Advanced CV disease of dogs Flashcards
What are the 3 main types of acquired CV disease that occur in dogs?
DMVD - endocardiosis or myxomatous valve disease
DCM
Pericardial effusions - neoplastic, idiopathic
Pathophysiology - DMVD
Distorition of valve leaflets due to a degenerative change –> insufficiency –> necessitates increased ventricular SV –> ventricular dilatation –> exacerbates leakage –> worsened by vasoconstriction
Define DMVD
Degenerative (acquired) mitral valve disease
Equation for total SV
Total V = Forward SV + regurgitant SV
Signalment - DMVD
AGE: typically older
BREED: small (<25kg), CKCS, Terriers, Poodles, Dachshund, Chihuahua
SEX: affects males earlier in some breeds (CKCS)
Clinical signs - DMVD - 4
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
Clinical examination findings - DMVD - and classification of DMVD
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.
What does a left apical systolic murmur suggest?
leak in the valve
Diagnostic evaluation - DMVD
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
What might you see on a DMVD ECG
Usually normal
May see pattern consistent with hypertrophy (not sensitive or specific)
Rhythm disturbances (rare) - APCs, atrial tachycardia/fibrillation, ventricular rhythm disturbances.
Radiographic signs - DMVD
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
Echocardiography - DMVD
VALVULAR CHANGES: rough irregular leaflets, prolapse, ruptured chordae tendinae, failure of apposition
CHAMBER ENLARGEMENT: LAE, LV dilatation (diastole)
MYOCARDIAL FUNCTION: alteration of FS.
Therapy - MR before CHF
Controversial, weight of evidence doesn’t support initiation of therapy in early disease
Therapy - MR after CHF CS onset
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)
Therapy DCM - before CHF
Possible benefit of ACEI
Recent study suggest pimobendan prior to onset of signs delays onset of signs and prolongs survival
Thearpy DCM - after CHF signs
Furosemide, ACEI and pimobendan
Consider spironolactone
Outline bacterial endocarditis
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
Types of CANINE cardiomyopathy
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
What is DCM?
= 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
Clinical signs - DCM
May be incidental OR occult DCM
Forward failure - intermittent collapse, weakness, sudden death
Backward failure - cough, excercise intolerance, dyspnoea, ascites
PE - DCM
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)
ECG - DCM - 5
Sinus tachycardia APCs AF VPCs Paroxysmal ventricular tachycardia
Differentiate DCM and DMVD
DCM = normal valve, dilated annulus, valve leakage is secondary problem DMVD = abnormal valve, normal annulus
Signalment and predispositions - DCM
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
How is a definitive diagnosis of DCM made?
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.
Name 4 indices of systolic function
Fractional shortening (FS)
Ejection fraction
Systolic time intervals
Doppler tissue imaging
What is the diagnostic test of choice for deciding if a DCM patient is in HF?
Radiography - evidence of left or right-sided congestive heart failure. Also there may be evidence of cardiomegaly - generalised or LVH or LAE.
What does the PROTECT study show?
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.
Prognosis - DCM that have gone into HF
very guarded. certain breeds seem to do better (cocker spaniels) than others (dobermans and great danes)
What do you do in patient with DCM after the best evidence has been exhausted? 3
- 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
What type of HF is pericardial effusion associated with?
Right sided HF in dogs
Main causes - pericardial effusion
Idiopathic pericarditis and neoplasia (equally likely)
[Also (but rarely if ever causing HF) - trauma, hypoproteinaemia, RCHF, FBs, FIP]
Name 3 neoplasias that can causes pericardial effusion
Right atrial HSA
Chemodectoma
Mesothelioma
Pathophysiology - pericardial effusion
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).
Signalment and predisposition - pericardial effusion
Middle aged -older dogs
Predisposition: GSDs, St. Bernards (earlier).
What is the most common cause of exclusively right sided HF in dogs?
pericardial effusion
What do DCM and DMVD cause?
Left-sided heart failure
What might be signs on clinical exam of fluid around the heart? 2
Muffled heart sounds Pulsus paradoxus (decreasing femoral pulse strength on inspiration)
T/F: there is always a murmur associated with pericardial effusion.
False - in pericardial effusion there is no mummur and for this reason this disease is often under-recognised as the cause of sudden ascites.
What is the most effective method for detecting fluid around the heart within the pericardial sac?
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
What do thoracic radiographs show in pericardial effusion?
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)
ECG - pericardial effusion
No definitive evidence of an effusion, may show decreased QRS complex amplitude and possible beat-to-beat alternation in the QRS amplitude (electrical alternans).
Treatment - pericardial effusion
No drugs indicated (due to limited CO and compromised diastolic function)
Best option = pericardiocentesis
Method - pericardiocentesis
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).
Prognosis - pericaridal effusion
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.
What do you do in cases of pericardiocentesis where the effusion recurs?
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).
