Preload

In cardiac physiology, preload is the end volumetric pressure that stretches the right or left ventricle of the heart to its greatest geometric dimensions under variable physiologic demand. In other words, it is the initial stretching of the cardiac myocytes prior to contraction; therefore, it is related to the sarcomere length at the end of diastole. And since we can’t measure the ideal length of the cardiac sarcomere, other parameters (i.e. ventricular end diastolic volume or pressure ) are used. Passive filling of the (heart) ventricle and subsequent atrial contraction thus allows an echocardiographically volumetric measurement. Preload is theoretically most accurately described as the initial stretching of a single cardiomyocyte prior to contraction. This cannot be measured in vivo and therefore other measurements are used as estimates. Estimation may be inaccurate, for example in a chronically dilated ventricle new sarcomeres may have formed in the heart muscle allowing the…