What does the QRS wave of an ECG represent?

The QRS wave of an electrocardiogram (ECG) represents ventricular depolarization, which is the electrical activation of the ventricles that leads to their contraction. During this phase, the electrical impulse rapidly spreads through the ventricles, causing them to contract and pump blood out of the heart—either to the lungs via the right ventricle or to the rest of the body via the left ventricle. The QRS complex is usually the most prominent part of the ECG waveform due to the mass of the ventricles compared to the atria.

This phase of the cardiac cycle is crucial because it influences cardiac output, heart rate, and overall heart function. Understanding the significance of the QRS wave allows for assessment of the heart's electrical activity and can indicate various conditions if abnormalities are present.