This results in an upright P wave in lead II on the ECG. If there is a P wave before every QRS complex, and it has a sinus morphology, then normal sinus rhythm, or NSR, is said to be present.

First, the standard 12-lead ECG is a 10-second strip. The bottom one or two lines will be a full “rhythm strip” of a specific lead, spanning the whole 10 seconds of the ECG. Other leads will ...