To measure the stiffness of the aorta, femoral artery and tibial artery noninvasively, cardio-ankle vascular index (CAVI) which is independent of blood pressure was developed. The formula for measuring this index is; CAVI=a{(2ρ/ΔP) × ln(Ps/Pd)PWV2} + b where, Ps and Pd are systolic and diastolic blood pressures respectively, PWV is pulse wave velocity between the heart and ankle, ΔP is Ps − Pd, ρ is blood density, and a and b are constants. This equation was derived from Bramwell-Hill’s equation1), and stiffness parameter2). To elucidate the clinical utility of CAVI, the reproducibility and dependence on blood pressure were studied using VaSera (Fukuda Denshi Co., Ltd.). Furthermore, CAVI in hemodialysis patients with or without atherosclerotic diseases was measured. The average coefficient of variation for five measurements among 22 persons was 3.8%. In hemodialysis patients (n = 482), CAVI was correlated weakly with systolic and diastolic blood pressures (R = 0.175, 0.006), while brachial-ankle PWV was correlated strongly with systolic and diastolic blood pressures (R = 0.463, 0.335). CAVI in hemodialysis patients without signs of atherosclerotic diseases (NA) was 8.1 ± 0.3 (mean ± SD). That in patients receiving percutaneous transluminal coronary angioplasty was 8.8 ± 0.3 (p < 0.05 vs. NA). CAVI in patients with ischemic change in their electrocardiogram (ECG) was 8.5 ± 0.3 (p < 0.05 vs. NA). That in patients with diabetes mellitus was 8.5 ± 0.3 (p < 0.002 vs. NA). CAVI in the patients with all three complications was 8.9 ± 0.35 (p < 0.001 vs. NA). These results suggested that CAVI could reflect arteriosclerosis of the aorta, femoral artery and tibial artery quantitatively.

The cardio-ankle vascular index (CAVI) is a new index of the overall stiffness of the artery from the origin of the aorta to the ankle. The most conspicuous feature of CAVI is its independence of blood pressure at the time of measurement. CAVI increases with age and in many arteriosclerotic diseases, such as coronary artery disease, carotid arteriosclerosis, chronic kidney disease and cerebrovascular disease, and is related to many coronary risk factors, such as hypertension, diabetes mellitus, dyslipidemia and smoking. Furthermore, CAVI decreases by controlling diabetes mellitus and hypertension, and also by abstaining from smoking. This suggests that CAVI is a physiological surrogate marker of athero- or arteriosclerosis, and also might be an indicator of lifestyle modification. Recently, it has been reported that CAVI and several left ventricular functions are co-related, suggesting a connection between the heart muscle and vascular function. This review covers the principles of CAVI and our current knowledge about CAVI, focusing on its roles and future outlook.

The cardio-ankle vascular stiffness index (CAVI) is a new parameter that reflects the stiffness of the aorta, femoral artery and tibial artery as a whole. One of its conspicuous features is that CAVI is independent of blood pressure at measuring time, theoretically. But, it has not been experimentally proved yet. For confirmation, pharmacological studies were performed comparing with brachial-ankle pulse wave velocity (baPWV). Used drugs were a β1-adrenoceptor blocker, metoprorol and an α1- adrenoceptor blocker doxazosin. Both were administered to 12 healthy volunteer men. CAVI and baPWV were measured every one hour for 6 hours using VaSera. When metoprolol (80 mg) was administered to 12 healthy volunteer men, systolic blood pressure decreased from 131.4 ± 4.5 to 118.3 ± 4.1 mmHg (mean ± SE) (p < 0.05) at the 3rd hour, and diastolic blood pressure decreased from 85.3 ± 4.0 to 75.3 ± 3.0 mm Hg (p < 0.05). baP-WV decreased from 13.93 ± 0.46 to 12.46 ± 0.49 m/sec (p < 0.05), significantly, but CAVI did not change (8.16 ± 0.29 to 8.24 ± 0.27) (p = 0.449). ΔbaPWV at each time was significantly correlated with both Δsystolic and Δdiastolic blood pressures, but ΔCAVI was not correlated with either Δblood pressure. When doxazosin (4 mg) was administered to the same men, systolic blood pressure decreased from 130.2 ± 4.6 to 117.2 ± 4.8 mmHg (p < 0.05) at the 3rd hour. Diastolic blood pressure also decreased from 85.1 ± 4.1 to 74.2 ± 3.9 mmHg (p < 0.05). baPWV decreased from 13.98 ± 0.68 to 12.25 ± 0.53 m/sec (p < 0.05), significantly. CAVI also decreased from 8.15 ± 0.28 to 7.18 ± 0.37 (p < 0.05), significantly. These results suggested that CAVI was not affected by blood pressure at the measuring time directly, but affected by the changes of contractility of smooth muscle cells.

A cardio-ankle vascular index (CAVI) has been developed to represent the extent of arteriosclerosis throughout the aorta, femoral artery and tibial artery independent of blood pressure. To practically use CAVI as a diagnostic tool for determining the extent of arteriosclerosis, our study objectives were (1) to establish the baseline CAVI scores by age and gender among cardiovascular disease (CVD) risk-free persons, (2) to compare CAVI scores between genders to test the hypothesis that the extent of arteriosclerosis in men is greater than in women, and (3) to compare CAVI scores between the CVD risk-free group and the CVD high-risk group in order to test the hypothesis that the extent of arteriosclerosis in the CVD high-risk group is greater than in the CVD risk-free group.

A body shape index (ABSI) is an abdominal obesity index developed based on epidemiological statistics and designed to correlate minimally with body mass index (BMI). We examined the approximation between ABSI and other abdominal obesity indices based on biophysical concepts. The cross-sectional data from 62,514 Japanese urban residents were analyzed. Body adiposity indices comprising BMI, waist circumference (WC), ABSI, conicity index (CI), waist-to-height ratio (WHtR), and WC/BMI ratio were examined. ABSI and CI more strongly correlated with age and arterial stiffness assessed by cardio-ankle vascular index (CAVI) compared to the other indices. The discriminative power for high CAVI (≥9.0) was the strongest for ABSI followed by CI and other indices, in that order. The range and distribution of WC corresponding to the cutoff of ABSI (0.0801), or CI (1.23) seemed reasonable. The correlation between ABSI and CI was the strongest compared to any other combination of indices. CI correlated moderately with BMI, whereas ABSI correlated minimally with BMI. ABSI correlates strongly and approximates closely with CI. Hence, ABSI may be considered to reflect the degree of body shape change from cylindricity to conicity and is currently the only abdominal obesity index not affected by the obesity paradox.