Sinus arrhythmia refers to a changing sinus node rate with the repiratory cycle (inspiration and expiration). This is quite common in young, healthy individuals and has no clinical significance. The heart rate increases with inspiration (due to the Bainbridge reflex) and decreases with expiration.
The ECG criteria to diagnose sinus arrhythmia is a variation of the PP interval from one beat to the next of at least 0.12 seconds or 120 milliseconds. Sinus arrhythmia, if not in a young person and not occurring with respiration, may be a sign of sick sinus syndrome (SSS).
Atrial Arrhythmias ECG Quiz
1. Surawicz B et al. ACC/AHA recommendations for the standardization and interpretation of the electrocardiogra. Circulation. 2009;119:e235-240.
2. Chou's Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
By Steven Lome