Causes of and Treatments of Cardiac Arrhythmias Flashcards
How are arrythmias subdivided?
Into tachyarrhythmias and bradyarrhythmia’s
How are tachyarrhythmias further divided?
Into supraventricular (originating from the AV junction or above) and ventricular (originating from below the AV junction).
What must be carried out before treating arrythmias?
Record an ECG - need to know the rhythm disturbance
List some cardiac causes of Episodic Weakness / Syncope
- Congenital heart disease (esp. Aortic stenosis, rev. PDA)
- Dilated cardiomyopathy – poor stroke volume
- Hypertrophic cardiomyopathy (cats)
- Cardiac tamponade
- Cardiac neoplasia
- Cardiac arrhythmia: Tachyarrhythmia, Bradyarrhythmia
Compare the appearance of ventricular vs supraventricular tachyarrhythmias on an ECG
Supraventricular = Narrow QRS complexes
Ventricular =
- Wide and bizarre QRS complexes
- T-wave is in the opposite direction of the QRS complexes
Describe the 4 classes of antiarrhythmic drugs
Class 1 = Sodium channel blockers
Class 2 = Beta-blockers
Class 3 = Potassium channel blockers
Class 4 = Calcium channel blockers
How do sodium channel blockers work as anti-arrhythmic drugs, name an example?
Slow upstroke (phase 0) of action potential
Lidocaine
How do beta blockers work as anti-arrhythmic drugs, name an example?
Slows depolarisation
Atenolol
How do potassium channel blockers work as anti-arrhythmic drugs, name an example?
Delays repolarisation, lengthens action potential duration
Sotalol
How do calcium channel blockers work as anti-arrhythmic drugs, name an example?
Act on nodal tissue, SAN or AVN - slow conduction
Diltiazem or Verapamil
Describe the two types of supraventricular tachycardia
Can be paroxysmal (starts and stops abruptly) or
sustained
Compare the ECG of supraventricular tachycardia to atrial fibrillation
Atrial fibrillation is an irregular R-R interval
SVT has a regular R-R interval
Describe the emergency treatment options for a supraventricular tachycardia
- Vagal manoeuvre: physical enhancement of vagal tone at the AV node
- IV Esmolol (beta-blocker)
- IV Diltiazem (calcium channel blocker) - oral diltiazem if no IV preparation
- Oral sotalol also possible (potassium channel blocker)
What is an accessory pathway?
A piece of myocardium that bypasses the AV node, may be one mechanism underlying SVT
Abnormal connection between the atria and ventricles
Name an example of SVT associated with an accessory pathway
Wolff-Parkinson White syndrome
Labradors and Retrievers appear to be predisposed.
Describe the appearance of an ECG in a dog with an accessory pathway/Wolff-Parkinson White syndrome
- Conduction to ventricles across the pathway – short PR interval
- Slurred QRS upstroke called delta wave
What is atrial fibrilation?
A form of supraventricular tachycardia
Requires different treatment
When does atrial fibrillation occur?
Atrial fibrillation can only occur if there is a critical atrial mass (so it is more likely to occur in giant breed dogs, horses and humans).
It occurs in other breeds of dog or even cats if there is marked atrial stretch - this means there is severe structural heart disease