What does the P-wave represent in an ECG?

The P-wave in an electrocardiogram (ECG) specifically represents atrial depolarization. This phase occurs when the electrical impulse generated by the sinoatrial (SA) node causes the atria to contract and push blood into the ventricles. The P-wave is the first deflection seen on the ECG and is typically a small, rounded waveform resulting from this depolarization process.

When the atria depolarize, sodium ions flow into the atrial muscle cells, and this change in electrical state leads to muscle contraction. Understanding the role of the P-wave is critical in interpreting heart rhythms and diagnosing potential dysfunctions in atrial activity. The morphology and timing of the P-wave can provide insight into atrial size, rhythm abnormalities, and other cardiac conditions.