We spoke to Dr. Ondina Bernstein to hear more on the FEVAR/BEVAR planning and interventions workshop that took place at CIRSE 2022.
Tips and tricks in FEVAR/BEVAR planning and interventions
The endovascular treatment options for juxta-renal and thoraco-abdominal aortic aneurysms have improved substantially in recent years with an increasing number of both off-the-shelf and custom-made endo grafts available. The clinical condition of patients and their anatomy need to be critically assessed on a case-by-case basis to decide on the best treatment for the patient. Despite the advances in endo graft technology, the success of the implantation and clinical outcomes depend on correctly sized and planned endo grafts. CT angiograms with a minimum slice thickness of 1mm are reformatted on planning software, prior to the manufacture of a customised endo graft.
The landing zones are assessed to decide the type of endo graft required to achieve a seal both proximally and distally. Fenestrated endovascular repair (FEVAR) is generally utilised for juxta-renal aortic aneurysms and branched endovascular repair (BEVAR) for thoraco-abdominal aortic aneurysms. BEVAR requires a minimum diameter of the aorta at the level of the visceral arteries, depending on the device used.
Access is planned to ensure that the delivery system of the endo graft can be inserted. In general, the common femoral and iliac arteries should be a minimum of 7-8mm in diameter. Angioplasty or an iliac conduit are adjunctive procedures that may be required or an open repair could be considered instead. The most common intraoperative adverse events are access complications and target artery complications. 
FEVAR for juxta-renal aneurysms may have fenestrations for two, three, four or even five visceral arteries. With increasing experience and follow-up, there has been a move to targeting more visceral arteries for a better proximal seal. Endo graft design differs between manufacturers. Cook Zenith® FEVAR and t-Branch® endo grafts commonly have two sealing stents proximal to the fenestrations/branches, but by optimising the sealing zone and improving durability, the risk of spinal cord ischaemia increases. Some centres advocate the use of prophylactic spinal drains for all cases, while other centres take a more selective approach. If full coverage of the descending thoracic aorta is required, staged procedures can reduce the risk of paraplegia.
The visceral arteries are scrutinised to plan the “landing zones” of the target arteries and balloon expandable bridging stent graft sizes. The coeliac axis, superior mesenteric artery (SMA), and main right and left renal arteries are targeted. If there is a further large renal artery, a stent graft could be customised to include five fenestrations, but generally smaller accessory renal arteries are covered. This results in a higher rate of renal infarcts but no significant reduction of eGFR on follow-up or type II endoleaks related to the renal artery.  The commonly used bridging stent grafts start at 5mm diameter, so renal arteries with a diameter of less than 4mm are unlikely to achieve a durable result free from occlusion. Indeed, renal artery stents are the most likely visceral target to occlude during follow-up, with a higher rate following BEVAR than FEVAR.
Challenging target artery anatomy also includes ostial stenoses and a decision can be made to pre-stent problematic stenoses. Pragmatic decisions of achieving a seal versus not covering an early branch of a target visceral artery are made. Figure 1 demonstrates a chronic dissection flap that extends into the left renal artery. Extension of the bridging stent to the renal artery bifurcation was required to achieve a seal and a branch did not need to be covered.
Figure 1a, b, c: Demonstrates a chronic dissection flap that extends into the left renal artery. Extension of the bridging stent to the renal artery bifurcation was required to achieve a seal and a branch did not need to be covered.
The angulation of the target artery should be taken account of at the planning stage so that vessels can be efficiently cannulated.
Figure 2a, b: Illustrates an upward-facing renal artery arising close to the aortic bifurcation. A customised endo graft with an upward-facing inner branch was planned.
Careful planning of the FEVAR/BEVAR endo graft and selecting the appropriate adjunctive equipment, such as sheaths and bridging stent grafts, can facilitate successful outcomes in challenging anatomy.
St Mary’s Hospital, London/GB
Dr. Ondina Bernstein is a consultant interventional radiologist and head of interventional radiology at St Mary’s Hospital, Imperial College Healthcare in London. She completed a clinical and research fellowship in University Health Network and Mount Sinai Hospital in Toronto and undertakes vascular and oncology interventional radiology. She is on the specialty training board and curriculum committee at the Royal College of Radiologists.
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