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 on an EKG appears as a normal sequence of sinus cycles followed by an absent P wave during the pause. This characteristic is indicative of the failure of a sinus impulse to propagate, leading to a missed heartbeat. In a typical sinus rhythm, each P wave precedes a QRS complex, representing the electrical activity initiating from the atria. When a sinus block occurs, the normal rhythm is interrupted, resulting in a gap where a P wave should be, followed by a return to the normal sinus rhythm.

This characteristic appearance helps distinguish a sinus block from other arrhythmias, such as a complete block or other forms of atrial dysfunction, where patterns and pauses might differ significantly from what is seen in a simple sinus block. Recognizing the absence of the P wave in the context of an otherwise regular rhythm is key to identifying this specific phenomenon on the EKG.