How does a sinus block appear on an EKG?

How does a sinus block appear on an EKG?

• A. Normal cycles followed by an absent P wave in the pause
• B. All cycles are normal without any pauses
• C. Regular P waves with varying intervals between beats
• D. A rapid succession of P waves

Answer: (A)

A sinus block occurs when the sinus node generates impulses normally, but one or more of these impulses fail to reach the atrial tissue, leading to a pause in the heartbeat. This is reflected on an EKG as normal cycles followed by a period where a P wave is absent during the pause. Essentially, you will see a series of normal P waves followed by a complete absence of a P wave for the duration of the block, after which the sinus rhythm resumes.

This pattern distinguishes a sinus block from other arrhythmias, making it clear that while the sinus node is functioning correctly, there is a temporary failure in the transmission of the impulse. This absence of the P wave during the pause is what solidifies the diagnosis of a sinus block on the EKG.