Week 9 Flashcards
what are the two common causes for the SA node not working?
- Sick sinus syndrome
- Ischaemia/Infarct
What infarct would effect the SA node?
Inferior
What happens in SA node exit block?
failure of impulse conduction to the atria
Looks like a pause in beat.
Pause lengths are 2 or more of PP interval
What happens in sinus arrest?
impulse formation stops in SA node
- prolonged pause without P wave activity
Pause is unrelated to PP interval
What is a first degree AV block?
delay in conduction of atrial impulse to ventricles
- prolongation of PR interval to >0.2 seconds
- PR interval remains constant
What is a Mobitz I Second degree AV block aka Wenkebach
Intermittent failure - Not a regular failure
PR interval gets longer, longer, longer then QRS drops off completely… then starts back back
What is a Mobitz II Second degree AV block
More likely to produce symptoms
- Generated lower in conduction system - within HIS bundle
Regular P waves
PR interval usually normal
QRS ??????
What is a 3rd degree AV block?
Atrial rate and ventricular rate not associated.
No atrial impulses can be conducted to the ventricles
Occur at level of AV node, bundle of his, bundle branches depending on width of QRS
What happens with excess vagal stimulus?
- bradycardia
- hypotension
How can you reduce parasympathetic stimulation?
- change position
- remove pain
- remove nausea
- patient taking a shit
- patient vomiting
What is atropine?
Main drug for bradycardia
How does atropine work?
Is a muscarinic receptor antagonist. Blocks the effects of Ach on muscarinic receptors - therefore cannot be activated
Works on muscarinic receptors in SA and AV node. If overstimulated you get brady.
What is chronotropy?
Firing rate of SA node
Increased chronotropy means increase HR
What is dromotropy?
Conduction velocity
Increased dromotropy mean the heart is more conductive
What is inotropy?
Force of contraction
