Sinus rhythm
From Ganfyd
(SR) Normal heart rhythm with each beat triggered by regular depolarisation in the sino-atrial node, and passing from there after atrial contraction to the atrio-ventricular node and thence to trigger ventricular depolarisation and contraction.
Conventionally the rate must be above 59 sinus bradycardia and below 100(?) sinus tachycardia.
Another normal rhythm is sinus arhythmia, where the rate of the SA node hunts slightly with time. If this is very excessive consider whether it is sick sinus syndrome
