Venous return is the rate of blood flow back to the heart.
Under steady-state conditions, venous return must equal cardiac output (Q), when averaged over time because the cardiovascular system is essentially a closed loop.
Although the above relationship is true for the hemodynamic factors that determine the flow of blood from the veins back to the heart, it is important not to lose sight of the fact that blood flow through the entire systemic circulation represents both the cardiac output and the venous return, which are equal in the steady-state because the circulatory system is closed.
[2] It is often suggested that venous return dictates cardiac output, effected through the Frank Starling mechanism.
It is confusion about these terms that has led some physiologists to suggest that the emphasis on 'venous return' be turned instead to more measurable and direct influences on cardiac output such as end diastolic pressure and volume which can be causally related to cardiac output and through which the influences of volume status, venous capacitance, ventricular compliance and venodilating therapies can be understood.