The next step in the orderly approach for 12-lead ECG interpretation is determination of the rhythm.
Sinus rhythm
For determination of heart rhythm as part of our interpretation of the ECG, we should now define sinus rhythm. In sinus rhythm, the rate is between 60-100 beats per minute, every normal P wave should be followed by a QRS, and the P wave must be upright in leads I and II, and inverted in lead aVR. At this time, we should mention the rhythm as sinus; if an arrhythmia is present, this should be mentioned instead of sinus rhythm.