What does the P wave in an ECG signify?

The P wave in an ECG signifies atrial contraction. This waveform represents the depolarization of the atria, which is the electrical activity that leads to the contraction of the atrial muscles. When the sinoatrial (SA) node fires, an electrical impulse travels through the atria, causing them to contract and push blood into the ventricles. This contraction is essential for effective heart function and occurs just before the QRS complex, which represents ventricular depolarization.

Understanding the function of the P wave is crucial because it indicates how well the atria are functioning in their role of filling the ventricles with blood. If there were abnormalities in the P wave, it could suggest atrial enlargement or other atrial defects, which could impact overall cardiac performance.