preload
The degree of ventricular stretch at the end of diastole, determined by venous return and ventricular compliance.
Full Definition
Preload refers to the initial stretching of cardiac muscle fibers prior to contraction, typically measured as the ventricular end-diastolic pressure or volume. It represents the amount of blood returned to the heart and determines the initial length of sarcomeres before systolic contraction begins. According to Frank-Starling mechanism, increased preload generally leads to increased stroke volume up to a physiological limit. Clinically, preload can be estimated through central venous pressure, pulmonary capillary wedge pressure, or echocardiographic measurements of ventricular filling.
Usage
Usage note: Distinguish clearly from afterload in hemodynamic discussions.
In Context
- "Diuretics reduce preload by decreasing venous return to the heart." — Pharmacology textbook
- "Assessment of preload is crucial in managing patients with acute heart failure." — Clinical management protocol