circulatory 2 Flashcards
Myocarditis/myocardial
degeneration
- Etiology
◦ Myocardial degeneration (toxic/nutritional)
◦ Myocardial toxin
◦ Nutritional
◦ Infectious Myocarditis
Myocardial toxins that can cause myocarditis
◦ Ionophores (monensin, lasolocid, salinomycin etc)
◦ Bacterial toxemia
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◦ Gossypol toxicity (cotton seeds)
◦ Cassia occidentalis– India, South America
◦ Phalaris spp. (canary grass) – all continents
nutritional causes of myocarditis
◦ Vitamin E / Se deficiency
◦ Excessive dietary molybdenum or sulfates
Infectious Myocarditis - bacterial and viral causes
Bacterial
◦ Histophilus somni (formerly Hemophilus somnus)
◦ Truperella pyogenes (formerly Arcanobacterium, Actinomyces, Corynebacterium)
◦ Clostridial myocarditis - lambs
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Viral
◦ Foot & Mouth Disease
◦ Bluetongue in sheep
Myocarditis/Myocardial Degeneration
- Clinical signs: acute, chronic
Peracute /acute
◦ Sudden death
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Chronic
◦ Heart failure (subacute to chronic cases)
◦ Arrhythmias
◦ Vitamin E / selenium deficiency
◦ Cases tend to die when exercised (unaccustomed)
Myocarditis/Myocardial Degeneration
- Clinical pathology
◦ Depend on the underlying cause (toxic vs septic)
◦ Isoenzymes (LDH/CK) ??
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◦ Cardiac Troponin I (structural protein) - cTpnI
◦ Indicative of active myocardial damage
◦ More sensitive, less cross-reactivity with skeletal muscle
◦ Myocardial necrosis had a cTnI concentration > or = 1.04 ng/mL.
◦ Experimental monensin toxicity cows.
Myocarditis/Myocardial Degeneration
- Treatment
◦ Remove/treat underlying cause > Treat deficiencies
◦ Rest, minimize stress
◦ Anti-arrhythmics (usually not feasible)
◦ Anti-inflammatory medication for myocarditis > Cortiosteroids, NSAIDs (flunixin, meloxicam, ketoprofen)
Myocarditis/Myocardial Degeneration
- PM lesions
◦ Gross PM often unrewarding
◦ Histology: degeneration, fibrosis, cellular infiltration
> Vit E/Selenium
> May see “characteristic” streaked pallor
◦ Myocarditis lesions may have abscesses
> But may be patchy on histology and may be missed
Pericardial Disease
Most common in ruminants? less common?
Septic pericarditis
◦ Cows > Traumatic reticulitis/pericarditis
◦ Sheep, goats, calves > Component of septicemia
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◦ Lymphoma (uncommon)
Hardware-associated pericarditis
- pathogenesis
◦ Foreign body penetrates reticulum
◦ Distance to pericardium 1-1.5 cm
◦ Infectious pericarditis
◦ Mixed infection usually
◦ Intestinal organisms, May be gas producing
Pericardial Disease
Clinical signs
◦ Muffled heart sounds > Fluid in pericardial sac interferes with sound transmission
◦ Weak and rapid peripheral pulse
◦ Decreased cardiac filling → decreased stroke volume→ decreased cardiac output
◦ Venous engorgement > Right heart cannot fill (thin walled), Compromised venous return
◦ Percussion (enlarged cardiac area)
◦ Jugular veins are often extremely distended
◦ Elbows abducted
◦ Pericarditis is often painful (mostly early in disease)
◦ May have a fever
◦ Friction rub sound (like an intense murmur)
◦ Hardware (TRP): history of anorexia, decreased milk production, poor rumen
motility, positive withers pinch
◦ May have splashing sound on auscultation
Pericardial Disease
Friction rubs - what are these?
- what do they sound like?
- when can we no longer hear them?
◦ Fibrin layers on pericardium & epicardium rubbing together
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Differentiation from murmurs
◦ Vary beat to beat
◦ In timing (i.e. cannot fix it to heart sounds: S1, S2)
◦ In character
◦ In intensity
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◦ May be present at one examination, then absent, then reappear
◦ Disappear once effusion accumulates
Pericardial Disease
Diagnosis
Clinical signs:
◦ Clinical diagnostic triad: muffled heart sounds, weak rapid pulse, venous engorgement
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Ultrasound:
◦ Anechoic to flocculent fluid with fibrin strands and gas
◦ Thickness of pericardium
◦ Rectal probe may be useful (5-7 cm penetration depth)
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ECG - Electrical Alternans
◦ Alternating large and small QRS complexes
◦ Change in ventricular axis due to presence of fluid
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◦ Pericardiocentesis (best U/S guidance)
Pericardial Disease
Treatment
◦ Systemic antibiotics alone not often enough
◦ Drainage of pericardial sac if causing enough signs
◦ Local instillation of antibiotics?
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Surgery
◦ Rumenotomy: removal of foreign body through reticulum may work if pericardial involvement not
extensive.
◦ Once pericarditis well established often difficult to treat.
◦ Pericardectomy (usually a heroic effort)
what is constrictive pericarditis?
◦ Fibrin formation organizes and forms fibrous tissue which restricts filling, may be a sequela or pericarditis
Pericardial Disease
Post mortem examination
- what can we see? with hardware disease?
◦ Pericardium full of fluid
◦ Appearance of fluid varies with underlying disease
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Hardware:
◦ Thickened pericardium
◦ Purulent, fibrinous fluid
◦ Communication with reticulum may be evident
◦ Foreign body may be present
◦ May have been withdrawn by magnet
◦ May have migrated further
High Mountain Disease
- what is this?
- pathogenesis?
- what can make it worse?
Congestive heart failure occurring in cattle moved to and living at altitude
◦ Low atmospheric O2 causes alveolar hypoxia → reflex pulmonary arterial
vasoconstriction → pulmonary hypertension → right heart failure
Cor Pulmonale
(right heart failure secondary to pulmonary hypertension)
- Worsened by ingestion of locoweed: Oxytropis and Astragalus spp.
High Mountain Disease
- who is susceptible?
- altitude?
Animals introduced to high altitude rather than
indigenous.
◦ Sheep, goats relatively resistant
◦ Holsteins appear predisposed
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Elevation above see level?
◦ Variable depending on intercurrent disease, distance over
which animal must forage, nutrition.
◦ But generally, over 1800m above sea level.
High Mountain Disease
- why are cows sensitive?
- compensation?
- additional effects?
- adaptation?
- Chronic low oxygen causes pulmonary arterioles to constrict > increased afterload
- Cows sensitive due to highly developed muscular media even in small pulmonary arterioles
- Compensatory mechanisms such as hyperventilation, polycythemia, increased cardiac output DO NOT develop
- Hypoxemia also causes myocardial damage
- Adaptation can occur if introduction to altitude is gradual
High Mountain Disease - ‘Like’ conditions
Can have similar “syndrome” without altitude
◦ Severe pulmonary parasitosis
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Severe pneumonia resulting in severe hypoxia
◦ Response to hypoxia can be the same and cor pulmonale can develop
◦ Can be exacerbated if with diseases such as diarrhea (eg. septic calves)
◦ Acidosis potentiates vasoconstriction
High Mountain Disease
Post-mortem
◦ Congestive heart failure
◦ Concentric right ventricular hypertrophy!
◦ May need to weigh chambers to diagnose: Right ventricular free wall >30% heart weight
High Mountain Disease
Management / Treatment, prognosis?
◦ Remove from altitude
◦ Minimize stress
◦ Diuretics may be of some benefit
◦ Usually die 3-4 weeks from onset of edema
◦ Slaughter/euthanasia
Cardiomyopathy - what does this mean?
◦ Non-specific term
◦ Subacute or chronic
◦ Primary or intrinsic disorders of the myocardium.
◦ Reflect primary myocardial, biochemical and/or metabolic deficiencies
◦ Intrinsic myocardial disease (no other cardiac tissues affected)
Bovine hereditary cardiomyopathy
- what is this?
- origins?
◦ Group of progressive degenerative disorders of the myocardium causing congestive heart failure and
subsequently death.
◦ Canadian Holstein sire Montwick Red Apple Sovereign (MRAS) > common ancestor
