at post-thrombotic syndrome rates after infusing fibrinolytic agents directly into the thrombus (a procedure called "catheter-directed thrombolysis"). PCDT uses infusion of thrombolytics in combination with a device that mechanically "chews up" the thrombus. The hypothesis is that actively removing the thrombus opens the vein more rapidly and restores blood flow, thereby reducing post-thrombotic syndrome.

What were the results of the ATTRACT Trial, and how can I apply them to my patient?

Most current guidelines state that PCDT can be considered in patients with an iliofemoral DVT, as long as the procedure occurs within 14 days of the start of symptoms.^1,2 The ATTRACT Trial found that adding PCDT to anticoagulation did not significantly decrease the overall rate of post-thrombotic syndrome after 2 years, and patients who received PCDT had a higher incidence of early major bleeding. Although the trial found that the rate of moderate or severe post-thrombotic syndrome was decreased with PCDT, this did not translate into improvement in patient-reported quality of life at 24 months. A prespecified subgroup analysis showed that adding PCDT to anticoagulation did not reduce the rate of post-thrombotic syndrome even in patients with iliofemoral (more proximal) DVT compared with femoropopliteal (more distal) DVT. Overall, the ATTRACT Trial showed that adding PCDT to standard anticoagulation did not change long-term outcomes.

This trial showed that the benefit of PCDT may be to reduce patient-reported leg pain and edema in the short term (within 30 days of symptom onset). However, the reduction in patient-reported pain with PCDT was small (a reduction of about 0.3 points on a 7-point Likert pain scale) and came at a cost of higher major early bleeding rates (with about 1 out of 100 patients having a major bleed within 10 days after PCDT). 

Did this trial have any limitations?​​​​​​​

• The type of device and duration of fibrinolytic infusion used for PCDT therapy varied. Some devices and treatment protocols may be better than others at reducing post-thrombotic syndrome rates.
• More patients in the anticoagulant therapy alone group missed at least 1 of the assessments for post-thrombotic syndrome. Therefore, the rate of post-thrombotic syndrome in this group may be higher than what was reported. However, it is reassuring that the overall rate of post-thrombotic syndrome in this trial is similar to what other studies have reported.³

**PCDT should still be considered for patients with phlegmasia cerulea dolens or threatened limb ischemia

Doctor, I have just been told I have a DVT, and my leg is very large and painful. Can you do something to remove the clot?

There is an invasive procedure called pharmacomechanical catheter-directed thrombolysis (PCDT), which uses a combination of "clot busting" medications and a mechanical device to break up the clot. However, a recent study showed that while PCDT reduced pain and swelling by a small amount in the short term, it did not reduce the risk of long-term complications such as post-thrombotic syndrome (chronic painful swelling of the leg), and more important, it caused more serious bleeding than treatment with anticoagulants (blood-thinners) alone. Most people will see improvement in their leg symptoms as their body works on slowly breaking down the clot over time. Anticoagulant therapy is taken to prevent further clotting while healing is taking place.

1. Thrombosis Canada. (2017). Deep Vein Thrombosis (DVT): Treatment. [online] Available at: http://thrombosiscanada.ca/clinicalguides.

2. Kearon, C., Akl, E., Ornelas, J., et al. Antithrombotic Therapy for VTE Disease. Chest, 2016;149:315-352.

3. Roumen-Klappe, E., den Heijer, M., Janssen, M., et al. The post-thrombotic syndrome: incidence and prognostic value of non-invasive venous examinations in a six year follow-up study. Thromb Haemost. 2005;94:825-30.