Cardiac Diseases Flashcards
What is the aetiology of Dilated Cardiomyopathy?
‘large dog heart disease’
Acquired
Idiopathic
may be related to genetic defects
common in larger breed dogs. Not seen much in cats.
Explain the pathophysiology of Dilated Cardiomyopathy
Progressive thinning of the myocardium, chambers become enlarged and heart ‘balloons’. AV valves stretch causing regurgitation of blood. At this stage there may be abnormalities in HR and rhythm as normal cant maintain normal heart rate.
Eventually falling CO leads to signs of congestive heart failure
What are the clinical signs of Dilated cardiomyopathy?
lethargy, depression, anorexia, exercise intolerance, cough/dyspnoea, syncope, murmur
Can cause sudden death due to fatal arrhythmias
Eventually results in heart failure
What is the most common acquired heart disease in dogs? (most likely small dogs)
Endocardiosis
Describe the aetiology of Endocardiosis (or Mitral Valve Disease MVD)
Degeneration of the AV valves (cause unknown)
- hereditary component
common in CKCS
Rare in cats
Describe the pathophysiology of Endocardiosis
The mitral valvular tissue degenerates. It becomes thickened and develops lesions. The valves cannot close properly. This cause the allowance of backflow or regurgitation of blood from the ventricles back to the atria.
This eventually leads to cardiac enlargement and output failure.
What are the clinical signs of Endocardiosis?
Clinical signs only show once the heart can no longer compensate.
Include:
-murmur (usually louder than for DCM)
- exercise intolerance (as cardiac function reduces)
- coughing (due to fluid build up in chest)
- ascites (in more advanced stages of heart failure once the right side is also affected then there begins to be a back up of fluid into the body)
- dyspnoea
- can disrupt sleep also
How can these acquired heart diseases be diagnosed?
Exam - auscultation may detect murmur
Radiography - can visualise heart outline and lung fields
Ultrasound - can see cardiac architecture and chamber size, blood flow etc
ECG - detects rhythm abnormalities
Lab tests - when cardiac cells become stressed, stretched or damaged they release an enzyme which we can test for.
Why would you select an Xray to diagnose a heart condition? Why wouldn’t you?
Can see if the heart is enlarged, can see if there is any fluid build up and can check for any lesions.
Will require sedation/ G/A
May have to be referred away to get scanned. Cost
Exposure to xrays
Not as definitive as Ultrasound
Why would you select an ultrasound to diagnose a heart condition?
Can see chamber size, all the architecture of the heart and the blood flow. Gives a definitive answer. None or light sedation only.
BUT may have to be referred
What is the body’s initial responses to heart disease?
Then after that?
Decreased CO causes increased heart rate and strength of heart beat.
Then the body will cause vasoconstriction to maintain BP to vital organs.
Later the RAA will try to retain Na and H20 to increase blood pressure
Describe the RAA system
BP falls,
Causes kidneys to release Renin.
Renin converts Angiotensinogen to angiotensin 1.
ACE then converts Angiotensin 1 to Angiotensin 2
Angiotensin 2 then does 2 things:
1. Acts on the adrenal gland to release Aldosterone
2. Causes vasoconstriction (increasing blood pressure)
Aldosterone causes salt retention in kidneys, water follows therefore increasing blood volume and therefore increasing blood pressure.
What is it called when the animal can no longer compensate for the heart failure?
Decompensated heart failure
What are the issues with decompensated heart failure?
Eventually compensatory mechanisms can actually exacerbate heart failure. For example the over worked, hypertrophic heart becomes fibrotic and inefficient. For example the fluid retention becomes pulmonary oedema and ascites
What are the common signs of most heart diseases
May include
- exercise intolerance
- coughing
- syncope (fainting)
- pale mm
- Tachycardia
- Tachypnoea
- Weak pulses
- Ascites
- weight loss
