Here's why:

* It's the first wave of the electrocardiogram (ECG). The P wave represents the electrical activity in the atria (the upper chambers of the heart) as they contract.

* It travels through the atria. The electrical signal travels through the atria, causing them to contract and pump blood into the ventricles.

* The speed of the P wave is influenced by factors like heart rate and conduction system health. However, in general, it's a faster wave compared to the QRS complex, which represents ventricular depolarization.

To be more specific:

* The P wave travels at approximately 0.1 meters per second.

* This speed is significantly faster than the QRS complex, which travels at around 0.5 meters per second.

However, the speed of the P wave is not the primary focus when interpreting an ECG. Instead, we focus on its shape, duration, and relationship to other waves to identify potential abnormalities in the heart's electrical activity.