Abstract

BACKGROUND

A number of different techniques and methodologies have been applied to quantify stiffness of arteries. Because measures of arterial stiffness differ in regards to measurement locations as well as properties, it is not clear how well these measures that are supposed to reflect the same arterial wall properties are related.

METHODS

Interrelationships between different measures of arterial stiffness were evaluated in 50 apparently healthy subjects varying in age.

RESULTS

Significant relations ranging from mild to strong were observed among measures of arterial stiffness while some measures were not significantly associated. Cardio-ankle vascular index (CAVI) was significantly associated with carotid-femoral pulse wave velocity (cfPWV) and brachial-ankle pulse wave velocity (baPWV). Ultrasound-derived measures of arterial stiffness (e.g., compliance, distensibility) were weakly or not significantly related to pulse wave velocity (PWV) measures. The limits of agreement between each of arterial stiffness measures based on the Bland–Altman analyses indicate that there were close agreements (CI = 1.12–1.52) between CAVI, cfPWV, and baPWV. However, agreements between PWV measures and ultrasound-derived measures were mild to moderate. β-stiffness index demonstrated large 95% CIs with other measures. When associations between relative changes in various measures of arterial stiffness in response to isometric handgrip exercise were evaluated, the general trend of associations was similar to the relations observed at rest. β-stiffness index was not related to most measures of arterial stiffness.

CONCLUSION

These results suggest that the techniques used to assess arterial stiffness may not be interchangeable in clinical and research settings and that comparisons of findings obtained with different arterial stiffness measures should be conducted with caution.

Cardiovascular disease remains the number one cause of mortality in most industrialized countries. The majority of cardiovascular diseases are attributed to the disorders of the vasculature involving coronary arteries and cerebral arteries. Accordingly, the detection of early or subclinical vascular disease is critical for prevention of future cardiovascular events. Arterial stiffness has emerged as one of the most important measures for the evaluation of vascular dysfunction. 1

Due primarily to the technological improvements that enable reliable and reproducible measures, a number of different techniques and methodologies have been applied to quantify stiffness of arteries. 2 However, there is no consensus as to which arterial stiffness measure should be used. Although carotid-femoral pulse wave velocity (cfPWV) has been proposed as the reference standard measurement for arterial stiffness, 1 cfPWV is an indirect assessment of arterial stiffness that involves a number of assumptions and cannot be considered as a gold standard. Because of this, a variety of arterial stiffness measures have been proposed and used in the research settings. 2–4 Because measures of arterial stiffness differ in regards to measurement locations (central vs. peripheral, local vs. segmental) as well as properties (diameter changes vs. velocity changes), it is not clear how well these measures that are supposed to reflect the same arterial wall properties are related. Previous studies on this topic are limited to head-to-head comparisons of 2 techniques 3 , 5 or a small number of subjects. 6 , 7

With this information as background, the primary aim of the present study was to assess interrelationships between different measures of arterial stiffness. In addition to associations among basal (resting) measures of arterial stiffness, we evaluated how well relative changes in one measure of arterial stiffness were associated with other measures during isometric exercise, a test that is known to induce acute changes in arterial stiffness.

METHODS

Subjects

A total of 50 subjects varying in age (21–78 years in age range) were studied. The subjects were apparently healthy without any overt cardiovascular diseases or diabetes screened by medical history questionnaire. None of the subjects were taking cardiovascular-acting medications. Other exclusion criteria included pregnancy, chronic smoking, a recent illness or surgery, or any medical intervention within 12 hours before study visits. The Institutional Review Board at University of Texas at Austin approved the study, and written informed consent was obtained from all subjects.

Measurements

Subjects refrained from strenuous exercise for 12 hours, caffeine consumption for 6 hours, and food for 4 hours prior to the experimental trials.

Blood pressure.

Blood pressure (BP) was measured using the oscillometric device (Omron Healthcare, Kyoto, Japan) on the brachial artery.

Cardio-ankle vascular index.

Cardio-ankle vascular index (CAVI), unilateral brachial BP, ankle BP, and heart rate were measured simultaneously by the vascular testing device equipped with oscillometric pressure sensor cuffs, electrocardiograms, and phonocardiograms (VaSera VS-1000, Fukuda Denshi, Tokyo, Japan). 8 The equation to calculate CAVI was:

 
a[2ρ/ΔPressure]× ln(Systolic BP/Diastolic BP)PWV2] + b,

where a and b = scale conversion constants to match CAVI values with aortic PWV, ρ = blood density, and PWV = pulse wave velocity from aortic valve to ankle. Coefficients of variation of intraobserver and interobserver reliability were 3.4% and 2.4%. 9

Pulse wave velocity.

Both cfPWV and brachial-ankle pulse wave velocity (baPWV) were concurrently measured by the vascular testing device (VP-1000plus, Omron Healthcare) equipped with oscillometric pressure sensor cuffs, electrocardiograms, phonocardiograms, and arterial applanation tonometry sensors. 3 PWV was calculated from the pulse pressure wave travel distance divided by the time delay. Arterial applanation tonometry sensors incorporating an array of 12 micropiezoresistive transducers were placed on the carotid and femoral arteries to measure pulse pressure wave travel time, and travel distance was obtained by the measurement of body surface distance from the sites of transducers (straight distance between the carotid and femoral arteries) with a segmometer specifically constructed for PWV studies. 10 baPWV was acquired from the oscillometric pressure sensor cuffs placed on the unilateral arm and ankle. The coefficients of variation for 2 trials were 5% for cfPWV and 4% for baPWV.

Carotid artery compliance.

The simultaneous measurements of ultrasound imaging of the common carotid artery and arterial pressure waveforms from the contralateral carotid artery allows noninvasive determination of arterial compliance (day-to-day coefficient of variation was 5% ± 2%). 11 Common carotid artery diameter was measured from the images derived from an ultrasound machine equipped with a high-resolution linear array transducer (iE33 Ultrasound System, Philips Ultrasound, Bothell, WA). Carotid artery diameter was analyzed using image analysis software (Brachial Analyzer, Medical Imaging Applications, Coralville, IA), and carotid artery pressure waveforms were analyzed using a waveform analysis software (WinDq 2000, Dataq Instruments, Akron, OH). Because the baseline levels of carotid BP are subject to hold-down force, the pressure signal obtained by tonometry was calibrated by equating the carotid mean arterial and diastolic BP to the brachial artery value as previously described. 12 Arterial compliance, elastic modulus, arterial distensibility, β-stiffness index, and Young’s modulus were subsequently calculated using the following formulae.

 
Arterial compliance = ΔDiameter/ΔPressure
 
Arterial distensibility = ΔDiameter/ (ΔPressure × Diameter at end-diastole)
 
Elastic modulus = (ΔPressure ×Diameter at end-diastole)/ΔDiameter
 
Young’s modulus = (ΔPressure×Diameter at end-diastole)/ΔDiameter×IMT
 
β-stiffness index= ln(ΔPressure)/(ΔDiameter/Diameter at end-diastole),

where IMT = intima-media thickness.

Isometric handgrip exercise.

Subjects performed isometric handgrip exercise (HDM-915; Lode Instruments, Groningen, The Netherlands) conducted at 40% of maximal voluntary contraction for 2 minutes. The force generated by the subjects was monitored closely on a visual display during the test. Subjects were instructed to breathe normally, avoid Valsalva maneuvers, and contract only the flexors of the hand to minimize muscular recruitment of the upper arm and shoulder. During 2 minutes of isometric handgrip exercise, BP was measured after 1 minute of BP perturbation, and all arterial stiffness measurements was simultaneously obtained followed by the BP measurement.

Statistical analyses

All variable distributions were examined using the Shapiro–Wilk test of normality recommended for small samples. A log transformation was used to normalize the distribution of skewed variables. Univariate correlational analyses were performed to determine the interrelationship among different measures of arterial stiffness at rest. The Bland–Altman plots were used to assess the limits of agreement with raw scores converted to Z -scores prior to analyses. Because the Z -score adjusts individual results based on SDs, it would allow arterial stiffness measures expressed in different units and data spreads to be compared on the same standardized scale. The Bland regression method was then used to determine 95% confidence interval (CI) limits at the mean. In order to account for the influence of heart rate and blood pressure, partial correlational analyses were conducted to assess interrelations between changes in arterial stiffness during isometric exercise. All data were presented as means ± SEM. Statistical significance was set a priori at P <0.05. SPSS statistics software version 22 (IBM, Chicago, IL) was used for all statistical analyses.

RESULTS

Table 1 shows selected descriptive subject characteristics. Interrelationships among different measure of arterial stiffness indices at baseline are displayed in Table 2 . Significant relations ranging widely from mild to strong were observed among measures of arterial stiffness while some measures were not significantly associated. All the measures of arterial stiffness derived from PWV (CAVI, cfPWV, and baPWV) were significantly associated with each other. β-stiffness index and Young’s elastic modulus were not associated with PWV measures of arterial stiffness. The limits of agreement between each of arterial stiffness measures based on the Bland–Altman analyses are presented in Table 3 . These prediction intervals expressed as 95% CIs demonstrate a large variation. There were close agreements (CI = 1.12–1.52) between CAVI, cfPWV, and baPWV. Agreements between PWV measures and ultrasound-derived measures were mild to moderate. β-stiffness index demonstrated large 95% CIs with other measures. In addition to basal (resting) levels of arterial stiffness, associations between relative changes in various measures of arterial stiffness in response to isometric handgrip exercise were also evaluated ( Table 4 ). Compared with the relations observed at rest, a greater number of intercorrelations were not statistically significant.

Table 1.

Selected subject characteristics

  Total ( N = 50)  
Age (years) 45.4±2.7 
Male/female ( n )  29/21 
Height (cm) 172±1 
Body mass (kg) 75.9±2.3 
Body mass index (kg/m 2 )  25.6±0.7 
Heart rate at rest (bpm) 57±1 
Systolic blood pressure (mm Hg) 124±2 
Diastolic blood pressure (mm Hg) 75±1 
Mean blood pressure (mm Hg) 91±1 
Pulse pressure (mm Hg) 49±1 
Carotid artery diameter (mm) 3.6±01 
Carotid artery IMT (mm) 0.52±0.02 
CAVI (AU) 7.3±0.2 
cfPWV (cm/s) 927±27 
baPWV (cm/s) 1,202±30 
Arterial compliance (cm/mm Hg) 0.01±0.001 
Elastic modulus (mm Hg) 395±21 
Distensibility (1/mm Hg) 0.04±0.002 
β-stiffness index (AU) 0.29±0.06 
Young’s modulus (mm) 821±46 
Maximal handgrip strength ( N )  244±15 
  Total ( N = 50)  
Age (years) 45.4±2.7 
Male/female ( n )  29/21 
Height (cm) 172±1 
Body mass (kg) 75.9±2.3 
Body mass index (kg/m 2 )  25.6±0.7 
Heart rate at rest (bpm) 57±1 
Systolic blood pressure (mm Hg) 124±2 
Diastolic blood pressure (mm Hg) 75±1 
Mean blood pressure (mm Hg) 91±1 
Pulse pressure (mm Hg) 49±1 
Carotid artery diameter (mm) 3.6±01 
Carotid artery IMT (mm) 0.52±0.02 
CAVI (AU) 7.3±0.2 
cfPWV (cm/s) 927±27 
baPWV (cm/s) 1,202±30 
Arterial compliance (cm/mm Hg) 0.01±0.001 
Elastic modulus (mm Hg) 395±21 
Distensibility (1/mm Hg) 0.04±0.002 
β-stiffness index (AU) 0.29±0.06 
Young’s modulus (mm) 821±46 
Maximal handgrip strength ( N )  244±15 

Data are means ± SEM. Abbreviations: AU, arbitrary unit; baPWV, brachial-ankle pulse wave velocity; CAVI, cardio-ankle vascular index; cfPWV, carotid-femoral pulse wave velocity; IMT, intima-media thickness.

Table 2.

Interrelationships among different measure of arterial stiffness indices at baseline

 cfPWV baPWV Compli. ElaMod Distens. β-stiff. Young 
CAVI 0.74 0.82 −0.38 0.45 −0.29 NS NS 
cfPWV – 0.69 −0.39 0.47 −0.31 NS NS 
baPWV  – −0.44 0.54 −0.32 NS NS 
Compli.   – −0.96 0.96 −0.91 0.82 
ElaMod    – −0.86 0.79 0.76 
Distens.     – −0.96 0.83 
β-stiff.      – 0.81 
 cfPWV baPWV Compli. ElaMod Distens. β-stiff. Young 
CAVI 0.74 0.82 −0.38 0.45 −0.29 NS NS 
cfPWV – 0.69 −0.39 0.47 −0.31 NS NS 
baPWV  – −0.44 0.54 −0.32 NS NS 
Compli.   – −0.96 0.96 −0.91 0.82 
ElaMod    – −0.86 0.79 0.76 
Distens.     – −0.96 0.83 
β-stiff.      – 0.81 

Data are Pearson correlation coefficients. Abbreviations: baPWV, brachial-ankle pulse wave velocity; CAVI, cardio-ankle vascular index; cfPWV, carotid-femoral pulse wave velocity; Compli., arterial compliance; Distens., arterial distensibility; ElaMod, elastic modulus; NS, nonsignificant; Young, Young’s modulus; β-stiff., β-stiffness index.

Table 3.

95% confidence intervals derived from differences in Z -scores between different measures of arterial stiffness at baseline

 cfPWV baPWV Compli. ElaMod Distens. β-stiff. Young 
CAVI 1.52 1.12 3.26 2.08 3.14 2.68 
cfPWV – 1.66 3.28 2.16 3.16 2.96 2.62 
baPWV  – 3.36 1.86 3.22 2.58 
Compli.   – 3.82 0.54 2.92 3.68 
ElaMod    – 3.72 2.74 1.44 
Distens.     – 2.90 3.68 
β-stiff.      – 2.90 
 cfPWV baPWV Compli. ElaMod Distens. β-stiff. Young 
CAVI 1.52 1.12 3.26 2.08 3.14 2.68 
cfPWV – 1.66 3.28 2.16 3.16 2.96 2.62 
baPWV  – 3.36 1.86 3.22 2.58 
Compli.   – 3.82 0.54 2.92 3.68 
ElaMod    – 3.72 2.74 1.44 
Distens.     – 2.90 3.68 
β-stiff.      – 2.90 

Abbreviations: baPWV, brachial-ankle pulse wave velocity; CAVI, cardio-ankle vascular index; cfPWV, carotid-femoral pulse wave velocity; Compli., arterial compliance; Distens., arterial distensibility; ElaMod, elastic modulus; Young, Young’s modulus; β-stiff., β-stiffness index.

Table 4.

Interrelationships among different measure of arterial stiffness indices on percent (%) change during isometric handgrip exercise

 cfPWV baPWV Compli. ElaMod Distens. β-stiff. Young 
CAVI NS 0.41 −0.39 NS −0.36 NS NS 
cfPWV – 0.48 NS NS NS NS NS 
baPWV  – NS NS NS NS NS 
Compli.   – 0.88 0.86 −0.33 0.73 
ElaMod    – 0.52 NS 0.74 
Distens.     – NS 0.53 
β-stiff.      – NS 
 cfPWV baPWV Compli. ElaMod Distens. β-stiff. Young 
CAVI NS 0.41 −0.39 NS −0.36 NS NS 
cfPWV – 0.48 NS NS NS NS NS 
baPWV  – NS NS NS NS NS 
Compli.   – 0.88 0.86 −0.33 0.73 
ElaMod    – 0.52 NS 0.74 
Distens.     – NS 0.53 
β-stiff.      – NS 

Data are partial correlation coefficients controlled for heart rate and mean arterial pressure. Abbreviations: baPWV, brachial-ankle pulse wave velocity; CAVI, cardio-ankle vascular index; cfPWV, carotid-femoral pulse wave velocity; Compli., arterial compliance; Distens., arterial distensibility; ElaMod, elastic modulus; NS, nonsignificant; Young, Young’s modulus; β-stiff., β-stiffness index.

DISCUSSION

In the present investigation, we used 3 different but related approaches to conduct comparisons between different measures of arterial stiffness. First, simple univariate correlational analyses were used to evaluate associations between basal measures of arterial stiffness. Second, a combination of Bland–Altman plots with calculations of 95% CIs were utilized to evaluate the limits of agreements between arterial stiffness measures. Third, isometric handgrip exercise was used to induce acute increases in arterial stiffness to see how well relative changes in one arterial stiffness measure would be tracked by another. The consistent finding across all 3 approaches was that measures of arterial stiffness were very variably associated with each other ranging from no significant associations to highly significant associations ( r = 0.96). These results suggest that the techniques used to assess arterial stiffness may not be interchangeable in clinical and research settings and that comparisons of research findings obtained with different arterial stiffness measures should be carefully conducted with caution.

Most of the arterial stiffness indices demonstrated significant associations with each other in the present study. However, there were notable differences in the strengths of correlations due primarily to different properties of arterial stiffness measurements. Arterial stiffness indices that share a homogeneous methodology seem to have greater correlations. For example, good agreements ranging 0.69–0.82 were observed between regional or propagative measures of arterial stiffness derived from PWV (cfPWV, baPWV, and CAVI). These results are consistent with previous larger-scale studies evaluating head-to-head comparisons of 2 techniques. 3 , 13 Between some measures of arterial stiffness, however, there were no significant associations. These results may be surprising given the fact that all the techniques examined in the present study are supposed to measure the same property of arterial wall. However, these results are consistent with previous studies using smaller number of subjects 6 , 7 and with a limited number of techniques. 3 , 5 Even within the techniques to measure cfPWV, there is a substantial difference in cfPWV values measured with SphygmoCor and Complior due primarily to different algorithms used to detect the “foot” of the pressure pulse. 5 A similarly poor or mild correspondence has been reported between measures of other vascular functions, including augmentation index, an index of arterial wave reflection and arterial stiffness 14 and vascular reactivity. 15

β-stiffness index has been proposed as a measure of arterial stiffness that is independent of BP. Interestingly, β-stiffness index was not significantly associated with many of the techniques examined in the present study. The proponents of β-stiffness index may argue that a lack of association would support and reinforce the BP independent concept of β-stiffness index that cannot be observed with other techniques. But such concept has been challenged by some as significant associations have been reported between β-stiffness index and BP. 4 , 9 Interestingly, CAVI has also been introduced as a BP independent measure of arterial stiffness as CAVI has been derived from the concept of β-stiffness index. 8 Several studies in Japan have verified the BP independence of CAVI 8 , 16 and have reported a strong association between CAVI and the stiffness parameter β obtained with transesophageal echocardiography. 17 However, CAVI was not associated with β-stiffness index in the present study. The reasons for the discrepancy are not clear. But CAVI differs from β-stiffness index in a number of ways. For example, β-stiffness index is a measure of local arterial stiffness determined from pulsatile changes in arterial diameter and BP whereas CAVI is a measure of segmental arterial stiffness that is derived from PWV. In the present study, the strengths of correlations were considerably lower between segmental and local stiffness measures (nonsignificant to 0.54) than in more homogeneous measures (ranging from 0.69 to 0.82 in segmental measures). Additionally, arteries undergo remodeling in response to chronic stimuli, 18 , 19 this might exert differential effects on compliance-based measures compared with wall stiffness-based measures.

The present study cannot determine which of the methods to obtain arterial stiffness is superior or correct. cfPWV cannot be a gold standard for the assessment of arterial stiffness as it is an indirect estimate of arterial stiffness. But because of the accumulated research evidence indicating its cardiovascular prognosis, 20 , 21 it has emerged as a reference standard or a hallowed technique. cfPWV was significantly associated with other propagative measures of arterial stiffness, including baPWV and CAVI, but the associations of cfPWV with ultrasound-derived measures of arterial compliance were very mild. Interestingly, all measures of ultrasound-based arterial stiffness were derived from the measurements of arterial diameter and local pressure through a variety of mathematical equations but the associations among them were not strong suggesting that each measure may attempt to reflect unique aspects of arterial stiffness.

In conclusion, the results of the present study indicate that the associations between measures of arterial stiffness are very variable ranging from no association to highly significant correlation. The strengths of these interrelations appear to remain irrespective of what assessment methods were used since simple correlations, the Bland–Altman plots and acute pressor responses all indicate consistent findings. These results suggest that a caution should be used when findings obtained using one measure of arterial stiffness were compared with those obtained using a different method.

SUPPLEMENTARY MATERIAL

Supplementary material is available at American Journal of Hypertension ( http://ajh.oxfordjournals.org ).

DISCLOSURE

The authors declared no conflict of interest.

ACKNOWLEDGMENTS

This work was supported by a grant by Fukuda Denshi, Tokyo, Japan.

REFERENCES

1.
Townsend
RR
Wilkinson
IB
Schiffrin
EL
Avolio
AP
Chirinos
JA
Cockcroft
JR
Heffernan
KS
Lakatta
EG
McEniery
CM
Mitchell
GF
Najjar
SS
Nichols
WW
Urbina
EM
Weber
T
;
American Heart Association Council on Hypertension
.
Recommendations for improving and standardizing vascular research on arterial stiffness: a scientific statement from the American Heart Association
.
Hypertension
 
2015
;
66
:
698
722
.
2.
O’Rourke
MF
Staessen
JA
Vlachopoulos
C
Duprez
D
Plante
GE
.
Clinical applications of arterial stiffness; definitions and reference values
.
Am J Hypertens
 
2002
;
15
:
426
444
.
3.
Tanaka
H
Munakata
M
Kawano
Y
Ohishi
M
Shoji
T
Sugawara
J
Tomiyama
H
Yamashina
A
Yasuda
H
Sawayama
T
Ozawa
T
.
Comparison between carotid-femoral and brachial-ankle pulse wave velocity as measures of arterial stiffness
.
J Hypertens
 
2009
;
27
:
2022
2027
.
4.
Lehmann
ED
.
Terminology for the definition of arterial elastic properties
.
Pathol Biol (Paris)
 
1999
;
47
:
656
664
.
5.
Millasseau
SC
Stewart
AD
Patel
SJ
Redwood
SR
Chowienczyk
PJ
.
Evaluation of carotid-femoral pulse wave velocity: influence of timing algorithm and heart rate
.
Hypertension
 
2005
;
45
:
222
226
.
6.
Woodman
RJ
Kingwell
BA
Beilin
LJ
Hamilton
SE
Dart
AM
Watts
GF
.
Assessment of central and peripheral arterial stiffness: studies indicating the need to use a combination of techniques
.
Am J Hypertens
 
2005
;
18
:
249
260
.
7.
Huck
CJ
Bronas
UG
Williamson
EB
Draheim
CC
Duprez
DA
Dengel
DR
.
Noninvasive measurements of arterial stiffness: repeatability and interrelationships with endothelial function and arterial morphology measures
.
Vasc Health Risk Manag
 
2007
;
3
:
343
349
.
8.
Shirai
K
Hiruta
N
Song
M
Kurosu
T
Suzuki
J
Tomaru
T
Miyashita
Y
Saiki
A
Takahashi
M
Suzuki
K
Takata
M
.
Cardio-ankle vascular index (CAVI) as a novel indicator of arterial stiffness: theory, evidence and perspectives
.
J Atheroscler Thromb
 
2011
;
18
:
924
938
.
9.
Lim
J
Pearman
ME
Park
W
Alkatan
M
Machin
DR
Tanaka
H
.
Impact of blood pressure perturbations on arterial stiffness
.
Am J Physiol Regul Integr Comp Physiol
 
2015
;
309
:
R1540
R1545
.
10.
Sugawara
J
Hayashi
K
Yokoi
T
Tanaka
H
.
Carotid-femoral pulse wave velocity: impact of different arterial path length measurements
.
Artery Res
 
2010
;
4
:
27
31
.
11.
Cook
JN
DeVan
AE
Schleifer
JL
Anton
MM
Cortez-Cooper
MY
Tanaka
H
.
Arterial compliance of rowers: implications for combined aerobic and strength training on arterial elasticity
.
Am J Physiol Heart Circ Physiol
 
2006
;
290
:
H1596
H1600
.
12.
Agabiti-Rosei
E
Mancia
G
O’Rourke
MF
Roman
MJ
Safar
ME
Smulyan
H
Wang
JG
Wilkinson
IB
Williams
B
Vlachopoulos
C
.
Central blood pressure measurements and antihypertensive therapy: a consensus document
.
Hypertension
 
2007
;
50
:
154
160
.
13.
Sugawara
J
Hayashi
K
Yokoi
T
Cortez-Cooper
MY
DeVan
AE
Anton
MA
Tanaka
H
.
Brachial-ankle pulse wave velocity: an index of central arterial stiffness?
J Hum Hypertens
 
2005
;
19
:
401
406
.
14.
Sugawara
J
Komine
H
Hayashi
K
Yoshizawa
M
Yokoi
T
Maeda
S
Tanaka
H
.
Agreement between carotid and radial augmentation index: does medication status affect the relation?
Artery Res
 
2008
;
2
:
74
-
76
.
15.
Dhindsa
M
Sommerlad
SM
DeVan
AE
Barnes
JN
Sugawara
J
Ley
O
Tanaka
H
.
Interrelationships among noninvasive measures of postischemic macro- and microvascular reactivity
.
J Appl Physiol (1985)
 
2008
;
105
:
427
432
.
16.
Ibata
J
Sasaki
H
Kakimoto
T
Matsuno
S
Nakatani
M
Kobayashi
M
Tatsumi
K
Nakano
Y
Wakasaki
H
Furuta
H
Nishi
M
Nanjo
K
.
Cardio-ankle vascular index measures arterial wall stiffness independent of blood pressure
.
Diabetes Res Clin Pract
 
2008
;
80
:
265
270
.
17.
Takaki
A
Ogawa
H
Wakeyama
T
Iwami
T
Kimura
M
Hadano
Y
Matsuda
S
Miyazaki
Y
Matsuda
T
Hiratsuka
A
Matsuzaki
M
.
Cardio-ankle vascular index is a new noninvasive parameter of arterial stiffness
.
Circ J
 
2007
;
71
:
1710
1714
.
18.
Miyachi
M
Tanaka
H
Yamamoto
K
Yoshioka
A
Takahashi
K
Onodera
S
.
Effects of one-legged endurance training on femoral arterial and venous size in healthy humans
.
J Appl Physiol (1985)
 
2001
;
90
:
2439
2444
.
19.
Dinenno
FA
Tanaka
H
Monahan
KD
Clevenger
CM
Eskurza
I
DeSouza
CA
Seals
DR
.
Regular endurance exercise induces expansive arterial remodelling in the trained limbs of healthy men
.
J Physiol
 
2001
;
534
:
287
295
.
20.
Blacher
J
Asmar
R
Djane
S
London
GM
Safar
ME
.
Aortic pulse wave velocity as a marker of cardiovascular risk in hypertensive patients
.
Hypertension
 
1999
;
33
:
1111
1117
.
21.
Meyer
ML
Tanaka
H
Palta
P
Cheng
S
Gouskova
N
Aguilar
D
Heiss
G
.
Correlates of segmental pulse wave velocity in older adults: the Atherosclerosis Risk in Communities (ARIC) Study
.
Am J Hypertens
 
2016
;
29
:
114
122
.