Key points from the evidence
Scottish Health Technologies Group (SHTG)
- Abdominal aortic aneurysms (AAA) develop below the renal arteries of the aorta. Aneurysms that develop above the renal arteries are called thoracic aortic aneurysms (TAAs). Aneurysms that extend from the thoracic section of the aorta into the abdominal section of the aorta are called thoracoabdominal aneurysms (TAAAs). Complex aneurysms involve the branches of the aorta, for example the arteries to organs such as the kidney, liver and bowel. This review is focused on the use of C-EVAR to treat complex AAAs and TAAAs.
- SHTG advice from 2018 stated that C-EVAR was a novel treatment associated with limited and low-quality evidence. Several systematic reviews have been published since 2018, yet the uncertainties in the evidence about its benefits remain.
- Systematic reviews which compare outcomes following C-EVAR or OSR all report concerns around the quality of the evidence base. The published literature consists of observational studies within which patient cohorts are often unlikely to be comparable in terms of urgency of treatment (elective/non-elective), aneurysm anatomy, risk profile and other demographics.
- Guidelines from the National Institute for Health and Care Excellence (NICE) in 2020 summarised nine studies comparing C-EVAR with OSR for the treatment of people with unruptured AAAs. NICE reported that C-EVAR was associated with a shorter procedure time, shorter in-hospital stay, fewer perioperative cardiovascular complications, and a greater chance of discharge to home (as opposed to another hospital or residential care). However, mortality in people who survive the perioperative period was greater in people treated with C-EVAR techniques. NICE reported that C-EVAR and OSR could not be differentiated with regard to perioperative mortality, perioperative complications, duration of critical care and reintervention rate. No evidence was identified comparing the efficacy of EVAR with OSR of ruptured complex AAA.
- A systematic review, with network meta-analyses (NMA), from 2022 compared treatments for the repair of complex AAA, focusing on juxtarenal aortic aneurysms (JRAA). The interventions evaluated were OSR, fenestrated EVAR (F-EVAR), EVAR with adjuncts (including chimneys and endo-anchors), as well as off-label use of standard EVAR. Twenty-four studies were reviewed including 15 that had been excluded from the NICE review because of quality concerns. In contrast to the NICE review, the authors concluded that there is a perioperative survival benefit for off-label EVAR and F-EVAR compared with OSR, potentially as a result of reduced risk of myocardial infarction (MI). There was no statistically significant difference in perioperative mortality between OSR and chimney-EVAR (Ch-EVAR). The authors note that F-EVAR carries a greater mid-term reintervention risk than OSR, which would have implications for costs and cost effectiveness. Other systematic reviews, in which the evidence base overlapped, similarly reported that F-EVAR and branched-EVAR (B-EVAR) were associated with reduced perioperative mortality, but higher reintervention rates.
- Five systematic reviews focused specifically on the repair of TAAAs (not included in the NICE guidelines). All reported that a lack of good quality evidence prevented definitive conclusions on the optimal surgical intervention for this cohort of patients. Some reviews suggested possible advantages of C-EVAR over OSR in terms of short-term outcomes, including perioperative mortality, and possibly increased reintervention rates. The conclusions reported in the systematic reviews were not consistent.
- C-EVAR costs more than OSR or standard EVAR. The cost of the stent graft for C-EVAR is £12,000–£30,000 in the UK depending on the device used. NICE cost-utility analyses found that for patients with complex AAAs, who are fit for OSR, C-EVAR costs more than OSR, but generates more quality-adjusted life years (QALYs). While there is uncertainty about the magnitude of survival gains, C-EVAR devices are often custom made and invariably more expensive, to the extent that C-EVAR is unlikely to be cost effective at conventional thresholds. NICE also reported that C-EVAR cost more and generated less benefit than a no surgical intervention strategy in patients not fit for OSR.
- High-volume hospitals where surgeons perform a higher number of procedures are associated with lower levels of perioperative mortality. A policy document from NHS England recommends that providers of these techniques should have a projected annual case load of at least 100 aortic procedures, and in excess of 24–30 C-EVAR cases to maintain high levels of expertise in all professionals involved in the care pathway. On this basis, in Scotland, where procedure numbers remain less than 50 per year, C-EVAR should be delivered from a small number of centres, or one centre.
- C-EVAR is currently conducted in five health boards in NHSScotland. The most complicated cases are referred to the national specialist TAAA service in the Royal Infirmary of Edinburgh, NHS Lothian. This service offers both open and endovascular treatment for patients with diseases of the aortic arch, thoracic, thoracoabdominal or suprarenal abdominal aorta and other complex aortic conditions. As this is a specialist service, C-EVAR delivered here is funded by NSD. C-EVAR delivered from the other NHS boards in not funded by NSD.