Characterization of arterial wave propagation and reflection in mice

Wave propagation through the arterial system changes with age and disease state, and mutant mice are often used to study these conditions. We have developed several noninvasive ultrasonic techniques to measure blood velocity and vessel wall motion from which we can calculate aortic pulse wave velocity (PWV), local compliance, impedance spectra, characteristic impedance (Z _c), augmentation index (AI), and forward and backward waves in intact anesthetized mice. We found altered vascular mechanics in many mutant strains of mice. In old mice PWV, AI, and Z_c are increased. In atherosclerotic mice PWV, Zc, and AI are increased; peripheral resistance and arterial compliance are decreased; and wave reflections are enhanced. We find that the initial deceleration of carotid velocity is caused by peripheral reflections, and that increased acceleration of velocity in the aortic arch in atherosclerotic mice is caused by enhanced carotid reflections returning to the heart and traveling forward in the aorta. We conclude that when scaled for heart period, the mouse arterial system and its responses to age and disease are similar to those in man. The ability to evaluate arterial mechanics in mice will expand their use as models to study human arterial diseases and conditions.