Canine Cardiomyopathies and Myocarditis Flashcards
What are the three main canine cardiomyopathies?
Dilated Cardiomyopathy
Arrhythmogenic Right Ventricular Cardiomyopathy
Atrial Standstill
What type of cardiomyopathy is common in Dobermans and other large breed dogs?
DCM
Which breed inherits ventricular arrhythmias (rare)?
German Shepherd
Which breeds are predisposed to juvenile DCM?
Portugese Water Dog
Great Dane
What are three infectious causes of myocarditis?
Chagas disease
Parvovirus
Lyme disease
What are the two most common nutritional deficiences leading to cardiomyopathy in dogs?
Taurine
Carnitine
What drug can cause toxic cardiomyopathy in dogs?
Doxyrubricin
What four metabolic states can commonly cause cardiomyopathy and systolic dysfunction?
Muscular dystropy
Hypothyroidism
Hyperthyroidism
Tachycardia
What is dilated cardiomyopathy (DCM)?
Primary heart muscle disease characterized by cardiac dilatation and systolic dysfunction of one or both ventricles
What are the five hypothesized causes of canine cardiomyopathy?
Familial/genetic Immune-mediated Viral Metabolic Nutritional
T/F: Canine cardiomyopathy is better understood than human cardiomyopathy
False; we’ve only pinpointed a few genes
Small dogs are more likely to get ___ (DCM/CVD), while large dogs are more likely to get (DCM/CVD)
CVD
DCM
T/F: There are breed-specific types of DCM
True Doberman Boxer English Cocker Spaniel American Cocker Spaniel Irish Wolfhound Portuguese Water Dog Great Dane
Large breed, male, middle aged dogs are a typical candidate for ___
DCM
What is the pathogenesis of DCM?
Neurohormonal activation -> proliferation of cardiac myocytes and fibroblasts and sodium and water retention -> increased preload -> cardiac remodeling (hypertrophy, dilatation, fibrosis, sphericity) -> Abnormal systolic, diastolic functions and arrhythmias
What are the three occult signs of DCM?
Arrhythmias
Systolic dysfunction
Sudden death
What are the six clinical signs of DCM?
Weakness Exercise intolerance Syncope Weight loss CHF Sudden cardiac death
What five signs of DCM should one look for on a physical exam?
Systolic murmur or S3 gallop (S3 is blood filling ventricle) Arrhythmia (pulse deficit) Weak arterial pulses Left sided CHF Biventricular CHF occasionally occurs
What is seen on ECG of a dog with DCM?
Often, nothing
May see tachyarrhythmia (VT, AF)
What is seen on radiographs of a dog with DCM?
Nothing until overt diation present
Rads can’t assess function
What is seen on an echocardiograph of a dog with DCM?
Can see LV systolic dysfunction
Mitral regurgitation
LA enlargement
What are biomarkers?
Substances that can give information about organ function or dysfunction
What is atrial natriuretic peptide (ANP) useful for?
It is increased in Dobermans with occult and overt DCM
Not sensitive in other breeds
What are brain natriuretic peptide and N-terminal pro-BNP useful for?
NTproBNP increased in overt DCM
BNP sensitive screen for dogs with occult DCM
What is troponin I (cTNI) useful for?
Increased in overt and occult DCM in Doberman
In American cocker spaniels, there is an association between low plasma ___ and DCM. How is this treated?
Taurine
Supplement taurine and L-carnitine
T/F: Female dalmations are more predisposed to DCM than males
False
What is the most commonly represented breed with DCM?
Doberman pinschers
T/F: Nearly 50% of Doberman pinschers will develop DCM in their lifetime
True
When/how do Doberman pinschers develop DCM? What are the two most likely outcomes?
Autosomal dominant inheritance (PDK4)
Adult-onset (usually around 5yrs)
Sudden death
CHF
What is the main sign in the occult phase of DCM for Dobermans?
Progressive LV dysfunction
What does PDK4 do?
It plays a regulatory role in cardiac energy metabolism and fatty acid oxidation
T/F: Approximately 25% of Great Danes will develop DCM
True
T/F: DCM is an X linked dominant inheritance
False; X linked recessive
T/F: DCM is an autosomal recessive sex-linked allele inheritance in Irish Wolfhounds
True
T/F: Atrial fibrillation precedes DCM in many large breed dogs?
True (Great Danes, Irish Wolfhounds, Newfoundlands)
T/F: Univentricular CHF is most common in Irish Wolfhounds with DCM
False; Biventricular is most common
T/F: Newfoundlands often have DCM with no appreciable heart murmur
True
T/F: DCM is an autosomal recessive trait in Portuguese Water Dogs
True
What drugs can be used to treat occult DCM?
ACE inhibitors (Benazapril - Dobermans) Beta blockers (Carvedilol) - use cautiously with gradual increase, not for active CHF Pimobendan - the miracle drug
What drugs that provide inotropic support can be given for dogs with overt DCM? (3)
Dobutamine
Pimobendan
Digoxin
What drugs provide a neurohormonal blockade for dogs with overt DCM? (2)
ACE inhibitors
Spirinolactone
What drugs reduce preload in dogs with overt DCM? (1 and lifestyle change)
Furosemide
Low Na diet
What drugs reduce afterload in dogs with overt DCM? (2)
ACE inhibitors
Pimobendan
What drugs help control ventricular arrhythmia in dogs with overt DCM? (4)
Lidocaine
Mexilitine
Sotalol
Amiodarone
What drugs help control supraventricular arrhythmias in dogs with overt DCM? (3)
Digoxin
Diltiazem
Amiodarone
What class I drugs (Na channel blockers) help treat ventricular arrhythmias?
Lidocaine (IV)
Mexilitine (oral, can cause nausea)
Procainamide (IV slowly)
What class III drugs (K channel blockers) help treat ventricular arrhythmias?
Sotalol Amiodarone (neutropenia, liver dysfunction)
What is arrhythmogenic right ventricular cardiomyopathy?
Fibrous fatty infiltrate of the right ventricular free wall
Previously known as “boxer cardiomyopathy”
Ventricular arrhythmias, syncope, and sudden death
Ventricular systolic dysfunction and dilation also seen
How do boxers inherit ARVC?
Autosomal dominant trait
Deletion of gene encoding for striatin production
What signs characterize the classes of ARVC?
Class I: asymptomatic
Class II: collapse and syncope
Class III: left sided CHF (rare, usually right side first)
All classes have RV arrhythmias
How is ARVC diagnosed?
Arrhythmia (not always) Biomarkers (cTNI - VPCs) Echocardiogram Holter monitor ECG - VPCs - singlet, runs, etc.
How is ARVC treated? (7)
Sotalol Mexilitine Amiodarone Fish oils Pimobendan ACE inhibitors Diuretics
What is atrial standstill?
Destruction and fibrous infiltration of the atrial myocardium results in an inability to transmit signal. See only nodal escape rhythm (Equally positive and negative QRS wave, large T)
What signs are associated with atrial standstill? (4)
Exercise intolerance
Weakness
Syncope
R CHF
When are German Shepherds most at risk for inherited ventricular arrhythmias?
12 weeks to 18 months
What causes inherited ventricular arrhythmias in German Shepherds and how is it treated?
Abnormal sympathetic innervation of the ventricular myocardium
Mexilitine - Sotalol combination
T/F: Plasma cTNI is often elevated with myocardial injury
True
What are three causes of protozoal myocarditis?
Leishmania
Neospora caninum
Toxoplasma gondii
What are two viral causes of myocarditis?
Parvovirus
West Nile
What are two parasitic causes of myocarditis?
Trypanosoma cruzi
Borrelia bergdorferi
T/F: Hypertrophic Cardiomyopathy is usually a primary disease in dogs
False; secondary
T/F: Hypothyroidism can cause systolic dysfunction and increased RV dimensions
False; LV
T/F: myocardial infarction is one of the most common cardiac issues in dogs
False; people!
Doxorubricin toxicity leads to what three cardiac changes?
Myocardial damage
Systolic dysfunction
DCM +/- CHF