Define preload and describe the determinants of preload.

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College Answer

A definition based on stretch of the isolated myocyte prior to contraction, and 
extrapolation to the human heart, was expected. Surrogate measures of preload 
used in clinical practice needed to be explained and related to the definition (for 
example, end-diastolic volume and central venous pressure). The Frank-Starling 
Law was relevant to discussion of the significance of preload to cardiac performance.
A diagram illustrating the interaction of important factors would have been helpful in 
answering this question. At a minimum, detail should have included atrial 
contractility, diastolic filling time, ventricular compliance, and the determinants of 
venous return.
Better answers included discussion of the effects of afterload, arrhythmias, and 
valvular pathology. A distinction between the factors determining left and right
ventricular preload would have demonstrated a more sophisticated understanding of 
the physiology.
Syllabus: C1c, 2b,c.
Reference: Cardiovascular Physiology, Berne and Levy, p64-65