Heart Block Flashcards
What are the main features of Heart Block?
- syncope
- heart failure
- regular bradycardia (30-50 bpm)
- wide pulse pressure
- JVP: cannon waves in neck
- variable intensity of S1
How many type of heart block are there?
Three
What is First degree heart block due to?
Delayed atrioventricular conduction through the AV node
What does every atrial impulse lead to in first degree heart block?
Ventricular contraction
What length will the PR interval be in someone with first degree heart block?
> 0.2 seconds
What is second degree heart block due to?
Some of the atrial impulses do not make it through the AV node to the ventricles.
How many types of second-degree heart block are there?
Two
What are the two types of second-degree heart block?
Mobitz I
Mobitz II
What is another term for Mobitz I?
Wenckebach phenomenon
What is Mobitz I?
Progressive prolongation of the PR interval until a dropped beat occurs
What is Mobitz I due to?
Atrial imputes becomes gradually weaker until it does not pass through the AV node.
What does Mobitz I result in?
Absent QRS complex after a P wave (no ventricular depolarisation)
What is Mobitz II?
PR interval is constant but the P wave is often not followed by a QRS complex
What is Mobitz II due to?
Intermitted failure or interruption of AV conduction.
What does Mobitz II result in?
This results in missing QRS complexes
PR interval is constant
What is there a set ratio of with Mobitz II?
A set ratio of P waves to QRS complexes
(e.g. 3 P waves to each QRS complex would be referred to as a 3:1 block)
What is there a risk of with Mobitz II?
Asystole
What is third degree heart block also known as?
Complete heart block
What is the main characteristic of third degree heart block?
No association between the P waves and QRS complexes
What is there a significant risk of with third degree heart block?
Asystole
