the frank–starling law of the heart (also known as starling's law and the frank–starling mechanism) represents the relationship between stroke volume and end diastolic volume. the law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end diastolic volume), when all other factors remain constant. as a larger volume of blood flows into the ventricle, the blood stretches the cardiac muscle fibers, leading to an increase in the force of contraction. the frank-starling mechanism allows the cardiac output to be synchronized with the venous return, arterial blood supply and humoral length, without depending upon external regulation to make alterations. the physiological importance of the mechanism lies mainly in maintaining left and right ventricular output equality.