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Abdominal Aortic Aneurysm
Mark Sarfati MD
Assistant Professor of Surgery and Radiology
Division of Vascular Surgery
University of Utah School of Medicine
Hidden Lake, Glacier NP
Abdominal Aortic Aneurysm (AAA)
• Definition: focal dilation 1.5x greater than the normal diameter of the artery (>3 cm)
• True aneurysm (all 3 layers) vs. pseudoaneurysm
• Infrarenal abdominal aorta most common location
• Can involve suprarenal aorta, iliac arteries • Aortic dissection is different disease
AAA: Epidemiology
• Disease of ELDERLY WHITE MALES
• Male:Female ratio 3:1 to 8:1
• Incidence in females begins to approach that of males after 8th decade
• Incidence in black males, black females, and white females roughly equivalent
• Incidence has been increasing
AAA Incidence vs Age
Epidemiologic Risk Factors
• Smoking
• Hypertension
• Family History
AAA: Pathophysiology
• Typically said to be “atherosclerotic”• More accurately termed degenerative• Gradual reduction in the aortic wall matrix
proteins (elastin; collagen)• Degraded by local overexpression of
proteolytic enzymes (matrix metalloproteinases)
• Chronic adventitial and medial inflammatory infiltrate
Complications of AAA
• Progressive enlargement leading to rupture, exsanguination and death
• Tenth leading cause of death among men >65 years old
• Actual death rate likely exceeds 15,000 reported deaths annually, because sudden death is often mistakenly attributed to MI
Complications of AAA
• Rupture is the gravest and most common complication
• Other complications include:– peripheral embolization– aortic thrombosis– fistula formation
• Aorto-duodenal• Aorto-caval
– local compression/mass effect– hydronephrosis
AAA diameter predicts rupture risk
AAA Diameter Annual Rupture Rate
4.0 – 5.4 cm 0.5 – 1.0%
5.5 – 6.4 cm 10%
6.5 – 6.9 cm 19%
7.0 – 7.9 cm 32%
> 8.0 cm 50%
Importance of elective repair
• Ruptured AAA 90% mortality
• Elective repair <5% mortality
• Early diagnosis and elective repair can reduce mortality from AAA
• Screening high risk populations is cost effective and reduces AAA-related mortality
Teton Range, WY
Presentation of AAA
• Asymptomatic– Incidental finding
• Symptomatic– Present with sx but are not bleeding
• Ruptured– Symptomatic and bleeding
Asymptomatic AAA
• Incidental finding– Physical exam– imaging
• Goal of evaluation: Confirm AAA is asymptomatic
• Further evaluation and elective repair
Symptomatic AAA
• Hemodynamically stable
• Not bleeding
• Symptoms referable to AAA
• Varied presentation
• 50% AAA initially misdiagnosed
Symptoms
• Abdominal, back, flank pain
• Usually acute onset (+/- syncope)
• Radiation to thigh, groin, testicle
• Nonspecific
• May be due to sudden expansion of aneurysm or compression of adjacent structures
Ruptured AAA
• Back pain, hypotension, pulsatile abdominal mass
• Classic triad < 50%
• Any AAA with sx: assume rupture until proven otherwise
• Contained in retroperitoneum vs free intraperitoneal rupture
• Leaking = ruptured
Differential Diagnosis
• Acute abdominal pain
• Shock
• Back pain
• MI, pancreatitis, perforated viscus, mesenteric ischemia, renal/biliary colic, lumbosacral disc disease etc…..
Evaluation
• History: known AAA, fam hx
• Physical– Pulsatile abd mass– Epigastric– 25-50% not palpable
• Size AAA• Obesity• Focused exam
Physical Examination for AAA
Evaluation
• Lab studies– Rarely helpful– CBC, coags, BMP, type and cross
• Imaging– Confirm presence of AAA– Detect rupture
Imaging
• Plain films– Calcification– Cannot measure size or determine rupture– No role
• Ultrasound– Rapid/accurate dx of AAA– Does not exclude rupture– Role: rapidly confirm presence of AAA
Imaging
• CT– Accurate: dx, diameter, rupture– Risk: time delay, must leave ED, contrast
• Angio– Inaccurate dx, size– Risk: invasive, time delay, must leave ED,
contrast– No role in ED eval
Ultrasound
Downloaded from: Vascular Surgery 6/e (on 17 October 2005 08:13 PM)
© 2005 Elsevier
Abdominal CT
Downloaded from: Vascular Surgery 6/e (on 17 October 2005 11:17 PM)
© 2005 Elsevier
Ruptured AAA
Angio vs CT
Angio = luminogram
thrombus lumen
Management
• Asymptomatic AAA– Confirm that patient is asymptomatic– Measure maximum diameter of AAA
(ultrasound)– Consult vascular surgery for follow-up
Management: Symptomatic AAA
• Assume ruptured until proven otherwise• Immediate vascular surgical consultation• Cardiac monitor• Large bore IV access• O2• CBC, coags, BMP, Type and Cross 6 units• CTA after surgical evaluation• Admit for urgent/emergent repair
Management: Ruptured AAA
• Immediate vascular surgical consult
• Usually straight to OR without further diagnostic work-up
• Imaging contraindicated in unstable patient
• IV access, type and cross etc if does not delay OR
• Consider emergency release blood
Continental Divide, Glacier NP
Surgical Repair of AAA
• Open repair
• Endovascular repair
Open surgical repair of AAA
• General anaesthetic
• Laparotomy
• Retroperitoneum incised to expose AAA
• Aorta/iliacs clamped
• Aorta replaced with prosthetic graft
Endovascular repair of AAA
• Less invasive procedure
• AAA excluded from circulation with intraluminal stent-graft
• Endo has lower periop morbidity and mortality rates but may be less durable and requires more frequent follow-up than open repair
• Typically reserved for elderly or high risk patient
Endovascular Repair of AAA
• General, regional, or local anaesthetic
• Femoral arteries exposed
• Graft introduced through femoral arteries
• Guided into position by fluoroscopic imaging
• Deployed
Aortic Endograft
Aortic Endograft
Bilateral groin incisions
Aortic Endograft
Endoluminal graft insertion
Aortic Endograft
Pre and post endovascular repair
Going-to-the-Sun Road, Glacier NP
Aortic Graft Complications
• Graft thrombosis
• Anastomotic pseudoaneurysm
• Graft infection
• Aorto-duodenal fistula
Graft Thrombosis• Lower extremity ischemia with absent
femoral pulse• Unilateral or bilateral (bifurcated vs tube
graft)
Anastomotic Pseudoaneurysm
• History/evidence prior femoral anastomosis
• Pulsatile groin mass• Due to mechanical disruption of
anastomotic suture line (+/- infection)
Aortic Graft Infection
• Major complication with high morbidity and mortality
• Acute or chronic
• Indolent or fulminant
• Fever, chills, anorexia, weight loss, abdominal/back pain, graft thrombosis, pseudoaneurysm, sepsis, groin incision seperation/sinus tract
• CT: perigraft fluid, inflammation, gas
gas
Perigraft fluid
Aorto-duodenal fistula
• Aortic anastomosis erodes/ruptures into duodenum
• Massive hematemesis (preceded by herald bleed)
• Suspect in any pt with UGI bleed and history aortic surgery
• Surgical emergency
• High mortality
duodenum graft
Wind River Range, WY