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ECG Findings

  • Bradycardia, typically with a rate of 40 to 60 bpm.

  • The QRS complex is narrow, < 120 ms.

  • P waves are absent, retrograde, very slow, or unrelated to the QRS complex.

Pearls

  1. When the atria fail to initiate a cardiac rhythm, or when no pacing signal reaches the lower AV node, the AV node or His bundle usually picks up the pacemaking responsibility.

  2. P waves may be conducted retrograde and buried in the T wave, as seen in this example.

  3. If a bundle branch block is also present, the QRS may be wide and may be difficult to discern from a primary ventricular rhythm.

FIGURE 23.25A

Junctional Rhythm with Retrograde P Waves. (ECG contributor: James V. Ritchie, MD.)

FIGURE 23.25B

The QRS is narrow. P waves are not present before the QRS. In this example, the signal that originated in the His bundle is conducted retrograde through the AV node into the atria, and retrograde P waves are apparent in the ST segment (arrows).

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