USMLE Step 1 Review - Vascular system, heart, pericardium - 1

Dr.AhmadDr.Ahmad مدير عام
Abnormal lipid metabolism
[FONT=&quot]Fredrickson's hyperlipidemias[/FONT]
Type I (familial hyperchylomicronemia; increased chylomicrons [deficient lipoprotein lipase]; supranate), type IIa (familial hypercholesterolemia; increased LDL [deficient LDL receptors, defective apo B-100], CH; atherosclerosis, tendon xanthomas, xanthelasmas), type IIb (familial combined hyperlipidemia; increased LDL, VLDL, CH, and TG; atherosclerosis); type III (familial dysbetalipoproteinemia; increased chylomicron, IDL remnants [mutations of apo E]; atherosclerosis), type IV (familial hypertriglyceridemia; increased VLDL due to decreased catabolism; most common genetic hyperlipidemia; infranate), type V (mixed hypertriglyceridemia; type I and type IV; defects in apo CII gene; diabetic ketoacidosis and alcoholism are common factors; turbid supranate and infranate; eruptive xanthomas)
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Absence of apo B --> malabsorption (very low triglyceride and cholesterol levels), CNS disease (ataxia, retinitis pigmentosa, nystagmus, sensory abnormalities), and acanthocytosis

Diseases of the arterial system
Hardening of the arteries; subclassified as atherosclerosis (formation of atheromas), Monckeberg's medial calcification, and arteriolosclerosis (hyaline and hyperplastic types)
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Most common disease afflicting the aorta; more common in males, age related; primarily involves intima of elastic and muscular arteries; fatty streak (early lesion) and fibrous plaque (advanced lesion); proposed mechanisms: thrombogenic (mural thrombus incorporated into an atheroma), monoclonal (proliferation of smooth muscle cells), reaction to injury theory (most popular; endothelial cell injury [smoking, LDL] --> monocytes and lymphocytes adhere to injury --> emigrate into vessel wall --> release of cytokines --> smooth muscle proliferation, chemotaxis [macrophages, lymphocytes, smooth muscle cells imbibe oxidized LDL produced by free radicals from injured epithelial cells and macrophages --> become foam cells] --> fatty streaks enlarge and disrupt endothelial surface --> platelets adhere to damaged endothelium and release PDGF [contributes to smooth muscle proliferation] --> smooth muscle cells synthesize collagen, elastin, proteoglycans --> fibrous plaques) (cont.)
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atherosclerosis involves abdominal aorta > coronary arteries > popliteal artery > descending thoracic > internal carotid > circle of Willis
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[FONT=&quot]Complications of atherosclerosis[/FONT]
Plaque ulcerates --> ruptures --> thrombus formation (lines of Zahn --> alternating layers of platelets and fibrin [pale], and layers of blood [dark]); thromboembolism of plaque material to distant sites may result in infarction; may weaken vessel wall resulting in aneurysm; primary pathogenesis of ischemic heart disease; associated with peripheral vascular disease (may lead to claudication and amputation of extremity); may result in CNS disease; primary cause of renovascular hypertension; may produce gastrointestinal disease (mesenteric angina, bowel infarction, ischemic strictures [colon])
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[FONT=&quot]Monckeberg's medial calcification[/FONT]
Age-related, clinically insignificant degenerative disease that commonly involves muscular arteries (e.g., femoral arteries, uterine arteries)
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Either hyperplastic (proliferative) or hyalinized; hyperplastic type characterized by smooth muscle proliferation in an "onion-skin" pattern with narrowing of the lumen (e.g., renal vessels in malignant hypertension and progressive systemic sclerosis); hyaline type associated with arterioles that have a glassy, pink appearance on H and E staining ("small-vessel disease" of diabetes mellitus [nonenzymatic glycosylation of basement membrane of vessels renders them permeable to proteins] and hypertension [increased pressure imposed on arteriolar walls drives protein into vessels])
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Localized dilatation of an artery that results from weakening by atherosclerosis (most common), inflammation, a congenital abnormality (e.g., Ehlers-Danlos syndrome), trauma, or hypertension; natural history is to enlarge and rupture; may be fusiform (spindle shaped), saccular (round), or dissecting
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[FONT=&quot]Aortic aneurysms[/FONT]
Different etiologies depending on location; in ascending aorta, most commonly secondary to dissecting aortic aneurysm that has extended proximally (tertiary syphilis is no longer the most common cause); in distal aorta (thoracic and abdominal) and in the extremities, most commonly secondary to atherosclerosis
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[FONT=&quot]Abdominal aortic aneurysm[/FONT]
Most common aneurysm; most often in men over age 55; due to weakening of wall by atherosclerosis owing to lack of vasa vasorum below renal artery orifices; majority asymptomatic; if symptomatic, pulsatile mass with mid-abdominal to lower back pain, abdominal bruit; rupture is most common complication (most rupture into left retroperitoneum) --> severe back pain, pulsatile mass, hypotension; abdominal ultrasound is gold standard
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[FONT=&quot]Berry aneurysm[/FONT]
Most commonly located at bifurcations of cerebral vessels (anterior communicating artery with anterior cerebral artery); most are congenital and are associated with vessels that lack an internal elastic membrane and muscle wall; association with adult polycystic kidney disease (10-15%) and coarctation of the aorta
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[FONT=&quot]Mycotic aneurysms[/FONT]
Secondary to weakening of vessel wall by an infectious process (e.g., septic embolism, infective endocarditis, fungal vasculitis [Aspergillus, Mucor, Candida])
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[FONT=&quot]Syphilitic aneurysm[/FONT]
Syphilitic aneurysm involving arch of aorta is second most common manifestation of tertiary syphilis; Treponema pallidum produces endarteritis obliterans (vasculitis; numerous plasma cells) of vasa vasorum in ascending and transverse portions of aortic arch --> ischemia in outer adventitial and outer medial tissue of aorta --> weakening of wall --> aneurysm formation and aortic regurgitation from stretching of aortic valve ring; linear calcifications often seen in ascending aorta by CXR; can be associated with respiratory distress, cough; death usually occurs from rupture or heart failure
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[FONT=&quot]Dissecting aortic aneurysm[/FONT]
Most common catastrophic disorder of the aorta; elastic tissue fragmentation (95%) with or without mucoid degeneration (cystic medial necrosis) in middle and outer part of media --> weakens vessel wall; predisposing causes: Marfan's syndrome (fibrillin defect), Ehlers-Danlos syndrome (defect in collagen), pregnancy (increased plasma volume), copper deficiency (cofactor in lysyl oxidase), coarctation of aorta (wall stress), trauma; hypertension is single most important factor for initiating dissection (shearing force to intimal surface --> intimal tear --> entry of column of blood); entry of blood into pericardial sac is most common cause of death; type A (most common; worst type; involves ascending aorta), type B (begin below subclavian artery); acute onset of severe chest pain (tearing), radiates to back; increased aortic diameter on CXR; retrograde arteriography is gold standard
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[FONT=&quot]AV fistulas[/FONT]
Abnormal communications between arteries and veins; either congenital or acquired (most commonly due to penetrating knife injury); large AV fistulas reduce systemic resistance and bypass microcirculation --> increase venous return to heart --> high-output cardiac failure

Disorders involving the venous system
Thrombosis of a vein without inflammation (90% in legs); predisposing factors: damage to vessel endothelium (e.g., inflammation, varicose veins), stasis of blood flow (e.g., bed rest), and hypercoagulability (e.g., oral contraceptive use); swelling, pain, edema distal to thrombosis, varicosities, ulceration
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[FONT=&quot]Deep venous thrombosis[/FONT]
Deep venous insufficiency: thrombosis --> obstruction of deep saphenous vein --> increased venous pressure --> increased blood flow to veins around ankles that communicate with superficial system --> veins in ankle rupture --> stasis dermatitis (swelling, hemorrhage --> hemosiderin deposition, ulcers) and secondary varicosities in superficial saphenous system; swelling of the calf and positive Homan sign (dorsiflexion of foot) and Mose sign (compression of calf) strongly suggests deep saphenous vein thrombophlebitis; complications: thromboembolism, thrombophlebitis, varicose veins; doppler ultrasonography (best test); x-ray venography is gold standard
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Pain and tenderness along the course of a superficial vein; usually occurs postoperatively in patients over 40; most commonly secondary to varicose veins but may be associated with phlebothrombosis (common), intravenous catheters, polycythemia, IV drug abuse, or a neighboring infection; involved vein is palpable cord with pain, induration, heat, and erythema along skin surface
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[FONT=&quot]Migratory thrombophlebitis[/FONT]
Venous thrombi disappear at one site and reappear at another; may be a paraneoplastic sign of underlying pancreatic cancer (Trousseau's sign)
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[FONT=&quot]Thoracic outlet syndrome[/FONT]
Abnormal compression of neurovascular compartment in the neck due to a cervical rib, spastic scalenus anterior muscle, or positional change in the neck and arms; diagnosis confirmed by arteriogram
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[FONT=&quot]Superior vena cava syndrome[/FONT]
Secondary to extrinsic compression of the SVC from a primary lung cancer (smoking) and less commonly a malignant lymphoma --> puffiness and blue to purple discoloration of the face, arms, and shoulders and CNS findings of dizziness, convulsions, and visual disturbances (congested retinal veins), JVD; diagnosis confirmed by venography

Disorders involving the lymphatic system
[FONT=&quot]Acute lymphangitis[/FONT]
Inflammation of the lymphatics ("red streak") most commonly secondary to Streptococcus pyogenes
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[FONT=&quot]Chylous effusions[/FONT]
Collections of lymphatic fluid in a body cavity secondary to a malignant lymphoma or trauma
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Abnormal interstitial collection of lymphatic fluid caused by congenital disease or blockage of lymphatics; primary type presents at birth (congenital lymphedema) or is delayed and first presents in adolescence (lymphedema precox); Milroy disease (hereditary lymphedema caused by faulty development of lymphatics); Turner's syndrome (lymphedema of hands and feet); secondary causes: lymphatic obstruction by tumor (e.g., peau d'orange appearance in inflammatory carcinoma of the breast), radiation (postradical mastectomy with axillary dissection; most common cause in US), infestation by filarial organisms (Wuchereria bancrofti), lymphogranuloma venereum (chlamydial disease --> localized lymphedema in vulva or scrotum); nonpitting edema, does not resolve with overnight elevation; complication of long-standing lymphedema is lymphangiosarcoma


  • تم تعديل 2009/04/28
    [align=left]Thank Youuuuuuuuuuuuuuuuuuuuuu
  • تم تعديل 2009/04/28
    مشكور دكتور احمد ويحمد رايتك ,ومتل ما بيقولو اول الغيث قطره وعم ننتظر تمطر علينا ببقيه المجموعه يلي وعدتنا فيها ,رجاء خاص لو سمحت لا تكثر من الالوان زاغت عيوننا,ما عدت ميزت العنوان من الموضوع والف الف شكر
  • Dr.AhmadDr.Ahmad مدير عام
    تم تعديل 2009/04/28
    تكرمي دكتورة و ان شاء الله السيل كلو جاية عالطريق ...........
    أهلا فيك لوفر
  • تم تعديل 2009/04/28
    شكرا لكم موضوع طبي بحت يعطيك العافية