Approach to cardiac disease - equine Flashcards
What does a typical QRS look like in horses?
most are negative (positive in small animals) and this is due to where the limb leads are standardly placed.
How does an equine QRS compare with that of a dog? 2
- negative in horse, positive in dog
- similar size (horses have a more extensive purkingje fibre system as they are herbivores versus carnivores).
Why do horses have a double P wave?
horses have very large atria and you have sequential depolarisation across the atrium (if you saw this in dogs you would be very worried about the dog having atrial enlargement as this may precede AF).
Is it normal to have T waves that can be positive or negative?
- normal in horse
- abnormal in dog (changes in the dog indicates myocardial disease because of different routes of reploarisation)
In horses, where is the positive electrode located?
near the heart apex
In horses, where is the negative electrode located?
near the heart base
What is the Earth probe?
you can pt it anywhere
What is the most common lead position for equine ECG work?
Base-apex lead
What is the normal jugular filling time?
20-25 seconds (horse) Prolonged - indicates a problem with left heart output.
What is the jugular pulse height related to?
directly proportional to CVP. Increases in CVP are seen with RCHF.
Why is sinus arrhythmia rarely noticed in horses?
their HR and RR are so slow
How do you assess left-sided heart function? 3
MM, CRT and jugular filling time
How do you assess right sided heart function? 1
jugular pulse
What are your top differentials for an irregularly irregular heart rhythm? 4
APC, VF, AF, 2nd degree AV block.
Describe F waves
far too many present (than P waves), variable size and duration (they take various routes around the artira which varies what the electrodes record)
What do P waves with no QRS suggest?
3rd degree AV block
Define atrial tachycarida
a run of 4 or more P waves together
Name 2 front-line drugs for equine ventricular arrhythmias
lidocaine and magnesium sulphate
What is amiodarone?
an anti-arrhythmic drug commonly used in dogs, has fewer side effects than quinidine. It prolongs the repolarisation phase of the action potential by blocking K channels. It predominantly has class 3 effects but also some properties of all classes.
What is the result of quinidine reducing vagal tone?
immediate effect is to make the refractory period in the AVN shorter. (digoxin makes ventricular rate faster, doesn’t change vagal tone, prolongs refractory period in the AVN)
T/F: you never have an S4 sound in horses with AF.
True
What is a holosystolic murmur?
a sound that fills the space between S1 and S2 but doesn’t obscure the sound of S1 (if S1 is obscured, this is known as a pan-systolic murmur)
What are the features of an aortic flow murmur?
systolic, generally quiet, good differential for LHS murmumr, above heart base
What are the features of mitral regurgitation murmurs?
systolic, heard over the apex
