This article is the seventh 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.
While most everyone has heard of first degree, type I, type II, and complete AV-block, comparatively few people recognize 2:1 AV-block as a valid rhythm diagnosis in its own right. That’s a shame, because 2:1 AV-block is a rather interesting finding. To understand why, consider the following dilemma:
- Type I AV-block presents with progressively increasing PR-intervals until a P-wave is blocked
- Type II AV-block presents with fixed PR-intervals until a P-wave is blocked
It should be clear from the two examples above (and the others in this series) that both forms of AV-block can present with various—and actively varying—conduction ratios: 5:4, 4:3, 3:2, etc… That doesn’t affect our ability to diagnose the rhythms, and in fact, it can be helpful to see how the PR-intervals behave with different ratios of P-waves to QRS-complexes.
- What do you do, however, when every-other P-wave is blocked?
For the rest of this discussion please follow this link or click on the rhythm strips above.