Understanding venous return

Excerpt

Cardiac output can increase fivefold to adapt to changing metabolic needs. Since normal contraction empties the heart of nearly all its blood, simply increasing the force or rate of contraction cannot explain the dramatic increase in cardiac output. Instead, the circulation mobilizes a large volume of blood from the compliant veins. The venous system stores two-thirds of the blood volume and serve as an adjustable reservoir [1, 2]. The Starling law explains that cardiac output is intrinsically coupled to the rate of blood return to the heart [1]. To increase cardiac output, the circulation increases venous return—the rate of blood flowing from the systemic veins into the right atrium. This review will discuss the mechanisms that regulate venous return. …