252 Myocardial Disease Flashcards
What is canine dilated cardiomyopathy?
= a primary myocardial disease characterised by cardiac enlargement and impaired systolic function of one or both ventricles
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What breeds is DCM most likely to occur in?
- large and medium sized breeds.
- US: Doberman Pinscher, Irish wolfhound, grea Dane, and cocker spaniel
- European: Airedale terrier, Doberman Pinscher, Newfoundland, and English Cocker Spaniel.
The difference in breed prevalence suggests an influence of environmental factors, and genetic influences
How does DCM typically present?
- Adult onset, except for Portuguese Water Dog and toy Manchester terrier who are diagnosed prior to 1 year
- Clinical signs: coughing, dyspnea, tachypnoea, syncope, exercise intolerance, and occasionally ascites
What are the findings on physical exam of Dog with DCM?
- soft systolic murmur consistent with mitral valve regurgitation +/- gallop sound (S3)
- tachyarrhythmia of ventricular or atrial origin
What can be the ECG findings of a dog with DCM?
- possibly tachyarrhythmia: AFib +/- vtach
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What are the radiographic findings of a dog with DCM?
Depending on stage of disease, it could indicate atrial and ventricular enlargement (usually left side), +/- pulmonary venous distension and pulmonary oedema.
- some cases can have biatrial and biventricular enlargement.
What are the Echocardiographic findings of a dog with DCM?
- left and sometimes right atrial and ventricular dilation
- ventricular wall may be thin
- concurrent left ventricular systolic dysfunction based upon decreased fractional shortening, ejection fraction, and increased end-systolic volume.
What cardiac biomarkers are useful for diagnosing DCM?
ANP = released in response to increased atrial pressure and stretch
-> increases in occult an overt dilated cardiomyopathy in Doberman’s. Other studies show not specific or sensitive enough to screen in other dog breeds
Cardiac troponin-1 (cTnI)= myocardial injury
- > lack sensitivity and specificity to be used as early marker of DCM.
- high sensitivity assay cTnI recentl available but utility to evaluate occult DCM is not reported
B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP)= released when ventricles are dilated, hypertrophic or increased wall tension and cleaved into two polypeptides.
- > sensitive screening even for dogs in occult stage of disease.
- Doberman’s with DCM show elevated plasma concentrations up to 1.5 yrs prior to developing DCM
What is the cause of DCM in cocker spaniels? How is it managed & treated? What is the prognosis?
American CS
- Cause= low plasma taurine levels in American Cocker Spaniels
- Manage = taurine and l-carnations supplementation -> increase FS% & decrease left ventricular end diastolic and systolic diameter over 4 month period. Although myocardial function did not return.
- Tx = 500mg of taurine and 1 gram of L-carnitine PO q 12h usually for life
- Prognosis = if taurine deficiency not identified then prognosis is poor
English CS
- Cause= English CS get DCM but taurine or carnations not identified. Can have a heritable component as most are from the same kennel.
- Management= Some dogs die suddenly, but many live prolonged, mostly asymptomatic, or long survival with medical management
How do dalmatians present with DCM? How is it inherited? WHat are the ECG findings? What is the Duration of survival?
Inheritance = - male dogs appear over represented but no formal study done
- Presentation = adult-onset and signs of left sided failure (cough, dyspnea) or syncope. Not biventricular heart failure
- ECG findings = sinus rhythm, sinus tachycardia with occasional ventricular ectopy
- Duration of survival= 1.5-30 months with euthanasia due to refractory CHF
- 8/9 dogs fed low protein diets to prevent irate stones, but no L-carnitine or taurine deficiency
How do Doberman Pinscher present with DCM? Inherited? What can be done to detect it early?
Present =
- left/and or right biventricular failure, often with atrial fibrillation or sudden cardiac death
- occult stage = infrequent VPCs, mild ventricular dilation +/- systolic dysfunction +/- diastolic function
- Overt stage = AFib, VPCs, and CHF
- syncope is associated with VTach, and bradycardia associated with episodic weakness and syncope observed in cardiomyopathic Doberman Pinschers
- Inherited = Familial inheritance - autosomal dominant mode of inheritance. USA identified a splice-site mutation in pyruvate dehydrogenase kinase 4 (PDK4)
Detection= measurement for early detection using NT-proBNP
How do Great Danes present with DCM? Inherited? ECG findings?
Inherited=
- appears to be familial disease.
- one study showed mostly male dogs suggesting X-linked pattern of inheritance
Presentation=
- can present for weight loss +/- coughing
- left sided heart murmurs, a gallop and ascites were observed
- ECG= AFib with VPCs
How do Irish Wolfhounds present with DCM? Inheritance? Outcome?
Inherited=
- Familial trait
- mode of inheritance is autosomal recessive with sex-specific alleles.
Presentation=
- AFib is commonly present in the majority
Outcome=
- not well understood but appears slowly, then develops AFi preceding CHF by an average of 2 months
- can die suddenly, commonly euthanised due to heart failure, - biventricular +/- chylothorax
How do Newfoundlands present with DCM? Inherited? ECG findings?
Inherited=
- adult onset with no gender predisposition
Presentation =
- clinical presentation includes dyspnea, cough, innappetance and ascites with left or biventricular heart failure.
- few have heart murmur
- ECG= AFib or isolated VPCs
How do Portuguese Water Dogs present with DCM? Inherited?
Inherited=
- juvenile familial CM and inherited as autosomal recessive linked to chromosome 8.
Present/Outcome=
- Affected puppies from unaffected and died between 2-32 weeks of age, from sudden collapse and death without signs or development of CHF
How is DCM inherited in standard schnauzers present?
Inherited=
- Familial DCM due to deletion and frame-shift mutation in the RNA binding motif protein 20 (RBM20) gene was identified.
- inherited in an autosomal recessive pattern.
How do Toy Manchester Terrier present with DCM? Inherited?
Inherited=
- A rapidly progressive juvenile form of familial DCM reported in the Toy Manchester Terrier and similar to Portuguese Water Dog.
Presentation/outcome:
- Most dogs are less than 1 year of age and typically die suddenly without signs of overt congestive heart failure
How can nutritional cardiomyopathy due to taurine deficiency result in DCM? What level is taurine deficiency? How is it managed?
- low taurine and L-carnatine, but dog have greater ability to synthesise taurine than cats
- common factor for dogs developing DCM is a diet of dr dog food with lamb meal, rice, or both as primary ingredient.
- hypothesised that rice bran or whole rice products may result in decreased taurine levels
Deficiency =- A blood level of <150nmol/mL or plasma levels <4nmol/mL indicates diagnosis of taurine deficiency
Management=
Treat: variable dosages, but 100mg/day PO SID or BID. Inotropic medication such as pimobendan and treatment of heart failure.
- response to treatment is around and improvement in 3-6 months on echo.
- blood levels of taurine reevaluated in 1-2 months
How is a dog with occult dilated cardiomyopathy managed?
- There are few studies evaluating benefit of medical therapy for dogs diagnosed with occult stage DCM
- ACEi: some benefit in dogs with dilation +/- systolic dysfunction
- beta blockers: unknown not enough studies
- pimobinden: PROTECT study, a multi Center double-blinded placebo controlled evaluation identified a survival benefit in Doberman Pinschers given pimobendan in occult stage of disease. Dobermans were given twice-daily pimobendan and time to onset of CHF or sudden cardiac death found significantly longer (718d V 441d)
How are dogs with DCM and CHF treated?
- Benefit form inotropic support-> ideally pimobendan
- Pimobendan has balanced vasodilation and positive inotropic effects and has shown to increase survival (median of 130 days versus a median of 14 days for placebo in one study) in Doberman Pinschers with DCM when given at 025mg/kg PO q 12h
- ACEi and diuretics should be started as needed
- nutritional supplements like taurine
- Fatty acids if in cachexia
- Digoxin +/- diltiazem is used in toe management of atrial fibrillation and congestive heart failure
How should dogs with DCM and ventricular arrhythmias?
- Caution if systolic dysfunction is present: Sotalol (beta blocker + potassium channel blocker)
- Mixelitine: 5-6 mg/kg PO q 8h can decrease arrhythmia
- Amiodarone in Dobermans at a dose of 10mg/kg PO q 12h for 5 days then 5mg/kg q 24h
- Evaluate serum drug concentrations, complete blood counts (neutropenia), and serum liver enzymes
What are negative prognostic indicators?
- Age of onset of clinical signs
- pleural effusions
- pulmonary oedema
- ascites
- atrial fibrillation
- end systolic volume index
- ejection fraction
- restrictive pattern of trans mitral flow
How is ARVC inherited in Boxer dogs? How do dogs present with clinical signs?
- familial disease and inherited as autosomal dominant trait
- variable genetic penetrance and dogs have many different presentations including asymptomatic, syncope, sudden death, and systolic dysfunction.
- homozygous mutant dogs exhibit severe forms of ARVC including higher number of ventricular arrhythmias, sudden death events, and rare structural heart disease (type III ARVC)
What is the presentation and clinical signs of a dog with ARVC?
Presentation:
- syncope, or episodes of syncope after period of exercise or excitement
- Exercise intolerance or lethargy
- Sudden death
- 10% present with left or biventricular heart failure
Physical exam:
- can be Normal
- tachyarrhythmia
- ventricular dilation and systolic dysfunction — termed type III ARVC
- systolic murmur +/- gallop auscultation at left apex
- signs of right heart failure - ascites & jugular distension
- ** left basilar systolic murmu not indication of boxer ARVC
How do biomarkers help with the diagnosis of Boxer ARVC?
- variable value
- Cardiac troponin I: significant elevated and correlated with VPC number and complexity of arrhythmia. BUT some dogs had lower levels of cTnI that overlapped with normal boxers
- BNP is not a useful indicator of disease
What are the ECG findings of a fog with ARVC?
- A VPC may be singly, in pair and in runs of paroxysmal ventricular tachycardia
- ## VPC’s have left bundle branch block in leads I, II, III, and AF consistent with right ventricular origin of this arrhythmia.
What are the thoracic radiograph findings of boxers with ARVC?
- usually in normal limits
- small number with left ventricular dilation and systolic dysfunction (type III ARVC), generalised cardiomegaly and pulmonary oedema +/- pleural effusion
What are the echo findings of a dog with ARVC?
Ventricular dilation and systolic dysfunction may occur but in most cases affected dogs have normal chamber sizes and systolic function.
What are the indications for treatment in a boxer dog with ARVC?
- if arrhythmia detected in asymptomatic dog then Holter monitor to evaluate arrhythmia. Treat if >1000 VPC/24hr period, runs of VTach, or evidence of RonT phenomenon.
- Homozygous positive for the striating mutation may need treatment earlier as it is more severe
- Treatment has no evidence for altering outcome, but will decrease PVC’s and syncopal episodes.
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What treatments are indicated for boxers with ARVC?
- Sotalol 1.5-3 mg/kg PO q12h
OR - Mixelitine 5-6 mg/kg PO q 8h
- In some cases both may improve to be effective.
- Ideally Holter monitor placed before starting therapy and repeated 2-3 weeks after starting therapy to monitor effect of medication.
- One study showed that fish oil supplementation orally 6 weeks reduced VPCs, but no to a degree that could be due to day-to-day variation.
- If systolic dysfunction and ventricular dilation (from echo) treat DCM (pimobendan, ACEi, diuretic)+ supplement L-carnations 50mg/kg q 8-12h
What is the prognosis of dogs with ARVC?
- Risk of sudden death
- many live for year on antiarrhythmics without clinical signs, but some develop ventricular dilation and systolic dysfunction.
What is myocarditis?
= a myocardial disease characterised by presence of myocardial necrosis or degeneration and inflammation
What causes myocarditis?
Overall a variety of physical, chemical, and infectious agents can damage the myocardial tissue and evoke inflammatory response -> results in chamber enlargement, myocardial dysfunction (similar to DCM), and tachyarrhythmia/bradyarrhythmia
- Trypanosoma Cruzi (North America)
- Leishmania
- Parvovirus
- West Nile virus
- Fungal myocarditis (blastomyces)
- bacteria: Bacillus pill form is, Citrobacter koseri, and Borreia burgdorferi
What is atrial myocarditis?
- Form of myocarditis limited to atria
- unexplained arrhythmia including atrial fibrillation associated with inflammation or infection of right atria.
- Intermittent asystole with syncope was observed in do with lymphocytes, macrophages, and neutrophils throughout right and lesser extent the left atrium.
What is myocardial infarction? What causes it?
- Acute myocardial infarction are uncommon rom of myocardial disease in dogs and most commonly associate with concurrent systemic or cardiac disease that lead to thromboembolic state.
- Conditions include: endocarditis, neoplasia renal disease, IMHA, and pancreatic disease.
