Revison Session Flashcards
What controls the heart rate?
SNS
What can cause broad ventricular complex?
Bundle beach block (SA node, tachy rate, PR ratio 1:1)
Ventricular ectopic (140 bpm, pacemaker faster then SA node)
Packer originates in the bundle of His due to failure of atrial pacemaker (20-40 bpm, ventricular pacemaker)
What does broad ventricular complex show?
Some of the heart is not depolarising
What does narrow ventricular complex show?
Impulse starts in the atria
Both bundle branches are working
What does a regular rhythm mean?
There is only one pacemaker
What does an irregular rhythm mean?
There are several pacemakers
What is important to remember about absent P waves?
Just because there are no P waves, doesn’t mean there is no atrial beat. Do a 12 lead ECG to make sure
When does a nodal beat occur?
Before the QRS complex
When does a junctional beat occur?
After the QRS complex
What does a long PR interval mean?
There is a change in AV conduction
What are the most common rhythms?
Af, AV blocks and VT
What are the 2 reasons for prolonged PR interval?
- AV node conduction problem (normally diseased) - shown as narrow complex QRS (40-60), treat with atropine to speed up AV node
- 1 bundle branch dead and 1 bundle branch ischeamic, causing conduction to take longer - shown as broad complex QRS. Can lead to full block
What is the key characteristic of 1st degree AV block?
Prolonged PR interval
Narrow complex
What is the cause of 1st degree AV block?
Inferior infarcts
Drugs: adenosine, beta blockers, digoxin
What does 3rd degree AV block normally look like?
Broad complex due to damage in bundle branches and pacemaker below bundle of His Junction
What are the potential causes of 3rd degree AV block?
AV node died (narrow complex)
Both bundle branches died (more complex)
What is the treatment for 3rd degree AV block?
Pace the rhythm
What is the main characteristic of 2nd degree type 1 AV block?
PR interval increases each beat, then the ventricular beat drops, then the sequence repeats
Normally narrow complex
What are the key characteristics of 2nd degree type 2 AV block?
Broad complex due to bundle block, leading to a conduction problem lower down the bundle of His
Normal PR interval meaning AV node is ok
PR ratio = equal distances apart (measure PP interval), >1:1
What does 2nd degree type 2 AV block normally mean?
One bundle branch dead and one diseased which could block any minute
What is the main treatment for 2nd degree type 2 AV block?
Pacing - aim for elective pacing
What are the key characteristics of 3rd degree AV block?
Regular P waves
No PR interval so no PR ratio as the P waves are different every time
Narrow complex = conduction mode failure
Broad complex = higher atrial rate, low pacemaker (bundle branch)
What are the 3 things that mean a rhythm strip can only be sinus rhythm?
- Rhythm starts in the SA node causing an upright P wave
- Rate = 60-170 (higher rate due to low BP and low O2)
- PR ratio = 1:1
What is the treatment for 3rd degree AV block?
Pacing
