PATHOLOGY OF Aneurysms Aneurysms are congenital or acquired dilations of blood vessels or the heart True aneurysm False aneurysm

2. • Aneurysms are congenital or
acquired dilations of blood
vessels or the heart
True aneurysm
False aneurysm

3. • True aneurysms involve all 3 layers of
artery or attenuated wall of heart
Atherosclerotic aneurysms
Congenital vascular aneurysm
Ventricular aneurysm
• False aneurysm results when a wall defect
leads to formation of extravascular
hematoma
Ventricular ruptures
Leak at junction of vascular grafts

5. classification
• Saccular aneurysms
discrete outpouchings ranging from 5-20
cm diameter , often with a contained thrombus
• Fusiform aneurysms
circumferential dilatations upto 20 cm
diameter, commonly involve aortic arch, abd
aorta, iliac arteries

6. PATHOGENESIS
Aneurysms occur when structure or function of connective
tissue is compromised by any of the following factors:
• Inadequate / abnormal connective tissue
synthesis
• Excessive connective tissue degradation
• Loss of smooth muscle cells or change in
smooth muscle cell synthetic phenotype

7. INADEQUATE / ABNORMAL
CONNECTIVE TISSUE
SYNTHESIS
• TGF beta regulates smooth muscle cell
proliferation and matrix synthesis
• Thus mutations in TGF beta receptors or
downstream signaling pathways result in
defective elastin and collagen synthesis.
Aneurysm in affected rupture even when small

8. • In Marfan syndrome, defective
synthesis of the scaffolding protein Fibrillin
leads to abnormal sequestration of TGF beta
in the aortic wall , with subsequent dilation
due to dysregulated signalling and
progressive loss of elastic tissue
• Defective type III collagen synthesis with
aneurysm formation is a hallmark of type IV
Ehlers Danlos syndrome

9. Excessive connective tissue
degradation
• Increased MMP expression as by macrophages
in atherosclerotic plaque can contribute to
aneurysm development by degrading arterial
ECM in the arterial wall
• Decreased TIMP expression can also cause
ECM degradation

10. Loss of smooth muscle
• Atherosclerotic thickening of intima can
cause ischemia of inner media
• Systemic hypertension can cause luminal
narrowing of aortic vasa vasorum leading to
ischemia of outer media
• Ischemia results in smooth muscle cell loss
and aortic degenerative changes –Cystic
medial degeneration (fibrosis, inadequate
ECM synthesis , accumulation of increasing
amounts of amorphosproteoglycans)

12. causes
• ATHEROSCLEROSIS
• HYPERTENSION
• Trauma, vasculitis , congenital defects ,
infections(mycotic aneurysm)
• Tertiary syphilis a rare cause

13. Abdominal aortic aneurysm
• Atherosclerotic aneurysm most common in
abdominal aorta
• More in men and > 50
• Cause : excess ECM degradation in major
• Atherosclerotic plaques compromise diffusion
medial degeneration & necrosis
• Familial predisposition

14. MORPHOLOGY
• Between renal artery and aortic bifurcation
• Extensive atherosclerosis present
• Aneurysm sac contains mural thrombus
• Inflammatory AAA
• Mycotic AAA

16. CONSEQUENCES
• Obstruction of vessel arising off the aorta
• Embolism
• An abdominal mass
• Impingement on adjacent structures
• Rupture

17. Thoracic aortic aneurysm
• Associated with hypertension and Marfan
• Mutation in TGF beta signaling pathway
SIGNS AND SYMPTOM
• Respiratory and feeding difficulties
• Persistent cough
• Pain due to erosion of bone
• Cardiac disease
• Aortic rupture

18. Aortic dissection
• Old term Dissecting aneurysm
• Occurs when blood splays apart the laminar planes of
media to form a blood filled channel within the aortic
wall
• Men 40-60 with antecedent hypertension
Younger patients with connective tissue abnormalities
• Can be iatrogenic

19. PATHOGENESIS
• Hypertension major risk factor
• Medial hypertrophy of vasa vasorum
• Marfan syndrome , Ehlers Danlos syndrome
type IV, defects in copper metabolism.
• Rarely disruption of vasa vasorum can gives
rise to an intramural hematoma without an
intimal tear.

20. MORPHOLOGY
• Intimal tear found in ascending aorta
• Extend retrograde towards heart or distally as far
as iliac and femoral
• Lies between middle and outer thirds of media
• Cardiac tamponade..
• Double barreled aorta– chronic dissections
• Preexisting histologically detectable lesion is
Cystic medial degeneration

22. CLINICAL CONSEQUENCES
• Proximal lesions : Type A dissections
(DeBakey type I or II)
• Distal lesions : Type B dissections
(DeBakey type III)

24. • Symptoms : sudden onset excruciating
,stabbing , or tearing pain
• Cause of death : rupture of dissection into
pericardial, pleural or peritoneal cavity
• Cardiac tamponade , aortic insufficiency,
MI
• Extension to large arteries
• Compression of spinal arteries –
Transverse myelitis

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