What is the P Wave? || EMS Cardiology

Although the general public may not know, EMS providers are trained as to what those little squiggly lines on the 12 lead actually indicate. It is paramount to understand what each of the electrical manifestations mean in order to note when something may not be right.

Gross abnormalities from a "normal" EKG are important to note as they may give the provider a chance to catch anything from a heart attack to an electrolyte imbalance and treat accordingly.

The first little wave of the sinus rhythm is the P wave. The p wave represents the depolarization of the atria. What does that actually mean? Learning early on that the word depolarization can be used in the place of contraction will help you tremendously! When the top chambers of the heart (the atria) squeeze/contract/depolarize, the P wave is manifested onto the 12 lead. Side note: A normal P wave is typically going to be .12 s (3 small boxes) or smaller.

A normal P wave is much smaller than the QRS complex, why is that?

Let's think about the anatomy of the heart! The atria are the smaller, upper chambers of the heart and the ventricles are the larger, muscular, lower chambers of the heart. It would only make sense that a forceful squeeze from the bigger, more muscular chambers of the heart would produce a larger manifestation (in normal circumstances). 

There is typically no EMS treatments for p wave abnormalities and they can have a variety of causes, a significant one is right/left atrial enlargement. The enlargement of the the atria can change the morphology of the p wave drastically and can indicate the patient has other very serious medical conditions......but we will save that for a future post.