What is the Origin of Cardiac Preload?

The concept is a cornerstone of cardiovascular physiology, rooted in the foundational Frank-Starling Law of the heart, which describes the relationship between end-diastolic volume and stroke volume. The term combines "cardiac," referring to the heart, with "preload," indicating the load or stretch placed on the muscle fibers before the contractile event. Its origin lies in the systematic study of the heart's intrinsic ability to adapt its output to the volume of venous return.

What is the Mechanism of Cardiac Preload?

Preload is mechanistically regulated by the venous return, which fills the heart chambers during the relaxation phase, diastole. Hormonal systems, including the renin-angiotensin-aldosterone system, significantly modulate circulating blood volume and vascular tone, thereby indirectly controlling venous return and preload. Increased preload stretches the ventricular sarcomeres to a more optimal length, which in turn leads to a more forceful contraction in the subsequent beat, a key homeostatic mechanism for maintaining adequate cardiac output.

Cardiac Preload ∞ Area

Cardiac Preload

Meaning

Cardiac Preload is a physiological measurement defined as the degree of myocardial fiber stretch at the end of ventricular diastole, immediately preceding the systolic contraction. Clinically, it is quantified by the end-diastolic volume or pressure of the ventricles, reflecting the volume of blood the heart must manage. This parameter is a primary determinant of stroke volume, integral to the Frank-Starling mechanism and overall circulatory efficiency.