PATHOLOGY - Feline Acquired Cardiac Disease Flashcards
What is hypertrophic cardiomyopathy?
Hypertrophic cardiomyopathy is an inherited generalised disease/dysfunction of the myocardium characterised by increased ventricular wall thickness
Which heart chamber is mainly affected by hypertrophic cardiomyopathy?
Left ventricle
Which signalement is more prone to hypertrophic cardiomyopathy?
Older (above 9 years) male cats
Which two cat breeds are predisposed to hypertrophic cardiomyopathy?
Maine Coon
Ragdolls
Why are Maine Coons and Ragdolls predisposed to hypertrophic cardiomyopathy?
Maine Coons and Ragdolls have a mutation in the gene encoding for cardiac myosin-binding protein (MYBPC)
Describe the pathophysiology of hypertrophic cardiomyopathy
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 hyoertrophy of the right ventricle and eventual right-sided congestive heart failure
How does atrial dilation increase the risk of arterial thromboembolisms?
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
What are the eight clinical signs of hypertrophic cardiomyopathy?
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
Why is there often not a heart murmur associated with hypertrophic cardiomyopathy?
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
When would you hear a heart murmur with hypertrophic cardiomyopathy?
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
What kind of murmur would you hear with hypertrophic cardiomyopathy?
Left sided basal systolic crescendo-decrescendo mumur
How does hypertrophic cardiomyopathy cause arrhythmias?
Arrhythmias can occur due to structural damage to the heart as it enlarges due to hypertrophic cardiomyopathy
Which three arrhythmias are seen due to hypertrophic cardiomyopathy?
Atrial fibrillation
Ventricular arrhythmias
Bundle branch blocks
What is stage A of hypertrophic cardiomyopathy?
Cats that are at risk of developing hypertrophic cardiomyopathy due to their signalement but have no structural or clinical signs
What is stage B1 of hypertrophic cardiomyopathy?
Cats with clear left ventricular thickening (hypertrophy) but no left atrial dilatation
What is stage B2 of hypertrophic cardiomyopathy?
Cats with clear left ventricular thickening (hypertrophy) and left atrial dilatation
What is stage C of hypertrophic cardiomyopathy?
Cats with clinical signs of congestive heart failure
What is stage D of hypertrophic cardiomyopathy?
Cats with congestive heart failure that is refractory to treatment
Which two biomarkers can be indicative of hypertrophic cardiomyopathy?
NTproBNP
Cardiac troponin I
When are NTproBNP snap tests particularly useful in cats?
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
What are the key signs of hypertrophic cardiomyopathy on echocardiography?
Thickening of the left ventricle
Dilatation of the left atrium
What are the key signs on echocardiography that indicate there is a risk of arterial thromboembolism secondary to hypertrophic cardiomyopathy?
Dilatation of the left atrium
Reduced systolic function of the left atrium
Spontaneous echocontrast (smoke)
Clots in the left atrium
What is spontaneous echocontrast (smoke)?
Spontneous echocontrast (smoke) is an echogenic swirling pattern seen in instances of stagnant or low velocity blood flow
What is a saddle thrombus?
A saddle thrombus is a thromboembolism at the aortic trifurcation
Which forelimb is more commonly affected by arterial thromboembolism in cats?
Right forelimb
What are the five clinical signs of a thromboembolism in cats?
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)
How would you treat an arterial thromboembolisim in a cat?
Administer clopidogrel/heparin and provide analgesia
In cats at risk of hypertrophic cardiomyopathy, what should owners monitor for at home?
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
How should you treat stage A hypertrophic cardiomyopathy?
No treatment
How should you treat stage B1 hypertrophic cardiomyopathy?
No treatment
How should you treat stage B2 hypertrophic cardiomyopathy?
Treat with clopidogrel
How should you treat stage C hypertrophic cardiomyopathy?
Treat with clopidogrel and diuretics
What is clopidogrel?
Clopidogrel is an antiplatelet drug
What is the prognosis for cats with hypertrophic cardiomyopathy exhibiting signs of left-sided congestive heart failure?
Generally a prognosis of one year
What is the prognosis for cats with hypertrophic cardiomyopathy with an arterial thromboembolism?
Poor prognosis of around 184 days if they survive the first arterial thromboembolism
List three potential causes of secondary hypertrophic cardiomyopathy in cats
Systemic hypertension
Hyperthyroidism
Transient myocardial thickening (TMT)
What are four possible causes of systemic hypertension in cats?
Kidney disease
Hyperthyroidism
Hyperaldosteronism
Idiopathic
What should you do to investigate systemic hypertension in cats?
Blood pressure
Assess target organ damage (damage to brain, kidneys, eyes and heart)
Why is it important to assess brain function if you suspect systemic hypertension?
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
Why is it important to assess the eyes if you suspect systemic hypertension?
It is important to assess the eyes if you suspect systemic hypertension as systemic hypertension can cause retinal detachment and acute onset blindness
Why is it important to assess kidney function if you suspect systemic hypertension?
It is important to assess kidney function if you suspect systemic hypertension as systemic hypertension can cause lead to or worsen existing kidney disease
Which drug should you use to treat systemic hypertension?
Amlodipine
Which sites can you use to measure blood pressure in cats?
Distal limbs
Tail (coccygeal artery)
How can hyperthyroidism cause secondary hypertrophic cardiomyopathy?
Hyperthryroidism results in increased T3 and T4 production which will increase metabolic rate resulting in secondary hypertrophic cardiomyopathy
How do you treat hypertrophic cardiomyopathy secondary to hyperthyroidism?
Treat the hyperthyroidism
Atenolol (betablocker) if severe tachycardia
Treat congestive heart failure
Clopidorgel if necessary
What is transient myocardial thickening (TMT)?
Transient myocardial thickening (TMT) is a reversible concentric hypertrophy of the myocardium caused by an infiltrative process
Which signalement is more prone to transient myocardial thickening (TMT)?
Young cats
How do you treat transient myocardial thickening (TMT)?
You treat transient myocardial thickening (TMT) the same way as hypertrophic cardiomyopathy
What is the prognosis for transient myocardial thickening (TMT)?
Good prognosis if it regresses
What happens in end-stage hypertrophic cardiomyopathy in cats?
End-stage hypertrophic cardiomyopathy is characterised by relative thinning of the ventricular walls and systolic dysfunction
What is restrictive cardiomyopathy?
Restrictive cardiomyopathy is an inherited generalised disease/dysfunction of the myocardium characterised by increased ventricular wall rigidity
What are the two subtypes of restrictive cardiomyopathy?
Endomyocardial form
Myocardial form
What is the characteristic feature of the endomyocardial form of restrictive cardiomyopathy?
The endomyocardial form of restrictive cardiomyopathy has a endocardial scar
What are the characteristic features of the myocardial form of restrictive cardiomyopathy?
The myocardial form of restrictive cardiomyopathy has normal ventricular wall structure and function but increased size of the atriums
What are the clinical signs of endocarditis in cats?
Pyrexia
New heart murmur
Limb weakness/paresis
Respiratory distress
Apathy
