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Equine Med and Surgery II > Lecture 11: Approach to Cardiovascular Disease of the Horse > Flashcards

Lecture 11: Approach to Cardiovascular Disease of the Horse Flashcards

1
Q

Horses heart have a high resting vagal tone- what does that mean

A

high parasympathetic tone, little to no sympathetic tone at rest

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2
Q

horses high vagal tone predisposes them to __

A

arrhythmias

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3
Q

benign, vagally mediated arrhythmias should disappear during ___

A

exercise

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4
Q

what is a common sample of a vagally mediated arrhythmia that should disappear with exercise

A

2nd degree AV block

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5
Q

What is normal HR

A

26-50bpm

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6
Q

what is max HR during exercise

A

220-240

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7
Q

Horses have extensive ___branching that results in simultaneous depolarization of ___

A

purkinkje fiber branching, ventricles

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8
Q

QRS complex only useful for deterring __ and ___

A

rate and rhythm

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9
Q

T of F: QRS complex gives you info on size and ectopic focus

A

false

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10
Q

__-___ heart sounds can be auscultated in normal horse

A

2-4

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11
Q

what are the 4 heart sounds and which ones do you always hear

A

S1- AV valve closure (lub)
S2- semilunar valve closure (dub)
S3- ventricular filling
S4- atrial systole

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12
Q

what is a murmur

A

abnormal heart sound

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13
Q

if you have a murmur between S1 and S2 what type of murmur is it

A

systolic murmur

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14
Q

if you have a murmur between S2 and S3 what type is it

A

diastolic murmur

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15
Q

what 4 things do you characterize a murmur by

A

timing, shape, point of maximal intensity, intensity level

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16
Q

diastolic decrescendo murmur/ aortic regurgitation is common in ___

A

older geriatric horses

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17
Q

PDA is common in __

A

newborn foals

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18
Q

what is a grade 1 heart murmur

A

soft and not easily heard, localized

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19
Q

what is a grade 2 heart murmur

A

soft but easily heard, heard consistently over PMI

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20
Q

what is a grade 3 heart murmur

A

moderate intensity, heard immediately and consistently, small area of radiation

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21
Q

what is a grade 4 heart murmur

A

loud, audible over a wide area, no palpable thrill

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22
Q

what is a grade 5 heart murmur

A

loud, radiating, and with palpable thrill

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23
Q

what is a grade 6 heart murmur

A

loud with palpable thrill and audible with the stethoscope held slightly away from chest wall

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24
Q

what are some indications for performing an ECG

A
  1. Murmur
  2. Poor performance/ exercise intolerance
  3. Syncope
  4. Weakness
  5. Significant electrolyte imbalances
  6. Unexplained bradycardia or tachycardia
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25
Q

where are the leads placed for base-apex ECG

A

black lead- left fifth ICS at level of olecranon
Red lead- right jugular furrow 2/3 of the way from the mandible and thoracic inlet
White lead- right shoulder

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26
Q

what do P waves indicate, and what heart sound

A

atrial depolarization, S4: atrial systole

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27
Q

What does QRS indicate and what heart sound

A

ventricular depolarizaztion, S1 AV valve closure

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28
Q

what does the T wave indicate and what heart sounds

A

ventricular depolarization, S2 semilunar valve closure followed by S3 ventricular filling

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29
Q

normal or abnormal- identify problems if present
Red line is 10 seconds

A

Normal sinus rhythm

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30
Q

normal or abnormal- identify any problems- red line= 10 seconds

A

Sinus bradycardia: Atrial and ventricular rats <24

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31
Q

normal or abnormal, identify any problems. Red line = 10 seconds

A

Sinus tachycardia. Atrial and ventricular rates= 90

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32
Q

normal or abnormal- identify any problems. Red line =10 seconds

A

2nd degree AV block- no all P waves followed by QRS complex

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33
Q

are 2nd degree AV blocks always pathological?

A

no- they may disappear with exercise

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34
Q

normal or abnormal- identify problems if any. Red line= 10 seconds

A

Atrial fibrillation

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35
Q

are atrial fibrillations always pathological

A

yes

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36
Q

normal or abnormal- identify problems if any. Red line= 10 seconds

A

missing complex- problem with SA node
Dx: sinus block and sinus bradycardia

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37
Q

How do you measure atrial rate on ECG

A

count p waves over 10 seconds then multiply by 6

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38
Q

how do you measure ventricular rate on ECG

A

count QRS complex over 10 seconds and multiply by 6

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39
Q

what does an echocardiography tell us/measure

A
  1. Chamber size
  2. Wall thickness
  3. Valves
  4. Hemodynamics
40
Q

what are some indications for cardiac work up in athletic horse

A
  1. Non-physiologic arrhythmia
  2. Murmur that increases in intensity over time
  3. 3/6 heart murmur with mitral or aortic regurg
  4. 4/6 heart murmur with tricuspid regurg
  5. Congenital heart disease (VSD)
  6. Continuous or systolic- diastolic murmurs
  7. Signs of myocardial disease
  8. Signs of CHF
41
Q

horses with what conditions (3) should not be ridden

A
  1. Signs of CHF
  2. Signs of pulmonary hypertension
  3. Complex ventricular arrhythmias
42
Q

a “lone” a-fib refers to an “a-fib” with no __

A

underlying cardiac disease

43
Q

a-fib clinical signs only noted during __

A

strenous exercise

44
Q

what is the likely cause of A-fib

A

random re-entry mechanism

45
Q

how does a normal heart prevent re-entry mechanism

A

impulse generated and travels then refractory period occurs and impulse dies and another one can’t be regenerated

46
Q

describe how re-entry occurs when the “path is longer”/heart is bigger

A

by the time the impulse returns to the heart, the refractory period has ended, impulse transmitted again

47
Q

describe how re-entry occurs when an impulse travels slowly/slow heart rate

A

by the time the impulse returns the refractory period has ended, impulse transmitted again

48
Q

what is the tx/protocol for atrial fibrillation

A
  1. ECG to confirm rhythm
  2. Echo to assess structure and hemodynamics
  3. Cardioversion
49
Q

what is the drug of choice for cardiac conversion during A-fib

A

quinidine sulfate

50
Q

What is quinidine sulfate and how does it work

A

class 1a anti-arrhythmic
Blocks fast sodium channels, increase duration of action potential and lengthen effective refractory period

51
Q

how do you administer quinidine sulfate and what dose and when do you stop

A

22mg/kg q2hr via nasogastric tube until
1. Conversion to sinus rhythm
2. Development of toxic side effects
3. Max 6 doses

52
Q

what drug may be useful for short duration a-fib <2 weeks

A

quinidine glaucoma the

53
Q

if a patients heart rate is greater than 60 with A-fib treat first with __

A

digoxin

54
Q

With a-fib, digoxin is indicated to slow to slow ventricular rate < 60bpm prior to __therapy

A

quinidine

55
Q

how does digoxin work

A
  1. Positive ions trope- inhibition of Na/K ATPase- increase contractility
  2. Negative chronotrope- increases vagal tone
56
Q

valvular heart disease is secondary to __, ___, ___, __

A

infection, inflammation, degenerative disease, trauma

57
Q

what are the most common organisms cultured from valvular heart disease

A

actinobacillus, streptococcus

58
Q

__valve disease is the most common cause of HF in horses

A

mitral valve disease

59
Q

Aortic insufficiency very common in __

A

older horses

60
Q

18yr old Arabian gelding presented with depression, breathing very hard, P=64, R=48, grade 5/6 heart murmur, crackles on thoracic auscultation. The following ECG and echo were obtained- what is wrong

A

ECG: sinus tachycardia
Echo: ruptured chordae tendinae of mitral valve

61
Q

what are some appropriate treatments for CHF

A
  1. Digoxin
  2. Diuretics/ furosemide
  3. ACE inhibitors- benazepril
62
Q

what are the appropriate tx for myocardial disease

A
  1. Gastric lavage, absorbants
  2. Corticosteroids
  3. Antibiotics
  4. Rest
  5. Management of HF
63
Q

ionospheres are commonly added to cattle feed to prevent coccidiosis, toxic to horses at __% of cattle dose

A

10%

64
Q

ionophore toxicity affects what

A

cardiac myocytes, myonecrosis

65
Q

ionophore toxicity decreases __ function

A

systolic function

66
Q

what are some clinical signs of ionophore toxicity

A

weakness, sweating, colic, tachycardia, tachypnea, muffled heart sounds, arrhythmias

67
Q

t or f: ionophore toxicity is often fatal

A

true

68
Q

what is tx for ionophore toxicity

A

activated charcoal, supportive care

69
Q

what are cardiac troponins

A

molecules of contractile mechanism in skeletal, cardiac muscle

70
Q

troponins complex are made up of __, __, __ proteins

A

I, T, C proteins

71
Q

cardiac troponins (cTnI) often measure in horses with __

A

myocardial damage

72
Q

what are some causes of pericardial disease

A

infectious, immune mediated, neoplastic

73
Q

what is the most common bacteria isolated in pericardial disease

A

actinobacillus equuli

74
Q

what is tx for pericardial disease

A

pericardiocentesis, pericardial lavage, antibiotics, supportive care

75
Q

what is prognosis for pericardial disease caused by actinobacillus equuli

A

guarded prognosis

76
Q

what is tx for pericardial disease caused by actinobacillus equuli

A
  1. Hospitalization
  2. Long term antibiotics- ampicillin and rifampin
  3. Supportive care
77
Q

aortic root rupture results in ___

A

sudden death

78
Q

what is classic presentation of aortic root rupture

A

older breeding stallion

79
Q

aortic root rupture occurs in higher incidence in what breed

A

friesian horses

80
Q

you are the owner of a successful racetrack practice. Speedy, a 4 years old thoroughbred stallion, presents with a history of decreased performance in his last few races. On your initial physical exam you find temperature of 100.2 F, respiratory rate of 20, heart rate of 52 and a heart rhythm that was irregularly irregular.

What is most likely cause:
A. Ventricular tachycardia
B. Ventricular fibrillation
C. Atrial fibrillation
D. 2nd degree AV block

A

C. Atrial fibrillation

81
Q

you are called out to do a wellness visit on 28yr old Morgan gelding, Tex who spends time as a pasture ornament. In the course of your physical exam you note a heart rate of 44 and grade 2/6 diastolic decrescendo murmur at the left fourth intercostal space

Which of the following do you tell the client:
A. Its a tricuspid insufficiency, recommend an echo
B. It’s mitral valve insufficiency, recommend an ECG
C. It’s pulmonary stenosis, recommend an echo
D. It’s aortic regurgitation, recommend a recheck at next visit

A

D

82
Q

dx ECG

A

Sinus bradycardia- every P wave followed by QRS but HR <26bpm

83
Q

dx ECG

A

Sinus Tachycardia- every P wave followed by QRS, but HR >50bpm

84
Q

dx ECG

A

sinus arrhythmia- RR intervals irregular, but every P wave followed by QRS

85
Q

dx ECG

A

sinus block- RR interval equal to 2 normal RR intervals

86
Q

dx ECG

A

atrial premature contraction- P wave occurs prematurely and followed by normal QRS-T complex

87
Q

dx ECG

A

atrial fibrillation- P waves absent, f-waves present. Normal QRS but RR intervals irregular

88
Q

dx ECG

A

2nd degre AV block- P wave not followed by QRS complex

89
Q

dx ECG

A

Third degree AV block- no relationship between P waves and QRS, PP intervals regular. First QRS complex is escape beat

90
Q

dx ECG

A

Premature ventricular contraction- no P wave before QRS. T wave is positive deflection. Short RR interval. also 2nd degree AV block following

91
Q

Dx ECG

A

Ventricular tachycardia- two VPCs followed by normal P-QRS-T

92
Q

dx ECG

A

Ventricular fibrillation- no normal QRS or T-waves

93
Q

dx ECG

A

Muscle tremor causing sharp narrow deflections

94
Q

dx ECG

A

ECG during exercise- T waves are large and in opposite polarity to QRS, P waves no longer visible as they are incorporated in preceding T waves

95
Q

if the SA node doesn’t fire what is missing from ECG

A

p wave

96
Q

if AV node doesn’t conduct what is missing from ECG

A

QRS

Equine Med and Surgery II (15 decks)

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