Sinus rhythm
（重定向自Normal sinus rhythm）
![Schematic representation of normal sinus rhythm showing standard waves, segments, and intervals](/Images/godic/202501/30/SinusRhythmLabels.svg2431.png")
![Example of a sinus rhythm with bifascicular block.](/Images/godic/202501/30/Bifascicular_block_ECG2431.png")
Sinus rhythm refers to any cardiac rhythm where depolarisation of the cardiac muscle begins at the sinus node. It is characterised by the presence of correctly-oriented P waves on the electrocardiogram (ECG). Sinus rhythm is necessary, but not sufficient, for normal electrical activity within the heart.