Which ECG finding is typical of junctional rhythm?

• A. P waves before QRS with normal PRI
• B. P waves after QRS with a long PRI
• C. P waves not present near QRS
• D. P waves lost or inverted near QRS

Answer: (D)

Junctional rhythm uses the AV junction as the pacemaker, so the impulse starts below the atria. That means atrial depolarization often occurs at the same time as, or after, the ventricles depolarize, causing the P waves to be hidden in or immediately adjacent to the QRS and often inverted if seen. So the typical ECG finding is P waves that are lost or inverted near the QRS complex, reflecting retrograde atrial activation from the AV junction. The QRS is usually narrow because ventricular conduction is intact, and the PRI is variable or not measurable when the P wave is not clearly preceding the QRS.