Ekg - Preexcitation Syndromes

Front 1

condition characterized by electrical current being conducted to the ventricles more quickly than usual

Back 1

preexitation

Front 2

With normal conduction, where is the major delay between the atria and ventricles?

Back 2

in the AV node

Front 3

In normal conduction, how long is the wave of depolarization typically held up in the AV node?

Back 3

0.1 seconds
(long enough for the atria to contract and empty their contents into the ventricles)

Front 4

areas of the heart through which current can bypass the AV node and arrive at the ventricles ahead of time

Back 4

accessory pathways

Front 5

True of False:
A number of accessory pathways have been discovered, with a decidedly male preponderance.

Back 5

True.
However, fewer than 1% of individuals possess these pathways.

Front 6

True or False:
Accessory pathways virtually always point to underlying heart disease.

Back 6

False.
Accessory pathways may occur in normal healthy hearts as an isolated finding.

Front 7

Name three medical conditions that may be associated with the presence of accessory pathways.

Back 7

mitral valve prolapse
hypertrophic obstructive cardiomyopathy (HOCM)
various congenital disorders

Front 8

Name the two major preexitation syndromes.

Back 8

Wolff-Parkinson-White (WPW)
and
Lown-Ganong-Levine (LGL)
syndromes

Front 9

True or False:
WPW and LGL syndromes are difficult to diagnose on EKG.

Back 9

False.
Both are easily diagnosed on EKG.

Front 10

In WPW and LGL, the accessory conduction pathways bypass the AV node and act as _______ to the ventricles.

Back 10

"short circuits"

Front 11

In WPW and LGL, the ventricles are activated ______.

Back 11

prematurely

Front 12

name of the bypass pathway in WPW syndrome

Back 12

bundle of Kent

Front 13

discreet aberrant conduction pathway that connects the artial and ventricles in WPW syndrome

Back 13

bundle of Kent

Front 14

True or False:
The bundle of Kent is always located between the right atrium and ventricle, posterior to the SA node.

Back 14

False.
The bundle of Kent can be left sided or right sided.

Front 15

criteria for WPW syndrome

Back 15

(1) PR interval less than 0.12 seconds

(2) Wide QRS complexes

(3) Delta waves seen in some leads

Front 16

The criterion for diagnosis of WPW is a PR interval of this duration.

Back 16

less than 0.12 seconds

Front 17

True or False:
The PR interval in WPW is prolonged.

Back 17

False.
It is shortened.

Front 18

In WPW, the QRS complex is widened to what duration?

Back 18

more than 0.1 seconds

Front 19

Unlike the delayed ventricular activation seen in bundle branch blocks, in WPW the QRS is widened due to ______ activation.

Back 19

premature

Front 20

True or False:
The QRS complex in WPW actually represents a fusion beat.

Back 20

True.
Most of the ventricular myocardium is activated through normal conduction pathways, but a small region is depolarized early through the bundle of Kent.

Front 21

slurred initial upstroke of the QRS that reflects the premature depolarization of a small region of the myocardium through an accessory pathway

Back 21

delta wave

Front 22

True or False:
A true delta wave is seen in all leads.

Back 22

False.
A true delta wave may be seen in only a few leads, so scan the entire EKG.

Front 23

What condition would you suspect upon seeing a short PR interval and a delta wave on EKG?

Back 23

WPW syndrome

Front 24

accessory pathway in Lown-Ganong-Levine syndrome

Back 24

James fibers

Front 25

James fibers are characterized as ______, or within the AV node.

Back 25

intranodal

Front 26

True or False:
Ventricular conduction in LGL is aberrant.

Back 26

False.
All ventricular conduction occurs in the usual ventricular conduction pathways.

Front 27

True or False:
Like WPW, LGL produces a delta wave.

Back 27

False.
Since there is no aberrant conduction in LDL, no delta wave is seen.

Front 28

What is the difference in ventricular conduction between WPW and LGL?

Back 28

WPW -- partly aberrant conduction pathway

LGL -- normal conduction pathway

Front 29

Name the one and only electrical manifestation of LGL.

Back 29

shortening of the PR interval

Front 30

Explain why the PR interval in LGL is short.

Back 30

James fibers within the AV node bypass the normal delay

Front 31

In LGL, the PR interval is what duration?

Back 31

less than 0.12 seconds

Front 32

criteria for LGL syndrome

Back 32

(1) PR interval less than 0.12 seconds

(2) Normal QRS width

(3) No delta wave

Front 33

If you were to see a very short PR interval in EKG with no other apparent abnormalities, what condition might you suspect?

Back 33

LGL syndrome

Front 34

True or False:
Virtually all individuals with WPW and LGL are eventually symtomatic.

Back 34

False.
In many individuals with WPW or LGL, preexcitation poses few, if any, clinical problems.

Front 35

True or False:
Preexcitation predisposes the heart to various tachyarrhythmias.

Back 35

True.

Front 36

True or False:
50% to 70% of individuals with WPW experience at least one supraventricular arrhythmia.

Back 36

True.

Front 37

Name the two tachyarrhythimias most often seen in WPW.

Back 37

PSVT and A-fib

Front 38

True or False:
An accessory bundle tends to naturally inhibit reentrant tachycardias.

Back 38

False.
An accessory bundle is the perfect substrate for reentry.

Front 39

True or False:
The bundle of Kent usually conducts current faster than the AV node.

Back 39

True.

Front 40

True or False:
The bundle of Kent has a shorter refractory period than the AV node.

Back 40

False.
It tends to have a longer refractory period than the AV node.

Front 41

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.

Back 41

True.
This scenario may form a self sustaining reentry loop between the ventricles and atria.

Front 42

What type of beat is likely to find the bundle of Kent refractory.

Back 42

artial premature beat

Front 43

PSVT formed by reentry from the ventricles to the atria through the bundle of Kent would likely produce what QRS morphology?

Back 43

Normal.
The ventricles would receive current normally from the AV node and bundle branches in this type of scenario.

Front 44

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

Back 44

Scenario 1 is more common.

Front 45

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?

Back 45

wide and bizarre QRS

Front 46

True or False:
There may be more than one Kent bundle in individuals with WPW.

Back 46

True.
10-15% of patients with WPW have more than one accessory pathway.

Front 47

What percentage of individuals with WPW have more than one accessory pathway?

Back 47

10-15%

Front 48

What percentage of individuals with WPW experience at least one tachyarrhythmia as a result?

Back 48

50-70%

Front 49

True or False:
Atrial Fibrillation secondary to WPW can be particulary devastating.

Back 49

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.

Front 50

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.

Back 50

True.
But this lethal form of atrial fib is rare in WPW.

Front 51

What should be considered a diagnostic possibility in any post cardiac arrest patient that is found to have preexcitation on their cardiograms?

Back 51

a-fib in WPW

Front 52

What is an effective method of pinpointing and eliminating the bundle of Kent.

Back 52

EPS/ablation

Front 53

True or False:
WPW does not interfere with EKG diagnosis of bundle branch block or ventricular hypertrophy.

Back 53

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.