Preload (cardiology)

As the relaxed ventricle fills during diastole, the walls are stretched and the length of sarcomeres increases.

Sarcomere length can be approximated by the volume of the ventricle because each shape has a conserved surface-area-to-volume ratio.

Preload is estimated from end-diastolic ventricular pressure and is measured in millimeters of mercury (mmHg).

It is relatively straightforward to estimate the volume of a healthy, filled left ventricle by visualizing the 2D cross-section with cardiac ultrasound.

[2] This technique is less helpful for estimating right ventricular preload because it is difficult to calculate the volume in an asymmetrical chamber.

The end diastolic pressure of the right ventricle can measured directly with a Swan-Ganz catheter.