Complications of Iliofemoral Thrombolysis and Stenting for Venous Disease

Introduction

Many patients with symptomatic iliofemoral deep vein thromboses (DVTs) are now undergoing intervention to minimize thrombus burden in order to decrease venous pressures and preserve valve function. For patients with extensive and/or severely symptomatic DVT, catheter-based intervention is standard of care. Current guidelines from the Society of Vascular Surgeons and American Venous Forum for treatment are acute proximal DVT with symptoms <14 days, good functional capacity, life expectancy greater than 1 year, phlegmasia cerulea dolens, and low bleeding risk.

Access for Catheter-Directed Thrombolysis

Successful catheter-directed thrombolysis (CDT) begins with access, for which preoperative assessment is helpful. Access should be obtained one level below the majority of the thrombus burden, often the ipsilateral popliteal vein with the patient in prone position. If the thrombus extends below the popliteal vein, access can be obtained in the small saphenous vein or one of the posterior tibial veins at the medial malleolus. If the thrombus is isolated to the iliac system, the ipsilateral femoral vein can be accessed with the patient in supine position. Alternatively, the contralateral femoral vein can be accessed for the up-and-over technique. Lastly, the internal jugular (IJ) can also be used; however, this is used less in acute situations, in which crossing is typically easy and thrombolysis usually necessary. One challenge with access from the contralateral femoral vein or jugular vein is that retrograde crossing of the valves can be more difficult.

Ultrasound-guided access should be obtained with a micropuncture system, with negative pressure on the attached syringe, partially filled with saline. Using ultrasound, the needle tip should be visualized entering the vein, as blood is not always seen in the syringe because of the thrombus. Multiple punctures, more likely without ultrasound guidance, can lead to hematoma and premature termination of the procedure.

An access venogram is performed via the micropuncture sheath to confirm location and visualize thrombus burden. It is important to use only gentle hand injections, not power injections, because of the risk of embolization. The microsheath is then upsized to a 6-French sheath to facilitate crossing of the thrombosed vein. Initial attempts are made with 0.035″ hydrophilic guidewire, such as a regular or stiff Angled Glidewire (Terumo, Somerset, New Jersey), along with a guiding catheter, such as a Glidecatheter (Terumo). An angled guiding catheter or wire is preferable to allow steering past the occlusions. Venograms are performed at various levels to visualize the extent of thrombus burden. Venogram is also performed once the catheter passes into the inferior vena cava (IVC) to confirm patency distal to the thrombus. If the entire thrombus burden is not treated, it is likely to fail because of continued outflow obstruction.

Once the lesion is crossed, there are several options. Thrombus removal can be achieved in one session, with pharmacomechanical thrombectomy, or in multiple sessions with thrombolysis with or without pharmacomechanical thrombectomy.

Thrombolysis

After confirming appropriate position by venogram, a multi-sideport infusion lysis catheter is placed. There are several options available including: Unifuse (AngioDynamics, Latham, NY), Cragg McNamara (Medtronic, Minneapolis, MN), EkoSonic (Boston Scientific, Marlborough, MA). The length of thrombus should be measured using a marking catheter or tape, intravascular ultrasound (IVUS) pullback, or measurements based on venogram. The catheter treatment zone is based on the length of the thrombus and ranges from 5 to 50 cm. Once the infusion catheter is in place, thrombolytic therapy is initiated, typically with 0.5–2 mg/h of recombinant tissue plasminogen activator (rtPA). The optimal dose has not been established. Lower doses may result in inadequate thrombus removal and higher doses may increase the risk of major bleeds. In addition to the rtPA, heparin is infused via the sheath to maintain sheath patency. There are no studies directly assessing the optimal dose of heparin during thrombolysis. Our practice is to use subtherapeutic levels (such as 500 U/h of unfractionated heparin); however, higher levels are sometimes used with higher thrombus burdens.

Patients undergoing thrombolysis are monitored in an intensive care unit (ICU) or step down unit and kept flat, with the limb straight to prevent kinking or displacement of the catheter. Routine laboratory work is recommended, including prothrombin time, partial thromboplastin time, hemoglobin/hematocrit and fibrinogen every 4–12 hours, in addition to neurovascular checks and monitoring the puncture site for bleeding. Fibrinogen monitoring is controversial. If the fibrinogen drops below 100 mg/dL, the rtPA infusion is reduced or discontinued to decrease risk of major bleeding. While the rtPA is held, therapeutic anticoagulation is administered via the catheter and saline via the sheath and the fibrinogen level is rechecked in 2–4 hours if the patient has not undergone repeat imaging. We find that a significant reduction in fibrinogen is usually an indicator that the thrombus burden has greatly decreased, and now the lytic agent is being infused more systemically indicating more urgent follow-up is needed. Repeat imaging routinely occurs after 12–24 hours, but is done earlier if fibrinogen greatly decreases or the patient demonstrates clinical signs of significant improvement. If thrombolysis is not complete at repeat imaging and repeat fibrinogen levels have adequately rebounded, rtPA can be restarted at half the dose, with close surveillance of fibrinogen levels and for signs of bleeding. Thrombolysis >72 hours greatly increases bleeding risk. Use of retrievable IVC filters to prevent pulmonary embolus during thrombolysis is controversial. However, recommendation for consideration of an IVC filter would be the following: (1) large thrombus burden involving the iliocaval segment; (2) free-floating thrombus in the iliocaval segment; (3) patient presenting with iliofemoral DVT and pulmonary embolus (PE); and (4) patients with poor cardiopulmonary reserve. If placed, once the threat of PE is no longer an issue, the retrievable ICV filter should be removed, usually at 4–6 weeks posttreatment. In addition, and in most circumstances, there is no need to stop anticoagulation during filter retrieval. Filters can easily be placed via the popliteal access. Two filters, Optease (Cordis, Santa Clara, CA) and Optional Elite (Argon Medical Devices, Frisco, TX), have a 70-cm treatment length. If access is more distal and a filter is desired, IJ placement may be necessary prior to accessing tibial veins because the delivery system for the filter will not reach from the tibial to the correct location in the IVC.