Mon 12-12-2005 OS Lecture 12 - Abdominal Aortic Aneurysm - Dr

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

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© 2005 Elsevier

Abdominal CT

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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