Validity of the augmentation index and pulse pressure amplification as determined by the SphygmoCor XCEL device: a comparison with invasive measurements.

Augmentation index (AIx) and pulse pressure (PP) amplification can be determined by the SphygmoCor XCEL device in an operator-independent manner. This study aimed to examine its validity against invasive measurements. Simultaneous recordings of central aortic pressure waveforms were performed with oscillometric and high-fidelity invasive methods in 35 patients who underwent coronary arteriography. Brachial blood pressure was also recorded using the two methods. AIx for the aortic pressure waveform was defined as the ratio of augmentation pressure to PP. PP amplification was defined as the ratio of brachial PP to aortic PP. The differences between the invasive and oscillometric measurements were -7.7±12.7% for AIx and 0.17±0.14 for PP amplification (mean±s.d.). Strong correlations between the invasive and oscillometric measurements were found in both indices (AIx: r=0.75; PP amplification: r=0.80; both P<0.001). The Bland-Altman plot showed a proportional bias of PP amplification, but not of AIx (AIx: r=-0.21, P=0.23; PP amplification: r=-0.61; P<0.001). In conclusion, estimated AIx may be reliable considering the high correlation between the invasive and noninvasive values and the lack of proportional bias against invasive assessment. However, a substantial underestimation and a large scatter of estimated AIx were also observed. Further studies using the device to investigate associations with target organ damage or prognoses are needed to clarify its clinical validity.