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 ...

In this instance, the P wave morphology (normally generated when the SA node fires causing atrial depolarizaion) will be altered since its origin is no longer at the SA node and is instead at the ...