What is a common manifestation of a sinus block on an EKG?

What is a common manifestation of a sinus block on an EKG?

• A. Irregularly spaced heartbeats
• B. Prolonged PR intervals followed by a flatline
• C. A normal rhythm followed by a missed beat with no P wave
• D. Consistent ventricular beat with absent atrial activity

Answer: (C)

A common manifestation of a sinus block on an EKG is characterized by a normal rhythm followed by a missed beat where there is no P wave. In a sinus block, there is a temporary interruption in the conduction of impulses from the sinus node, resulting in the failure of the atria to activate during the blocked interval. This means that the P wave corresponding to that missed beat is absent, but the surrounding heartbeats maintain a normal sinus rhythm.

This phenomenon typically occurs when the sinus node is functioning normally before and after the block, reinforcing the idea that the inherent rhythm of the heart remains unchanged outside the blocked period. The presence of the missed beat helps clinicians recognize that the block specifically occurred at the level of the sinus node due to the lack of activity during that time.

Other manifestations, such as irregularly spaced heartbeats or prolonged PR intervals followed by a flatline, do not align with the classic presentation of a sinus block. They may suggest different arrhythmias or conduction issues, which further distinguishes sinus block as a unique finding in EKG interpretation.