Cardiovascular Pathology II Flashcards
What is a cardiomyopathy?
Generalised term for diseases of the heart muscle where the walls of the heart chambers have become thickened or stiff
What is primary mycardial disease?
- Typically idiopathic (infectious)
- The disease is intrinsic to the myocardial fibre
What is secondary myocardial disease?
- Usually the result of a known external insult
- Potentially metabolic cause (toxic, infectious neoplastic)
- The disease is not intrinsic to the myocardial fibre
What are the five types of primary cardiomyopathy types?
- Dilated
- Hypertrophic
- Restrictive
- Arrhythmogenic right ventricular
- unclassified
What predisposes a dilated primary cardiomyopathy?
- Large breed dosg e.g doberman pinschers, portugese water dogs, irish wolfhounds
What effect does a dilated primary cardiomyopathy have on the cardiac cycle?
- Causes systolic dilation- lowered inotropy with increased ventricular ESV
What is the gross pathology of a dilated primary cardiomyopathy?
- Dilation of atria and ventricles, increased annulus circumference
- Eccentric hypertrophy of ventricles
What breeds are most predisposed to a hypertrophic primary cardiomyopathy?
- Most common in cats
- Maine Coos/ Ragdolls, any cat with cardiac myosin binding protein C
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What effect does Hypertrophic primary cardiomyopathy have on the cardiac cycle?
- Diastolic dysfunction- impaired lusitropy (ventriclar compliance and filling)
What is a saddle thrombus?
- Thromboembolus at the aortic trifurcation
What is a saddle thrombus the sequelae for?
- hypertrophic cardiacmyopathy
How does a thromboembolus in the aortic trifurcation occur?
Thrombus forms in the left atrium
thrombus dislodges and passes through the aorta
lodges in the aortic trifurcation
causes distal limb ischemia
What predisposes a restrictive primary cardiomyopathy?
- It’s relatively infrequent
- potential sequelae of endomyocarditis
What effect does a restrictive primary cardiomyopathy have on the cardiac cycle?
- Diastolic dysfunction
- restricted ventricular filling
due to increased stiffness of the ventricular myocardium
What is the gross pathology of a restrictive primary cardiomyopathy?
- Endomyocardial fibrosis
- excessive moderator bands
- Atria typically dilate with normal ventricular size
What are the genetic/ breed predispositions of an Arrhythmogenic right ventricular cardiomyopathy?
- Middle aged boxers, rarely cats
- striatin gene mutation
What effect does an Arrhythmogenic right ventricular cardiomyopathy have on the cardiac cycle?
- Ventricular arrythmia, typically left bundle branch block morphology
How does hyperthyroidism in cats lead to thyrotoxic heart disease?
- Excessive circulating thyroid hormones
- increased production of myocardial proteins -> hypertrophy, enhanced contractility
- increased calcium recycling. upregulation of receptors, enhanced depolarisation
What is Brain-Heart Syndrome?
- Multifocal myocardial necrosis associated with neurological disease of diverse origin
When does multifocal myocardial necrosis occur?
- occurs in dogs with gastric torsion, acute necrotising pancreatitis, septic peritonitis
What is the nutritional cause of myocardial necrosis?
Vitamin E/ Selenium deficiency
How does vitamin E deficiciency cause myocardial necrosis?
- Decreased free-radical scavenging
- free-radical damage to myocyte cell membranes
- myocyte necrosis and mineralisation
- death via ventricular arrythmia
What does vitamin E dediciency cause in lambs, calves, foals and camelids
White lamb disease
What does vitamin E deficiency cause in Piglets?
Mulberry heart disease
What essential amino acid in cats can cause myocardial necrosis?
Taurine
cause taurine-deficiency myocardial failure
What stain do we use for taurine-deficiency myocardial failure?
Masson’s Trichrome stain;
What plants can cause myocardial necrosis?
Cardiac glycosides e.g foxglove, milkweed, lily of the valley
What pharmaceuticals can cause myocardial necrosis?
- Digoxin
- Ionophores
- Chemotherapeutics
What beetle may cause myocardial necrosis?
- Blister beetles
- Cantharidin is the toxic principle, it also causes ulcerative gastroenteritis
What is the mechanism of action for Digoxin?
Reversibly inhibits Na+/K+ ATPase pump → ↑ intracellular
Na+ and Ca2+ → ↑ inotropy (contractility) but can also
lead to cardiomyocyte necrosis
increased intracellular calcium increases contractility
What is the mechanism of action of Ionophore toxins?
- forms reversible complexes with cations and facilitates ionic transport across biological membranes
What are the 5 different types of myocarditis?
- Necrotising
- suppurative
- Pyogranulomatous
- Lymphoplasmacytic
- Eosinophillic
What problems in dogs predispose to multifocal myocardial necrosis?
- gastric torsion
- acute necrotisisng pancreatitis
- septic peritonitis
What is the myocardial response to injury?
- Extensive or minor fibrosis depedning on the extent of the injury?
