Sinus arrhythmia is described as

• A. Slight irregularities due to respiration; benign
• B. A consistently regular rhythm with no variation
• C. An irregular rhythm due to electrolyte abnormalities
• D. Tachycardia

Answer: (A)

Sinus arrhythmia is a normal variation in heart rate that happens with breathing. The rhythm comes from the SA node, so the P waves and QRS complexes look normal, but the time between beats changes with respiration—heart rate rises a bit during inspiration and falls during expiration. This fluctuation is due to autonomic influences (vagal tone changing with the breathing cycle) and is considered benign, especially in younger people.

Think of the other options as describing different situations: a consistently regular rhythm with no variation isn’t showing the respiratory-linked change that defines sinus arrhythmia; an irregular rhythm from electrolyte problems would imply a metabolic or electrolyte issue rather than a breathing-related pattern; tachycardia refers to a persistently fast rate, not the normal, slow-to-moderate variation tied to respiration.