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
what is the characteristic feature of second degree AV block moritz type I? AKA wenkebach
the PR intervals following P waves gradually increase and then eventually a P wave is not followed by a QRS
what is the characteristic feature of second degree AV block moritz type II?
PR intervals are the same length or fixed and eventually lead to a dropped QRS complex
what is the characteristic feature of 3rd degree AV blocl?
regular P waves and regular QRS complex…but P waves are not associated with the QRS at all!
in second degree mobitz type I where is the block normally?
AV node
in second degree mobitz type II where is the block normally?
below the AV node…like the bundle of his
what is the QRS duration in second degree AV block moritz type I?
narrow/normal
what is the QRS duration in second degree AV block moritz type II?
lengthened..similar to a BBB
which type of second degree AV block does exercise and atropine improve?
type 1 or wenkenback
exercise worsens type II 2nd degree AV block
what type of block should you think of when you see grouped beating?
2nd degree AV block
what should we ask about QRS when you have tachycardia?
is the QRS narrow or wide
if we have a narrow QRS with a regular rhythm…what do we expect as tachycardia cause? (3)
sinus tachycardia
atrial flutter
PSVT
what does PSVT stand for and what 3 things does it include?
paroxysmal supraventricular tachycardia
includes AT, AVRT and AVNRT
if we have a narrow QRS with irregular tachycardic rhythm then what should we think of as the cause? (3)
atrial fibrillation
atrial flutter with bundle block
atrial premature beats
if you have a widened QRS and a regular rhythm then what do we think? (2)
sinus tachycardia with aberrancy or block
ventricular tachycardia
if you have a widened QRS and irregular rhythm what are we thinking? (4)
a fib with aberrancy or block
ventricular premature beats
V fib
Torsades
what causes atrial flutter?
functional unidirectional block with reentry normally in the right atrium
with atrial flutter…what do the P waves look like on a ECG?
sawtooth projections with continuous excitation
what is the atria rate with atrial flutter?
300 bpm
what is unique about the ventricular rate with atrial flutter?
the ventricule rate is usually a multiple of 300 which is the rate of the atria
what can atrial flutter lead to?
heart failure and stroke
PSVT mechanism
abnormal automaticity of another tissue outside of the usual nodes that is faster than the SA node
what does PSVT look like on ECG?
tachycardia with abnormal P waves
what leads to look at for P wave morphology and direction of them normally?
I- up
II- up
aVF- up
mechanism of atrial fibrillation
have abnormal automaticity of the pulmonary veins that is maintained by reentrant circuits in the left atrium
what to see on a fib ECG?
irregular QRS complex and tons of irregular “P waves”
what does a premature atrial beat look like on the ECG?
different looking P wave compared to others around it and a normal QRS usually follows
what does a ventricular premature beat look like on ECG?
irregular QRS with delayed beat following
common mechanism for ventricular tachycardia
often due to scarring from MI that has created a pathway for unidirectional block and reentry
ECG description for ventricular tachycardia
will not have normal P waves and have widened QRS complexes with tachycardic rate
how to differentiate sinus tachycardia with a block from ventricular tachycardia?
the sinus tachycardia will have P waves and the ventricular tachycardia will not…BUT they both will have widened QRS and a tachycardic rate
what usually leads to torsades?
often channelopathies that cause prolonged QT segments
