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Premature Atrial Complex - Atrial Rhythms

Intro to PACs

  • PACs can occur for a number of different reasons i.e., diet, fatigue, stress, disease, ischemia to name a few.
  • Premature complexes frequently occur in bradycardic rhythms, but may occur almost any time.
  • PACs occur when an early electrical impulse occurs from a location in the atria other than the SA node.

Intro to PACs 2

  • This early impulse causes an early cardiac complex which disrupts the underlying rhythm.
  • The locus of stimulation being different, results in a change in the morphology of the P wave.
  • PACs can occur occasionally or frequently.
  • PACs ECG can be observed with or without a pattern
  • The P wave with PAC's will always be upright

EKG Analysis

pacs ecg image

Notice the following: the R to R interval is irregular, the fifth complex is early and the P wave on the early complex is a different shape.

EKG Practice Strip

atrial ecg image 2

Analyze this tracing using the five steps of rhythm analysis.

Show Answer
  • Rhythm: Irregular
  • Rate: 50
  • P wave: Upright & uniform (except early complexes - biphasic)
  • PR interval: 0.16 second
  • QRS: 0.08
  • Interpretation: Sinus Bradycardia with PACs

Authors and Sources

Authors and Reviewers


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