Which rhythm represents a junctional escape rhythm, where the junctional pacemaker overtakes the normal pacemaker, often associated with AMI, open‑heart surgery, myocarditis, or digoxin toxicity, and is usually asymptomatic?

• A. Accelerated Junctional Rhythm
• B. Junctional Escape Rhythm
• C. Premature Junctional Complex
• D. First Degree Heart Block

Answer: (B)

When the primary pacemaker (the SA node) slows down or fails, the AV junction can take over as the heart’s pacemaker. This produces a junctional escape rhythm, a slower but steady rhythm meant to preserve heart activity. The rate is typically 40–60 beats per minute, and the atrial activity often isn’t seen as normal P waves; if P waves do appear, they are usually after the QRS or inverted, because the atria are activated retrogradely from the AV junction. The QRS complexes are usually narrow since ventricular depolarization proceeds normally once the impulse starts at the AV junction.

This rhythm reflects a protective backup mechanism that kicks in when the SA node is suppressed, which is common in conditions like acute myocardial infarction, after open-heart surgery, myocarditis, or digoxin toxicity. Because the rate sits in a relatively normal range and cardiac output can be maintained, many patients are asymptomatic.

Other rhythms either describe a single early junctional beat (not a sustained rhythm), a faster rate (accelerated junctional rhythm), or a conduction delay without a junctional escape mechanism (first-degree heart block).