Cardiology

Question 1

Possible heart sounds in horse

Answer 1

2 to 4
S1 - lub = closure of AV valves
S2 - dub = closure of semilunar valves
S3 - ahh = end of rapid filling phase
S4 - ba = atrial contraction

Question 2

ECG

Answer 2

cannot perform typical vector analysis because Purkinje fibers deeply penetrate myocardium and do not polarize apex to base, more wringing action
Main ECG lead placement is base apex because maximizes depolarization
Normal variants
- notched P wave common
- negative QRS (intervetricular septum depolarization)
- large T wave

Question 3

preferred method of evaluating equine heart

Answer 3

echocardiography

Question 4

normal HR

Answer 4

26-44bpm

Question 5

_______ predominates at rest in the horse

Answer 5

vagal tone

Question 6

ECG lead placement

Answer 6

+ on left thorax
- on right jugular furrow
ground at any point remote form heart

Question 7

Most common PHYSIOLOGICAL arrhythmia in the horse

Answer 7

Mobitz I 2nd degree AV block = Wenkebach

Question 8

Most common pathological arrhythmia in the horse

Answer 8

Atrial fibrillation

Question 9

is Mobitz Type II always pathologic?

Answer 9

yes

Question 10

Presenting complaint of horse with Afib

Answer 10

exercise intolerance (quitting at 3/4post, pulling up)
tachypnea
EIPH
CHF
collapse
myopathy, colic

Question 11

2 forms of Afib

Answer 11

paroxysmal - occurs during race and can disappear with deceleration of the HR
- may be associated with K depletion in horses given furosemide or oral bicarb pre-race

Sustained - easier to Dx because rhythm sustained over long period of time

Question 12

PE of horse with A fib

Answer 12

auscultation - irregularly irregular, sounds like shoe in drier
pulses - variable strength

Question 13

ECG of an Afib horse

Answer 13

baseline fibrillation wavs (F waves) = soars or fine
QRST usually normal morphology but irregularly spaced

NO P WAVES

Question 14

Treatment of Afib

Answer 14

If HR and echo normal –> give Quinidine

If HR high or abnormal echo –> Digoxin then Quinidine

If HF –> don’t Tx the Afib, Tx the HF

Question 15

MOA of Quinidine as Tx for Afib

Answer 15

blocks fast inward Na current in myocardium

Question 16

How do you Tx quinidine toxicity

Answer 16

Tx acute toxicity w. IV sodium bicarbonate

Question 17

Idiosynchratic rxn to quinidine

Answer 17

causes rapid supra ventricular tachycardia

Question 18

Dosing Quinidine

Answer 18

if acute <72h, can use IV
- give small bolus Q 10 min, do not exceed 12mg/kg

More typically, use PO quinidine
can use 5mg test dose, then 20-22mg/kg q2h until converted
stop if toxic side effects, or reach 60g

Question 19

Ventricular tachycardia

Answer 19

associated with metabolic disease

caused by myocarditis, endotoxemia, hypoxia, electrolyte disturbances

Question 20

Clinical signs of VT

Answer 20

exercise intolerance, can lead to syncope

Question 21

Treating VT

Answer 21

LIDOCAINE, bolus or infusion

indicated in sick colicy patients

Question 22

Pathological murmurs in the horse

Answer 22

mitral insufficiency - systolic murmur on L side
aortic insufficiency - diastolic murmur on L side
tricuspid insufficiency - systolic murmur on R side

Question 23

most important murmur in the horse

Answer 23

mitral insufficiency

Question 24

clinical signs of mitral insufficiency

Answer 24

vary depending on severity of valvular dysfunction
most likely valvular dysfunction leading to cardiac failure
mild: exercise intolerance
severe: sudden death, chord tendinae rupture, acute decompensation in failure (most common cause of valvular death in horses)

Question 25

Most common site of bacterial endocarditis?

Answer 25

mitral valve

Question 26

Diagnosing mitral valve insufficiency

Answer 26

LA and LV size, regurgitation fraction, PA size
may hear murmur if severe
may show Afib because enlarged atria

Question 27

most likely to lead to HF

Answer 27

mitral valve insufficiency

Question 28

if have mitral valve insufficiency and chord tendinae rupture, murmur sounds like

Answer 28

honking murmur like geese

Question 29

if pulmonary artery ruptures

Answer 29

sudden death

Question 30

Aortic insufficiency

Answer 30

seen in older horses
noisy musical diastolic murmur, mostly on L side
incidental finding but can lead to failure

Question 31

Prognostic factors of valve insufficiency

Answer 31

type of valvular disease
degree of L sided volume overload
size of regurgitant jet
age of horse

Mitral: size of PA
Aortic: size of aortic root, presence/absence of concurrent L AV insufficiency

Question 32

Vegetative endocarditis

Answer 32

mitral valve more commonly
young horses, males more than females
endothelial damage –> bacteria can adhere –> local clotting activated
CS: fever of unknown origin, tachycardia, murmur, poor doing colic (from ileus from perfusion problems)
Dx: CBC (inflammation), Chem (organ dysfunction from CV compromise), blood culture to isolate organism
Tx: 4-6w of antimicrobials minimum, anti inflammatories (aspirin or flunixin) to help w/ clotting

Question 33

Follow up protocol for endocarditis

Answer 33

blood culture 60d after cessation of antibiotics

at least 3 cultures

Question 34

3 important causes of HF

Answer 34

mitral valve insufficiency
pericarditis
ionophore toxicosis

Question 35

3 forms of pericarditis

Answer 35

effusive - usually viral
constrictive (fibrinous) - usually bacterial, pleuropneumoniae
combined

Question 36

clinical signs of pericarditis

Answer 36

FEVER, edema, distended jugular veins, poor pulses, weakness, listlessness, syncope, acute developing failure

Question 37

Tx pericarditis

Answer 37

Effusive - drainage
Constrictive - pericardectomy

HF drugs
diuretics - furosemide
inotropes - digoxin
ACEi - enalepril
vasodilators - hydralazine