Which of the following is an example of an escape beat?

Which of the following is an example of an escape beat?

• A. Atrial escape beat
• B. AV escape beat
• C. Ventricular contraction
• D. Sinus beat

Answer: (A)

An escape beat refers to a cardiac impulse that originates from a subsidiary pacemaker when the primary pacemaker (usually the sinus node) fails to fire for a brief period. Specifically, the atrial escape beat occurs when the normal pacemaking activity of the sinus node is interrupted, often due to sinus bradycardia or a transient pause in sinus activity, prompting an alternative pacemaker in the atria to generate a beat.

In this context, the atrial escape beat serves to maintain heart rhythm by ensuring that the heart continues to contract, albeit from a different site than usual. It is typically characterized by a P wave that is different in morphology from sinus beats, indicating its different origin in the atria, followed by a normal QRS complex.

The other types of beats mentioned in the choices are not classified as escape beats. For example, an AV escape beat is generated from the atrioventricular node and would be considered a specific type of escape beat, but it is not classified as 'atrial.' Ventricular contraction, or a ventricular escape beat, arises from the ventricles and typically occurs when both atrial and junctional impulses fail. Lastly, a sinus beat originates from the sinus node, the primary pacemaker, and does