Patient Care Technician (PCT) AAH Practice Exam

What does the QRS complex indicate in an ECG?

1. Depolarization of the atria

2. Repolarization of the atria

3. Depolarization of the ventricles

4. Repolarization of the ventricles

The correct answer is: Depolarization of the ventricles

The QRS complex in an electrocardiogram (ECG) represents the depolarization of the ventricles. This phase is crucial because it indicates the electrical activation of the ventricular myocardium, which is responsible for the contraction of the ventricles and the subsequent pumping of blood to the lungs and the rest of the body. During the QRS complex, the electrical impulse travels rapidly through the ventricles, leading to a powerful contraction. This is a key moment in the cardiac cycle, as it ensures that the heart effectively circulates blood throughout the body. By contrast, the depolarization of the atria is represented by the P wave, while the repolarization phases are indicated by the T wave and the absence of an appropriate waveform for atrial repolarization. Thus, understanding the QRS complex is fundamental for interpreting ECG readings and assessing cardiac function.