2 The condition, current treatments and procedure
2.1 Chronic limb-threatening ischaemia of the lower extremities is caused by severely narrowed or blocked arteries. It is an advanced stage of peripheral arterial disease. The severely reduced blood supply causes ischaemic pain, ulceration, tissue loss and gangrene. It is associated with high amputation and mortality rates, and poor quality of life.
2.2 Chronic limb-threatening ischaemia usually needs treatment to re-establish blood flow to the affected area and to prevent major amputation. Treatment options include medications, endovascular interventions (such as angioplasty, stents and directional atherectomy) and surgical treatments (such as bypass). Management of chronic limb-threatening ischaemia is described in NICE's clinical guideline on peripheral arterial disease.
2.3 The procedure uses an endovascular, minimally invasive approach. An arteriovenous fistula is created to allow venous arterialisation in the below-the-knee vasculature. The aim is to restore blood flow to the ischaemic foot.
2.4 Preoperative investigation is needed to confirm adequate pedal venous anatomy and identify a suitable crossover point between the vessels.
2.5 The procedure is usually done using general anaesthesia, and with ultrasound guidance. Antegrade arterial access is established through the common femoral artery, and retrograde venous access is established through the tibial vein. Arterial and venous catheters are inserted and advanced to the target artery and vein (most frequently the posterior tibial artery and vein). Once both catheters are positioned with a crossover point, a needle is used to create an arteriovenous fistula. Valvulotomy of the vein is then done, usually from the crossover point to the midfoot. Multiple stents are placed in the vein from the level of the calcaneus to the arteriovenous crossover point, and a crossing stent is inserted to maintain the arteriovenous fistula. This establishes retrograde blood flow down the veins, which become arterialised.
2.6 Arteriography is done at the end of the procedure to visualise blood flow into the deep venous arch.