Wenckebach without a pause!

This week we had a Holter monitor recording reported as complete heart block. For obvious reasons this can be a serious diagnosis, but the reporting cardiologist felt it was Wenckebach sequences and requested a review.

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Wenckebach sequences almost always have a generous pause at the termination of a sequence.

In the above example, the blocked P wave extends the R to R interval from about 1000 ms to 1900 ms.

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Sometimes this interval is shorter when the preceding PR interval becomes very long and the blocked P wave occurs immediately following the previous T wave.

Can the pause disappear?

In the following tracing, there is no pause because the blocked P wave is concealed within the QRS of the previous beat. which has a very long PR interval (or is it a junctional escape beat?).

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