Direct means of obtaining CAVI0-a corrected cardio-ankle vascular stiffness index (CAVI)-from conventional CAVI measurements or their underlying variables

Objective: Cardio-ankle vascular index (CAVI) as measured using the VaSera device (CAVI(VS), Fukuda Denshi), has been proposed as a stiffness index that does not depend on blood pressure. We have recently shown theoretically that CAVI(VS) still exhibits blood pressure dependence, and proposed the corrected index CAVI(0). The present study aims to establish a method of calculating CAVI(0) either (i) from VaSera-reported values of cardiac-brachial and brachial-ankle pulse transit times (tb and tba, respectively) and blood pressure, or (ii) directly from CAVI(VS). To derive this method, the relationship among CAVI(VS) and its scale constants a and b, tb, tba, and blood pressure has to be established. Approach: From data of 497 subjects, eight candidate CAVI parameters were defined and calculated, containing all combinations of left or right tb/tba/blood pressure. Candidates were evaluated through correlation with measured left and right CAVI(VS). Correlations were compared statistically. Once the correct candidates were determined, two constants (a and b) required for converting CAVI(VS) to CAVI(0) were estimated through linear regression. Main results: Left and right CAVI(VS) are calculated using left and right tba; however, both left and right CAVI(VS) are calculated using right brachial blood pressures and right tb. Constants a and b for conversion of CAVI(VS) to CAVI(0) were estimated to be 0.842 [0.836 0.848] and 0.753 [0.721 0.786] (mean [95%CI]), respectively. Equations to estimate CAVI(0) from CAVI(VS), and to directly calculate CAVI(0) from the VaSera output are provided in this paper, as well as in a directly usable spreadsheet supplement. Significance: Our results permit straightforward calculation of CAVI(0) during a study, as well as retrospective estimation of CAVI(0) from CAVI(VS) in already published studies or where the original transit time values are not available, paving the way for thorough comparison of CAVI(0) to CAVI(VS) in clinical and research settings. Novelty and significance Cardio-ankle vascular index (CAVI) as measured using the VaSera device (CAVI(VS), Fukuda Denshi), has been proposed as a blood pressure-independent arterial stiffness index. We have recently shown theoretically that CAVI(VS) still exhibits pressure dependence, and proposed a corrected index, CAVI(0). In the present study, we derived equations to directly obtain CAVI(0) using data from the VaSera device. Our results permit straightforward calculation of CAVI(0) during a study, as well as retrospective estimation of CAVI(0) from CAVI(VS) in already published studies, paving the way for thorough comparison of CAVI(0) to CAVI(VS) in clinical and research settings.