What percentage of ventricular filling occurs with atrial contraction?

During the cardiac cycle, the process of ventricular filling consists of two main phases: passive filling and active filling. The majority of ventricular filling occurs passively due to the pressure gradient created when the atrioventricular valves open, allowing blood to flow from the atria to the ventricles. However, the final phase of this filling process is driven by atrial contraction, also known as atrial systole.

Atrial contraction contributes a significant but not overwhelming amount to the total volume of blood that enters the ventricles. Estimates typically indicate that approximately 20-30% of the total ventricular filling occurs as a result of this contraction. The correct figure based on physiological studies and cardiac function models suggests this is around 30%. This portion is particularly important during situations requiring increased cardiac output or during tachycardia, where the phase of passive filling might be reduced due to shorter diastolic intervals.

Understanding the role of atrial contraction emphasizes the importance of both mechanical and pressure dynamics in the heart's function, reinforcing how atrial contraction helps optimize ventricular filling and prepare the heart for effective pumping during the subsequent contraction phase.