Sinus arrhythmias are characterized by which pattern?

• A. Regular rhythm with a constant rate
• B. Always causing chest pain
• C. An irregular rhythm linked to respiration
• D. Occurring only in diseased hearts

Answer: (C)

Respiratory sinus arrhythmia is a normal variation where the heart rate changes with the breathing cycle. The electrical timing from the SA node stays regular, but the intervals between beats lengthen and shorten with expiration and inspiration, respectively. In other words, the rhythm is irregular in the sense that the rate fluctuates in sync with breathing, being faster during inspiration and slower during expiration. This phenomenon is commonly seen in healthy young people and does not indicate disease. It isn’t about chest pain and isn’t limited to diseased hearts.