WPW syndrome may be intermittent

  In some patients, preexcitation may be seen on occasional days.

  In some others, preexcitation may appear in a few beats and then disappear and reappear again.

  In patients with complete AV block, some P waves buried in QRS complex, will deform the QRS and

      may falsely give the impression of
delta wave and therefore intermittent WPW syndrome

      at first glance.




How to differentiate intermittent preecitation from fusion beat?

  The fusion beat arises due to fortuitous meeting of a supraventricular impulse and ventricular impulse

      in the ventricle.

  This fortuitous meeting of impulses result in
QRS complexes with different shapes.

  On the other hand,
intermittent preexcitation results in similar QRS complexes with delta waves.





ECG 1. Intermittent WPW syndrome. Only
some beats show short PR interval and delta waves while others do not.

Dr. Beatrice Brembilla has donated the above ECG to our website.

Click here for a more detailed ECG





ECG 2. WPW syndrome in an 11 years old child. Preexcitation was not observed everyday. Electrophysiological study revealed
inferior accessory pathyway and the child underwent successfull radiofrequency ablation. This ECG also shows sinus
arrhythmia.

Dr. Christian Balmer has donated the above ECG to our website.

Click here for a more detailed ECG





ECG 3. Intermittent WPW syndrome in child.
.

Dr. Christopher Rausch has donated the above ECG to our website.

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ECG 4. The left side of above ECG shows complete AV block.
P waves are not related to QRS complexes.
Some P waves, buried in the QRS, deform the QRS complex and give the impression of intermittent WPW syndrome at first glance

The right side shows Wenkebach AV block.
PR interval gradually prolongs; 3rd and 6th
P waves are dropped (not conducted to the ventricles).

Click here for a more detailed ECG





ECG 5. The ECG above belongs to a 68 years-old woman.
Only some of the beats show short PR interval and
delta wave (preexcitation) (denoting intermittent WPW).
At first glance, these two beats may seem like fusion beats.
Especially, if there was only one of them, it would be more easy to misdiagnose it as a fusion beat.
However, the fusion beat arises due to fortuitous meeting of a supraventricular impulse and ventricular impulse in the ventricle.
Therefore it is almost impossible to see fusion beats with similar morphology.
On the other hand, the ECG above shows two beats with
similar delta waves, suggesting intermittent preexcitation.

Dr. Sinan Altan Kocaman has donated the above ECG to our website.

Click here for a more detailed ECG