Feline Myocardial Disease Flashcards
List the 4 primary feline myocardial diseases
- Hypertrophic cardiomyopathy
- Restrictive cardiomyopathy
- Dilated cardiomyopathy
- Arrhythmogenic right ventricular cardiomyopathy
List the 3 secondary feline myocardial diseases
- Hypertensive cardiomyopathy
- Hyperthyroid cardiomyopathy
- Cardiomyopathy associated with other systemic disease e.g. renal failure, acromegaly (normally associated with insulin resistant diabetes mellitus) etc
Which conditions need to be excluded in cats to diagnosed cardiomyopathies?
Conditions that will cause a pressure overload on the left ventricle
e.g. systemic hypertension: need to measure BP and look for primary causes of this e.g., hyperthyroidism, chronic kidney disease
Describe the features of feline systemic hypertension
- May result in secondary cardiomyopathy
- Heart murmurs frequently identified
- Need to screen for underlying systemic disease (Haematology, Biochemistry, TT4 etc.)
- Vital to recognise prior to ocular / CNS complications.
Feline hypertrophic cardiomyopathy is characterised by?
A marked concentric hypertrophy of the left ventricle
Diastolic dysfunction - difficulty in filling
How is feline hypertrophic cardiomyopathy diagnosed?
A diagnosis of exclusion
Rule out other potential causes of concentric hypertrophy
List some other potential causes of concentric hypertrophy in cats
- Aortic stenosis
- Systemic hypertension
- Hyperthyroidism
- Chronic renal failure
- Acromegaly (+/- diabetes mellitus)
What happens if cats with hypertrophic cardiomyopathy become very stressed or tachycardic?
Can push them into left sided congestive heart failure and
can be known as flash pulmonary oedema
How do cats with preclinical hypertrophic cardiomyopathy present
- Identified because of detection of an asymptomatic heart murmur most commonly
- Sometimes, arrhythmias or diastolic gallops detected on physical examination.
- Blood samples: Increased NT-pro-BNP (ref. <100 pmol/L) and / or Troponin I (cardiac biomarkers)
How do cats with clinical hypertrophic cardiomyopathy present
- Dyspnoea or tachypnoea because of congestive heart failure (pulmonary oedema and / or pleural effusion
- Feline arterial thrombo-embolism (FATE)
- Syncope / odd episodes (seem frightened or painful)
- Periods of open-mouth panting
- Sudden death
What are the clinical signs/findings in feline arterial thrombo-embolism? in cats with HCM?
- Purple looking pads
- Off back legs
- Painful
- PM: saddle thrombus in the aorta going to the external iliac arteries
- Severe underlying heart disease with poor prognosis
What drugs should be given to a cat presenting with clinical HCM?
Give oxygen
Butorphanol sedation
Furosemide IV
Describe how echocardiography is used to diagnose feline HCM?
Demonstration of a concentric hypertrophy (with wall measurements ≥6 mm in diastole) is sufficient for the diagnosis, after active exclusion of underlying disease and systemic hypertension
- Aortic to left atrial ratio is more than 1.5
- Left atrium is increasing in size – risks = heart failure and thromboembolism
Describe how feline hypertrophic cardiomyopathy is classified/staged
A = predisposed
B1 (low risk) = sub clinical - normal/mild atrial enlargement
B2 (higher risk) = subclinical - moderate/severe atrial enlargement
C = Current/previous CHF
D = refractory CHF
Define refractory CHF
Also known as end stage or advanced heart failure - heart failure symptoms persist despite taking prescribed medications
Describe the appearance of feline HCM on radiographs
- Typically have pulmonary oedema
- Air bronchograms: alveolar interstitial pattern
- Effacement of the cardiac silhouette
- Resolving of the pulmonary oedema allows for a better view of the cardiac silhouette
- Typically no cardiomegaly due to concentric hypertrophy
Describe the diastolic ‘gallops’ heard in feline heart disease
The detection of third (S3) and fourth heart (S4) sounds
Abnormally detected in cats and dogs
S3 = rapid deceleration of blood in LV
S4 = LV filling associated with atrial contraction
Describe treatment of feline HCM if the patient is in heart failure
- Diuretics (furosemide) (IV if it can be administered without stress if severe dyspnoea)
- Venodilator if life-threatening pulmonary oedema.
- ACE inhibitor (ACE inhibitors are not licensed for the treatment of feline CHF. However benazepril is licensed in cats (for CKD)
- Angiotensin II receptor blocker (Telmisartan; Semintra) is an alternative (licensed for feline CKD)
Which drugs can be used to prevent thromboembolism in cats with HCM?
Clopidogrel
Aspirin
Which drugs may be used in the asymptomatic cat with HCM?
Beta blocker: reduce severity of dynamic LVOT obstruction, slow HR (improves diastolic function)
ACE-I
Diltiazem: positive inotrope (improves relaxation)
- No evidence available that any drug slows down progression into CHF
Which group of drugs cannot be used in cats with CHF?
Beta blockers
What must be excluded from cats to diagnose suspected dilated cardiomyopathy?
Taurine deficiency - assess response to taurine supplementation
How is feline dilated cardiomyopathy treated?
- Warmth
- Humidified oxygen
- Drain significant pleural effusions
- Furosemide
- ACE inhibitors
- Pimobendan (unlicensed for cats)
- Taurine: even if not deficient
Describe the two forms of restrictive cardiomyopathy
Myocardial form – associated with fibrosis
Endomyocardial form – endocardial thickening
Describe the characteristics of restrictive cardiomyopathy
- Relatively normal LV wall measurements
- Relatively normal LV chamber dimensions
- Relatively normal LV systolic function
- Usually marked LA enlargement
- Diastolic function: restrictive physiology
What is non-specific cardiomyopathy?
Features of more than one form of cardiomyopathy
e.g. Systolic dysfunction with abnormal LV filling
Describe arrhythmogenic right ventricular cardiomyopathy in cats
- Fatty replacement of myocardium, initially around RVOT. Usually marked dilatation of the right heart.
- May show ventricular arrhythmias or conduction disturbances but most commonly, affected cats present with R-CHF (e.g. ascites).
- Some cats have 3rd degree AV block.
What are the key considerations when presented with a dyspnoeic cat due to pulmonary oedema
- These cats are very fragile and seriously ill
- Do not stress
- They will not tolerate echocardiography, radiography and ECG
- Must be stabilised prior to further investigation
Describe how to stabilise a dyspnoeic cat
- Oxygen therapy (humidified)
- Reduce anxiety (e.g. butorphanol)
- Calm, gentle handling & environment
- Delay investigations until more stable.
- Intravenous furosemide (IM if very stressed)
- Drain pleural effusions
Describe using a NT pro-BNP SNAP test
- Immediate results, so very useful in a dyspnoeic patient to identify a cardiac cause or to exclude it.
- Can also run the test on pleural effusion post-Thoracocentesis
- Not useful to screen healthy cats for HCM (need values of >200pmol/L for “Abnormal” on the SNAP test).
Describe treatment of stages A and B1 of feline cardiomyopathy
No treatments indicated
Describe treatment of stage B2 of feline cardiomyopathy
Clopidogrel if at risk of FATE
Describe treatment of stages C and D of feline cardiomyopathy
- Diuretics: Furosemide
- Consider pimobendan
- ACE-I once recovered from acute decompensation
- Consider spironolactone
