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Y4 SA - cardiology > Myocardial disease in dogs and cats > Flashcards

Myocardial disease in dogs and cats Flashcards

1
Q

Types of myocardial disease

A

Primary myocardial dz
1. dilated cardiomyopathy (DCM)
2. arrhythmogenic right ventricular cardiomyopathy (ARVC)
3. hypertrophic cardiomyopathy (common in cats)
4. restrictive cardiomyopathy (common in cats)

Secondary myocardial dz
1. infective myocarditis
2. deficiency dz
3. toxic causes

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2
Q

What is the most common form of myocardial dz in dogs?

A
  • DCM
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3
Q

Prevalence of DCM in cats

A
  • rare
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4
Q

How is DCM characterised?

A
  • impaired myocardial contractility with dilation of LV (± RV)
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5
Q

What is common with DCM?

A
  • tachyarrhythmias
    – supraventricular ± ventricular
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6
Q

DCM pathophysiology

A
  • eccentric hypertrophy of the LV
  • systolic failure (forward failure)
    – heart doesn’t contract enough so not enough oxygen gets to the system as not enough blood moves forwards
  • diastolic failure (backward failure - congestion)
    – every time the ventricle tries to fill and contract it doesn’t completely empty, so you get congestion and blood backs up in the system
  • LA dilation and increased LAP
  • right side can also be affected
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7
Q

DCM histopathology

A

2 distinct types of HP are reported, these are thought to relate to the underlying mechanism of the dz
- narrow (attenuated) myocardial cells with a wavy appearance (Newfoundlands)
- myofibre degeneration, myocyte atrophy and lysis, fatty infiltration and fibrosis (Boxers, some Dobermans)

Otherwise often non-specific and include:
- scattered areas of myocardial necrosis
– myocardial degeneration and fibrosis
– inflammatory cell infiltrates are inconsistent but an active myocarditis is rare

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8
Q

DCM signalment

A
  • breed predispositions (genetic basis)
    – Doberman, Newfoundland, IWH, St Bernards, Labs, Great Dane, Cocker spaniels, Boxers (ARVC), GSD
    – Boxers autosomal dominance inheritance pattern
    – but different breeds have very different prognosis with the same dz
    – Cocker spaniels - 2y with appropriate tx
    – Doberman - often a few weeks
  • usually middle aged dogs (has been reported in puppies as young as 6m)
  • usually dogs >12kg
  • males tend to be more severely affected but no gender predilection
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9
Q

DCM - how does this condition cause dz?

A
  • loss of systolic function results in low cardiac output (loss of contraction)
  • low cardiac output results in forward failure
  • sympathetic, hormonal and renal compensatory mechanisms activated therefore -> maintain cardiac output by increasing HR, peripheral vasoconstriction and volume expansion
  • ventricle fails to empty, which results in increased ventricular diastolic pressure
  • this in turn results in compromised coronary perfusion, worsening myocardial function further and resulting in arrhythmias
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10
Q

DCM - how do they present?

A

Occult phase
- can be prolonged
- screening programmes of specific breeds to identify this phase
– 24h holter monitor (>50VPCs/24h)
– echocardiography
- non-symptomatic

Symptomatic phase
- usually present in CHF
- CS: weight loss, sudden death, soft murmur, atrial fibrillation, lethargy, exercise intolerance, dyspnoea (signs of left sided failure)

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11
Q

Why use a Holter monitor?

A
  1. to monitor for HR control
  2. unexplained syncope or collapse
  3. arrhythmias
  4. monitoring therapy
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12
Q

DCM - clinical examination

A

Variable depending on the degree of myocardial dysfunction
- tachycardia ± arrhythmias -> AF, VPCs, VT
- variable pulses ± pulse deficits if dysrhythmic
- signs of LCHF ± RCHF
- gallop sounds - if in sinus rhythm
- soft MR/TR murmurs

If forward failure (often bad news)
- pale mm
- sluggish crt
- cool extremities

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13
Q

DCM investigations

A
  • CE: usually in CHF
  • echocardiography: definitive diagnosis
  • clinical pathology: complications/co-existing dz
  • radiography: confirms CHF
  • ECG if dysrhythmic
  • blood pressure esp once on tx
  • 24h Holter monitor: more for screening
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14
Q

DCM echocardiograph findings

A
  • large, round, poorly contractile LV
  • poor systolic function (poor contractility)
  • dilated, round LA
  • ± mitral regurgitation small/moderate due to dilation
  • ± right sided changes
  • m mode confirms dilated, hypomotile LV
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15
Q

DCM electrocardiography

A
  • findings are very variable
    – normal
    – wide ± tall complexes (occasionally small complexes
  • many DCM dogs have ventricular arrhythmias
  • treat heart failure
  • treat arrhythmias if haemodynamically unstable
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16
Q

Arrhythmogenic right ventricular cardiomyopathy - what is it? breed? histopath findings?

A
  • rhythm disturbance caused by the cardiac muscle in the right ventricle
  • usually Boxers
  • myofibre atrophy, fibrosis and fatty infiltration
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17
Q

3 stages of ARVC

A
  1. asymptomatic with ventricular arrhythmias
  2. symptomatic - normal heart size and LV function but dogs are syncopal/weak from ventricular arrhythmias
  3. CHF - poor myocardial function, CHF and ventricular arrhythmias
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18
Q

ARVC CS

A
  • can appear any age, mean age 8y
  • ventricular arrhythmias
  • supra-ventricular arrhythmias
  • > 500 VPCs/24h
  • but spontaneous variation of up to 80%
  • syncope
  • sudden death
19
Q

Diagnosis and tx of ARVC

A
  • investigations as for DCM but 24h Holter monitor is necessary
  • may need further physiological monitoring -> refer these cases
  • but never underestimate a syncopal/collapsing Boxer

Tx
- treat any heart failure
- anti-arrhythmic medication -> soltalol

20
Q

Causes of secondary myocardial dz

A
  • myocarditis -> infectious/non-infectious
  • doxorubicin -> acute and chronic cardiotoxicity
  • metabolic / nutritional toxicities
    – L-carnitine deficiency
    – Taurine deficiency -> grain free diets?
  • ischaemic heart disease
  • tachycardia-induced cardiomyopathy -> most commonly seen with SVT
21
Q

Feline cardiomyopathies - prevalence

A
  • myocardial disease is most common in cats
22
Q

Feline cardiomyopathies - types

A
  • HCM: most common in literature
  • RCM: restrictive cardiomyopathy
  • DCM
  • ARVC
  • FUCM: feline unclassified cardiomyopathy
23
Q

Feline cardiomyopathies - cause

A
  • exact cause unknown but a genetic bases is thought to underlie many cases of HCM
24
Q

What is HCM

A

= hypertrophic cardiomyopathy
- inappropriate myocardial hypertrophy of a non-dilated left ventricle, occurring in the absence of an identifiable stimulus

25
HCM diagnosis
- diagnosis of exclusion -- need to make sure no other cause
26
What things other than HCM can cause concentric hypertrophy?
- aortic stenos: ventricles struggle to inject blood - systemic hypertension: primary, diabetes mellitus, Cushing's dz - metabolic disorders capable of inducing hypertrophy: hyperthyroidism, acromegaly - renal dz and associated hypertension
27
2 clinical forms of HCM
1. obstructive - 42% of cats - great majority of dogs - ventricular walls become so thick -> systolic anterior motion of mitral valve -> dynamic left ventricular outflow tract obstruction - get turbulent flow in the LVOFT (aorta) - concurrent eccentric jet of mitral regurgitation along the posterior wall of the LA 2. non-obstructive
28
Systolic anterior motion of the mitral valve in obstructive HCM
1. papillary muscle displaced towards the septum 2. mitral valve malalignment 3. narrowed LVOT (Venturi effect)
29
HCM signalment
- 3 genetic mutations now discovered -- 2 in Maine Coons & 1 in Ragdolls - rare in dogs
30
HCM pathology
- excessive LV wall/septum hypertrophy without dilation - extent and distribution of LVH is variable - LA enlargement varies depending on the severity of diastolic dysfunction
31
RCM aetiology
- unknown aetiology probably multifactorial as there is range of pathological findings - could be end stage of other disease processes
32
2 forms of RCM
- endomyocardial - myocardial
33
RCM histopathology changes
- extensive endocardial, subendocardial or myocardial fibrosis
34
RCM pathology
- atrial enlargement (usually very large) due to poor ventricular filling and regurgitation - mild LV hypertrophy can happen - diastolic failure (poor filling) -> backwards failure
35
RCM signalment, diagnosis & management
- all similar to HCM
36
Feline cardiomyopathy presentation
- very variable - often present in heart failure - good at hiding dz - range from asymptomatic cat with a heart murmur to recumbent, cold dyspneic cat via congestive cardiac failure - often increased resp rate at rest - if stressed then can lead to severe dyspnoea - often present at a late stage - usually dyspnoeic - frequently present after fluid tx/GA/steroid use - acute onset lameness/paralysis - ATE - sudden death
37
Feline cardiomyopathy clinical exam
General CE CV system - mm colour - femoral pulses (bilateral, quality, rhythm, pulse deficits) - palpate apex beat on both sides - chest compressibility - chest percussion - auscultation - not always tachycardia
38
Feline cardiomyopathy CE findings
- many have auscultatory abnormalities - systolic murmur PMI sternal border - often dynamic murmur - comes and goes - gallops sounds with severe HCM - crackles throughout lung fields if pulmonary oedema - dull lung and heart sounds if pleural effusion
39
Feline cardiomyopathy echo findings
- LV hypertrophy often asymmetrical - basal septum frequently affected - hypertrophied, hyperechoic, irregular papillary muscles - LVH >6mm in diastole - 2DE measurements as well as MM - LV lumen is usually small - LA enlargement is variable - mild to severe - can have obstructive component: systolic anterior motion of the mitral valve (SAM)
40
Radiography of feline cardiomyopathy
- imperative for diagnosing heart failure - ideally only when pts are stable - cariogenic pulmonary oedema can be very variable in cats with heart failure - pleural effusion is quite common - cardiomegaly - venous congestion
41
Feline DCM - cause
- taurine deficiency was a major cause prior to the 80s - taurine levels in commercial diets has been increased and now DCM secondary to taurine deficiency is rare - DCM often end stage of another myocardial abnormality - toxic, drug induced, CM or infection
42
Features of feline DCM
- features similar to dogs - poor contractility - dilation of all 4 chambers esp LV and LA - arrhythmias (common) - pleural effusion (common) - older cats - frequently present in heart failure - some present in output failure - bradyarrhythmias can also occur - diagnosis as with HCM - always check taurine levels & supplement as indicated - tx as HCM when in CHF + pimobendan (not licenced but need to improve contractility)
43
Hypertrophic cardiomyopathy in dogs
- rare in the dog - cause unknown: genetic basis suspected - diastolic failure - young to middle aged small breed dogs - male predisposition - syncope/sudden death can occur - CHF rare but can occur - dysrhythmias - gallop heard in some dogs if in sinus rhythm

Y4 SA - cardiology (15 decks)

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