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SYSTEMIC PATHOLOGY - 1 > 4 – Myocardium > Flashcards

4 – Myocardium Flashcards

1
Q

Myocardium and lost myofibrils

A
  • NO capacity to replace
  • Normal repair is impossible
  • *different compared to skeletal muscle
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2
Q

Myocardial degeneration: microscopically

A
  • Loss of striations
  • Hypereosinophilia
  • Swelling
  • Dissolution of sarcoplasm and myofibrils
  • Nuclear condensation
  • Fragmented
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3
Q

Myocardial calcification or mineralization

A
  • In many degenerative diseases, calcium is SEQUESTERED in the sarcoplasm and organelles
  • Large amounts of calcium=detrimental effects
  • Microscopically (H&E): dark-blue granules in sarcoplasm
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4
Q

What happens to affected myocardial fibers following necrosis?

A
  • Under cardiomyolysis
  • Macrophages (and neutrophils) start cleaning up myofiber debris
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5
Q

Myocardial necrosis and repair

A
  • Necrotic tissue is replaced by connective tissue=eventually results in cardiac fibrosis (SCAR)
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6
Q

Myocardial necrosis: grossly

A
  • Softer, pale discoloration
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7
Q

Myocardial fibrosis: grossly

A
  • Firmer, white
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8
Q

Ischemic Myocardial Necrosis (HEART ATTACK)

A
  • Very common in humans
  • RARE in animals
  • Usually a result of vasculitis (needs to be extensive)
  • Due to plaques
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9
Q

Examples of some things that can cause Toxic Myocardial Necrosis

A
  • Cardiac glycoside containing plants: Oleander
  • Cantharidin (due to ingestion of blister beetles)
  • Other toxic plans (Karwinskia humboldtiana)
  • Doxorubicin
  • Ionophores (monensin)
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10
Q

White muscle disease (nutritional myopathy)

A
  • Major economic loss worldwide
  • Often manifests as sudden death
  • Affects farm animals (NOT dogs and cats)
  • Mostly in rapidly growing animals
  • Affect fetuses and cause abortion
  • Exacerbated by EXERCISE or STRESS (produce more radicals)
  • Responds well to treatment in early stages
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11
Q

Which muscle types does white muscle disease affect?

A
  • Sometimes only skeletal muscle or cardiac muscle
  • Sometimes both
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12
Q

Basic pathogenesis of white muscle disease

A
  • Deficiencies of Vitamin E and Selenium=reduced availability of free radical scavengers
  • Free radicals overwhelm scavengers, and excessive free radicals cause PEROXIDATAION OF CELL MEMBRANES (cell degeneration)
  • Degenerated cells are UNABLE to pump out calcium=calcium accumulates (mineralization)
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13
Q

White muscle disease gross lesions

A
  • White discolouration of L. ventricle (calves) and R. ventricle (lambs)
  • Submit tissues of both sides of heart for histopathology
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14
Q

White muscle disease histopathology

A
  • Areas of mineralization=black
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15
Q

Vitamin E and Selenium deficiency in pigs

A
  • Does NOT cause white muscle disease
  • Liver necrosis
  • Still affects the heart (MULBERRY HEART DISEASE)
    o Extensive areas of hemorrhage and necrosis
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16
Q

Neurogenic myocardial necrosis (brain-heart syndrome)

A
  • Multifocal subendocardial areas of pale discoloration=myocardial necrosis and fibrosis
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17
Q

Myocarditis

A
  • Rarely occurs alone, typically part of SYSTEMIC disease
  • Classified based on exudate
18
Q

Myocarditis classification based on exudate

A
  • Suppurative (neutrophils)
  • Lymphocytic
  • Eosinophilic
  • Hemorrhagic
  • Granulomatous
19
Q

Canine parvovirus

A
  • Causes hemorrhagic enteritis
  • Can cause myocarditis in young puppies (canine parvovirus myocarditis)
    o Intranuclear inclusion body (histology)
20
Q

Histophilius somni

A
  • Past: associated with Infectious Thrombotic Meningoencephalitis (ITME), pneumonia, arthritis, reproductive problems
  • Recent: cause of bovine myocarditis (particuallary in feed lots)
21
Q

Histophilius somni myocarditis

A
  • Locally extensive areas of infarction (secondary to vasculitis and thrombosis)
  • Suppurative myocarditis
  • Lesions primarily involve papillary muscles and L. ventricular free walls
22
Q

Staphylococcus aureus mycarditis in lambs and kids

A
  • Multifocal suppurative myocarditis affecting L + R ventricles
  • Bacteria and neutrophils: histology
23
Q

Myocardial abscess in cow (Trueperella pyogenes)

A
  • Infection and inflammation in lung, liver, joints: blood dissemination leads to heart abscesses or endocarditis
  • Large abscesses in myocardium
24
Q

Parasitic myocarditis (Cysticercosis)

A
  • Fluid filled cysts containing white larvae
  • Indirect cycle
  • Could be due to protozoa (Trypanosoma cruzi) or nematodes (Trichnella spiralis)
25
Q

Cysticercosis sp.

A
  • Taenia saginata: C. bovis
  • Taenia ovis: C. ovis
  • Taenia solium: C. cellulose
26
Q

Chagas disease (American Trypanosomiasis

A
  • Trypanosoma cruzi
  • Kissing bug (Triatoma spp.)
  • Lymphoplasmacytic myocarditis
27
Q

Animal cardiomyopathies: morphologically classified in 3 main types

A
  • Hypertrophic cardiomyopathy (HCM)
  • Dilated or congestive cardiomyopathy (DCM)
  • Restrictive cardiomyopathy
28
Q

Primary cardiomyopathies

A
  • Changes in cardiac wall THICKNESS
  • Causes electrical disturbances
  • Often results in sudden death
  • Most common in dogs and cats
  • Sporadically reported in cattle, pigs and rats
  • Etiology is uncertain
  • Some instances: genetic predisposition
  • Typically progressive cardiac disease
29
Q

Hypertrophic cardiomyopathy

A
  • Most common in cats (middle aged males)
  • Decreased ventricular filling -> decreased compliance -> DIASTOLIC DYSFUNCTION
  • Both ventricles, but especially noticeable in left
  • Increased heart weight as a percent of body weight
30
Q

Hypertrophic cardiomyopathy resembles CONCENTRIC HYPERTROPHY but w/o an underlying cause such as

A
  • Aortic or pulmonic stenosis
  • Hypertension
31
Q

Hypertrophic cardiomyopathy: 1/3 have

A
  • Aortic ‘saddle’ thromboemboli
  • Less often have atrial thrombi
32
Q

Hypertrophic cardiomyopathy: genetics

A
  • Myosin binding protein C3 gene mutation
  • Ex. Main Coon, Ragdoll
33
Q

Hypertrophic cardiomyopathy: histopathology

A
  • Fiber disarray (crisscrossing)
34
Q

Dilated (congestive) cardiomyopathy

A
  • Most common in dogs (cats, hamsters)
  • Progressive cardiac dilation and contractile (systolic) dysfunctions
    o Decreased contractile force and increased EDV
35
Q

Dilated (congestive) cardiomyopathy: causal predispositions

A
  • Taurine deficiency in cats and foxes
  • Familial tendencies in large dog breeds
  • Hereditary form in Holstein cattle
36
Q

Dilated cardiomyopathy: ‘grossly’

A
  • Increased heart weight
  • Dilated chambers
  • Cardiomegaly
  • Thin walls
  • Attenuated papillary muscles
37
Q

Arrhythmogenic right ventricular cardiomyopathy (variant of DCM)

A
  • Boxer dogs
  • Autosomal dominant trait=causes an ION CHANNEL DEFECT
  • Diffusely pale dilated right ventricle
    o Also pale due infiltration of adipose tissue
38
Q

Arrhythmogenic right ventricular cardiomyopathy: histology

A
  • R. ventricular myocyte degeneration
  • Necrosis
  • Loss of replacement by adipose or fibroadipose tissue
39
Q

Restrictive cardiomyopathy (‘L ventricular endocardial fibrosis’)

A
  • Most common in cats
  • Impaired ventricular filling and DIASTOLIC DYSFUNCTION
  • Usually preceded by endomyocarditis
  • Diffuse endocardial thickening (sometimes mural thrombosis)
  • *excessive moderator bands (septomarginal trabeculae)
40
Q

Other forms of restrictive cardiomyopathy

A
  • Excessive moderator bands (septomarginal trabeculae)
  • Congenital endocardial fibroelastosis (Burmese cats)
41
Q

Primary endocardial fibroelastosis

A
  • Hereditary disease in humans and Burmese cats
  • Both ventricles
  • Lots of collagen and elastin fibers
  • No underlying cardiac disease
  • Uncertain pathogenesis
  • *don’t usually reach adult life

SYSTEMIC PATHOLOGY - 1 (24 decks)

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