Which PR interval pattern is associated with junctional rhythms?

Which PR interval pattern is associated with junctional rhythms?

• A. Short or long
• B. Normal
• C. Absent
• D. Prolonged to more than 0.20 s

Answer: (A)

When the rhythm starts from the AV junction, the timing of atrial depolarization relative to the ventricular depolarization can vary. This makes the PR interval—the time from the start of the P wave to the start of the QRS complex—not fixed. The atria can be activated just before the ventricle, leading to a shorter PR interval, or after the ventricle due to retrograde atrial conduction, yielding a longer PR interval or even a P wave that isn’t clearly seen before the QRS. Because of this variability, the PR interval pattern in junctional rhythms can be shorter than normal or longer than normal, rather than consistently normal.

When the rhythm starts from the AV junction, the timing of atrial depolarization relative to the ventricular depolarization can vary. This makes the PR interval—the time from the start of the P wave to the start of the QRS complex—not fixed. The atria can be activated just before the ventricle, leading to a shorter PR interval, or after the ventricle due to retrograde atrial conduction, yielding a longer PR interval or even a P wave that isn’t clearly seen before the QRS. Because of this variability, the PR interval pattern in junctional rhythms can be shorter than normal or longer than normal, rather than consistently normal.