Wolff parkinson white syndrome

Dr David Carroll et al.

The Wolff-Parkinson-White syndrome describes paroxysmal tachydysrhythmias in the presence of a specific accessory pathway (AP) which allows direct electrical connection between the atria and ventricles, which usually exclusively occurs via the atrioventricular node. The accessory pathway is usually referred to as the bundle of Kent, situated in the atrioventricular groove, and is thought to arise as a result of incomplete atrioventricular separation during prenatal life.

If the impulse from the sinoatrial node conducts ("antegrade") through the bypass tract to the ventricles prior to (simultaneously occuring normal conduction) egress from the bundle of His (via the AV node), three features will be evident on the electrocardiogram:

  • shortening of the PR interval
    • the accessory pathway allows faster conduction than the AV node
    • normal PR interval between 0.12-0.20 seconds
  • a "delta" wave
    • slurring of the initial portion of the QRS complex
    • myocyte-to-myocyte conduction, after AP conduction, is less organized than conduction through the specialized conduction system
  • slight widening of the QRS
    • the initial disorganized conduction results in the total duration (normal duration <0.08 seconds) of the QRS being slightly (0.10-0.12 seconds) longer

These features define the "pre-excited" ECG, and must be present when a patient is in normal sinus rhythm to diagnose the wolff-parkinson-white (WPW) syndrome.

An estimated 1/2000 people have an accessory pathway, most of whom will have otherwise structurally normal hearts. Syndromic associations include:

The most common symptom reported is palpitations, which may be spontaneous or triggered by activity, last from seconds to days, and terminate abruptly. Most patients are hemodynamically stable on presentation. Other common symptoms include:

  • pre-syncope
  • dyspnea
  • weakness

Of note, patients who present in atrial fibrillation may be profoundly unstable, and may present with:

 

Features depend on whether the patient is in normal sinus rhythm, or presenting with a tachydysrhythmia; three types of tachydysrhhmia occur, all of which abolish the classic "pre-excitation" features found in sinus rhythm 6

  • normal sinus rhythm
    • short PR interval, delta wave, slight QRS widening, secondary ST-T changes
    • subdivided into two types based on the QRS complex in precordial lead V1
      • type A WPW
        • dominant R wave in V1 (R wave > S wave)
      • type B WPW
        • lead V1 has a predominantly negative QRS complex (S or Q wave > R wave)

Features present during a paroxysm of a tachydysrhythmia depend on the pathway taken and the atrial activity present; the three classic presenting rhythms have the following ECG features

  • narrow complex, regular tachycardia
    • orthodromic atrioventricular reciprocating tachycardia (AVRT)
      • most common presenting rhythm
      • an atrial ectopic beat (PAC) initiates a re-entry circuit through the AV node, retrograde through the AP to the atria, completing the circuit through the AV node once more
  • wide complex tachycardia
    • atrial fibrillation with WPW
      • may result in hemodynamic instability 
      • ventricular rate may reach up to 300 beats per minute
      • marked variation in R-R intervals, QRS width, and QRS morphology
    • antidromic AVRT
      • conduction antegrade through the AP to the ventricles, retrograde through the AV node to the atria, then once more through the AP
      • regularity of the ventricular rate distinguishes this rhythm from atrial fibrillation with WPW

In 10% of cases multiple accessory pathways co-exist. There are three classically described types of pathways, classified based on the anatomical structures which they connect and the resultant features on the electrocardiogram. ECG features in sinus rhythm of the respective pathways include 4:

  • bundle of james
    • connect the proximal atrioventricular node (AVN) to the distal AVN
    • short PR interval, no delta wave
  • bundle of kent
    • connect the atria to the ventricles
    • short PR interval and a delta wave
  • mahaim fibers
    • connect the right atrium to right bundle branch fascicles
    • normal (0.12-0.20 seconds) PR interval, delta wave 

Accessory pathways may be right-sided, prematurely activating the right ventricle, left-sided or left-sided, pre-exciting the left ventricle. They may also be present on the inferior surface of the heart, located near the interventricular septum.

Fetal M mode echocardiography may be used to diagnose the presence of a fetal supraventricular tachycardia, a rare cause of which may be an AVRT due to an accessory pathway. The fetal HR in an SVT is usually above 200 beats per minute, with a normal FHR falling between 120-160 bpm.

Antegrade conduction down the AP results in a long R-P interval (time between the peak of the "R" of the QRS and the start of the P wave) on the electrocardiogram; the M-mode correlate of this finding is a short V-A interval 4.

The presence of re-entry through an accessory pathway (with fast retrograde conduction and slow antegrade conduction) is considered a likely etiology when the VA interval is shorter than the AV interval in the presence of a fetal SVT; this may affect choice of therapy and prognosis.

The tripartite eponym is derived from the three cardiologists who published the first study case study on eleven patients with this syndrome; Louis Wolff (1898 – 1972), Paul White (1886 – 1973), and John Parkinson (1885 – 1976) 1

Congenital heart disease

There is more than one way to present the variety of congenital heart diseases. Whichever way they are categorized, it is helpful to have a working understanding of normal and fetal circulation, as well as an understanding of the segmental approach to imaging in congenital heart disease.

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Article information

rID: 66980
System: Cardiac
Synonyms or Alternate Spellings:

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