Adult Echocardiography Practice Exam

During what part of the cardiac cycle does active filling occur?

1. During QRS complex

2. Just after the QRS complex

3. Immediately after the P wave

4. Immediately after the T wave

The correct answer is: Immediately after the P wave

Active filling of the heart refers primarily to the phase in which the atria contract to push blood into the ventricles. This action occurs during diastole, specifically following atrial depolarization, which manifests as the P wave on the electrocardiogram (ECG). When the P wave appears, it indicates that the atria are depolarizing and preparing to contract. This contraction leads to the active filling of the ventricles with blood. In this context, the timing is crucial: the mechanical contraction of the atria and their resultant active filling of the ventricles take place just after the P wave, before the electrical activity of the ventricles initiates, represented by the subsequent QRS complex. The other phases mentioned in the choices occur at different times in the cardiac cycle or are associated with different events. The QRS complex signifies the depolarization of the ventricles, leading to their contraction, while the T wave represents ventricular repolarization. Active filling specifically does not occur during these phases, as they are focused on ventricular activity rather than atrial filling functions. Thus, identifying the correct point in the cycle associated with atrial contraction is vital in understanding the dynamics of cardiac filling.