3 The procedure
3.1 Mechanical clot retrieval for treating acute ischaemic stroke is done for stroke caused by blockage of a main cerebral artery. Immediately after they are admitted to hospital, patients have a CT scan and a CT or MR angiogram to confirm the presence of a major vessel occlusion. The procedure is then usually done with the patient under sedation, but sometimes general anaesthesia is used. Conventional cerebral angiography is done to show the exact location of the arterial occlusion. A delivery catheter is inserted, usually through the femoral artery in the groin, and advanced into the occluded artery using X‑ray guidance. A clot‑retrieval device attached to a guidewire is introduced through the delivery catheter to the site of the occlusion, to remove the clot and re‑establish blood flow to the affected part of the brain. Many patients will also have had initial treatment with intravenous thrombolysis.
3.2 Several types of device and different techniques have been used for clot retrieval. Most recent clinical trial evidence is based on the use of stent retrievers, which are currently the most commonly used type of device. The stent retriever is a self‑expanding metal mesh tube that is introduced through a catheter and partially deployed within the clot. The stent retriever traps the clot within its mesh and is then withdrawn through the catheter.
3.3 The aim is to perform the procedure as soon as possible after the onset of stroke symptoms.