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Y4 SA - Cardio-Respiratory > Canine dilated cardiomyopathy and other myocardial diseases > Flashcards

Canine dilated cardiomyopathy and other myocardial diseases Flashcards

1
Q

What is a cardiomyopathy?

A

Myocardial disorder in which the heart muscle is structurally and functionally abnormal

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2
Q

Which cells make up heart muscle?

A

Cardiomyocytes

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3
Q

Name the most common cardiomyopathy in dogs

A

Dilated cardiomyopathy

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4
Q

List the 4 primary cardiomyopathies in dogs

A
  • Dilated cardiomyopathy (DCM)
  • Arrhythmogenic right ventricular cardiomyopathy (ARVC)
  • Hypertrophic cardiomyopathy (HCM)
  • Atrial cardiomyopathy (can also be called atrial standstill)
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5
Q

List some causes of a secondary cardiomyopathy

A
  • Tachycardia induced
  • Systemic hypertension
  • Drugs/toxins
  • Infiltrative disease e.g. neoplasia
  • Metabolic/endocrine disease
  • Nutritional
  • Inflammatory: myocarditis
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6
Q

What is the most common cause of nutritional cardiomyopathies?

A

Taurine deficiency

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7
Q

Define dilated cardiomyopathy

A

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

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8
Q

Which animals are typically affected by dilated cardiomyopathy?

A
  • Generally affects large and giant breeds
  • Middle aged/old dogs
  • No sex predisposition
  • Guarded/poor prognosis
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9
Q

The prevalence of DCM is highest in which dog breed?

A

Dobermann

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10
Q

Describe the gross pathology of a dog with DCM

A
  • Dilatation of any of the 4 cardiac chambers (L>R): eccentric hypertrophy
  • Increased heart weight: BW ratio
  • LV thickness : LV diameter reduced
  • Valvular lesions: age related, due to mitral regurgitation caused by valvular annulus stretching
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11
Q

How does DCM appear on histology?

A
  • Attenuated fibers (atrophied): Myocytes thin, degeneration, fibrosis
  • Fibro-fatty infiltration: Myocyte lysis, vacuolation, fibrosis, fatty infiltration
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12
Q

In DCM what happens once there is damage to the cardiomyocytes?

A
  • Damaged cells no longer function effectively as a syncytium
  • Cell death and fatty or fibrous replacement (as per histopathology)
    -> IMPAIRED SYSTOLIC FUNCTION
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13
Q

What are the consequences of impaired systolic function?

A

-> Reduced cardiac output -> activation of symp NS and RAAS -> vasoconstriction, increased HR + contractility, myocardial hypertrophy, chamber dilation -> increased myocardial oxygen demand, wall stress -> further myocardial cell death, myocardial fibrosis -> FURTHER impaired systolic function -> (round in a loop)

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14
Q

Name 3 similarities of DCM and mitral degenerative valve disease

A
  • Enlargement of left ventricle (+/- right)
  • Enlargement of left atrium
  • Mitral regurgitation
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15
Q

Name some differences of DCM and mitral degenerative valve disease

A

DCM:
- Mild mitral regurgitation
- Reduced systolic function
- Decreased wall contractility
- LV>LA
MDVD:
- Lots of mitral regurgitation
- Normal (?)/hyperdynamic systolic function
- Normal wall contractility
- LA>LV

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16
Q

Describe DCM in Dobermanns (breed variation)

A
  • High prevalence (approx. 60%)
  • Slowly progressive, inherited
  • Long asymptomatic preclinical phase
  • Ventricular arrhythmias (♀)
  • Sudden death
  • Cardiomegaly less obvious
  • Annual screening, short survival after CHF
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17
Q

ARVC stands for?

A

Arrhythmogenic right ventricular cardiomyopathy

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18
Q

What is Arrhythmogenic right ventricular cardiomyopathy?

A

Involves predominantly the right ventricle with progressive loss of myocytes and fatty or fibrofatty tissue replacement, resulting in regional (segmental) or global abnormalities.

19
Q

Arrhythmogenic right ventricular cardiomyopathy is most commonly seen in which breed?

A

Boxers

20
Q

Describe the three forms of Arrhythmogenic right ventricular cardiomyopathy

A
  1. Asymptomatic – VPCs detected by Holter monitoring
  2. Symptomatic (syncopal) – arrhythmias (VPCs), normal systolic function
  3. Structural changes of the heart (ventricular dilation) + arrhythmias
21
Q

Describe the gross pathology of arrhythmogenic right ventricular cardiomyopathy

A
  • Fatty tissue or scarring may be seen grossly
  • Possibly dilated heart: right ventricle
  • Wall thinning
22
Q

Describe the histopathology of arrhythmogenic right ventricular cardiomyopathy

A

Loss of myocytes with fatty/fibrofatty replacement

23
Q

Describe the features of atrial cardiomyopathy

A
  • Thinning atrial walls
  • Atrial standstill on ECG: no P wave, escape rhythm
  • LA&raquo_space;»> LV on echo
24
Q

Describe the features of hypertrophic cardiomyopathy

A
  • Rare, similar to feline HCM
  • Terrier breeds, Pointer dogs, Golden Retriever
25
Q

Describe a likely clinical presentation of a patient with DCM

A

Adult dogs
Large-giant breeds
Exercise intolerance
Most dogs are in CHF at presentation
- DCM is characterized by a preclinical/occult phase, where no clinical signs are evident, but ventricular
arrhythmias are frequently present and sudden death can occur

26
Q

Upon clinical exam what may you find if you have a dog with DCM?

A
  • Arrhythmia
  • Quiet, soft heart murmur, left apical systolic (if you don’t look for it you won’t find it!!)
  • Dyspnoea, tachypnoea, crackles (if in left sided heart failure)
  • Ascites, jugular distention (if in right sided heart failure)
  • Collapse?
  • Possibly no clinical signs
27
Q

Describe the likely history of a dog with DCM

A

Exercise intolerance
Cough
Increased respiratory rate and effort

28
Q

Compare the clinical presentation of DCM with MVDV

A

DCM:
- Large breeds
- Quiet heart murmur
- Adult dogs
- Collapse more common
- Once in CHF typical symptoms present: exercise intolerance, cough, etc
- Sudden death risk!
MVDV:
- Small breeds
- Loud heart murmur
- Adult dogs
- Collapse less common
- Once in CHF typical symptoms present: exercise intolerance, cough, etc

29
Q

What diagnostic investigations would you carry out with a dog presenting with a suspected DCM?

A
  • History + physical examination
  • Blood pressure
  • Clinical pathology: Biomarkers – troponin as the myocytes are being damaged
  • ECG
  • Radiography
  • Echocardiography
  • Ambulatory ECG
30
Q

Why is blood pressure used as a diagnostic tool in DCM?

A
  • Reflects compensatory mechanisms
  • Rule out hypertension
  • If in heart failure, assess for hypotension
31
Q

What does systolic hypotension indicate?

A

Low if forward failure = systolic dysfunction (heart not contracting as well as it should do)

32
Q

Compare the ECGs of DCM and MDVD

A

DCM:
- Atrial fibrillation
- VPCs
- SVPCs
- Ventricular tachycardia
MDVD:
- Supraventricular premature complexes
- Atrial fibrillation
- Ventricular premature complexes

33
Q

In DCM how is evidence of atrial and ventricular chamber enlargement seen on an ECG?

A

Ventricular enlargement patterns: tall R waves, prolonged QRS duration, ST segment changes
Atrial enlargement patterns: wide, tall P waves, prolonged QRS duration

34
Q

How are thoracic radiographs used to diagnosed DCM?

A
  • Sedation
  • DV + (right) lateral
  • Cardiac size: Tracheal elevation, Bulges?
  • Pulmonary vessels
  • Lung infiltrate
  • Effusions?
35
Q

What is the best diagnostic method to confirm DCM?

A

Echocardiography

36
Q

List the 3 main features seen on echocardiography which indicated DCM

A

Rounded
Dilated
Poor contractility

37
Q

Compare the echocardiography of DCM and MVDV

A

DCM:
- Enlarged left ventricle and atrium but LV>LA
- Dilated and rounded left ventricle
- Thin walls
- Reduced systolic function
- Decreased contractility
- Mild/moderate MR
MDVD:
- Enlarged left ventricle and atrium but LA>LV
- Dilated and rounded left ventricle
- Hyperdynamic systolic function
- Lots of MR

38
Q

Describe the uses of ambulatory ECG Holter monitoring for diagnosis of DCM

A
  • Permits diagnosis of DCM in preclinical/occult phase (arrhythmias without chamber dilation and/or systolic dysfunction), especially in Dobermann and Boxer with ARVC
  • Assessment of arrhythmias – quantification, complexity; need for treatment
  • Assessment of response to treatment
39
Q

What would be seen on a Holter monitoring ECG which would indicate DCM

A

High numbers of VPCs
300-100 = likley affected

40
Q

Name 2 drugs that can be used for DCM therapy in the pre-clinical phase

A

Pimobendan
ACE-inhibitor

41
Q

Once DCM progresses into heart failure how is CHF treated?

A
  • Furosemide: keeps the animals alive when they are in failure so this is the top priority + other diuretics?
  • Pimobendan
  • ACE-inhibitors
  • Spironolactone
42
Q

Which drugs are used in the treatment of arrythmias related to DCM

A

Supraventricular = Diltiazem, Digoxin
Ventricular = Sotalol

43
Q

Describe the prognosis of DCM

A
  • In general guarded-poor, depending on response to treatment
  • Monitoring of response important
  • 6-12m (less in certain breeds)
44
Q

List 4 negative prognostic indicators for DCM

A

Young age
Ascites
Dyspnoea
Atrial fibrillation

Y4 SA - Cardio-Respiratory (10 decks)

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