A 24h ECG tracing of an 8-year old boy reveals the following sequence:
Looks like sinus rhythm. However, it skips one beat. Since the P wave is not followed by a QRS complex, you ultimately think of AV block (AVB).
Now, there are different types of AV block, including AVB I, AVB II/1, AVB II/2, AVB III, high grade AVB,...
From the tracing shown above you make the diagnosis of ...?
Now, when looking at the tracing you will notice the following:
1) the PR intervals of the beats following the blocked P wave increase (blue arrows)
2) the PR interval of the beat right before the blocked P wave is longer than the PR interval of the subsequent beat (red circles)
Both of these findings suggest AVB II type 1, showing Wenckebach periodicity.
Actually you only need to look at the PR interval before and after the blocked P wave to diagnose AVB II/1.
AVB II/1 is considered benign. Level of block is above the His-level of the conduction system. You may find AVB II/1 in healthy children and adolescent during sleep.
Causes of AVB: