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 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 ...

The rhythm is either sinus rhythm or not sinus rhythm. Sinus rhythm refers to the origination of the electrical activity coming from the sinus node — also known as the sinoatrial node, or SA node.