ECG Arrhythmias Flashcards
What is the term given to a pacemaker cell other than the SAN pacing the heart?
An ectopic pacemaker
Which cells of the heart have the potential to be pacemakers and why?
All of the conduction system cells (SAN through to Purkinje fibres) as they all have phase 4 depolarisation
What are the 2 types of cardiomyopathy?
Dilated
Hypertrophic
Explain first degree heart block.
Long PR interval (>3-5 small squares)
Explain second degree type 1 heart block.
What is its other name?
Increasingly longer PR interval then eventually a missed QRS complex
Weinkeback
Explain second degree type 2 heart block.
What is its other name?
Fixed PR intervals with missed QRS complexes
Mobitz
Explain third degree heart block.
No P and QRS complex relationship (atrioventricular dissociation)
What is a re-entry arrhythmia?
What type of arrhythmia does this usually allow for?
Depolarisation is trapped in one region of the heart whilst adjoining tissue repolarises, making it no longer refractory and able to depolarise again - this usually gives rise to tachyarrhythmias
What can cause adjacent differences in myocardial conduction/refractory rates allowing for re-entry arrhythmias?
Ischaemia, scarring, congenital conditions
What subgroup of heart arrhythmia does AF fall into?
It is a SVT
Which area of heart is usually the ectopic focus of AF?
The cardiac muscle layer at the transitional zone between the left atrium and a pulmonary vein
What is the characteristic ECG of AF?
Fibrillatory ‘f’ waves instead of P waves
Irregularly irregular QRS complexes
Tachycardia (normally >150)
What are the four classes of anti-arrhythmic drugs?
Class 1 = sodium channel blockers = suppress conduction = flecanaide (pill in pocked)
Class 2 = beta blockers = inhibit AVN conduction = bisoprolol
Class 3 = prolong refractory and AP times = amiodarone
Class 4 = calcium channel blockers = inhibit AVN conduction = verapamil
Inhibit AVN = negative chronotropic effect
Adenosine (used for SVT) = slows AVN conduction
Digoxin = stimulates vagus which slows AVN conduction
Which anti-arrhythmic drug classes are not good for VT rhythms?
Why?
Class 2 , 4, adenosine and digoxin
The problem in VT arrhythmia is in the ventricles, therefore below AVN, the above drugs and classes work on the AVN - pointless as acting too high in chain of conduction pathway
What is a gross way of explaining:
1) class 2, 4, adenosine and digoxin
2) class 1 and 3
1) rate controllers
2) rhythm controllers
