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Endoluminal Treatment of Infrarenal Abdominal Aortic Aneurysm 25
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a
b
Fig. 3.1. (a,b)
26 Vascular Surgery
c
d
Fig. 3.1. a Contrast-enhanced CT scan at the level of the neck of the aneurysm, immediately below the renal
arteries. The neck has a maximum diameter of 19 mm on this image and has no irregular features, such as mural
thrombus or atheromatous plaque. b Contrast-enhanced CT scan at the level of the sac of the aneurysm,
showing a typical “target” appearance due to the presence of significant mural thrombus lining the aneurysm
and contrast filling the flow channel. Maximum diameter 62 mm. c Contrast-enhanced CT scan at the level just
below the aortic bifurcation, showing two iliac arteries of diameter 16–17 mm. d Three-dimensional reconstruction of a contrast-enhanced CT scan, showing angulation between the neck and the aneurysm of about 45°. The
iliac arteries are tortuous, with an angulation of at least 90°.
Endoluminal Treatment of Infrarenal Abdominal Aortic Aneurysm 27
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a
b
Fig. 3.2. a Calibrated aortic angiogram showing the aortic lumen, renal arteries and neck of the aneurysm. b
Calibrated aortic angiogram showing the lumen of the aorta and both iliacs. Note that the diameter of the iliac
arteries measures less on the angiogram than on the CT images.
28 Vascular Surgery
B. Oversize all diameters by 10 per cent.
C. Oversize the proximal diameter by 20 per cent and the limb diameters by
10 per cent.
D. Undersize all diameters by 10 per cent and balloon-expand them to the proper
size at the end of the procedure.
Due to the patient’s severely impaired lung function and other risk factors,
the procedure was performed under epidural anaesthesia. The abdomen and
both groins were prepared into a sterile field. Common femoral arteries were
surgically exposed, sheaths were inserted, and wires were put into place under
fluoroscopy. Angiography was performed to mark exactly the position of the
renal arteries (Fig. 3.3), and an endoluminal device was implanted successfully
(Fig. 3.4).
Question 6
Whilst deploying the graft, the following need to be considered:
A. The orientation of the graft.
B. The location of any renal accessory renal arteries.
C. The location of the aortic bifurcation.
D. The location of the bifurcation of the common iliac artery.
Fig. 3.3. Early on-table angiogram to locate precisely the renal arteries during graft implant procedure. The
arrow indicates the left renal artery. The device is ideally placed immediately below the orifice of the renal artery
(note that some designs of endograft incorporate a bare stent that projects over the renal orifices).
Endoluminal Treatment of Infrarenal Abdominal Aortic Aneurysm 29
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Fig. 3.4. Angiogram of a successfully deployed graft showing patent renal arteries, the endograft on the outside
of the contrast-filled lumen, and the absence of an endoleak (flow of blood into the AAA sac). The blush near the
proximal end of the graft (arrow) is gas inside the superimposed intestine.
Question 7
What are the more common complications of endoluminal aneurysm repair?
Question 8
Which of the following is the most important finding on follow-up imaging
A. No change to the lung field on chest X-ray.
B. The diameter of the aneurysm compared to the original diameter.
C. The absence of a type II endoleak previously visible on CT.
D. The position of the graft on abdominal X-ray.
Commentary
AAAs are generally a disease of elderly white males. In men, AAAs start to occur at
the age of 50 years, reaching a peak incidence of about 350/100,000 person-years by
the age of 80 years. The prevalence of AAAs of at least 3 mm in diameter in men
over 65 years is 7.6 per cent. In women, AAAs tend to occur a few years later in life.
The age-adjusted incidence is four to six times higher in men than in woman. Age,
30 Vascular Surgery
gender and smoking are the risk factors with the largest impact on AAA prevalence
[1].
Although ultrasonography is the method of choice for population screening or
follow-up measurements in patients with known aneurysms, ultrasound imaging
alone gives insufficient information for preoperative assessment for repair procedures. For open repair, most surgeons recommend a preoperative imaging study
with (spiral) CT scanning, which provides accurate information regarding
aneurysm size and its relationship to branch vessels, as well as any anatomic anomalies [2].
Preoperative imaging is even more important when endovascular treatment is
considered, because patient selection and sizing of the endograft depend on it. With
contrast-enhanced spiral CT, the dimensions of the proximal neck can be determined accurately and the presence of calcification or mural thrombus noted.
Although the anatomy of the iliac arteries and accessory renal arteries can be
demonstrated by spiral CT, in most medical centres calibrated aortography is also
performed to allow accurate measurements. Anteroposterior and lateral views are
required to demonstrate tortuosity in the neck of the aneurysm and the iliac arteries
[3]. Three-dimensional reconstructions of contrast-enhanced CT scans are being
utilised increasingly in order to get a more detailed perception of the actual
anatomy. These reconstructions may become the standard method for accurate
sizing of endografts in the near future. [Q1: D]
The decision of whether to treat an AAA remains a difficult process in which multiple factors play a role. One important factor is the risk of rupture, which, unfortunately, will always be an estimate, since large numbers of patients with AAAs have
not been followed up without intervention. Based on currently available data from
the UK Small Aneurysm Trial, the annual risk of rupture is less than 1 per cent
when the diameter is 4–5.5 cm, although the validity of this risk estimation was
compromised by the fact that many patients in this trial received surgery at a diameter less than 5.5 cm due to other factors. With increasing diameters, the annual
rupture rates have been estimated to be as follows: 5–6 cm, 5–15%; 6–7 cm, 10–20%;
7–8 cm, 20–40%; <greater than>8 cm, 30–50% [4]. [Q2: C]
Recent trials have demonstrated a reduction in 30-day morbidity and mortality
rate in patients undergoing endoluminal aortic aneurysm surgery compared to the
traditional open approach [5, 6]. These well-constructed randomised trials showed
a reduction of approximately 65 per cent in the incidence of moderate to major
complications following endoluminal repair compared to open repair. Current
information indicates that the benefit is likely to be greater for high-risk patients.
The presence of renal failure is not an absolute contraindication to the endovascular
approach as various precautions can be taken to protect the kidneys, such as intravenous hydration, antioxidant medications or temporary dialysis. The average contrast use for the procedure is 120–150 ml. [Q3: C, D]
Not all aneurysms are anatomically suitable for endovascular repair. In general,
all endoluminal grafts need areas of reasonably healthy vessel wall proximally and
distally to be able to seal off the aneurysm from the blood flow. Most important for
suitability are the size and morphology of the proximal neck (the segment of aortic
wall between the lowest renal artery and the beginning of the aneurysm). The neck
should consist of relatively normal aorta over a length of at least 1.5 cm, and the
diameter should not exceed 30 mm. Another limitation for endovascular repair is
the maximum angulation in the neck (should not exceed 60°) and the iliac arteries
(ideally less than 90°) [7]. [Q4: A, C, D]
Endoluminal Treatment of Infrarenal Abdominal Aortic Aneurysm 31
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After precise measurements from angiography and CT scanning, the optimal size
of the graft can be chosen. To anchor the proximal part of the graft firmly onto the
native aortic wall, a constant radial force of the graft is necessary. To achieve this, it
is important to oversize the graft. Unfortunately, some recent reports suggest that
there may be slow ongoing expansion of the neck of the aneurysm after endoluminal AAA repair [8]. This may favour a more aggressive oversizing of the proximal
part of the graft, but this could in turn cause infolding of the graft fabric, which may
lead to failure to seal the AAA sac (“endoleak”). Current recommendations are to
oversize the proximal part of the graft by 10–20 per cent and the limb diameters by
10 per cent. [Q5: C]
Most current devices for endovascular repair procedures depend on self-expanding stents or wireforms for attachment to the aortic wall. Most grafts are configured
so that there is a marking indicating the contralateral limb. Preoperative measuring
assessment of size is confirmed intraoperatively to prevent problems in length of
the limbs. After the graft has been implanted, a pigtail angiographic catheter is reintroduced, and a post-procedure digital subtraction angiogram is performed. The
contrast run is examined closely for the presence of extravasation of contrast, suggesting an endoleak. In some grafts, the aneurysmal sac will fill temporarily with
contrast due to porosity of the graft material. A retrograde angiogram through the
femoral sheaths is used to visualise a seal at the distal end of the graft. [Q6: A, B, C, D]
Complications of endoluminal AAA repair have been divided into remote/systemic and local/vascular. The remote/systemic complications are similar to, but less
frequent than, those occurring after open AAA repair. The local/vascular complications are more specific for the endoluminal repair (Table 3.1). [Q7]
The follow-up of endoluminal aneurysm repair patients remains important in
determining the long-term success of aneurysm exclusion. General recommendations include a physical examination and abdominal X-ray (AXR) plus contrastenhanced CT scan within 1 week, then 6, 12 and 18 months after operation, and
then annually. At present there are a number of registries such as Cleveland Clinic,
and a European collaboration (EUROSTAR) [9] indicating an annual mortality rate
of more than 1 per cent related to abdominal aortic aneurysms after endovascular
repair of AAA (EVAR). It appears that 15–25 per cent of deployed grafts will require
some secondary intervention. The requirement for secondary intervention is
greater for earlier generation grafts, compared with the newer devices. This appears
Table 3.1. Local/vascular complications after endoluminal repair
Injury to access arteries
Embolisation
Distal ischaemia
Renal failure
Endoleak
Type I (proximal or distal attachment zones)
Type II (lumbar or mesenteric collateral channels)
Type III (fabric tear or modular dislocation)
Endotension
Type IV (porosity leak)
Graft limb thrombosis
Groin wound infection
Conversion to open repair
32 Vascular Surgery
to be independent of the length of time the grafts remain in place. There is,
however, significant improvement in quality-of-life measurements in patients with
EVAR compared with open repair up to at least 6 months [10]. The importance of
the type II endoleaks is unclear. However, they have been known to reappear after a
period of absence. The position and the integrity of the graft is easily identified on
plain abdominal X-ray. Whilst the aneurysmal sac can vary over time with endovascular repair, an expanding aneurysmal sac in the presence or absence (endotension)
of endoleaks warrants further investigation and treatment. [Q8: B]
Case Analysis Quiz
A number of imaging examples are shown in Figs 3.5–3.8. Analyse the anatomical
suitability of each case for the possibility of endoluminal graft repair of the AAA. In
particular, determine the favourable and unfavourable features shown.
Fig. 3.5. Aortic angiogram showing a very favourable anatomy for endovascular repair: the neck is straight and
long, without irregular features of the wall. In addition, the aneurysm sac is straight, and both iliac arteries are
non-aneurysmal and relatively straight.
Endoluminal Treatment of Infrarenal Abdominal Aortic Aneurysm 33
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Fig. 3.6. In this case, the aortagram shows neck angulation of about 45°, and the neck has a reversed taper configuration. Both these features are considered to be unfavourable for endoluminal treatment because it is more
difficult for the device to achieve complete seal and reliable fixation).
a
Fig. 3.7. Three-dimensional reconstruction of contrast-enhanced CT scan showing severe iliac angulation: a
lateral view, b antero-inferior view. The iliac arteries show angulation in at least three different planes. The right
common iliac artery is also aneurysmal. These features are unfavourable for access of the deployment sheath,
and are associated with a higher risk of distal endoleak.
b
34 Vascular Surgery
Fig. 3.8. Aortic angiogram showing a 90° angulation within the neck of the aneurysm. This is considered to be
unsuitable for endovascular repair, since it is difficult to achieve satisfactory seal of the AAA sac or long-term
attachment of the device.
References
1. Melton LJ 3rd, Bickerstaff LK, Hollier LH, Van Peenen HJ, Lie JT, Pairolero PC, et al. Changing incidence of abdominal aortic aneurysms: a population-based study. Am J Epidemiol 1984;120:379–86.
2. Jaakkola P, Hippelainen M, Farin P, Rytkonen H, Kainulainen S, Partanen K. Interobserver variability in measuring the dimensions of the abdominal aorta: comparison of ultrasound and computed
tomography. Eur J Vasc Endovasc Surg 1996;12:230–7.
3. Fillinger M. Computed tomography and three-dimensional reconstruction in evaluation of
vascular disease. In: Rutherford RB, editor. Vascular surgery, 5th edn. Philadelphia: WB Saunders,
2000;230–69.
4. Rutherford RB, editor. Vascular surgery, 5th edn. Philadelphia: WB Saunders, 2000.
5. Greenhalgh RM, Brown LL, Kwong GP, Powell JJ, THompson SG. Comparison of endovascular repair
with open repair in patients with AAA (EVAR trial 1) 30 day operative mortality results: randomised
controlled trial. Lancet 2004;364:843–8.
6. Prinssen M, Verhoeven ELG, Buth J, Cuypers PW, van Sambbek MR, Balm R, et al. A randomized
trial comparing conventional and endovascular repair of abdominal aortic aneurysms. N Engl J Med
2004;351:1607–18
7. Ahn SS, Rutherford RB, Johnston KW, May J, Veith FJ, Baker JD, et al. Reporting standards for
infrarenal endovascular abdominal aortic aneurysm repair. J Vasc Surg 1997;25:405–10.
8. Prinssen M, Wever JJ, Mali WP, Eikelboom BC, Blankensteijn JD. Concerns for the durability of the
proximal abdominal aortic fixation from a 2-year and 3-year longitudinal computed tomography
angiography study. J Vasc Surg 2001;33:S64–9.
9. Van Marrewijk CJ, Buth J, Harris PL, Norgren L, Nevelsteen A, Wyatt MG. Significance of endoleaks
after endovascular repair of abdominal aneurysms: the EUROSTAR experience. J Vasc Surg
2002;35:461–73.
10. Prinssen M, Buskens E, Blankensteijn JD, DREAM trial participants. Quality of life after endovascular and open AAA repair. Results of a randomised trial. Eur J Vasc Endovasc Surg 2004;27:121–27.
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