Diastolic Augmentation Index Improves Radial Augmentation Index in Assessing Arterial Stiffness

Arterial stiffness is an important risk factor for cardiovascular events. Radial augmentation index (AI _r ) can be more conveniently measured compared with carotid-femoral pulse wave velocity (cfPWV). However, the performance of AI _r in assessing arterial stiffness is limited. This study proposes a novel index AI _rd , a combination of AI _r and diastolic augmentation index (AI _d ) with a weight α, to achieve better performance over AI _r in assessing arterial stiffness. 120 subjects (43 ± 21 years old) were enrolled. The best-fit α is determined by the best correlation coefficient between AI _rd and cfPWV. The performance of the method was tested using the 12-fold cross validation method. AI _rd (r = 0.68, P < 0.001) shows a stronger correlation with cfPWV and a narrower prediction interval than AI _r (r = 0.61, P < 0.001), AI _d (r = -0.17, P = 0.06), the central augmentation index (AI _c ) (r = 0.61, P < 0.001) or AI _c normalized for heart rate of 75 bpm (r = 0.65, P < 0.001). Compared with AI _r (age, P < 0.001; gender, P < 0.001; heart rate, P < 0.001; diastolic blood pressure, P < 0.001; weight, P = 0.001), AI _rd has fewer confounding factors (age, P < 0.001; gender, P < 0.001). In conclusion, AI _rd derives performance improvement in assessing arterial stiffness, with a stronger correlation with cfPWV and fewer confounding factors.