Are localized abnormal dilations of arteries. Result due to weakening of the vessel wall. Have the tendency to rupture. Law of Laplace: states that as the diameter of aneurysm increases the wall stress increases : further enlargement and rupture is inevitable. Aneurysms are classified by: Location ( e.g abdominal aortic aneurysm) Etiology (e.g. syphlitic aneurysm) Shape (e.g. fusiform , saccular)

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2. 2
Aneurysms
Are localized abnormal dilations of arteries.
Result due to weakening of the vessel wall.
Have the tendency to rupture.
Law of Laplace: states that as the
diameter of aneurysm increases the wall
stress increases : further enlargement
and rupture is inevitable.
Aneurysms are classified by:
Location ( e.g abdominal aortic aneurysm)
Etiology (e.g. syphlitic aneurysm)
Shape (e.g. fusiform , saccular)

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The locations
of
aneurysms

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Causes of aneurysm
1. Atherosclerosis: MCC
causes arterial wall thinning due to
destruction of media
2. Cystic medial degeneration
3. Syphilis
4. Trauma
5. Polyarteritis nodosa (PAN)
6. Congenital defects : EDS, MS
7. Infections (also called mycotic aneurysms).

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Aneurysm complications
1. Rupture
2. Impingement on adjacent structures
3. Occlusion of proximate vessel
4. Embolism from mural thrombosis

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Abdominal aortic aneurysms (AAA)
Are complications of atherosclerosis
MC type of aneurysm (MC in men>55 yrs)
Usually located below the renal artery
orifices proximal to bifurcation
Pathogenesis:
1. Atherosclerosis weakens vessel wall:
(no vasa vasorum below renal artery
orifice).
Lumen of aneurysm fills with atheromatous
debris and blood clots.
2. Familial factors and structural defects in
connective tissue

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Abdominal aortic aneurysm

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Abdominal aortic aneurysms
Clinical findings:
Majority are asymptomatic
Symptomatic:
a pulsatile mass can be palpated.
Rupture: is the most common complication
Abrupt onset of severe back pain is
followed by hypotension from blood loss in
retroperitoneum and shock.
Diagnosis:
Abdominal ultrasound is the gold standard
test.

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Syphilitic aneurysm
Cardiovascular manifestation of tertiary
syphilis.
Usually occurs in men 40-55 years of age.
Is due to inflammation of aortic vasa vasorum.

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Syphilitic aneurysm: Pathogenesis
T.pallidum infects the vasa vasorum of the
ascending and transverse portions of aortic arch.
Causing endarteritis obliterans (of the vasa
vasorum).
Characteristic plasma cell infiltrate in vessel
wall.
Ischemia  focal necrosis and scarring of
media 
Dilation of the aorta and aortic valve ring.
Roughened intimal surface imparts a “tree
bark” appearance.

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"Tree-barking“ of aorta

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Syphilitic aneurysm
Clinical findings:
Aortic regurgitation with left ventricular
hypertrophy.
Bounding pulse: due to increased LVEDV 
Increased stroke volume.
Brassy cough: left recurrent laryngeal nerve is
stretched by the aneurysm.
Respiratory difficulty: due to airway
encroachment.
Rupture leads to rapid death.
Diagnosis:
Aortography
Calcification in the arch of aorta: highly
predictive of syphilitic aneurysm.

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Syphilitic aneurysm
"Tree-barking“ of aorta

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Mycotic aneurysm
Result from weakening of the vessel wall due
to a microbial infection.
Causes:
Septic embolism
Bacteria: Bacteroides, Pseudomonas
aeruginosa, Salmonella species
Infective endocarditis
Fungal vasculitis: Aspergillus, Mucor, Candida
are vessel invaders)
Clinical findings:
thrombosis with or without infarction,
rupture and hemorrhage.

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Berry aneurysm
Are small spherical
aneurysms most commonly
located at the bifurcation
of cerebral vessels.
Increased intravascular
pressure and weakness in
arterial wall lead to their
formation.
They can rupture and lead
to fatal Subarachnoid
hemorrhage.

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Berry aneurysm :Pathogenesis
Arise due to defect in cerebral vessels:
Vessels lack muscular layer at the point of
bifurcation
Pressure at the weak point
Loss/degeneration of internal elastic
membrane 
Berry aneurysm
Associations: any cause of HT predisposes to
berry aneurysms:
Essential hypertension
Adult polycystic kidney disease
Rupture of a berry aneurysm  blood into
subarachnoid space

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Berry aneurysm
Clinical findings:
Subarachnoid hemorrhage:
Sudden onset of severe occipital headache
“worst headache I ever had”.
Loss of consciousness.
Nuchal rigidity from irritation of meninges.
Complications:
Death from bleeding
Rebleed, neurological deficits.
Diagnosis:
CT scan as screen
Angiography confirms the diagnosis.

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Aortic dissection
Definition: blood from
the vessel lumen
enters an intimal tear
and dissects a path
along the length of
the vessel.
Usually involves the
wall of the
ascending aorta.

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Epidemiology
Aortic dissection occurs in two groups:
Most common group:
Men (mean age of 40-60 years) with
hypertension.
Young patients with a connective tissue
disorder:
Marfan syndrome, Ehlers Danlos syndrome.

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Pathology and Pathogenesis
The basis of dissecting aortic aneurysm is
weakening of aortic media.
Predisposing conditions:
Cystic medial degeneration (CMD):
is characterized by focal loss of elastic and
muscle fibers in tunica media.
Leads to cystic spaces filled with myxoid
material.
The cause is unknown.
Seen in different conditions ….

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Normal media
Cystic Medial
degeneration

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Pathology and Pathogenesis
Risk factors for CMD:
Increase in wall stress:
Hypertension, pregnancy
Defect in connective tissue:
Marfan Syndrome : defect in elastic
tissue (fibrillin)
Ehlers Danlos syndrome : defect in
collagen
Aging, Copper deficiency

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Cause of dissection
Intimal tear:
Due to HT or underlying structural weakness in
the media
Usually occurs within 10 cm of aortic valve
Column of blood dissects under arterial
pressure through the areas of weakness
Progresses proximally and or distally.

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Intimal tear

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Aortic
Dissection

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Aortic dissection
Types:
Type A :
involves ascending
aorta
Most common and
worst type
Type B:
Begins below the
subclavian artery
Classification of dissection
into types A and B.

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Aortic dissection
Clinical findings:
Acute onset of severe retrosternal pain radiating to
the back. Pain described as tearing.
AV regurgitation: due to aortic valve ring dilation; a
radiograph or echocardiogram shows widening of the
aortic valve root.
Loss of upper extremity pulse: compression of the
subclavian artery.
Rupture: usually into the pericardial sac (tamponade
most common cause of death), pleural cavity or
peritoneal cavity.
Diagnosis:
Increased aortic diameter on chest X ray.