Rapid Interpretations of EKGs - Chapter 6 highlights Flashcards
Rhythm, Part II
When examining the rhythm on a tracing, why should you always check for all the varieties of block?
because the same patient can have more than one type of block going on at the same time
What are the 4 types of blocks?
What occurs in Sinus Block?
an unhealthy SA node stops its pacing activity for at least one complete cycle these blocks are usually transient
What are the three types of AV block?
What occurs in a first degree AV block?
prolonged PR interval, more than one large square (0.2 seconds) on EKG the conduction through the AV node is retarded :D
With consistant PR prolongation, first degree AV block is present. What does it mean if you see a PR interval longer than 0.2 seconds anywhere in the tracing? (in a random spot)
that some type of AV block is present
What are the two types of second degree AV blocks and where do they originate?
Wenckebach and Mobitz
Wenckebach occurs in the AV node. What will you see on the EKG that leads you to believe that rhythm is, in fact, Wenckebach?
the PR interval gradually lengthens in successive cycles, but the last P wave of the series fails to conduct to the ventricles
Mobitz block occurs in the Purkinje fiber bundles of the His Bundle or the Bundle Branches. What will you see on the EKG that leads you to believe that the rhythm is, in fact, Mobitz?
there are a series of cycles consisting of one normal P-QRS-T cycle preceeded by a series of paced P waves that fail to conduct through the AV node
When considering Wenckebach and Mobitz blocks, which one is innocuous and which one is pathological?
Wenckebach = innocuous
Mobitz = pathological
If you see a 2:1 AV block, what would clue you in on whether it’s a Wenckebach 2:1 AV block or Mobitz 2:1 AV block?
Wenckebach = lengthened PR interval, but the QRS is normal
Mobitz = the PR interval is normal, but the QRS is widened
(since Wenckebach commonly originates in the AV node, the pacing focus will be junctional and the QRS will be of normal duration [ie. the ventricles will contract together])
(since Mobitz originates below the AV node, the pacing focus will be ventricular in origin, producing a widened QRS [ie. the ventricles are not contracting together])
If you have a 2:1 AV block and you aren’t sure if it’s Wenckebach or Mobitz, based on the PR interval and QRS width, what can you have the patient do to make the proper determination?
a vagal maneuver (since the AV node is richly supplied with parasympathetic innervation, vagal maneuvers will inhibit the AV node and increase the number of cycles/series to show a Wenchebach pattern.
alternatively, because Mobitz blocks occur in the ventricular conduction system, a vagal maneuver will either eliminate the block, producing 1:1 AV conduction, or they have no effect)
What occurs in a third degree AV block?
there is a total block of conduction to the ventricles from the atria
If the complete AV block is in the AV node, above the AV Junction, then what will the QRS complex look like and what rate will the QRS be pacing at?
If the complete AV block occurs below the AV Junction, then what will the QRS complex look like and what rate will the QRS be pacing at?
What occurs in a Bundle Branch Block (BBB)?
there is a block of conduction in the Right or Left Bundle Branch
RBBB produces an R,R’ in what leads?
LBBB produces an R,R’ in what leads?
Review of the steps for checking the origin of a BBB.
What is it called if you have a block of one Bundle Branch with intermittent block of the other Bundle Branch?
intermittent complete AV block (or intermittent Mobitz)
