What is preload?

Preload refers to the volume of blood in the ventricles at the end of diastole, just before the heart contracts. This volume stretches the ventricular myocardium, which is the muscle tissue of the heart. The greater the volume of blood that fills the ventricles, the more they are stretched, leading to a stronger contraction due to the Frank-Starling mechanism. This phenomenon highlights the relationship between the amount of blood returning to the heart (venous return) and the force of contraction during systole (heart muscle contraction).

Understanding preload is essential for grasping the overall mechanics of the heart and how it functions efficiently as part of the cardiovascular system. It plays a critical role in determining cardiac output, which is the total volume of blood the heart pumps per minute. A proper understanding of preload can inform approaches to managing various heart conditions that affect filling pressures and volumes.