P2.12 Influence of the Central to Peripheral Arterial Stiffness Gradient on Timing and Amplitude of Wave Reflections

Abstract

In younger individuals peripheral muscular arteries are stiffer and pulse wave velocity (PWV_m) greater than central elastic artery stiffness and PWV_e (PWV_m>PWV_e). The marked increase in aortic stiffness with age, with little change in peripheral stiffness, results in a reversal of the arterial stiffness gradient (PWV_e>PWV_m). It has been hypothesized¹ that this may reduce wave reflection amplitude and augmentation index (AI_a) due to movement of the major reflection site further from the heart. To test this hypothesis we investigated whether a reverse stiffness gradient (PWV_e >PWV_m) is associated with a reduced AI_a and an increased reflection site distance.

Studies were performed in subjects aged>50 years who were free of medication. Following 10mins supine rest, blood pressure, pulse wave analysis and carotid-femoral (PWV_e) and femoral-dorsalis-pedis (PWV_m) PWVs were measured. Distance to the major reflection site was calculated from PWV_e and reflected wave travel time (Tr/2)².

PWV_e and PWV_m were 7.8±1.0m/s and 9.7±1.0m/s, respectively, in subjects with a positive stiffness gradient (PWV_m>PWV_e) and 10.8±2.1m/s and 9.0±1.6m/s in subjects with a reverse stiffness gradient. Central pulse pressure and augmentation pressure were higher in subjects with a reverse stiffness gradient (38 ± 18vs.48±9mmHg and 12±6vs.14±5mmHg, P<0.05), as was AI_a corrected for heart rate (23±8vs.27±6%.P<0.05) and reflection site distance (56±10vs.76±15cm. P<0.01). Time to reflection did not differ between groups (71.4±6.4vs.70.5±5.0ms).

Reversal of the stiffness gradient (PWV_e>PWV_m) is associated with increased central pulse pressure, reflected wave amplitude and AI_a and a paradoxical increase in reflection site distance.