Aneurysms & a Brief Discussion on Embolism Ali Al Khader, M.D. Faculty of Medicine Al-Balqa’ Applied University Email: ali.alkhader@bau.edu.jo

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”)

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

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

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

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

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

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

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

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

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%

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

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

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%

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

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

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.)

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

Thank You