Arrhythmias in LA/Horses Flashcards
What can cause arrhythmias in LAs?
Primary (infectious, nutritional, others e.g. cardiomyopathy, neoplasia, or idiopathic) or Secondary (endotoxaemia, hypoxia, electrolyte or acid-base disturbances)
Would you use an Echo or ECG to tell you about arrhythmias in horses?
ECG used to tell you about cardiac rate and rhythm.
What is second degree AV block?
When the AV node only conducts some of the depolarisations from the atria (i.e. not a QRS for every P)
Why is it normal for horses to have second degree AV block?
They have high vagal tone.
What would you hear/see on an ECG with second degree AV block in horses?
Regularily irregular blocking of the P wave, isolated fourth heart sound wound be heard before block. Usually slow heart rate.
What is atrial fibrillation? What would you see on an ECG?
AF is the commonest pathological arrhythmia in horses. It is caused by no coordinated contraction of the atria, so there is fibrillation. No P waves, but there are fibrillation waves.
What would you hear/see on an ECG with atrial fibrillation in horses?
Irregularily irregular heartbeat with no 4th heart sound. No P waves, only F waves. Usually normal rate.
What clinical signs would you expect with atrial fibrillation?
Often there may be none in horses not very physically activity, may be incidental. May see excercise intolerance in those with a higher work load.
How can you differentiate 2nd degree AV block from AF?
AF is irregularily irregular with no 4th heart sound, no P waves. 2nd degree AV block is regularily irregular with a 4th heart sound, and P waves on ECG. 2nd degree also has slow HR, AF usually normal.
If the owner wants to treat AF, how can it be done in horses? Why is this decision not taken lightly? (Would not usually treat happy hackers)
Quinidine sulphate, considered due to side effects (ventricular tachycardia, hypotension, decreased CO, diarrhoea, can be fatal.
Is it safe to ride a horse with AF?
Some horses with AF may get VPC’s, leading to VF and death. Therefore you ALWAYS do an excercising ECG looking for ventricular abnormalities before saying safe to ride.
What makes a horse with AF a good candidate for treatment with Quinidine sulphate?
No underlying heart disease, going on for less than 4 months, normal heart rate.
What is an Atrial premature complex? How would it look on an ECG?
When atria prematurely contract. It may or may not be conducted by the AVN. It is an abnormal P followed by a normal QRS if conducted, or no QRS if non-conducted.
What is an Ventricular premature complex? How would it look on an ECG? Are the significant?
When the ventricle contracts by itself. It is an abnormal wide and bizarre QRS, with no preceding P wave. Much more likely to progress onto VF and death than APC.
What is Ventricular tachycardia?
When heartbeat starts in ventricle, 3 or more VPC’s. It can me uniform or multiform based on how many different types of VPC’s.
