The relationship between large artery stiffness, wave reflection and pulsatility in the micro-circulation: new insights into the management of both hypertension and diabetes

Abstract

Objective: Increased arterial stiffness is associated with a reduced buffering capacity of the large arteries, therefore predisposing the microcirculation to increased flow and pressure pulsatility. However, increased wave reflection may be protective, by reducing the amount of pulsatility transmitted to the microcirculation. The aim of this study was to examine this hypothesis by exploring the relationship between large artery stiffness, wave reflections and pulsatility in the microvasculature. Design and Method: 67 volunteers, aged 64 ± 10 years, not taking any sympathomimetic compounds and free from any acute ocular symptoms participated. Aortic pulse wave velocity (aPWV) and augmentation index (AIx) were recorded using the SphygmoCor system as measures of large artery stiffness and wave reflection, respectively. Retinal artery resistance index (RI), a measure of early retinal organ damage and pulsatility ratio (PR), a measure of retinal artery pulsatility were recorded using doppler ultrasound (Aloca). Results: aPWV was significantly associated with RI (R = 0.43,P = 0.001) and PR (R = 0.54,P = < 0.001) whereas AIx was significantly and inversely related to RI (R = -0.26,P = 0.047) and PR (R = -0.33, P = 0.011, respectively). Stratifying individuals according to tertile of aPWV and AIx revealed that RI and PR were significantly higher in those individuals with high aPWV but low AIx, compared with individuals with low aPWV and high AIx (0.51 ± 0.13 vs 0.37 ± 0.06, P = 0.004,RI; and 2.2 ± 0.61vs1.6 ± 0.20; P = 0.008, PR). Conclusions: Increased large artery stiffness is implicated in microcirculatory damage. However, increased wave reflections may exert a protective effect. Future mechanistic studies linking the macro and micro-circulations may provide important insights into the management of conditions such as hypertension and diabetes.