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Aim: The Cardio-Ankle Vascular Index (CAVI) is a stiffness index of the arterial tree from the origin of the aorta to the ankle, independent of blood pressure at the time of measurement. The CAVI equation includes the coefficients “a” and “b” to adjust it to the value of Hasegawa's pulse wave velocity, which is compensated for at 80 mmHg of diastolic pressure. To verify this adjustment with the coefficients, the clinical significance of CAVI and CAVI without the coefficients (ha β ) were compared in both an epidemiological study and an acute clinical study. Methods: In the epidemiological study, the significances of CAVI and ha β among people with or without coronary risks such as hypertension, dyslipidemia, hyperglycemia, and abnormal electrocardiography change, were compared. In the acute clinical study, nitroglycerin was administered to subjects in a control group and to coronary artery disease patients, observing CAVI and ha β values over a 20-min period. Results: There was no discrepancy in terms of statistically significant differences between CAVI and ha β among subjects with or without risk factors. Furthermore, there was also no discrepancy in terms of statistically significant differences between CAVI and ha β during the changes of those values following nitroglycerin administration over a 20-min period. Conclusion: In both the epidemiologic and clinical studies, there was no discrepancy in terms of significant differences between CAVI and ha β . These results suggest that both are valid as indices of stiffness of the arterial tree from the origin of the aorta to the ankle.

Original ArticleAim: The cardio-ankle vascular index (CAVI) represents the blood pressure-independent arterial stiffness from the origin of the aorta to the ankle. CAVI0 has been proposed as a variant index. We aimed to clarify the difference between CAVI and CAVI0 among large populations, and to explore reasons of the difference. Methods:The subjects were 5,293 Japanese healthy and 3,338 hypertensive people. Simple and multiple regression analyses were performed using age, sex, body mass index, systolic, and diastolic blood pressure (Pd) as variables. Sub-group analysis was performed by sex and age. The CAVI values with and without adjustment by reference pressure were also compared.Results: CAVI had a positive correlation with Pd, while CAVI0 had a negative correlation with Pd in the healthy population. The CAVI values of the hypertensive group were higher than those of healthy group in both men and women, but the CAVI0 values in women of the hypertensive group in the 30-39 age group was significantly lower than that of the corresponding healthy group. Differences of CAVI values with or without modification using the reference pressure were 1.09% 1.38% for the healthy group and 3.68% 1.66% for the hypertensive group.Conclusion: CAVI showed the expected values, but CAVI0 showed inexplicable results in the healthy and hypertensive populations. The differences were due to the strong dependency of CAVI0 on Pd. Differences of CAVI values with or without reference pressure were negligible. These results indicate that CAVI obtained by the VaSera system is appropriate, but CAVI0 is not. changes according to changes in blood pressure at the measuring time. This has been shown theoretically and also experimentally 4) . Therefore, PWV is an inappropriate index for research studying the effect of blood pressure on arterial stiffness.An attempt to establish an arterial stiffness index independent of blood pressure at measuring time was made by Hayashi et al. 5) . They found that the relationship between a change in vascular diameter and internal blood pressure showed an exponential curve,

Arterial stiffness is a good predictor of cardiovascular events. As a substitute for elastic modulus representing stiffness, pulse wave velocity (PWV) has been used for over a century as it is easy to measure; however, PWV is known to essentially depend on blood pressure at the time of measurement. The cardio-ankle vascular index (CAVI) is a relatively new index of global arterial stiffness of the origin of the aorta to the ankle arteries. The characteristic feature is its independency from blood pressure at the measuring time. Recently, a variant index CAVI 0 was proposed, which was claimed to be a more accurate arterial stiffness index than CAVI, considering independency from blood pressure. The purpose of this review is to evaluate the properties of CAVI more precisely by comparing with CAVI 0 , and to confirm the true meaning of CAVI as an index of arterial stiffness. First, the properties of PWV depending on the blood pressure and the variation of PWV values in the cardiac cycle were analyzed. Then, we attempted to clarify the point at which the PWV, adopted in CAVI or in CAVI 0 , was measured in cardiac cycle. A comprehensive comparison of the clinical data of CAVI and CAVI 0 showed that CAVI is more appropriate than CAVI 0. In conclusion, CAVI is reconfirmed to be a reliable and useful index of blood pressureindependent arterial stiffness composed of both organic and functional stiffness.

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