Influence of the central-to-peripheral arterial stiffness gradient on the timing and amplitude of wave reflections

In individuals with compliant aortas, peripheral muscular artery stiffness exceeds central elastic artery stiffness. With aging, central stiffness increases with little change in peripheral stiffness, resulting in a reversal of the normal stiffness gradient. This reversal may reduce the wave reflection amplitude due to the movement of the major 'effective' reflection site further from the heart. To test this phenomenon, we investigated the relationship among arterial stiffness gradients (normal and reversed), wave reflection amplitude and reflection site distance. Subjects aged ≥50 years were recruited from the Anglo-Cardiff Collaborative Trial. Central stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV). In Study 1, peripheral PWV was also measured in the arm (carotid-radial pulse wave velocity) and, in Study 2, in the leg (femoral-dorsalis pedis). Reflection site distance was calculated from cfPWV and the reflected wave Tr. Subjects were dichotomized into those with a normal stiffness gradient (peripheral >central PWV) or a reversed gradient (peripheral <central PWV). In Study 1, the reflection site distance was greater in subjects with a reversed gradient (P<0.01), whereas time-to-reflection was lower (P<0.001). Both the augmentation pressure (P<0.001) and augmentation index (P<0.05) were greater in subjects with a reversed gradient. In Study 2, the augmentation pressure, augmentation index and reflection site distance were greater in subjects with a reversed stiffness gradient (P<0.01, P<0.05 and P<0.01, respectively), and time-to-reflection was not different between groups. A reversed arterial stiffness gradient is associated with an increased reflection site distance, and a paradoxical increase in reflected wave amplitude and augmentation index.