Premature Junctional Contractions features?

• A. Late, wide QRS with no compensatory pause
• B. Random early junctional beats with QRS ≤0.10 s and long compensatory pause
• C. Atrial flutter with ventricular response
• D. Sinus rhythm with occasional early P waves

Answer: (B)

Premature junctional contractions come from the AV junction, so they show up as early beats that use the normal ventricular conduction pathway. That keeps the QRS narrow (usually 0.10 seconds or less). The P waves are often not seen or are inverted and can appear after the QRS because the impulse travels retrogradely to the atria. After such a premature beat, the next sinus beat is delayed, producing a longer-than-usual pause before the next regular beat. These features—an early junctional beat, a narrow QRS, and a longer compensatory pause—best describe premature junctional contractions.

This differs from a premature ventricular contraction, which would have a wide QRS; from atrial flutter with ventricular response, which has a rapid, sawtooth atrial pattern; and from sinus rhythm with occasional early P waves, which would be premature atrial contractions.