Evaluation of the calculation formulas of the cardio-ankle vascular index used in the Japanese apparatus

Background: Recently, coefficients in the equation of cardio-ankle vascular index (CAVI) used in VaSera (R) device were disclosed. This study aimed to simulate the influence of adjusting the coefficients in the equation of CAVI and also aimed to validate the equation. Methods: The CAVI displayed by VaSera (CAVIvs) and the CAVI estimated (CAVIes) with fixing the coefficients of the middle range of the heart-ankle stiffness parameter beta (ha beta) in the equation were compared. Moreover, the heart-ankle pulse wave velocity (haPWV) which corresponds to the low cutoff ha beta of 7.348 was estimated in various blood pressure patterns to validate the formula. Results: The CAVIvs was clearly lower than CAVIes in the low and the high range of CAVIvs. Moreover, it was virtually impossible to obtain the low cutoff ha beta of 7.348 by using typical values of haPWV. Conclusion: The CAVIvs in the high-range of VaSera underestimates the original property of stiffness parameter beta. Moreover, there will be also a missing information in the equations introduced in the corresponding article, especially in the calculation formula of CAVIvs from ha beta. Therefore, in order to make the best use of the nature of the stiffness parameter beta to be used in VaSera, fixing the coefficients or termination of its use should be considered.