3 The procedure
3.1 Ultrasound‑enhanced, catheter‑directed thrombolysis is an endovascular technique that uses high‑frequency, low‑energy ultrasound waves in combination with infusion of a thrombolytic drug, with the aim of accelerating plasmin‑mediated thrombolysis. It aims to reduce treatment time, the dose of thrombolytic drug delivered and thrombolysis‑related complications, compared with catheter‑directed thrombolysis alone.
3.2 The procedure is done using local anaesthesia, with imaging guidance by fluoroscopy. Therapeutic doses of heparin are administered through a peripheral catheter before and during the procedure.
3.3 With the patient in the supine position, a diagnostic catheter is inserted into the area of the thrombosis via the femoral, jugular or popliteal vein and a venogram is done. A guide wire is passed through the thrombosed segment of vein under X‑ray guidance and the diagnostic catheter is removed. A multi‑lumen infusion catheter is passed over the guide wire into the thrombosed venous segment and the guide wire is replaced with an ultrasound core wire. This wire has multiple small ultrasound transducers that deliver ultrasound waves along the entire treatment zone. A thrombolytic drug is infused directly into the thrombus through holes in the side of the catheter, using an infusion pump, along with a flow of saline to act as a coolant while the ultrasound is activated. An electronic device controls the ultrasound power output. The patient is continuously monitored from the start of the treatment. Treatment typically lasts for 12–24 hours.
3.4 Follow‑up venographic and echocardiographic assessment is performed at regular intervals after the start of the procedure. Once the thrombus has cleared, or there is no further progress, the treatment is stopped and the patient starts standard anticoagulant therapy.