Introduction: Augmentation index (AI) measures the contribution that wave reflection makes to the arterial pressure waveform. AI is considered a surrogate marker for the stiffness of the arterial system; however its utility in atrial fibrillation (AF) is unknown. The AI is routinely recorded from the radial artery (rAI). AI can also be calculated from the fingertips by peripheral arterial tonometry (patAI). Therefore we sought to determine whether AI calculated from patAI provides similar information to that of rAI in patients with AF.
Methods: Thirty-five consecutive patients with paroxysmal AF (age 59 ± 12) were examined during sinus rhythm. For each subject, rAI and patAI were recorded using radial applanation tonometry (SphygmoCor) and using peripheral arterial tonometry (EndoPat2000).
Results: Overall, rAI (19 ± 13%) was significantly (p < 0.005) higher than patAI (9 ± 21%) but both indices were highly correlated to each other. The R value was 0.79 (p < 0.0001) and the R-squared value was 0.62 (Fig. A). Bland–Altman plot of the difference between the two techniques (patAI-rAI values) versus their mean demonstrates that patAI under-estimates augmentation index (Fig. B). The bias calculated over the range of averaged concentrations was −10%, however, it is not constant over this range.
Conclusion: AI can be measured by radial artery tonometry and peripheral arterial tonometry. There is a good correlation between the AI calculated from both techniques; the lack of uniform bias between the values suggests that the two techniques are not interchangeable as estimates of arterial stiffness in patients with AF.
© 2011 Published by Elsevier Inc.