Physiology of venous return. An unappreciated boost to the heart.

Adequate cardiovascular function depends on the control of venous tone as well as cardiac contractility, heart rate, vascular resistances, and an adequate blood volume. Venous tone is a major determinant of cardiac preload, a clinically important factor influencing cardiac function, especially during cardiac failure. In this review, vascular capacitance, venous tone, and venous return are discussed, and the concepts relating them to cardiovascular function are summarized. Active venoconstriction or dilation provides a rapid compensation, equivalent to a change in blood volume, for cardiovascular homeostasis.