CHAPTER 22: Atrioventricular Block
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In most clinical instances, complete AV block is at least partly compensated by an
escape rhythm originating from an area distal to the site of the block. However, complete
AV block of sudden onset may cause syncope with catastrophic results, or even sudden
death, when there is no escape rhythm (Fig. 22.8). As seen in the figure, P waves occur
immediately after the T waves, and the first two P waves are conducted without even
first-degree block, but the third and all subsequent P waves are not conducted at all. Thus,
third-degree AV block need not be preceded by first- or second-degree AV block.
V1
F I G U R E 2 2 . 8 .
A lead V1 rhythm strip from elderly patient on telemetry monitoring during
hospitalization following an episode of syncope.
Arrows
indicate the continuing sinus tachycardia
before and after the onset of complete AV block.
