Does the p wave represent first electrical pulse?

The P wave does represent the first electrical impulse of the cardiac cycle. It arises from the sinoatrial node, which is the natural pacemaker of the heart located in the right atrium. This electrical signal spreads through the atria, causing them to contract. The P wave is observed on an electrocardiogram (ECG), a graphical record of the electrical activity of the heart, as a small, upward deflection. It precedes the QRS complex, which represents the electrical activation of the ventricles and is associated with the subsequent forceful contraction of the heart chambers.