Feline Cardiomyopathies Flashcards
Name the different types of myocardial disease in the cat
- HCM (HOCM, hypertrophic cardiomyopathy)
- RCM (restrictive cardiomyopathy)
- DCM (dilated cardiomyopathy)
- ARVC (arrhythmogenic right ventricular cardiomyopathy)
- FUCM (feline unclassified cardiomyopathy)
Described mostly by the pathology seen at post-mortem, determined by echocardiography
All treated pretty much the same and all present as heart failure so doesn’t really matter
What is hypertrophic cardiomyopathy?
Inappropriate myocardial hypertrophy of a non-dilated left ventricle, occurring in the absence of an identifiable stimulus –> external diameter of heart appears normal
HCM is a diagnosis of exclusion- what needs to be ruled out?
- Aortic stenosis
- Systemic hypertension (primary, DM, Cushing’s)
- Metabolic disorders capable of inducing hypertrophy (hyperthyroidism, acromegaly)
- Renal disease
What are the two clinical forms of HCM?
Obstructive (42% of cats)
Non-obstructive
Describe the obstructive form of HCM
Dynamic left ventricular outflow tract obstruction develops
Due to abnormal movement of the anterior mitral valve leaflet in systole –> systolic anterior motion of the mitral valve (SAM)
Turbulent blood flow in left ventricular outflow tract
Concurrent eccentric jet of mitral regurgitation along the posterior wall of the left atrium
Describe the steps involved in systolic anterior motion (SAM) of the mitral valve
- Papillary muscle displaced towards the septum
- Mitral valve malalignment
- Narrowed LVOT
What typical features are seen in the feline form of HCM?
- Disproportionate hypertrophy of the septum
- Myofibre disarray/ malalignment
- Arteriosclerosis
Describe the signalment of HCM
- Commonest acquired heart disease in cats
- 3 genetic mutations now discovered- 2 in Maine Coons and 1 in Ragdolls
- Rare in dogs
- Cause unknown but probably genetic
Describe the distribution of left ventricular hypertrophy in HCM
- Very variable
- May encompass the entire ventricle symmetrically or only involve certain regions
- Asymmetrical septal thickening is common
- Limited to portions of the LV wall or PM in some cats
- Can also affect the right ventricle
Why is HCM a diastolic disease?
The ventricle can’t fill properly
Atria are trying to force blood into a non-compliant ventricle
What is the clinical presentation of cats with HCM?
Very variable –> range from asymptomatic cat with a heart murmur to a recumbent, cold, dyspnoeic cat with congestive heart failure
Not always tachycardic
May present with acute onset lameness/ paralysis if thromboembolus formation secondary to heart disease
Sudden death can occur
What can be heard on auscultation of a cat with myocardial disease?
Systolic murmur PMI sternal border
Often dynamic murmur
Gallop sounds with severe HCM - because of trouble with heart filling
Crackles throughout lung fields due to pulmonary oedema
Dull lung and heart sounds due to pleural effusion
Describe the findings on echocardiography with HCM
o LV hypertrophy often asymmetrical
o Basal septum frequently affected
o Hypertrophied, hyperechoic, irregular papillary muscles
o LVH > 6mm (5.5mm, 5mm) in diastole
o 2DE measurements as well as M mode
o LV lumen is usually small
o LA enlargement is variable- mild to severe
o Can have obstructive component (SAM, often occurs prior to severe wall thickening)
If LV loos a bit thick but LA is ok then don’t need to worry about the cat at that time- follow up in 6m-1y to see if LA has changed
Describe dynamic right ventricular outflow tract obstruction
- Less significant than left side – don’t worry too much about it
- Occurs in some cats and leads to a right sternal border murmur
- Exact significance of DRVOFTO is uncertain but it does occur in higher frequency in those cats with significant left sided disease
- Very rarely severe enough to warrant treatment
- Leads to a right sided sternal murmur
Describe what would be seen in thoracic radiology of a cat with CHF
- Interstitial/ alveolar infiltrate
- Cardiomegaly
- Pulmonary venous congestion
( The majority of cats with CHF will have pulmonary oedema)
