At the end of diastole, which chambers contain the most blood?

At the end of diastole, the ventricles contain the most blood because this is the phase of the cardiac cycle where the ventricles are filling with blood just before they contract. During diastole, both the atria and ventricles are relaxed, allowing blood to flow from the atria into the ventricles. The amount of blood in the ventricles at this point is referred to as end-diastolic volume (EDV), which is typically greater than the blood volume in the atria.

The atria do fill with blood during diastole as well, receiving blood from the superior and inferior vena cavae into the right atrium and from the pulmonary veins into the left atrium. However, the total volume in the atria is less than what is contained in the ventricles by the end of diastole, as a significant volume of blood is being stored in the ventricles in preparation for the next systolic contraction.

Understanding this concept is crucial for interpreting filling pressures and ventricular function in echocardiography, as well as for assessing diastolic dysfunction conditions where filling dynamics may be altered.