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Aneurysms and DissectionAneurysms and Dissection

CSBR.Prasad, MD.,

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Aneurysm - Definition:

Localized abnormal dilation of a blood vessel or the heart

It may be congenital or acquired

Common sites

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Aneurysm of left ventricle

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Aneurysm of the left ventricle

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The gross morphology of aneurysms reveals several different pathological features:

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Types: True aneurysms:

Dilation of intact arterial wall or thinned ventricular wall of the heart Atherosclerotic, syphilitic, and congenital

vascular aneurysms, ventricular aneurysms following MI

False aneurysms / Pseudoaneurysms: A defect in the vascular wall leading to an

extravascular hematoma that freely communicates with the intravascular space (“pulsating hematoma”) ventricular rupture after MI that is contained by

a pericardial adhesion

True & False aneurysms

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Cardiac aneurysm

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Complication: Both true and false aneurysms can

rupture, often with catastrophic consequences

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Morphological types: Saccular aneurysms:

Spherical outpouchings involving only a portion of the vessel wall vary from 5 to 20 cm in diameter and often contain thrombus

Fusiform aneurysms: Circumferential dilations of a long

vascular segment vary in diameter (up to 20 cm) and can involve extensive portions

These types are not specific for any disease or clinical manifestations

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Aneurysms:

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Pathogenesis of Aneurysms: Aneurysms can occur when the

structure or function of the connective tissue within the vascular wall is compromised Inherited defects in connective tissues Acquired connective tissue defects

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Pathogenesis of Aneurysms: The intrinsic quality of the vascular wall

connective tissue is poor The balance of collagen degradation and

synthesis is altered by inflammation and associated proteases

The vascular wall is weakened through loss of smooth muscle cells or the synthesis of noncollagenous or nonelastic extracellular matrix

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Pathogenesis of Aneurysms: The intrinsic quality of the vascular wall

connective tissue is poor Marfan syndrome:

Defective protein fibrillin leads to aberrant TGF-ß activity and weakening of elastic tissue

Loeys-Dietz syndrome: Mutations in TGF-ß receptors lead to defective

synthesis of elastin and collagens I and III Ehlers-Danlos syndrome:

Defective type III collagen synthesis Vitamin C deficiency:

Altered collagen cross-linking

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Pathogenesis of Aneurysms: The intrinsic quality of the vascular wall

connective tissue is poor The balance of collagen degradation and

synthesis is altered by inflammation and associated proteases

The vascular wall is weakened through loss of smooth muscle cells or the synthesis of noncollagenous or nonelastic extracellular matrix

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Pathogenesis of Aneurysms: The balance of collagen degradation and

synthesis is altered by inflammation and associated proteases Increased matrix metalloprotease (MMP)

expression AS, Vasculitis

Decreased expression of tissue inhibitors of metalloproteases (TIMPs) Inflammatory lesions – AS Local Inflammation – production of IL-4, IL-10

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Pathogenesis of Aneurysms: The intrinsic quality of the vascular wall

connective tissue is poor The balance of collagen degradation and

synthesis is altered by inflammation and associated proteases

The vascular wall is weakened through loss of smooth muscle cells or the synthesis of noncollagenous or nonelastic extracellular matrix

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Pathogenesis of Aneurysms: The vascular wall is weakened

through loss of smooth muscle cells or the synthesis of noncollagenous or nonelastic extracellular matrix Ischemia of the inner media

[Histo: Cystic medial degeneration] AS, Systemic hypertension Tertiary syphilis

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Cystic medial degeneration

Alcian Blue-PAS

Marfan’s syndromeMarfan’s syndrome

NormalNormal

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Important causes of aortic aneurysmsThe two most important causes of aortic

aneurysms: Atherosclerosis [AAA] Hypertension [Thoracic aortic aneurysm] Others:

Trauma Vasculitis Congenital defects & Infections

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Mycotic aneurysms: Mycotic aneurysms can originate: Septic embolus [infective endocarditis] Extension of an adjacent suppurative

process Circulating organisms directly infecting

the arterial wall

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Abdominal Aortic Aneurysm: AAA Atherosclerosis Men >50yrs Smokers

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Abdominal Aortic Aneurysm: MORPHOLOGY Usual position: below the renal

arteries and above the bifurcation of the aorta

Saccular or fusiform 15 cm in diameter, and up to 25

cm in length Usually contains a bland, laminated,

mural thrombus

Abdominal Aortic AneurysmUsual position:

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Variants of AAA:Three AAA variants merit special

mention because of their unusual features

Inflammatory AAA IgG4-related disease Mycotic AAA

Inflammatory AAA 5% to 10% of all AAA Typically seen in younger patients Back pain and Elevated inflammatory markers – CRP Histology:

Characterized by abundant lymphoplasmacytic inflammation with many macrophages, giant cells

Dense periaortic scarring that can extend into the anterior retroperitoneum

Localized immune response to the abdominal aortic wall

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IgG4-related disease AAA

High plasma levels of IgG4 Fibrosis Infiltrated by IgG4-expressing plasma cells Other organ systems may also be involved

Salivary, pancreas, biliary system

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Mycotic AAA Infected by the lodging of circulating

microorganisms in the wall

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Clinical Features of AAA Incidental finding – ‘pulsatile abdominal tumor’ Rupture into the peritoneal cavity or

retroperitoneal tissues with massive, potentially fatal hemorrhage

Obstruction of a vessel branching off from the aorta, resulting in ischemic injury to the supplied tissue

Embolism from atheroma or mural thrombus Impingement on an adjacent structure eg:

Compression of a ureter or erosion of vertebrae

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The risk of rupture - AAA Is directly related to the size

NIL - <4 cm 1% per year between 4 and 5 cm 11% per year between 5 and 6 cm 25% per year larger than 6 cm

Most aneurysms expand at a rate of 0.2 to 0.3 cm/year, but 20% expand more rapidly

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Aneurysms 5 cm or larger are managed aggressively

Thoracic Aortic Aneurysm - TAA Most commonly associated with

hypertension Other causes:

Marfan syndrome Loeys-Dietz syndrome

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Thoracic Aortic Aneurysm – TAAPresentation: Respiratory difficulties due to encroachment on

the lungs and airways Difficulty in swallowing due to compression of

the esophagus Persistent cough due to compression of the

recurrent laryngeal nerves Pain caused by erosion of bone Cardiac disease – IHD - as the aortic aneurysm

leads to AR Rupture

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Abdominal Aortic Aneurysm

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Thoracic Aortic Aneurysm – TAAPresentation:

Most patients with syphilitic aneurysms die of heart failure secondary to aortic valvular

incompetence

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Thoracic Aortic Aneurysm – TAA

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Thoracic Aortic Aneurysm – TAA

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Thoracic Aortic Aneurysm – TAA

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Thoracic Aortic Aneurysm – TAATree bark appearance - Syphilis

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Aortic Dissection Occurs when blood separates the

laminar planes of the media to form a blood-filled channel within the aortic wall

Occurs principally in two groups of patients: Men, 40 to 60 years with antecedent

hypertension (>90%) and Younger adults with abnormalities of

connective tissue affecting the aorta

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Aortic Dissection

Other causes: Arterial cannulization Pregnancy

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Aortic DissectionPathogenesis: Hypertension – Cystic medial degeneration Marfan syndrome Ehlers-Danlos syndrome Defects in copper metabolism

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Aortic Dissection - MORPHOLOGY

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Most frequent finding is cystic medial degeneration usually initiates with an intimal tear Spontaneous dissection:

Within 10 cm of the aortic valve Tears are typically transverse with sharp, jagged edges up to 1

to 5 cm in length Dissection can extend retrograde toward the heart as well as

distally Tear: Between the middle and outer thirds Rupture through the adventitia causing massive

hemorrhage Cardic tamponade “double-barreled aorta”

Aortic Dissection - MORPHOLOGY

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Aortic dissection

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Classification:

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Clinical Features: Proximal dissections are more serious and

dangerous (types I and II of the DeBakey)

PAIN: sudden onset of excruciating pain, usually beginning in the anterior chest, radiating to the back between the scapulae, and moving downward as the dissection progresses

Cardiac tamponade Aortic insufficiency Ischemic consequences

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Out come: In type A dissections: Mortality is 70% Most type B dissections can be

managed conservatively -75% survival rate

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E N D

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