Relationship Between Brachial-Ankle Pulse Wave Velocity And Autoregulation Of Blood Flow In Retrobular Arteries

Objective: Recent studies showed that there is a close relationshipbetween either pulse pressure or large artery stiffness and small/microvasculardamage in heart, brain and kidney in hypertensive patients. This observationprompted some investigators to propose a concept of large/small arterycross-talk; however, whether the ocular vessels, ones of the target organs ofhypertension, involve such a cross-talk has not yet been reported, nor themechanisms underlining such a cross-talk has well understood. It has beenobserved that large artery stiffening was associated with endothelialdysfunction and, on the other hand, it well-known that endothelial functionplays an important role in the autoregulation of ocular blood flow. This study,therefore, was to determine whether there were any associations between thelarge artery stiffness and autoregulation of blood flow in retrobular arteriesand, if it is, whether such an association could be mediated by endothelialfunction in primary hypertensive patients.Methods: Forty primary hypertensive patients were enrolled into the study.Large arterial stiffness was estimated by measuring brachial-ankle pulse wavevelocity (baPWV) with an automatic waveform analyzer, autoregulation ofblood flow in retrobular arteries was evaluated by determining percentagechange of peak systolic velocity (PSV), end diastolic velocity (EDV) andresistive index (RI)(PSV%， EDV and%RI%, respectively) in the centralretinal artery (CRA) supplying the retinal and posterior ciliary artery (PCA)supplying the choroids with a color Doppler imaging before and after posturechange. Endothelial function was assessed by brachial artery flow-mediateddilation (FMD). A linear correlation analysis was used to analysis ofcorrelation between baPWV and the indexes of blood flow autoregulation, anda multivariate regression analysis was performed to assess the effect of the related factors including, in particular, FMD, on the associationaforementioned.Results:1. When changing from a seated to a supine position, ophthalmic arterypressure increased significantly from85.16±12.34mmHg to105.15±12.54mmHg (P<0.001), PSV and EDV increased significantly inboth CRA and PCA, RI decreased significantly in PCA and, as the onlyexception, RI in CRA was not significantly altered.2. The results of linear correlation analyses showed that, in the CRA, baPWVwas significantly correlated with both PSV%(r=0.331, P=0.037) and EDV%(r=0.477, P=0.002), but not with RI (r=-0.154, P=0.342); in thePCA, no significant correlations were found between baPWV and PSV%(r=2.19, p=0.175), EDV%(r=0.306, P=0.055) or RI%(r=-0.071,P=0.663).3. The results of multivariate regression analyses indicated that, in the crudemodel for the associations between baPWV and PSV%and EDV%(Model A), after adjustment for age, sex, blood pressure measurements(systolic blood pressure, diastolic blood pressure, pulse pressure and meanblood pressure), intraocular pressure and high-sensitivity C-reactive protein(model B), the associations between baPWV and both PSV%and EDV%(β(95%CI):2.26(0.07;4.45); P=0.044and4.57(2.09;7.06);P=0.001, respectively) remained statistically significant. Furtheradjustment for FMD (Model C) did not materially alter the associationbetween baPWV and EDV%, but rendered the association betweenbaPWV and PSV%statistically nonsignificant. FMD explainedapproximately33%of the association between baPWV and PSV%.Conclusions: There is an independent correlation between large arterystiffness and autoregulation of blood flow in CRA in primary hypertensivepatients, and such an association is partially mediated by endothelial function.