Figure 2.

(A) Healthy aging is a means to retard brain, kidney, and heart damage. Indeed, in healthy subjects, an impedance mismatch occurs in response to the stiffness gradient between proximal elastic arteries and distal muscular arteries. This phenomenon generates pressure wave reflection, limiting the transmission of pressure pulsatility to target organs. The largest part of the reflected pulsatile energy that propagates backward, toward the heart, travels indeed at low velocity along elastic arteries, thus do not superimpose on incident pressure wave. Thus, central BP remains normal. From Laurent and Cunha (23) with permission. (B) Wave reflections in the elderly. When the aorta stiffens with aging, it loses its ability to dampen the pulsatility of ventricular ejection. Small arteries of target organ are damaged by the hyperpulsatility. Because the stiffness of distal muscular arteries does not change with age, there is a reduction of the stiffness gradient between proximal elastic arteries and distal muscular arteries. Thus, pressure pulsatility is transmitted to a larger extent toward small arteries of target organs. The largest part of the reflected pulsatile energy that propagates backward, toward the heart, travels at high velocity along stiff arteries. TRhus, it superimposes on incident pressure wave and increase central SBP. From Laurent and Cunha (23) with permission.