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K. Spanos and A. Giannoukas
https://doi.org/10.1016/j.avsg.2019.05.048. Epub 2019 Aug 5.
PMID: 31394244.
29. Oliveira NFG, Gonçalves FB, Hoeks SE, Josee van Rijn M, Ultee
K, Pinto JP, Raa ST, van Herwaarden JA, de Vries JPM, Verhagen
HJM. Long-term outcomes of standard endovascular aneurysm repair in patients with severe neck angulation. J Vasc Surg.
2018;68(6):1725–35. https://doi.org/10.1016/j.jvs.2018.03.427.
Epub 2018 Jun 15. PMID: 29914837.
The Role ofAorto-Uni-iliac Endografts
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A.Svetlikov, G.Khubulava, G.Gorbunov, V.Gurevich,
andY.Nakatis
48
Introduction
Endovascular aortic aneurysm repair (EVAR) is a relative
new weapon in the vascular surgeon’s armamentarium [1–6]
and studies have shown that aorto-uni-iliac (AUI) devices
coupled with occlusion of contralateral iliac artery and crossover femoral-femoral or iliac-femoral bypass, have comparable outcome in selected patients to treatment with
bifurcated devices. Although the use of this strategy is limited in daily practice for the treatment of abdominal aortic
aneurysms (AAA) in healthy patients, this may not be the
case for the treatment of high-risk patients with complex
iliac anatomy, in the treatment of r-AAA, or in the treatment
of complications of previously applied endovascular bifurcated devices for the treatment of AAA.The purpose of this
chapter is to review the relevant literature and discuss the
outcomes on the use of AUI stent grafts.
Despite this potential drawback of using an extraanatomic bypass, deployment of an AUI stent graft device is
still being used for the treatment of abdominal aortic aneurysms in different and complicated circumstances, such as
A. Svetlikov (*)
Division of Faculty Surgery, Cardiovascular Surgery Department,
North Western Scientic Clinical Center of Federal Medical
Biological Agency of Russia, St. Petersburg State University,
St. Petersburg, Russia
G. Khubulava
Cardiovascular Surgery Department, The First I.P.Pavlov St.
Petersburg Medical University, St. Petersburg, Russia
G. Gorbunov
Cardiovascular Surgery Department, North Western I.I Mechnikov
State Medical University, St. Petersburg, Russia
V. Gurevich
North Western Scientic Clinical Center of Federal Medical
Biological Agency of Russia, Atherosclerosis Treatment,
St. Petersburg, Russia
Y. Nakatis
Vascular Surgery Department, North Western Scientic Clinical
Center of Federal Medical Biological Agency of Russia,
St. Petersburg, Russia
presence of narrow terminal aorta; small diameter, tortuous,
kinked, calcied, or even occluded contralateral iliac artery;
presence of common iliac aneurysm; treatment of ruptured
abdominal aortiс aneurysms (rAAA); and management of
endoleaks of previously implanted endoprosthesis.
Many surgeons, however, debate the disadvantages of the
method due to the extra-anatomic bypass and express doubts
concerning the long-term results, claiming mainly poor
femoral- femoral bypass outcome, which varies in different
reports from 35 to 92%, for 5-year patency rates [1–9].
Since the earlier experiences with EVAR, access problems due to small and diseased iliac arteries have been one of
the most signicant causes of morbidity. The problem of a
narrow distal aorta, often encountered in patients with saccular aneurysms and penetrating aortic ulcers, and in those
with concomitant aorto-iliac occlusive disease, was traditionally treated by an aorto-uni-iliac converter with femoral
crossover bypass grafts. Although this operation has been
proven safe and effective, there are potential negative implications related to the open surgical portion of the operation
and the use of a prosthetic graft in the groin, including risk of
graft infection, narrowing or occlusion, and degeneration
over time. Patency of the contralateral internal iliac artery
relies on retrograde ow via the external iliac artery, with
reports indicating higher rates of long-term occlusion
[10–12].
Use ofAorto-Uni-iliac Device
fortheTreatment ofRuptured Abdominal
Aortic Aneurysms
The rst ruptured AAA was treated by Veith in 1994, and in
the same year Yusuf etal. published the rst case. Since then
several аuthors have published their experience with endovascular repair of ruptured abdominal aortiс aneurysms
(rAAA). Despite encouraging results, the proportion of
patients with rAAA being treated by EVAR remains relatively low. This may be because of logistical problems
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
G. Geroulakos et al. (eds.), Mastering Endovascular Techniques, https://doi.org/10.1007/978-3-031-42735-0_48
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including the availability of an experienced endovascular
team and a sufcient stock of suitable grafts. To enable
EVAR for rAAA, it has been suggested that endovascular
stent grafts must be immediately available in a wide range of
sizes. This would require a large stock of bifurcated stent
grafts and may not, for nancial and storage reasons, be possible in most vascular units. The modular AUI stent-graft
system comprising 16 components could replace a total of
750 unitary bifurcated systems [13–17].
Durability oftheCrossover Femoral-Femoral
Bypass Graft
One of the largest drawbacks to the use of AUI procedures is
the reliance on extra-anatomic bypass grafts to revascularize
the contralateral limb. The patency of crossover iliac- femoral
or femoral-femoral bypass is acceptable when used for
occlusive disease. Previous reports on crossover femoralfemoral bypass graft patency have been related to patients
with occlusive arterial disease. Patency rates for femoralfemoral bypass grafts vary in the literature. R.L.Ng et al.
reported a cumulative patency rate at 6years of 92% for
femoral-femoral crossover procedures and a low early mortality rate of 1.3%, whereas A.J.Lamerton et al. showed a
cumulative patency rate of 60% at 5years [17, 18].
The primary indications today for the treatment of AAA
by EVAR with the AUI conguration as they were proposed
in the reviewed studies are the following:
1. Distance to lower renal artery to aortic bifurcation
<70mm
2. Narrow terminal aorta <15mm (transverse diameter)
3. Contralateral common iliac artery angle >90° from the
longitudinal axis of the aneurysm
4. Obstructed contralateral common iliac artery
5. Isolated infrarenal abdominal aortic dissections
6. Combination of the previous indications
7. Conversion to the AUI conguration while deploying a
bifurcated endograft due to impossible contralateral
limb catheterization
8. Ruptured AAA
9. Concomitant ecstatic or frankly aneurysmal bilateral
common iliac arteries, unless the patient has indispensable internal iliac arteries (relative indication)
10. Heavily calcied contralateral external iliac artery (rela-
tive indication)
11. Narrow contralateral common iliac artery (diameter
<5mm), with or without previous transluminal angioplasty (relative indication)
12. Previous stents to the iliac arteries (relative indication)
Advantages ofAorto-Uni-Iliac Stent Grafts
The delivery system is usually simple either in custommade or commercial devices. No stent graft orientation is
needed, and no limb cannulation is required, and thus fewer
intraortic manipulations in 3-dimentional space under
2-dimensional uoroscopic guidance and decreased risk of
embolization. Less contrast agent is needed. Home-made
systems have several advantages even compared to commercial ones; they can be customized, pre- or intraoperatively, to deal with any unusual circumstances and can
quickly incorporate lessons learned intraoperatively. The
presence of a separate occluder for the contralateral iliac
artery occlusion is an advantage of the method. The common iliac occluder is independent from the primary stent
graft in both size and position. The two parts are separate,
so that occluder diameter can vary widely regardless of the
diameter of the primary stent graft. It can also be placed
exactly where it is needed regardless of the position of the
primary stent graft.
Disadvantages ofAorto-Uni-Iliac Stent
Grafts
Of course, the simplicity of AUI stent-graft deployment
comes at a price. An occlusion of the contralateral iliac artery
is required so as to seal the aneurysm associated with a
femoral- femoral bypass in order to reestablish perfusion to
the contralateral limb. This may put the patient at risk, as
AUI stent graft channels all the blood ow into one iliac
artery and from there to the pelvis. Even widely patented
AUI stent grafts can limit ow enough to cause claudication
if the external iliac artery is small and the patient active. The
patency of crossover iliofemoral or femoro-femoral bypass
is very high as demonstrated in this review.
Early critics pointed to poor long-term patency rates of
the femoro-femoral bypass, but more recent data have dispelled this argument pointing to excellent long-term patency
of the femoro-femoral portion of AUI repairs. Fortunately,
the patency of crossover femoro-femoral bypass is very high
in recent published literatures. R.L. Ng et al. reported a
cumulative patency rate at 6years of 92% for femoro- femoral
crossover procedures and a low early mortality rate of 1.3%.
Also, despite the fact that these procedures might be complicated by the development of graft infection, graft occlusion,
false aneurysm formation, or seromas in the groin, their incidences are very low [18–20].
Hynes and Sultan reported that AUI EVAR with a femfem crossover is a safe and effective alternative to bifurcated endografts in high-risk patients with AAA. This is the
48 The Role ofAorto-Uni-iliac Endografts
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505
same nding as in our study. This is explained by the fact
that AUI EVAR requires less preoperative planning, less
operative time, and less trauma. In our study, the mean
operative time was 114 min in the fem-fem group and
79min in the non- fem- fem group (𝑃=0.013). This short
operative time is due to the omission of the bypass step.
This also enabled less blood loss and less anesthesia time
for those patients, which is more convenient when dealing
with the high risk associated with severe comorbidities or
ruptured AAAs. Jean- Baptiste et al. reported higher incidence of complications with AUI EVAR compared to bifurcated endografts in high- risk patients. This could be
attributed to the fact that AUI grafts were considered in this
study for higher-risk patients, while bifurcated grafts were
used in healthier patients. Hynes and Sultan published
results in high-risk patients for bimodular devices which
mirror the results of AUI with or without crossover but
rebuff the nding of Jean-Baptiste that AUI EVAR is inferior to bimodular conguration. Carraello etal. reported
high mortality rate with AUI grafts, but a deeper look at this
study design demonstrates that precious time was wasted in
preoperative analysis and preoperative CT angiography in
these unstable patients. A number of studies suggested that
the use of AUI instead of the bifurcated endografts might be
attributed to its easier preoperative planning and intraoperative application, especially in centers with less experience
with EVAR.Katsikas etal. documented through meta-analysis that the main advantages of the AUI endograft are its
simplicity and versatility. In 2004, Arko etal. demonstrated
that 55% of patients considered for endovascular AAA
repair met the anatomical selection criteria, with men twice
as likely as women. Conversely, if we applied AUI options
for those 220 patients, all can be managed routinely with
this conguration. Currently up to 95% of our AAA patients
are deemed suitable for EVAR. Clouse et al. proved that
AUI with fem-fem crossover graft is a safe, effective option
with satisfactory midterm results. Five of their patients had
chronic contralateral iliac occlusion but they performed
fem-fem crossover bypass [21–24].
References
1. Piotrovsky JJ, Pear WH, Jones DN, Whitehill T, Bell R, Patt A,
Rutherford RB.Aortobifemoral bypass: the operation of choice for
unilateral iliac occlusion? J Vasc Surg. 1988;8:211–8.
2. Plecha FT, Plecha FM. Femorofemoral bypass grafts: ten-year
experience. J Vasc Surg. 1984;1:555–61.
3. Flanigan DP, Pratt DG, Goodreau JJ, Burnham SJ, Yao JS,
Betgan JJ. Hemodynamic and angiographic guidelines in
selection of patients for femorofemoral bypass. Arch Surg.
1978;113:1257–62.
4. Eugene J, Goldstone J, Moore WS.Fifteen year experience with
subcutaneous bypass grafts for lower extremity ischemia. Ann
Surg. 1977;186:177–83.
5. Brief DK, Brener BJ. Extra-anatomic bypasses: femorofemoral
crossover grafts. In: Wilson SE, Veith FJ, Hobson RW, editors.
Vascular surgery: principles and practice. NewYork: McGraw-Hill;
1987. p.415–8.
6. Dick LS, Brief DK, Alpert J, Dick LS, Brief DK, Alpert J, Brener
BJ, Goldenkranz R, Parsonet V.A 12-year experience with femorofemoral crossover grafts. Arch Surg. 1980;115:1359–65.
7. Mosley JG, Marston A.Long term results of 66 femorofemoral
bypass grafts: 9-year follow-up. Br J Surg. 1983;70:631–4.
8. Maini BS, Mannick JA.Effect of arterial reconstruction on limb
salvage: a ten-year appraisal. Arch Surg. 1978;113:1297–304.
9. Chuter TA, Faruqi RM, Reilly LM, Kerlan RK, Sawhney R, Wall
SD, et al. Aortomonoiliac endovascular grafting combined with
femorofemoral bypass: an acceptable compromise or a preferred
solution? Semin Vasc Surg. 1999;12:176–81.
10. Criado E, Burnham SJ, Tinsley EA Jr, Johnson G Jr, Keagy
BA.Femorofemoral bypass graft: analysis of patency and factors
inuencing long-term outcome. J Vasc Surg. 1993;18:495–505.
11. Clouse WD, Brewster DC, Marone LK, Cambria RP, LaMuraglia
GM, Watkins MT, et al. Durability of aortouniiliac endografting
with femorofemoral crossover: 4-year experience in the EVT/
Guidant trials. J Vasc Surg. 2003;37:1142–9.
12. Dalanis I, Nano G, Bianchi P, Stegher S, Casana R, Malagrida
G, Tealdi DG. Endovascular techniques for the treatment of ruptured abdominal aortic aneurysms: 7-year intention-to-treat results.
World J Surg. 2006;30:1809–14; discussion 1815-1816.
13. Peppelenbosch N, Geelkerken RH, Soong C, Cao P, Steimetz OK,
Teijnk JA, Lepantalo M, De Letter J, Vermassen FE, Derose G,
Buskens E, Buth J.Endograft treatment of ruptured abdominal aortic aneurysms using the talent aortouniiliac system: an international
multicenter study. J Vasc Surg. 2006;43:1111–22.
14. Lee WA, Huber TS, Hirneise CM, Berceli SA, Seeger JM.Eligibility
rates of ruptured and symptomatic AAA for endovascular repair. J
Endovasc Ther. 2002;9:436–42.
15. Leon LR, Labropoulos N, Laredo J, Rodrigues HE, Kalman PG.To
what extent has endovascular aneurysm repair inuenced abdominal aorticaneurysm management in the state of Illinois? J Vasc
Surg. 2005;41:568–74.
16. Armon MP, Yusuf SW, Whitaker SC, Gregson RH, Wenham PW,
Hopkinson BR. The anatomy of abdominal aortic aneurysms:
implications for sizing of endovascular grafts. Eur J Vasc Endovasc
Surg. 1997;13:398–402.
17. Lamerton AJ, Nikolaides AN, Eastcott HH. The femorofemoral
graft. Haemodynamic improvement and patency rate. Arch Surg.
1985;120:1274–8.
18. Ng RL, Gillies TE, Davies AH, Baird RN, Horrocks M.Iliofemoral
versus femorofemoral bypass: a 6-year audit. Br J Surg.
1992;79:1011–3.
19. Lipsitz EC, Ohki T, Veith FJ, Rhee SJ, Gargiulo NJ 3rd, Suggs WD,
et al. Patency rates of femorofemoral bypasses associated with
endovascular aneurysm repair surpass those performed for occlusive disease. J Endovasc Ther. 2003;10:1061–5.
20. Arko FR, Filis KA, Seidel SA, etal. How many patients with infrarenal aneurysms are candidates for endovascular repair? The northern California experience. J Endovasc Ther. 2004;11(1):33–40.
21. Katsikas VC, Dalainas I, Martinakis VG, Xiromeritis K.The role
of aortouniiliac devices in the treatment of aneurysmal disease. Eur
Rev Med Pharmacol Sci. 2012;16(8):1061–71.
22. Elixen JB, Batt M, Azzaoui R, Koussa M, Hassen-Khodja R, Haulon
S.A comparison of the mid-term results following the use of bifur-
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cated and aorto-uni-iliac devices in the treatment of abdominal
aortic aneurysms. Eur J Vasc Endovasc Surg. 2009;38(3):298–304.
23. Bonardelli S, Nodari F, De Lucia M, Cervi E, Giulini SM.Crossover
ilio-iliac bypass and removal of femoro-femoral graft as rst treatment for the infection of crossover bypass in aorto-uni-iliac endovascular aneurysm repair. Vascular. 2012;20(6):306–10.
24. Hynes N, Sultan S.A prospective clinical, economic, and qualityof- life analysis comparing endovascular aneurysm repair (EVAR),
open repair, and best medical treatment in high-risk patients with
abdominal aortic aneurysms suitable for EVAR: the Irish patient
trial. J Endovasc Ther. 2007;14(6):763–76.
Hostile Proximal Neck: Angulated,
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Short, or Conical
J.Shea, A.L.Pouncey, andC.Bicknell
49
Case Presentation
A 90-year-old male was admitted to the emergency room
from home with back pain and a large tender expansile mass
on abdominal examination. He was otherwise t with a past
medical history of vitamin D deciency. He was a nonsmoker, with no other risk factors for atherosclerosis.
A CT angiogram conrmed the presence of a 91 mm
aneurysm with signicant 83-degree (beta) angulation at the
neck (Fig.49.1).
Measurements were taken using 3D planning software.
The neck length was 31.5mm, and the neck diameter was
30mm. The common iliac arteries were 14mm diameter on
the right and 17mm diameter on the left. The external iliac
arteries were 7mm in diameter.
Continued at page 519
Fig. 49.1 CT angiogram demonstrating signicant beta angulation of the aneurysm neck
J. Shea · A. L. Pouncey · C. Bicknell (*)
Imperial Vascular Unit, London, UK
e-mail: jessica.shea@nhs.net; a.pouncey@imperial.ac.uk;
colin.bicknell@imperial.ac.uk
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
G. Geroulakos et al. (eds.), Mastering Endovascular Techniques, https://doi.org/10.1007/978-3-031-42735-0_49
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Background
For an infrarenal abdominal aortic aneurysm (IRAAA), the
aneurysm neck is dened as the segment of aorta between
the lowest renal artery and commencement of the aneurysm
along the centreline of the aorta. This region is used as the
landing zone for a stent-graft in endovascular aortic repair
(EVAR); or, in open repair, for placement of an aortic clamp
and anastomosis of the graft [1]. For EVAR, the optimal
IRAAA neck is a uniform, straight, smooth cylinder of sufcient length and appropriate diameter, which enables stable
xation and complete sealing of the stent-graft to the vessel
wall. In light of this, stent-graft manufacturers have set
device-specic IFU (instructions for use) thresholds, dening appropriate neck anatomical characteristics needed to
ensure adequate sealing of the device. These criteria are
based on neck length, diameter (distal and proximal), and
angulation (alpha and beta), as well as the degree of calcication and thrombus burden. Deployment outside of these
anatomical constraints is associated with a greater risk of
graft-related adverse events, in particular loss of an adequate
sealing zone leading to type 1a endoleak, stent-graft migration, sac growth, secondary rupture, need for re-intervention
and aneurysm-related mortality [2] (Fig.49.2).
The Hostile Neck
Anatomical Features andAssociated Outcomes
Hostile neck anatomy (HNA) denotes anatomically unfavourable anatomy for endovascular repair (EVAR). It is the
most frequent determinant of ineligibility for EVAR [3].
HNA is associated with increased technical difculty and a
greater risk type 1a endoleak (loss of the proximal seal),
reintervention, secondary rupture, renal injury, and death [4,
5]. A meta-analysis of seven observational studies has noted
that, following EVAR, patients with HNA had over four
times the risk of a type 1a endoleak and nine times the risk of
aneurysm-related mortality within 1year compared to those
with favourable anatomy [6].
The precise anatomical denition of a hostile neck varies
from study to study and depends on the constraints dened
by IFU for the device deployed [7]. Stather etal. dened
HNA as one of a neck length of <15mm, neck diameter of
>28mm, and/or angulation of ≥60°, noting that these features were associated with greater technical difculty and
worse short-term outcomes [4]. More extensive criteria were
used by AbuRahma et al., who dened HNA as one of a
length of <10 mm, a diameter >28 mm, an angulation of
>60°, ≥50% thrombus, ≥50% calcication, and a conical
neck (reverse taper), noting an associated increase in the rate
of type 1 endoleak, reintervention, and peri-operative complications [8]. Expert consensus has since dened HNA as
one of ve relevant anatomical parameters: aortic neck
length, angulation, diameter, conical neck, and the presence
of circumferential calcication [9]. These features do not
occur in isolation, and the effects are cumulative, with a
resultant decrease in the likelihood of technical and clinical
success [4, 10]. Selected features of hostile neck anatomy—
short neck, wide neck, angulated and conical neck (SWAC)—
are described below (Fig.49.3):
Fig. 49.2 Anatomical characteristics of aneurysm necks
Short Neck
For a standard EVAR to remain securely in position the sealing zone of the stent-graft must lie in direct apposition to the
vessel wall for a certain distance, exerting an even radial
force. A short neck produces challenges to stent-graft positioning and obtaining an early seal; therefore, type 1a endoleaks on the table are common; long-term xation and
consequent migration; and long-term sealing as minimal
aortic neck degeneration and dilatation can lead to type 1a
endoleak and long-term graft failure.
The minimum neck length required for optimal device
xation is dependent on the individual characteristics of the
stent-graft used. Although a short neck is often dened as
<15mm, necks with a length between 10 and 15 mm can
often be treated successfully with off-the-shelf devices and
accurate deployment [11, 12]. However, approximately 41%
of patients present with neck lengths outside that of the tra-
49 Hostile Proximal Neck: Angulated, Short, or Conical
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Fig. 49.3 Hostile neck characteristics
509
ditional IFU for most aortic endografts [13], and a short neck
is the most common cause of ineligibility for endovascular
repair [14]. When standard EVAR is utilised for the treatment of an IRAAA with a short neck, it is associated with
increased risk of type 1 endoleak and stent-graft migration
[15]. Moreover, regardless of technical outcome, a two-fold
increase in all-cause mortality for patients with short necks
at 5years is observed (adjusted hazard ratio [HR] 2, condence interval 1.02–3.8, p=0.04) [16].
Wide Neck
A neck diameter of greater than 30 mm is by denition aneurysmal aortic tissue. A wide neck will not necessarily produce challenges to graft positioning and obtaining an early
seal, but, by denition, the wide neck is diseased and will
degenerate in time most likely, with long-term xation issues
and consequent migration and long-term sealing issues leading to graft failure.
While not necessarily presenting an increase in technical
difculty, or associated with adverse short-term outcomes, in
the median term, an infrarenal neck diameter of >30mm is
associated with an increased risk of neck-related adverse
events, type 1a endoleak, and secondary intervention [17].
Moreover, an increase in additional post-EVAR aortic neck
dilation is also observed (odds ratio [OR] 3.1, p=0.02) [18].
Angulation
Aortic neck angulation is measured perpendicular to the aortic axis, in the middle of the exure [19]. Angulated necks
produce challenges to stent-graft positioning around the curvature of the aorta and obtaining an early seal, long-term
xation, and long-term sealing.
Signicant angulation frequently occurs with concomitant adverse anatomical features, and pre-operative assessment of the “functional” neck, the length used for the sealing
of the stent-graft, can be difcult [20]. Aortic neck angulation (β angle) refers to the angle between the neck and the
long axis of the aneurysm. An angle of >60° is associated
with an increased use of intraoperative adjunctive procedures
[21]; persistent type 1a endoleak following EVAR [22, 23];
and increased risk of peri-operative complications (OR 3.38,
p=0.009) [7, 8]. On meta-analysis of six observational stud-
ies, a higher rate of type 1a endoleak at 3years (5.6% vs.
2.6%, p<0.0001) and an increased rate of neck-related secondary intervention (13.1% vs. 9%, p<0.05) were associated
with severe neck angulation (>60°); but aneurysm sac
increase, rupture, and all-cause mortality were not signicantly different at mid-term [24]. Suprarenal neck angulation
(α angle) refers to the angle between the suprarenal and
infrarenal aorta. It affects feasibility of suprarenal xation,
and following EVAR is associated with an increased risk of
technical failure, peri-operative mortality (11.1% vs. 0.25%,
p<0.001), type 1a endoleak (19.8% vs. 2.2%, p< 0.001),
stent migration (7.6% vs. 0%, p<0.001), and a reduction in
long-term survival [25].
Conical Neck
If the cylindrical stent-graft is not in perfect apposition to the
aortic wall, the risk of failure of sealing is substantial. The
conical neck provides challenges to the endovascular surgeon in appropriately sizing the graft to gain an initial seal,
and just as the wide-necked aneurysms, this portion is diseased, and so may degenerate in time.
This is a problem for a signicant proportion of patients.
Within the Gore Global Registry for Endovascular Aortic
Treatment (GREAT), 42.6% (1312/3077) patients were
noted to have non-cylindrical necks [26]. A conical proximal
neck is dened as a cone-shaped proximal neck with >10%
increase in vessel diameter within the 15mm length of the
proximal landing zone. The presence of a conical neck makes
sizing of the stent-graft diameter more difcult, reduces the
length of adequate seal, and consequently is associated with
an increased risk of type 1 endoleak (OR 5.25, p<0.0001)
and need for aortic cuff (OR 5.95, p<0.0001) [8]. The conical neck is purported to be the strongest factor associated
with the failure of standard EVAR [27].
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Who Does HNA Aect?
Neck anatomy is one of the most important factors governing
qualication for treatment within IFU and therefore eligibility for EVAR [3, 28], with HNA resulting in patients being
turned down for AAA repair, necessitating open repair, or
leading to a substantial proportion of patients treated outside
of IFU [29, 30].
Neck anatomy varies with aneurysm size [31, 32], sex
[33], and ethnicity [34]. Hostile neck anatomy has been
reported to occur in 34–66% of patients and more frequently
in patients with an IRAAA of >55mm diameter [30, 32, 35].
In a retrospective study of 14,739 IRAAA patients in the
Vascular Quality Initiative (VQI), 19.6% had a short neck
(<15mm), 6.3% had severe angulation (>60°), and 9.1% had
a wide neck (>30mm) [35].
It is well recognised that women are less likely to be eligible for EVAR (34% vs. 54%, OR 0.44, 95% CI [0.32–
0.62]) [36, 37] and lose eligibility for EVAR at a smaller
AAA size (55 mm vs. 65 mm) compared to men [31].
Accordingly, within the VQI those with HNA were more
often female [35]. Women have been noted to have greater
neck angulation and a higher percentage thrombus burden
than men [31, 33]. Within the Gore Global Registry for
Endovascular Aortic Treatment (GREAT), in addition to
more severe angulation, a greater proportion of women were
also noted to have non-cylindrical neck morphology and
more often required reintervention [26]. Prevalence of HNA
is even more marked outside of the Caucasian population. A
study of Korean patients found that neck anatomy was eligible in only 34.0% of intact and 23.0% of ruptured AAAs
with greater neck angulation again noted in women [30].
Endovascular Strategy andTechniques
Selecting theRight Approach
It is often difcult for clinicians to decide on the most appropriate primary management for IRAAAs with more complex
pathology such as HNA. The APPROACH concept was
coined by Donas and Torsello to help with this decisionmaking for patients with complex pararenal aortic pathology
[38]. It encompasses eight major criteria as key factors to
inuence decision-making: aortic pathology, the patient’s
clinical prole, proven literature evidence, operator’s preference, skill set, access considerations, costs, and hostile neck
features [38]. All these considerations and the wishes of the
patient [39] should be amalgamated together to decide
whether an endovascular or open approach, or indeed, conservative management, would be most benecial [40]. Where
the optimal strategy extends beyond the borders of the opera-
tor’s expertise, collaboration, and advice should be sought
[41]. Nonetheless, the AAA population is a high-risk population with high proportion of smokers with cardiac, respiratory, and renal disease, who stand to benet greatly from the
reduced physiological insult and benets afforded by endovascular repair. Many of these patients will have HNA, which
is noted to increase in prevalence with age [3]. Therefore, a
comprehensive technological armamentarium and a strategic
approach are needed to provide the best possible repair.
Various methods and technical considerations for the treatment of IRAAA with HNA are outlined below.
EVAR
Pre-operative Assessment
Prior to repair, appropriate imaging, most often high-quality
(<1 mm thickness) computed tomography angiography
(CTA), should be utilised to examine the aortic vascular morphology. This enables characterisation of the features of an
HNA, facilitates pre-operative planning, and aids device
selection. Centreline reconstruction should be used to enable
accurate neck diameter and length measurement for the evaluation of the “functional” neck—the length that can be used
for the sealing of the stent-graft [20]. Aortic angulation
should be measured perpendicular to the aortic axis, in the
middle of the exure [19], and can be further evaluated using
3D reconstruction [19].
Accurate diameter assessment is important for stent-graft
oversizing, to prevent migration, and is normally recommended at between 10–20% and <30% [42]. Consideration
should be given to the high likelihood of asymmetrical endograft placement in patients with severe angulation, as this
may reduce the degree of oversizing calculated prior to
deployment [20]. Further difculty is encountered with a
conical neck, for which oversizing may be more marked in
the narrower portion. This is usually handled in a pragmatic
fashion, with acceptance of a lesser degree of oversizing in
the larger segment (maintaining >10%) and a greater degree
of oversizing in the narrow segment (maintaining <30%)
[43]. In these cases, the neck, in the strictest denition, may
be short, but there may be a much longer usable sealing zone.
In cases with a short or angulated neck, an assessment of
the optimal C-arm position to ensure angulation orthogonal
to the aortic neck and crux of the distal renal artery should
also be made at this point to maximise use of neck length for
proximal sealing. This should be done with the caveat that
positioning may need to change slightly due to vessel
straightening during the procedure. This adjustment can be
accounted for following the deployment of the proximal
stent rings through correction of the C-arm position and further angiography prior to full stent-graft deployment [20].
49 Hostile Proximal Neck: Angulated, Short, or Conical
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O-the-Shelf Devices
While there is little doubt that HNA is associated with
reduced durability, in carefully selected populations, such
as elderly and medically compromised patients (for whom
the mortality risk of complex endovascular or open repair
is greater), or where there is an urgent need for repair,
EVAR remains an attractive option. Many off-the -shelf
endografts with active xation have been reported to provide reasonable results when neck anatomy is not perfect
but acceptable and can, in these high-risk patient groups,
pragmatically be used despite an increased risk of type 1a
endoleak [3, 44, 45].
When selecting a device there are a variety of stent-grafts
on the market with features designed to accommodate HNA,
which have expanded the capabilities of treatment within
IFU [5, 46].
Controlled delivery and accurate deployment are important. In cases of severe aortic neck angulation or vessel tortuosity, intraoperative techniques such as the use of pull-through
wires or directional tip control may be utilised to improve
tracking and accurate deployment of the device [47, 48]. The
Endowedge Technique, using angioplasty balloons within
the renal artery to align scallops of a stent-graft and maximise proximal placement, has also been described to maximise the seal zone [49]. Now though several grafts are
repositionable.
Further technological advances aim to improve the accuracy of deployment. The GORE EXCLUDER Conformable
AAA Endoprosthesis with ACTIVE CONTROL System
allows dynamic adjustment intraoperatively, angling the
proximal end of the graft so that the device can be positioned
along the centreline of the aorta, and there is no loss of sealing zone, and it is more conformable. These features decrease
the risk of type 1a endoleak and perhaps increase the longterm sealing and xation of the graft.
In wide-necked aneurysms, one example is the ovation
stent-graft, for which xation and seal are separated, with
graft xation achieved by suprarenal stent anchors and seal
by polymer-lled inatable sealing rings. The reduced radial
force, and hence reduced risk of proximal aortic dilatation,
has been purported as an explanation for the long-term success of this graft in wide-necked AAA.
This graft IFU states that a proximal aortic landing zone
for the sealing ring 7mm below the inferior renal artery is
required, for which no difference in rates of type 1a endoleak,
reintervention, or aneurysm-related mortality have been
reported at 5years [16, 46, 50, 51]. However, it is a general
misconception that suprarenal xation devices increase the
ability to treat a short neck. No difference in the rates of stent
migration and midterm outcomes between infra- and suprarenal xation devices has been demonstrated, but inferior
renal outcomes associated with suprarenal xation are
observed [12, 52, 53].
However, while stent-graft devices have clearly improved,
the marginal gains in IFU cannot accommodate all cases, and
careful post-operative surveillance is needed [54]. Further
endovascular approaches are needed to improve durability
and also to provide rescue following post-operative neckrelated complications such as type 1a endoleak and stent
migration.
Adjunctive Procedures
For endovascular management of IRAAAs with HNA, additional adjuncts and techniques can be used to maximise
proximal seal and positioning, both intraoperatively during
the primary procedure, and to rescue following post- operative
neck-related complications such as type 1a endoleaks.
When a proximal endoleak at the time of stent-graft insertion occurs, the simplest strategy is to reshape the proximal
landing zone via balloon ination, thus changing the conformation of the proximal stent end to increase adherence. This
can then be followed by extension with a bare-metal stent or
with stent-graft cuff placement if needed—both of which are
reported to provide acceptable midterm outcomes [55, 56].
Palmaz stents (Cordis Corporation, Bridgewater, NJ) are
balloon-expandable stents with a closed cell design which
exerts a high radial force, encouraging the moulding of the
stent-graft to the vessel wall while reducing the risk of
branch compromise. They are well established as a treatment
for treating intraoperative type 1a endoleaks during EVAR,
more commonly seen in hostile neck patients [57, 58].
However, in the long-term follow-up of 125 patients over a
median of 43months, a signicant increase in the diameter
of the sealing zone was observed, with 14% of cases demonstrating signicant Palmaz stent migration, 9% with stentgraft migration, and 16% of cases developing a type 1a
endoleak. Therefore, while Palmaz stenting presents an adequate bailout strategy, it should not be used rst line to
extend elective infrarenal endovascular aneurysm repair in
more demanding anatomies [56].
When a segment of infrarenal aorta proximal to the EVAR
remains, a cuff can be used to repair or reinforce the sealing
zone. For cases with HNA, use of cuffs has been associated
with superior durability [59]. Additionally, pre-deployment
of an aortic cuff into a challenging neck prior to placement of
the main stent-graft can be used to improve sealing, a strategy known as the Kilt Technique [60]. This technique may
have utility for cases with severe neck angulation, as it is
reported to straighten the landing zone prior to main body
deployment. Several case series have reported a high rate of
technical success and low mortality and complication rates
in the short term [60–65]. In the case of wide-necked aneurysms, deployment of a thoracic endograft can be utilised as
a proximal extension for a main infrarenal device, named the
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