Hypertrophic Cardiomyopathy and RCM Flashcards by Corinne Perra

T/F: feline hypertrophic myopathy is secondary to increased ventricular pressures

False

Primary concentric hypertrophy
Usually LV but RV can be affected

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What breeds of cats are most predisposed to HCM?

Maine coon
Rag dolls
American shorthair

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Cardiomyocyte hypertrophy occurs in reponse to _________

Sarcomeric dysfunction

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What do you see on histopathology in HCM?

Myofiber disarray
Arteriosclerosis (hardening of the arteries)
Fibrosis

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Hypertrophic cardiomyopathy results in _______ dysfunction due to increased ventricular wall stiffness

Diastolic

—> impaired relaxation

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How does hypertrophic cardiomyopathy impact blood flow?

Diastolic dysfunction leads to increased ventricular filling pressures

—> increase LV pressures increase atrial and pulmonary venous pressures —> develop pulmonary edema +/- pleural effusion

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What is the obstructive form of HCM?

Systolic anterior motion of the mitral valve (SAM)

—> papillary muscle hypertrophy leads to displacement of chordae tendineae to the LV outflow tract during systole

—> impaired flow to aorta and some regurgitation through mitral valve

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T/F: cats with HCM do not have murmurs

True

Except in obstructive form

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Why do you see left atrial dilation in HCM>

Dilation due to chronically elevated filling pressures of the ventricles

-can be exacerbated by mitral regurgitation from SAM

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If the LA becomes moderately/severely dilated, what would you be concerned about in you cats?

Thrombus formation

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What is the usual signalment of cats with HCM?

Av age 6years
Younger presentation in pure breeds

Male>female

DSH is the most common breed diagnosed

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What is the most common presenting complaint in HCM cats?

Dyspnea (due to CHF)

Although 50% of cats are asymptomatic at time of diagnosis

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What co-morbidities are common with HCM?

Hyperthyroidism and renal disease

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Where is a murmur heard in a cat with HCM with SAM?

Systolic murmur, often left sided

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What can be present in auscultation of a cat with HCM?

Normal auscultation normal in cats with HCM

Gallop
Heart rate normal, low, or high

Premature beats

Femoral pulses are usually normal (unless ATE, arrhythmia, low output HF)

Abnormal lung sounds with CHF
Hypothermic if ATE or low output

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What are the DDX for murmurs in cats?

Structural heart disease

HCM
RCM
degenerative valve disease
congenital heart disease (young)

Physiological

dynamic right ventricular outflow tract obstruction
anemia
hyperthyroid
fever

Innocent

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How can we get a definitive diagnosis for HCM?

Echo

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What are DDX for LV concentric hypertrophy that you must rule out before you can contribute the hypertrophy to HCM?

Aortic stenosis
Systemic hypertension
Acromegaly
Infiltrative debase (lymphoma)

What are the most common arrhythmias in cats with HCM?

VPC
VT
APC
SVT
A fib

Test of choice if arrhythmia is auscultated is ECG

What is the test of choice if there are intermittent signs suspected to be due to arrhythmia ?

24hr holter monitor

What is the most commonly used biomarker in clinical feline cardiology?

N proBNP

-IDEXX snap test

What are drugs with potential benefits in treating asymptomatic cats with HCM

Diltiazem 
ACE inhibitor s
Aldosterone antagonist 
B blocker 
Antiplatelet drug (clopidogrel)

—> consider severity, risk factors, disease progression, drug side effects

Left atrial enlargement is a risk factor for what diseases?

CHF
ATE
Sudden death

—cardiologists recommend 1>drugs when LAE is present

What drug has been show to significantly reduce dynamic LVOTO?

Beta blocker (atenolol) 
-negative inotropic

What is the inpatient procedure for CHF due to HCM?

Thoracocentesis for pleural effusion Furosemide Supplemental O2 Clopidogrel Diltiazem /Pimobendan ? Dobutamine for low output HF (uncommon in HCM)

What is the outpatient procedure for patients with CHF due to HCM?

Thoracocentesis Oral furosemide Clopidogrel ACE inhibitor Pimobdenan/Diltiazem Refractory CHF: spironolactone, higher doses of furosemide, HCTZ, or pimobdenan

What is the treatment for arterial thromboembolism ?

Analgesia (fentanyl or buprenorphine) Antithrombic therapy - heparin - clopidogrel Supportive care - bladder and prevention of urine/fecal scald - musculoskeletal support - nutritional - monitor for reperfusion injury (hyperkalemia/acidosis), azotemia, arrhythmia, CHF, necrosis, infection

What is the criteria for treating arrhythmias?

Ventricular or supraventricular tachycardia Frequent singles, couplets, and/or triplets R on T

How can you treat acute SVT?

Diltiazem or esmolol

How do you treat chronic SVT?

``` Diltiazem Atenolol Digoxin Ivabradine Amiodarone ```

How do you treat acute ventricular tachycardia ?

Lidocaine | Esmolol

How do you treat chronic ventricular tachycardia?

Atenolol Sotalol Amiodarone

How can clients monitor for progression of heart failure?

Sleeping/resting respiratory rate (>30br/min indicates HF) New/increased cough (dog) Lethargy, syncope, weakness, decreased appetite, abdominal distention

How can progression of HR be monitored in the clinic?

``` HR and rhythm RR and effort Mentation BP Weight Renal values and electrolytes Radiographs ECG Holter Echo ```

What side effects can result from HF medications that clients should watch for at home?

Appetite Energy level Vomiting, diarrhea Hydration Mentation

What is the prognosis of HCM?

Good (several years for most) asymptomatic cats Poor long term prognosis if CHF develops Sudden death can occur (10-25% of HCM related deaths) ATE also a potential complications

RCM is a primary myocardial disease that is characterized by _________ dysfunction

Diastolic

T/F: both HCM and RCM are due to diastolic dysfunction and increase in ventricular wall thickness

False Both are due to diastolic dysfunction HCM—>increased ventricular wall thickness RCM—>normal ventricular wall thickness

What changes occur to the heart in RCM?

Focal or diffuse fibrosis in the endocardium and/or myocardium Walls are usually normal thickness but focal thinning/thickening is possible Atrial dilation in most common

How does the diastolic filling differ between HCM and RCM?

HCM: prolonged myocardial relaxation -> decreased passive filling DCM: restrictive filling —> ventricle is stiff impairing atrial systolic filling

What is the signalment of RCM?

Adult onset Av age 7 No sex or breed predisposed

What are possible PE findings in cats with RCM?

Can have no auscultable abnormalities Gallop/low grade murmur possible HR normal/low/high Premature beat possible Femoral pulses normal unless ATE Abnormal lung sounds Hypothermic if ATE or low output HF

How do you treat cats with RCM?

``` Asymptomatic with atrial enlargement: antithrombic (clopidogrel) ACE inhibitor (enalapril or benazepril ) + pimobdenan if systolic dysfunction is present ``` Symptomatic: same treatment for HCM with HF

What is the prognosis for cats with RCM?

Symptomatic - mean survivial is 4-9months