1. Aneurysms & a Brief Discussion on Embolism
Ali Al Khader, M.D.
Faculty of Medicine
Al-Balqa’ Applied University

2. Aneurysms, overview
= congenital or acquired dilations of blood vessels or the heart
“True” aneurysms
-involve all three layers of the artery (intima, media, and adventitia) or the
attenuated wall of the heart
…e.g., atherosclerotic and congenital vascular aneurysms, as well as ventricular
aneurysms resulting from transmural myocardial infarctions
false aneurysm (pseudoaneurysm)
= extravascular hematoma that communicates with the intravascular space
(“pulsating hematoma”)

3. Aneurysms, classification according to shape
aortic arch, the abdominal aorta, or the iliac arteries

4. Aneurysms, pathogenesis
Inadequate or abnormal connective tissue synthesis
…mutations in TGF-β receptors or downstream signaling pathways
…often rupture, even when small
…Marfan syndrome
…deficiency of??
…type IV Ehlers-Danlos syndrome
…defective type III collagen synthesis

5. Aneurysms, Pathogenesis, cont’d
The 2 most important causes
Excessive connective tissue degradation
…increased MMPs…such as by macrophages in atherosclerotic plaque
…decreased TIMPs
…inflammation increased MMPs and decreases TIMPs
Loss of smooth muscle cells or change in the smooth muscle cell synthetic phenotype
…atherosclerosis…increases distance of diffusion to inner media
…HTN…decreases blood flow from vasa vasorum to outer media
…these may cause loss of SM cells, fibrosis, inadequate ECM, accumulation of
amorphous proteoglycans, and loss of elasticity in aorta
…these changes = cystic medial degeneration…may be also seen in Marfan & Scurvy

6. Aneurysms, pathogenesis, cont’d
HTN…ascending aorta more
Atherosclerosis…abdominal aorta
Other causes:
-Trauma
-Vasculitis
-Congenital defects
-Infections… = mycotic aneurysms

7. Mycotic aneurysms Mycotic aneurysms result from :
embolization of a septic embolus, usually as a complication of infective
endocarditis
(2) extension of an adjacent suppurative process
(3) direct infection of an arterial wall by circulating organisms…like
Salmonella gastroenteritis
Tertiary syphilis is a rare cause of aortic aneurysms
…predilection for vasa vasorum of ascending thoracic
aorta…obliterative endarteritis
…the aneurysm can occasionally involve aortic valve annulus

8. Abdominal aortic aneurysm (AAA)
Atherosclerosis
…can also affect: common iliac, aortic arch, descending thoracic aorta
…inflammation and impaired diffusion
…men
…smokers
…after 50 years
…not only atherosclerosis
Marfan syndrome
Smoking-related emphysema is associated…dysregulated ECM degradation

9. Abdominal aortic aneurysm, morphology
Typically: between the renal arteries and the aortic bifurcation
…can be saccular or fusiform
…up to 15 cm in diameter and 25 cm in length
…In the vast majority: underlying extensive atherosclerosis is present
…usually with mural thrombus
Not infrequently, AAAs are accompanied by smaller iliac artery aneurysms

10. Clinical consequences of AAA
Obstruction of a vessel branching off the aorta…renal, iliac…etc.
Embolism
Pressure…on ureter, vertebra…etc.
Palpable pulsating abdominal mass
Rupture into peritoneal/retroperitoneal cavity…often fatal

11. AAA rupture Size…if <=4cm in diameter: almost never
4-5: 1% per year
5-6: 11% per year
>6cm: 25% per year
Managed surgically
…if elective: mortality 5%
…if emergency: 50%

12. Thoracic aortic aneurysm
Most commonly HTN, Marfan, and TGF-beta defects
Clinically:
(1) Encroachment on mediastinal structures (e.g., respiratory or feeding difficulties
due to airway or esophageal compression, respectively)
(2) Persistent cough from irritation of the recurrent laryngeal nerves
(3) Pain caused by erosion of bone (i.e., ribs and vertebral bodies)
Cardiac disease due to valvular insufficiency or narrowing of the coronary ostia
Aortic rupture
(5) Patients with syphilitic aneurysms may die of heart failure induced by
aortic valvular incompetence

13. Embolism Thromboembolism…systemic or venous Gas embolism
Amniotic fluid embolism
Fat embolism

14. Fat embolism
Long bone fractures and soft tissue crush injuries…<10% are clinically significant
Vigorous cardiopulmonary resuscitation…mostly asymptomatic
If symptomatic:
-pulmonary insufficiency
-neurologic symptoms
-anemia
-thrombocytopenia
-diffuse petechial rash
Fatal in 10%

15. Fat embolism, mechanisms
Both mechanical obstruction and biochemical injury
Direct obstruction and platelet aggregation
Fatty acid release…endothelial injury
Granulocyte recruitment and the injury they cause

16. Amniotic fluid embolism
Uncommon
Mortality rate: 80%... the most common cause of maternal death in the developed world
85% of survivors suffer some form of permanent neurologic deficit
Sudden severe dyspnea, cyanosis, and hypotensive shock, followed by seizures and coma

17. Amniotic fluid embolism, cont’d
also may find lanugo hair, fat or mucin
If survived initial crisis:
-pulmonary edema
-DIC (50%)…thrombogenic
substances from amniotic fluid
Robbins basic pathology 9th edition…(Courtesy of Dr. Beth Schwartz, Baltimore, Maryland.)

18. Air embolism Examples: -bypass surgery…coronary artery
-neurosurgery…cerebral artery
-venous such as in obstetric surgery or chest trauma…pulmonary
-decompression sickness
The bends, chokes, and caisson disease

19. Thank You