Abdominal Aortic Aneurysms AAA

1
Abdominal Aortic Aneurysms(AAA)

• Marc Gibber
• Resident Conference
• November 2, 2005

2

• Presentation
• Diagnosis
• Management
• Open repair vs. EVAR
• Complications

• History
• Anatomy
• Pathology
• Epidemiology
• Risk factors

• Questions

3
History

• Most common true aneurysm
• High propensity to rupture
• US rupture
• 15th leading cause of death overall
• 10th leading cause of death men gt 55 y/o
• gt8500 hospital deaths annually
• 30-40 of ruptures die before operation
• 40-50 operative mortality rate
• 80-90 overall mortality rate
• Unchanged over 20 years

4
History

• Elective Repairs
• One of most common vascular procedures
• 40,000 operations annually
• lt5 elective surgical mortality rate
• Ruptures
• 50 million cost to society annually
• 2,000 lives saved if repaired electively
• 24,655/pt mean financial loss to hosp.

5
Aorta

• Normal male adult
• Gradually decrease from thorax to infrarenal
  location
• Thorax 28 mm in men
• Infrarenal 20 mm in men
• 2 mm larger in men than women
• Increase
• Age
• Male gender
• AA race
• Increasing height
• Increasing weight
• Increasing body mass
• Increasing body surface area
• Lederle et al J Vasc Surg 26595,1997

6
Aneurysms

• gt50 permanent focal dilation
• Abdominal Aorta
• 3-cm
• Iliac Artery
• 1.8 cm
• Clinical Practice
• 50 enlargement compared to adjacent
  nonaneurysmal artery
• Shape
• Mostly fusiform
• Others saccular and eccentric

7
Definitions

• Ectasia
• Focal dilation lt 50 of the normal expected
  diameter
• Arteriomegaly
• diffuse (nonfocal) enlargement of several
  arterial segments, with increases in diameter gt
  50 of expected diameter.
• may be considered aneurysmal if the diameter of a
  segment is increased by gt 50 of the diameter of
  an adjacent segment
• Aneurysmosis
• multiple aneurysmal segments separated by either
  normal, occluded, or arteriomegalic segments

8
Pathogenesis

• Originally hypothesis Atherosclerosis
• Elderly age and atherosclerosis present
• Fails to explain occlusive dz that is present
• Current etiologies
• Structural
• Hemodynamic
• Autoimmune
• DEGENERATIVE D/O

9
Structure

• Matrix protein Elastin and Collagen
• Organized in layers to withstand pressure
• Gradual reduction in medial elastin
• Proximal thoracic aorta 60-80 layers
• Infrarenal aorta 28-32 layers
• 58 decrease in elastin suprarenal to infrarenal
• Only area with less elastin than collagen
• medial thinning and intimal thickening
• Elastin ½ life of 40-70 years
• Not synthesized in adults

10
Hemodynamics

• Increased pulsatility and wall tension
• reflected waves from bifurcation
• Increased peripheral resistance
• Increased prevelance after AKA

11
Enzymatic Degradation

• Increase in expression and activity of Matrix
  Metalloproteinases (MMP)
• 3-fold increase in MMP-9 in 5-7 cm AAA
• Increase in serine proteinases
• Plasmin, neutrophil elastase
• Inhibitors unchanged
• Animal Studies
• Elastase infusion recruits inflam. Rxn gtAAA
• prevented by inh. Infl. Cells and blocking MMP

12
Epidemiology

• Disease of elderly white males
• Aneurysm
• 3-117 per 100,000 person years
• Men women 51
• White AA 3.51
• Gender
• Men 10 years earlier (50 y/o vs 60 y/o)
• Prevalence
• more accurate than incidence 2º u/s screening
• 3 cm 3-10 in autopsy survey gt 50 y/o
• VA screening study in 1997
• 3cm 4.6
• 4cm 1.4

13
Risk Factors

• Smoking
• 5.6 X for AAA 4cm
• 78 of all AAA 4cm
• ? risk with ?
• ? w/ ? depth inhalation
• ? w/ ? MAP and DBP
• Male Gender
• 4.5 X risk
• Family History
• 2X risk
• Age
• Height

• CAD
• Hypercholesterolemia
• HTN
• Systolic
• Diabetes
• .5 X Risk
• Heart transplants
• ? prevalence expansion
• mechanism remain unclear
• obligatory chronic immunosuppression may
  contribute

14
The Aneurysm Detection and Management (ADAM)
15
Risk Factors

• AAA
• 5 to 15 develop 2nd in aorta or iliac
• develop anywhere commonly within the residual
  infrarenal aortic cuff
• Survailance with computed tomography (CT) of the
  chest, abdomen, and pelvis 5 years or sooner
  after repair
• lt 5 chance of having a peripheral artery
  aneurysm,
• evaluation beyond physical examination is not
  justified
• Popliteal or femoral artery aneurysms
• 50 incidence of aneurysms in the abdominal aorta
  or iliac vessels
• CT of the entire aorta and iliac vessels to r/o a
  synchronous aneurysm

16
Family Clustering

• 1rst º relative with AAA
• 15-25 vs 2-3 w/o AAA have AAA
• Siblings have AAA
• ? if U/S screening is performed
• male siblings gt 55 25 had AAA 3cm
• female siblings gt55 7 had AAA 3cm
• Increased risk if proband is female
• 12 vs 7 to sibling or parent
• Females with family history
• 35 vs 14 w/o f.hx

17
Presentation

• Most asymptomatic
• Pt. describes pulse in abdomen
• Palpate pulsatile mass
• Obesity vs thin pt
• HTN, tortuous aorta, wide pulse pressure
• Physical Exam
• PPV of 15 AAA gt 3.5 cm
• Chervu et. al.
• 38 initially detected on PE
• 62 detected on incidental radiologic studies
• 23 not palpable even when dx known
• 2/3 of obese pt not palpable

18
Symptoms

• Rupture most common cause of symptomatic AAAs
• Anterior Rupture (20 of ruptures)
• Abrupt pain
• Abdominal or back pain
• Radiating into groin or flank
• Hypotension
• Transient hypotension to frank shock
• Pulsatile abdominal mass
• If not obscured by obesity or abdominal
  distension
• Usually tender
• All 3 symptoms in only 26
• Temporary LOC
• w/ pain 50
• w/o pain 17

19
Symptoms

• Posterior Rupture
• 80 of ruptures
• Contained by retroperitoneal space
• Contained hematoma ? may persist for days or
  weeks
• Back or vague abdominal pain
• Distal Embolization
• Acute ischemic symptoms
• 2-5
• more common in smaller AAA
• livedo reticularis of the feet
• ie, blue toe syndrome

20
AAA Complications

• Infected AAA
• Primary (nml aorta)
• gt1
• Salmonella and Staph. Aureus
• Secondary (AAA)
• Up to 37
• Minimal significance
• nml flora (Staph., Cornybacterium, Strep.
  Faecalis)

• Fistula
• 1º AV fistula
• AAA to Vena Cava
• Bruit gt 50
• CHF
• 1º AE fistula
• rare
• 4th portion duodenum
• GI bleeding? shock

21
Diagnosis

• Ultrasound
• Computer Tomography (CT)
• Spiral CT
• Magnetic Resonance Imaging (MRI)
• Magnetic Resonance Angiography (MRA)
• Arteriography

22
Ultrasound

• Abdominal B-mode
• Least expensive
• 84 interobserver variability lt5
• Disadvantages
• suprarenal and iliac A
• Obese
• Rupture
• underestimates by 2-4 mm
• W/u of suspected AAA
• Serial evaluation lt 4cm

• Screening
• ? rupture rate by 55 in men
• Debate about screening programs
• Cost-effective in male gt 60 y/o who smoke or
  other high risks

23
Computer Tomography

• Gold Standard
• Dx
• Serial Evaluation AAA gt 4cm
• More Accurate
• 91 interobserver variability lt5
• Precisely defines proximal and distal extent
• More accurate or Iliac A.
• Exclude rupture in stable but symp. pt.
• Detect other pathologies
• I.e. inflammatory aneurysm
• Disadvantages
• More expensive
• Involves radiation and requires contrast
• Overestimates if oblique angle

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25
Spiral CT

• Thinner slices
• Appreciate visceral aortic branches
• 3-D reconstruction
• More accurate measurements
• Endovascular sizing
• Study of choice for Dx and pre-op
• Accurate size and definition of vessel
  relationships
• Identify anomalies
• Identify other pathologies
• Identify aortic wall calcifications

26
Magnetic Resonance

• MRI
• Accuracy comparable CT
• Avoids radiation and contrast
• Disadvantages
• More expensive
• Less available
• Claustrophobic
• Contraindicated w/ metallic devices

• MRA
• pre-op for adjacent arteries

27
Arteriography

• Indications
• Perirenal Aneurysms
• Renal Vascular Hypertension
• Mesenteric Ischemia
• Previous Colon Surgery
• v Celiac and SMA
• Distal Occ. Dz
• Endovascular planning

28
Natural History

• The tangential stress (t) of a fluid-filled
  cylindric tube is determined by the following
  equation
• P is the pressure exerted by the blood
  (dyne/cm2)
• r is the internal radius (cm)
• d is the thickness (cm) of the arterial wall
• Normal Vessel (2cm)
• Wall thickness 0.2 cm
• Internal radius of 0.8 cm
• Fluid pressure of 150 mm Hg
• tangential stress an and a would be 8 x 105
  dyne/cm2
• Aneurismic Vessel (6cm)
• Wall thickness 0.06 cm
• Internal radius of 2.94 cm
• Fluid pressure of 150 mm Hg
• Tangential stress 98 x 105 dyne/cm2.

• 12-fold increase in tangential stress

29
Rupture Risk

• Universally accepted related to size
• 1966 Szilagyi compared lt6 cm to gt6 cm
• f/u rupture rate 43 vs. 20
• 5-year survival 6 vs. 48
• 1977 Darling analyzed AAA autopsy
• 473 consecutive AAA pts., 25 ruptured
• lt 4 cm 10
• 4-7 cm 25
• 7-10 cm 46
• gt10 cm 61

30
Risks for Rupture

• AAA Diameter
• Laplaces Law
• Absolute or relative size
• HTN
• Laplaces Law
• 54 vs 28
• COPD
• proteinase imbalance
• Emphysema 67 vs. 42
• Bronchiectasis 29 vs. 15
• Smoking
• Cigarettes 4.6 X
• Cigars 2.4X
• Hand-rolled cigarettes 14.6X

• Family Hx
• First degree relatives (FDR)
• 2 FDR 15
• 3 FDR 29
• 4 FDR 36
• Womengt men
• 30 vs. 17
• Increase in rupture rate
• 32 vs. 9
• Younger rupture age
• 65 y/o vs. 75 y/o

31
Rupture Risk
Increased by COPD, smoking, HTN, family history
and rapid expansion
32
Medical Management

• Smoking Cessation
• BP Control
• Beta-blockade with Propanolol
• ? plasminogen activators and MMP activation
• Periodic Exams
• U/S
• CT if close to surgical threshold

33
Surgery

• Indications
• Symptomatic pt.
• Almost universally
• Asymptomatic pt.
• 4-5 cm
• young low surg. risk
• High rupture risk
• 5 cm most pts.
• 6-7 cm if high risk
• Rapid Expansion
• gt 5 cm in 6 months

• Elective Surgery Risks
• Elective surgery mortality lt 5 (4-10)
• Independent Risk Factors
• Renal Dysfunction
• CHF
• ECG ischemia
• Pulmonary Dysfunction
• Age
• Female Gender

34
Surgical Repair

• Open vs Endo.

35
Open Repair

• Incision
• Transperitoneal
• Midline
• Rapid, wide access
• Pulmonary complications
• hernias
• Transverse
• Indications
• ruptured AAA,
• uncertain dx.
• coexisting abd pathology,
• L Vena Cava,
• lg bl iliac aneurysms

36
Open Repair

• Incision
• Retroperitoneal
• ? Less pulmonary, SBO morbidity, ileus, IV Fluid
  req. post-op
• Indications
• Hostile abdomen,
• abd. Wall stoma,
• horseshoe kidney,
• suprarenal anastomosis,
• inflammatory aneurysm
• Visceral artery revascularization

37
Open Repair

• Aortic Clamping
• 1st in least dz area
• Longitudinal incision
• Horizontal incision
• Not complete
• Proximal anastamosis
• Distal anastamosis
• /- iliac revasc.
• Back-bleeding
• IMA ligation
• No SMA occlusive dz.
• Good sig. colon perfusion
• Lower Ext. assessment
• Protamine
• Aneurysm closure and omentum pedicle

38
Complications

• MI
• leading single-organ cause of early and late
  mortality
• 25
• Multisystem organ Failure
• 1 overall 57
• 1 cause visceral organ dysfunction

39
Complications

• Cardiac
• Most w/i 2 days
• Prevent with adequate preload, dec HR BP,
• Oxygen saturation and Hct
• Hemorrhage
• Proximal anastamosis
• Venous bleeding
• Iliac v. and l renal v. during exposure
• Post l renal v. or large lumbar vein
• Homodynamic Complications
• Clamping HTN causing MI
• Declamping hypotension

40
Complications

• Iatrogenic Injury
• Ureteral injury
• Double J stent
• Splenic Injury
• Splenectomy
• Enterotomy
• Prompt termination if Elective
• Pancreatitis

• GI complications
• Paralytic ileus
• Anorexia
• Periodic constipation and diarrhea
• Sigmoid colon ischemia

41
Complications

• Renal Failure
• Rare w/ adequate IVF
• Contrast or embolization related
• Distal Embolization
• Aortic mobilization or clamping
• microemboli
• Blue toes
• Venous Thrombosis
• PE and DVT
• Low ? 2º anticoagulation

• Paraplegia
• Spinal cord ischemia
• Collaterals from int Iliac A
• Artery of Adamkiewicz
• Low origin
• Hypotension
• Sexual Dysfunction
• Impotence, retrograde Ejaculation
• Reduced pelvic blood, nerve damage
• 25

42
Late Complications

• 7 w/i 5 years of surgery
• lt10 life long
• Pseudoaneurysm (3 years)
• Aorta 0.2
• Iliac 1.2
• Femoral 3
• Graft Infection
• Aortoiliac 0.5
• Present 3-4 years post-op
• Early femoral

• Aertoenteric Fistula
• Secondary (post-op)
• 0.9
• years post-op
• Duodenum to prox. Suture line
• Presentation GI bleeding
• Thrombosis of graft
• 35 after 10 years
• Secondary Aneurysms
• 5 _at_ 5 years post-op

43
Endovascular Repair

• Indications
• High risk pt, D gt 6 cm
• Risk of rupture gt repair
• Alternative to open repair
• Criteria
• Aorta collar gt15mm
• Anuerysm diameter lt 28mm
• Angulation gt 120º (90º in iliac aneurysm)

44
Complications

• Arterial injury
• Iliac, Suprarenal
• Emboliazation
• Microembolization and renal failure
• Post Implant syndrome
• Back pain, fever w/o infection
• POD 0-7
• Unknown etiology
• Incidence up to 50
• Graft Limb Thrombosis
• Artery dissection
• Endograft kinking in Iliac A.
• Endograft kinking in Aneurysm Sac

45
Endoleaks

• Catagories
• Type I
• Seal failure
• Type II
• Retrograde flow
• Type III
• Graft defect
• Type IV
• Fabric Porosity

• Incidence
• Up to 45
• Natural hx
• 50 seal spontaneously
• Type 2 gt 1
• Management
• Observation
• Further Endovascular procedure
• Surgical band ligation
• Conversion to open repair

46
EVAR Post Surgery

• Follow Up
• 1 week, 6 12, 18 months
• Morphology Changes
• Sac reduction
• Enlargement if endoleak
• Increase diameter of proximal neck
• Conversion to Open
• Aortic Rupture
• Endograft migration and obstruction
• Persistent endoleak
• Infected graft

47
?
48
Question 1

• Excluding intracranial aneurysms, the most common
  site of aneurysm formation is
• A) Thoracic aorta
• B) Infrarenal abdominal aorta
• C) Superior mesenteric artery
• D) Common femoral artery

49
Question 2

• Which of the following statements is/are true
  with respect to AAA?
• A) White men have a threefold higher incidence
  than do black men
• B) Patients with a family history of AAA among
  first-degree relatives are more likely to have
  AAA
• C) The peak prevalence of AAA is 10 to 15 years
  later among women than it is among men
• D) Patients with AAA tent to be taller and older
  than typical patients with atherosclerosis and
  occlusive disease

50
Question 3

• Which of the following characterize(s) the
  histologic and histochemical features of AAA?
• A) A decrease in the amount of elastin
• B) Marked adventitial inflammatory cell
  infiltration
• C) More immunoglobulin in extracts from aneurysms
  than in normal aorta
• D) Decrease in elastin content directly
  correlates with the size of the aneurysm

51
Question 4

• Which of the following is/are true with respect
  to aortic elastin?
• A) Numerous studies have confirmed deficiency
  within aortic aneurysms however, the amount of
  collagen has been found to be normal, decreased,
  or increased
• B) Human tissues do not generate much new elastin
  after the first decade of life
• C) Vessels treated with elastase dilate and
  become less compliant
• D) Glycine makes up one third of the amino acids
  of elastin

52
Question 5

• Which of the following statements is/are true
  regarding elastin in aortic tissue?
• A) Elastin is arranged in layers
• B) The number of lamellae in the abdominal aorta
  of humans is disproportionately low for the load
  that is must bear (compared with other mammalian
  species)
• C) The estimated half-life of elastin is
  approximately 70 years
• D) Elastin is synthesized solely by mesothelial
  cells

53
Question 6

• Which of the following is/are true with respect
  to fibrillin, an important structure of the
  extra-cellular matrix?
• A) Fibrillin acts as the scaffolding for the
  deposition of elastin during elastogenesis
• B) Fibrillin mutations cause Marfans syndrome
• C) The gene for fibrillin is located in the long
  arm of chromosome 15
• D) Fibrillin is important in the pathogenesis of
  AAA

54
Question 7

• Which of the following is/are true regarding
  extracellular matrix proteins?
• A) Elastase activity is increased in AAA tissue
• B) Colagenase activity is increased in AAA tissue
• C) Matrix metalloproteinases are present in
  tissue from AAA
• D) The level of tissue plasminogen activator has
  been found to be elevated in AAA

55
Question 8

• Which of the following findings suggesting
  inflammation have a role in AAA?
• A) Increased concentration of T and B lymphocytes
  and macrophages in the adventitia
• B) Recognition that levels of interleukin-1ß and
  TNFa are higher in AAA extracts than in control
  substances
• C) A specifine IgG immunoglobulin directed
  against aortic wall antigen
• D) Control of aneurysm size with administration
  of aspirin

56
Question 9

• Which of the following is/are associated with
  risk of development of abdominal aortic aneurysm
  ?
• A) Smoking
• B) Family history of first-degree relative with
  an AAA
• C) Heart transplant
• D) History of intracranial aneurysms
• E) Portal hypertension

57
Question 10

• Which of the following statements is/are true in
  relation to the presentation and evolution of
  AAA?
• A) Most patients have compressive symptoms due to
  the mass effect of the aneurysm
• B) Abdominal ultrasound remains the most cost
  effective test to evaluate for ruptured AAA
• C) Computed tomography is the contemporary
  standard for determining aneurysm suitability for
  endovascular repair
• D) Angiography provides consistent overestimates
  of AAA diameter because of parallax magnification
  effects
• E) Indications for angiography before elective
  repair of AAA include concomitant lower extremity
  occlusive disease, suspicion of reno-vascular
  hypertension, or presence of a horseshoe kidney

58
Question 11

• Which of the following statements is/are true
  regarding the contemporary therapeutic
  considerations and option for management of AAA?
• A) Good risk patients with AAAs larger than 5 cm
  in diameter and a life expectancy of at least 2
  years should be offered elective repair
• B) Patients may be offered endoluminal repair but
  only under a U.S. Food and Drug Administration
  approved investigational device protocol
• C) Hospital length of stay, operative blood loss,
  and costs are equivalent for standard open and
  endoluminal repair of AAA
• D) Endovascular repair of AAA has been shown to
  prevent aneurysm rupture in the long term and is
  comparable with standard repair
• E) All patients with symptomatic or ruptured AAAs
  should undergo surgical repair provided quality
  of life and life expectancy are reasonable

59
Question 12

• Match each endoleak type with the appropriate
  description
• A) Type I
• B) Type II
• C) Type III
• D) Type IV
• 1. Patent lumbar artery
• 2. Bleeding through pores in graft material
• 3. Leak at proximal attachment site
• 4. Delayed distal limb migration with leak at
  distal anastomosis
• 5. Leak between components of a modular endograft

60
Question 13

• Which of the following statements is/are true
  regarding the preoperative evaluation and
  optimization of patients undergoing elective
  repair of AAA?
• A) Perioperative ß blockade improves outcome
• B) Routine pulmonary function tests improve
  outcome
• C) Coronary arterial occlusive disease is
  uniquely uncommon among these patients, who tend
  to have aneurysmal rather than occlusive disease
• D) For typical infrarenal aortic aneurysms,
  preoperative imaging with ultrasound alone is
  sufficient and avoids the radiation and contrast
  exposure associated with CT
• E) Preoperative angiography is indicated before
  repair for patients with renal anomalies or
  suspected renal vascular hypertension

61
Question 14

• Standard maneuvers for elective open repair of
  intact infrarenal AAA include which of the
  following?
• A) Permissive hypothermia to decrease the basal
  metabolic rate of the lower extremities during
  clamping
• B) Exclusive use of the transperitoneal approach
  in operation on patients with abdominal wall
  stomas to allow direct dissection of the bowel
  under direct vision
• C) Reimplantation of the inferior mesenteric
  artery only if vigorous backbleeding is
  encountered after the aneurysmal sac is opened
• D) Implantation of a bifurcated aortobifemoral
  prosthetic graft for reconstruction if either
  common iliac artery is larger than 2.0 cm in
  diameter
• E) Abandonment of the repair if sigmoid colotomy
  is made before graft implantation, even if the
  patient has undergone mechanical pre-operative
  bowel preparation

62
Question 15

• Which of the following clinical circumstances and
  operations are reasonable approaches for an
  otherwise healthy 60 year-old man?
• A) Isolated 4-cm common iliac artery aneurysm
  managed by means of aortobiliac prosthetic graft
  reconstruction
• B) 5.5 cm AAA with a 1 cm thick wall, medial
  deviation of the ureters, and chronic back pain
  requiring narcotics managed by means of AAA
  repair by the retroperitoneal approach
• C) 5 cm AAA and nearly obstructing cancer of the
  left colon managed by means of staged repair of
  AAA and colonic lesion with colectomy performed
  first
• D) 7 cm suprarenal AAA with renovascular
  hypertension from left renal artery stenosis
  managed by means of a retroperitoneal approach to
  AAA repair and simulaneous left renal
  revascularization
• E) 3.5 cm AAA with horseshoe kidney managed by
  means of elective repair after angiography by a
  retroperitoneal approach

63
Inflammatory aneurysm

• A distinct clinical entity
• 5 of infrarenal AAA
• 5-10 years younger 1 cm larger
• Genetic component
• More common family hx.
• HLA-DRB1 alleles B115 and B10404
• Thickening of aneurysmal wall
• Advential fibrotic inflamatory infiltration w
  lymphocytes monocyte
• Presentation
• abdominal or back pain, abdomen tenderness on
  palpation, weight loss, elevated erythrocyte
  sedimentation rate (ESR)
• Diagnosis
• CT scan with periaortic inflammation and fibrosis
  and occasional ureteral obstruction
• Treatment same as non-inflammatory AAA

64
Infectious

• Histologically
• Chronic adventitial and medial inflammatory
  infiltrate
• Different than occlusive dz
• Inf. Rxn in intimal plaques
• Source
• Chlamydia Pneumonia in AAA walls
• B-lymphocytes, plasma cells, immunoglobulin
• Suggest autoimmune component

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THE END