Cardiac Diseases Flashcards
What is heart failure?
When the heart fails to pump sufficient blood to meet the metabolic needs of the body’s tissues.
What are the compensatory mechanisms in heart disease?
The sympathetic nervous system responses, RRA system, myocardial hypertrophy and the Frank-Starling mechanisms.
They help maintain cardiac output.
What is compensated heart failure?
The bodies mechanisms help maintain cardiac output meaning in the early stages there is a slight decrease in cardiac function which may be missed and the animal remains asymptomatic.
What happens initially and later on in heart disease?
Initial response:
Heart rate increases. (sympathetic nervous system)
Peripheral vasoconstriction occurs to maintain BP to vital organs.
Later:
Heart adapts to increased filling by increasing the output (SV).
Sodium and water are retained by the kidneys to increase BP.
Improved contractility.
What is decompensated heart failure?
When the mechanisms can no longer maintain cardiac output and become insufficient.
What is PRIMARY acquired heart disease?
Where there is underlying disease in the heart muscle or associated structures.
What is SECONDARY acquired heart disease?
Where the disease develops subsequent to another condition.
What are types of acquired heart disease?
Cardiomyopathies (Dilated/Hypertrophic)
Endocardiosis (Chronic degenerative valve dx)
Pericarditis
Endocarditis
ACQUIRED HD
Dilated Cardiomyopathy (DCM)
What is the aetiology?
Idiopathic.
May be related to genetic biochemical defects.
Several breeds recognised as being over represented - esp. large/giant breeds.
ACQUIRED HD
Dilated Cardiomyopathy (DCM)
What is the pathophysiology?
Progressive thinning of the myocardium which impairs the efficiency of the heart contraction.
The atria becomes enlarged.
The heart wall stretches becoming ‘ballooned’.
Eventually the AV valves stretch leading to regurgitation of blood and atrial enlargement.
At this stage there may be abnormalities in HR and rhythm.
Eventually falling CO leads to signs of congestive heart failure. (This is usually end stage.)
ACQUIRED HD
Dilated Cardiomyopathy (DCM)
What are the clinical signs?
Lethargy
Depression
Anorexia
Exercise intolerance
Cough/dyspnoea
Syncope
Murmur
Could cause sudden death!
Progressive resulting in heart failure.
ACQUIRED HD
Dilated Cardiomyopathy (DCM)
What are the diagnostic techniques?
History
Clinical signs
Thoracic auscultation – murmur or arrythmias
Chest radiographs – show enlarged heart (along with other signs)
ECG
Blood pressure measurements
Cardiography
Haematology and biochemistry
ACQUIRED HD
Hypertrophic Cardiomyopathy (HCM)
What is the aetiology?
Most commonly acquired heart disease in cats.
Can be idiopathic/genetic especially in Maine Coon.
Often secondary to hyperthyroidism.
ACQUIRED HD
Hypertrophic Cardiomyopathy (HCM)
What is the pathophysiology?
Progressive thickening of the ventricular muscle.
Enlarged heart, with thickened walls (opposite of dilated cardiomyopathy)
Chambers become narrowed reducing chamber volume.
Reduced cardiac output, backpressure and atrial enlargement results.
Signs of heart failure may only be seen in advanced stages of disease.
ACQUIRED HD
Hypertrophic Cardiomyopathy (HCM)
What are the clinical signs?
May have a murmur or gallop rhythm.
Lethargy
Depression
Anorexia
Leading to heart failure
Dyspnoea
Tachypnoea
Occurs mainly in cats as a result of hyperthyroidism.
