Sinus Arrhythmia

Sinus arrhythmia is a variant of sinus rhythm. During sinus arrhtyhmia there is much (>0.16 sec) variation in the consecutive RR intervals.

An example of an ECG with sinus arrhythmia. This was a young patient without any symptoms. This sinus arrhythmia is often observed in young people and is related to in and expiration

Another example of sinus arrhythmia