Dysrhythmias and poor performance Flashcards
1
Q
Equien HR?
A
Resting: 2-42bpm
Can raise to 240 in exercising thoroughbred
Trot up to 140 in normal horse
2
Q
when are dysrrhymias often seen?
A
during cool down when parasympathetic tone is highest
3
Q
Common types of dysrhythmia?
A
4
Q
When to investigate dysrhythmias?
A
- Vetting – always listen at rest prior to examination, straight after exercise and
during cooldown. - Heart rate or rhythm disturbance is detected by auscultation (often as part of a
routine clinical examination) - Relevant clinical signs of cardiac disease (CHF, oedema, cough)
- Client concerns
- Poor performance
- Collapse
5
Q
How do we invesitgate?
A
ECG
6
Q
How do we do ECG diagnostic?
A
- Exercising ECg often to decide if horse is at risk
- need to reach max exercise depending on breed and rq work
7
Q
What does a normal equine ECG look like?
A
o P wave: large atria, often bifid
o QRS Complex: variation common
o T wave: changes during exercise
o PR interval
o RR interval
8
Q
DESCRIBE 2nd ° Av block
A
o Common in fit/athletic horses at rest
o Due to high vagal tone
o Disappear with exercise/excitement or atropine administration
9
Q
What primary cause of dysrhythmias?
A
isolated electrical disturbance
10
Q
2ary causes of dysrhythmias?
A
- Structural heart disease
- Metabolic and endocrine disorders
- Systemic inflammation
- Hypotension, haemorrhage, anaemia and ischaemia
- Autonomic influences
- Toxicosis
- Drugs
11
Q
Describe Atrial Fibrillation
A
o The most common cardiac dysrhythmia in horses
o Can be associated with poor performance and exercise intolerance
o Caused by irregular depolarization of the atrial myocytes
12
Q
Clinical signs of AFib?
A
- Irregularly irregular rhythm -> intermittent long pauses with rapid runs
- Maybe no CLs
- Exercise intolerance (without cardiac structure change Afib will only affect performance in intense exercise)
- Signs of CHF
13
Q
What are the two classifications of Atrial fibrillation?
A
- Lone atrial fibrillation
- Atrial fibrillation with concurrent cardiac dx
14
Q
Describe lone atrial fibrillation?
A
- Irregular rhythm without evidence of cardiac disease
- Young athletic horses (4.9% of racehorses in Hong Kong)
- Sudden onset exercise intolerance
- Often develops during/immediately afterstrenuous exercise
- Revert to normal rhythm within 24h - 48h with no treatment
15
Q
Describe Atrial fib with concurrent dx?
A
- Elderly horses with loud murmurs of MR
- Moderate to severe resting tachycardia with dysrhythmia: 50 bpm – 100 bpm
- Clinical signs of CHF: exercise intolerance, dyspnoea, oedema, weight loss, collapse
- Need further investigation and treatment
16
Q
Diagnosis of A fib?
A
- PE & Hx
- Irregular heartbeat & pulse - ECg -> definitive diagnosis
- Echocardiography eval of underlying dx)
- Exercise ECG
17
Q
Afib on Echo?
A
- Assess any regurg present?
- Assess structural abn
- Most likely atrial dilation
-> if structural abn -> tx likely unsuccessful
18
Q
Exercising ECg for Afib - do we need to convert?
A
- If severe tachycardia present during exercise they are unsafe to ride as they
are an increased risk of sudden cardiac death - Assess for any ventricular tachycardia
- Must be done prior to commencing any treatment
19
Q
Prognosis for Afib?
A
- HR >60 considered a poor prognostic marker
- Inc atrial flutter rate inc lieklihood of recurrence
- Atrial enlargement => poor prognostic marker
- Duration. foA-fib matters (remodelling of atria!)
- Lone A fib or recent onset = better prognosis
20
Q
Treatement for Afib?
A
- conversion to normal sinus rhythm-> Exmaple: Transvenous electrical cardioversion (TVEC)
21
Q
Describe TVEC?
A
- Widely performed in referral
- Cardioversion catheters placed in pulm artery and right atrium
- Synchronised electrical shock under GA
- Sotalol used prior to and after TVEC
22
Q
Medical tx - Afib?
A
-> Quinidine sulphate
-> Amiodarone
23
Q
Describe quinidie?
A
- Class IA anti-arrhythmic drug
- PO administration via NGT
- Repeat q2h until the rhythm converts to NSR
- Only applied in horses with no systemic illness
- Side effects: colic, diarrhea, tachycardia, urticaria, oedema of nasal mucosa, ventricular arrhythmias
24
Q
Describe Amiodarone?
A
- Class III anti-arrhythmic drug
- IV CRI administration
25
What tx for cases showing signs of CHF at time of diagnosis?
o Supportive care before conversion trial
o Treatments to relieve signs of CHF: diuretics (e.g. furosemide)
o Improve ventricular response to fibrillating atria (e.g. digoxin)
o Conversion to NSR
o Poor prognosis though
26
Summarise approach to A fib?
27
DESCRIBE POST-NSR CONVERSION MONITORING?
- Echo & 24h holter post NSd conversion
- Anti-arrythmic drug (solatol) to prevent recurrence
- Rest -> 4 weeks + periodical auscultation
28
What causes primary tachyarrythmias?
Myocardial dx -> infectious, immune-M, toxic, nutritional, neoplastic ..
29
Tachyarrythmais can also be 2ary to what factors?
* Associated with non-cardiac causes
* Hypoxia (e.g. dynamic airway obstruction in athletic horses)
* Endotoxemia,septicemia, SIRS
* Electrolytes and/or acid-base imbalance
30
Describe Atrial PRemature contractions and wether to worry about them
* On auscultation there will be premature beats interrupting the NSR
* Rarely cause performance issues on their own
Biggest concern:
* Ability to incite a-fibrillation or a-flutter
31
What is Atrial premature contraction associated with?
o Often associated with primary myocardial disease
o Ectopic premature atrial activation
o Abnormal P with normal QRS-T
32
What abnormalities to note with premature atrial contractions?
* Change in P wave morphology
* QRS often normal BUT
* QRS can be wide and biazrre
33
Describe VPCs?
* On auscultation there will be premature beats interrupting the NSR
* Normally a compensatory pause following a VPC
* The abnormal beat will often sound loud
* Wide and bizarre QRS complex
34
What are VPCs associated with and what will we see?
o Often associated with secondary to other causes
o Abnormal QRS-T
o The more complex and variable the VPCs, the higher the risk
35
Management for tachyarrythmias?
o Primary goal istreating the underlying cause
- Often requires steroidal therapy
- Any infections treat those
o Anti-arrhythmic drugs
* Lidocaine and magnesium frequently used
* Beta-blockers can help
* Can consider digoxin if life threatening
36
Prognosis for tachyA?
* If lone VPC that is obliterated during exercise risk is small
* If occurring just after exercise can be associated with parasympathetic
tone and normal
* If it occurs in exercise then serious concern
* Only consenting adults should ride these horses
37
Should. urest VPC?
yes at least >6months
38
Describe high degree heart blocks?
o High grade 2º AV block or 3º AV block can result in syncope and collapse
o More frequently seen in donkeys and mules
o Management: pacemaker
