| Background and Objective:Morbidity and mortality in cardiovascular disease are related primarily to structural and functional alterations of the arterial wall. Changes in the arterial wall can lead to increased arterial stiffness, which has been shown to influence cardiovascular prognosis adversely. Thus, measuring arterial stiffness has been recommended in the preventative management of cardiovascular disease. To examine arterial elastic properties, pulse wave analysis has been used increasingly in clinical studies as it is a simple and reproducible non-invasive technique. Pulse wave analysis measures augmentation index, a parameter that reflects the degree to which central arterial pressure is enhanced by wave reflection of the pulse wave. It should be clarified that AI estimated at the level of the aorta may have a good linear correlation with AI at the level of the radial artery, but they are not confirmed. The aims of the present study were three aspects:to investigate whether the radial augmentation index is correlated with cardiovascular risk; to characterize the main determinants of radial augmentation index in general population of china and to compare the differences in radial augmentation index between blood pressure groups.Material and Methods:In a population-based cross-sectional study of 4985 subjects (2417men and 2568 women) aged 18-96 years (50.9±14.7 years, mean±SD) from Beijing, Each participant was interviewed and completed a standardized questionnaire and physical examinations. Blood was withdrawn for the determination of blood biochemistry and oral glucose tolerance test; AI was measured in the left radial artery using tonometry Colin HEM-9000AI; Automatic pulse wave velocity measuring system (Complior SP, France) was applied to examine carotid-femoral PWV (CFPWV) and carotid-radial PWV (CRPWV) as the parameters reflecting central elastic large arterial and peripheral muscular medium sized arterial elasticity respectively. Subjects were divided into six subgroups according to their brachial blood pressure level as suggested from the classification of the ESH2007 report. All analyses were conducted using SPSS (version 13, SPSS Inc., Chicago, Illinois).Results:Radial augmentation index significantly increased with increasing risk scores and was significantly correlated to not only the Framingham risk scores (r=0.50, P< 0.01) but also the 10-year risk prediction models for ischemic cardiovascular disease (r=0.43, P<0.01). Radial AI showed an association with carotid-femoral PWV (r=0.25, P<0.01), but there was no significant relationship between radial AI and carotid-radial PWV (r=-0.05, P>0.05). The average value of rAI in Chinese healthy subjects was 74.22%±15.03%. Radial AI was significantly higher in women than in men (79.52%±13.06%compared with 68.59%±14.93%, P<0.001). rAI was positively related to age in healthy men and women (r= 0.526, P<0.001, and r= 0.545, P<0.001, respectively). rAI increased with age up to median age of 50 years in men and 60 years in women but plateaued thereafter. The reference values were established in the different age groups. Stepwise regression analysis revealed that age (positive), diastolic blood pressure(positive), smoking(positive), heart rate (inverse), height(inverse), waist circumference (inverse) and fasting blood glucose (inverse) were independent determinants of radial AI in women; While in men, it was also determined by total cholesterol (positive).Both in general population and in treated hypertensive subjects, Radial AI gradually and significantly increased from the subgroup with the lower blood pressure to the subgroup with higher blood pressure, even after adjustment for age, gender, heart rate and waist circumference.Conclusions:Radial augmentation index may be a useful marker of cardiovascular risk. rAI showed an association with carotid-femoral PWV, but there was no significant relationship between radial AI and carotid-radial PWV. Radial AI seemed to be influenced by age and gender in healthy subjects, it is higher in women than men, so the reference values should be established in the different age groups respectively; This study showed that the incremental value of rAI as an important measurement of arterial compliance may be particularly relevant in younger subjects. These findings indicate that rAI is determined by many factors such as arterial stiffness,distance to the reflection point and reflection coefficient. So it is necessary to take into account these confounding factors when assessing AI as an index for atherosclerosis. Arterial elasticity gradually and significantly decreased from the subgroup with the lower blood pressure to the subgroup with higher blood pressure, both in general population and in treated hypertensive subjects. These results suggest that antihypertensive treatment strategies with more beneficial effects on arterial properties are needed.
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