Endovascular Repair of rAAA (rEVAR) versus Open Repair (OR), a Contemporary Comparison of the Paradigm Shift in Rupture AAA Management: Leading Vascular Surgery Expert Sherif Sultan, MD

Editorial – Sherif Sultan, MD, FRCS, FACS, PhD

Sherif Sultan, MD FRCS FACS PhD 1, 2; Patrick Canning MB BCH1; Edel P Kavanagh, BSc PhD1,2; Wael Tawfick MS, MRCS1;  Niamh Hynes, MD MRCS1,2

  • 1Western Vascular Institute, Department of Vascular and Endovascular Surgery, University College Hospital Galway, Newcastle road, Galway, Ireland
  • 2Department of Vascular and Endovascular Surgery, Galway Clinic, RCSI, Dublin Road, Galway, Ireland

Corresponding author: Professor Sherif Sultan, Professor of Vascular & Endovascular Surgeon, Western Vascular Institute, Department of Vascular & Endovascular Surgery, University College Hospital Galway, Ireland;

Telephone: +35391 720121. Fax: +35391720122. Email: sherif.sultan@hse.ie

Abstract

The overall number of abdominal aortic aneurysm repairs has increased by 65% over a 10-year period but the absolute number of ruptured abdominal aortic aneurysms has declined by 24%. Para-millennium contemporary trends in the management of abdominal aortic aneurysms have shown an increase in elective endovascular repair due to screening programs, and the minimal-invasiveness of the technology, which allows for high patient turnover rates. One could also argue that by reducing operative risk, EVAR has lowered the threshold for intervention and even when managing older and sicker patients, EVAR provides an absolute mortality reduction of 37% over open repair. The experience gained with EVAR and its clear advantages over open repair, have been successfully translated from the elective to the emergency setting, although the change in circumstances, in themselves demand a fresh look at the comparison between endovascular and open repair in the event of aortic rupture.

Introduction

While there has been a rapid uptake of endovascular aortic repair (EVAR) for elective abdominal aortic aneurysm (AAA) repair, this paradigm shift is not evident with ruptured AAA (rAAA).1 Systematic reviews and population based studies found mortality, and post-operative complications to be reduced in patients undergoing ruptured EVAR (rEVAR) compared to ruptured open surgical repair (rOSR) of rAAA.1-3 However, there was concern over patient selection and publication bias, leading to the need for randomized controlled trials in this area.2

Two randomized controlled trials (RCTs), the IMPROVE trial (The Immediate Management of the Patient with Ruptured Aneurysm: Open versus Endovascular Repair) and the AJAX trial (Amsterdam Acute Aneurysm) both showed no difference in all-cause mortality, combined death and severe complications, respectively.4,5 Due to the similarity in clinical outcomes between both patient groups, we would argue that cost-effectiveness should be a focal point in the treatment decision of rAAA.

Cost-effectiveness remains a divided area in the literature. Retrospective studies have found rEVAR to be both cost-effective and equivalent to rOSR, with the two RCTs coming to contradictory conclusions.6,7 The IMPROVE trial found rEVAR to be cost-effective, while the AJAX trial found rEVAR to be, ‘unaffordable based on current standards of societal willingness-to-pay for health gains.4,5 The mechanisms of injury post rAAA are hemorrhagic shock and lower torso ischemia. Both lead to reperfusion injury on revascularization and initiate systemic inflammatory response syndrome (SIRS), leading to multiple organ dysfunction syndromes (MODS), which is the  primary cause of mortality in 75% of patients.4,5 REVAR role in ameliorating the risk of progression to MODS, could be the main factor that determines its value in patients with aortic rupture.

A number of questions arise with regard to treating rAAA: Which patients are going to die from other factors before they benefit from emergency AAA repair?; What price are patients willing to pay for quality of life?; In economic terms, how much is the healthcare system disposed to invest for the optimal AAA treatment?. Time has lagged and as a result, it has halted the advancement in technology. Endograft designs and material, and pharmacological manipulation all are challenging opportunities in rAAA management. However, rEVAR for rAAA has a pragmatism rule that cannot be measured for patients. The null hypothesis for this review was that rEVAR as the primary modality for rAAA is achievable, appears to be associated with favourable mortality versus open repair, and is ultimately cost-effective.

Surgical Technique

Interventions for rupture AAA are not strictly consistent between vascular units. However within a given unit, it is vital that a uniform approach is invariably undertaken, in as much as is feasible. This allows for excellent team dynamics and streamlined efficient life-saving approach.

In our unit, immediately after CT scanning is performed an experienced endovascular team make the ultimate decision on suitability, after evaluating the suitability for rEVAR. We routinely have on the shelf, a standard set of aorto-uni-iliac or bi-iliac endovascular grafts from a multiple different manufacturers, and mix and match as we see fit after viewing patient anatomical images using a 3D imaging tool: TeraRecon until 2007 (Foster City, California, USA), and 3Mensio from 2008 to present (Pie Medical Imaging BV, Maastricht, The Netherlands).

The infra-renal aortic neck cranial to the aneurysm must have a diameter of 20-33mm and a length of at least 5mm. Severe neck angulation is rarely a contra-indication to EVAR due to our experience in the DRESS technique, enabling us to overcome what would normally be considered as a challenge for EVAR implementation. This technique included the deployment of 5 or 6 extra-stiff guide-wires, (Lunderquest. Cook, Indianapolis, USA), across the aneurysm neck to straighten severe angulation, and facilitate the graft deployment. Another step usually needed to ensure proper proximal seal and fixation of the graft in cases with short severely angulated neck, is the deployment of a PALMAZ stent (Cordis Corporation, Florida, USA). This is a stainless steel, expandable, wire-mesh tube stent mounted over a Coda balloon across the renal arteries, before deployment of neck extensions or the graft main body. This greatly insures the stability of the graft against migration, and achieves proper seal with a short angulated neck. Any iliac artery can accommodate the endovascular graft by utilizing endo-paving and cobbling techniques. We cover the internal iliac artery and land in the external iliac in cases of common or internal iliac aneurysms.

The suprarenal balloon (Reliant, Medtronic, Minneapolis, Minn; CODA, Cook, Indianapolis, USA) is placed above the level of the renal arteries during manipulation of the endovascular device only if signs of intra-operative hemodynamic instability develop, and is withdrawn immediately before stent graft deployment. The Coda or Reliant occlusion balloon is used to gain immediate proximal control supported by an 18 French sheath (Cook, Indianapolis, USA) to prevent downgrade balloon displacement, followed by deployment of an aorto-iliac device. For patients in whom the aortic anatomy is not amenable to rEVAR, the intra-aortic occluding balloon is left in place in the proximal aorta above both renal arteries to arrest ongoing bleeding. A standard open surgical cross-clamp placement and repair is performed with a Dacron tube graft.

We deem rEVAR the treatment of choice because the aneurysm sac can be controlled immediately under local anesthesia. This retains the contribution of the anterior abdominal musculature that gives tamponade to the hematoma, which is lost when muscle relaxant is given. All procedures OSR/EVAR are performed with intravenous unfractionated heparin and all patients are maintained on aspirin post operation. EVAR patients undergo a control aortic duplex scan and plain film x-ray of the abdomen to document the location of the graft on day one post operation, at six weeks and then six monthly intervals thereafter. Computered Tomography (CT) scan follow up is performed if the duplex scan shows any sign of endoleak or sac expansion, or if follow up x-ray shows graft migration. OSR patients have an ankle brachial index performed at the same time points.

 

State of the Art, rEVAR versus OR

Literature on randomized controlled trials for rEVAR is insufficient. The Nottingham Trial was abandoned due to on table technical problems by the performing teams, which resulted in a high mortality rate.8 The Ajax Trial, an Amsterdam based trial showed no difference between the two arms recruited; moreover it was extended twice since 2007.9 However, they used AUI and fem-fem cross over for all the EVAR patients, and the 7 referring centers operated on the same number that were randomized to either group. So patients who theoretically could most benefit from rEVAR were excluded. The ECAR Trial; a Paris based study only randomized the most stable EVAR suitable patients and is still ongoing.10 The IMPROVE Trial, a UK based trial, which started in summer 2009, aimed to show a drop in OR for rAAA from 45% to 30%, by having a CTA first approach.11 Such an approach may lead to a type II error, delineating the anatomy of patients and favor OR. Moreover, the technical unavailability of out of hours radiologists in some UK hospitals would lead to skewing towards OR. However, the IMPROVE trial, all rupture AAA RCTs are designed to recruit the most stable EVAR suitable patients and circumnavigate “the ethical dilemma of randomization of the unstable patient”. The study was conducted in 29 centers in the UK, with only one center from Canada enrolling patients. This trial is therefore constrained by the health system in which it was conducted and any results must be explicitly contextualized by the authors. This trial has little scope for international application.

There is no doubt that the IMPROVE trial was carefully planned and much useful information has been collected, but the conclusions made by the authors are not supported by the data. Furthermore, there are several issues relating to the trial design and interpretation of results that lead to a miscommunication of the actual findings, and make it difficult to relate the findings to other countries. This is particularly important because it is a pragmatic trial of a treatment algorithm rather than a direct comparison of treatment modalities/surgical techniques i.e., EVAR for rupture AAA versus open repair for rupture AAA. These issues need to be clarified because a misinterpretation of this data could lead to a valid life-saving treatment being inappropriately withheld from patients.

The IMPROVE trial sponsors requested that the primary outcome measure be all-cause mortality rather than aneurysm related mortality. The all-cause mortality may not differ much from the aneurysm-related survival as a 30-day outcome, but it may certainly have a meaningful impact on more long-term time points, especially in this elderly patient cohort that historically have considerable co-morbidities. A review of the statistical power is warranted based on the fact that the actual enrollment was almost 100 less than the 600 the trial was powered to assess, and the fact that there was a large crossover rate. In light of this large crossover between groups, which was independent of anatomical suitability, a per protocol analysis is necessary to give the trial some international context, even if it is just to validate the investigators intention to treat analysis. This is necessary especially considering that overall in the two randomized groups, taken together, the 30-day mortality for rAAA patients actually treated by EVAR was 24.7% (46 of 186), and for those actually treated by open repair, was 38.1% (128 of 336; p <0.002).4 However, an acknowledgment must be made when doing a per protocol analysis that the protocol used in the IMPROVE trial reflects UK practice and does not translate to a vast proportion of international vascular units.

rEVAR costs were higher in IMPROVE, considering the fact that most international centers do not require two specialist teams to undertake a ruptured aneurysm repair by open or endovascular means. At time of hospital discharge the cost disparity between two different “treatment algorithms” holds some validity but by one year the cost of interest is more a factor of treatment modality rather than the initial care pathway. Therefore, a per treatment cost-analysis is useful and of more concern to clinicians who are trying to justify enhanced use of EVAR for rAAA to their trust managers and/or their Chief Financial Officers. Those in charge of healthcare budgets cannot afford to be pragmatic and bottom line costs are of far more interest.

The IMPROVE trial is worthwhile and provides very useful information about the management of ruptured AAA and exposes several flaws in the way that vascular units are run in the UK, most notably the lack of unification between vascular and radiology specialists. A specialist trained in both open and endovascular repair will alleviate the “operational” issues that preclude patients suitable for EVAR being denied this treatment, and it would also reduce costs further. This is a valid finding of the trial, which will serve to positively influence training and the future provisions of vascular services.

The main conclusion of the IMPROVE trial at one year is not supported by its data. This conclusion that “an endovascular first strategy for management of ruptured aneurysms does not offer a survival benefit over 1-year” is misleading because more than half (162 of 316) the patients randomized to the endovascular strategy group did not actually undergo treatment by EVAR. This invalidates any intention-to–treat analysis and prevents the trial from providing useful level 1 evidence regarding mortality for the two rAAA treatments. The use of all-cause rather than aneurysm related mortality further reduces the validity of this outcome at one year and later time points. It does not constitute true level 1 evidence, and so a more accurate conclusion justified by IMPROVE’s data would be: In patients with a rAAA, if they can be treated by EVAR, their one-year survival will be superior to that of patient’s treated by OR. The superiority of EVAR, if it can be performed for the treatment of rAAA, is further supported by the decreased proportion of rAAA patients that receive no corrective treatment when EVAR is utilized, compared to when open treatment is being used.

We are witnessing a declining incidence of clinically relevant AAA. Nevertheless, there is an increase up to 80% of patients undergoing rEVAR in EVAR first centers. The 30-day mortality is decreasing fast to 20-35%.3 Moreover centers that introduced the rEVAR first algorithm have witnessed a total reduction in 30-day mortality (OR and EVAR) from 58% to 35%.12 In our unit, by 2011, we had 100% EVAR first policy for all rAAA.

A direct comparison between rEVAR and OR for rAAA is challenging, since not all patients are anatomically appropriate for on the shelf endo-grafts. We matched a control with two groups using the 3-point scale of the SVS Anatomic Risk scores and SVS Global score for risk of morbidity and mortality after rEVAR. There was no statistical difference between the two groups, however rEVAR patients were older and sicker. The patients who benefited most from rEVAR were those who were unstable and theoretically unsalvageable. Patients stable enough for CT-scanning are already a self-selecting group compared to those that are in extremes and cannot wait for imaging. In our unit, a rEVAR first strategy to all of our patients allowed us to salvage the sickest patients where all the benefit had been substantiated, which highlights the importance of real life scenario rather than the controlled environment of a randomized controlled trial.5

Foster et al. concluded that no observational study showed any superiority of OR over rEVAR with reference to mortality or morbidity.11 However, they found two studies that had shown equivalence in mortality, and 24 studies with improved 30-day survival with rEVAR, which depicts our finding. On the contrary, Saqib et al., purported that endovascular repair for rAAA does not seem to conclusively confer either acute or late survival advantages over open repair.13 The leading body of evidence is found in a co-operative multicentre cohort study reported by Veith et al., spanning 49 institutions in 13 countries.3 This confirmed superiority of rEVAR over OR in terms of 30-day mortality (19.7% rEVAR versus 36.3% OR; P=0.0001).7

A structured rEVAR-first protocol by Starnes et al. resulted in a 60% drop in overall 30-day mortality from 54.2% to 18.5%.12 Mehta et al. reported 18% mortality for rEVAR patients, which is 50% less than OR.14

In the Amsterdam Acute Aneurysm Trial, a prospective cohort of all patients with a rAAA, the suitability for endovascular repair in patients with a rAAA confirmed on CTA was 45.8%, but the application rate was lower. Forty-six patients were operated on in the referring centers, which equate to the same number in both arms. In our unit, over 10 years, the mean suitability was 35%. If suitability was focused on a 3-year period from 2009-2011, suitability for rEVAR was 85%. Nevertheless, the percentage of patients presenting with rAAA with favorable anatomy suitable for rEVAR is between 46% and 81%.11 This percentage is likely to increase as advances continue in stent graft technology and manufacturing, in addition to better imaging and 3D software tools.9,15,16

 

rEVAR First Approach

Implications of a rEVAR-first approach for all ruptures will concentrate its management in high deliberate practice volume centers. The first corner stone in our protocol is hypotensive hemostasis, which allowed the majority of our patients to arrive in theatre in a salvageable state. This is echoed by findings in a study by Reimerink et al., in which the authors suggest that withholding a fluid challenge in patients with rAAA will promote better outcome.16 Veith et al., found that systolic arterial pressures of 50 to 70 mm Hg are well tolerated for short periods and limit internal bleeding and its associated loss of platelets and clotting factors.17

In our unit, the suprarenal balloon is placed above the level of the renal arteries during manipulation of the endovascular device only if signs of intra-operative hemodynamic instability develop. It is withdrawn immediately before stent graft deployment and provides the necessary control over hemodynamic instability. However, Veith el al., stated that deflation of the balloon before sealing of the rupture site will result in immediate recurrence of the circulatory collapse.17 They recommended the use of multiple balloons to minimize renal and visceral ischemia by placing secondary balloons within the endograft as the supraceliac balloon is deflated and removed through its supporting sheath.17 Berland et al., suggested this technique to be accomplished with a sheath-supported compliant balloon, inserted via the groin contra-lateral to the side to be used for insertion of the endograft main body.18 After the main body is fully deployed, a second balloon is placed within the endograft, and the first balloon is removed so that extension limbs can be placed in the contra-lateral side.18 A third balloon can be placed via the contra-lateral side and ipsilateral extensions deployed as necessary.18

In our experience of the implementation of a round the clock rEVAR program, although a logistic challenge in terms of medical manpower in an economic down turn, was solved by training all vascular surgeons from 2002-2005 to perform using an endovascular technique, in all cases that were suitable for rEVAR. Early in our unit, only one surgeon was performing rEVAR. With more surgeons gaining experience in the use of rEVAR, it has increasingly moved to the forefront in the treatment of rAAA.

Our protocol is 100% endovascular approach for all ruptures, except if it is anatomically impossible to perform. The fact that we are well equipped as a large volume tertiary center with high numbers of referrals, and that we have a vast experience in elective EVAR with highly trained endovascular surgeons, provides us with different tools to overcome challenges in the implementation of the EVAR technique in cases considered elsewhere to be unsuitable. Our experience with different types of grafts, technical skills to overcome anatomically challenging cases with the DRESS technique, the availability of on the shelf grafts with different sizes, and the ability to mix and match according to the circumstantial requirements, has led to abolition of the potential for selection bias. With experience and advancing endovascular skill, in our unit, we have been able to drop our 30-day mortality rate from 41% to 20 % by December 2011.

Hinchcliffe et al., highlighted that lack of CT scanning prior to surgery instigates harm to the patients, and fails to define the role of an endovascular first strategy.2 This concurs with our philosophy that patients who access the hospital alive, anatomical suitability can be assessed by CTA. Currently, with our Hybird Endosuite (Philips, Allura, Germany), the patient is able to complete the entire journey of management of rAAA in theatre from diagnosis to intervention.

The debate on whether to use a bifurcated or an aorta-uni-iliac stent was settled when our protocols put the first choice of bifurcated graft in 2008.19,20 Previously, choice of an aorto-uni-iliac endovascular graft was made because of technical ease. Now there is an increased availability of six different grafts (Endurant (Medtronic, Santa Rosa, ca), AFX (Endologix (Irvine, CA), Excluder (Gore medical Flagstaff, AZ) Jotec (Hechingen, Germany), Cook (Bloomington, IN), Incraft (Cardinal Health, Dublin, OH) a mix and match policy, and a wide range of choices to serve all of our AAA patients. This negates the complications of the femoro-femoral bypass, such as thrombosis and infection.20

Lesperance et al., in their publication regarding the disparities in outcomes from a nationwide perspective in USA echoed our unit, that rEVAR is increasingly used with steadily decreasing mortality and improved outcomes, compared with OR.20 However, results in non-teaching centers are substantially worse than those in teaching hospitals.20 The latest does apply to our practice as all major vascular interventions are done in deliberate practice volumes centres.21 We agree that high-volume surgeons confer a significant survival benefit, as volume increases proficiency.22 Furthermore, a nationwide adoption of rEVAR in the USA documented a lower postoperative mortality than OR with higher elective AAA, and increased the mortality advantage for rEVAR. These results support regionalization of rAAA repair to high volume centers whenever possible, and a wider adoption of EVAR for rAAA.23 A Canadian study by Moore et al., showed a substantiated mortality benefit for rEVAR protocol with 30-day mortality reduction from 30% before the protocol to 17.9% after the protocol was instituted.24 Interestingly, this study showed a trend toward improved mortality for hemodynamically unstable patients who underwent rEVAR rather than OR.

Davenport et al., in their 30-day National Surgical Quality Improvement Program (NSQIP) outcomes for rAAA, illustrated a lower 30-day morbidity risk, a decrease in transfusion requirements, ICU and hospital stay for rEVAR versus OR.25 Mehta et al., revealed that rEVAR compared with OR of rAAA not only significantly reduces 30-day mortality (24% rEVAR versus 44% OR; P=<0.005), but also improves long-term cumulative survival at 5 years (37% rEVAR versus 26% OR; P=<0.005).26

Hynes et al., conducted a prospective clinical, economic, and quality-of-life analysis comparing EVAR, OR, and best medical treatment in high-risk patients with AAA. The authors concluded that EVAR, as a “one-time procedure,” substantially reduces operative morbidity, hospital stay, costs, and utilization of intensive care facilities, if performed in a high-volume center. The authors calculated a mean cost per patient of €18,476 for EVAR and €24,252 for OR, a savings of €5,776 per patient treated with EVAR. In our unit, the mean quality adjusted life years for rEVAR was significantly greater than OR.

 

CONCLUSION

rEVAR as the primary modality in management of rAAA is achievable and practical. Literature shows that rEVAR performed better with encouraging lower 30-day mortality and long-term survival over OR, in suitable cases. The mortality for rAAA is still high and unacceptable regardless of the mode of intervention. We believe that an active mandatory screening program supported by the government will improve the outcome and would save a number of lives lost in health expenditure cutbacks.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Conflict of interest

None of the authors have any financial arrangement or other relationship that could be construed as a conflict of interest.

References

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Manish Mehta, MD, MPH, Jeffrey C, Hnath, MD.  Lessons Learned in Offering EVAR for Ruptured Aneurysms, Important considerations to improve outcomes.