Feline Myocardial disease

Question 1

What are primary feline myocardial diseases?

Answer 1

• Hypertrophic cardiomyopathy (HCM)
  -With or without LV obstruction
• Restrictive cardiomyopathy (RCM)
• Non-specific cardiomyopathy (NS-CM)
• Dilated cardiomyopathy (DCM)
• Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Question 2

What are secondary feline myocardial diseases?

Answer 2

• Hypertensive cardiomyopathy
• Hyperthyroid cardiomyopathy
• Cardiomyopathy associated with:
  -acromegaly
  -azotaemia
  -diabetes mellitus etc.
• Transient myocardial thickening
  -Young cats, follows stressful incident.
  -Reversible cardiomyopathy

Question 3

What can feline systemic hypertension lead to?

Answer 3

Secondary cardiomyopathy

Question 4

What should be ruled out that may cause concentric hypertrophy before diagnosing feline hypertrophic cardiomyopathy?

Answer 4

 Aortic stenosis
 Systemic hypertension
 Hyperthyroidism
 Chronic renal failure
 Acromegaly (+/- diabetes mellitus)
 Transient myocardial thickening

Question 5

What’s the most common cause of a heart murmur in cats?

Answer 5

• Hypertrophic cardiomyopathy

Question 6

What is HCM in cats?

Answer 6

• familial disease reported in Persians, Ragdolls, Maine coons, Sphinxes, American shorthairs, British shorthairs, Norwegian Forest cats, etc.
• Autosomal dominant trait
• Maine coons & Ragdolls; mutations detected in genes encoding Myosin binding protein C, Sphinx: ALMS1 gene (genetic tests available)

Question 7

How do cats present with preclinical HCM?
What biomarkers are increased?

Answer 7

• asymptomatic heart murmur
• Sometimes arrhythmias, diastolic gallops on physical exam
• increased NT-pro-BNP +/or Troponin I (cardiac biomarkers)

Question 8

How do cats present with clinical HCM?

Answer 8

• Dyspnoea or tachypnoea because of congestive heart failure (pulmonary oedema and / or pleural effusion
• Feline arterial thrombo-embolism (FATE)
• Syncope / odd episodes
• Periods of open-mouth panting
• Sudden death

Question 9

What is seen with Feline arterial thromboembolism

Answer 9

• V painful
• more painful than RTAs
• Loss of hindlegs - external iliacs usually embolised (saddle thrombus)

Question 10

How do you classify feline HCM?

Answer 10

1. A = predisposed
2. B1 = subclinical - normal/mild atrial enlargement
3. B2 = subclinical - moderate/severe atrial enlargement
4. C = current / previous CHF / Arterial thromboembolism
5. D = Refractory CHF

Question 11

What are heart sounds?

Answer 11

• S1 = closure of AV valve
• S2 = Closure of semilunar valves
  abnormal
• S3 = rapid deceleration of blood in LV
• S4 = LV filling associated with atrial contraction

Question 12

How would you treat a cat with heart failiure? (HCM)

Answer 12

• Diuretics - furosemide
• Venodilators - GTN (if life-threatening pulmonary oedema
• ACE inhibitor (not licenced - but Benazepril is)
• Angiotensin II receptor blocker - Telmisartan
• Clopidogrel = prevent thromboembolism

Question 13

What could you do with asymptomatic cats?

Answer 13

• Beta blocker / Ca channel blockers
• no strong evidence of improvement
• DONT give beta blocker if CHF

Question 14

If dilated cardiomyopathy, what must be excluded in cats? Tx?

Answer 14

• Taurine deficiency
• Tx = pimobendan (+ve inotrope), warmth, humidified o2, drain effusions, furosemide

Question 15

What are the 2 forms of restrictive cardiomyopathy? What are they characterised by?

Answer 15

• Two forms:
• Myocardial form
• Endomyocardial form
• Characterised by:
  – Relatively normal LV wall measurements
  – Relatively normal LV chamber dimensions
  – Relatively normal LV systolic function
  – Usually marked LA enlargement
  – Diastolic function: restrictive physiology

Question 16

What is non-specific cardiomyopathy?

Answer 16

• Features of more than one form of cardiomyopathy
• e.g. Systolic dysfunction with abnormal LV filling
• Describe the abnormalities
  – This example: 4 chamber dilatation, impaired LV systolic function, “smoke” in LA, small pericardial effusion (due to CHF)

Question 17

What is arrhythmogenic RV cardiomyopathy?

Answer 17

• 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

Question 18

What should be done to cats with dyspnoea due to life threatening pulmonary oedema?

Answer 18

• DO NOT STRESS!
• Provide oxygen, without additional stress (oxygen cage in quiet, dark room)
• Administer furosemide (IV if an IV catheter can be placed without stress; otherwise IM)
• Nitroglycerine topically (Percutol) (if available)
• Sedation if cat very anxious (opiates e.g. methadone).
• Only after the cat is stabilised should you undertake diagnostic tests

Question 19

What should be done to dyspnoeic cats with CHF?

Answer 19

• Oxygen therapy (humidified)
• Reduce anxiety (e.g. butorphanol)
• Calm, gentle handling & environment
• Delay investigations until more stable.
• IV Furosemide
• Drain pleural effusions

Question 20

How can you screen cats for HCM?

Answer 20

• Annual Echo - pedigrees
• NT-pro-BNP SNAP test for clinical cases