What is an expected visual hallmark of junctional rhythm on an ECG?

• A. Shortened PR interval
• B. Inverted P waves
• C. Wide QRST complex
• D. Absent T waves

Answer: (B)

In junctional rhythm, the expected visual hallmark is the presence of inverted P waves. This is primarily due to the origin of the impulse, which arises from the junctional tissue (the atrioventricular junction), rather than from the sinoatrial (SA) node. As a result, the electrical activity is directed towards the atria instead of away from them, causing the P waves to appear inverted on the ECG—often before or after the QRS complex, or even buried within it.

This characteristic can help differentiate junctional rhythms from other types of arrhythmias. While changes in the PR interval, width of the QRS complex, and T-wave morphology are relevant in other contexts, they are not defining features of junctional rhythm. Understanding the position and orientation of the P waves in relation to the QRS complex is crucial in interpreting ECGs effectively.