Etiology, pathology and management options for AAA

1. ---Dr. Anusha . M
Moderator: Dr. B. MohanLal Naik, M.S[Prof]
Dr. G. Konda Reddy, M.S[Asst]
Dr. B.Madhava Krishna, M.S[Asst]
Abdominal Aortic
Aneurysm

2. • It begins at the aortic
hiatus of the diaphragm,
anterior to the lower
border of vertebra T7.
• It descends to the level of
vertebra L4 it is slightly to
the left of midline.
• The terminal branches of
the abdominal aorta are
the two common iliac
arteries.
• Normal Diameter ranges from
16-22 mm.
Abdominal Aorta

3. Branches of Abdominal Aorta
Visceral Branches
• Celiac.
• Superior Mesenteric A
• Inferior Mesenteric A
• Middle Suprarenal artery
• Renals A
• Gonadal
Parietal Branches
• Inferior Phrenic A
• Lumbar A
• Middle Sacral A

4. • Dilatations of localised segments of the arterial system
are called ‘aneurysms’.
ANEURYSM
 True aneurysms --contain
the three layers of the arterial
wall in the aneurysm sac.
 False aneurysms -- a single
layer of fibrous tissue as the
wall of the sac as seen in
aneurysm following trauma.

5. Based on shape of the
aneurysm
Fusiform—uniform dilatation of
entire circumference of
arterial wall
Saccular—dilatation of part of
circumference of the arterial
wall

6. • Abdominal aortic aneurysm is the most
common aortic aneurysm; infra renal
segement is more prone for aneurysm
formation.
• Incidence is 2%. It is more common in
males.
• Transverse diameter of aorta in an
aneurysm should be 3 cm or more.
• Common in elderly; chance of getting
aneurysm in genetically related first
degree relatives is 10 times more.
• Common in smokers -- 8:1with
nonsmokers.

7. • Atherosclerosis (as degenerative process) is the
most common facilitating cause (95%).
• Familial aortic aneurysm (associated with 25% of
AAA) is more prevalent in females. It is related
to decrease in type III collagen, α1 antitrypsin
and lysyl oxidase. Marfan’s, Ehler Danlos
syndromes are related genetically.
• Others: Syphilis, aortic dissection, trauma,
collagen diseases, infection, arteritis, cystic
medial necrosis, association with Chlamydia
pneumoniae (55%).
ETIOLOGY

8. The wall of the mature aorta is composed of three
layers:
Tunia intima, with its single layer of endothelial cells;
Tunica media, made up of smooth muscle cells within a
structural protein matrix; ELASTIN is the main load
bearing part.
Tunica adventitia, a tough layer of collagen fiber and
fibroblasts.
PATHOPHYSIOLOGY

9. • In the thoracic aorta, the media contains 55 to 60
elastin lamellar units, with adventitial vasa vasora
penetrating the vascular zone of the outer layers,
whereas there are 28 to 32 elastin lamellar units in the
abdominal aortic media.
• This makes the abdominal aorta relatively avascular
compared with the more proximal aorta, relying more
on the trans intimal diffusion of oxygen and nutrients.

10. Proposed model for Protease mediated
aneurysm formation
(1) Thrombus within the lumen traps
Neutrophils. These Neutrophils release
proteases which diffuse into the media
causing breakdown of Collagen and Elastin.
(2) These proteases also kill vascular smooth
muscle cells (VSMCs). As VSMCs normally
release protease inhibitors and hence Protease
action is left unchecked.
Finally, angiogenesis within the adventitia, a
recognised feature of AAAs causes influx of yet
more protease producing leukocytes.

11. Net Result:
Decreased elastin, collagen and smooth
muscle within the aortic wall leading to
dilatation and possible rupture.
Matrix metalloproteinases (MMPs) and other
mediators of tissue enzyme function
participates directly in matrix protein
degradation.
The immune response has also been
implicated in the pathophysiology of
aneurysm formation

12. Development Expansion Rupture
Tobacco use Advanced Age Female gender
Hypercholesterolemia Severe Cardiac
Disease
↓ FEV1
Hypertension Previous Stroke Larger initial AA
diameter
Male Gender Tobacco Use Cardiac or renal
transplantation
Family History Cardiac Or
Renal
Transplantation
Higher mean blood
pressure
RISK FACTORS Current tobacco use
(length of time smoking
≫ amount)

13. Risk of Rupture
Predicting the behavior of an
aneurysm over time is difficult.
Risk factors for rupture include
-- chronic obstructive pulmonary
disease
--current tobacco use
-- larger initial AAA diameter
-- female gender
--cardiac or renal transplantation.
The most widely adopted surrogate
for rupture risk is maximal
cross-sectional aneurysm diameter

14. Clinical features
• Patients with AAAs are typically asymptomatic.
• It presents as back pain, abdominal pain, mass abdomen
which is smooth, soft, nonmobile, not moving with
respiration, vertically placed above the umbilical level,
pulsatile both in supine as well as knee-elbow position
with same intensity, resonant on percussion.
• Hypertension, diabetes, cardiac problems should be
looked for.
• Lower limb ischaemia and embolic episodes can occur.

15. • Gastrointestinal, urinary and venous symptoms
can also be caused by pressure from an
abdominal aneurysm.
• Aortocaval fistula, presents as high output cardiac
failure with continuous bruit in abdomen and
severe lower limb ischaemia .
• Aortoenteric fistula is due to erosion of aneurysm
into 4th part of duodenum presenting as GI bleed,
malaena, shock.
• Being a retroperitoneal mass back pain is
common—may be due to retroperitoneal
stretching, nerve irritation or vertebral erosion.

16. Differential Diagnosis
• Retroperitoneal mass ---pseudocyst of
pancreas, retroperitoneal cyst mimic
abdominal aortic aneurysm especially
when it is thrombosed.
• Mesenteric ischaemia, acute pancreatitis,
perforated duodenal ulcer may mimic
ruptured aneurysm.
• conditions causing back pain like disc
prolapse, sciatica.

17. Complications of abdominal aortic
aneurysm
• Rupture
• infection
• Thrombosis & embolism
• Distal ischaemia &gangrene
• Aortocaval fistula formation
• Aortoenteric fistula
• Erosion of vertebra
• Spinal cord ischaemia when thrombosis
develops

18. Investigations :
 Full blood count, electrolytes, liver function tests,
coagulation tests and blood lipid estimation should
be performed.
 Blood should be crossmatched a few days prior to
surgery.
 Anaesthetic assessment -- Cardiac and Respiratory
function tests.
An electrocardiogram and chest radiograph are
essential.
Further assessment may include echocardiography or
isotope ventriculography, cardiopulmonary exercise
testing and spirometry.

19. Ultrasound examination
has been demonstrated to
afford excellent sensitivity and
specificity.
Advantages: Non-invasive , no
risk of radiation, and contrast
media, it is an excellent choice
for screening.
Ultrasound is not an ideal
method for detecting rupture
as it is unable to image all
portions of the aortic wall,
It has been estimated that
ultrasound may fail to detect
up to 50% of aneurysm
ruptures.
ASSESSMENT OF MORPHOLOGY
OF ANEURYSM
Ultrasonogram of an aortic
aneurysm showing the large
clot-filled sac with a small central
lumen

20. Provides excellent imaging of
AAA compared to ultrasound.
CT, particularly with the adjunctive use of
iodinated contrast agents to perform CT
angiography (CTA) which provides
1)anatomic information
2) detects vessel calcification,thrombus
3)concurrent arterial occlusive disease
4)permits multiplanar and three-
dimensional reconstruction and analysis for
operative planning.
Drawbacks include substantial radiation
exposure, particularly in the setting of
serial examinations and the use of
iodinated contrast media in a population
with a high incidence of comorbid kidney
disease.4
Computed tomography
Infrarenal abdominal aortic
aneurysm demonstrating aortic wall
calcification and intraluminal
thrombus

21. • Magnetic resonance imaging and
magnetic resonance angiography
(MRA) are sensitive in the detection of
AAA.
• MRI does not demonstrate aorticwall
calcification, which is important in
operative planning.
• MRA uses gadolinium, which has
been associated with the development
of nephrogenic systemic fibrosis in
patients with low glomerular filtration
rate.
• The availability of MRI may also be
limited by the presence of
incompatible metallic implants or
foreign bodies.
MRI
MRA coronal view of an
infrarenal aneurysm

22. Recommendations for Screening:
• Ultrasound is the screening modality of
choice.
Candidates for Screening:
 Men > 65yrs or > 55yrs with a family
history
 Women > 65yrs of age
 Family history of Aneurysm
 History of tobacco use

23. Once an aneurysm has been detected, the Society
for Vascular
Surgery Clinical Practice Council recommends
further screening intervals as follows, based on
aneurysm size i.e.., maximum external aortic
diameter and associated risk of rupture :
 <2.6 cm: no further screening recommended
 2.6-2.9 cm: reexamination at 5 years
 3-3.4 cm: reexamination at 3 years
 3.5-4.4 cm: reexamination at 12 months
 4.5-5.4 cm: reexamination at 6 months

24. Medical Management
• The current approach to the medical management of
infrarenal aortic aneurysms focuses mainly on small
aneurysms.
• Targeted mechanisms for potential medical management
include inhibition of immune function, dyslipidemia,
hypertension, connective tissue degradation, oxidative stress,
and vascular smooth muscle degradation.
• Multiple agents—including statins, angiotensin converting
enzyme (ACE) inhibitors, β-blockers, and antibiotics
including tetracycline and doxycycline—have been shown in
animal models to slow aneurysm progression. Effectiveness
has not been clearly demonstrated in humans.

25. • The size criterion for elective repair is 5.5 cm
for men and 5 cm for women or a 12-month
growth rate of equal to or greater than 10 mm
in both sexes.
• Additional indications for elective or early
intervention included saccular aneurysms,
dissection of mural thrombus, or fracture of
saccular calcification.
INDICATIONS FOR INTERVENTION

26. Identification and management of important
medical comorbidities, such as
 Coronary artery disease (CAD)
 Renal insufficiency
 Peripheral arterial occlusive disease
 Diabetes
 Obstructive lung disease
• Vitamin K antagonists should be stopped 5 to 7
days prior to surgery and bridging
anticoagulation provided, if indicated, using
LMWH or unfractionated heparin
Pre operative evaluation and management

27. Called as endo-aneurysmorrhaphy with intraluminal
graft placement
• Under general anaesthesia, with the patient lying supine, a
full length midline or supraumbilical transverse incision is
made.
• The small bowel is lifted to the patient’s right and the aorta
identified.
• The posterior peritoneum overlying the aorta is opened and
the upper limit of the aneurysm identified.
• The aorta immediately above the dilatation is exposed; this
is generally just inferior to the left renal vein and renal
arteries.
Open surgical procedure

28. • The common iliac arteries are then exposed and clamps applied
above and below the lesion.
• Aneurysm is opened longitudinally and back-bleeding from
lumbar and mesenteric vessels controlled by sutures placed from
within the sac.
• Upper and lower aortic necks are prepared to which an aortic
prosthesis is then sutured end to end inside the sac with a
monofilament non-absorbable Suture.
• Clamps are released slowly to prevent sudden hypotension. If
haemostasis is satisfactory at this point, the aneurysm sac is
closed around the prosthesis to exclude both it and the suture
lines from the bowel to reduce the risk of adherence and
potential fistula formation.
• The abdomen is then closed.
• When the iliac vessels are also involved with dilatation or severe
atheroma, it is necessary to construct an aortobi-iliac or
aortobifemoral bypass, rather than use a simple aorto-aortic
tube.

29. Posterior wall of the aorta immediately
above and below the sac is not divided.
A Dacron tube graft is laid in place
within the sac ready for suture.
Graft is sutured in place and
vascular clamps removed

30. Postoperative complications
The most common complications after open repair are
---cardiac (ischaemia and infarction)
---respiratory (atelectasis and lower lobe consolidation)
---colonic ischemia due to lack of collateral supply
---Renal failure
---Neurological--sexual dysfunction and spinal cord ischaemia.
---Aortoduodenal fistula –uncommon
--- Prosthetic graft infection
---Distal Thromboembolism
---DVT

31. Endovascular aneurysm repair
• About 50 per cent of infrarenal aneurysms are
suitable for EVAR.
• Common causes of unsuitability include a short,
flared or angulated neck and difficult iliac artery
access because of narrowing or tortuosity
• The endovascular prosthesis (‘stent graft’) is
usually made up of three separate parts – a main
body and two limbs which are enclosed in
separate delivery catheters .
• Some types have only two pieces – a main body
with ipsilateral limb attached and a separate
contralateral limb.
• The prosthesis is made from Dacron or PTFE
with integral metallic stents for support.

32. Endovascular prosthesis
main body
Endovascular
prosthesis main body
with separate limbs

33. • Expose both femoral arteries under general or local
anaesthetic which allows access to the aorta.
• Under radiological control, guidewires and catheters are
used to cross the aneurysm and an angiogram performed
to mark the level of the renal arteries.
• The delivery catheter is inserted in the aneurysm sac and
the stent graft deployed by withdrawal of the delivery
system.
• Inflate a moulding balloon catheter in the stent graft to
ensure the hooks and barbs are engaged to the aortic wall
and a good seal is obtained.
Technique:

34. • The top edge of the fabric of the stent graft has to be
deployed below the renal arteries i.e..,infrarenal
fixation ;
• Bare metal stents at the proximal end of the main
body lie across the renal arteries to give better
support and fixation i.e.., suprarenal fixation.
• Blood flows between the metal struts of the stent into
the renal arteries.
• Success is dependent on a good seal between the
stent graft and the proximal and distal ‘landing zones’
in the aorta and iliac arteries.

35. Endoleak
Most common indication for re-intervention after EVAR.
• Type I endoleak is defined as failure to achieve a
satisfactory seal at either the proximal (type Ia) or distal (type
Ib)seal zone, representing a failure to exclude the aneurysm
sac.
• Type I endoleak should be addressed at the time of
detection.
 Placement of additional graft components to extend the seal
zone
 Placement of balloon-expandable stents within the seal zone
• One FDA-approved device uses helical EndoAnchors
delivered with a deflectable sheath to address both type I
endoleak and migration

36. Type II endoleaks
• Most common form and represent continued filling of
the aneurysm sac by lumbar branches or the inferior
mesenteric artery.
• Treatment may include embolization of feeding
branches by selective catheterization (transarterial
technique) or direct sac puncture (translumbar
technique) or laparoscopic or open surgical ligation
of these vessels.
Type III endoleaks
• Represent failure of an individual component or of
the seal between components of a modular graft
system.
• All type III endoleaks should be treated, typically by
relining the offending area with new graft
components

37. Type IV endoleaks
• Represent seepage through porous graft material
and are typically self-limited, resolving when
procedural anticoagulation is reversed.
• An entity known as ENDOTENSION is sometimes
considered a fifth type of endoleak. This
represents persistent growth of the aneurysm sac
in the absence of a detectable leak. It is proposed
that this phenomenon is due to either the passage
of serous ultrafiltrate across an excessively
porous fabric or the existence of an undetected
endoleak of one of the prior types.

38. • Abdominal aortic aneurysms can rupture anteriorly
into the peritoneal cavity (20 per cent) or
posterolaterally into the retroperitoneal space (80 per
cent).
• Anterior rupture results in free bleeding into the
peritoneal cavity; very few patients reach hospital
alive.
• Posterior rupture on the other hand produce a
retroperitoneal haematoma .
• A brief period ensues when a combination of
moderate hypotension and the resistance of the
retroperitoneal tissues arrests further haemorrhage
and may allow transport to hospital.
Ruptured abdominal aortic aneurysm

39. • Ruptured abdominal aortic aneurysm is a surgical
emergency;
• It should be suspected in a patient with the triad of severe
abdominal and/or back pain, hypotension and a pulsatile
abdominal mass.
• Good venous access is needed for infusion of saline or
volume expanding fluids, but the systolic blood pressure
should not be raised more than is necessary to maintain
consciousness and permit cardiac perfusion (<100 mmHg).
• Resuscitative endovascular balloon occlusion of the aorta --
---This balloon is placed percutaneously to establish
proximal control in anticipation of open or endovascular
repair.
--- Initial wire access to the suprarenal aorta should be
followed by passage of a stiff guidewire and placement of a
sheath of sufficient size (14 Fr) to accommodate a large,
compliant occlusion balloon and length (40 cm) to
support the inflated balloon in a suprarenal position.

40. One and all