Path Heart III (13)

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Author:
mse263
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263269
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Path Heart III (13)
Updated:
2014-02-21 23:10:12
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Pathology
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MBS Pathology
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Exam 2
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  1. Cardiomyopathy ('Heart Muscle Disease’)
    • intrinsic/principal diseases of the myocardium, as opposed to dysfunctions secondary to ischemia,
    • valvular, or hypertensive diseases
    • regardless of the cause (genetic, acquired, idiopathic), cardiac (ventricular) dysfunction is the key problem
    • can be broken down into 3 categories: dilated (90%), hypertrophic, or restrictive (less common)
  2. Primary Cardiomyopathies
    disease solely or predominantly confined to the heart muscle
  3. Secondary Cardiomyopathies
    heart is a part of generalized multi-organ disorder
  4. What is the most common form of cardiomyopathy?
    • Dilated Cardiomyopathy (DCM)
    • progressive hypertrophy & dilation of all 4 chambers
    • leads to systolic (contractile) failure
    • heart enlarged to 3-4x normal size & flabby w/ dilation of all chambers
    • while the cause is usually unknown (idiopathic), other conditions may be implicated (eg. infections, drugs, toxins, metabolic/neuromuscular abnormalities, etc.)
    • if idiopathic it's likely to be of genetic origin affecting genes that encode cytoskeletal/sarcomere/mitochondrial proteins
  5. What's the fundamental defect in dilated cardiomyopathy?
    • ineffective contraction
    • clinically manifests as slowly progressing congestive heart failure
    • symptoms: dyspnea, easily fatigable, poor exertional capacity
    • in end-stage DCM cardiac ejection fraction is typically less than 25% & cardiac transplantation is the ONLY definitive treatment
  6. Hypertrophic Cardiomyopathy
    • myocardial hypertrophy, abnormal diastolic filling, & in 1/3 of cases, intermittent ventricular outflow obstruction
    • MASSIVE myocardial hypertrophy, usually w/o ventricular dilation
    • the degree of hypertrophy is out of proportion to the hemodynamic load
    • concentric hypertrophy seen in 10% of case
    • can see characteristic "banana-shaped" ventricular lumen
  7. What causes Hypertrophic Cardiomyopathy?
    • missense point mutation in 1 of several genes encoding the sarcomeric proteins that form the
    • contractile apparatus of striated muscle (myosin, troponin, tropomyosin etc.)
    • may be related to defects in force generation that come about from altered sarcomere function
    • is usually autosomal dominant however a significant portion of cases develop as sporadic mutations w/o a family history
  8. How can the septum & left ventricular free wall be characterized in hypertrophic cardiomyopathy?
    in most cases it presents w/ asymmetrical septal hypertrophy, meaning there is a disproportionate thickening of the ventricular septum as compared with the free wall of the left ventricle
  9. Hypertrophic Cardiomyopathy Myofiber Characteristics
    • there is myofiber disarray w/ hypertrophic & branching myocytes running in various orientations instead of the usual parallel arrangements
    • there can also be interstitial & replacement fibrosis
  10. Restrictive Cardiomyopathy
    • a disease of the myocardium characterized by a primary decrease in ventricular compliance, resulting in impaired ventricular filling during diastole
    • myocardial stiffness limits diastolic filling but contractile functions remain NORMAL
    • ventricles are of normal or slightly enlarged size, cavities are NOT dilated, & the myocardium is firm
    • is the LEAST common category of cardiomyopathy in Western countries
    • condition invariably progresses to congestive heart failure & only 10% of patients survive for 10 years
  11. What are some of the causes of restrictive cardiomyopathy?
    • 1. interstitial infiltration of amyloid, metastatic
    • carcinoma, or sarcoid granulomas
    • 2. endomyocardial diseases
    • 3. storage diseases, including hemochromatosis
    • 4. markedly increased interstitial tissue
  12. Myocarditis
    • inflammation of the myocardium associated w/ myocyte necrosis & degeneration
    • the inflammation is the primary cause of the disease (as opposed to a response to myocardial injury like in ischemic heart disease)
    • is most common in CHILDREN between 1–10 yrs. old & can cause acute biventricular heart failure in previously individuals
    • severe myocarditis can cause arrhythmias & sudden cardiac death
  13. Causes of Myocarditis
    • 1. viral infections (most common) like coxsackieviruses; injury is caused by an immune response directed against virally infected myocardial cells
    • 2. nonviral infectious myocarditis like Chagas disease (caused by Trypanosoma cruzi); others = Trichinosis, Lyme disease (Borrelia burgdorferi)
    • 3. hypersensitivity & immunologically related diseases like Rheumatic fever, systemic lupus erythematosus, drug reaction (penicillin, sulfonamide etc.)
  14. Myocarditis Morphology
    • diffuse myocardial degeneration & necrosis w/ an inflammatory infiltrate
    • lymphocytic myocarditis shows infiltration of mononuclear inflammatory cells + associated myocyte injury
    • hypersensitivity myocarditis shows interstitial inflammatory infiltrate w/ eosinophils & mononuclear inflammatory cells
    • giant cell myocarditis shows mononuclear inflammatory infiltrate w/ lymphocytes, macrophages, extensive loss of muscle, & multinucleated giant cells
    • chagas disease shows myofibers distended w/ trypanosomes + surrounding inflammatory reaction & individual myofiber necrosis
  15. Myxomas
    • a tumor of primitive connective tissue that is the most common primary tumor of the heart in adults
    • it's a benign tumor often associated w/ clonal abnormalities of chromosomes 12 & 17 and is thought to arise from primitive multipotent mesenchymal cells
    • most cases show up in the L atrium as a glistening, gelatinous, polypoid mass, w/ a loose myxoid stroma (stellate or globular myxoma cells) embedded in a background of abundant proteoglycans
    • has characteristic vessel or gland-like structures
  16. What are the possible complications of a myxoma?
    while the benign tumor won't metastasize, it can EMBOLIZE & causes death in 1/3 of the patients (brain embolization)
  17. Pericardial Effusion
    • the accumulation of excessive fluid within the pericardial cavity, either as transudate or exudate
    • normal pericardial fluid is ~30-50 mL but effusion can reach several hundred mL
    • can cause cardiac Tamponade, a syndrome produced by the rapid accumulation of pericardial fluid that restricts the filling of the heart
  18. Hemopericardium
    • bleeding directly into the pericardial cavity
    • caused by penetrating cardiac trauma, rupture of a dissecting aneurysm of the aorta, infiltration of a vessel by tumor, rupture of cardiac wall, bleeding diathesis, etc.
  19. Cardiac Tamponade
    • pressure on the heart muscle which occurs when the pericardial space fills up w/ fluid faster than the pericardial sac can stretch
    • because the heart is filled with fluid blood can't properly be pumped through & filtered → builds up in the veins
    • during venous pressure rises progressively & linearly while arterial pressure may be normal or elevated & therefore is diagnostically unreliable
  20. Pericarditis
    inflammation of the pericardium (the fibrous sac surrounding the heart)
  21. In what situations is Fibrinous Pericarditis seen?
    • acute MI, post-infarction, uremia, chest radiation, rheumatic fever, SLE, & trauma
    • is a form of acute pericarditis; has effusion fluid rich in protein & the pericardium contains primarily mononuclear inflammatory cells
  22. What causes Purulent (Suppurative) Pericarditis?
    • invasion of the pericardial space by MICROBES
    • it causes an acute inflammatory reaction
    • organization & scarring is the usual outcome
    • it may lead to constrictive pericarditis
  23. Congenital Heart Defect
    • a defect in the structure of the heart & great vessels present at birth as a consequence of faulty embryonic development
    • can be caused by misplaced structures (eg. transposition of the great vessels) or as an arrest in the progression of a normal structure from an early stage to one that is more mature (eg. atrial septal defect)
    • most abnormalities arise during gestational weeks 3-8 when major cardiovascular structures develop
    • is seen in ~1% of live births
  24. What are the most common type of congenital cardiac malformations?
    • Left-to-Right Shunt
    • characterized by a "back-leak" of blood from the systemic to the pulmonary circulation
    • the pulmonary circulation carries both the blood that legitimately entered the R atrium & ventricle but also the blood entering through an ASD (atrial septal defect), VSD (ventricular septal defect), or PDA (patent ductus arteriosus)
    • blood volume & pressure in the pulmonary circulation become abnormally high
    • a significant shunt causes progressive damage to the pulmonary vasculature & gradual development of irreversible pulmonary hypertension
  25. Eisenmenger Syndrome
    when the pressure in the pulmonary circuit ultimately exceeds the systemic pressure causing a reversal of blood flow from the R side of the circulation to the L
  26. Right-to-Left Shunt
    • a cardiac shunt that allows blood to flow from the right to the left heart
    • CYANOSIS (low O2) presents at or near the time of birth b/c poorly oxygenated blood from the right side of the heart is introduced directly into the arterial circulation
    • most common: tetralogy of Fallot & transposition of the great vessels
    • can see clubbing of the finger tips, polycythemia (increase in the blood circulation of RBC), or paradoxical embolism
  27. Tetralogy of Fallot
    • a cyanotic Right-to-Left Shunt that's the most common cause of cyanotic congenital heart defects
    • 1. Ventral septal defect
    • 2. Obstruction to the right ventricular outflow tract (subpulmonic stenosis)
    • 3. Dextroposition of the aorta so that it overrides the ventricular septal defect
    • 4. Right ventricular hypertrophy
    • b/c of the pulmonary stenosis, blood is shunted through the ventricular septal defect into the aorta, resulting in arterial desaturation & cyanosis
    • if not repaired dyspnea on exertion will present & physical development will be slowed
    • there's also a risk for bacterial endocarditis & brain abscesses
  28. How can Tetralogy of Fallot be treated?
    total correct with surgery is possible
  29. Transposition of the Great Arteries (TGA)
    • a type of cyanotic congenital heart disease in which the aorta arises from the right ventricle & the pulmonary artery from the left ventricle!
    • the 2 circuits are separate & not compatible w/ life
    • almost all infants w/ TGA have an atrial septal defect &/or patent ductus arteriosis as compensatory mechanisms
    • the malformation can be corrected w/ surgery
  30. Aortic Coarctation
    • a local constriction that almost always occurs immediately below the origin of the left subclavian artery at the site of the ductus arteriosus
    • is 2-5x more frequent in males than females & is associated w/ bicuspid aortic valves in 2/3 of the cases
  31. How is blood pressure affected by Aortic Coarctation?
    • there is hypertension in the upper parts of the body but hypotension below the coarctation (aka in the lower extremities)
    • upper body hypertension results in left ventricular hypertrophy, dizziness, headaches, & nosebleeds
    • lower body hypotension leads to weakness, pallor, & coldness of lower extremities
    • radiographs of the chest show notching (erosion) of the inner surfaces of the ribs produced by increased pressure in markedly dilated intercostal arteries

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