In EPS, an echo beat indicates retrograde atrial conduction following a ventricular event.

• A. Retrograde atrial conduction after a ventricular extrastimulus
• B. Antegrade conduction to the atria
• C. No conduction changes
• D. An electrical artifact

Answer: (A)

Echo beats show ventriculoatrial conduction: when a ventricular extrastimulus is delivered, the impulse can travel backward to the atria via the AV junction or a retrograde pathway, activating the atria after the ventricle and producing a second atrial depolarization. This retrograde atrial activation after a ventricular event is what an echo beat represents, so describing it as retrograde atrial conduction following a ventricular extrastimulus is the correct interpretation.

An antegrade conduction to the atria would imply atrial activation from the atria toward the ventricles, not after a ventricular event. No conduction changes would mean no retrograde activation, which contradicts the presence of an echo beat. An electrical artifact would not reflect true physiological retrograde conduction.