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Extended use of endovascular aneurysm sealing for
ruptured abdominal aortic aneurysms
Dittmar Böckler
a,n, Andrew Holden
b, Dainis Krievins
c, Jean-Paul P.M. de Vries
d,
Andreas S. Peters
a, Philipp Geisbüsch
a, and Michel Reijnen
eaDepartment of Vascular and Endovascular Surgery, University of Heidelberg, Im Neuenheimer Feld 110, 69120
Heidelberg, Germany
bAuckland City Hospital, Auckland, New Zealand cStradins University Hospital, Riga, Latvia
dSt. Antonius Hospital, Nieuwegein, The Netherlands e
Rijnstate Hospital, Arnhem, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Endovascular repair of abdominal aortic aneurysms (EVAR) is now an established treat-ment modality for suitable patients presenting with aneurysm rupture. EVAR for ruptured aneurysms reduces transfusion, mechanical ventilation, intensive care. and hospital stay when compared with open surgery. In the emergency setting, however, EVAR is limited by low applicability due to adverse clinical or anatomical characteristics and increased need for reintervention. In addition, ongoing bleeding from aortic side branches post-EVAR can cause hemodynamic instability, larger hematomas, and abdominal compartment syn-drome. Endovascular aneurysm sealing, based on polymerfilling of the aneurysm, has the potential to overcome some of the limitations of EVAR for ruptured aneurysms and to improve outcomes. Recent literature suggests that endovascular aneurysm sealing can be performed with early mortality similar to that of EVAR for ruptured aortic aneurysms, but experience is limited to a few centers and a small number of patients. The addition of chimney grafts can increase the applicability of endovascular aneurysm sealing in order to treat short-neck and juxtarenal aneurysms as an alternative to fenestrated endografts. Further evaluation of the technique, with larger longitudinal studies, is necessary before advocating wider implementation of endovascular aneurysm sealing in the emergency setting.
& 2016 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1.
Introduction
In recent years, endovascular aneurysm repair (EVAR) has become the favored option to treat suitable patients with abdominal aortic aneurysms (AAA) electively in many centers worldwide. This evolution is based mainly on the multicenter
randomized trials: EVAR 1 (United Kingdom Endovascular Aneurysm Repair 1), DREAM (Dutch Randomized Endovascular Aneurysm Management), and OVER (Open Versus Endovascular Repair)[1–7].
EVAR also has been established as an complementary treat-ment option for ruptured AAA (rAAA) beside conventional
http://dx.doi.org/10.1053/j.semvascsurg.2016.09.002
0895-7967/$ - see front matter& 2016 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
nCorresponding author.
open repair. However, treatment, either open or endovascular, is still associated with significant mortality. A recently pub-lished meta-analysis reported overall mortality of 48.5%, and there was no decline in mortality over time[8,9]. Even in series performed at“Centers of Excellence,” mortality of EVAR for rAAA (rEVAR) is between 18.9% and 79%[10,11]. According to Baderkhan et al[12], aortic anatomy predicts mortality sig-nificantly. Nevertheless, the care of patients with rAAA remains challenging, but rEVAR carries a substantial oppor-tunity for improved survival and lower complications due to the less-invasive nature of EVAR compared with open repair (OR). However, published results from randomized trials showed no difference in 30-day mortality when comparing EVAR with OR[13–15]. A recently published Cochrane system-atic review stated that the results of these randomized con-trolled trials prove rEVAR to be a valid option in suitable patients, but failed to show superiority across the board[16]. Some single-center experience suggests that rEVAR is the best approach and applicable to all patients with rAAA if the chimney technique is used as an adjunctive measure[17].
There have been remarkable technological advancements in EVAR since Juan Parodi’s first procedure in 1991. Endovas-cular aneurysm sealing (EVAS) for example, based on poly-merfilling of the AAA sac, has evolved rapidly during the last 3 to 5 years. Published early experience is very promising, applying this technology not only to routine but complex morphologies[18–20]. Global experience has been collected in two registries, the Global Forward and EVAS US-IDE (Safety and Effectiveness Study of Endovascular Abdominal Aortic Aneurysm Repair Using the Nellixs System) trials[21]. The concept of EVAS may add benefits to patient care in the scenario of rAAA with the potential to overcome limitations of rEVAR, expand indications in patients morphologically not being suitable, and even to treat post-EVAR ruptures. Pre-liminary experience has been reported[22–24].
This article outlines recent limitations of rEVAR, discusses potential benefits of rEVAS, and presents the current experi-ence using Nellix in rAAAs.
2.
Facts and
figures on AAA rupture
The incidence of rAAA (Fig. 1) is estimated to be 10.6/100.000 patient-years[25]. The incidence decreased from 9.3 in 2000 to 2005 to 8.4 in 2006 to 2010, calculated per 100,000 population. A decrease in mortality from rAAA was reported for many countries, such as Sweden, England, and Wales [26]. From 1997, hospital admissions for rAAA have declined from 18.6 to 13.5 per 100,000 population, and mortality from rAAA in those aged at least 65 years has fallen from 65.9 to 44.6 per 100,000 population. Anjum et al [7]concluded that the reduction in incidence of rAAA since 1997 is attributable largely to changes in smoking prevalence and increases in elective AAA repair in those aged 75 years and older. Reite et al[27]investigated the epidemiology of rAAA in a defined Norwegian population. Incidence was 11.0 rAAA per 100,000 per year. The adjusted mortality rate was 7.5 per 100,000 per year. The overall 90-day mortality was 68% and 51% for the patients treated for rAAA. Parkinson et al [28] analyzed the rupture rate of untreated large AAAs in patients unfit for elective repair. Overall inci-dence of rAAA in patients with AAA 45.5 cm was 5.3% per year in his review. This represented cumulative yearly rupture rates of 3.5% in AAA 5.5 to 6.0 cm, 4.1% in AAA 6.1 to 7.0 cm, and 6.3% in AAA47.0 cm. In this population, the risk of death from causes other than AAA was higher than the risk of death from rupture, and the rupture rates of untreated AAA were lower than formerly described in the literature. The mortality of rAAA is still alarmingly high, especially if the patients who die before hospital admission or intervention are included in the computation of rAAA mortality. Karthikesalingam et al[29] reported in-hospital, all-cause mortality (pooled intervention and non-corrective treatment) of 53.1% in the United States and 65.9% in England. In the population-based Malmö Diet and Cancer Study, the acute mortality, defined as death before reaching a hospital or during thefirst admission, was 41% for ruptured thoracic aortic aneurysm and 34% for rAAA, respec-tively. In a small Finnish study[30], only 139 of 221 patients
(63%) with rAAA reached the hospital, and 111 (50%) even-tually underwent emergency surgery. When including the operative mortality, in total, 77% of patients with rAAA died.
3.
EVAR for rAAA
Potential benefits for an endovascular procedure over open repair are vessel control under local anesthesia, rapid achieve-ment of hemodynamic stability, permissive hypotension during the whole procedure, and selective aortic occlusion to reduce retroperitoneal bleeding. This can result in quicker operative time, less blood loss, and reductions in perioperative cardio-pulmonary morbidity and mortality, possibly resulting in improved 30-day mortality and improved long-term outcomes. EVAR for rAAA is equal to open surgical repair in terms of 30-day and 1-year mortality. There is no significant difference in mortality after primary rEVAR when compared with primary OP strategy in randomized controlled trials[31]and in national population-based studies[32].
Nevertheless, there is a consistent but not significant trend toward lower mortality with EVAR at 1 year[9]. There is also a trend toward better outcomes in women[13]. Hostile neck anatomy remains the biggest challenge for both treatment groups (OR and rEVAR) and affects outcomes [33,34]. The IMPROVE (Immediate Management of Patients with Rupture: Open Versus Endovascular Repair) trial demonstrated the correlation of adverse, hostile aneurysm neck anatomy and survival. Mortality at 30 days was 27.2% after rEVAR in the subset of patients with hostile neck anatomy compared with 13.9% with favorable anatomy. This effect was not sustained at 3 years (33% v 36 %).
There is considerable debate between EVAR and OR for the treatment of rAAA and it is timely to review what we know:
Mortality for rEVAR is not inferior to OR (IMPROVE trial 35% v 37%, AJAX [Amsterdam Acute Aneurysm] trial 21% v 25%)[14,15]. Immediate secondary outcomes definitively benefit with EVAR by reducing the need for mechanical ventilation and blood transfusion and reduced intensive care unit and hospital stay[35]. In-hospital reintervention rate is comparable between rEVAR and OR, but long-term reinterventions are more frequent with EVAR compared with OR (25% v 5%)[36,37]. Cost for EVAR devices in ruptures is high, but overall care is less costly. The AJAX trial[35]showed that rEVAR costs €5,306 more at 30 days, but, according to IMROVE, costs at 1 year are€1,435 less due to reduced length of stay[13,14].There are still several unmet needs in the endovascular treatment for patients with rAAA.
3.1. Procedural challenges
To assess EVAR anatomic suitability with computed tomog-raphy, hemodynamic stability is mandatory. Hostile necks require more adjunctive procedures to seal the aneurysm and to treat the patient. Antoniou et al[38]demonstrated a lower
intraoperative Type Ia endoleak rate of 9% in favorable, compared with 22% in hostile, necks (Po .001).
3.2. Anatomic suitability
Up to 80% of rAAAs are unsuitable for EVAR due to anatomic suitability and/or comorbidity[39]. Turndown rate is as high as 40% due to hostile neck anatomy and poor, limited iliac access[29]. It is well known that large AAA diameter neg-atively influences infrarenal neck length and/or shape and morphology.
Short aneurysm necks adversely influence mortality after OR of rAAA (30-day mortality: 43.4%), but also after EVAR, with a 30-day mortality of 8% in favorable necks compared with 23% in hostile necks[40].
Juxtarenal aneurysm ruptures are often unsuitable for standard EVAR and need either custom-made fenestrated devices (not routinely available in emergent situations) or chimney EVAR repair. This is still associated with a Type Ia endoleak rate up to 10% due to gutters and, therefore, not sealing the rupture site[41].
3.3. Endoleak and secondary interventions
It has been reported that larger AAA diameter, mostly observed in ruptured cases, is associated with higher reinter-vention rates[42].
3.4. Type II endoleaks in rAAA
Patent inferior mesenteric artery and lumbar arteries can cause ongoing active bleeding resulting in retroperitoneal hematoma and can, therefore, be problematic post-rEVAR compared with elective EVAR. Paralytic bowel obstruction, abdominal compartment syndrome, and prolonged hospital-ization may be sequelae of Type II endoleaks[33].
3.5. Potential role of EVAS in rAAA care
The Nellix device (Endologix, Irvine, CA) was developed with recognition that many of the complications of EVAR stem from inadequate isolation of the native aortic wall from pressurized blood flow. The Nellix platform utilizes polymer-filled polyurethane endobags surrounding balloon-expandable stents covered with expanded polytetra fluoro-ethylene and stabilizes the aneurysm sac by completely filling and sealing the blood flow lumen, hence the term, endovascular aneurysm sealing system (EVAS)[22,23].
With this background in mind and knowing procedural implantation steps being published earlier [24], there are potential advantages of EVAS in rAAA regarding eligibility of patients and procedural steps of endovascular repair (Fig. 2):
1. The Forward Global registry demonstrated that more complex anatomies were treated with Nellix/EVAS com-pared with other post-market registries, such as ENGAGE and GREAT (Fig. 3). Transferring this observation to the treatment of rAAA might allow a broader range of anato-mies within instructions for use (IFU) to be treated. In
combination with the chimney technique, even more patients with complex anatomy, especially short necks, might be suitable for endovascular therapy.
2. Early published results with the use of Nellix report sheath insertion times o30 minutes, which facilitates faster hemodynamic control. In addition, cannulation of con-tralateral limb during implantation of bifurcated stent grafts becomes obsolete.
3. Once the stent grafts are inflated and the endobags are prefilled with saline, sealing and hemodynamic stability are potentially achieved. Prefilling of the endobag provides fast bleeding control and makes aortic balloon occlusion unnecessary. No persisting bleeding from endoleaks and, therefore, no further retroperitoneal bleeding and reduced hematoma can lower the incidence of abdominal compart-ment syndrome. In addition, there is no potential for ongoing Fig. 2– Preoperative and postoperative computed tomography scans, as well as intraoperative angiography, showing a ruptured aorto-iliac aneurysm successfully treated with Nellix (courtesy of A. Holden, Auckland, New Zealand).
retrograde bleeding from persisting Type II endoleaks. The reduction of endoleak rate can diminish the reintervention rate and alter the follow-up modality and schedule. 4. Nellix can be used in combination with chimney grafts in
rAAA without the risk of gutter-related endoleaks and in ruptures during EVAR as an alternative of primary open conversion (Fig. 4).
In summary, such a design has the potential to stabilize patients in shock due to rapid sealing, lower rate of Type I and Type II endoleaks, and treat patients with unsuitable aortic neck morphology. EVAS potentially takes advantage of the benefits of a minimally invasive technique, while reduc-ing the drawbacks of EVAR in rAAA.
4.
Results of EVAS for rAAA
An early experience using Nellix in patients with acute AAA was published recently by Reijnen et al[43]. In this retro-spective multicenter observational study, eight high-volume centers with substantial EVAS experience enrolled 58 patients (28 rAAA, 30 symptomatic) within a 26-month period between February 2013 and April 2015. Fifty-three percent (n¼ 30) of patients were treated out of IFU for various reasons, including infrarenal neck configuration, angles, and maximum flow lumen. Mean follow-up was 9 months.
Mean procedural time in the ruptured subgroup was 957 31 minutes. Mean polymer volume was 1367 93 mL at a mean pressure of 1857 16 mm Hg. Concomitant procedures were performed in 18% (chimney, distal extension, access-related). Thirty-day mortality was 32% (n¼ 9); Type Ia endoleak rate was 3.5% (n¼ 1) and reintervention rate was 29% (n ¼ 8). Reinter-vention included three conversions (two due to instability and one after bridging of a mycotic aneurysm). During follow-up, aneurysm sac size was stable and no secondary endoleaks occurred. The authors concluded that EVAS in the acute setting is feasible—at least in experienced sites, safe, and concordant with the literature for EVAR. Thirty-day mortality is in line with the results of EVAR trials. It needs to be emphasized that many patients in this study were outside of IFU for Nellix or conven-tional EVAR devices. More robust prospective data with larger patient cohorts are required to evaluate the role of EVAS in the treatment algorithm of rAAA.
5.
Chimneys and EVAS in rAAA
Use of the Nellix endoprosthesis combined with chimney grafts has been studied recently[44]. The addition of chimney grafts can increase the applicability of endovascular aneurysm sealing in order to treat short-neck and juxtarenal aneurysms as an alternative to fenestrated endografts[45].
Dinkelmann et al [46] recently published a series of 26 elective chimney-EVAS procedures in 16 patients with jux-tarenal aneurysms with mean neck length of 3 mm with high primary technical success rate. Secondary interventions were required in 3 patients, each due to type IA endoleak, limb occlusion, and brachial dissection.
Case reports and small series also demonstrated the feasi-bility of emergent endovascular repair of ruptured aneurysm using chimney grafts and the Nellix EVAS system to reduce the potential for endoleak from the gutters around the chimney grafts [47,48]. Larger series are needed to confirm thesefindings and more robust data on both chimney EVAS and EVAS in ruptured cases are required to establish longer-term outcomes.
6.
Discussion
The endovascular approach for rAAA provides several proce-dural benefits over OR, including reduced invasiveness avoid-ing laparotomy, vascular control under local anesthesia, and hemodynamic stability. This may result in shorter procedural time, lower blood loss, and lower complication rate, followed by improved 30-day mortality and potentially improved long-term survival. EVAS may add another endovascular option in the treatment of patients with ruptured aneurysms.
There is ongoing debate on the comparison of EVAR and OR for rAAA. According to recently published randomized trials, there is a non-inferiority of mortality: 35% versus 37% in IMPROVE and 21% versus 25% in AJAX[13–15,35]. There is a secondary outcome benefit with EVAR due to reduced need for mechanical ventilation, blood transfusion due to less blood loss, and reduced intensive care unit and hospital stay combined with earlier recovery. On the other hand, reintervention rates are higher after EVAR—in-hospital reinterventions are comparable but long-term reinterventions are more frequent (25% v 5%). EVAR devices are more expensive but overall care cost is less expensive. According to the Dutch AJAX trial, 30-day costs for rEVAR are more expensive (þ€5,306) compared with EVAR. After 1 year, rEVAR is€1,435 less, with reduced length of stay[13,14]. One major concern in the treatment of rAAA applying the concept of EVAS while pressurizing the endobags is the potential for increasing the aortic rupture tear. However, recent publications have not shown a risk of increasing tear size or subsequent bleeding, as long as endobagfill pressure is kept at the intended pressure level of 180 mm Hg. By using contrast during prefill, endobag behavior can be observed throughout thefilling process and endobag bulging can be detected. The pre-fill step avoids underestimation of required polymer volume and results in aneurysm exclusion allowing additional polymer to be thawed. The correlation of volume and pressure needs to be known and respected duringfilling Fig. 3– Global registry enrolled more patients with more
complex anatomies compared with ENGAGE and GREAT registries.
with either saline or polymer. Bench tests and clinical experience have not shown an elevated risk for increased aortic wall tear when applying the intended and recom-mended pressure of 180 mm Hg (0.2 atm/bar).
The challenge in the use of Nellix in ruptured cases is to not underestimate the required volume in order to seal the rAAA.
For successful implantation in elective and ruptured patients, knowledge and understanding of the correlation between volume and pressure is mandatory (Fig. 5).
7.
Summary and conclusions
Initial Nellix publications provide promising clinical data in the elective setting [18–20]. EVAS for rAAA is feasible in experienced sites. Thirty-day mortality is in line with the rEVAR experience. The use of Nellix in rAAA is out of IFU at present. Experience in elective procedures is mandatory before applying EVAS in emergent cases or ruptures. EVAS has the potential to improve outcomes, but experience is still very limited, with just 28 patients in the largest series. Furthermore, mid-/long-term results are awaited. Next steps are to develop a treatment and implantation protocol together with bailout strategies. Overall, more robust pro-spective data and experience are required to test those treatment protocols before considering rEVAS as complemen-tary standard procedure in patients with rAAA. A multicenter prospective registry (Nellix Rupture Study) is planned to assess the outcomes in patients with a ruptured infrarenal aortic aneurysm treated with the Nellix EVAS system. Fig. 4– Intraoperative angiograhy showing an iatrogenic rupture at the aortic bifurcation (A, B) during EVAR being repaired with Nellix (C, D).
Fig. 5– Correlation between filling pressure and injected volume (percentage of precalculated volume). Pressure rises exponentially when volume reaches 100% of needed volume.
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