In the cardiac cycle depicted in an ECG, what does the QRS complex represent?

The QRS complex in an ECG represents ventricular contraction, making it a fundamental component of the cardiac cycle. It occurs after the P wave, which indicates atrial depolarization, and before the T wave, which depicts ventricular repolarization.

During the QRS complex, the electrical impulses rapidly travel through the ventricles, leading to their depolarization and subsequent contraction. This contraction is critical because it is responsible for pumping blood out of the heart—specifically from the right ventricle to the lungs and from the left ventricle to the rest of the body. Understanding this relationship is essential for interpreting an ECG, as it reveals important information regarding heart function and rhythm.