The most common approach to interventional management of deep vein thrombosis is catheter-directed thrombolysis. Limitations of catheter-directed thrombolysis led to the development of percutaneous mechanical thrombectomy devices as well as lytic-assisted devices, writes Mahmood Razavi, director, Center for Clinical Trials and Research, Heart and Vascular Center, St Joseph Hospital, Orange, California, USA
Endovascular management of deep vein thrombosis is gaining more recognition among non-interventionalists and those who initially see and diagnose patients with this condition. Although only a small minority of such patients currently receive catheter-based therapy, the practice is widespread. Yet, there is no commonly accepted standardised technique.
The most common approach to interventional management of deep vein thrombosis is catheter-directed thrombolysis. Limitations of catheter-directed thrombolysis led to the development of percutaneous mechanical thrombectomy devices as well as lytic-assisted devices.
To date, there have been a large number of percutaneous mechanical thrombectomy devices introduced into the market. As a standalone technique and without the use adjunctive thrombolytic drugs, the efficacy of current generations of percutaneous mechanical thrombectomy devices has been disappointing in proximal deep vein thrombosis. These devices tend to work well removing hyper-acute clot and hence it is not a surprise that they fall short in patients with deep vein thrombosis who may have clots that are 2–3 weeks old.
The lytic-assisted devices, which include pharmacomechanical and sonically-enhanced thrombolysis are designed to augment the efficacy of thrombolytic drugs. The current popular approaches include the use of Trellis catheter (Covidien), EkoSonic Endovascular System (EKOS), and the combination of Angiojet (Medrad/Possis) and a thrombolytic drug employing the “power-pulse” technique.
Reporting the results of an industry-sponsored prospective survey of the use of Trellis-8 catheter, Hillman reported a high degree of clot lysis during single session treatments of patients with acute deep vein thrombosis (Hillman DE. JVIR 2008;19:377). As with catheter-directed thrombolysis, efficacy dropped as the clot age increased beyond 2–3 weeks. The important lesson learned was that an acute thrombus can be removed on the table without the need for overnight infusion of thrombolytic drugs. Furthermore, Hillman’s study showed lower resource utilisation when the Trellis-8 strategy was utilised as compared to catheter-directed thrombolysis.
The Ekosonic Endovascular system takes advantage of the ability of sonic waves to accelerate the process of thrombolysis. In the study by Parikh et al 70% of patients with acute deep vein thrombosis who underwent sonically-enhanced lysis had complete resolution of clot after an overnight infusion of thrombolytics (Parikh S et al. JVIR 2008;19:521). This is an overall improved result compared to that observed in the National Venous Registry (Mewissen MW, et al. Radiology 1999; 211:39–49), using catheter-directed thrombolysis alone.
Unpublished data from centres employing the “power-pulse” technique suggest that same-session clot removal can also be successful using the combination of Angiojet and thrombolytic drugs.
In the author’s experience, however, a single session strategy can be successful if the clot is limited to the femoral veins with adequate inflow from the popliteal vein, and unobstructed outflow through the ilio-caval segments. Involvement of larger venous structures such as the iliacs and inferior vena cava will often require use of adjunctive techniques such as catheter-directed thrombolysis and/or stenting.
Experience to date indicates that the toolbox for the treatment of various venous conditions, while improving, remains incomplete. Despite the progress in the past decade, the venous space is in dire need of innovative approaches in all aspects of its endovascular care.