Most patients respond well to standard diuretic therapy, usually at the costs of impaired renal function. Based on the assumption that clinically overt fluid overload is the result of progressive fluid accumulation, current European Society of Cardiology (ESC) and American College of Cardiology Foundation/American Heart Association (ACCF/AHA) guidelines recommend a correction of volume status using diuretics, to reduce the total fluid volume. However there is no consensus on how to define fluid overload quantitavely.