Validity and reliability of aortic pulse wave velocity and augmentation index determined by the new cuff-based SphygmoCor Xcel

Abstract

Aortic pulse wave velocity (AoPWV) and augmentation index (AIx) are commonly used measures of large elastic artery stiffness and wave reflection, respectively. Recently, a new cuff-based SphygmoCor device (Xcel) has been developed to measure both AoPWV and AIx. We sought to examine the following: (1) the validity of Xcel compared with the well-validated tonometry-based SphygmoCor device (MM3); (2) the intratest and day-to-day reliability of Xcel; (3) the influence of body side (right or left) on Xcel measurements; and (4) the relation of Xcel measurements to carotid artery compliance, distensibility and β-stiffness index. We found that measurements of AoPWV and AIx between Xcel and MM3 were not different (P=0.26 and P=0.43, N=22 and 26, respectively) and were strongly related (r=0.85 and 0.75, P<0.0001), and based on Bland-Altman plots there was good agreement between them. Intra-test (intraclass correlation=0.996 and 0.983, P<0.0001; AoPWV and AIx, N=24 and 26, respectively) and day-to-day reliability (intraclass correlation=0.979 and 0.939, P<0.0001) were high. Xcel AoPWV and AIx on the left versus right body side were not different (P=0.19 and P=0.58, N=14 and 15, respectively) and were highly correlated (r=0.99 and 0.94, P<0.0001). AoPWV and AIx measured with Xcel were positively related with β-stiffness index (r=0.62 and 0.51, P< or = 0.005, N=23 and 24, respectively) and negatively related with distensibility (r = -0.58 and -0.44, P < or = 0.02, N=23 and 24, respectively). In conclusion, Xcel measures of AIx and AoPWV are valid, highly reliable and not affected by body side. Xcel is a useful tool for use in research and the clinic.