Sinus arrhythmia is a variation in the heart's sinus rhythm, usually caused by changes in a person's breathing cycle. It's a common finding, especially in children and young adults, and its ...

Sinus rhythm (a.k.a. normal sinus rhythm) refers to the normal heart beat originating from the sinoatrial node. This is manifested as an upright P wave in lead II of the ECG. Sinus bradycardia ...

Sinus arrhythmia refers to a changing sinus node rate with the respiratory cycle, on inspiration and expiration. This is quite common in young, healthy individuals and has no clinical significance.

In fact, up to 60% of athletes demonstrate ECG changes (in isolation or in combination) such as sinus bradycardia, sinus arrhythmia, first-degree atrioventricular (AV) block, early repolarisation, ...