Preload (cardiology)

Preload (Cardiology)

Preload in cardiology refers to the degree of stretch of the cardiac muscle at the end of diastole, immediately before contraction. It is directly related to the ventricular filling. The concept of preload is closely related to the Frank-Starling mechanism of the heart, which describes the relationship between the stroke volume and the preload.

Definition

Preload is defined as the initial stretching of the cardiac myocytes (muscle cells) prior to contraction. It is related to the sarcomere length at the end of diastole, just before the start of systole. The preload is often used synonymously with the end-diastolic volume, but they are not the same. The end-diastolic volume is a reflection of preload.

Physiology

The preload affects the force of the subsequent contraction due to the Frank-Starling mechanism. This mechanism states that the greater the volume of blood entering the heart during diastole (end-diastolic volume), the greater the volume of blood ejected during systolic contraction (stroke volume) up to a limit.

Clinical significance

In clinical practice, the preload can be altered by changing the patient's body position, by the use of certain medications, or by the administration of intravenous fluids. The preload is an important factor in determining the stroke volume of the heart. It is also a key factor in the management of many cardiovascular conditions, including heart failure and hypertension.

Measurement

The preload can be measured using various techniques, including echocardiography, cardiac catheterization, and magnetic resonance imaging (MRI). However, these methods are not always accurate and can be influenced by many factors.

See also

• Afterload
• Cardiac output
• Heart rate
• Stroke volume

References

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