Path Heart III (13)

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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

Card Set Information

Path Heart III (13)
2014-02-22 04:10:12
MBS Pathology
Exam 2
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