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Year 4 Small Animal Studies > Cardiology: Canine Dilated Cardiomyopathy > Flashcards

Cardiology: Canine Dilated Cardiomyopathy Flashcards

1
Q

What are the different primary cardiomyopathies?

A
  • Dilated cardiomyopathy
  • Arrhythmogenic right ventricular cardiomyopathy
  • Hypertrophic cardiomyopathy
  • Atrial myopathy (atrial standstill)
  • Restrictive cardiomyopathy
  • Unclassified cardiomyopathy

RCM and UCM very rare in dogs

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1
Q

What are the different primary cardiomyopathies?

A
  • Dilated cardiomyopathy
  • Arrhythmogenic right ventricular cardiomyopathy
  • Hypertrophic cardiomyopathy
  • Atrial myopathy (atrial standstill)
  • Restrictive cardiomyopathy
  • Unclassified cardiomyopathy

RCM and UCM very rare in dogs

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2
Q

What is the most common primary cardiomyopathy?

A

Dilated Cardiomyopathy
Idiopathic

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3
Q

What breeds are more commonly affected by ARVC?

A

Boxers and English bull dogs

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4
Q

What predisposes to HCM?
What breeds seem predisposed?

(hypertrophic cardiomyopathy)

A
  • Secondary to aortic stenosis, systemic hypertension of infiltrative disease
  • Terrier breeds, pointer dogs, golden retrievers
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5
Q

What breeds has atrial cardiomyopathy been described in?

A

ESS and labrodors

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6
Q

What are the different causes of secondary cardiomyopathies?

A
  • Tachycardia induced cardiomyopathies
  • Drugs/toxins
  • Infiltrative
  • Metabolic
  • Nutritional
  • Inflammatory
  • Connective tissue disease
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7
Q
  1. What drugs/toxins can cause cardiomyopathies?
  2. What can be a infiltrative cardiomyopathy cause
  3. What metabolic/endocrine disorders can cause cardiomyopathy?
  4. What are nutritional causes of myopathy?
A
  1. Chemotherapeutic drugs, cyclophosphamide, heavy metals
  2. Neoplasia, glycogen storage disease, amyloidosis
  3. Hypo/hyperthyroidism, diabetes mellitus, acromegaly
  4. Taurine deficiency, L-carnitine
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8
Q

What are inflammatory causes of secondary cardiomyopathies are there?

(myocarditis)

A

Infectious:
* Canine distemper, Parvo (herpes, corona)
* Bartonella
* Borrelia, leptospira, leishmania
* Toxoplasma, trypanosoma cruzi
* Cryptococcus, histoplasmosis
* Aspergillus

Non-infectious:
* Viral- autoimmune
* Drug hypersensitivity
* Trauma
* Systemic inflammatory diseases

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9
Q

What is the definition of DCM?

A

Primary myocardial disorder characterised by a dilation of the four cardiac chambers and a reduction in contractility

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10
Q

What breeds and ages are more typically affected by DCM?

A
  • Affects large and giant breed dogs- can be small
  • Middle-ages/old

Poor prognosis

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11
Q

Describe the pathology of DCM?

A
  • Dilation of any of the 4 chambers L>R
  • Increased heart weight: BW ratio
  • LV thickness : LV diameter reduced
  • Valvular lesions: age related, mitral regurgitation
  • Histological lesions- attenuated wavy fibres, fibrofatty degeneration
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12
Q

Describe the pathophysiology of DCM?

A
  • Impaired systolic function
  • Redcued cardiac output
  • Activation of sympathetic and RAAS
  • Vasoconstriction, increased HR and contractility
  • Myocardial hypertrophy, chamber dilation
  • Increased myocardial O2 demand
  • Increased call stress CO and CP maintained
  • Further myocardial death then fibrosis
  • Impaired systolic function
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13
Q

How do the following breeds vary with DCM?
1. Dobermans
2. Great Danes
3. Irish wolf hounds
4. Newfoundlands
5. Cockerspaniels
6. Springerspaniels
6. Labradors
7. Dalmations

A
  1. Long occult phase, sudden death common
  2. Atrial fib with CHF, sudden death common
  3. can present with AF then progress to overt DCM
  4. Taurine defiency identified with improvement on supplement
  5. Reduced contract and enlarged cardiac dimensions
  6. reduced contract and enlarged dimensions- slow progression
  7. Predisposed to pathways resulting in SVT
  8. Associated with protein restricted diet
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14
Q

What is the definition of arrhythmogenic right ventricular cardiomyopathy?

A

ARVC usually involved the right ventricle with progressive loss of myocytes with faty of fibrofatty tissue replacement resulting in regional or global abnormalities

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15
Q

What are the three forms of ARVC?

A
  • Asymptomatic- VPCs detected by holter monitoring
  • Symptomatic- arrhythmias, normal systolic function
  • Structural changes of the heart and arrythmias
16
Q

What is the aetiology of arrythmogenic right ventricular cardiomyopathy?

A
  • Fibrofatty tissue replacement particularly in the right ventricle- also LV/atria
  • Fatty tissue or scarring may be seen grossly
  • Possibly dilated heart
17
Q
  1. How is DCM preclinical phase characterised?
  2. How does this progress?
A
  1. No clinical signs, ventricular arryhtmias frequently present and sudden death can occur
  2. Signs of CHF and forward failure, left- right and biventricular CHF
18
Q

What may be found on physical examination of a dog with DCM?

A
  • Cardia cachexia ‘muscle wasting’
  • Pale MMS, Sluggish CRT
  • Tachypnoea/dyspnoea
  • Weak femoral pulses
  • Jugular distension, abdominal effusion, positive hepatojugular reflex

Auscultation
* Lungs- increased respiratory sounds, crackles, tachypnoea/dyspnoea (pulmonary oedema)
* Heart- tachycardia, arrhythmias, soft systolic murmur, left apex- mitral regurgitation
* Gallop sound (S3)- rapid ventricle filling

19
Q

What clinical pathology might be different with DCM?

A
  • Pre-renal azotaemia common
  • Mild increases of liver enzymes (hepatic congestion)
  • Albumin low if effusions
  • Rule out hypothyroidism- TT4,TSH
  • Cardiac markers:
    Troponin- myocardial cell damage, not specific for cardiac disease
    NT-proBNP- marker for heart stretch
20
Q
  1. What arrythmias are common with DCM?
  2. What evidence of chamber enlargment can an ECG show?
A
  1. AF and VPCs
  2. Ventricular enlargment patterns: tall R waves, prolonged QRS duration, ST segment changes
    Atrial enlargment patterns: wide, tall P waves, prolonged QRS
21
Q

How can a DV and right lateral radiograph show signs of DCM?

A
  • Cardiomegaly- lateral view
  • Left atrial enlargment
  • Pulmonary vasculature- distended lobar pulmonary veins
  • Lung patterns
    interstitial- early pulmonary oedema
    alveolar- advanced pulmonary oedema
  • Check abdomen for abdominal effusion
22
Q
  1. How does DCM present in simple terms with echo?
  2. What specific changes are there for chambers?
  3. What specifically changes about contractility?
A
  1. Rounded, dilated, poor contractility
  2. Increase M mode of LV, increased LA/Ao ratio (>1.5), increased E point to septal separation, usually mild MR
  3. Decreased FS%, decreased EF%, decreased LV ESV, increased systolic time intervals, asynchronus contraction of LV

Diagnosis is exclusion

23
Q

What is holter monitoring useful for with DCM?

A
  • Permits diagnosis in preclinical phase (arrythmias without chamber dilation/systolic dysfunction)
  • Assesment of arryhtmias- needed for treatment
  • Assessment of response to treatment
24
Q
  1. What does AF mean on a holter?
  2. What do VPCs, VT cause?
A
  1. HR <140 bpm
  2. Reduced number of ventricular ectopic beats, reduced malignancy of ectopic complexes
25
Q

How is preclinical disease of DCM treated?

A

Pimobendan

26
Q

What are the different targets of congestive heart failure?

A
  • Reduce preload
  • Inotropic support
  • Reduce afterload
  • Control of arrhythmias
27
Q

How is preload reduced with CHF from DCM?

A

Diuretics and Venodilators
* Furosemide- essential in CHF (loop diuretic)
* Torasemide- more potent then furosemide
* Spinonolactone- anti-remodelling, weak diuetic
* Thiazide- in progression, if ascites present and furosemide insufficient
* Glyceryl trinitrate- percutaneous venodilator- acute pulmonary oedema

28
Q

What inotropic support can be given for CHF?

A
  • Pimobenden- positive inotrope and vasodilator
    calcium sensitizer, phosphodiesterase III inhibitor
  • Dobutamine
    Sympathomimetic
    In emergency situations
    Can be pro-arrythmic
28
Q

What inotropic support can be given for CHF?

A
  • Pimobenden- positive inotrope and vasodilator
    calcium sensitizer, phosphodiesterase III inhibitor
  • Dobutamine
    Sympathomimetic
    In emergency situations
    Can be pro-arrythmic
29
Q

How is afterload reduced?
What drugs are used?

A

Vasodilators
* ACE inhibitors- benazepril, enalapril, ramipril, imidapril

30
Q

What drugs can be used for atrial fibrillation?

A
  • Calcium channel blockers- diltiazem
  • Digoxin- reduce dose if renal failure/overweight
    Check K+ levels
  • Beta-blockers- less safe- more negative inotropic and chronotropic
    Do not use in heart failure
31
Q

What drugs can be given for ventricular arrythmias?

A
  • Lidocaine- emergency treatment
  • Sotalol- for oral treatment
  • Mexiletine- requires a VMD import license but same vaughn-williams class as lidocaine
  • Amiodarone
32
Q

What is the prognosis for DCM?

A

Very variable
* Some breeds have extremely short MST
* English cockers >2y
* Occult disease in dobermans quickly progresses
* Negative prognostic indicators- young age, ascites, dyspnoea, atrial fibrillation

Year 4 Small Animal Studies (97 decks)

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