What does the QRS complex represent in an ECG?

The QRS complex is a crucial component of the electrocardiogram (ECG) that specifically represents ventricular depolarization. During this phase, the electrical impulses spread through the ventricles, causing them to contract and pump blood to the lungs and the rest of the body. The QRS complex reflects the rapid movement of electrical activity across the ventricles and is usually characterized by a sharp, significant spike on the ECG tracing.

In contrast to the other processes mentioned, atrial contraction occurs before the QRS complex, represented by the P wave. Atrial filling is a passive process that happens during diastole when blood flows into the atria, while ventricular filling primarily occurs in the early diastole phase and is also prior to the QRS complex. Therefore, recognizing that the QRS complex is directly associated with the depolarization and subsequent contraction of the ventricles is essential for interpreting ECGs accurately.