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==Overview==
==Overview==
Wolff-Parkinson-White (WPW) pattern is characterized by the presence of characteristic [[ECG]] findings, such as a short [[PR interval]] and a [[delta wave]]. Two types of WPW patterns exist: type A which is characterized by a positive delta wave, and type B which is characterized by a negative [[delta wave]] and a prominent S wave.  WPW syndrome is the occurrence of [[tachycardia]] with or without associated symptoms in a subject with existing [[WPW]] pattern.<ref>{{Cite web  | last =  | first =  | title = Wolff-Parkinson-White Syndrome and Accessory Pathways | url = http://circ.ahajournals.org/content/122/15/e480.full | publisher =  | date =  | accessdate = 1 April 2014 }}</ref>  Several types of arrhythmia can occur in WPW syndrome such as [[AV reentrant tachycardia]] (AVRT), [[atrial fibrillation]],or [[atrial flutter]], the most common of which is [[AVRT]].<ref name="circ.ahajournals.org">{{Cite web  | last =  | first =  | title = ACC/AHA/ESC Guidelines for the Management of Patients With Supraventricular Arrhythmias—Executive Summary | url = http://circ.ahajournals.org/content/108/15/1871 | publisher =  | date =  | accessdate = 15 August 2013 }}</ref> WPW syndrome can present as an orthodromic or antidromic [[AVRT]] during which the [[delta wave]] no longer appears.  [[Atrial fibrillation]] in a patient with [[WPW]] should be suspected when there is [[ECG]] findings of an irregularly irregular rhythm and absent [[P wave]]s suggestive of [[atrial fibrillation]] in the context of a [[heart rate]] higher than 220 beats per minute.
Wolff-Parkinson-White (WPW) pattern is characterized by the presence of characteristic [[ECG]] findings, such as a short [[PR interval]] and a [[delta wave]].   WPW syndrome is the occurrence of [[tachycardia]] with or without associated symptoms in a subject with existing [[WPW]] pattern.<ref>{{Cite web  | last =  | first =  | title = Wolff-Parkinson-White Syndrome and Accessory Pathways | url = http://circ.ahajournals.org/content/122/15/e480.full | publisher =  | date =  | accessdate = 1 April 2014 }}</ref>  Several types of arrhythmia can occur in WPW syndrome such as [[AV reentrant tachycardia]] (AVRT), [[atrial fibrillation]],or [[atrial flutter]], the most common of which is [[AVRT]].<ref name="circ.ahajournals.org">{{Cite web  | last =  | first =  | title = ACC/AHA/ESC Guidelines for the Management of Patients With Supraventricular Arrhythmias—Executive Summary | url = http://circ.ahajournals.org/content/108/15/1871 | publisher =  | date =  | accessdate = 15 August 2013 }}</ref> WPW syndrome can present as an orthodromic or antidromic [[AVRT]] during which the [[delta wave]] no longer appears.  [[Atrial fibrillation]] in a patient with [[WPW]] should be suspected when there is [[ECG]] findings of an irregularly irregular rhythm and absent [[P wave]]s suggestive of [[atrial fibrillation]] in the context of a [[heart rate]] higher than 220 beats per minute.


==WPW Pattern==
==WPW Pattern==
# Two pathways between the [[atrium]] and the [[ventricle]] are present.
*WPW pattern is characterized by the following typical[[ECG]] findings:
# There is a shortened [[PR interval]]
** Short [[PR interval]]: The [[PR interval]] is short because the [[ventricles]] begins to contract earlier than usual because the electrical signal travels through the accessory pathway faster than the [[AV node]].
#* PR less than 0.12 seconds
** [[Wide QRS]]
#* In most cases it varies between 0.08 and 0.11 seconds
** Presence of a [[delta wave]]
# A [[wide QRS]] with a [[delta wave]].
* Other findings that can be present in a subject with an accessory pathway include [[QRS alternans]] and [[ST segment depression]].
#* The [[QRS]] is 0.11 second or longer
#* Is inversely proportional to the [[PR interval|PR]] (i.e. the shorter the [[PR interval|PR]], the longer the [[QRS]] secondary to greater pre-excitation).
#* The combination of the shortened [[PR interval]] and widened [[QRS]] is of normal duration
# The delta wave occurs as the ventricle is activated first via the accessory pathway (AP) and then normal activation follows down the normal pathway.
#* The duration of the delta wave is 0.03 to 0.06 seconds
# The pattern of ventricular activation is determined by several factors:
#* The location of the accessory pathway: The closer the accessory pathway to the [[SA node]], the quicker the impulse will reach the atrial insertion site of the AP. In contrast, in those patients in whom the AP is located in the far lateral region of the [[left ventricle]], contribution to the AP during NSR may be minimal.  
#* The intra-atrial conduction time: Left atrial pathology will prolong the time necessary to reach the left sided AP, drugs can also prolong the time to reach a left-sided pathway.
#* The conduction time over the accessory pathway: The conduction time over the AP depends on the length of the AP and velocity with which the impulse is conducted. Investigators have found that the accessory pathway may vary in length from 1 to 10 mm. 
#* The AV conduction time over the normal AV nodal-His-Purkinje pathway
# Secondary [[T wave]] changes:
#* Because of the early asynchronous activation of the [[ventricle]], the sequence of repolarization will be different leading to [[T wave]] changes.
#* The [[T wave]] polarity is opposite in direction to the delta wave
# Concealed bypass tracts:
#* If the accessory pathway's contribution to ventricular activation is minimal because of the coincidental arrival of the excitation wavefront over the normal pathway, then this should not be called a concealed accessory pathway.
#* Concealed accessory pathways are those that conduct in a retrograde fashion (ventriculoatrial) only.
#* Antegrade conduction in these patients is absent because the refractory period of the AP in the antegrade direction is longer than the sinus cycle length.
#* When a recurrent [[tachycardia]] occurs in association with such concealed bypass, the conduction is called concealed [[WPW syndrome]]
#* Are usually located on the left side of the cardiac chambers
#* Consider this if during the tachycardia there is a negative [[P wave]] in lead V1, if there is a [[P wave]] after the QRS complex
# Findings are intermittent in 1/2 the cases


== Determining the location of the accessory pathway==
== Determining the location of the accessory pathway==

Revision as of 01:14, 18 April 2014

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

Wolff-Parkinson-White (WPW) pattern is characterized by the presence of characteristic ECG findings, such as a short PR interval and a delta wave. WPW syndrome is the occurrence of tachycardia with or without associated symptoms in a subject with existing WPW pattern.[1] Several types of arrhythmia can occur in WPW syndrome such as AV reentrant tachycardia (AVRT), atrial fibrillation,or atrial flutter, the most common of which is AVRT.[2] WPW syndrome can present as an orthodromic or antidromic AVRT during which the delta wave no longer appears. Atrial fibrillation in a patient with WPW should be suspected when there is ECG findings of an irregularly irregular rhythm and absent P waves suggestive of atrial fibrillation in the context of a heart rate higher than 220 beats per minute.

WPW Pattern

Determining the location of the accessory pathway

Check lead V1
Negative delta wave in V1 = right ventricle Positive delta wave im V1= left ventricle
Negative delta wave and QRS in II, III, AVF Left axis Inferior axis Negative delta wave and QRS in II, III, AVF Isoelectric or negative delta I, AVL, V5, V6
Posteroseptal Right free wall Anteroseptal Posteroseptal Lateral

WPW Syndrome

WPW syndrome is the occurrence of tachycardia with or without associated symptoms in a subject with existing WPW pattern.[3] Several types of arrhythmia can occur in WPW syndrome such as AV reentrant tachycardia (AVRT), atrial fibrillation,or atrial flutter, the most common of which is AVRT.[2]

Orthodromic AVRT

The anterograde conduction (from the atrium to the ventricle) passes through the AV node and the retrograde conduction (from the ventricle to the atrium) passes through the accessory pathway. It apprears in 90 to 95% of WPW.
The EKG findings include:

  • Regular rhythm
  • Narrow QRS complexes
  • P wave before QRS

Antidromic AVRT

The anterograde conduction (from the atrium to the ventricle) passes through the accessory pathway and the retrograde conduction (from the ventricle to the atrium) passes through the AV node. It apprears in less than 10% of WPW.
The EKG findings include:

Clinical Manifestations

  1. The most common form of paroxysmal tachycardia in these patients is a circus movement tachycardia (CMT) incorporating the AP.
  2. The CMT utilizes the following structures: the AV node, the His-Purkinje system, the ventricular myocardium (from the terminal portion of the His system to the ventricular end of the AP), the AP itself, and the atrial myocardium itself from the atrial insertion of the AP to the AV node.
  3. This circuit can conduct in both directions:
    • Type I A CMT:
      1. This is the usual form of the CMT in patients with WPW.
      2. Is antegrade through the AV node, VA conduction through the AP.
      3. The QRS complex during the tachycardia shows either normal intraventricular conduction or typical bundle branch block configuration.
      4. Symptoms: Palpitations (97%), dyspnea (57%), anginal pain (56%), perspiration (55%), fatigue (41%), anxiety (30%), dizziness (30%),polyuria (26%).
      5. This is also called orthodromic reentrant tachycardia.
      6. There is no delta wave.
      7. The rate is 140 to 250 bpm.
      8. It is faster than the rate of tachycardia due to reentry in the AV node.
      9. Often triggered by a PAC


    • Type I B CMT:
      1. Anterograde down the accessory pathway, retrograde in the AVN-His pathway.
      2. The QRS is widened (wide QRS)
      3. This form is rare.
      4. Also called antidromic reentrant tachycardia.


    • Type II CMT (intra-AV nodal):
      1. Anterograde pathway is an AV nodal slow pathway, the retrograde pathway is an AV nodal fast pathway.
      2. No evidence of ventricular pre-excitation during the tachycardia.
    • Type III CMT (uses two accessory pathways):
      1. Conducts anterograde down one accessory pathway and retrograde up a second accessory pathway.
      2. These patients can also experience atrial tachycardias and ventricular tachycardias.

Atrial Fibrillation in WPW

Can cause life-threatening ventricular rates due to the exclusive AV conduction over the accessory pathway.

    • Reduces cardiac output.
    • May degenerate into VF, particularly in those with multiple bypass tracts.
  2. The only marker identified for degeneration into VF in the literature was the occurrence of RR intervals equal to or less than 205 msec during the a fib
  3. Seen in 78 of 256 of Wellen's patients with WPW. Reported incidence is 20 to 35% in other studies.
  4. The degree of ventricular preexcitation observed in the EKG during NSR bears no relationship whatsoever to the risk of developing life-threatening ventricular rates during the a.fib.
  5. The QRS complexes are wide and bizarre as a result of preexcitation.
  6. The ventricular rate is 220 to 360 beats per minute due to the short effective refractory period of the accessory pathway.
  7. It is often mistaken for VT.
  8. If the atrial rate in atrial fibrillation is greater than 200 BPM then suspect this. The rhythm will also be grossly irregular if it is due to atrial fibrillation. Such a rapid rate would be unusual if it were due to conduction by way of the normal AV conduction system.

Examples

Shown below is an EKG of Wolff-Parkinson-White syndrome demonstrating slurred upstroke of the QRS complex (>110 milli sec), resulting in a delta-wave (arrow). The EKG also shows a short PR interval.

Copyleft image obtained courtesy of ECGpedia,http://en.ecgpedia.org/wiki/Main_Page

Shown below is an EKG showing a slurred upstroke QRS complex which is best appreciated in the precordial leads and a PR interval of less than 120 ms (short PR interval) suggesting WPW syndrome.

Copyleft image obtained courtesy of ECGpedia,http://en.ecgpedia.org/wiki/Main_Page

Shown below is an EKG demonstrating a delta wave in leads V2, I, aVL, with wide QRS complexes and left axis deviation suggesting WPW syndrome.

Copyleft image obtained courtesy of ECGpedia,http://en.ecgpedia.org/wiki/Main_Page

Shown below is an EKG showing a short PR interval of less than 120 ms, delta waves in leads I, aVF, aVL and chest leads with wide QRS complexes indicating WPW syndrome.

Copyleft image obtained courtesy of ECGpedia,http://en.ecgpedia.org/wiki/Main_Page

For more EKG examples of Wolff-Parkinson-White syndrome click here.

References

  1. ↑ "Wolff-Parkinson-White Syndrome and Accessory Pathways". Retrieved 1 April 2014.
  2. ↑ 2.0 2.1 "ACC/AHA/ESC Guidelines for the Management of Patients With Supraventricular Arrhythmias—Executive Summary". Retrieved 15 August 2013.
  3. ↑ "Wolff-Parkinson-White Syndrome and Accessory Pathways". Retrieved 1 April 2014.

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