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 ...

Less commonly, sinus arrhythmia may indicate an underlying medical problem, like heart disease or heart block. The heart's normal sinus rhythm is created by electrical signals that spread ...

then the term “ectopic atrial rhythm” is used. Because the origination of this electrical activity is not from the sinus node, the P wave would not have its normal sinus appearance ― that is ...