The Frank–Starling law (also known as Starling’s law of the heart) states that the strength of ventricular contraction is dependent on the length of the resting fibres. In other words, when all other factors are kept constant, an increase in left ventricular preload causes stroke volume (SV) to increase, without the need for extrinsic neural or humoral regulatory mechanisms. As left ventricular preload (i.e. left ventricular end-diastolic volume, LVEDV) is difficult to measure, left ventricular end-diastolic pressure (LVEDP) is often used as its surrogate marker. The relationship between SV and LVEDP is nonlinear (Figure 30.1).