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Equine Medicine > Equine Cardiac Arrhythmias > Flashcards

Equine Cardiac Arrhythmias Flashcards

1
Q

What is the most common cardiovascular cause of poor performance? In what horses is it most common?

A

atrial fibrillation (ALWAYS PATHOLOGIC)

large breeds —> Warmbloods, Thoroughbreds
(not commonly seen in ponies)

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2
Q

What is atrial fibrillation?

A

multiples points in the atria are sending out impulses, which overtake the rhythm of the sinoatrial node

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3
Q

What are the 2 most common causes of poor performance in horses with atrial fibrillation?

A
  1. unable to efficiently push blood to ventricles during diastole
  2. disproportionately high heart rate at exercise makes the horse fatigue more quickly
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4
Q

How does atrial fibrillation affect horses at rest?

A

often tolerated at rest

  • causes increased heart rate during exercise (walk, trot, gallop)
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5
Q

What is seen on physical exam in horses with atrial fibrillation?

A
  • variable pulse quality
  • irregularly irregular rhythm on auscultation and pulse palpation (chaotic!)
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6
Q

What are 2 characteristics of atrial fibrillation on ECG?

A
  1. P waves replaced by F waves that are randomly at different shapes and amplitudes
  2. irregular R-R interval with consistent QRS complexes
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7
Q

What is most commonly seen on cardiac ultrasounds in patients with atrial fibrillation? What laboratory tests are most commonly done?

A

enlarges atrial diameter and inefficient contractions

  • CBC/chem: inflammation, electrolytes
  • fractional excretions
  • cardiac enzymes
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8
Q

What drug is associated with causing atrial fibrillation?

A

Furosemide —> diuretic that decreases potassium

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9
Q

When is treatment for atrial fibrillation done? How does signalment determine affect treatment?

A

if AF is present for >48-72 hours and a full cardiac exam was performed to search for causes

  • easier to defibrillate younger horses
  • if horses are only on pasture, it may not be necessary to treat since it is well tolerated at rest
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10
Q

How is atrial fibrillation medically managed? What are 7 associated side effects?

A

Quinidine sulfate by NG tube

  1. congestion/edema of mucous membranes
  2. colic
  3. ataxia
  4. laminitis
  5. urticaria
  6. tachycardia
  7. collapse/sudden death
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11
Q

What factors are considered before treatment for atrial fibrillation?

A
  • HISTORY: duration of fibrillation
  • PE: HR at rest
  • ECG: presence/absence of other arrhythmias
  • US: enlarged atrium
  • effect of exercise
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12
Q

What alternative treatment is available for atrial fibrillation?

A

transvenous electric cardioversion, where electrodes are placed in the pulmonary artery and atrium and deliver electric shocks

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13
Q

What is atrial premature contraction?

A

one random point in the atria makes its own impulse, which overpowers the sinoatrial node, causing contraction of the atria before they are ready

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14
Q

What are the most common consequences of atrial premature contraction?

A

depends on underlying cause and number of APCs

  • none
  • exercise intolerance
  • atrial fibrillation
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15
Q

What is heard on auscultation in patients with atrial premature contraction?

A

irregularly irregular rhythm where the regular rhythm is interrupted by a premature beat

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16
Q

What 2 things are observed on ECGs in patients with atrial premature contraction?

A
  1. ectopic premature P causes shortened P-P or R-R intervals
  2. normal QRS morphology
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17
Q

What are some signs of physiologic atrial premature contractions?

A
  • rare at rest
  • vanishes with exercise
  • rare after exercise
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18
Q

What are 5 signs of pathologic atrial premature contractions? How is it treated?

A
  1. frequent at rest
  2. with episodes of tachycardia
  3. poor performance
  4. leads to fibrillation or flutter
  5. with other signs of cardiac disease

rest are corticosteroids

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19
Q

What causes sinus arrhythmia? Where does it originate?

A

changes in vagal tone (not common in horses)

SA node

20
Q

When is the appearance of sinus arrhythmia most common?

A
  • frequent, transient
  • most commonly seen AFTER exercise, with a heart rate of 130-150 bpm
21
Q

What is heard on auscultation in patients with sinus arrhythmia?

A

cyclic irregularity that disappears with exercise

22
Q

What is seen on ECGs in patients with sinus arrhythmia?

A

cyclic changes in R-R interval, with normal QRS complexes

23
Q

How are HR, exercise, and clinical signs affected by physiologic AV blocks?

A
  • HR = low at rest
  • block disappears with exercise
  • no clinical signs

commonly physiologic in athletic horses, there is an advantage to having a slow resting HR and being able to ramp it up during exercise

24
Q

How are HR, exercise, and clinical signs affected by pathologic AV blocks?

A
  • HR = inappropriately low
  • block persists with exercise
  • exercise intolerance, ataxia, syncope, collapse, unexplained trauma
25
Q

What is the most common etiology of second degree AV blocks? Where does it originate?

A

high vagal tone, common in athletic horses (most commonly disappears with exercise)

partial conduction at AV node

26
Q

What is the most common physiologic arrhythmia in horses?

A

second degree AV block

27
Q

What is heard on auscultation in patients with second degree AV blocks?

A
  • regularly irregular rhythm with slow to normal HR
  • diastolic pause where S4 is audible
28
Q

What is characteristic of ECGs of second degree AV blocks?

A

not every P wave if followed by QRS complexes —> normal propagation in atrium, but AV node doesn’t let it through

  • QRS complexes are normal and preceded by P waves
  • disappears with exercise
29
Q

What is an advanced second degree AV block? Complete block?

A

numerous P waves without QRS complexes

dissociation between atria and ventricles

30
Q

What are 4 treatment options for second degree AV blocks?

A
  1. treat primary cause or disease
  2. sympathomimetics (vagolytics)
  3. glucocorticoids
  4. temporary or permanent transvenous pacemaker
31
Q

What is ventricular premature contraction? What consequences are associated?

A

one random point in the ventricle makes its own impulse, causing ventricles to contract before they are ready

  • none
  • exercise intolerance
  • collapse
32
Q

What is heard on auscultation in patients with ventricular premature contraction?

A
  • HR normal or tachycardia
  • irregularly irregular rhythm (not as chaotic as A fib)
33
Q

What are 2 characteristics of ECGs in ventricular premature contraction?

A
  1. shortened QRS intervals not preceded by P waves
  2. followed by compensatory pause to protect the heart from other impulses
34
Q

What is characteristic of physiologic ventricular premature contraction? Pathologic?

A

rare at rest, vanishes with exercise, or rare after exercise

  • frequent at rest
  • with episodes of tachycardia
  • poor performance
  • leads to ventricular tachycardia
  • other signs of cardiac disease
35
Q

What is characteristic of ventricular tachycardia on ECG? What is heard on auscultation?

A

> 4 successive ventricular premature contractions

rapid (ir)regular rhythm with cardiac sounds of variable intensity

36
Q

How does the type of ventricular tachycardia affect prognosis?

A

uniform > multiform > R on T > Torsades > fibrillation

37
Q

What are 5 treatment options for ventricular tachycardia?

A
  1. lidocaine
  2. quinidine
  3. magnesium sulfate
  4. phenytoin
  5. propanolol
38
Q

Exercise ECG:

A

increased HR causes P waves to not be seen —> may not be pathologic, software is used to determine changes

39
Q

What is seen on this ECG?

A

AV block

  • irregular P waves not followed by QRS complexes
  • sudden drop in HR to 32
40
Q

What is seen on this ECG?

A

atrial fibrillation

  • F waves
41
Q

What is seen on this ECG?

A

2 VPCs

  • narrow and tall QRS complexes
42
Q

What is seen on this ECG?

a. second degree AV block
b. ventricular premature contraction with compensatory pause
c. atrial fibrillation
d. atrial flutter

A

C - F waves + irregular spacing between QRS complex

43
Q

A regularly irregular rhythm at rest most likely corresponds to which arrhythmia?

a. sinus arrhythmia
b. second degree AV block
c. third degree AV block
d. sinoatrial block

A

B - usually irregular

(A fib is irregularly irregular)

44
Q

What is the most common pathologic arrhythmia in horses?

a. atrial tachycardia
b. premature supraventricular contraction
c. atrial fibrillation
d. second degree AV block

A

C - persists and affects performance

45
Q

What are some factors that you should assess before treating horses with atrial fibrillation?

A
  • HISTORY: knowing when it started, prior episodes
  • SIGNALMENT: young horses easier to treat
  • PE: normal HR at rest

Equine Medicine (33 decks)

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