Cardiology: Feline Myocardial Disease

Question 1

What are primary myocardial disease of cats?

Answer 1

• Hypertrophic cardiomyopathy with or without LV obstruction
• Restrictive cardiomyopathy
• Cardiomyopathy of non-specific phenotype
• Dilated cardiomyopathy
• Arrhythmogenic right ventricular cardiomyopathy

Question 2

What secondary myocardial disease can affect cats?

Answer 2

• Hypetensive cardiomyopathy
• Hyperthyroid cardiomyopathy
• Cardiomyopathy associated with other systemic disease- eg renal failure

Question 3

How are feline cardiomyopathies staged?

Answer 3

• A- predisposed
• B1 (low risk)- subclinical, normal/mild atrial enlargment
• B2 (higher risk)- moderate/severe atrial enlargment
• C- current/previous CHF/ATE
• D- refractory CHF

ATE= aortic thromboembolism

Question 4

What are the clinical signs of feline cardiomyopathy?

Answer 4

• May be none
• Arrhythmia, gallop sound
• Affected cats may show left sided CHF- acute alveolar flooding
• Stasis of blood flow in the dilated LA may result in thrombus formation/thromboembolism

Question 5

How can HCM cause a left atypical systolic murmur?

Answer 5

Left Apical Systolic Murmur
* Turbulent blood flow in the left ventricular outflow (LVOT) tract as it accelerates around basal septal bulge
* The increased flow may result in anterior mitral valve leaflet to be sucked into LVOT- systolic anterior motion
* SAM and narrowing of the LVOT and mitral regurgitation may result

Hypertropic with dynamic left ventricular outflow tract obstruction

Question 6

How can HCM profuce right sternal border murmurs?
How can they be iatrogenic?

Answer 6

• Septal hypertrophy may cause turbulence

Iatrogenic from pressing your stethoscope too hard on the feline chest wall

Question 7

When may S3 and S4 be heard with HCM?

Answer 7

• S3 (rapid ventricle filling) may be detected if the LV is stiff or increased pressure
• S4 (atrial contraction) may be detected if there is an increased dependence on atrial contraciton- impaired LV relaxation in HCM

Question 8

How is HCM characterised?

Answer 8

• Marked concentric hypertrophy of the LV
• This is associated with diastolic dysfunction (difficult to fill ventricles)
• If filling pressures increase can cause pulmonary oedema

Question 9

How is HCM diagnosed?

Answer 9

Echocardiography
* Demonstration of concentric hypertrophy is sufficient
* Hypertrophy in cats is usually generalised
* Left atrial enlargment in cats with symptomatic disease or imminent disease

Rule out other potential causes

Question 10

What can thoracic radiographs and ECG show with HCM?

Answer 10

Thoracic radiographs
* no cardiomegaly (concentric)
* Advanced disease- atrial enlargment
* Best method for left sided CHF identification (LA enlarg, pulmonary venous distension, pulmonary infiltrate)

Echocardiography
* Indicated with dysrythmia- may be abnormal with sinus
* Evidence of LV enlargment
* Intraventricular conduction disturbances

Question 11

How is HCM treated?

Answer 11

• CHF- diuretics- furosemide
• Pleural effusion- drained
• ACE inhibitors- not v efficient
• Spironolactone- no evidence
• Asymptomatic HCM- beta blockers
• Clopidogrel- asymptomatic with dilated LA
• Pimobendan- not licensed

Question 12

What drugs can be used to prevent thromboembolism?

Answer 12

• Clopidogrel- anti-platelet
• Aspririn
• Dalteparin- inject dailt
• Factor Xa inhibitors- current study

Question 13

Restrictive Cardiomyopathy

1. What is restrictive cardiomyopathy associated with?
2. What are the common reasons for feline presentation?
3. What are the two forms?
4. What cause the two forms?
5. What is the treatment?

Answer 13

1. Significant diastolic dysfunction with massive left atrial enlargment, LV walls and chambers close
2. Thrombo-embolic complications or pulmonary oedema and pleural effusions
3. Endomyocardial form, myocardial form
4. Endo- consequence of previous endomyocarditis, bands of adhesions crossing LV, myo- unkown
5. Furosemide and ACE inhibitor
   Pimobendan if impaired systolic function with no dynamic outflow tract obstruction

Question 14

1. What previously predisposed to cats with DCM?
2. How is DCM diagnosed?
3. How is it treated?

Answer 14

1. Taurine deficiency
2. Echocardiography
3. Tarine supplement, furosemide and ace inhibitor, positive inotropes

Question 15

What is the pathogenesis of Arrythmogenic right ventricular cardiomyopathy?

Answer 15

Right ventricular myocardium becomes replaced with a fibro-fatty infiltrate

Question 16

What are the major differentials for a dyspnoeic cat?

Answer 16

• Feline Asthma
• Causes of pleural effusions
• Acute pulmonary oedema- left sided heart failure

Question 17

How should a cat in dysponea with heart disease be treated in an emergency?

Answer 17

• Stress must be minimised
• Sedation may be required- opiated useful (butorphanol)
• Supplemental O2 (humidified) provided
• Furosemide IV, if too stressed, IM or SC- monitor resp rate
• Nitroglycerine topically- venodilator effect- alleviates pulmonart oedema

Question 18

After stabilisation of dysponeic cat with heart disease what follows?

Answer 18

• Diagnostic procedures
• Poor systolic function- pimobendan
• Positive inotrope- caution
• Beta clockers- avoided with CHF

Question 19

What are the different potential causes of concentric hypertrophy?

Diagnosis of Feline Hypertrophic Cardiomyopathy

Answer 19

• Aortic stenosis
• Systemic hypertension
• Hyperthyroidism
• Chronic renal failure
• Acromegaly