Final answer:
Preload is the stretch on the heart's ventricles before they contract, influenced by venous return and affecting cardiac output through the Frank-Starling mechanism. It's a crucial factor considered in treatments related to cardiac performance and conditions.
Step-by-step explanation:
Preload refers to the end-diastolic volume that stretches the right or left ventricle of the heart to its greatest geometric dimensions under variable physiologic demand. In simpler terms, it is the initial stretching of the cardiac myocytes (heart muscle cells) prior to contraction, therefore it's related to the volume of blood returning to the heart that fills the ventricles before they contract. This factor can greatly affect cardiac output, which is the volume of blood that the heart ejects in one minute.
Characteristics and Aspects Related to Preload
Preload is dependent on the venous blood return to the heart and is influenced by factors such as total blood volume and venous tone.
It affects stroke volume and therefore cardiac output by following the Frank-Starling mechanism, where an increase in preload can lead to an increased force of contraction, up to an optimum point.
Alterations in preload can be clinical indicators of various cardiac conditions and are managed by interventions that modify venous return or ventricular filling.