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Where now for Endovascular Repair of Ruptured AAA?

Open ArchivePublished:May 20, 2015DOI:https://doi.org/10.1016/j.ejvs.2015.03.040
      The ECAR study is the third randomised trial that has failed to demonstrate any survival advantage for patients with ruptured AAA treated by an endovascular stent-grafting technique. Although of different designs, both IMPROVE

      IMPROVE Trial Investigators, Powell JT, Sweeting MJ, Thompson MM, Ashleigh R, Bell R, Gomes M, et al. Endovascular or open repair strategy for ruptured abdominal aortic aneurysm: 30 day outcomes from IMPROVE randomised trial. BMJ;348:f7661.

      and the Amsterdam aneurysm study
      • Reimerink J.J.
      • Hoornweg L.L.
      • Vahl A.C.
      • Wisselink W.
      • van den Broek T.A.
      • Legemate D.A.
      • et al.
      Amsterdam Acute Aneurysm Trial Collaborators
      Endovascular repair versus open repair of ruptured abdominal aortic aneurysms: a multicenter randomized controlled trial.
      essentially came to the same conclusion of no overall mortality benefit. The randomised controlled trial findings conflict with those of the numerous cohort studies, which have demonstrated a survival benefit for EVAR.
      • van Beek S.C.
      • Conijn A.P.
      • Koelemay M.J.
      • Balm R.
      Endovascular aneurysm repair versus open repair for patients with a ruptured abdominal aortic aneurysm: a systematic review and meta-analysis of short-term survival.
      In attempting to explain these conflicting findings, the most important factor appears to be patient selection. A recent meta-analysis identified that although EVAR conferred a significant benefit over open repair in most cohort studies, these studies were at a high risk of bias.
      • van Beek S.C.
      • Conijn A.P.
      • Koelemay M.J.
      • Balm R.
      Endovascular aneurysm repair versus open repair for patients with a ruptured abdominal aortic aneurysm: a systematic review and meta-analysis of short-term survival.
      More specifically, patients are often assigned to EVAR when haemodynamically stable and with favourable aortic anatomy, introducing a well-defined selection bias.

      Ambler GK, Twine CP, Shak J, Rollins KE, Varty K, Coughlin PA, et al. Survival following ruptured abdominal aortic aneurysm before and during the IMPROVE Trial: a single-centre series. Eur J Vasc Endovasc Surg;47(4):388–393.

      Randomised trials in the emergency setting are difficult to design and conduct. The ECAR study has a number of important limitations that reduce its overall impact. The patients randomised in the trial were a highly selected cohort of the overall population of patients presenting to trial centres with a rAAA. In fact only 20% of patients, those who were haemodynamically stable and anatomically suitable for EVAR, were randomised. The interventions and outcomes of the majority (80%) including those who were not offered any intervention were not reported. In this highly selected group it could have been anticipated that outcomes would be good, and therefore basing the power calculation on a 40% open repair mortality is hard to justify. This combined with the failure to complete recruitment, resulted in the ECAR study being underpowered.
      It is also worth considering why centres failed to recruit. Certainly the entry criteria (stable and EVAR-friendly anatomy) were restrictive, and ruptured AAA appears to be a waning disease, but were there other reasons? The impact of the lenient credentialing of trial centres in the ECAR may have influenced patient outcomes. Patients waited some considerable time (2.9 hours) to receive an EVAR compared with open repair (1.3 hours), and almost three-quarters of patients were treated with an AUI EVAR configuration (despite their stability), suggesting that centres may not have been as expert in delivering emergency EVAR as they were with open repair.
      The principal factor-influencing outcome of RAAA appears to be aortic anatomy. Evidence from Dick et al.
      • Dick F.
      • Diehm N.
      • Opfermann P.
      • von Allmen R.
      • Tevaearai H.
      • Schmidli J.
      Endovascular suitability and outcome after open surgery for ruptured abdominal aortic aneurysm.
      suggests that outcomes for open repair are significantly better in those patients who are anatomically suitable for EVAR, and furthermore suggests that borderline anatomical suitability confers improved outcomes over patients who are not suitable for EVAR. The recent data from IMPROVE
      • IMPROVE Trial Investigators
      The effect of aortic morphology on peri-operative mortality of ruptured abdominal aortic aneurysm.
      reported that infra-renal neck length is an important factor affecting outcome after RAAA surgery. It is not wholly surprising that a longer neck confers advantages, not only in those patients undergoing REVAR but also in those undergoing open repair by providing a suitable infra-renal clamp site.
      So, if, as the randomised trials suggest, EVAR confers no mortality benefit over open repair in anatomically suitable patients, then do any patients benefit from EVAR? IMPROVE suggests that females (and those undergoing EVAR under local anaesthesia) may have better outcomes. There is, however, another group who may potentially benefit from EVAR - those patients previously offered no intervention for their ruptured AAA. This group is difficult to define, as “turn down rates” are often not reported, and account for over 40% of patients presenting with ruptured AAA in the UK.
      • Karthikesalingam A.
      • Holt P.J.
      • Vidal-Diez A.
      • Ozdemir B.A.
      • Poloniecki J.D.
      • Hinchliffe R.J.
      • et al.
      Mortality from ruptured abdominal aortic aneurysms: clinical lessons from a comparison of outcomes in England and the USA.
      Evidence from cohort studies suggests that EVAR is offered to older patients who otherwise may not be offered any intervention.
      • Noorani A.
      • Page A.
      • Walsh S.R.
      • Varty K.
      • Hayes P.D.
      • Boyle J.R.
      Mid-term outcomes following emergency endovascular aortic aneurysm repair for ruptured abdominal aortic aneurysms.
      And offering intervention to a greater proportion of patients presenting with ruptured AAA will have the greatest impact on reducing overall mortality rates. Delivery of an effective 24/7 emergency EVAR service in vascular centres is going to be a key component in delivering improved outcomes for patients presenting with ruptured AAA.

      References

      1. IMPROVE Trial Investigators, Powell JT, Sweeting MJ, Thompson MM, Ashleigh R, Bell R, Gomes M, et al. Endovascular or open repair strategy for ruptured abdominal aortic aneurysm: 30 day outcomes from IMPROVE randomised trial. BMJ;348:f7661.

        • Reimerink J.J.
        • Hoornweg L.L.
        • Vahl A.C.
        • Wisselink W.
        • van den Broek T.A.
        • Legemate D.A.
        • et al.
        • Amsterdam Acute Aneurysm Trial Collaborators
        Endovascular repair versus open repair of ruptured abdominal aortic aneurysms: a multicenter randomized controlled trial.
        Ann Surg. 2013; 258: 248-256
        • van Beek S.C.
        • Conijn A.P.
        • Koelemay M.J.
        • Balm R.
        Endovascular aneurysm repair versus open repair for patients with a ruptured abdominal aortic aneurysm: a systematic review and meta-analysis of short-term survival.
        Eur J Vasc Endovasc Surg. 2014; 47: 593-602
      2. Ambler GK, Twine CP, Shak J, Rollins KE, Varty K, Coughlin PA, et al. Survival following ruptured abdominal aortic aneurysm before and during the IMPROVE Trial: a single-centre series. Eur J Vasc Endovasc Surg;47(4):388–393.

        • Dick F.
        • Diehm N.
        • Opfermann P.
        • von Allmen R.
        • Tevaearai H.
        • Schmidli J.
        Endovascular suitability and outcome after open surgery for ruptured abdominal aortic aneurysm.
        Br J Surg. 2012; 99: 940-947
        • IMPROVE Trial Investigators
        The effect of aortic morphology on peri-operative mortality of ruptured abdominal aortic aneurysm.
        Eur Heart J. 2015 Jan 27; (pii: ehu521. [Epub ahead of print])
        • Karthikesalingam A.
        • Holt P.J.
        • Vidal-Diez A.
        • Ozdemir B.A.
        • Poloniecki J.D.
        • Hinchliffe R.J.
        • et al.
        Mortality from ruptured abdominal aortic aneurysms: clinical lessons from a comparison of outcomes in England and the USA.
        Lancet. 2014; 383: 963-969
        • Noorani A.
        • Page A.
        • Walsh S.R.
        • Varty K.
        • Hayes P.D.
        • Boyle J.R.
        Mid-term outcomes following emergency endovascular aortic aneurysm repair for ruptured abdominal aortic aneurysms.
        Eur J Vasc Endovasc Surg. 2012; 43: 382-385

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