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Diseases of the Myocardium
Winter 2009
Lisa Miller
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Idiopathic or Inherited Primary Myocardial Disease
Primary Myocardial DiseasesPrimary Cardiomyopathy
• Definition– Acute, subacute, or chronic generalized
disease of heart muscle. An intrinsic disease of the myocardial fiber.
• Arrhythmogenic cardiomyopathy (ACM)– Clinical term arrhythmia with normal
ejection fraction.– May precede pathological changes.
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Idiopathic Primary Myocardial Disease (IPMD)
Primary Cardiomyopathy
• Pathological Terms – Primary cardiomyopathy is diagnosed with gross
or histopathological changes in the myocardium without apparent cause.
• Cause/Etiology– Inherited – Obscure or not known.
• Viruses, Immune mediated disease, Toxins– All have been implicated
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Primary CardiomyopathyGeneralities
• Classification based on cardiac wall thickness– Pathologically Speaking
• Hypertrophic (HCM)• Congestive or Dilative (DCM)
– Taurine deficiency in cats, foxes and dogs• Taurine Deficiency Myocardial Failure (TDMF)
– L-carnitine deficiency • Dilative cardiomyopathy in dogs (Boxer)• Used in treatment protocols
• Restrictive Cardiomyopathy• Other
– Arrhythmogenic Right Ventricular Cardiomyopathy– Excessive Moderator Bands
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Primary CardiomyopathySpecies Affected
• Dogs– Great Dane -DCM– Newfoundland –DCM– English Cocker– Irish Wolfhound -DCM– German shepherd - HCM– St Bernard -DCM– Boxer (ACM) – English bull dogs (ACM) – Doberman Pinschers (2 forms)– American Cocker Spaniel– Bull Mastiff – Dalmatians– Boston terriers (HCM)– Springer Spaniels – Atrial standstill– Portuguese water Dogs– Golden Retriever
• Males and Middle Aged• 0.5% admission to VTH
• Cats– Maine Coon Cat– Rag Doll– British and American Shorthair– Rex, Persians, DSH
• Cattle – Holstein, Simmental, Herefords, etc
• Birds– Turkeys
• Round Heart Disease
– Chickens– Ducklings
• Syrian Hamsters – Inherited MD• Human beings
– Autosomal dominant HCM
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Hypertrophic Cardiomyopathy• Gross
– Resembles concentric hypertrophy
– Increase in Heart weight
• Species– Cat
• 10-20% present with posterior paresis
• Most common form of heart disease in the cat
• Breeds– Maine Coon(AD)– Rag Doll– British & American
Short Hair (AD)– Rex
– Dog, rat, pigThrombus in distal aorta
Heart from cat with HCOM
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Hypertrophic CardiomyopathyHCOM
• Histo– Large, hypertrophied
fibers – irregular size
– Myofibre disarray
– Variable numbers of inflammatory cells and fibrosis
• Physiology Diastolic Dysfunction– ventricular filling
– compliance
– Sometimes only see hypertrophy of septum
Feline HCOM Myofibre disarray
Feline HCOM Myocardial disarray and fibrosis
Feline normal heart
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Hypertrophic Cardiomyopathy
Outflow obstruction
-Acquired Subaortic Stenosis
Caused by HCOM
Endomyocardial fibrosis
Mitral valve irritant?
Feline HCOM Myocardial fibrosis
Masson’s trichrome stain
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Congestive CardiomyopathyDilative, Dilated, Dilatative, DCM
• Species– Dog– Cat, hamster, turkey,
pig, cow, fox
• Gross– Resembles eccentric
hypertrophy• Dilated chamber, thin
walls, valves may be open due to cardiac muscle dilation
– Wt
12-year-old doberman, m/c with congestive cardiomyopathy
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Congestive Cardiomyopathy
Physiology:– Progressive cardiac
dilation and contractile dysfunction
– contractile force
– End Diastolic Volume
• Histo– Thin, wavy,
myofibres
– Variable fibrosisFeline Congestive Cardiomyopathy Myocardium H&E
Normal myocardium
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Congestive Cardiomyopathy
Gross Appearance:
-ventricular chambers increased in size
-thin walls
-attenuated papillary muscles
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Restrictive Cardiomyopathy
• Less common and probably not a “true cardiomyopathy”
• ventricular compliance– Due to restriction of
ventricular filling
• Cats – Endocardial
fibroelastosis• Burmese
– Inflammation• Fibrosis• Endomyocarditis
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Other Primary Cardiomyopathies
• Arrhythmogenic Right Ventricular Cardiomyopathy (Fibroadipose Dysplasia)– Adipose cells and fibroblasts infiltrate
and replace normal right ventricular myocardium• Boxers
http://www.bcm.edu/web/pediatrics/images/ARVD_Heart_Cap.gif
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Other Primary Cardiomyopathies
• Excessive Moderator Bands– Reported in Adult Cats– May be a Congenital Anomalie
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CardiomyopathiesHypertrophic Congestive Restrictive Other
wt/body wt
+/- wt/body wt
+/-
MyofibersIrregular and
enlarged –
myofibre disarray
MyofibersThin and wavy
Variable amounts of CT
MyofibersHypertrophied myofibres
May not be a true cardiomyopathy
MyofibersReplaced with fibroblasts and adipose tissue
Catsmiddle aged males
10-20% posterior paralysis
Persians, Maine coon
Dog, Rat, Pig
Cattle
Dog
Cat
Hamster
Turkey
Pig, Cattle
Cat
Human beings
Dogs ? subaorticstenosis?
Dog – Boxer
Human Beings
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Secondary Myocardial DiseaseSecondary Cardiomyopathy
• Definition: Disease of cardiac muscle resulting from metabolic, toxic, infectious, or neoplastic disease
• Not– NOT " INTRINSIC DISEASE of myofibres”
– NOT PRIMARY CARDIOMYOPATHY
– NOT Inflammatory Disease
See page 585 – Box 10-3 - Pathologic Basis of Veterinary Disease
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CatecholamineToxicity
• “Brain-Heart Syndrome”
• Causes: – Chemical agents
– Brain/spinal cord trauma
– Functional tumor of adrenal medulla
• Lesions: – Multifocal myocardial
necrosis (LV,P)
• Species– Dogs
– Many other species
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Hyperthyroidism
• Causes– Cats with functional
thyroid masses
• Lesions– Concentric hypertrophy
– LV
• Reversible
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Conduction Disorders• Unexpected death in Doberman pinscher dogs
– Focal degeneration of the bundle of His• Syncope in pug dogs
– Degeneration of the bundle of His• Intermittent sinus arrest in deaf dalmation dogs
– Sinus Node lesions• Sinoatrial syncope (sick sinus syndrome)
– Miniature Schnauzers, West Highland White terriers– Dachshunds, Springer Spaniels
• Arrhythmias – dogs and horses• Atrial fibrillation• Heart block
– associated with myocardial lesions
Few pathological evaluations or reports
on conduction disorders…
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Nutritional Deficiencies
Vitamin E/Selenium deficiency
Synonyms
“White Muscle Disease”
“Mulberry Heart Disease”
Incidence
Areas deficient in VitE/Se
Many species
Etiology
Low Vit E/Se, low Sulphur
High [polyunsaturated fats]
Exposure to pro-oxidant compounds
Intake of selenium antagonists
silver salts, Hg, Cu, Co, Cd, Zn, Sn
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Vitamin E/Selenium deficiency
Pig – Mulberry Heart
Lamb – Mineralization and necrosis of muscle
Calf-Nutritional cardiomyopathy
Foal White muscle Disease
Pathogenesis
Vit E = antioxidant works with glutathione peroxidase to prevent oxidation of membranes
Lesions
Pale areas of necrosis and mineralization lambs and calves,
pigs have widespread haemorrhages (microangiopathy
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Taurine DeficiencyTaurine Deficiency Myocardial Failure
Essential Amino Acid for Cats
Modulates Tissue Calcium
Dilated left and right ventricles with thin myocardial –indistinguishable from DCM.
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Poisonous plants & Animals • Avocados Leaves • Cardiac Glycosides
– Oleander– Foxglove– Lily of the Valley– Dogbane– Toad Poisoning “Bufo toxicosis”
• No lesions - sudden death• Inhibit sodium and potassium ATPase pumps
http://www.ivis.org/advances/Beasley/cpt14b/chapter_frm.asp?LA=1oleander
foxglove
Lily of the Valley
dogbane
Bufo Toad
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Cardiotoxins
• Myocardial depressants
• Direct Injury to Myofibre– Electrical Defibrillation
– Hemorrhagic Shock
• Hypersensitivity
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Chemotherapeutic Agentsproducing myocardial disease
• Doxorubicin (Adriamycin)
– Dose related cardiotoxicity – CHF
– Sarcoplasmic vacuolization and necrosis
• Monensin
– Horses, cattle, sheep, pigs, dogs & poultry
– Myocardial necrosis
Adria Cells
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Infectious AgentsMyocarditis
• Viral– Encephalomyocarditis
virus of swine • Picornavirus –
cardiovirus
• Elephants, primates, swine
• Rodents are carriers
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Infectious Agents
Viral Myocarditis• Parvovirus in the dog
– Lesions in pups <10 weeks of age
• West Nile Virus
• Pseudorabies
• Canine distemper– in very young puppies
• Bluetongue in sheep
• Coxsackie virus– Man and mouse
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Viral Agents - Myocarditis• Foot and Mouth Disease
– Tiger Heart
• Avian Encephalomyelitis• Newcastle Disease• Eastern & Western Encephalitis• Human Viruses
– Influenza– HIV– Cytomegalovirus
• NOTE: – Viral agents may produce acute
necrosis with little inflammatory response.
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Bacterial AgentsMyocarditis
• Direct extension of pericarditis – (eg. "hardware disease")
• Direct extension of endocarditis – (eg. Bacterial infection of
mitral valves)
• Septicemias
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Bacterial Agents- Myocarditis
• Any septicemia– Borrelia burgdorferi – Lyme Disease– Histophilus somni
• feedlot cattle– Clostridium chauvei
• Blackleg – Listeria monocytogenes
• especially in sheep
– Actinobacillus equuli &Streptococcus equi
• horses
– A. pyogenes• Cattle and sheep
– Staph aureus• Sheep and goats
– Corynebacterium kutscheri• Rodents
– Psudomonas aeruginosa– Tyzzer’s Disease– Necrobacillosis Bovine – Heart Histo Blackleg –
Clostridial myocarditis
Lamb – Staphylococcal myocarditis, multifocal
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Parasites - Myocarditis
• Neosporum caninum– Fatal fetal myocarditis and
encephalitis– Abortion or weak calves
• Toxoplasma gondii– Occurs in any species in contact
with cat faeces– Public health hazard– Fatal fetal myocarditis can occur
if infected during pregnancy
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Parasites - Myocarditis
• Trypanosoma cruzi (Chaga's disease)– Reported in dogs in
Texas and Louisiana
– Fatal infection in young dogs (6-8 months)
– “Assassin" bug inoculates organism while feeding
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Causes of Myocardial Dysfunction - Summary
Idiopathic and Inherited Cardiomyopathies – Dilative, Hypertrophic, Restrictive,
Arrhythmogenic
Endocrine/Metabolic Hyperthyroidism
Catecholamine toxicity
Hypokalemia
Nutritional Vitamin E/Selenium
Taurine
Copper
Toxic Agents Gossypol
Poisonous Plants – oleander, foxglove, others
Ionophotes – monensin, ,salinomycin, maduramicin
Doxorubicin/daunorubicin
Iron, Thallium, toads and blister beetle
Furazolidone, fluroacetate, and more…
Infectious agents Viral
Bacterial
Parasitic
Genetic Cardiomyopathies
Porcine Stress Syndrome
Storage Diseases
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Miscellaneous Myocardial Disease
• Porcine stress syndrome
• Sudden death in cattle
• Canine gastric/dilation – volvulus
• Acute necrotizing pancreatitis
• Sepsis - peritonitis