75
NORMAL SINUS RHYTHM
The heart's normal electrical rhythm. The SA node fires at 60–100 bpm, impulses conduct normally through the atria, AV node, and ventricles.
ECG Features
Regular rhythm. Upright P wave before every QRS. PR interval 120–200 ms. Narrow QRS (<120 ms). Each P followed by a QRS.
Clinical Significance
Normal finding. No intervention required.