Feline cardiomyopathy Flashcards
Definition of cardiomyopathy
A muscle disease associated with cardiac dysfunction
Can be primary or secondary
Classifications of feline cardiomyopathies
Hypertrophic cardiomyopathy (HCM) - left ventricle walls thickened
Restrictive cardiomyopathy (RCM) - dilated atrium
Dilated cardiomyopathy (DCM)
Arrhythmogenic right ventricle cardiomyopathy (ARVC)
Prevalence of different cardiomyopathies in cats
HCM: 58-77%
RCM: 15-21%
DCM: 4.4-10%
ARVC: 0.5-1%
Hypertrophic cardiomyopathy
Unexplained increase in left ventricular thickness
Myocardial disease charaterised by LV hypertrophy in the abscence of abnormal loading conditions
Very similar clinical and pathological features to HCM in humans
Aetiology of HCM
Familial in several breeds (Maine coon, Ragdoll, DSH, Sphynx)
In most cases the genetic mutation is unknown
Diagnosis of HCM
Echocardiography
- LV wall thickness (diastole) should be more than/equal to 6.0mm
HCM phenocopies
Unexplained increase in left ventricular thickness
Need to screen for the other diseases that look like HCM but aren’t
Thick walls could instead be oedema, cell infiltration etc.
Diseases, aside from HCM, that can cause pressure overload in the left ventricle - myocardial hypertrophy
Aortic stenosis (more resistance leaving the left ventricle)
Systemic hypertension (very important in cats)
Acromegaly
Hypersomatotropism
Much more prevalent in the UK than previously thought
Frequently presented with diabetes mellitus, but not always
However still much more rare than HCM
Pseudohypertrophy
If the patient is dehydrated the ventricular walls look thick but they aren’t
You would also expect the atrium to look small
Systolic anterior motion of the mitral valve (SAM)
Seen in both HCM (commonly but not pathognomic) and some HCM phenocopies
During systole the mitral valve should remain in place
Common cause of heart murmurs in cats and humans
Obstruction to the blood flow so the blood will flow faster to get around it
Mitral regurgitation
Mitral valve is dragged towards the septum
In HCM the ventricles are also hypercontractile
Transient myocardial thickening
Presents with CHF and looks like HCM
However undergoes reverse remodelling back to normal
Typically young cats, usually that have recently undergone a stressful event
Excellent prognosis
Young cats with ‘HCM’ and heart failure +/- antecedent event > give it a try > treat!!
Causes of thickened ventricular walls on echo (cats)
Myocardial hypertrophy
Pseudohypertrophy
Accumulation of cells or fluid
Causes of myocardial hypertrophy
Hyperthyroidism
Acromegaly
HCM
Aortic stenosis
Systemic hypertension
Cause of pseudohypertrophy
Dehydration
Cause of accumulation of cells or fluid in ventricular walls
Lymphoma
TMT
Mean age of diagnosis of HCM
5.9-6.5yrs
What % of cats with HCM develop serious complications?
Around 30%
- congestive heart failure
- aortic thromboembolism
- Sudden cardiac death
What % of cats with HCM have normal heart sounds?
Up to 69%
Diagnosis of HCM
Ausculation of heart
ECG
Echo
T4 test (hyperthyroidism)
Blood pressure (systemic hypertension)
Echocardiography of RCM
Normal LV wall thickness
LA or biatrial enlargement
Pathology of RCM
Bi-atrial dilation
Normal LV wall thickness
Normal LV systolic function
Restrictive LV filling pattern
Aetiology of RCM
Infiltration of eosinophils > activated eosinophils > cardiac damage
□ Unlikely in cats
Viral induced or immune-mediated
□ Conflicting results
® Histopath evidence of myocarditis and panleukopaenia virus DNA
® Histopath no endocarditis or endomyocarditis and no viral DNA
® 35% of RCM cats had infectious diseases
Familial > sarcomere mutations
□ No genetic studies in cats so far
Signalment of RCM
Mean age at diagnosis 7-10 years
> > DSH cats, but also in Birmans, Siamese, and Persians
Physical examination of cats with RCM
Systolic heart murmur (36-77%)
Gallop (31%)
Arrythmias (23%)
Diagnosis of RCM
Echocardiography
- myocardial RCM
- Endomyocardial RCM
Dilated cardiomyopathy in cats
Characterised by LV dilation and systolic dysfunction
Classically associated with taurine deficiency
§ Rare after taurine levels in commercial cat food were corrected
§ Cats on unbalanced diets (e.g. vegetarian, dog food)
Prognosis of DCM in cats
12-49 days MST in DCM non-responsive to taurine > longer survival with pimobendan
Diagnosis of DCM in cats
Echocardiography
- normal-reduced LV wall thickness
- LV systolic dysfunction
- LA dilation
Arrhythmogenic RV cardiomyopathy (ARVC) in cats
Characterised by RV fibro-fatty infiltration
§ Severely dilated RV
§ Thin RV wall
§ Can also affect LV
Differential diagnosis for ARVC in cats
Tricuspid dysplasia
Diagnosis of ARVC in cats
Echocardiography
- RA and RV dilation
- Arrhythmias and right-sided CHF
Echo and ECG
- malignant ventricular arrhythmias are common
Stages of feline cardiomyopathy
A: predisposed
B1: low risk, subclinical, normal/mild atrial enlargement
B2: high risk, subclinical, moderate/severe atrial enlargement
C: CHF/ATE
D: refractory CHF
Median survial time of cats with asymptomatic HCM
May have >10yrs
Risk factors for HCM in cats
LA dilation
‘Smoke’
LA thrombus
Treatment of stage B2 cardiomyopathy in cats
Clopidogrel
Treatment of Stage C cardiomyopathy in cats
Sedation
No stress
O2
Furosemide
Antithrombotics
- heparin
- clopidogrel
Analgesia
- methadone
- fentanyl
What is the most common heart disease in cats?
HCM
