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what are the three basic categories of conduction blocks?
sinus node block, AV, bundle branch
if the sinus node is blocked, does it fire normally?
yes
what part of the heart does an AV block refer to?
between the sinus node and the distal end of the bundle of His...which of course includes the AV node
what part of the heart does a bundle branch block effect?
from where the left and right bundle branches meet at the bundle of His, all the way down to the end of the Purkinje fibers
how many degrees of AV blocks are there?
3
how many types of second degree AV block are there, and what are their names?
two types, Mobitz type 1 and Mobitz type 2.

mobitz type 1 second degree AV block also has what name?
Wenckebach Block
Is EKG able to distinguish between a block in the AV node and one in the His bundle?
no
what is occurring electrically with first degree AV block?
there is a delay at the AV node, all signals from the SA node get to and through the AV node, but with a delay.
what does 1st degree AV block look like on EKG?
a prolonged PR interval
how long must the PR interval be for first degree AV block to be diagnosed? and how many tiny boxes is that on the paper?
longer than 0.2 seconds, 5 tiny boxes
what is a normal PR interval, in terms of time and how many tiny boxes?
0.12-0.20, 3-5 tiny boxes
with first degree AV block, is there a QRS complex after every P wave?
yes
when is first degree AV block usually treated?
only when there is other evidence of heart dysfunction, but by itself it is not treated
what happens electrically with second degree AV blocks?
not every atrial impulse is able to pass through the AV node
which of the two types of second-degree block involve a block within the AV node?
mobitz type 1, Wenckebach
which type of second degree AV block has a block below the AV node in the His bundle?
mobitz type 2
which of the two types of second degree AV block are caused by a block below the AV node?
Mobitz type 2
mobitz type 1 AV block looks like what\'s on EKG?
each PR interval is increased until an entire P wave and QRS complex is omitted
mobitz type 1 AV block is typically described with also a what? And how is this computed?
a ratio of P waves to QRS complexes, this is computed even including a p-wave which is part of the QRS complex
diagnosis of Wenckebach block requires the progressive lengthening of each what interval until what fails to conduct at all?
progressive lengthening of each successive PR interval until 1p weigh fails to conduct at all, there will be AP wave but no QRS complex
mobitz type 2 block looks like what on EKG?
since conduction is an all-or-nothing phenomenon, ekg does not show a lengthening PR interval.
the EKG will show two or more normal beats with normal PR intervals, then it P wave that is not followed by a QRS complex
is the ratio of P waves to QRS complexes with mobitz type two block consistent?
no
the official diagnosis of mobitz type two block requires the presence of what two ekg features?
a dropped beat without progressive lengthening of the PR interval
the major distinction between a type 1 and type 2 second degree AV block is what ekg feature?
whether or not the PR interval remains the same or is progressively lengthened
what is happening conductively with third degree AV block?
there are no atrial impulses that make it through to activate the ventricles, but the ventricles create an escape on their own and continue to beat, at a very low rate
any circumstances in which the atria and ventricles are being driven by independent pacemakers it is called AV what?
AV dissociation
3rd degree AV block is also called what?
Complete heart block
With third degree AV block, what are typical atrial and ventricle rates?
atrial 60-100, ventricles 30-45
what does third degree AV block look like on EKG?
the P waves appear at regular intervals, the QRS complexes also appear at regular intervals, but they are not associated with each other, and the QRS complexes are wide
wide QRS complexes, such as in third degree AV block, usually implies what?
that the QRS complex signal originated in a ventricle
why would a ventricular QRS complex be wider than an atrial-origin QRS complex?
because the ventricles conduct much slower
what is the obvious ekg difference between a ventricular escape rhythm, as with third degree AV block, and PVCs?
the speed at which they occur, PVCs are fast and premature, coming before the next expected beat.
ventricular escape beats occur after a long pause and is never premature, it is always slower than normal beats.
ventricular escape beat
diagnosis of third degree AV heart block requires the presence of what and what rate requirements?
requires the presence of AV dissociation in which the ventricular rate is lower than the sinus or atrial rate
how is third degree AV heart block treated?
it is a medical emergency, requiring a pacemaker
what are the two greatest risk factors of a third degree AV dissociation?
an acute infarction in progress, an overdose of antiarrhythmic medication
what disease can cause a reversible complete heart block if treated fast enough?
Lyme disease
with normal ventricular depolarization, the QRS complex is what, and the electrical axis lies between what and what degrees?
narrow, 0 and 90 degrees
bundle branch blocks are diagnosed by looking at what 2 EKG features?
QRS complex width and configuration
which is more common, right or left bundle branch block?
right bundle branch block is more common than left
what happens electrically with right bundle branch block?
right ventricular depolarization is delayed and does not begin until the left ventricle is almost fully depolarized
what are the two key features on EKG of right bundle branch block?
QRS complex is widened beyond 0.12 seconds, and the creation of a rabbit ears shaped QRS complex
what is a rabbit ears QRS complex, and which leads will show this?
it is the shape of two nearly separate R waves, the first and stronger one is the left ventricle and the second weaker one is the right ventricle depolarizing.
The rabbit ears are seen most prominently in v1 but also somewhat in v2
With right bundle branch block, the rabbit ears QRS complex, what is the second r-wave technically called?
R\' or R prime
with right bundle branch block, the QRS complex with rabbit ears, altogether is technically called what in notation format?
RSR prime
right bundle branch block
left bundle branch block
With right bundle branch block, the QRS complex assumes what shape in which 2 leads?
Rabbit ears in v1 and v2
With left bundle branch block, what is occurring electrically?
because left bundle branch block, there is a delay in the left ventricle becoming depolarized, and when they do, they do so very suddenly and show a very tall R wave
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