Equine Murmurs Flashcards
What is the most common physiologic murmur of the horse?
Grade III/VI or less left heart base systolic ejection murmur
What is the most common congenital cardiac defect in foals?
Ventricular septal defect
What is the murmur associated with VSD?
III-IV/VI coarse, band shaped, pan-systolic murmur
What is the most sensitive and specific diagnostic test for VSD?
2D echo
What is the murmur associated with PDA?
Grade III-IV/VI continuous murmur over left heart base
“Machinery Murmur”
When is the ductus arteriosus normally closed in horses?
within first 72-96 hours of birth
What is the closure of the DA triggered by?
increased arterial O2 tensions and decreased flow
T/F: Valvular insufficiency in the horse can occur both in the presence and absence of cardiac pathology
TRUE
What is the most frequent cause of mitral valve insufficiency?
Degenerative changes to valve
What is the most common site for bacterial endocarditis in equine?
Mitral valve
What are CS associated with aortic insufficiency?
N/A-typically asymptomatic
What is the most common murmur identified in national hunt horses?
Tricuspid insufficiency
What are the most commonly affected valves for vegetative endocarditis?
Mitral and aortic
What are the common bacterial isolates found in vegetative endocarditis?
Strep spp., Actinobacillus equuli, Escherichia coli
What is the minimum time frame for treating vegetative endocarditis?
4-6 weeks
What are the initial Ab used for vegetative endocarditis and then common secondary Ab?
K-pen IV and gentamicin
Cefotaxime, rifampin and TMS
What are anti-inflammatory drugs used in vegetative endocarditis?
phenylbutazone or flunixin meglumine
What are four causes of CHF in horses?
Myocardial dysfunction, acquired valvular dysfunction/disease, pericardial effusion, congenital cardiac disease
What is the most common type of heart failure in the horse?
Volume overload resulting in progressive ventricular dilatation
What is dilatation?
Increase in myocardial cell number and length
An increase in afterload leading to increase in myocardial cells laid in parallel fashion is known as what?
Pressure overload
What is a cause of pressure overload?
semilunar valvular stenosis (rare)
T/F: In a failing heart, increases in filling increases the stroke volume
FALSE- when filling is increased it DOES NOT increase SV
T/F: Horses typically have CS of both R&L sided CHF?
True
What are three goals of CHF treatment in equine?
- improve tissue perfusion=increase CO
- promote excretion of excess fluids
- maintain oxygenation
What is the most common positive inotrope used in horses?
Digoxin- inhibits Na/K/ATPase resulting in increase in intracellular Na and increase intracellular Ca
Dose dependent
What are factors predisposing a horse to digoxin toxicity?
decreased plasma protein binding, hypokalemia/hypomagnesemia, dehydration, renal disease
What is the treatment for digoxin toxicity?
Fab antidigoxin antibodies
What does dobutamine do and when is it typically used?
Increases contractility–> Inc. SV
Used w/ septic shock in foals and for horses with acute failure temporarily
What is the MOA of furosemide?
inhibits Na, K and Cl reabsorption in ASCENDING LOOP of Henle-increasing excretion of electrolytes and water
What is the more potent form of furosemide?
Bumetamide
What are some bacterial, viral and parasitic causes of myocarditis?
Bacterial- slmonella and clostridium
Viral- influenza, EVA, EIA, AHS
Parasitic- Strongylosis and borrelia burgdorferi
What is a nutritional cause of myocarditis?
Vit E/Se
What are the three forms of pericarditis?
Effusive
Constrictive
Effusive-constrictive
What are causes of effusive pericarditis?
Trauma, inflammation, neoplasia and idiopathic (most common)
Fibrinous pericarditis is also known as what form of pericarditis?
Constrictive pericarditis
What is the HR in effusive pericarditis vs. constrictive pericarditis?
Effusive: 50-80
Constrictive: 60-100
Severity of CS in effusive pericarditis are directly linked to what?
absolute amount of fluid present and rate of accumulation
Why is venous return impaired through the cardiac cycle of a patient with effusive pericarditis?
Decreased diastolic filling due to decreased myocardial stretch leading to decreased SV and force of contraction
Explain why there is a decreased CO in a patient with constrictive pericarditis?
Initial diastolic fillin is unimpaired, but when critical volume is reached expansion is restricted and filling ceases abruptly, resulting in decreased preload –> decreased CO
Ingestion of a new batch of hay or grain is typical of this
Ionophore toxicity
What is contraindicated in inophore toxicity?
Digoxin
Both digoxin and inophores cause Ca influx- they work together when both given and lead to cell death and myocardial necrosis
