Diseases of the cardiovascular system III Flashcards
What is a cardiomyopathy?
Disease of the myocardium
What is a dilated cardiomyopathy?
- Common in dogs
- Characterised by ventricular dilation and thin hypomotile ventricular wall
What is hypertrophic cardiomyopathy?
- Common in cats
- characterised by hypertrophy of the ventricular wall and a restricted ventricular lumen
What is restrictive cardiomyopathy?
Characterised by a stiff ventrciular wall and marked dilation of the atrium feeding the ventricle
What is arrhythmogenic right ventricular cardiomyopathy?
- Boxers
- Fibrofatty infiltrate that preferentially affects the right ventricle
What diseases may be able to mimic a dilated cardiomyopathy?
- Taurine deficiency in cats
- L-carnitine deficiency in boxers
- Toxins
- Grain-free diets
- Lamb based diets
What breeds are predisposed to dilated cardiomyopathy?
- Medium to large breed dogs, e.g dobermans, great danes…
- Doberman pinschers are autosomal dominant (splice-site mutation)
- Great danes- appears to be familial, male dogs are over-represented suggesting X-linked inheritance
What is the clinical presentation of dilated cardiomyopathy?
Adult onset disease
* asympomatic/ occult phase = usually progressive
* Symptomatic phase = coughing, dyspnoea, ascites
What are the common physical findings of the occult phase of dilated cardiomyopathy?
- soft sytolic heart murmur
- Irregular heart rhythm
- Pulse deficits
What are the occasional clinical signs of the occult phase of dilated cardiomyopathy?
- Diastolic gallop
- Weak pulse
- Jugular vein distension
- Decreased intensity of heart sounds
What are the overt clinical signs of dilated cardiomyopathy?
- Moderate intensity
- Irregular heart rhythm
- Pulse deficits
- Tachypnoea
- Dyspnoea
- Weakness
- Increased bronchovesicular sounds
What are the less common clinical signs of dilated cardiomyopathy?
- Jugular vein distension
- Ascites
- Hepatomegaly
- Pale MM, hypothermia
What is the only reliable way to diagnose DCM?
Echocardiography
What echocardiography is recommended for adult dogs of at risk breeds (for DCM) ?
Annual two dimensional and M-Mode echocardiography
-ECG for signs of LV and LA enlargement
What are the cardiac biomarkers for dilated cardiomyopathy?
Troponin
What is hypertrophic cardiomyopathy?
primary myocardial disease that results in thickening of the left ventricular walls
What is the prevalence of HCM in the feline population?
Up to 20% in the general feline population
What is the relationship between Hypertrophic cardiomyopathy and Maine Coons?
- Causative mutation in A31P in the cardiac myosin Binding Protein C sarcomeric gene for inherited HCM, with autosomal domiannt inheritance
What is the relationship between hypertrophic cardiomyopathy and ragdoll cats?
- Substitution mutation in MYBPC3 associated with HCM was associated in 2007
What are the clinical signs of HCM in cats?
- Often asymptomatic- murmur or gallop is picked up at routinee examination
- Heart murmurs can be absent in cats with HCM and heart failure
- Best heard over the left apex or cranial sternum- often dynamic
What are the cliniical signs of congestive heart failure?
- Anorexia, Lethargy, Dyspnoea, Syncope, Pleural effusion/ pulmonary oedema
- Feline aortic thromboembolism
How might you diagnose Congestive Heart Disease?
Evaluate and test for diseases that cause secondary hypertrophy
* Important to do so before making a diagnosis
What is the phenotype for echocardiography for felien HCM?
- Papillary muscle hypertrophy
- Increased LV wall thickness
- Systolic anterior motion of the mitral valve
- Left atrial enlargement
- Spontaneous echo contrast
What does a spontaneous echo contrast look like?
‘smoke sign’
How might you treat congestive heart failure?
Beta blockers or calcium channel antagonists - act as negative chronotropes and negative inotropes to improve diastolic filling
* Can be controversial if SAM present – sleep more effective than beta-blockade and diltiazem has
questionable long term effect on survival
What is restrictive cardiomyopathy?
Second most common primary cardiomyopathy in the cat
» Characterised by a diastolic dysfunction, with impaired ventricular
filling due to increased myocardial stiffness (reduced ventricular
compliance
What are the clinical signs of restrictive cardiomyopathy?
most cats will present in CHF
* Dyspnoea (89%), followed by non-specific signs (lethargy,
weakness, hypothermia, anorexia), ascites (14%), and
paresis/paralysis related to ATE (6%)) * Heart murmur (81%) (left apical systolic in 77% of murmurs) and
gallop rhythm (31%) of RCM cats
What is Arrhythmogenic Right ventricular cardiomyopathy?
» AKA Box cardiomyopathy (but Boxers can also develop DCM!)
» Inherited as an autosomal dominant trait, variable penetrance
» Most commonly characterised by ventricular arrhythmias,
syncope, and sudden death – but can also be asymptomatic
What are the clinical signs and prognosis of Arrhythmogenic right ventrciular cardiomyopathy?
- 1) asymptomatic dogs with ventricular tachyarrhythmia
- 2) dogs with normal heart size and LV function, but with syncope or
weakness from paroxysmal or sustained ventricular tachycardia - 3) Boxers with poor myocardial function and CHF, as well as ventricular
arrhythmias. The prognosis is especially poor in the last category.
What is the histology of Arrhythmogenic right ventricular cardiomyopathy?
multifocal myocyte vacuolisation, myocyte loss, and significant fatty infiltration
What is the diagnosis for arrhythmogenic right ventrciular cardiomyopathy?
can have normal physical exam, or; tachyarrhythmia, pulse deficits, systolic murmur –may require 24-hour Holter monitor * Note: many Boxers have a soft basilar systolic murmur due to SAS or may be physiological and NOT necessarily due to ARVC
* Likely to be multiple factors that may influence which dogs develop overt clinical signs of the disease
How might you treat arrhythmogenic right ventricular cardiomyopathy?
- Sotalol (β-blocker) 1.5-3.5 mg/kg PO q 12hr, or mexiletine (VG Na+
blocker) 5-6 mg/kg PO q 8hr * +/- fish oils (780 mg EPA and 497 mg DHA PO per day)
What is Myxomatous Mitral Valve Disease?
a condition that causes the mitral valve leaflets to become loose and floppy, which can lead to blood leaking backward into the heart or lungs
What breeds are predisposed to MMVD?
- Prevalence higher in small breed dogs <20 kg (CKCS,
Chihuahua, Dachshund, Poodle, Pomeranian, Papillons etc.) * Large breeds can be affected, usually more severe and
progresses quickly
What valve does MMVD primarily effect?
» Primarily affects the left AV valve but 30% of dogs have an
affected tricuspid valve
» Cause remains unknown, however there is an inherited
component in some breeds. Severity may also have a
genetic component
What is the pathophysiology of MMVD?
- Deformation of valve leaflets (expansion of ECM – extra
cellular matrix - with proteoglycans and GAGs, fibrosis,
degradation of endothelium) * Regurgitation of blood into LA - Increased cardiac workload on LV due to volume overload
- Eccentric hypertrophy of LV
- Severe MR > CHF
What are the differentials for MMVD?
- Dilated cardiomyopathy
- Bacterial endocarditis of mitral valve
- Previously undetected congenital heart disease
(e.g. mitral valve dysplasia, or PDA)
What are the diagnostics for MMVD?
- Ausculatation
- Blood Pressure
- Thoracic radiography
How might you potentially treat MMVD?
Depends on the stage
* Stage B2: Murmur intensity ≥ 3/6,
remodelling of LA and LV, breed adjusted
VHS > 10.5
* If echo is not available then VHS > 11.7,
serially increasing VHS, VLAS > 3
What is the ratio for MMVD?
LA:Ao ratio ≥ 1.6
