AV block Flashcards
True or false: In first degree heart block, every P is followed by QRS
True
How long in the PR interval in AV block?
200ms +
In first degree heart block, there is delayed conduction through the…
AVN
What drugs can cause AV block?
Beta-blockers, CCBs or digoxin can block AVN conduction
What characterises second degree heart block?
Some P waves are not followed by QRS complexes
Second degree heart block is where some atrial impulses don’t make it through the ___ to the ventricles
AVN
What are the types of second degree heart block?
Mobitz I and Mobitz II
Describe Mobitz type I pattern of AV block
Progressive PR prolongation until a QRS is dropped
What can cause Mobitz I AV block?
Certain drugs (Beta-blockers, CCBs and digoxin)
An inferior MI
What is treatment for Mobitz I AV block?
No treatment unless v symptomatic eg syncope
Then pacemaker
Describe Mobitz II pattern of AV block
PR interval is consistently prolonged (not progressively enlarging) with random dropped QRS
What can cause Mobitz II AV block?
Drugs (beta-blockers, CCBs, digoxin)
Inferior MI
Rheumatic fever
What are symptoms of Mobitz II AV block?
Syncope
SOB
Chest pain
What is treatment for Mobitz II AV block?
Pacemaker
What is third degree AV block called?
AV dissociation (complete heart block)
What is the relationship between P waves and QRS complexes in third degree heart block?
No relationship
Significant risk of asystole (flat-lining)
Describe what is happening in third degree heart block
The atria and ventricles beat independently of each other.
Ventricular escape rhythm sustains heartbeat.
What happens in the ventricular escape rhythm?
The SAN is dysfunctional so AVN takes over but is also dysfunctional so ventricular pacemakers take over with poor firing rate of 20-40 bpm
What can cause third degree/complete heart block?
Acute MI
Hypertension
Structural heart disease
What is the treatment for third degree/ complete heart block?
IV atropine and permanent pacemaker
Atropine in third degree heart block is an a______ medication and works by inhibiting the ______ _______ ______
antimuscarinic
Parasympathetic nervous system
(Side effects include pupil dilation, dry mouth, urinary retention and constipation)
When else is atropine used?
Pesticide poisoning
Also used to treat a slow heartbeat or those at risk of asystole
Can be used to reduce saliva and fluid in respiratory tract during surgery
