Sinus arrhythmia
Sinus arrhythmia is a commonly encountered variation of normal sinus rhythm. Sinus arrhythmia characteristically presents with an irregular rate in which the variation in the R-R interval is greater than 0.12 seconds. Additionally, P waves are typically mono-form and in a pattern consistent with atrial activation originating from the sinus node. During respiration, the intermittent vagus nerve activation occurs, which results in beat to beat variations in the resting heart rate. During inspiration the heart rate goes up, while during expiration, the heart rate goes down, being slowest at end-inspiration.
When present, sinus arrhythmia typically indicates good cardiovascular health.
