The arterial circulation is a network that delivers oxygen and nutrients to cells. Blood flow is achieved by means of a muscular pump but diffusion plays a key role at a cellular level necessitating a branching structure where no cell is more than ∼25microm from a capillary.¹

The design of the cardiovascular system is subject to a variety of ‘constraints’ and ‘costs’. It has been postulated that the design of the arterial network might be understood in terms of the need to minimize competing ‘costs’ within the context of physical or material limits to the system.² These designs can also be envisaged as being subservient to space filling or fractal considerations.³ The signalling mechanisms underlying these designs remain to be fully characterised, although shear stress, wall tensile stress and metabolic stimuli are likely candidates.^4,5 I will also review evidence that deviations from a minimal cost condition or optimal design may provide both a measure of disease severity and insights into the underlying disease mechanism.