Wagner_Marriot's Practical Electrocardiography, 12e

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.

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.

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CHAPTER 22: Atrioventricular Block