What is the correct interpretation of the P wave in an electrocardiogram?

The P wave represents the graphical representation of all the electrical forces that occur during atrial depolarization.
The presence of positive P waves in lead II, anterograde, and in a 1:1 relationship with the QRS complexes are the three characteristics that define a sinus rhythm.
Changes in the duration and voltage of the P wave of the ECG may suggest enlargement (fundamentally dilation) of the atria.
The duration and voltage of the P wave can vary significantly depending on the weight of the animal and the degree of training to which it is subjected.