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).

  The 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.

Click here for a more detailed ECG





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.

Click here for a more detailed ECG





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.

Click here for a more detailed ECG





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.

Click here for a more detailed ECG