Large arteries haemodynamics: conduit versus cushioning function.

Arterial system has two distinct interrelated functions: to deliver an adequate supply of blood to organs and tissues--the conduit function, and to smooth the pressure and flow pulsation resulting from intermittent ventricular ejection in order to transform oscillatory hemodynamics into a steady flow and pressure--the cushioning function. The conduit function depends principally on low resistance of conduit arteries, i.e. on the radius of the vessel. Atherosclerotic plaques causing more or less important reduction in the caliber of arteries are the principal cause of altered conduit function. The efficiency of cushioning function depend on geometric and viscoelastic properties of arterial system described in terms of compliance or stiffness. Stiffening of the arteries induces principally an increase in left ventricular hypertrophy and alterations in coronary flow distribution. Arteriosclerosis characterised by diffuse fibroelastic thickening is the principal cause altering cushioning function. Arteriosclerosis is a physiological aging phenomenon which is accelerated in several conditions including principally those characterised by increased blood pressure.