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Exam 2
Equine Arrhythmias
52
Veterinary Medicine
Professional
02/23/2017

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Cards

Term
Which physiologic changes in cardio are especially important with signalment?
Definition
-murmurs
Term
Which heart sounds do we hear in a horse?
Definition
-four
-always hear first two but can occasionally hear first three
Term
What is S1?
Definition
-sound made by slocure of AV valves
Term
What is S2?
Definition
-sound made by closure of semilunar valves
Term
What is the significance of a marked split S2 in horses?
Definition
-RAO
Term
What is S3? How often is it heard?
Definition
-caused by rapid filling of ventricles
-heard best over cardiac apex about 50% of time
Term
What is S4? When is it heard?
Definition
-caused by atrial contraction
-can be heard in 2nd and 3rd AV block
Term
What is the typical HR for a horse? What changes in how we take it in a horse?
Definition
-26-44 bpm
-listen for at least a minute
Term
True or False: Arrhythmias are less common in horses than any other domestic species.
Definition
-FALSE, most common
Term
When should we perform an ECG in a horse w/ an arrhythmia?
Definition
-any time the arrhythmia does not disappear w/ excitement or exercise
Term
What is the purpose of an ECG?
Definition
-detects rate and rhythm changes: not useful for chamber size
Term
Which ECG do we use in the horse?
Definition
-base-apex
-red net: red on right neck
-white on right: white on right withers
-black heart: black on left side above elbow
-set recorder to lead I
Term
What are the parts of the ECG in a horse?
Definition
-P wave: biphasic due to atrial depolarization
-WRS: ventricular depolarization
-T wave: ventricular repolarization (should be positive)
Term
What is sinus bradycardia?
Definition
-sinus rate < 26 bpm due to high vagal tone at rest
Term
When is sinus bradycardia benign or pathologic?
Definition
-Benign: rate should inc w/ exercse, excitement, parasympatholytics
-Path: assoc w/ severe exercise intolerance and syncope
Term
What does sinus bradycardia look like on ECG?
Definition
-normal complexes just really slow
Term
What is the most common physiologic arrhythmia in the horse?
Definition
=second deg AB block
Term
When is a second deg AV block considered physiologic in the horse?
Definition
-when it goes away w/ dec vagal tone
Term
What does second deg AV block look like on ECG?
Definition
-p wave w/out ARST w/ regular intervals b/n complexes & same pause interval
Term
What is sinus tachycardia? When is it usually seen?
Definition
-sinus rate > 50 bpm
-often seen in nervous or excited horses common w/ underlying dz: sepsis, anemia, shock
Term
What does sinus tachycardia look like on ECG?
Definition
-normal complexes just really fast
Term
How can we differentiate physiologic arrhythmias from pathologic?
Definition
-an ECG at exercise
-arrhythmia in combo w/ other issues is more likely to be pathologic
Term
What is the most common pathologic arrhythmia in the horse?
Definition
-atrial fibrillation
-most common arrhythmia causing poor performance in young athletes
Term
What is the most common presenting complaint w/ atrial fibrillation in horses? Others?
Definition
-exercise intolerance
-others: EIPH, dyspnea, syncope
Term
Can atrial fibrillation be an incidental finding?
Definition
-yes
Term
What does atrial fibrillation sound like?
Definition
-irregularly irregular rhythm
-heart sounds vary in intensity
-lack of 4th heart sound
Term
What does atrial fibrillation look like on ECG?
Definition
-irregular R-R intervals
-lack P waves, have lots of f waves
-variability in QRS-T cplx beat to beat
Term
What are some common causes of atrial fibrillation?
Definition
-electrolyte distrurbances: low K+
-underlying cardiac dz and atrial enlargement
-myocarditis
-idiopathic large atrial size: MOST COMMON
Term
When do we convert atrial fibrillation horse rather than not?
Definition
-if HR < 60 bpm
-short duration of onset
-no hx of myocardial pathology
-no CS of heart failure or structural changes in heart
-risk vs benefit
Term
HOw do we convert atrial fibrillation in the horse?
Definition
-Quinidine
-electrical cardioversion: great but expensive
-make sure whole body K+ is WNL
Term
What is the prognosis of atrial fibrillation in the horse?
Definition
-unwise to recommend working an untreated horse
-recommend exercise tolerance test w/ holter monitoring
Term
What are the signs in horses w/ supraventricular tachycardia?
Definition
-very rapid rate
-significant dec in performance
Term
What are some causes behind equine supraventricular tachycardia?
Definition
-systemic dz
-electrolyte & met disturbances
-myocardial dz
Term
What does supraventricular tachycardia look like on ECG?
Definition
-short but REGULAR R-R intervals
-usually normal QRS-T complexes: can be wide and bizarre w/out visible P waves
Term
How do we treat equine supraventricular tachycardia? Extra precautions?
Definition
-digoxin +/- quinidine
-if together do TDM: qhinidine can inc concentrations of digoxin
Term
What does a 3rd degree block look like on ECG?
Definition
-QRS-T complexes normal or widened
-R-R interval is regular, P waves normal
-P waves not assoc w/ ARS-T complexes
Term
What do VPCs look like on ECG?
Definition
-ARS-T usually bizarre
-T wave in opposite direction of QRS
-followed by a compensatory paus
Term
What do VPCs usually indicate in horses?
Definition
-myocardial dz
Term
When are equine VPCs significant?
Definition
-inc in frequency w/ exercise
-multiform
-R on T
Term
What is equine ventricular tachycardia?
Definition
-4 or more runs of VPCs w/ inc HR
-paraxysmal or sustained
-uniform or multiform
Term
What is equine ventricular tachycardia usually associated w/?
Definition
-assoc w/ severe changes in performance +/- syncope
Term
What is a common cause of V-tach in horses?
Definition
-endurance horses w/ electrolyte abnormalities
Term
What does V-tach look like on ECG?
Definition
-4 or more runs of VPCs
-P waves present but not conducted
-inc HR
Term
When do we treat equine arrhythmias?
Definition
-hemodynamic instability
-exercise intolerance
-poor performance
-heart failure
-dyspnea
-syncope
Term
When do we treat ventricular arrhythmias in horses?
Definition
-SVT that worsens w/ exercise or results in HR > 200 bpm
-rapid SVT or ventrial arrhythmia at rest > 120 bpm
-frequent or multiform ectopic beats
-ventricular arrhythmias more often cause hemodynamic compromise, therefore they are more often treated
Term
How do we treat v-tac in horses?
Definition
-lidocain
-if that fails use MgSO4
Term
What is f-fib?
Definition
-lack of recognizable WRS-T complexes
Term
What are the two more important question for general prognosis?
Definition
-is hte horse suitable for the kind of work for which it will be used?
-is the safety of the rider at risk?
Term
What is the issue with condemning every horse that has a murmur or arrhytmia?
Definition
-unfortunate for a lot of horses
-not an educated approach
Term
What do we use for an exercise tolerance exam in horses?
Definition
-consider ah olter monitor or telemetry during exercise
Term
What are the general guidelines for not recommending work for equine exercise tolerance test?
Definition
-cery frequent premature contractions: guarded prognosis
-marked bradycardia w/ arrhytmia
Term
Wat is the general prognosis for brood mares?
Definition
-if CO is compromised, danger loosing foal & mare late term
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