PATHOLOGY - Feline Acquired Cardiac Disease

Question 1

What is hypertrophic cardiomyopathy?

Answer 1

Hypertrophic cardiomyopathy is an inherited generalised disease/dysfunction of the myocardium characterised by increased ventricular wall thickness

Question 2

Which heart chamber is mainly affected by hypertrophic cardiomyopathy?

Answer 2

Left ventricle

Question 3

Which signalement is more prone to hypertrophic cardiomyopathy?

Answer 3

Older (above 9 years) male cats

Question 4

Which two cat breeds are predisposed to hypertrophic cardiomyopathy?

Answer 4

Maine Coon
Ragdolls

Question 5

Why are Maine Coons and Ragdolls predisposed to hypertrophic cardiomyopathy?

Answer 5

Maine Coons and Ragdolls have a mutation in the gene encoding for cardiac myosin-binding protein (MYBPC)

Question 6

Describe the pathophysiology of hypertrophic cardiomyopathy

Answer 6

Hypertrophic cardiomyopathy is generalised dysfunction of the myocardium resulting in diastolic dysfunction, characterised by thickening of the left ventricular wall resulting in reduced compliance and impaired ventricular filling, resulting in a reduction in cardiac output. Due to the reduced ventricular compliance, blood will accumulate in the left atrium and the left atrium will dilate to accommodate this increased blood volume. Eventually this will progress to left-sided congestive heart failure due to the decreased cardiac output and the volume overload in the left atrium which will back up into the pulmonary veins causing congestion, increased hydrostatic pressure and pulmonary oedema. This can also progress to right-sided congestive heart failure as pulmonary hypertension will increase the afterload on the right side of the heart, resulting in pressure overload, concentric hypertrophy of the right ventricle and eventual right-sided congestive heart failure

Question 7

How does atrial dilation increase the risk of arterial thromboembolisms?

Answer 7

Atrial dilation increases the propensity for blood stasis which allows for thombus formation. These thrombi can then travel into the aorta and cause an arterial thromboembolism

Question 8

What are the eight clinical signs of hypertrophic cardiomyopathy?

Answer 8

Asymptomatic
Maybe a murmur
Arrhythmias
Exercise intolerance
Syncope
Signs of left-sided congestive heart failure
Signs of right-sided congestive heart failure
Signs of arterial thromboembolisms

Question 9

Why is there often not a heart murmur associated with hypertrophic cardiomyopathy?

Answer 9

There is not always a heart murmur as the primary issue in hypertrophic cardiomyopathy is related to the myocardial structure and function rather than turbulent blood flow that typically results in a heart murmur

Question 10

What should you always rule out in a cat which presents with a new murmur?

Answer 10

Always rule out systemic hypertension by taking a blood pressure

Question 11

When would you hear a heart murmur with hypertrophic cardiomyopathy?

Answer 11

Hypertrophic cardiomyopathy can alter the structure of the left ventricle resulting in displacement of the mitral valve leaflets towards the left ventricular outflow tract - known as systolic anterior motion (SAM) - which will cause turbulent blood flow and a heart murmur

Question 12

What kind of murmur would you hear with hypertrophic cardiomyopathy?

Answer 12

Left sided basal systolic crescendo-decrescendo mumur

Question 13

How does hypertrophic cardiomyopathy cause arrhythmias?

Answer 13

Arrhythmias can occur due to structural damage to the heart as it enlarges due to hypertrophic cardiomyopathy

Question 14

Which three arrhythmias are seen due to hypertrophic cardiomyopathy?

Answer 14

Atrial fibrillation
Ventricular arrhythmias
Bundle branch blocks

Question 15

What is stage A of hypertrophic cardiomyopathy?

Answer 15

Cats that are at risk of developing hypertrophic cardiomyopathy due to their signalement but have no structural or clinical signs

Question 16

What is stage B1 of hypertrophic cardiomyopathy?

Answer 16

Cats with clear left ventricular thickening (hypertrophy) but no left atrial dilatation

Question 17

What is stage B2 of hypertrophic cardiomyopathy?

Answer 17

Cats with clear left ventricular thickening (hypertrophy) and left atrial dilatation

Question 18

What is stage C of hypertrophic cardiomyopathy?

Answer 18

Cats with clinical signs of congestive heart failure

Question 19

What is stage D of hypertrophic cardiomyopathy?

Answer 19

Cats with congestive heart failure that is refractory to treatment

Question 20

Which two biomarkers can be indicative of hypertrophic cardiomyopathy?

Answer 20

NTproBNP
Cardiac troponin I

Question 21

When are NTproBNP snap tests particularly useful in cats?

Answer 21

If a cat presents with dyspnoea, an NTproBNP snap test can be helpful to differentiate between of the aetiology is cardiac or respiratory in origin

Question 22

What are the key signs of hypertrophic cardiomyopathy on echocardiography?

Answer 22

Thickening of the left ventricle
Dilatation of the left atrium

Question 23

What are the key signs on echocardiography that indicate there is a risk of arterial thromboembolism secondary to hypertrophic cardiomyopathy?

Answer 23

Dilatation of the left atrium
Reduced systolic function of the left atrium
Spontaneous echocontrast (smoke)
Clots in the left atrium

Question 24

What is spontaneous echocontrast (smoke)?

Answer 24

Spontneous echocontrast (smoke) is an echogenic swirling pattern seen in instances of stagnant or low velocity blood flow

Question 25

What is a saddle thrombus?

Answer 25

A saddle thrombus is a thromboembolism at the aortic trifurcation

Question 26

Which forelimb is more commonly affected by arterial thromboembolism in cats?

Answer 26

Right forelimb

Question 27

What are the five clinical signs of a thromboembolism in cats?

Answer 27

Pallor *of affected limb(s)* Cold extremities *of affected limb(s)* Loss of pulse *of affected limb(s)* Limb paralysis *of affected limb(s)* Pain *of affected limb(s)*

Question 28

How would you treat an arterial thromboembolisim in a cat?

Answer 28

Administer clopidogrel/heparin and provide analgesia

Question 29

In cats at risk of hypertrophic cardiomyopathy, what should owners monitor for at home?

Answer 29

An increased resting respiratory rate as this can precede signs of left-sided congestive heart failure, and paradoxical breathing due to the risk of pleural effusion

Question 30

How do you diagnose hypertrophic cardiomyopathy in cats?

Answer 30

Rule out other causes of myocardial thickening *(take blood pressure, measure T4 etc.)* Echocardiography

Question 31

How should you treat stage A hypertrophic cardiomyopathy?

Answer 31

No treatment

Question 32

How should you treat stage B1 hypertrophic cardiomyopathy?

Answer 32

No treatment

Question 33

How should you treat stage B2 hypertrophic cardiomyopathy?

Answer 33

Treat with clopidogrel

Question 34

How should you treat stage C hypertrophic cardiomyopathy?

Answer 34

Treat with clopidogrel and diuretics

Question 35

What is clopidogrel?

Answer 35

Clopidogrel is an antiplatelet drug

Question 36

What is the prognosis for cats with hypertrophic cardiomyopathy exhibiting signs of left-sided congestive heart failure?

Answer 36

Generally a prognosis of one year

Question 37

What is the prognosis for cats with hypertrophic cardiomyopathy with an arterial thromboembolism?

Answer 37

Poor prognosis of around 184 days if they survive the first arterial thromboembolism

Question 38

List three potential causes of secondary hypertrophic cardiomyopathy in cats

Answer 38

Systemic hypertension Hyperthyroidism Transient myocardial thickening (TMT)

Question 39

What are four possible causes of systemic hypertension in cats?

Answer 39

Kidney disease Hyperthyroidism Hyperaldosteronism Idiopathic

Question 40

What should you do to investigate systemic hypertension in cats?

Answer 40

Blood pressure Assess target organ damage *(damage to brain, kidneys, eyes and heart)*

Question 41

Why is it important to assess brain function if you suspect systemic hypertension?

Answer 41

It is important to assess brain function if you suspect systemic hypertension as systemic hypertension can lead to damage of blood vessels in the brain leading to strokes and encephalopathies

Question 42

Why is it important to assess the eyes if you suspect systemic hypertension?

Answer 42

It is important to assess the eyes if you suspect systemic hypertension as systemic hypertension can cause retinal detachment and acute onset blindness

Question 43

Why is it important to assess kidney function if you suspect systemic hypertension?

Answer 43

It is important to assess kidney function if you suspect systemic hypertension as systemic hypertension can cause lead to or worsen existing kidney disease

Question 44

Which drug should you use to treat systemic hypertension?

Answer 44

Amlodipine

Question 45

Which sites can you use to measure blood pressure in cats?

Answer 45

Distal limbs Tail (coccygeal artery)

Question 46

How can hyperthyroidism cause secondary hypertrophic cardiomyopathy?

Answer 46

Hyperthryroidism results in increased T3 and T4 production which will increase metabolic rate resulting in secondary hypertrophic cardiomyopathy

Question 47

How do you treat hypertrophic cardiomyopathy secondary to hyperthyroidism?

Answer 47

Treat the hyperthyroidism Atenolol (betablocker) if severe tachycardia Treat congestive heart failure Clopidorgel if necessary

Question 48

What is transient myocardial thickening (TMT)?

Answer 48

Transient myocardial thickening (TMT) is a reversible concentric hypertrophy of the myocardium caused by an infiltrative process

Question 49

Which signalement is more prone to transient myocardial thickening (TMT)?

Answer 49

Young cats

Question 50

How do you treat transient myocardial thickening (TMT)?

Answer 50

You treat transient myocardial thickening (TMT) the same way as hypertrophic cardiomyopathy

Question 51

What is the prognosis for transient myocardial thickening (TMT)?

Answer 51

Good prognosis if it regresses

Question 52

What happens in end-stage hypertrophic cardiomyopathy in cats?

Answer 52

End-stage hypertrophic cardiomyopathy is characterised by relative thinning of the ventricular walls and systolic dysfunction

Question 53

What is restrictive cardiomyopathy?

Answer 53

Restrictive cardiomyopathy is an inherited generalised disease/dysfunction of the myocardium characterised by increased ventricular wall rigidity

Question 54

What are the two subtypes of restrictive cardiomyopathy?

Answer 54

Endomyocardial form Myocardial form

Question 55

What is the characteristic feature of the endomyocardial form of restrictive cardiomyopathy?

Answer 55

The endomyocardial form of restrictive cardiomyopathy has a endocardial scar

Question 56

What are the characteristic features of the myocardial form of restrictive cardiomyopathy?

Answer 56

The myocardial form of restrictive cardiomyopathy has normal ventricular wall structure and function but increased size of the atriums

Question 57

What are the clinical signs of endocarditis in cats?

Answer 57

Pyrexia New heart murmur Limb weakness/paresis Respiratory distress Apathy