What is the definition of sinus arrhythmia?

Sinus arrhythmia refers specifically to a variation in heart rate that occurs during the breathing cycle. This physiological phenomenon is typically characterized by an increase in heart rate during inhalation and a decrease during exhalation. It is most commonly observed in children and young adults, and it often reflects a normal variation associated with autonomic nervous system activity. Since it occurs due to the influence of breathing on heart dynamics, this makes it a normal response rather than a pathological condition, distinguishing it from conditions like dangerous heart conditions or electrical malfunctions. Sinus arrhythmia is often considered a benign variation and can be a normal finding on an EKG, particularly in healthy individuals.