Which best describes a sinus arrhythmia on an EKG?

A sinus arrhythmia is characterized by an irregular rhythm that is associated with the respiratory cycle. In particular, it features varying R-R intervals on the EKG, which correspond to the heart rate increasing with inhalation and decreasing with exhalation. This phenomenon typically occurs in healthy individuals, particularly in younger populations, and reflects the normal autonomic nervous system response to breathing.

The presence of P waves is expected in a sinus arrhythmia, as they should be present before each QRS complex, indicating that the rhythm is still originating from the sinus node. The varying R-R intervals are crucial, as they highlight the irregularity in the timing of the heartbeats, unlike in a regular rhythm where the intervals would be consistent.

Other descriptions provided do not adequately capture the essential features of a sinus arrhythmia. For instance, a regular rhythm with absent P waves suggests a different underlying issue, more indicative of atrial fibrillation or other supraventricular arrhythmias. Varying intervals between P waves would imply a different pathological condition, such as atrial flutter or other forms of atrial irregularity. An irregular rhythm with consistent PR intervals does not correlate with sinus arrhythmia, as it suggests other types of arrhythmias that