Advanced CV disease of dogs

Question 1

What are the 3 main types of acquired CV disease that occur in dogs?

Answer 1

DMVD - endocardiosis or myxomatous valve disease
DCM
Pericardial effusions - neoplastic, idiopathic

Question 2

Pathophysiology - DMVD

Answer 2

Distorition of valve leaflets due to a degenerative change –> insufficiency –> necessitates increased ventricular SV –> ventricular dilatation –> exacerbates leakage –> worsened by vasoconstriction

Question 3

Define DMVD

Answer 3

Degenerative (acquired) mitral valve disease

Question 4

Equation for total SV

Answer 4

Total V = Forward SV + regurgitant SV

Question 5

Signalment - DMVD

Answer 5

AGE: typically older

BREED: small (<25kg), CKCS, Terriers, Poodles, Dachshund, Chihuahua

SEX: affects males earlier in some breeds (CKCS)

Question 6

Clinical signs - DMVD - 4

Answer 6

Signs of left sided failure - cough, dyspnoea, exercise intolerance

Signs of collapse - dysrhythmias

Sudden death (rare) - arrhythmia, left atrial tear, ruptured chord

Signs or right-sided HF - late in disease progression

Question 7

Clinical examination findings - DMVD - and classification of DMVD

Answer 7

Vary according to stage of disease:
MILD (compensated) - left aprical systolic murmur, +/- exercise intolerance, may be otherwise normal

MODERATE (developing failure) - murmur higher grade, dyspnoea, tachycardia, dysrhythmia, crackles/wheezes

SEVERE (overt CHF) - above present and may progress or RCHF), ascites, jugular pulses, hepatomegaly

Dogs in the more advanced stages of disease (although they may not have HF, will have a murmur louder than grade 3/6. They may have elevated HR and lose sinus arrhythmia.

Question 8

What does a left apical systolic murmur suggest?

Answer 8

leak in the valve

Question 9

Diagnostic evaluation - DMVD

Answer 9

Clinical examination

ECG - helpful when a rhythm disturbance is suspected but not necessarily indicated in every case

Radiography- left sided enlargement, when dogs go into HF you see pulmonary congestion and edema

Echocardiography - Doppler for definitive Dx
Blood tests (MR), left sided enlargement

Definitive diagnosis requires demonstration of mitral regurgitation

Question 10

What might you see on a DMVD ECG

Answer 10

Usually normal
May see pattern consistent with hypertrophy (not sensitive or specific)
Rhythm disturbances (rare) - APCs, atrial tachycardia/fibrillation, ventricular rhythm disturbances.

Question 11

Radiographic signs - DMVD

Answer 11

Variable changes as disease progresses
LA enlargement, lateral and DV views
LV enlargement
Bronchial compression
Pulonary venous congestion
Pulmonary oedema
RCHF signs - pleural effusion, ascites, hepatomegaly

Question 12

Echocardiography - DMVD

Answer 12

VALVULAR CHANGES: rough irregular leaflets, prolapse, ruptured chordae tendinae, failure of apposition

CHAMBER ENLARGEMENT: LAE, LV dilatation (diastole)

MYOCARDIAL FUNCTION: alteration of FS.

Question 13

Therapy - MR before CHF

Answer 13

Controversial, weight of evidence doesn’t support initiation of therapy in early disease

Question 14

Therapy - MR after CHF CS onset

Answer 14

Furosemide and pimobendan (QUEST)
Also consider ACEI and spironolactone (in that order since this is the order of best evidence and strongest indication. Thereafter dose according to the most pressing clinical problems identified)

Question 15

Therapy DCM - before CHF

Answer 15

Possible benefit of ACEI

Recent study suggest pimobendan prior to onset of signs delays onset of signs and prolongs survival

Question 16

Thearpy DCM - after CHF signs

Answer 16

Furosemide, ACEI and pimobendan

Consider spironolactone

Question 17

Outline bacterial endocarditis

Answer 17

Rare
= Infection of endocardium, typically valvular
CS: pyrexia (unknown origin), lame, sepsis
Dx: echo, blood culture, changing murmur
Tx: appropriate AB therapy over many weeks
Prognosis: guarded

Question 18

Types of CANINE cardiomyopathy

Answer 18

DILATED: relatively common in dogs, 2nd commonest acquired heart disease

**ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY **

HYPERTROPHIC - v common in cats, v. rare in dogs

RESTRICTIVE

Intermediate/UNCLASSIFIED

Question 19

What is DCM?

Answer 19

= systolic failure of the myocardium with dilatation of the ventricle due to increased end diastolic pressures. May lead to increased end diastolic pressures –> valvular insufficiency secondary to dilatation.

Aetiology unknown

Question 20

Clinical signs - DCM

Answer 20

May be incidental OR occult DCM
Forward failure - intermittent collapse, weakness, sudden death
Backward failure - cough, excercise intolerance, dyspnoea, ascites

Question 21

PE - DCM

Answer 21

Findings variable
Systolic murmur - due to heart dilatation, likely softer than DMVD
Gallop rhythm
Arrhythmia, pulse deficits (more likely than DMVD)
Signs of CHF (dyspnoea, crackles, cough. Ascites, pleural effusion, SC oedema)

Question 22

ECG - DCM - 5

Answer 22

Sinus tachycardia
APCs
AF
VPCs
Paroxysmal ventricular tachycardia

Question 23

Differentiate DCM and DMVD

Answer 23

DCM = normal valve, dilated annulus, valve leakage is secondary problem
DMVD = abnormal valve, normal annulus

Question 24

Signalment and predispositions - DCM

Answer 24

Large breed dogs (>25kg) - unlike DMVD
Breeds: Dovermans, Boxers, Great danes, Cocker Spaniels
Prevalence increases with age (typically 5-10)
Males more frequently affected in some breeds

Question 25

How is a definitive diagnosis of DCM made?

Answer 25

Echocardiography - the 2 key features being dilatation and systolic dysfunction.

Dilated hypokinetic LV (FS% <25%), increased LVID-D and LVID-S. May also see LAE and mitral insufficiency.

Question 26

Name 4 indices of systolic function

Answer 26

Fractional shortening (FS)
Ejection fraction
Systolic time intervals
Doppler tissue imaging

Question 27

What is the diagnostic test of choice for deciding if a DCM patient is in HF?

Answer 27

Radiography - evidence of left or right-sided congestive heart failure. Also there may be evidence of cardiomegaly - generalised or LVH or LAE.

Question 28

What does the PROTECT study show?

Answer 28

pimobendan administered to dobermans with preclinical DCM delays the onset of CS and prolongs life. There is also evidence to suggest the benefit of ACEI prior to the onset of HF, particularly in certain breeds. Once HF develps, tx is similar to DMVD (i.e Furosemide, pimobendan and ACEI are indicated. Spironolactone may also be beneficial). More likely that cardiac rhythm control will be necessary in these dogs that in those with DMVD.

Question 29

Prognosis - DCM that have gone into HF

Answer 29

very guarded. certain breeds seem to do better (cocker spaniels) than others (dobermans and great danes)

Question 30

What do you do in patient with DCM after the best evidence has been exhausted? 3

Answer 30

• Optimise cardiac rate and rhythm (control rate in AF, control severity of rhythm disturbance in VT)
• Antagonise neurohormonal mechanisms (ACEI, beta-blockers, spironolactone)
• Nutritional support

Question 31

What type of HF is pericardial effusion associated with?

Answer 31

Right sided HF in dogs

Question 32

Main causes - pericardial effusion

Answer 32

Idiopathic pericarditis and neoplasia (equally likely)

[Also (but rarely if ever causing HF) - trauma, hypoproteinaemia, RCHF, FBs, FIP]

Question 33

Name 3 neoplasias that can causes pericardial effusion

Answer 33

Right atrial HSA
Chemodectoma
Mesothelioma

Question 34

Pathophysiology - pericardial effusion

Answer 34

Increased pressure in pericardial sac –> compromised diastolic function –> right side more affected (thin wall) –> RCHF. If acute in onset may see signs of syncope and forward failure (inadequate output) or backward failure (signs of congestion).

Question 35

Signalment and predisposition - pericardial effusion

Answer 35

Middle aged -older dogs

Predisposition: GSDs, St. Bernards (earlier).

Question 36

What is the most common cause of exclusively right sided HF in dogs?

Answer 36

pericardial effusion

Question 37

What do DCM and DMVD cause?

Answer 37

Left-sided heart failure

Question 38

What might be signs on clinical exam of fluid around the heart? 2

Answer 38

Muffled heart sounds
Pulsus paradoxus (decreasing femoral pulse strength on inspiration)

Question 39

T/F: there is always a murmur associated with pericardial effusion.

Answer 39

False - in pericardial effusion there is no mummur and for this reason this disease is often under-recognised as the cause of sudden ascites.

Question 40

What is the most effective method for detecting fluid around the heart within the pericardial sac?

Answer 40

ECHO. May also help determine the underlying cause. Where a mass is seen, you can probably confirm the cause is neoplasia (but you cannot rule out the possibility of neoplasia on the basis of a negative scan). Detection of a mass is associated with a worse outcome.

May show evidence of cardiac tamponade (collapse of RA and RV during systole).

Might indicate best site for pericardiocentesis

Question 41

What do thoracic radiographs show in pericardial effusion?

Answer 41

evidence of an enlarged cardiac silhouette but don’t allow you to discriminate fluid from soft tissue (thus other causes of silhouette enlargement cannot be ruled out)

Question 42

ECG - pericardial effusion

Answer 42

No definitive evidence of an effusion, may show decreased QRS complex amplitude and possible beat-to-beat alternation in the QRS amplitude (electrical alternans).

Question 43

Treatment - pericardial effusion

Answer 43

No drugs indicated (due to limited CO and compromised diastolic function)
Best option = pericardiocentesis

Question 44

Method - pericardiocentesis

Answer 44

Usually LA and/or sedation
Right side of thorax
Ultrasound guidance
Don’t use acepromazine (vasodilation may be detrimental in a dog with limited CO).

Question 45

Prognosis - pericaridal effusion

Answer 45

Depends on underlying cause
Idiopathic - cured by drainage, tends to recur
Neoplastic - poor prognosis, especially RA HSA, chemodectomas may be slow growing
FBs or infectious causes -may be manageable with surgery.

Question 46

What do you do in cases of pericardiocentesis where the effusion recurs?

Answer 46

Perform a pericardiectomy or a pericardiotomy (i.e. remove the pericardium or creating a hole in the pericardium to allow fluid to drain into the pleural space where it can usually be absorbed more effectively).