JC03 (Surgery) - Aortic Aneurysm Flashcards
Define aneurysm
□ Definition: permanent localized dilatation of an artery
with 50% increase in diameter
Classify 4 main types of aneurysms by form
□ Fusiform: circumferential dilatation (more common)
□ Saccular: bulging only involves part of circumference
□ Dissecting: Blood enters space within media (false lumen)
□ Varicose aneurys: tortuous dilatation
Classify true and false aneurysms
True:
Lined by intact attenuated vessel wall formed by all 3 layers (intima, media, adventitia)
False/ pseudo:
Lined by laminated thrombus and compressed fibrous tissue
Classify aneurysms by etiologies
□ Atheromatous: commonly affects abdominal aorta, popliteal and femoral arteries
□ Mycotic: aneurysm resulting from microbial arteritis
(subacute bacterial endocarditis, bacteremia)
□ Traumatic (a/w false aneurysms)
□ Connective tissue diseases, eg. Marfan’s syndrome
□ Others: syphilitic, congenital, anastomotic (at AV fistulas)
Most common form of aneurysm
true fusiform atherosclerotic aneurysms
Complications of aneurysms
→ Compression, eg. RLN compression by thoracic aortic aneurysm
→ Thrombosis and embolism
→ Infection
→ Rupture
Most common location of abdominal aortic aneurysm
Area between infra-renal artery area and the bifurcation of aorta
95% with associated atherosclerosis (strong association but not pathogenic)
Etiology of AAA
Multifactorial, loss of vascular structural proteins leading to loss of wall strength
□ Mechanical: degeneration (old) , hypertension
□ Smoking: Enhanced proteolytic activity of matrix metalloproteinase (MMP) → dissolution of arterial wall ECM
□ Connective tissue disease e.g. Marfan’s syndrome
□ Cystic medial necrosis
□ Postsurgical anastomotic disruption
□ Vasculitis
□ Mycotic aneurysm (Staph aureus, Syphillis, Salmonella, fungal infections)
Symptoms of AAA
Due to local compression:
- Pain at abdominal, back due to stretching of aneurysm sac
- Radicular pain in thigh and groin (esp in distal aneurysms, due to nerve compression)
- GI, urinary, venous obstruction
Due to distal embolization → acute ischaemic limb
Classical Triad of symptoms for AAA rupture
→ Severe abdominal and/or back pain
→ Hypotension
→ Pulsatile abdominal mass
How to define location of AAA in PE
Confirm AAA:
→ Mass above umbilicus
→ Expansile pulsation
Upper and lower border
- Can get above → infrarenal
- Can get below → does not involve iliac artery
Modalities of imaging for AAA (3)
Plain C/AXR: calcified rim + widened mediastinum
USG
CT angiogram: surgical planning
Management options for AAA ** (conservative and surgical)
Conservative management:
- Active surveillance by USG every 6 months, elective repair >5.5cm
- Lifestyle: smoking cessation, ↑exercise
Surgical management:
□ Open repair: aneurysmectomy + inlay graft
□ Endovascular aneurysm repair (EVAR):
aortic stent graft ± IIA embolization
Growth rate and rupture risk of AAA per year
Growth rate: ~5mm/y
Risk of rupture at 5y: 20% if <5cm, 50% if >5cm
Indications for surgical management of AAA
Size: >5cm to 5.5cm diameter
Increase in aneurysm size by > 0.5 cm within 6 months, regardless of size
Chronic abdominal pain/ impeding rupture
Thromboembolic complications present
Iliac or femoral artery aneurysm that causes lower-limb ischemia
(Aneurysms > 4.5 cm in patients with Marfan syndrome)
Contraindications to surgical management of AAA
All AAA >5cm should be operated on unless
→ Medically unfit (operative mortality > risk of rupture)
→ Limited life expectancy
Compare efficacy of open vs EVAR surgery for AAA
EVAR generally has
→ Better short-term outcome
→ Similar long-term outcome due to durability issue, higher re-intervention rate
Outline pre-operative preparation for AAA repair
1) General: blood tests, ECG, CXR
2) CTA: assessment of anatomy for any variants, eg. horseshoe kidney, retro-aortic renal vein
3) Cardiac: assessment or intervention
4) Transfusion prep: T/S and 6 units of blood ready
5) Thromboprophylaxis: IV heparin (to prevent trash limb) ± IV protamine after surgery
Complications that cause the highest mortality in AAA repair
MI due to stress by clamping/declamping (leading cause of early postoperative death)
Respiratory: ARDS
acute kidney injury (leading cause of late postoperative death)
Early complications of Open AAA repair
Hemorrhage
Iatrogenic injury to internal organs
Tissue ischemia:
- Bowel ischemia (ligation of mesenteric vessels, esp. colon)
- Paraplegia after spinal ischemia (ligation of costal or lumbar arteries in throacic AA)
- Sexual dysfunction (ligation of retroperitoneal vessels)
- Trash foot (ligation of iliac arteries)
- Renal failure (embolism and decrease renal perfusion)
Late iatrogenic complications of Open AAA repair (3)
Graft infection
Anastomotic aneurysm
Graft-duodenal fistula
Early graft-related complications of EVAR AAA repair
Entry site: thrombosis, dissection, haematoma, embolization
Retroperitoneal haematoma
Endoleak: persistent flow into aneurysm sac after EVAR
Graft migration (proximal aortic neck dilatation)
Separation of components
Graft limb kinking and occlusion
Endograft infection
Systemic complications of EVAR AAA repair
Cardiac: MI
Respiratory: ARDS
Contrast-related: allergy, nephropathy
Ischemia: visceral organs, spine
Post-implantation syndrome: inflammatory for 7-10 days, self-limiting
4 sites of AAA rupture
Retroperitoneal (80%), i.e. left posterolateral wall 2 to 4 cm below the renal arteries. most common*
Intraperitoneal (20%), i.e. anterior rupture
Duodenal (rare)
IVC (rare)
Signs of retroperitoneal or intraperitoneal bleeding from ruptured AAA
→ Cullen’s sign: paraumbilical bruising
→ Grey Turner sign: flank bruising
→ Fox’s sign: ecchymosis of proximal thigh
→ Bryant’s sign: discoloration of scrotum
D/dx of retroperitoneal or intraperitoneal bleed
□ Ruptured mycotic aneurysm
□ Ruptured HCC (esp if young, AAA seldom occurs in <40y)
□ Ruptured ectopic pregnancy
Management of ruptured AAA
- Diagnosis: USG or CTA
- Resuscitation:
- Large bore IV cannula
- Cross-match blood, fresh frozen plasma (NO ADRENALINE)
- Achieve permissive hypotension* to limit bleeding - Surgery:
- Clamping of aorta
- Emergency repair:
EVAR (stable- CTA, unstable- Aortic balloon)
Open surgery (unstable)
Complications of ruptured AAA
□ Massive blood loss and transfusion-related S/E, eg. DIC*, hypothermia
□ Cardiorespiratory* complications due to haemodynamic stress
□ Ischaemic* complications:
→ Renal failure due to shock or suprarenal clamping
→ Bowel ischaemia: much higher risk than in non - ruptured AAA
□ Paralytic ileus* due to retroperitoneal haematoma
□ Abdominal compartment syndrome* due to reperfusion injury
Determinants of open vs EVAR AAA repair
Anatomical variance:
→ Neck: suitable length (>10-15mm), diameter (15-20% smaller than graft) and angulation (<60o) for graft landing zone
→ Iliac artery: adequate length (>15-20mm) and diameter (8-22mm) for graft landing
→ Access: minimal tortuosity and narrowing
→ Others: calcification, preservation of IIA
Define 5 types of Endoleaks
Type I and III - high pressure endoleaks
Type II - reflux leak from visceral arteries
Type IV - porosity of graft fabric
Type V - unknown cause
Types I and III are high-pressure leaks → warrant endovascular repair (eg. extension limb, aortic cuff)
