What might a single junctional escape beat produce on an EKG?

What might a single junctional escape beat produce on an EKG?

• A. An absent P wave before the QRS complex.
• B. An inverted P wave immediately before or following the QRS complex.
• C. A wide QRS complex without any preceding waves.
• D. A premature beat with normal atrial depolarization.

Answer: (B)

A single junctional escape beat typically results from a transient failure of the sinoatrial (SA) node to generate an impulse, allowing the junctional tissue (the area around the AV node) to take over pacing for that beat. The most characteristic manifestation of a junctional escape beat on an EKG is the presence of an inverted P wave. This P wave may occur either immediately before or after the QRS complex, depending on the timing of the junctional impulse relative to the ventricular depolarization.

In patients with a junctional escape rhythm, normal atrial depolarization is often unreliable due to the failure of the SA node; therefore, the junctional focus can depolarize the ventricles directly. The inverted P wave indicates retrograde conduction through the atria, as the impulse travels upward from the junction towards the atria, which is not the typical conduction pathway seen with normal sinus rhythm. This characteristic change is why option B correctly describes what is observed on the EKG with a junctional escape beat.

The other choices do not adequately reflect the nature of a junctional escape beat. For example, absent P waves suggest a complete failure of heart electrical activity from the atria, while a wide QRS complex typically indicates