In the presence of high atrial rates (atrial fibrillation or flutter) the slow conduction properties of the AV node does not permit all atrial impulses to stimulate the ventricles, protecting them from rapid rates.

  In patients with WPW syndrome, the accessory pathway may permit very rapid conduction to ventricles through bypassing the AV node. This may result in development of ventricular fibrillation and death.

  This is assumed to be the basis for the very small risk of sudden death in patients with WPW syndrome.

  In patients with WPW syndrome, the risk of sudden death is highest when the shortest RR interval during atrial fibrillation is < 200 msec (5 small squares).

  The risk of sudden death is thought to be low in patients with concealed accessory pathyways (no delta waves during sinus rhythm).

  During atrial fibrillation in patients with WPW syndrome, the ventricles can be depolarized over the accessory pathyway, the AV node or by a fusion of both. This may result in different QRS morphologies.




Observation of the following ECG triad should raise the suspicion of atrial fibrillation in WPW syndrome

  Irregular rhythm

  Very high rate

  Wide QRS tachycardia




References

  Kusumoto, Fred. Understanding intracardiac EGMs and ECG’s.

      2010. Wiley-Blackwell. ISBN 978-1-4051-8410-6.             (
highly recommended)

  Murgatroyd, Francis D. Handbook of Cardiac Electrophysiology.

      2002 ReMEDICA Publishing. ISBN 1 901346 37 4.

  Indian Pacing Electrophysiol J 2008;8(2):141-145.





ECG 1a. Atrial fibrillation in WPW syndrome: very rapid, irregular, wide QRS tachycardia.

Prof. Dr. Bulent Ozin has donated the above ECG to our website.




ECG 1b. Leads aVR, aVL and aVF of the same patient.

Prof. Dr. Bulent Ozin has donated the above ECG to our website.




ECG 1c. Leads V1, V2 and V3 of the same patient.

Prof. Dr. Bulent Ozin has donated the above ECG to our website.




EKG 1d. Leads V4, V5 and V6 of the same patient.

Prof. Dr. Bulent Ozin has donated the above ECG to our website.





ECG 2a. Very rapid and irregular wide QRS tachycardia in another patient.
Very rapid ventricular rate during atrial fibrillation should raise the suspicion of WPW syndrome.
The above ECG was recorded before cardioversion.

Prof. Dr. Bulent Ozin has donated the above ECG to our website.

Click here for a more detailed ECG




ECG 2b. The same patient's ECG after cardioversion shows sinus rhythm with delta waves (pre-excitation).

Prof. Dr. Bulent Ozin has donated the above ECG to our website.

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ECG 3. The above rhythm tracing was obtained from the recorder of the defibrillator just before cardioversion.
Very rapid and irregular wide QRS tachycardia: atrial fibrillation in WPW syndrome

Prof. Dr. Bulent Ozin has donated the above ECG to our website.

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ECG 4a. Preexcited atrial fibrillation. The ECG above belongs to a 43 years-old woman who developed a rapid heart rate with
light headedness on exercise. Her ECG immediately after exercise is above. Observation of very rapid and irregular wide QRS
tachycardia suggest the diagnosis of atrial fibrillation in WPW syndrome.

Dr. Fred Kusumoto has donated the above ECG to our website.

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ECG 4b. Preablation of ECG of the same patient shows subtle delta waves in leads III and V3.

Dr. Fred Kusumoto has donated the above ECG to our website.

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ECG 4c. Postablation ECG of the same woman does not show delta waves any more.

Dr. Fred Kusumoto has donated the above ECG to our website.

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ECG 5a. The ECG above is from a 34 years-old woman with palpitation.
The rhythm is atrial fibrillation with a very high ventricular rate.
Sometimes,
the RR interval approaches to 200 milliseconds.

Dr. Fikret Agir has donated the above ECG to our website.

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ECG 5b. The ECG above belongs to the same patient. It was recorded after electrical cardioversion.
Now the rhythm is sinus. Some leads show
delta waves : WPW syndrome.

Dr. Fikret Agir has donated the above ECG to our website.

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ECG 6a. The ECG above is from a 40 years-old woman complaining of palpitation.
Atrial fibrillation with a high ventricular response is seen.

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ECG 6b. Above ECG belongs to the same woman. It was recorded after electrical cardioversion.
Sinus rhythm, left bundle branch block, short PR interval and delta wave is seen.

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