Advanced Patient Assessment Practice Exam

In which part of the cardiac cycle does the most blood flow into the ventricles?

1. Atrial diastole

2. Ventricular systole

3. Atrial systole

4. Isovolumetric relaxation

The correct answer is: Atrial systole

The phase of the cardiac cycle during which the most blood flows into the ventricles is during atrial systole. During this period, the atria contract, actively pushing blood into the ventricles. This phase occurs just before the ventricles begin to contract, ensuring they are filled to their maximum capacity. Atrial systole accounts for about 10-20% of the total ventricular filling, especially important in situations where the heart is beating rapidly or if there is decreased ventricular compliance. During this phase, the atrioventricular valves (the mitral and tricuspid valves) are open, allowing the blood flow from the atria into the ventricles to occur efficiently. In contrast, during the other options: ventricular systole is when the ventricles contract to eject blood into the aorta and pulmonary artery, thus no filling occurs; isovolumetric relaxation is a phase following ventricular contraction where all valves are closed and no blood enters the ventricles; and atrial diastole occurs when the atria are filling with blood from the veins, but this is not the phase when the maximum amount of blood enters the ventricles. Therefore, recognizing atrial systole as the phase where the most blood flows into the ventricles