Relationship between radial artery augmentation index and central arterial stiffness

We studied relationships between radial artery augmentation index (AI) and central arterial stiffness, an identified risk factor of future cardiovascular diseases, in 49 males and 51 females (age: 19∼73 yrs). Radial artery AI was calculated from radial arterial pressure waveforms in supine and in sitting positions by applanation tonometry-based automated radial AI measurement device (HEM-9010AI, Omron). Carotid artery AI and aortic pulse wave velocity (PWV) were measured in supine resting by automated PWV measurement system (form PWV/ABI, Colin MT) as indices of central arterial stiffness. Radial AI measured in supine position correlated with counterparts measured in sitting position (r=0.931, P<0.0001). There was no significant difference in these indices (80.9 ± 17.5 vs. 81.0 ± 15.3, mean ± SD). Radial AI measured in supine position had a strong correlation with carotid AI (r=0.850, P<0.001) and a modest correlation with aortic PWV (r=0.472, P<0.0001) in whole subjects. Correlation coefficients between radial AI and aortic PWV were larger in males (r=0.588, P<0.0001) and females (r=0.553, P<0.0001) than that in whole subjects. The most used approach to obtain central arterial AI is to perform radial artery tonometry and then apply a transfer function to calculate the aortic pressure waveform from the radial waveform. Our results suggest that AI obtained directly from radial artery can give equivalent information of central arterial AI, regardless of measurement posture (i.e., lying and sitting).