What is primarily represented by the QRS complex on an ECG?

The QRS complex on an electrocardiogram (ECG) primarily represents ventricular depolarization. This is a crucial electrical event during the cardiac cycle, as it indicates the process in which the ventricular myocardial cells become activated, leading to contraction. During ventricular depolarization, the electrical impulse travels through the ventricles, causing them to contract and pump blood to the lungs and the rest of the body.

This phase is preceded by atrial depolarization, reflected in the P wave, which is responsible for the contraction of the atria. Following the QRS complex, the T wave represents ventricular repolarization, which is the process by which the ventricles recover and prepare for the next cycle of depolarization.

Understanding the QRS complex is important in clinical practice, as abnormalities in its shape, duration, or amplitude can indicate various cardiac conditions, such as bundle branch blocks, ventricular hypertrophy, or ischemia.