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Introduction ⬇

Recognizing wandering pacemaker

Rhythm

  • Atrial: Varies slightly, with an irregular P-P interval
  • Ventricular: Varies slightly, with an irregular R-R interval

Rate

  • Varies, but usually within normal limits or less than 60 beats/min

P wave

  • Altered size and configuration from changing pacemaker site with at least three different P-wave shapes visible
  • May be absent or inverted or occur after QRS complex if impulse originates in the AV junction

PR interval

  • Varies from beat to beat as pacemaker site changes
  • Usually less than 0.20 second
  • Less than 0.12 second if the impulse originates in the AV junction

QRS complex

  • Duration and configuration usually normal because ventricular depolarization is normal

T wave

  • Normal size and configuration

QT interval

  • Usually within normal limits

Other

  • May be difficult to differentiate wandering pacemaker from PACs


Distinguishing wandering pacemaker from PACs

Because PACs are common, you may miss a wandering pacemaker rhythm unless you examine the rhythm strip carefully. You may find it helpful to look at a rhythm strip that's longer than 6 seconds.

Wandering pacemaker

  • Carefully examine the P waves. You'll be able to identify at least three different shapes of P waves (see shaded areas above) in a wandering pacemaker.
  • Keep in mind that the atrial rhythm varies slightly, with an irregular P-P interval. The ventricular rhythm varies slightly as well, with an irregular R-R interval. These slight variations result from the changing site of impulse formation.

PACs

  • Keep in mind that the PAC occurs earlier than the sinus P wave, with an abnormal configuration when compared with a sinus P wave (see shaded area above).
  • It's possible, although rare, to see multifocal PACs that originate from multiple ectopic pacemaker sites in the atria. If this happens, the P waves may have different shapes.
  • Except for the irregular atrial and ventricular rhythms that result from the PAC, the underlying rhythm is usually regular.


What Causes It ⬆ ⬇

  • Increased parasympathetic (vagal) influences on the SA node or AV junction
  • COPD
  • Digoxin toxicity
  • Inflammation of atrial tissue
  • Valvular heart disease

What to Look for ⬆ ⬇

  • Usually no symptoms (patient is unaware of the arrhythmia)
  • Pulse rate normal or less than 60 beats/min
  • Rhythm regular or slightly irregular
  • At least three distinct P-wave configurations (distinguish wandering pacemaker from PACs)

How It's Treated ⬆

  • Usually, no treatment is needed if the patient has no symptoms.
  • If the patient has symptoms, his medication regimen should be reviewed and the underlying cause of the arrhythmia investigated and treated.
  • Monitor the patient's heart rhythm.
  • Observe the patient for evidence of hemodynamic instability, such as hypotension and changes in mental status.