PR interval and QRS complex of accelerated junctional rhythm

• A. PR >0.12 s and QRS ≤0.10 s
• B. PR ≤0.10 s and QRS ≤0.10 s
• C. PR ≤0.10 s and QRS >0.12 s
• D. PR >0.12 s and QRS >0.12 s

Answer: (B)

In accelerated junctional rhythm, the impulse starts near the AV node. That keeps ventricular activation through the normal conduction system, so the QRS complex stays narrow. The atrial signal often travels retrogradely or is hidden, so the P waves may appear after the QRS or be inverted, making the PR interval short or not easily measurable.

So the best description is a short PR interval (about 0.10 s or less) with a narrow QRS complex (0.10 s or less). The other patterns—long PR with normal or narrow QRS, or wide QRS—don’t fit a junctional rhythm, which is characterized by normal ventricular conduction (narrow QRS) and an absent or very short PR due to retrograde atrial activation.