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. 2006 Summer;53(2):53–64. doi: 10.2344/0003-3006(2006)53[53:FOEI]2.0.CO;2

Figure 8.

Figure 8

Junctional rhythm. There are no P waves and a PR interval cannot be ascertained. Therefore, the sinoatrial node is not pacing this rhythm. But the QRS complexes are narrow, so the pacemaker is above the ventricles. The logical conclusion is that the atrioventricular node or neighboring tissue is pacing the heart. This is called junctional rhythm. Because this node has a slower firing rate than the sinoatrial node (See Figure 1), rates of 50 and 90 are the cutoffs for bradycardic and tachycardic rates, ie, junctional bradycardia or tachycardia.