Heart diseases in cats Flashcards
hypertrophic cardiomyopathy
- what is it?
- murmur origin with this condition?
- most common heart issue in cats
- increased thickening of left ventricular walls
- thickening can be focal or generalized
- they like to thicken up at the region below the aorta, on the ventricular septum > can bulge out through outflow tract during systole, result in aorta narrowing and faster jet of blood > this is what the systolic murmur often comes from
- “dynamic obstruction of the left ventricular outflow tract” = hypertrophic obstructive cardiomyopathy
HCM prevalence in cats?
- how does a murmur correlate with this? age?
General cat population 15%
- chance of HCM increases with age
- in young cats, most murmur patients will NOT have HCM
- in old cats, murmurs with HCM are far more common - about 40% of murmur cases have HCM. Additionally, some cats without a murmur will have HCM.
what is the main issue with HCM, ie. what is the cardiac dysfunction?
what subsequent changes occur in the heart and vascular system?
- Left ventricular concentric hypertrophy > diastolic dysfunction
> impaired filling / relaxation; stiff / thick heart muscle
> S4 gallop
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Left atrial (LA) dilation - Increased pressures → left sided CHF
- Thrombus → arterial thromboembolism
- ACVIM stages of feline cardiomyopathy?
- Presentation of feline cardiomyopathy?
No clinical signs:
- A: predisposed
- B1: subclinical. normal / mild left atrial enlargement. (low risk)
- B2: subclinical. moderate / severe left atrial enlargement. (high risk)
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History of heart failure signs:
- C: current/ prior CHF or ATE
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End-stage heart failure:
- D: CHF refractory to treatment
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* Asymptomatic
* Heart murmur, gallop
* Arrhythmia
* If they show signs – problem
> Left sided congestive heart failure (CHF)
> Biventricular CHF
> Sudden paresis/paralysis
feline heart murmur- most likely reason for it?
- left ventricular outflow obstruction
physical exam findings for feline CHF
Heart rate (normal 120-240)
* Tachycardia
* Bradycardia
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Respiration
* Tachypnea (>30/min), dyspnea
* Pulmonary edema, pleural effusion
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* Weak peripheral pulses
how a thrombus can develop from HCM
- Left ventricular hypertrophy
- Impaired left ventricular relaxation
- Left atrium enlargement
- Increased pressure in the left atrium: pulmonary edema
- Endothelial disruption and slow flow
- Thrombus formation
- A section of the thrombus dislodges, aortic thromboembolism
- Obstruction of blood flow
Diagnostic tests for HCM
- Thoracic radiographs, TFAST > Left sided CHF, pleural effusion
- Echocardiography > Diagnosis
- Biomarker > Diagnosis?
<><><><> - contrary to dogs, cats like to do pleural effusion
> would be good to know this first in case we need to stabilize the patient - echocardiography is good for Dx, as they might have a murmur or no murmur
- X-rays will not be as reliable as they are in the dog as the heart must get quite large for it to be apparent
where will pulmonary edema be in a cat vs in a dog?
cats can place pulmonary edema anywhere, not as often caudo-dorsal as in dog
thoracic radiographs to detect heart disease in cats
- what VHS values are important?
- LA measurement?
- other signs to look for?
- why dont x-rays always work so well for this?
- Vertebra heart sum
- < 8.0 for screening
(heart disease unlikely) - > 9.3 specific (heart disease likely)
<><> - LA>2cm
- Pulmonary edema
- Pleural effusion
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what do we do with between 8 and 9.3? - this is why X-rays don’t work as well
- hypertrophy goes more inward in the beginning, so we wont see this from our X-ray
- if we have hypertrophy, our LA is becoming bigger, but to see this on X-rays we need it to be bigger than 2cm, and up to 1.6cm is normal > must become significantly larger to be visible
Echocardiography
- how to diagnose heart disease?
- what can we see?
- LV walls – hypertrophic
cardiomyopathy
> look also for hypertrophic obstructive cardiomyopathy - LA size, echogenic contrast
- also look for thrombus
Biomarker: NT-proBNP
- is this useful for diagnosing heart conditions in cats?
- gets released with stretch in the heart
- has its limitations, bad for screening
- useful for narrowed down groups, when we think cardiac disease is likely
- but BNP also secreted by kidney, related to hyperthyroid, etc.
> other systemic diseases can increase BNP
What do we do in the following situations:
* Low grade heart murmur, young cat
* Heart murmur, older cat, asymptomatic
* Respiratory abnormalities
- Low grade heart murmur, young cat > less worried about heart disease in this situation
<><> - Heart murmur, older cat, asymptomatic
> Echocardiography
<><> - Respiratory abnormalities
> Suspicion for CHF: thoracic radiographs
- treatment for heart diseased cat, but not in heart failure?
- treatment for LV outflow tract obstruction? cautions?
- if not in heart failure, we have no studies, we don’t have a clear course of action… so probably just do nothing
- there is nothing we can do to slow progression
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LV outflow tract obstruction: atenolol - Reduction: heart rate, LV flow obstruction, prolongs diastole
- Ventricular arrhythmia
- Do NOT give atenolol in heart failure > as it reduces contractility, and this can push into heart failure. Don’t give if in doubt, as at the end of the day we have minimal evidence that it makes a positive difference.
prevention and treatment for thrombus
- Clopidogrel
- Rivaroxaban > add this to clopidogrel if clot is still there
- Aspirin > but clopidogrel is better
- Low molecular weight heparin (deltaparin, enoxaparin) > if we see a clot
