EMS 12-Lead: The 12 Rhythms of Christmas – Type I AV-Block

This article is the fifth in our latest series, The 12 Rhythms of Christmas, where each day we examine a new rhythm disorder. It’s a continuation of the theme behind last year’s 12 Leads of Christmas.

Type I AV-block is a pretty interesting phenomenon, first described in 1899 by Dutch anatomist Karel Wenckebach. It is characterized by progressive lengthening of the PR-intervals that culminates in a dropped (fully blocked) P-wave and a pause in the ventricular rhythm, reseting the AV-node so that the cycle can repeat.

Let’s look at an example:

Even those with limited experience in basic dysrhythmias should be able to identify the increasing PR-intervals…

That, however, is where most folks’ knowledge ends. But I expect most of the folks reading this blog, if they don’t already, would like to understand why this pattern occurs.

For the rest of this article please follow this link or click the rhythm strips above.

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