Physiology, Cardiac Preload

Also termed left ventricular end-diastolic pressure (LVEDP), preload is a measure of the degree of the ventricular stretch when the heart is at the end of diastole. Preload, in addition to afterload and contractility, is one of the three main factors that directly influence stroke volume (SV), the amount of blood pumped out of the heart in one cardiac cycle. Affected by changes in venous tone and circulating blood volume, changes in preload directly affect stroke volume, therefore influencing cardiac output and the overall function of the heart. A thorough understanding of preload, what affects it, and how pharmacological treatments can manipulate preload is essential to understanding overall cardiac physiology.