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
what is stable bradycardia?
between 50-60 bpm
50 is threshold for management
MICA don’t intervene till HR of 20
What are the two types of pacemakers?
- Fixed rate
- Demand
What is atrial pacemakers
Paces the P waves - seen on ECG where P wave should be
What do look for with pacemaker rhythms on ECGs?
- Failure to sense
- Failure to capture
- Failure to pace
What is ventricular pacemakers
sits on QRS, QRS is initiated by pacemaker
What is a dual capture pacemaker?
Paces both atrial and ventricular
What is failure to sense with pacemakers?
Pacemaker cant sense hearts own electrical pulse. Can lead to inappropriate pacing
What is failure to capture?
When pacemaker fires, but does not generate impulse.
Does not depolarise
What is failure to pace?
SA node fires but pacemaker is not firing
not keeping rhythm
Stops working
What are the implications of pacemakers in STEMI diagnosis?
it’s not possible to diagnose STEMI form ECG in patients with ventricular pacemaker
How many joules are implantable defib?
35-40 joules
leads are biphasic
