Which part of the heart is depolarized during the QRS complex?

The QRS complex on an electrocardiogram represents the depolarization of the ventricles, which is a critical phase of the cardiac cycle. During this time, the electrical impulse travels through the Bundle of His and into the Purkinje fibers, causing the ventricles to contract and pump blood to the lungs and the rest of the body.

It's important to recognize that this phase coincides with the rapid and powerful contraction of the ventricles, which is necessary for effective circulation. While the atria do depolarize during the cardiac cycle, this occurs shortly before the QRS complex and is reflected in the P wave, which is associated with atrial depolarization.

In summary, the QRS complex specifically indicates ventricular activity, marking the key moment when the ventricles are stimulated to contract following depolarization. Understanding this waveform is essential for interpreting heart function and diagnosing any potential cardiac issues.