Endovascular Aneurysm Repair - The Procedure

The Procedure

The procedure is carried out in a sterile environment, usually a theatre, under x-ray fluoroscopic guidance. It is usually carried out by an interventional radiologist or vascular surgeon. The patient is either given a full GA (general anaestheic) or regional anaesthesia.

Vascular 'sheaths' are introduced into the patient's femoral arteries, through which the guidewires, catheters and eventually, the Stent Graft is passed.

Diagnostic angiography images or 'runs' are captured of the aorta to determine the location on the patient's renal arteries, so the stent graft can be deployed without blocking these. Failure to achieve this will cause renal failure, thus the precision and control of the graft stent deployment is extremely important. The main 'body' of the stent graft is placed first, follow by the 'limbs' which join on to the main body and sit on the Aortic Bifurcation for better support, and extend to the Iliac arteries.

For certain occasions that the aneurysm extends down to the Common Iliac Arteries, a specially designed graft stent, named as Iliac Branch Device (IBD), can be used, instead of blocking the Internal Iliac Arteries, but to preserve them. The preservation of the Internal Iliac Arteries is important to prevent Buttock Claudication, and to preserve the full genital function.

The idea is that the stent graft (covered stent), once in place acts as an artificial lumen for blood to flow down, and not into the surrounding aneurysm sac. This therefore immediately takes the pressure off the aneurysm wall, which itself will thrombose in time.

A newer adaption of EVAR is the Hybrid Procedure. A hybrid procedure occurs in the angiography room and aims to combine endovascular procedures with limited open surgery. In this procedure the stent graft deployment is planned to combine with an open operation to revascularise selected arteries that will be "covered" by the stent graft i.e. deprived of arterial inflow. In this method more extensive EVAR devices can be deployed to treat the primary lesion while preserving arterial flow to critical arteries.

Thoraco-abdominal aneurysms (TAA) typically involve such vessels and deployment of the EVAR device will cover important arteries e.g. visceral or renal arteries, resulting in end organ ischaemia which may not be survivable. The open operation component aims to bring a bypass graft from an artery outside the stent graft coverage to vital arteries within the coverage region. This component adds to the EVAR procedure in time and risk but is usually judged to be lesser that the risk of the major totally open operation.

Staging such procedures is common. A common example is revascularisation of the left common carotid artery and/or the left subclavian artery from the innominate artery or the right common carotid artery to allow treatment of a thoracic aortic aneurysm that encroachs proximally into the aortic arch to be treated without thoracotomy. Continued design improvement in stent graft including branched endografts will reduce but not eliminate this category of surgery. 'Chimney stents into the innominate artery with TEVAR into the proximal aortic arch have recently been described. Other surgeons favor limited thoracotomy with carotid-carotid bypass i.e. hybrid procedures.

All such procedures aim to reduce the morbidity and mortality of treating arterial disease in a patient polpulation that is increasingly older and less fit than when major open repairs were developed and popularised. Even in those days, significant risks were accepted in the understanding than the large open operation was the only option. That is not the case in most patients today. Durability and problems such as 'endoleaks' may require careful surveillance and adjuvant procedures to ensure success of the EVAR or EVAR/hybrid procedure. CT Angiography (CTA) imaging has in particular made a key contribution to planning, success, durabity in this complex area of vascular surgery.