Arrhythmias Flashcards
(27 cards)
Horses have a very large heart with a huge myocardium. How does this affect vagal tone?
High vagal tone
What is the P wave on an ECG?
Atrial depolarisation
+ contraction, S4
What is the QRS wave on an ECG?
Ventricular depolarisation
+ contraction, S1
What is the T wave on an ECG?
Ventricular repolarisation
+ relaxation, S2
Where does the equine ECG attach to horses?
Left arm (+) - right apex Right arm (-) - mid jugular furrow Neutral - remote from heart
What is the purpose of the P-R segment on an ECG?
Delay impulse at AV node
Prevent synchronous contraction of atria and ventricles
Which part of an ECG wave may be positive or negative?
T wave
QRS normally negative in horse
Which types of AV block are physiological arrhythmias and which are pathological?
1st and 2nd degree AV block = physiological
3rd degree AV block = pathological
Does 2nd degree AV block occur at exercise or at rest?
At rest
AV node stops spread of depolarisation to ventricles every 3-4 beats
Which physiological arrhythmia has no P wave and variable R-R intervals?
Sinus block
Which common physiological arrhythmia has P waves followed by a pause of 2X R-R interval, every 3-4 beats?
2nd degree AV block
Atrial fibrillation may present as poor performance, fading during a race and epistaxis. Why does AF cause epistaxis?
Pulmonary hypertension
Causes EIPH
What is the most common arrhythmia causing poor performance in horses? It is often an incidental finding.
Atrial fibrillation
Atrial fibrillation can be primary/lone AF (without underlying cardiac pathology) or secondary to cardiac pathology. Give an example of a condition that leads to secondary AF
Mitral regurgitation
Causing LA dilation
Is atrial fibrillation a cause of heart failure?
NO
If a case of AF has heart failure, look for underlying cause
Give the 3 clinical signs of heart failure in horses
HR >50bpm
Peripheral oedema
Jugular distension
A horse has had a recent onset of atrial fibrillation in the last 12 hours. What treatment should be performed?
None - may revert to sinus rhythm within 24-48 hours
What are the 2 conversion options for treating atrial fibrillation?
Pharmacological conversion - quinidine
Transvenous electrical cardioversion
Quinidine sulphate is used for atrial fibrillation in horses. How is it administered? What if it is not succesful?
PO - nasogastric tube
Every 2 hours until conversion (maximum of 5 doses)
Prolong treatment interval and add in digoxin if needed - stop if side effects or not converting
When using transvenous electrical cardioversion for atrial fibrillation, when should you NOT give the shock?
T wave - fatal
Regular atrial premature contractions can lead to what other arrhythmia…
Atrial fibrillation
What are atrial premature complexes?
Premature complexes with a different shaped P wave
In general, what does a different shaped P wave suggest?
Atrial contraction originating somewhere other than SAN
In general, what does a different shaped QRS or T suggest?
Ventricular contraction originating somewhere other than AVN
