Arrhythmia Information Flashcards
two mechanisms of bradycardia
conduction blocks or reduced automaticity
3 mechanisms of tachycardia
enhanced automaticity
triggered activity
unidirectional blocks and reentries
what arrhythmia results from reduced SA node automaticity
called a junctional escape rhythm and the AV node will likely take over
what will the common ECG of a junctional escape rhythm look like?
you will not have P waves prior to the QRS complex and it will be bradycardia…
Note you can have P waves that follow the QRS complex
why can we sometimes see P waves with a junctional escape rhythm after the QRS?
since atria have not depolarized, when AV node fires it can go backward and make the atria contract
how can non nodal cells lead to tachycardia?
if they somehow are firing at a higher rate than the SA node then they will take over…this is usually due to drugs, injury, ischemia
at what point in action potential can an early afterdepolarization tachycardia occur?
this is right after depolarization so during the repolarization phases of 2 and 3
at what point in action potential can a delayed afterdepolarization tachycardia occur?
this is right after repolarization that it occurs…so start of phase 4
what is the common cause of the delayed afterdepolarization tachycardia?
from increased intracellular calcium inducing the secondary Na/Ca pump that brings Na in and depolarizes the cell again
what is the common cause of early afterdepolarization tachycardia?
usually from drugs/channelopathies that prolong the QT interval of AP in general
how can a conduction block be functional?
if it is due to the refractory period from a previous firing
a block with reentry usually leads to what?
TACHYCARDIA
explain how the bundle of kent in WPW can ultimately lead to reentry of conduction?
so…if you have a slowed AV node, when the AV node eventually fires it could come back through the accessory pathway or bundle of kent and stimulate that area that can then go to the AV node which has had enough time to repolarize and you get a cycle
what is it called when you have a reentry pathway in the AV node?
atrioventricular reentry tract…AVRT
what does an AVRT ECG look like? 3 things
- normal and narrow QRS
- no P waves prior to the QRS
- tachycardia
with bradycardia…what two things should we look at on QRS for ECG?
is there grouped beating?
are they coming at normal intervals?
define sinus bradycardia
slowed rate of heart with normal sinus rhythm
common cause of sinus bradycardia
increased vagal tone or increased parasympathetic output
what will ECG of sinus bradycardia look like?
there will be a decrease in rate with normal P…QRS…T waves
what is main characteristic of first degree AV block?
all P waves lead to QRS…but the PT interval is prolonged