Diagnostic criteria

  PR interval is not fixed. There is gradual prolongation of the PR interval, and after a few beats one of the P waves cannot be conducted to the ventricles. Thereafter, the cycle restarts.

  Some P waves are not followed by a QRS complex ( dropped beat).

  Block is at the level of atrioventricular (AV) node.

  2:1 AV block is generally accepted as a variant of the Wenkebach phenomenon.




ECG 1. Gradual prolongation of the PR interval. Blocked (non-conducted) P waves are shown by arrows.

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ECG 2. 2:1 AV block in a patient with coronary artery disease. Blocked P waves are shown by arrows.
Narrow QRS complexes suggest Wenkebach type 2:1 AV block.

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ECG 3. Holter recording shows Wenkebach phenomenon. PR interval gradually prolongs and
the 5th beat from the left is not conducted . The cycle restarts and PR interval gradually prolongs again .

Dr. Gulay Copur has donated the above ECG to our website.

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ECG 4. The ECG above belongs to a 65 years-old woman complaining of dizziness. There is Mobitz Type 1 (Wenkebach) AV
block. After a non-conducted (dropped) P wave the cycle restarts and PR interval prolongs gradually .
The third P wave fails to be conducted again (dropped beat) .

Dr. Nezire Gullu has donated the above ECG to our website.

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ECG 5. The ECG above belongs to a 6 months-old baby with a large, non-restrictive VSD.
Congenital 2:1 atrioventricular block with ventriculophasic sinus arrhythmia is seen.

Pediatric cardiologist Dr. Mahmut Gokdemir has donated the above ECG to our website.

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