Comparison of photoplethysmographic and arterial tonometry-derived indices of arterial stiffness.

Arterial tonometry is a method to assess arterial stiffness and has become a valuable tool in the stratification of cardiovascular risk. The arterial tonometry-derived augmentation index (AIx) is a marker of arterial stiffness and an independent predictor of mortality. As the AIx is relatively cumbersome to obtain, simpler methods such as analysis of pulse waves obtained by digital photoplethysmography have been proposed to estimate arterial stiffness. The objective of this study is to compare the usefulness of the stiffness index (SI) derived from digital photoplethysmography and the AIx derived from radial tonometry for stratification of cardiovascular risk. We studied 83 subjects with a heterogeneous cardiovascular risk profile and determined the ability of the two devices to differentiate subjects with low from subjects with high cardiovascular risk estimated by the Europe (EU)-heart score. Failure rate in both devices was similar (3.6%). AIx and SI were modestly correlated (r=0.48, P<0.001) and both indexes correlated with the EU-score (r=0.54, P<0.001) and (r=0.56, P<0.001), respectively. Both devices discriminated accurately between subjects with high cardiovascular risk (upper tertile of the EU-score) and low cardiovascular risk (lower tertile). However, only the SI differentiated significantly between subjects with intermediate risk (middle tertile) and high risk (upper tertile). Compared with the AIx, assessment of the SI derived by digital photoplethysmography is simple and possibly yields an advantage in risk stratification of subjects with intermediate and high cardiovascular risk. Therefore, digital pulse wave analysis may be a valuable tool to estimate arterial stiffness in large clinical studies.