What are venous thrombolysis, thrombectomy and recanalization? Why perform them?
Deep vein thrombosis is a blood clot or thrombus in a deep vein. They occur most commonly in the leg. But they may develop in the arm or other parts of the body. If left untreated, the clots may break off and block off the blood supply to the lungs, which can be potentially life-threatening. In addition, large blood clots can restrict normal blood return from the arms or legs, which can lead to limb swelling, pain or even tissue breakdown.
While most blood clots in the veins can be dissolved with anticoagulation medications alone, minimally invasive treatments such thrombolysis and thrombectomy can be used to treat large blood clots or blood clots that is causing severe symptoms in the limb.
Thrombolysis, or cathter-directed thrombolysis, uses a thin tube with multiple holes at its tip to deliver a concentrated dose of clot-dissolving medication to the clots. Thrombectomy uses mechanical means to remove the clots by suction. Thrombolysis and thrombectomy can be applied on its own or as combination therapy.
In the long run, blood clots inside the veins can damage venous valves and cause narrowing or complete blockage (occlusion) of the veins. Recanalisation procedures are minimally invasive methods to restore normal blood flow to these narrowed or occluded veins. This involves balloon dilatation (venoplasty), stenting or a combination of both.
How does the procedure work?
For venous thrombolysis and thrombectomy, the interventional radiologist will insert a sheath (a long plastic tube 2-3 mm in diameter) into a vessel vein in your neck or groin under ultrasound guidance. Small amount of contrast dye will be injected to get a picture under X-ray (known as “venogram”) to assess the severity of the condition,. The interventional radiologist will then decide if thrombolysis is adequate or an additional thrombectomy needs to be done.
For thrombolysis, a special catheter with multiple holes will be directed to the clots. Clot dissolving medication will be infused through this catheter for around 1 – 2 days. During this period, you will be monitored closely as an in-patient. After the thrombolysis therapy, you will be brought back to the interventional radiology department for another venogram to assess the results. If the clots have not dissolved satisfactorily, additional thrombolysis or thrombectomy may be performed.
For thrombectomy, a special suction catheter will be directed to the clots. Some of these catheters will spray water to dissolve the clot first before suction removal while some catheters will remove the clot as a whole by suction.
For venous recanalization, the interventional radiologist will attempt to navigate across the narrowed or blocked vein using guidewires. If this is successful, the narrowing will be dilated using special balloons and then a stent will usually be placed to provide better support to the vein walls. If the guidewire is unable to pass across the blocked vein, a sharp needle may have to be used.
If a stent is placed, you may be asked to take lifelong anti-platelet medications to prevent stent blockage.
What are the risks?
Common risks include risks include bruising at the puncture site or in the affected area. Bleeding is one of the major risks for thrombolysis. Rarely this may cause bleeding within the skull which can be life-threatening. For thrombectomy, depending on the mechanism of clot removal, it may lead to acute electrolyte imbalance and reddish urine.
Some of the rare but important risks for venous recanalisation include vein rupture and dislodgement of the stent (meaning the stent has moved away from the target vein and displaced to another site). These complications may need surgical management.
Bibliography
1. Results of a prospective randomized trial evaluating surgery versus thrombolysis for ischemia of the lower extremity. The STILE trial. Annals of Surgery. 1994; 220(3):251-66; discussion 66-8. Epub 1994/09/01.