Sinus arrhythmia in children is characterized by which pattern?

• A. The heart rate increases with inspiration and decreases with expiration
• B. The heart rate decreases with inspiration and increases with expiration
• C. The heart rate remains constant during breathing
• D. The heart rate increases with expiration and decreases with inspiration

Answer: (A)

Respiratory sinus arrhythmia is a normal variation in pediatric heart rate tied to breathing. The heart rate speeds up during inspiration and slows during expiration because of autonomic modulation: inspiration reduces vagal (parasympathetic) tone to the SA node, allowing the rate to rise, while expiration increases vagal tone, slowing the rate. On a tracing, the interval between beats shortens with inspiration and lengthens with expiration, yet the rhythm stays regular. This pattern is especially common in children due to higher vagal tone and is considered a benign finding rather than a sign of pathology.