Lecture 13: Canine Myocardial Diseases

cardiomyopathies can be

• confined to the heart

• part of generalized systemic disorder

cardiomyopathies include

• dilated cardiomyopathy

• hypertrophic cardiomyopathy

• restrictive cardiomyopathy

• arrhythmic right ventricular cardiomyopathy

• nonspecific cardiomyopathy

• primary (intrinsic) cardiomyopathy

• secondary (extrinsic) cardiomyopathy

cardiomyopathy in cats

most common cause of heart disease

cardiomyopathy in dogs

second most common heart disease → most common heart disease in giant breed dogs

clinical manifestations of cardiomyopathy

• congestive heart failure → dyspnea, exercise intolerance

• cardiac arrhythmias → syncope, episodic weakness

• thromboembolism → acute lameness, other signs, dyspnea

• sudden death

dilated cardiomyopathy

• primary myocardial disease characterized by ventricular dilation and systolic dysfunction

• dilation leads to secondary mitral ± tricuspid valve regurgitation

• large and giant breed middle-aged to older dogs → males overrepresented

clinical consequences of DCM

heart failure, arrhythmias, sudden death

what breeds are genetically predisposed to DCM?

dobermans and boxers

what nutritional issues can cause DCM?

taurine deficiency, carnitine deficiency, and grain-free diets

DCM history

• variable cough, dyspnea, syncope, weakness, collapse, anorexia, exercise intolerance, weight loss

• sometimes misdiagnosed with bronchitis in last 3 weeks

DCM PE

• muffled or soft heart sounds

• soft systolic murmur

• gallop or irregular rhythm, ± tachycardia

• weak pulses, pulse deficits

• jugular distension, ascites or crackles

DCM ECG

• a fib, VPCs, ventricular arrhythmias, APCs

• LA and/or LV enlargement patterns

• conduction disturbances

DCM thoracic radiographs

• cardiomegaly

• pulmonary edema

• pleural effusion or ascites

DCM biomarkers

• increased NT-proBNP, increased cTnl

• genetic testing

DCM pathology

• fibrosis

• inflammation

• lipid accumulation

• myocyte degeneration

• edema

• variable by breed and case

DCM echo

• dilated ventricles, thin walls

• decreased systolic function

• reduced ejection fraction

• secondary mitral ± tricuspid regurgitation

• left atrial enlargement

what is this?

DCM

DCM associated with certain diets

• diets high in peas, pea fractions, lentils, chickpeas, ± sweet potatoes

• usually advertised as grain free diets

• still susceptible to arrhythmias and sudden death

DCM associated with taurine deficiency

• nutritional DCM

• breed disposition → goldens, cocker spaniels, newfoundlands

• prognosis may be better than other DCM cases

DCM associated with carnitine deficiency

• nutritional DCM

• breed disposition → boxers, cocker spaniels, dobermans

• plasma levels may not reflect myocardial levels

• myocardial biopsy is most accurate but invasive

NT-proBNP is used to

search for occult disease

blood taurine concentration is used in

suspected cases of nutritional DCM

cardiac troponin I

often modestly elevated, especially dobies and grain free diet DCM

canine DCM drugs for CHF

• furosemide → lowest possible dose

• pimobendan → also used in occult phase

• ACE inhibitor

• ± spironolactone

canine DCM drugs for arrhythmias

• if atrial fibrillation → digoxin and diltiazem

• if serious ventricular arrhythmias → sotalol, mexiletine or amiodarone

diet for canine DCM chronic management

change if on high pea or high lentil or grain free diet

preclinical stage DCM treatment approach

pimobendan

CHF stage DCM treatment approach

furosemide + pimobendan + ACE inhibitor + spironolactone

arrhythmias DCM treatment approach

sotalol, diltiazem + digoxin

nutritional DCM treatment approach

taurine supplementation, diet correction

DCM prognosis

• doberman (with CHF) → poor: median survival 3-6 months

• great dane, irish wolfhound → fair to guarded

• early detection (B2) → improved survival with pimobendan

• sudden death risk → high, especially in dobermans with VPCs

doberman pinscher cardiomyopathy

• occult cardiomyopathy

• ventricular arrhythmias

• between 45-63% of dobermans have DCM

• ventricular arrhythmias/ventricular fibrillation

• cardiogenic shock

boxer cardiomyopathy

• arrhythmogenic right ventricular cardiomyopathy

• sustained, rapid ventricular tachycardia

• ECG → wide QRS, wide P wave

• average age is 8 years

• dysfunctional ryanodine receptor

DCM of giant breed dogs

• left heart failure or biventricular failure

• atrial fibrillation is common

• sudden death is possible

• survival shorter if CHF

• asymptomatic with arrhythmia alone → often a prolonged survival

cardiomyopathy of irish wolfhounds

• left atrial enlargement and arrhythmias are hallmarks

• chylous pleural effusion sometimes develops if overt DCM

• fractional shortening is higher than many dogs with cardiomyopathy

• atrial fibrillation is common and may be the first sign of cardiomyopathy

• can be slowly progressive

english and american cocker spaniel cardiomyopathy

• average age 6-10 years

• nearly equal male:female ratio

• LVE pattern with tall R wave, APCs common

• generalized cardiomegaly with pulmonary edema

• may have low plasma or whole blood taurine concentrations

• pimobendan may slow progression

DCM of newfoundlands

• typically middle age or older

• some normal dogs may have fractional shortening between 20-28%

• atrial fibrillation is common

• taurine deficiency if eating certain diets

• refractory CHF is most common cause of death/euthanasia!

juvenile DCM in portuguese water dog

• sudden death and peracute CHF

• 5 weeks to 3-4 months of age

• necropsy/echo findings = typical DCM

• conflicting reports about the role of taurine

• genetic mutation → chromosome 8

• arrhythmias infrequent, soft murmur or gallop

• pulmonary edema, hepatomegaly

doxirubricin toxicity

• DCM-like syndrome

• oxidant injury

• arrhythmias

• cumulative dose >240 mg/ml2

• caution in dogs predisposed to DCM

canine hypertrophic cardiomyopathy

• very uncommon

• GSP, GSD, shi tzu

• genetic basis in GSP

• conduction abnormalities, 3rd degree AV block, ventricular arrhythmias

• CHF may develop

• sudden death first sign in some cases

myocarditis

• inflammatory response in myocardium

• viral, bacterial, fungal, parasitic, immune etiology

• common possible features → CHF, arrhythmias, thromboembolic disease

suspects of myocarditis

• parvo

• foot and mouth disease

• bluetongue virus in sheep

• encephalomyocarditis

• equine viral arteritis

• feline infectious peritonitis virus

• FIV in cats

• lyme

• fungal

• protozoal

trypanosomiasis (chagas disease)

• trypanosoma cruzi

• reduviidae bug → vector

• texas, mexico, south and central america

• severe myocarditis

• right atrium and ventricle may predominate

• left sided or right sided CHF

• treatment with ragonil