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What are the main canine cardiomyopathies? (3)
- dilated cardiomyopathy (DCM), arrhythmogenic right ventricular CM (ARRV)
- persistent atrial standstill (atrial CM)
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What are secondary cardiomyopathies that occur in dogs? (6)
myocarditis, hypothyroidism, CM of chronic volume overload, CM of chronic pressure overload, tachycardia-induced CM, drug-induced CM (doxorubicin, monensin)
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What is DCM?
primary heart muscle disease characterized by cardiac dilatation and systolic dysfunction of one or both ventricles
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What are hypothesized causes of canine DCM? (5)
familial/genetic, immune-mediated, viral, metabolic, nutritional
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What is the mutation related to Boxer ARVC?
Striatin
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What is the mutation associated with Doberman DCM?
PDK4
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Canine DCM is a(n) ___________ disease, with different phenotypes in _____________.
heterogenous; different breeds
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What breeds are commonly associated with CM, and which does each breed get? (4)
Doberman Pinscher (genetic DCM), Boxer (genetic ARVC), American Cocker Spaniel (taurine/carnitine), Springer/Sussex Spaniel (atrial CM)
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Cardiomyopathies are most common in... [signalement]
large breed, male, middle aged dogs
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What are the 3 clinical phases of canine CM?
genetic predisposition--> preclinical (occult) phase (arrhythmias)--> heart failure (weakness, exercise intolerance, syncope, weight loss, CHF, sudden cardiac death)
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What clinical signs are associated with the heart failure phase of canine CM? (6)
weakness, exercise intolerance, syncope, weight loss, CHF, sudden cardiac death
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What are the most common presentations of Doberman DCM? (4)
ventricular arrhythmias (LV VPCs), syncope, sudden death, L-CHF (sometimes R)
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What PE findings might be associated with Doberman DCM? (5)
soft systolic murmur, S3 gallop, arrhythmia w/ pulse deficit, weak arterial pulses, L-CHF/biventricular CHF
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Why is the murmur associated with Doberman DCM always soft?
ventricles that cannot contract properly will never develop a loud murmur
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What ECG findings are common with Doberman DCM? (4)
often sinus rhythm or sinus tachy, left VPCs, ST segment depression, wide QRS complexes
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How do we detect occult DCM in Dobies? What are common initial abnormalities?
Holter ECG for 24 hours; only VPCs/ ventricular ectopy
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What radiographic findings are common with Doberman DCM? (4)
left-sided enlargement, pulmonary venous distention, perihilar/ patchy distribution of pulmonary edema, +/- pleural effusion
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Echo findings with Doberman DCM. (5)
[confirm diagnosis] LA and LV dilatation with wall thinning, LV systolic dysfunction, secondary mitral regurg (mitral valve may look normal!!), restrictive LV filling, evidence of pulmonary hypertension
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What do you see on M-mode with Doberman DCM?
LV hypokinesia (small SF)
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What are the key problems that need to be addressed with Doberman DCM? (5)
increased preload, increased afterload, decreased systolic function, tachyarrhythmia, myocardial remodeling
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What is the treatment plan for symptomatic Doberman DCM? (7)
diuretics, ACEi, low salt diet, Pimobendan, Digitalis and/or Diltiazem (if supraventricular tachyarrhythmia), Sotalol or Mexiletine (if ventricular tachyarrhythmia), Spironolactone/ Carvedilol, ACEi, Fish oils (cardioprotection)
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How do you handle occult Doberman DCM? (5)
cardiac protection (ACEi, fish oils), mild exercise restriction, Pimobendan (if chamber enlargement), ACEi (prevent volume overload), Sotalol or Mexiletine(if vtach arrhythmia)
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What is the acute therapy for CHF in a dog with CM? (7)
- [FONTS Plus]
- Furosemide, Oxygen, Nitroglycerine, Sedation, Tapping (if effusion), Pimobendan
- Cardiogenic shock?--> Dobutamine
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What is the chronic therapy for CHF in a dog with CM? (6)
furosemide, enalapril, pimobendan, digoxin +diltiazem (if afib), spironolactone, +/- fish oil
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What is the prognosis for Doberman DCM?
- was poor before Pimobendan
- with Pimobendan, <1 year
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What are characteristics of Cocker Spaniel DCM? (4)
adult onset, L or R-CHF, reversible, good prognosis with taurine and carnitine supplementation
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Persistent atrial standstill (atrial CM) occurs most commonly in __________ as a result of...
English Springer Spaniels; selective destruction of atrial myocardium, resulting in atrial standstill.
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What are early clinical signs of atrial CM? (4)
exercise intolerance, weakness, syncope, R-CHF
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What are ECG findings with atrial CM in Springer Spaniels? (2)
very small P waves (may be absent), nodal and ventricular escapes
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What are gross and microscopic findings with atrial CM? (1 of each)
severe RA and RV dilatation, massive loss of myofibers
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What is the therapy for atrial CM? (2)
symptomatic treatment of heart failure, cardiac pacemaker
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What is Irish Wolfhound CM?
"lone" atrial fibrillation that can later develop into full blown DCM
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In late disease, what are findings associated with Irish Wolfhound CM? (2)
pleural effusion, often chylous
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What is the therapy and prognosis for Irish Wolfhound CM?
- Therapy: Digoxin and Diltiazem, if develop CHF, standard txt
- Prognosis: good
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What is Boxer ARVC? (5 characteristics)
primary myocardial disease characterized by RV tachyarrhythmias, syncope, sudden death, heart muscle atrophy, fatty infiltration of RV free wall
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What are the categories of Boxer ARVC? (3)
- Category I: asymptomatic
- Category II: collapse and syncope
- Category III: L-CHF
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All 3 categories of Boxer ARVC are characterized by ___________.
RV arrhythmias (sometimesatrial arrhythmias)
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What are echo findings with Boxer ARVC?
- categories I and II are normal on echo
- category III has RV dilatation on echo
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What are ECG findings common with Boxer ARVC? (3)
RV bigeminy with sinus and VPCs, right axis shift, RV vtach
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How are arrhythmias associated with Boxer ARVC often discovered?
Holter ECG for 24 hours
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What is the therapy for Boxer ARVC? (5)
- [if symptomatic] [SPAM] Sotalol, Procainamide, Amiodarone, Atenolol, Mexiletine
- +/- fish oils
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What are primary causes of myocarditis? (5)
Chagas' myocarditis (T. cruzi), Parvovirus, Toxoplasma, Neospora, Lyme
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What are the stages of Chagas' myocarditis and what does each cause? (2)
- Acute: arrhythmia (most common AV block)
- Chronic: right side myocardial failure, ventricular ectopy
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What are secondary causes of myocarditis? (2)
bacterial and septic
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What drugs are commonly used to treat acute (in hospital) ventricular ectopy in a dog? (5)
- [First line] IV lidocaine
- [Second line] IV procainamide, amiodarone, esmolol, magnesium salts
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What drugs are used for the chronic (home treatment) of ventricular ectopy in dogs? (5)
[SPAAM] sotalol, procainamide, amiodarone, atenolol, mexiletine
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What are differentials for LV hypokinesia in a dog? (4)
DCM, taurine deficiency, volume overload (valve regurg, shunts, RAAS activation), end-stage heart failure
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