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53 Cards in this Set

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condition characterized by electrical current being conducted to the ventricles more quickly than usual
preexitation
With normal conduction, where is the major delay between the atria and ventricles?
in the AV node
In normal conduction, how long is the wave of depolarization typically held up in the AV node?
0.1 seconds
(long enough for the atria to contract and empty their contents into the ventricles)
areas of the heart through which current can bypass the AV node and arrive at the ventricles ahead of time
accessory pathways
True of False:
A number of accessory pathways have been discovered, with a decidedly male preponderance.
True.
However, fewer than 1% of individuals possess these pathways.
True or False:
Accessory pathways virtually always point to underlying heart disease.
False.
Accessory pathways may occur in normal healthy hearts as an isolated finding.
Name three medical conditions that may be associated with the presence of accessory pathways.
mitral valve prolapse
hypertrophic obstructive cardiomyopathy (HOCM)
various congenital disorders
Name the two major preexitation syndromes.
Wolff-Parkinson-White (WPW)
and
Lown-Ganong-Levine (LGL)
syndromes
True or False:
WPW and LGL syndromes are difficult to diagnose on EKG.
False.
Both are easily diagnosed on EKG.
In WPW and LGL, the accessory conduction pathways bypass the AV node and act as _______ to the ventricles.
"short circuits"
In WPW and LGL, the ventricles are activated ______.
prematurely
name of the bypass pathway in WPW syndrome
bundle of Kent
discreet aberrant conduction pathway that connects the artial and ventricles in WPW syndrome
bundle of Kent
True or False:
The bundle of Kent is always located between the right atrium and ventricle, posterior to the SA node.
False.
The bundle of Kent can be left sided or right sided.
criteria for WPW syndrome
(1) PR interval less than 0.12 seconds

(2) Wide QRS complexes

(3) Delta waves seen in some leads
The criterion for diagnosis of WPW is a PR interval of this duration.
less than 0.12 seconds
True or False:
The PR interval in WPW is prolonged.
False.
It is shortened.
In WPW, the QRS complex is widened to what duration?
more than 0.1 seconds
Unlike the delayed ventricular activation seen in bundle branch blocks, in WPW the QRS is widened due to ______ activation.
premature
True or False:
The QRS complex in WPW actually represents a fusion beat.
True.
Most of the ventricular myocardium is activated through normal conduction pathways, but a small region is depolarized early through the bundle of Kent.
slurred initial upstroke of the QRS that reflects the premature depolarization of a small region of the myocardium through an accessory pathway
delta wave
True or False:
A true delta wave is seen in all leads.
False.
A true delta wave may be seen in only a few leads, so scan the entire EKG.
What condition would you suspect upon seeing a short PR interval and a delta wave on EKG?
WPW syndrome
accessory pathway in Lown-Ganong-Levine syndrome
James fibers
James fibers are characterized as ______, or within the AV node.
intranodal
True or False:
Ventricular conduction in LGL is aberrant.
False.
All ventricular conduction occurs in the usual ventricular conduction pathways.
True or False:
Like WPW, LGL produces a delta wave.
False.
Since there is no aberrant conduction in LDL, no delta wave is seen.
What is the difference in ventricular conduction between WPW and LGL?
WPW -- partly aberrant conduction pathway

LGL -- normal conduction pathway
Name the one and only electrical manifestation of LGL.
shortening of the PR interval
Explain why the PR interval in LGL is short.
James fibers within the AV node bypass the normal delay
In LGL, the PR interval is what duration?
less than 0.12 seconds
criteria for LGL syndrome
(1) PR interval less than 0.12 seconds

(2) Normal QRS width

(3) No delta wave
If you were to see a very short PR interval in EKG with no other apparent abnormalities, what condition might you suspect?
LGL syndrome
True or False:
Virtually all individuals with WPW and LGL are eventually symtomatic.
False.
In many individuals with WPW or LGL, preexcitation poses few, if any, clinical problems.
True or False:
Preexcitation predisposes the heart to various tachyarrhythmias.
True.
True or False:
50% to 70% of individuals with WPW experience at least one supraventricular arrhythmia.
True.
Name the two tachyarrhythimias most often seen in WPW.
PSVT and A-fib
True or False:
An accessory bundle tends to naturally inhibit reentrant tachycardias.
False.
An accessory bundle is the perfect substrate for reentry.
True or False:
The bundle of Kent usually conducts current faster than the AV node.
True.
True or False:
The bundle of Kent has a shorter refractory period than the AV node.
False.
It tends to have a longer refractory period than the AV node.
True or False:
If a PAC initially finds the bundle of Kent refractory, current may pass normally through the AV node then immediately return to the atria through the no longer refractory bundle of Kent, forming a reentry loop.
True.
This scenario may form a self sustaining reentry loop between the ventricles and atria.
What type of beat is likely to find the bundle of Kent refractory.
artial premature beat
PSVT formed by reentry from the ventricles to the atria through the bundle of Kent would likely produce what QRS morphology?
Normal.
The ventricles would receive current normally from the AV node and bundle branches in this type of scenario.
Which is more common in WPW related PSVT:

(1) Normal ventricular depolarization via the bundle branches with atrial reentry through the bundle of Kent

(2) abberant ventricular depolarization via the bundle of Kent with retrograde atrial reentry though the AV node
Scenario 1 is more common.
What type of QRS would you expect in a WPW related PSVT in which the reentrant mechanism circles down the bundle of Kent and back up through the AV node?
wide and bizarre QRS
True or False:
There may be more than one Kent bundle in individuals with WPW.
True.
10-15% of patients with WPW have more than one accessory pathway.
What percentage of individuals with WPW have more than one accessory pathway?
10-15%
What percentage of individuals with WPW experience at least one tachyarrhythmia as a result?
50-70%
True or False:
Atrial Fibrillation secondary to WPW can be particulary devastating.
True.
Without the AV node to act as a barrier to the atrial chaos, ventricular rates can rise as high as 300 beats per minute.
True or False:
Atrial fib in WPW can be fatal, as it has been known to bombard the ventricles through the bundle of Kent and thus induce ventricular fibrillation.
True.
But this lethal form of atrial fib is rare in WPW.
What should be considered a diagnostic possibility in any post cardiac arrest patient that is found to have preexcitation on their cardiograms?
a-fib in WPW
What is an effective method of pinpointing and eliminating the bundle of Kent.
EPS/ablation
True or False:
WPW does not interfere with EKG diagnosis of bundle branch block or ventricular hypertrophy.
False.
Because the presence of an accessory pathway in WPW alters the vector and current flow to at least some degree, you cannot access axis or amplitude with any precision.