Congenital Anomalies of Blood Vessels PDF

Congenital anomalies of Blood vessels: 1) Berry aneurysm: - Thin walled arterial outpouching affects cerebral vessels of circle of willis. - The affected vessel is attenuated (weak). - Complication: Spontaneous rupture causing fatal intracerebral hemorrhage. 2) Arterio-venous fistula: - Abnormal...

Congenital anomalies of Blood vessels: 1) Berry aneurysm: - Thin walled arterial outpouching affects cerebral vessels of circle of willis. - The affected vessel is attenuated (weak). - Complication: Spontaneous rupture causing fatal intracerebral hemorrhage. 2) Arterio-venous fistula: - Abnormal connection between artery and vein without intervening capillary bed. - Can be congenital or acquired (due to rupture of aneurysm or penetrating wound) - Complication: Large AV fistula can cause high output heart failure. 3) Fibromuscular dysplasia: - Focal irregular thickening of the wall of medium sized and large muscular arteries - Occur due to combination of medial and intimal hyperplasia and fibrosis leading to luminal stenosis - Most frequently affect young woman. - Complication: Renovascular hypertension and rupture of the vessels. HYPERTENSION (HTN) Definition: Sustained elevation of blood pressure above 140/90 mmHg. - Affects ~ 25% of population. Classification of hypertension: Accordingto severity: Benign (95%) versus malignant (5%) According to cause: Primary (essential) (95%) versus secondary (5%) According to side of circulation: Systolic vs diastolic 1. Essential (idiopathic) in 95% of cases: Results from an interaction between genetic and environmental factors include; stress, obesity, cigarette smoking, physical inactivity and heavy consumption of salt. 2. Secondary due to some underlying cause : a. Renal (glomerulonephritis, renal artery stenosis and polycystic kidney diseases). b. Endocrine (adrenocortical, pheochromocytoma, hyper and hypothyroidism). c. Cardiovascular (coarctation of aorta and polyarteritis nodosa). d. Neurogenic (psychogenic, increase intracranial pressure).  Malignant hypertension: - 5% (also known as accelerated HTN) - Usually superimposed on preexisting benign hypertension - Characterized by rapidly rising blood pressure that, if untreated, leads to death within 1 to 2 years - Systolic pressures > 200 mm Hg or Diastolic pressures > 120 mm Hg - Most common complication: Renal failure and retinal hemorrhages Morphologic changes: HTN is associated with arteri olo sclerosis (small arterial disease) Two forms of small blood vessel disease are hypertension related: 1- Hyaline arteriolosclerosis 2- Hyperplastic arteriolosclerosis 1- Hyaline arteriolosclerosis - Ass. with benign hypertension - homogeneous pink hyaline thickening of arteriolar Walls lead to luminal narrowing (ischemia) - leakage of plasma components across injured endothelial cells into vessel walls - increased ECM production by smooth muscle cells in response to chronic hemodynamic stress. Complications of Hyaline arteriolosclerosis: - Most significant in kidneys➔ nephrosclerosis (glomerular scarring > Hypertensive nephropathy). Other causes of hyaline arteriolosclerosis: 1- elderly patients (normo-tensive) 2- diabetis mellitus. 2- Hyperplastic arteriolosclerosis - Occur with severe (malignant) hypertension - Characterized by onionskin" concentric laminated thickening of arteriolar walls or Fibrinoid vessel wall necrosis (necrotizing arteriolitis) - Reduplicated basement membrane > Narrowing of the lumen CNS: Stroke (hemorrhagic and ischemic) Blood vessels: Arteriolosclerosis, Atheroscleosis Aneurysms and dissection Heart: CHD, left ventricular hypertrophy & heart failure (hypertensive heart disease) Kidney: Renal failure Retina: Retinal hemorrhages  ARTERIOSCLEROSIS Arteriosclerosis ="hardening of the arteries" arterial wall thickening and loss of elasticity. Three patterns are recognized, with different clinical and pathologic consequences:  1-Arteriolosclerosis - Affects small arteries and arterioles - Associated with hypertension and/or diabetes mellitus  2- Mönckeberg medial calcific sclerosis Calcific deposits in muscular arteries Typically in persons > age 50 Radiographically visible (x-rays, etc…) Palpable vessels Do not encroach on vessel lumen and are usually not clinically significant  3) Atherosclerosis Greek word "gruel" ,"hardening," Most frequent and clinically important pattern of arteriosclerosis Characterized by intimal lesions =atheromas ( atherosclerotic plaques) Atheromatous plaque = raised lesion with a core of lipid (cholesterol and cholesterol esters) covered by a firm, white fibrous cap ATHEROSCLEROSIS- PATHOGENESIS - Not fully understood., mostly result of inflammatory process in response to endothelial injury. COMPONENTS OF WELL DEVELOPED ATHEROMA ATHEROSCLEROSIS- PATHOGENESIS  Progression of atherosclerosis 1- Fatty streaks: The earliest lesion, may appaear befor puberty They composed of lipid filled foamy macrophages. Appears Grossly as non raised yellowish streaks 2- Atheromatous plaque: Raised lesion showing Intracellular lipid accumulation. Core of extracellular lipid 3- Fibroatheroma: Single lipid core with fibrotic and calcific layers 4- Complicated lesion: Thick fat core Thin fat core Thin fibrous cap Thick fibrous cap More inflammation less inflammation ANEURYSM Localized permanent abnormal dilation of artery or heart Types: Normal 1-True aneurysm All three layers of arterial wall or heart e.g. Atherosclerotic, syphilitic, congenital aneurysms, ventricular aneurysms following transmural MI.  2- False aneurysm: (pseudo-aneurysm). A breach in vascular wall leading to hematoma communicating with intravascular space ("pulsating hematoma") Examples: - Ventricular rupture after MI contained by pericardial adhesion - A leak at the junction of a vascular graft with a natural artery.  Aneurysms are classified according to macroscopic shape into: 1- Saccular aneurysms - Spherical outpouchings -involving only a portion of vessel wall - May contain thrombi 2-Fusiform aneurysms diffuse, circumferential dilation of a long vascular segment they vary in diameter and length and can involve extensive portions of artery The two most important causes are: 1- Atherosclerosis : - most common cause →intimal plaques compress underlying media →compromise nutrient and waste diffusion into arterial wall →media degeneration and necrosis → thinning and weakening of media →dilation of vessel 2- Cystic medial degeneration of arterial media causes include: trauma; congenital defects (e.g., berry aneurysms); hereditary defects in structural components (Marfan); infections (mycotic aneurysms); vasculitis.  Atherosclerotic aneurysms occur most frequently in: abdominal aorta > common iliac > arch >descending parts of thoracic aorta. m/c in men rarely < age 50 Atherosclerosis is a major cause of AAA other contributors include: 1- Hereditary defects in structural components of the aorta: (e.g., Marfan disease by defective fibrillin production affects elastic tissue synthesis) 2- An altered balance of collagen degradation and synthesis mediated by local inflammatory infiltrates and the destructive proteolytic enzymes (e.g. vasculitis).  Usually below renal arteries and above bifurcation of aorta  can be saccular or fusiform  may be as large as 15 cm in diameter, and as long as 25 cm  Microscopically: atherosclerosis; thinning of media  frequently contains a laminated mural thrombus Infection of a major artery that weakens its wall is called a mycotic aneurysm can originate from: (1) embolization of a septic thrombus (infective endocarditis) (2) extension of adjacent suppurative process (3) circulating organisms infecting arterial wall  Extravasation of blood that enters the wall of artery through an intimal tear, as a hematoma dissecting between its layers.  often but not always aneurysmal  Both true and false aneurysms as well as dissections can rupture, often with catastrophic consequences  A catastrophic event whereby blood dissects apart the media to form a blood-filled channel within aortic wall  Complications are : Massive hemorrhage cardiac tamponade (hemorrhage into the pericardial sac)  1- Hypertension is the major risk factor  pressure-related mechanical injury and/or ischemic injury.  2- inherited or acquired connective tissue disorders causing abnormal vascular ECM  (e.g., Marfan syndrome, Ehlers-Danlos syndrome, vitamin C deficiency, copper metabolic defects)  cardiovascular manifestations  Sharp chest/ back pain  Weak pulses in downstream arteries  Cardiac tamponade  Blood pressure difference between Rt & Lt arms  Hypotension  shock 1 - Type A dissections:  More common  More dangerous  Proximal to take off of major aortic branches  involve either ascending aorta only or both ascending and descending aorta ( types I and II of the DeBakey classification ) 2- Type B dissections: - Distal to take off of major aortic branches - Does not involve ascending aorta - usually beginning distal to subclavian artery - Also called DeBakey type III  The most common among inherited or acquired connective tissue disorders assosiated with aortic dissection  Autosomal dominant disease of fibrillin, an ECM scaffolding protein required for normal elastic tissue synthesis  Manifestations include:  skeletal abnormalities (elongated axial bones)  ocular findings (lens subluxation)