Feline Cardiomyopathy Flashcards
Define cardiomyopathy
disease of the heart muscle
List the 2 main types of cariomyopathy
Hypertrophic Cardiomyopathy (HCM) Dilated Cardiomyopathy (DCM)
Which cardiomyopathy is more common today?
HCM
What is DCM
ventricular muscle lose ability to contract properly; you end up with flaccid ventricular muscles and dilated ventricular lumen
What causes DCM
taurine defidience
What is HCM?
disorganization and thickening of the muscle fibers in the ventricular walls; thickening of the ventricular muscle
What are 2 causes of HCM?
idiopathic
secondary to hyperthyroidism
How does HCM alter systemic circulation?
- The thickened left ventricle has a smaller lumen size, so less blood will fit
- Because less blood fits into the left ventricle, more blood gets stored in the left atrium
- Left atrium walls stretch as the left atrium enlarges
- When the left atrium can’t get any bigger, the blood backs up into the pulmonary vasculature
- The backup of blood increases pulmonary pressure
- When pulmonary pressure gets too high, fluid leaks from the blood vessels typically into the pleural space (pleural effusion)
- Because a decreased amount of blood is being ejected from the left ventricle, the cardiac output decreases
- When cardiac output decreases, the body increases the HR to try and increase blood deliver to tissues, but what this really does is make the heart beat faster which doesn’t allow the ventricle to completely fill, so even less blood enters the left ventricle and cardiac output decreases more
- Begin a cycle of increasing HR and decreasing cardiac output that eventually exhausts the heart
- Additionally, the backup of blood into the left atrium and pulmonary vessels worsens, increasing pressure
HCM Clinical Signs
- lethargy and depression
- dyspnea and respiratory distress due to pleural effusion secondary to left heart failure
- anorexia
What are different ways a cardiomyopathy cat may present?
- No outward evidence of heart Dz, but a heart murmur may be found on PE
- Sudden death (HCM)
- A stressful event that precedes the onset of acute respiratory signs
- Hind limb paresis or paralysis secondary to thromboembolic Dz (saddle thrombus) +/- other clinical signs
How can a thrombus develop in HCM cats? Where is the most common place it will lodge?
- Blood pools in left atrium and begins to swirl around
- Swirling activates coagulation cascade and thrombus forms in the left atrial lumen (usually on the wall)
- Part or all of the thrombus breaks free
- Travels thru left ventricle out the aorta
- Thrombus follows path of least resistance until it reaches blood vessels that are too narrow for it to pass through
- A lodged thrombus at the aortic bifurcation (common lodging spot) disrupts blood supply to each hind limb
- Hind limbs = cold, cyanotic foot pads, no obvious femoral pulse, extreme pain for first 24hrs
Other possible places for a thrombus to lodge & CS
- front limb
- unilaterally in one hind limb
- same clinical signs as saddle thrombus, just in a different limb
- kidney (rare, but possible)
Prognosis for saddle thrombus
- poor
- not impossible to recover from physical signs
- but b/c thrombus is secondary to HCM, there is a high risk for another thrombotic event
Medical prevention of thrombus formation
-Anticoagulant therapy (25mg Aspirin) q3-4 days
HCM medical therapy
- list drugs
- say what they do
- Calcium channel antagonists to decrease HR and relax ventricular muscles in non-obstructive HCM
- Beta antagonists to decrease HR and relax ventricular muscles in obstructive HCM
- Furosemide if left sided heart failure is causing pulmonary edema
- Thoracocentesis if left sided heart failure is causing pleural effusion followed by diuretics
- Gradual discont. diuretics if excess fluid is resolved
