Equine Murmurs

Question 1

What is the most common physiologic murmur of the horse?

Answer 1

Grade III/VI or less left heart base systolic ejection murmur

Question 2

What is the most common congenital cardiac defect in foals?

Answer 2

Ventricular septal defect

Question 3

What is the murmur associated with VSD?

Answer 3

III-IV/VI coarse, band shaped, pan-systolic murmur

Question 4

What is the most sensitive and specific diagnostic test for VSD?

Answer 4

2D echo

Question 5

What is the murmur associated with PDA?

Answer 5

Grade III-IV/VI continuous murmur over left heart base

“Machinery Murmur”

Question 6

When is the ductus arteriosus normally closed in horses?

Answer 6

within first 72-96 hours of birth

Question 7

What is the closure of the DA triggered by?

Answer 7

increased arterial O2 tensions and decreased flow

Question 8

T/F: Valvular insufficiency in the horse can occur both in the presence and absence of cardiac pathology

Answer 8

TRUE

Question 9

What is the most frequent cause of mitral valve insufficiency?

Answer 9

Degenerative changes to valve

Question 10

What is the most common site for bacterial endocarditis in equine?

Answer 10

Mitral valve

Question 11

What are CS associated with aortic insufficiency?

Answer 11

N/A-typically asymptomatic

Question 12

What is the most common murmur identified in national hunt horses?

Answer 12

Tricuspid insufficiency

Question 13

What are the most commonly affected valves for vegetative endocarditis?

Answer 13

Mitral and aortic

Question 14

What are the common bacterial isolates found in vegetative endocarditis?

Answer 14

Strep spp., Actinobacillus equuli, Escherichia coli

Question 15

What is the minimum time frame for treating vegetative endocarditis?

Answer 15

4-6 weeks

Question 16

What are the initial Ab used for vegetative endocarditis and then common secondary Ab?

Answer 16

K-pen IV and gentamicin

Cefotaxime, rifampin and TMS

Question 17

What are anti-inflammatory drugs used in vegetative endocarditis?

Answer 17

phenylbutazone or flunixin meglumine

Question 18

What are four causes of CHF in horses?

Answer 18

Myocardial dysfunction, acquired valvular dysfunction/disease, pericardial effusion, congenital cardiac disease

Question 19

What is the most common type of heart failure in the horse?

Answer 19

Volume overload resulting in progressive ventricular dilatation

Question 20

What is dilatation?

Answer 20

Increase in myocardial cell number and length

Question 21

An increase in afterload leading to increase in myocardial cells laid in parallel fashion is known as what?

Answer 21

Pressure overload

Question 22

What is a cause of pressure overload?

Answer 22

semilunar valvular stenosis (rare)

Question 23

T/F: In a failing heart, increases in filling increases the stroke volume

Answer 23

FALSE- when filling is increased it DOES NOT increase SV

Question 24

T/F: Horses typically have CS of both R&L sided CHF?

Answer 24

True

Question 25

What are three goals of CHF treatment in equine?

Answer 25

1. improve tissue perfusion=increase CO 2. promote excretion of excess fluids 3. maintain oxygenation

Question 26

What is the most common positive inotrope used in horses?

Answer 26

Digoxin- inhibits Na/K/ATPase resulting in increase in intracellular Na and increase intracellular Ca Dose dependent

Question 27

What are factors predisposing a horse to digoxin toxicity?

Answer 27

decreased plasma protein binding, hypokalemia/hypomagnesemia, dehydration, renal disease

Question 28

What is the treatment for digoxin toxicity?

Answer 28

Fab antidigoxin antibodies

Question 29

What does dobutamine do and when is it typically used?

Answer 29

Increases contractility--> Inc. SV | Used w/ septic shock in foals and for horses with acute failure temporarily

Question 30

What is the MOA of furosemide?

Answer 30

inhibits Na, K and Cl reabsorption in ASCENDING LOOP of Henle-increasing excretion of electrolytes and water

Question 31

What is the more potent form of furosemide?

Answer 31

Bumetamide

Question 32

What are some bacterial, viral and parasitic causes of myocarditis?

Answer 32

Bacterial- slmonella and clostridium Viral- influenza, EVA, EIA, AHS Parasitic- Strongylosis and borrelia burgdorferi

Question 33

What is a nutritional cause of myocarditis?

Answer 33

Vit E/Se

Question 34

What are the three forms of pericarditis?

Answer 34

Effusive Constrictive Effusive-constrictive

Question 35

What are causes of effusive pericarditis?

Answer 35

Trauma, inflammation, neoplasia and idiopathic (most common)

Question 36

Fibrinous pericarditis is also known as what form of pericarditis?

Answer 36

Constrictive pericarditis

Question 37

What is the HR in effusive pericarditis vs. constrictive pericarditis?

Answer 37

Effusive: 50-80 Constrictive: 60-100

Question 38

Severity of CS in effusive pericarditis are directly linked to what?

Answer 38

absolute amount of fluid present and rate of accumulation

Question 39

Why is venous return impaired through the cardiac cycle of a patient with effusive pericarditis?

Answer 39

Decreased diastolic filling due to decreased myocardial stretch leading to decreased SV and force of contraction

Question 40

Explain why there is a decreased CO in a patient with constrictive pericarditis?

Answer 40

Initial diastolic fillin is unimpaired, but when critical volume is reached expansion is restricted and filling ceases abruptly, resulting in decreased preload --> decreased CO

Question 41

Ingestion of a new batch of hay or grain is typical of this

Answer 41

Ionophore toxicity

Question 42

What is contraindicated in inophore toxicity?

Answer 42

Digoxin Both digoxin and inophores cause Ca influx- they work together when both given and lead to cell death and myocardial necrosis