preload

1. The load to which a muscle is subjected before shortening. 2. SYN: ventricular p..

- ventricular p. formerly, the end-diastolic pressure stretching the ventricular walls, which determines the end-diastolic fiber length at the onset of ventricular contraction, or some other measure of this load on the muscle fibers before contraction; now, more rigorously expressed in terms of the wall stress at this moment, related to the tension per unit cross-sectional area in the ventricular muscle fibers (calculated by Laplace law from internal radius and pressure modified by wall thickness) that balances this transmural pressure at the moment before contraction begins. SYN: p. (2).

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pre·load -'lōd n the stretched condition of the heart muscle at the end of diastole just before contraction

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pre·load (preґlōd) the mechanical state of the heart at the end of diastole, the magnitude of the maximal (end-diastolic) ventricular volume or the end-diastolic pressure stretching the ventricles, calculated as: in isolated cardiac muscle, the force stretching the resting muscle to a given length prior to contraction; in the intact heart, the stress on the ventricular wall at the end of diastole, determined largely by the venous return, total blood volume and its distribution, and atrial activity. It is usually measured as left ventricular end-diastolic volume.