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Small Animal Medicine II > Canine Heart Diseases & Cardiomyopathies > Flashcards

Canine Heart Diseases & Cardiomyopathies Flashcards

1
Q

What valves are most commonly affected by endocarditis? What are the 4 most common causes?

A

mitral and aortic valves (left-sided!)

  1. Staph
  2. Strep
  3. E. coli
  4. Bartonella - can be negative on culture
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2
Q

What lesion is characteristic of endocarditis? What does this cause?

A

vegetative lesion - fibrin + platelets + bacteria

severe valvular regurgitation and spread of bacteria into systemic circulation

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3
Q

What is this most common origin of bacterial endocarditis? What perpetuates it?

A

recent/current infection of skin, mouth, urinary tract, prostate, or lungs

  • chronic bacteremia
  • diseased valves - SAS, mitral disease; damage causes poor protective barrier
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4
Q

What patients are most commonly affected by bacterial endocarditis? What signs are most common?

A

young, large breed dogs

  • FEVER
  • new, severe murmur
  • hyperkinetic, bounding pulse
  • polyarthritis
  • thromboembolism
  • CHF
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5
Q

What is required for diagnosing endocarditis?

A

blood culture

+/- echo
+/- thoracic radiographs

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6
Q

What treatment is used for endocarditis?

A

appropriate IV antibiotics for at at least 6-8 weeks - Ampicillin, Baytril —> guarded prognosis due to bacterial embolization

  • address failure, arrhythmias, and underlying disease
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7
Q

What is the difference between primary and secondary DCM?

A

PRIMARY - idiopathic, genetic, inflammatory (arrhythmogenic right ventricular cardiomyopathy - ARVC)

SECONDARY - persistent tachycardia, toxicosis (doxorubicin, epirubicin), muscular dystrophy, infections (Parvo, Borreliosis, Trypanosomiasis), metabolic conditions, nutritional disorders (grain-free, taurine, carnitine)

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8
Q

What is DCM? What breeds are predisposed?

A

myocardial disease characterized by decreased contractility with secondary compensatory ventricular dilation

large/giant breeds - Doberman (pyruvate dehydrogenase, titan), St. Bernards, Irish Wolfhounds, Boxers (ARVC), Newfoundlands, Afghans, Dalmations, Great Danes (X-linked), Cocker Spaniels, Portuguese Water Dog (autosomal recessive)

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9
Q

What is the pathogenesis of DCM?

A
  • systolic contractile failure
  • neurohormonal activation causes sodium and water retention/vasoconstriction, which increases preload, and proliferation of myocytes/fibroblasts
  • cardiac remodeling = hypertrophy, dilation, fibrosis, sphericity
  • changes cause abnormal systolic and diastolic function and arrhythmias
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10
Q

What are the 5 stages of DCM?

A
  • Stage A - unaffected dogs with increased risk (breed/genotype)
  • Stage B1 - electrical changes (VPC, Afib), but NO structural changes
  • Stage B2 - LV systolic dysfunction AND structural changes +/- electrical changes
  • Stage C - electrical and structural changes with CHF
  • Stage D - end-stage disease with CHF refractory to standard therapy
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11
Q

What are some signs of DCM?

A
  • first sign can be sudden death
  • weakness, lethargy
  • tachypnea, dyspnea, exercise intolderance
  • cough/gagging
  • anorexia
  • ascites
  • syncope
  • tall R waves
  • ventricular enlargement
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12
Q

What is seen on PE in patients with DCM?

A
  • systolic murmur or S3 gallop
  • arrhythmia (pulse deficit)
  • weak arterial pulse
  • LS-CHF - pulmonary edema, cough
  • RH-CHF - ascites, jugular pulses
  • cardiac cachexia
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13
Q

What changes in EKG are expected with DCM? What diagnostic is considered more sensitive?

A
  • atrial/ventricular enlargement patterns - abnormal P and R waves, APCs, VPCs, bundle branch blocks
  • tachyarrhythmias - Afib, Vtach
  • often normal

Holter monitor - <50 VPC/day

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14
Q

What is seen in thoracic radiographs in cases of DCM? How is this limited?

A

CHF = severe enlargement

cannot assess function unless CHF is present

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15
Q

How are biomarkers being used to diagnose DCM?

A

(DNA, NT-proBNP, troponin I) - NOT to diagnose —> indicate those at-risk, aid in screening and response to therapy

  • echo is confirmatory
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16
Q

What is the diagnostic test of choice for DCM? What 3 things are seen?

A

echocardiography

  1. LV systolic dysfunction
  2. mitral regurgitation, annulus enlargement
  3. LA enlargement
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17
Q

What breed is most commonly affected by DCM? What are the 2 major outcomes?

A

Doberman Pinschers —> adult onset, left/biventricular failure, arrhythmias

  1. sudden death
  2. CHF
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18
Q

How do most Dobermans present with DCM? What is key to survival?

A

occult phase (Stage B2) at 2-4 years —> progressive LV dysfunction, sudden death before any signs

early intervention/detection —> screen at 3 years (q 1 y) with echo, holter, and NT-proBNP to determine if Pimobendan, ACEi +/- Sotalol are indicated

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19
Q

What is the difference in the causes of DCM in American and English Cocker Spaniels?

A

AMERICAN = low plasma taurine levels (poorer prognosis) —> taurine supplementation and L-carnitine may improve LV function, but will not be normal

ENGLISH = not taurine related, likely heritable

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20
Q

What is the most common cause of DCM in Great Danes? What is the most common finding? What monitoring is recommended?

A

X-linked recessive - males > female, especially sons of affected females, daughters of affected fathers likely silent carriers

atrial fibrillation before signs of myocardial changes

annual monitoring, especially with Afib

21
Q

What is the most common cause of DCM in Irish Wolfhounds? What is the most common sign? What is not seen?

A

familial, males > females

  • atrial fibrillation about 24 months prior to CHF
  • long-term result = biventricular CHF

sudden death

22
Q

How are Portuguese Water Dogs most commonly affected by DCM? What is the most common sign?

A

juvenile form —> autosomal recessive trait linked to chromosome 8

affected puppies commonly collapse and die between 2-32 weeks of age

23
Q

How are Newfoundlands affected by DCM? What are the most common signs?

A

adult onset

  • biventricular CHF
  • heart murmurs rare, but AF and VPCs seen
24
Q

What is arrhythmogenic right ventricular cardiomyopathy (ARVC)?

A

Boxer cardiomyopathy —> primary myocardial disease where fibro-fatty replacement of the RV myocardium causes ventricular arrhythmias

  • English Bulldogs also affected!
25
Q

What are the 5 most common results of ARVC?

A
  1. ventricular arrhythmias
  2. ventricular systolic dysfunction and dilation
  3. CHF
  4. syncope
  5. sudden death
26
Q

What are the 3 types of ARVC? How do most Boxers present?

A
  • Class I = asymptomatic
  • Class II = collapse and syncope
  • Class III = CHF (left AND right)

normal PE, arrhythmia may be auscultated but is commonly missed

27
Q

What is the diagnostic test of choice for ARVC? Why?

A

Holter monitor

  • biomarkers (troponin I, BNP) not helpful
  • genetic testing only available for Boxers - negative result does not r/o possibility of developing gen
  • majority of dogs have normal structure, so echocardiography is only helpful for dogs with overt signs of CHF
28
Q

What is seen on ECGs and Holter monitors in cases of ARVC?

A

ECG - typically performed for 2-5 minutes —> VPCs (single, couplet, runs of VT), left bundle branch block

HOLTER - 24 hour hours, 300 VPC per day (always screen Boxers!)

29
Q

What are the 3 stages of ARVC? How do they present on physical exams?

A
  1. ventricular arrhythmias with NO cardiac dysfunction and symptoms - 50-300 VPC/day is possible, >300 VPCs/day very likely
  2. ventricular arrhytmias progress, no cardiac dysfunction, SYNCOPE - normal PE and echo, Vtach on Holter (syncope when >300 bpm >8 s)
  3. ventricular arrhythmia, cardiac dysfunction, heart failure, syncope - CHF on PE, echo shows LV dilation and poor function, Vtach and Afib with hugh LA on Holter
30
Q

When is treatment recommended for ARVC?

A

when VPCs > 1000/day or clincial signs of weakness/syncope —> must treat or will develop DCM morphology

31
Q

What are the 2 major treatments of ARVC? When patient is in failure?

A
  1. Sotalol +/- Mexiletine
  2. fish oil

treat failure and add antiarrhythmic

32
Q

What is the prognosis of ARVC like?

A
  • sudden death always possible with arrhythmias
  • can live for years on medication
  • must find and treat CHF quickly
33
Q

When can tachycardia cause DCM? What is indicative of tachycardia being the cause?

A

HR > 200 bpm for more than 2-6 weeks = myocardial failure —> if resolved early, can return to normal in 1-2 weeks

all 4 chambers will become enlarged —> true dilation and failure causes ascites and pulmonary edema

  • hypoxia NOT mechanism for failure
34
Q

What are some nutritional causes of DCM?

A
  • DOGS = alcohol, Doxorubicin, Adriamycin, L-carnitine deficiency (Cockers, Goldens, Newfies)
  • DOGS and CATS = grain-free, boutique diets deficient in taurine, thiamine, vitamin E, and selenium, while containing grapeseed oil, heavy metals, and monensin
35
Q

Why is it especially important to screen for DCM in at-risk breeds?

A

occult disease most common in these breeds - early detection allows time to stop breeding and provide early treatment if arrhythmias or low contractility are detected

  • average onset is 5-7 years, but can be as early as 2 years
36
Q

What screening is recommended for DCM at-risk breeds?

A

start at 2 years and screen annually —> 24 Holter monitor looking for VPCs (expect ~50 single VPCs/day in healthy Dobermans, more = concern for occult disease)

37
Q

What ancillary tests are commonly used while screening at-risk breeds for DCM?

A
  • biomarkers - NT-proBNP
  • genetic tests
  • short ECGs
38
Q

What are the 6 strategies for treating DCM?

A
  1. INOTROPIC SUPPORT - Pimobendan
  2. NEUROHORMONAL SUPPORT - ACEi, Spironolactone
  3. PRELOAD REDUCTION - Furosemide, low sodium diet
  4. AFTERLOAD REDUCTION - ACEi, Pimobendan
  5. VENT. ARRHYTHMIA - Lidocaine, Sotalol, Mexelitine
  6. SUPRAVENT. ARRHYTHMIA - Digoxin, Diltiazen (NO beta-blockers)

check diet, monitor RR

39
Q

When has it been proven that ACEi and Pimobendan are beneficial for occult DCM?

A

in Dobermans and Irish Wolfhounds

40
Q

What are 5 negative predictors for survival in patients with DCM?

A
  1. age of onset
  2. ascites
  3. atrial fibrillation
  4. decreased ejection fraction
  5. restrictive diastolic pattern
41
Q

What causes myocarditis? What are the 7 most common etiologies?

A

mild/transient/fulminant immune response leads to heart abnormalities

  1. bacterial - Bartonella, Lyme
  2. fungal
  3. viral - Parvo, Herpes, Adenovirus, Distemper
  4. toxins - anthracyclines (doxorubicin)
  5. protozoal - trypanosoma (Chagas), Toxoplasma, Neospora, Babesia, Hepatozoan
  6. hypersensitivities - cephalosporins, Digoxin, diuretics
  7. immunologic - post-infectious, IBD, lupus
42
Q

How is viral etiology of myocarditis unique?

A

multisystemic signs predominate

43
Q

How does Doxorubicin cause myocarditis?

A

decreases CO and causes arrhythmias/myocyte damage, systolic dysfunction, CHF —> similar presentation to DCM

  • cumulative dose!
44
Q

What are 5 methods to reduce Doxorubicin toxicity?

A
  1. use lowest cumulative doses
  2. give drug slowly (CRI) —> rapid infusion causes peak plasma levels > toxic dose
  3. liposome-encapsulated forms
  4. pretreat with Dexrazoxane
  5. Carvedilol may minimize damage
45
Q

What transmits Trypanosoma that can cause myocarditis? What are the 2 types of presentations?

A

Reduviid/kissing bugs (TEXAS/Southern US) carry Trypanosoma cruzi, which is spread from feces deposited by wounds or ingestion of bug

  1. ACUTE - tachyarrhythmias, AV conduction disturbances, and sudden death common in puppies and young dogs
  2. CHRONIC - progressive myocardial disease looks like DCM and causes bradyarrhythmias common in older dogs that survive the acute phase

(chronic myocarditis + cardiomegaly)

46
Q

What are 3 ways to diagnose Trypanosomiasis?

A
  1. suspicion based on geography and uncommon breeds developing DCM
  2. antibody titers
  3. identification of trypomastigotes in peripheral blood or amastigotes on myocardial biopsy/necropsy
47
Q

What treatments are used for Trypanosomiasis?

A
  • no known treatment for cardiac signs in dogs
  • supportive care for arrhythmias and CHF
  • Benznidazole may benefit in acute phase
48
Q

What endocrine disease is associated with DCM? How are they related?

A

hypothyroidism —> poor thyroid function can result in systolic dysfunction and LV dilation (minorly!)

DOES NOT CAUSE DCM, but can have an impact in dogs that are already declining in function

  • hypothyroidism AND DCM common in Dobermans, screen for both!

Small Animal Medicine II (57 decks)

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