Preload and afterload

Preload is end volumetric pressure that stretches the left ventricle of the heart. Preload=LVEDP INTO LVEDR DEVIDED BY 2h LVEDP=LEFT VENTRICULAR END DIAsTOlic pressuse and LVEDR=LEDE SAME R(RADIUS)at ventrical midpoint..........Afterload is measurement of tension produced by a specific chamber of heart...thanks