Venous return curve

Venous return curve is a graphical representation of the relationship between the venous return (VR) and the right atrial pressure (RAP). It is a crucial concept in understanding the physiology of the cardiovascular system.

Overview

The venous return curve is a plot of the venous return (the volume of blood returning to the heart per unit of time) against the right atrial pressure. The curve is typically downward sloping, indicating that as the right atrial pressure increases, the venous return decreases. This relationship is due to the Starling's law, which states that the force of contraction of the heart is proportional to the initial length of the cardiac muscle fibers.

Determinants of the Venous Return Curve

The position and shape of the venous return curve are determined by two main factors: the mean systemic filling pressure (MSFP) and the resistance to venous return (RVR).

Mean Systemic Filling Pressure

The mean systemic filling pressure is the pressure in the systemic circulation when there is no blood flow. It is determined by the total blood volume and the compliance of the blood vessels. An increase in the blood volume or a decrease in the vessel compliance will increase the MSFP, shifting the venous return curve to the right.

Resistance to Venous Return

The resistance to venous return is determined by the resistance of the veins and venules. An increase in the RVR will decrease the slope of the venous return curve, indicating a decrease in the venous return for a given right atrial pressure.

Clinical Significance

The venous return curve is a useful tool in understanding the pathophysiology of various cardiovascular diseases. For example, in congestive heart failure, the venous return curve is shifted to the right due to an increase in the blood volume. This results in an increase in the right atrial pressure, leading to the symptoms of peripheral edema and jugular venous distension.

See Also

• Cardiac function curve
• Frank-Starling law
• Cardiac output