Starling's law of the heart

Starling's law of the heart, also known as the Frank-Starling law, is a physiological principle that describes how the heart's stroke volume changes in response to changes in venous return. It was first described by physiologists Ernest Starling and Otto Frank in the early 20th century.

Overview

The law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end diastolic volume) when all other factors remain constant. This is due to the inherent property of heart muscle fibers; as they are stretched, they contract with greater force. This relationship between stroke volume and end diastolic volume is often depicted graphically as the Frank-Starling curve.

Mechanism

The mechanism behind Starling's law is related to the length-tension relationship in muscle physiology. As the heart fills with more blood, the cardiac muscle fibers are stretched, leading to an increased force of contraction. This is due to an optimal overlap of actin and myosin filaments, which results in a more powerful stroke.

Clinical significance

Understanding Starling's law is crucial in managing patients with heart failure. In conditions where the heart is unable to pump out the blood it receives, as in congestive heart failure, the curve flattens, indicating that the heart is operating at its maximum capacity and cannot increase its stroke volume in response to increased filling. This can guide treatment strategies, such as the use of diuretics to reduce blood volume and thus reduce the workload on the heart.

See also

• Cardiac physiology
• Heart failure
• Stroke volume
• Venous return

References

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