Lecture 14 9/17/24 Flashcards
What is cardiomyopathy?
-primary heart muscle disorder in which the heart muscle is structurally and functionally abnormal
What is dilated cardiomyopathy?
left ventricular dilation and systolic myocardial dysfunction +/- right ventricular involvement
What causes ventricular dilation in DCM?
hypokinesis
What is the etiopathogenesis of DCM?
-cardiomyocytes in the mature individual cannot reproduce to correct abnormalities and/or damage
-dilated heart works at mechanical disadvantage
-dilation tends to be progressive
What can cause systolic myocardial dysfunction?
-loss of cardiomyocytes due to necrosis
-ultrastructural abnormalities of the contractile apparatus
-persistent tachycardia
-nutritional deficiencies
Why is DCM considered a phenotype?
it is an “end-stage heart” that can result from virtually any pathologic insult to the myocardium
What are the potential pathways of DCM?
-toxic
-metabolic
-immune
-infective
-nutritional
Which dogs have a genetic predisposition for DCM?
-doberman pinscher
-great dane
-newfoundland
-irish wolfhound
What is the pathophysiology of DCM?
-impaired systolic myocardial function results in progressive ventricular dilation
-high ventricular filling pressures are reflected back upon the upstream capillary bed
-reflection results in edema and/or cavitary effusion
What is the typical signalment of DCM patients?
-large or giant breed dog
-middle aged
-doberman, boxer, great dane, irish wolfhound, or cocker spaniel
What are the clinical signs seen in DCM patients?
related to CHF:
-dyspnea
-cough
-weight loss
-syncope
-ascites
What are the physical exam findings seen in DCM patients?
-soft systolic murmur of MR origin and/or gallop sounds
-arrhythmia
-crackles suggestive of pulmonary edema
-tachycardia
-ascites
What are the diagnostic findings for DCM on chest rads?
-enlargement of cardiac silhouette
-LAE with pulmonary infiltrates (left CHF)
What are the diagnostic findings for DCM on ECG?
-ventricular arrhythmias/AFib
-chamber hypertrophy patterns
-intraventricular conduction disturbances
What are the diagnostic findings for DCM on echo?
-increased end-systolic and end-diastolic volumes
-secondary MR
What are the characteristics of DCM in doberman pinschers?
-high incidence of ventricular tachyarrhythmia and sudden cardiac death
-heart failure associated with brief and rapid progressive course
-affects left ventricle primarily
-diffusely distributed edema
-straightening of caudal border of cardiac silhouette
-increase in cardiac silhouette dorsoventral dimension
-DCM is slowly progressive, insidious disorder
-should screen outwardly normal dogs; can delay clinical signs with pimobendan when criteria are met
What are the characteristics of DCM in boxers?
arrhythmogenic form of CM is common
What are the characteristics of DCM in giant breeds?
-pleural effusion and ascites are relatively common
-AFib is common
-likely a sex-linked trait in great danes
What are the characteristics of DCM in cocker spaniels?
-valvular disease is more common but DCM does occur
-affected dogs have low plasma taurine conc. and often respond to taurine supplementation
What therapy is indicated for stage B DCM?
-pimobendan
-ACE inhibitors and beta-blockers for cardioprotective effect
What therapy is indicated for stage C DCM?
-furosemide
-ACE inhibitor
-pimobendan
-possibly spironolactone
-digoxin if AFib is present
What are the characteristics of taurine supplementation in DCM patients?
-deficiency is associated with DCM in cocker spaniels, golden retrievers, and newfoundlands
-may be able to withdraw cardiac drugs and only treat with taurine supp.
-should measure plasma taurine any time an at risk or atypical breed presents with DCM
Why is L-carnitine sometimes supplemented in DCM patients?
it may favorably affect myocardial energetics
What is arrhythmogenic right ventricular cardiomyopathy?
inherited heart muscle disease characterized by fibrofatty replacement, VTA and sudden cardiac death
What are the categories of ARVC?
Cat. 1: VTA in the absence of clinical signs; most common
Cat. 2: syncope, presumably related to ventricular tachycardia
Cat. 3: CHF due to systolic myocardial dysfunction
What are the characteristics of ARVC?
-many boxers present with VTA in the absence of myocardial dysfunction
-progression between categories is NOT inevitable
-evidence of an association between a striatin mutation and DCM in boxers
-not exclusively a right ventricular disease
What are the ECG findings with ARVC?
-ventricular ectopic complexes
-ventricular premature complexes, potentially in couplets or triplets
-ventricular tachycardia
What are the rad. findings with ARVC?
typically normal
What are the echo findings with ARVC?
-typically normal
-possible to see RA/RV dilation and LV systolic dysfunction
What ECG/Holter finding is suggestive of ARVC diagnosis?
100 VPC/day or greater
What is the diagnosis and treatment approach for ARVC?
-treat subclinical arrhythmias only if ECG characteristics provide indication
-use sotalol to control ventricular arrhythmias when associated with syncope/weakness
What are the characteristics of ARVC prognosis?
-association exists between severity of arrhythmia and syncope and survival
-no association between anti-arrhythmic treatment and survival
-longevity of patients in not statistically different from unaffected control group
-echo finding of systolic dysfunction is risk factor for poor outcome
What is hypertrophic CM?
hypertrophy of a non-dilated ventricle that develops in the absence of other diseases that would result in myocardial growth
What are the characteristics of HCM?
-terriers predisposed
-heart failure is rare
-sudden death occurs occasionally
