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. A sinus morphology is an upright P wave in lead II and ...

Sinus bradycardia occurs on an ECG when there is a normal upright P wave in lead II ― sinus P wave ― preceding every QRS complex with a ventricular rate of less than 60 beats per minute.

There were also signs of a late-arriving, "extra" P-wave phase, in addition to the normal initial P-waves captured by the stations in Spain. "Initially, we were not aiming to better understand the ...