THE EFFECT OF BLOOD PRESSURE ALTERATION ON THE PULSE WAVE VELOCITY

The role of retinal vessel geometry as an indicator of systemic arterial stiffness assessed by cardio-ankle vascular index

Objective

To determine whether retinal vessel geometry is associated with systemic arterial stiffness, as determined by the cardio-ankle vascular index (CAVI).

Methods

This single-center retrospective cross-sectional study included 407 eyes of 407 subjects who underwent routine health exams, including CAVI and fundus photography. Retinal vessel geometry was measured using a computer-assisted program (Singapore "I" Vessel Assessment). Subjects were classified into two groups based on CAVI values: high CAVI (≥9) or low CAVI (<9). The main outcome measures included the association of retinal vessel geometry and CAVI value evaluated using multivariable logistic regression models.

Results

Three hundred forty-three subjects (343, 84.3%) were in the low CAVI group, and 64 (15.7%) subjects were in the high CAVI group. Multivariable logistic linear regression analyses adjusted for age, sex, body mass index, smoking status, mean arterial pressure, and the presence of hypertension, diabetes mellitus, and dyslipidemia showed a significant association between high CAVI values and the following retinal vessel geometry parameters: central retinal arteriolar equivalent caliber (CRAE; adjusted odds ratio [AOR], 0.95; 95% confidence interval [CI], 0.89-1.00; P = 0.043), fractal dimension of arteriolar network (FDa; AOR, 4.21 × 10^-4; 95% CI, 2.32 × 10^-7-0.77; P = 0.042), and arteriolar branching angle (BAa; AOR, 0.96; 95% CI, 0.93-0.99; P = 0.007).

Conclusions

Increased systemic arterial stiffness had a significant association with retinal vessel geometry related to arterial narrowing (CRAE), less branching complexity of the arterial tree (FDa), and acute arteriolar bifurcation (BAa).

Calibration-Free Cuffless Blood Pressure Estimation Based on a Population With a Diverse Range of Age and Blood Pressure

This study presents a new blood pressure (BP) estimation algorithm utilizing machine learning (ML). A cuffless device that can measure BP without calibration would be precious for portability, continuous measurement, and comfortability, but unfortunately, it does not currently exist. Conventional BP measurement with a cuff is standard, but this method has various problems like inaccurate BP measurement, poor portability, and painful cuff pressure. To overcome these disadvantages, many researchers have developed cuffless BP estimation devices. However, these devices are not clinically applicable because they require advanced preparation before use, such as calibration, do not follow international standards (81060-1:2007), or have been designed using insufficient data sets. The present study was conducted to combat these issues. We recruited 127 participants and obtained 878 raw datasets. According to international standards, our diverse data set included participants from different age groups with a wide variety of blood pressures. We utilized ML to formulate a BP estimation method that did not require calibration. The present study also conformed to the method required by international standards while calculating the level of error in BP estimation. Two essential methods were applied in this study: (a) grouping the participants into five subsets based on the relationship between the pulse transit time and systolic BP by a support vector machine ensemble with bagging (b) applying the information from the wavelet transformation of the pulse wave and the electrocardiogram to the linear regression BP estimation model for each group. For systolic BP, the standard deviation of error for the proposed BP estimation results with cross-validation was 7.74 mmHg, which was an improvement from 17.05 mmHg, as estimated by the conventional pulse-transit-time-based methods. For diastolic BP, the standard deviation of error was 6.42 mmHg for the proposed BP estimation, which was an improvement from 14.05mmHg. The purpose of the present study was to demonstrate and evaluate the performance of the newly developed BP estimation ML method that meets the international standard for non-invasive sphygmomanometers in a population with a diverse range of age and BP.

Predictive Value of the Cardio-Ankle Vascular Index for Cardiovascular Events in Patients at Cardiovascular Risk

Background Arterial stiffness is an important predictor of cardiovascular events; however, indexes for measuring arterial stiffness have not been widely incorporated into routine clinical practice. This study aimed to determine whether the cardio-ankle vascular index (CAVI), based on the blood pressure-independent stiffness parameter β and reflecting arterial stiffness from the origin of the ascending aorta, is a good predictor of cardiovascular events in patients with cardiovascular disease risk factors in a large prospective cohort. Methods and Results This multicenter prospective cohort study, commencing in May 2013, with a 5-year follow-up period, included patients (aged 40‒74 years) with cardiovascular disease risks. The primary outcome was the composite of cardiovascular death, nonfatal stroke, or nonfatal myocardial infarction. Among 2932 included patients, 2001 (68.3%) were men; the mean (SD) age at diagnosis was 63 (8) years. During the median follow-up of 4.9 years, 82 participants experienced primary outcomes. The CAVI predicted the primary outcome (hazard ratio, 1.38; 95% CI, 1.16‒1.65; P<0.001). In terms of event subtypes, the CAVI was associated with cardiovascular death and stroke but not with myocardial infarction. When the CAVI was incorporated into a model with known cardiovascular disease risks for predicting cardiovascular events, the global χ² value increased from 33.8 to 45.2 (P<0.001), and the net reclassification index was 0.254 (P=0.024). Conclusions This large cohort study demonstrated that the CAVI predicted cardiovascular events. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01859897.

Cardio-ankle vascular index is associated with coronary plaque composition assessed with iMAP-intravascular ultrasound in patients with coronary artery disease

BACKGROUND

The cardio-ankle vascular index (CAVI) is an indicator of arterial stiffness and has been reported to be associated with the severity of coronary artery disease and cardiovascular events. However, whether CAVI can predict the composition of coronary plaques remains unclear.

METHODS

We enrolled 208 patients who underwent percutaneous coronary intervention (PCI) for culprit lesions evaluated with iMAP-intravascular ultrasound (IVUS), a radiofrequency imaging system for characterizing tissues. iMAP-IVUS classified the culprit plaque composition as fibrotic, lipidic, necrotic, or calcified, and the respective absolute volumes [fibrotic volume (FV), lipidic volume (LV), necrotic volume NV, and calcified volume] and their ratios (%) within the total plaque volume were calculated. A plaque with a median %NV of ≥ 33.2% was defined as a larger NV (LNV) plaque. We measured CAVI and divided the patients into two groups according to CAVI ≥8 (high CAVI, n = 164) or <8 (low CAVI, n = 44).

RESULTS

Culprit plaques had significantly greater absolute NV (p = 0.016), %NV (p = 0.01), and smaller %FV (p = 0.02) in patients with high CAVI than in those with low CAVI. Patients with high CAVI had a higher prevalence of LNV plaques in culprit lesions than those with low CAVI (54% vs. 34%, p = 0.026). CAVI correlated significantly and positively with absolute NV, LV, and negatively with %FV. In logistic regression analysis after adjustment for the classic coronary risk factors and possible variables associated with vulnerable plaques, high CAVI had an independent and significant association with the presence of LNV plaques (OR, 3.37; 95% CI, 1.45-7.79; p = 0.0032).

CONCLUSIONS

A high CAVI is associated with the composition of coronary culprit plaques, particularly increased amount of necrotic tissue, in patients with coronary artery disease undergoing PCI .

The impact of heart rate on pulse wave velocity: an in-silico evaluation

BACKGROUND

Clinical and experimental evidence regarding the influence of heart rate (HR) on arterial stiffness and its surrogate marker carotid-to-femoral pulse wave velocity (cf-PWV) is conflicting. We aimed to evaluate the effect of HR on cf-PWV measurement under controlled haemodynamic conditions and especially with respect to blood pressure (BP) that is a strong determinant of arterial stiffness.

METHOD

Fifty-nine simulated cases were created using a previously validated in-silico model. For each case, cf-PWV was measured at five HR values, 60, 70, 80, 90, 100 bpm. With increasing HR, we assessed cf-PWV under two scenarios: with BP free to vary in response to HR increase, and with aortic DBP (aoDBP) fixed to its baseline value at 60 bpm, by modifying total peripheral resistance accordingly. Further, we quantified the importance of arterial compliance (C) on cf-PWV changes caused by increasing HR.

RESULTS

When BP was left free to vary with HR, a significant HR-effect on cf-PWV (0.66 ± 0.24 m/s per 10 bpm, P < 0.001) was observed. This effect was reduced to 0.21 ± 0.14 m/s per 10 bpm (P = 0.048) when aoDBP was maintained fixed with increasing HR. The HR-effect on the BP-corrected cf-PWV was higher in the case of low C = 0.8 ± 0.3 ml/mmHg (0.26 ± 0.15 m/s per 10 bpm, P = 0.014) than the case of higher C = 1.7 ± 0.5 ml/mmHg (0.16 ± 0.07 m/s per 10 bpm, P = 0.045).

CONCLUSION

Our findings demonstrated that relatively small HR changes may only slightly affect the cf-PWV. Nevertheless, in cases wherein HR might vary at a greater extent, a more clinically significant impact on cf-PWV should be considered.

Arterial Stiffness Assessed by Cardio-Ankle Vascular Index in Patients With Abdominal Aortic Aneurysm and Its Alterations After Treatment

PURPOSE

The aim of the present study was to investigate a potential difference on the arterial stiffness among aneurysm patients and non-aneurysm controls, as well as to explore potential changes between patients treated either with endovascular or open repair.

MATERIALS AND METHODS

A 110 patients with an infrarenal AAA were prospectively enrolled in this study. Fifty-six patients received an EVAR, whereas 54 patients received an open surgical repair. Moreover, 103 gender and age-matched subjects without AAA served as controls. The cardio-ankle vascular index (CAVI) was applied for measurement of the arterial stiffness.

RESULTS

CAVI values were statistically higher in the AAA patients when compared with control subjects. Although at 48 hours postoperatively the CAVI values were increased in both groups when compared to baseline values, the difference in CAVI had a tendency to be higher in the open group compared to the endovascular group. At 6 months of follow up the CAVI values returned to the baseline for the patients of the open repair group. However, in the endovascular group CAVI values remained higher when compared with the baseline values.

CONCLUSION

Patients with AAAs demonstrated a higher value of CAVI compared to healthy controls. A significant increase of arterial stiffness in both groups during the immediate postoperative period was documented. The increase in arterial stiffness remained significant at 6 months in EVAR patients. Further studies are needed to elucidate the impact of a decreased aortic compliance after stentgraft implantation on the cardiac function of patients with AAA.

Sources of Inaccuracy in Photoplethysmography for Continuous Cardiovascular Monitoring

Photoplethysmography (PPG) is a low-cost, noninvasive optical technique that uses change in light transmission with changes in blood volume within tissue to provide information for cardiovascular health and fitness. As remote health and wearable medical devices become more prevalent, PPG devices are being developed as part of wearable systems to monitor parameters such as heart rate (HR) that do not require complex analysis of the PPG waveform. However, complex analyses of the PPG waveform yield valuable clinical information, such as: blood pressure, respiratory information, sympathetic nervous system activity, and heart rate variability. Systems aiming to derive such complex parameters do not always account for realistic sources of noise, as testing is performed within controlled parameter spaces. A wearable monitoring tool to be used beyond fitness and heart rate must account for noise sources originating from individual patient variations (e.g., skin tone, obesity, age, and gender), physiology (e.g., respiration, venous pulsation, body site of measurement, and body temperature), and external perturbations of the device itself (e.g., motion artifact, ambient light, and applied pressure to the skin). Here, we present a comprehensive review of the literature that aims to summarize these noise sources for future PPG device development for use in health monitoring.

Effects of Enhanced Intracranial Pressure on Blood Pressure and the Cardio-Ankle Vascular Index in Rabbits

Aim: Stroke is well known to lead to hypertension; nevertheless, the role of vascular function in hypertension remains unclear. In this study, we aimed to clarify the mechanism underlying increased arterial stiffness following stroke.

Methods: The cardio-ankle vascular index (CAVI) was measured in five New Zealand White rabbits. Under general anesthesia, intracranial pressure (ICP) was increased by injecting saline (15 mL) into the cisterna magna. ICP was monitored using a catheter inserted into the subarachnoid space via right frontal bone craniotomy. Blood pressure (BP), CAVI, and common carotid flow (CCF) were evaluated, and the responses of these parameters to increased ICP were analyzed.

Results: Saline injection into the cisterna magna increased the ICP by over 20 mmHg. Both BP and CAVI increased from 63.2±4.84 to 128.8±14.68 mmHg and from 4.02±0.28 to 4.9±0.53, respectively. Similarly, BP and CCF increased. When hexamethonium was administered before the increase in ICP, the increase in BP (132.2±9.41 mmHg with 10 mg/kg hexamethonium vs. 105.6±11.01 mmHg with 100 mg/kg hexamethonium) and CAVI (5.02±0.64 with 10 mg/kg hexamethonium vs. 4.82±0.42 with 100 mg/kg hexamethonium) were suppressed in a dose-dependent manner.

Conclusion: Increased ICP causes an increase in BP and CAVI, suggesting that enhanced stiffness of the muscular arteries contributes to high BP. Blocking the autonomic nervous system with hexamethonium suppresses the increase in BP and CAVI, indicating that these increases are mediated by activation of the autonomic nervous system.

Heart rate and blood pressure dependence of aortic distensibility in rats: comparison of measured and calculated pulse wave velocity

OBJECTIVES

When assessing arterial stiffness, heart rate (HR) and blood pressure (BP) are potential confounders. It appears that the HR/BP dependences of pulse wave velocity (PWV) and distensibility are different, even though both assess arterial stiffness. This study aims to compare aortic PWV as measured using pulse transit time (PWVTT) and as calculated from distensibility (PWVdist) at the same measurement site and propose a solution to the disparity in dependences of PWVTT and PWVdist.

METHODS

Adult anaesthetized rats (n = 24) were randomly paced at HRs 300-500 bpm, at 50 bpm steps. At each step, aortic PWVTT (two pressure-tip catheters) and PWVdist (pressure-tip catheter and ultrasound wall-tracking; abdominal aorta) were measured simultaneously while BP was varied pharmacologically.

RESULTS

HR dependence of PWVdist paradoxically decreased at higher levels of BP. In addition, BP dependence of PWVdist was much larger than that of PWVTT. These discrepancies are explained in that standard PWVdist uses an approximate derivative of pressure to diameter, which overestimates PWV with increasing pulse pressure (PP). In vivo, PP decreases as HR increases, potentially causing a PWVdist decrease with HR. Estimating the full pressure-diameter curve for each HR corrected for this effect by enabling calculation of the true derivative at diastolic BP. This correction yielded a PWVdist that shows HR and BP dependences similar to those of PWVTT. As expected, BP dependence of all PWV metrics was much larger than HR dependence.

CONCLUSION

Measured and calculated PWV have different dependences on HR and BP. These differences are, at least in part, because of approximations made in using systolic and diastolic values to calculate distensibility.

Comparing the Heart-Thigh and Thigh-Ankle Arteries with the Heart-Ankle Arterial Segment for Arterial Stiffness Measurements

Purpose

The cardio-ankle vascular index, applying the stiffness parameter β theory, was calculated using the pulse-wave velocity and blood pressure from the aortic orifice to the ankle. Accordingly, the impact of the stiffness of the aorta [heart–thigh β (htBETA)] and medium-sized muscular artery [thigh–ankle β (taBETA)] on the stiffness of the heart–ankle β (haBETA) was investigated; further, whether the htBETA (haBETA − taBETA) improved the power of diagnosis of coronary artery disease (CAD) was examined.

Materials and Methods

Segmental βs were calculated using VaSela with an additional thigh cuff and compared using the receiver operating characteristic (ROC) curve analysis to evaluate CAD.

Results

Overall, 90 healthy subjects and 41 patients with CAD were included. In both groups, haBETA and htBETA, but not taBETA, correlated with age, and taBETA was three times higher than htBETA (p < 0.01). Multiple regression analysis revealed that haBETA can be estimated using htBETA and taBETA in healthy subjects and patients with CAD (r = 0.86, r = 0.67, respectively, p < 0.01), and two-thirds of the haBETA components can be estimated by htBETA using the component analysis. The area under the ROC curve (AUC) for CAD in taBETA (0.493, p = n.s.) was smaller than that in haBETA (0.731, p < 0.01) or htBETA (0.757, p < 0.01); no difference was observed in AUC between haBETA and htBETA.

Conclusion

The stiffness of medium-sized muscular arteries of the age-independent thigh–ankle segment (taBETA) was constant, which was three times greater than that of the elastic artery of the heart–thigh artery (htBETA). Two-thirds of the haBETA components could be estimated using htBETA. The ROC curve analysis revealed that the AUC of haBETA could be replaced by that of htBETA, prolonging the measurement segment without affecting the diagnostic power for CAD.

Elevated cardio-ankle vascular index may be related to future stroke risk in Japanese subjects

BACKGROUND

The cardio-ankle vascular index (CAVI) has been proposed as a useful parameter for arteriosclerotic diseases. However, whether it is associated with stroke risk in Japanese subjects remains unclear.

METHODS

In total, 280 Japanese subjects (92 females, 52.6 ± 5 years old) underwent a medical check-up. CAVI value and risk factors for arterial dysfunction were evaluated; the predicted 10-year stroke risk was measured by the Japan Public Health Center study.

RESULTS

Age, sex, body mass index, and systolic blood pressure were significant independent predictors of CAVI. CAVI values were significantly elevated in the high, compared with the medium-low and low predicted risk groups. A significant odds ratio (OR) for the high-risk group was noted in the highest quartile of CAVI values (OR, 14.67; 95% confidence interval [CI], 3.17-68.0), compared with the lowest quartile, after adjusting for potential confounders. A significant OR for very high predicted stroke risk was also found for each quartile increase (OR, 3.04; 95% CI, 1.87-4.94) and 1-standard deviation increase (OR, 2.24; 95% CI, 1.52-3.30) in CAVI value.

CONCLUSION

Elevated CAVI values were related to an elevated predicted stroke risk, suggesting that CAVI could be a suitable surrogate marker for finding subjects at an increased risk of first-ever stroke.

Age-related difference of the association of cardiovascular risk factors with the cardio-ankle vascular index in the Cardiovascular Prognostic Coupling Study in Japan (the Coupling Registry)

The value of the cardio-ankle vascular index (CAVI) increases with age. All large-scale studies of the CAVI have investigated patients <80 years old. Thus, the clinical characteristics of high CAVI in patients aged 80 or more remain unclear. Therefore, we investigated (1) the CAVI in very elderly patients and (2) the determinants of a high CAVI in high-risk patients, including very elderly patients. The Cardiovascular Prognostic Coupling Study in Japan (Coupling Registry) is a prospective observational study of Japanese outpatients with any cardiovascular risk factors. We enrolled 5109 patients from 30 institutions (average age 68.7 ± 11.4 years, 52.4% males). We investigated the determinants of the CAVI by separating the patients into three groups: 970 middle-aged (<60 years), 3252 elderly (60-79 years), and 887 very elderly (≥80 years) patients. The CAVI values of the males were significantly higher those of the females in all age groups (<60 years: 7.81 ± 1.11 vs. 7.38 ± 0.99, P < .001; 60-79 years: 9.20 ± 1.29 vs. 8.66 ± 1.07, P < .001; ≥80 years: 10.26 ± 1.39 vs. 9.51 ± 1.12, P < .001). In all age groups, the CAVI of the patients with diabetes/glucose tolerance disorder was higher than that of the patients without diabetes/glucose tolerance disorder (<60 years: 7.82 ± 1.22 vs 7.58 ± 1.03, P = .002; 60-79 years: 9.23 ± 1.20 vs 8.78 ± 1.19, P < .001; ≥80 years: 10.04 ± 1.24 vs 9.75 ± 1.32, P = .002). The determinants of the CAVI in these very elderly patients were age, male sex, low BMI, and mean blood pressure. Diabetes/glucose tolerance disorder and glucose were independently associated with the CAVI in the patients aged <60 years and 60-79 years, but not in those aged ≥80 years after adjusting for other covariates.

Wearable Piezoelectric-Based System for Continuous Beat-to-Beat Blood Pressure Measurement

Non-invasive continuous blood pressure measurement is an emerging issue that potentially can be applied to cardiovascular disease monitoring and prediction. Recently, many groups have proposed the pulse transition time (PTT) method to estimate blood pressure for long-term monitoring. However, the PTT-based methods for blood pressure estimation are limited by non-specific estimation models and require multiple calibrations. This study aims to develop a low-cost wearable piezoelectric-based system for continuous beat-to-beat blood pressure measurement. The pressure change in the radial artery was extracted by systolic and diastolic feature points in pressure pulse wave (PPW) and the pressure sensitivity of the sensor. The proposed system showed a reliable accuracy of systolic blood pressure (SBP) (mean absolute error (MAE) ± standard deviation (SD) 1.52 ± 0.30 mmHg) and diastolic blood pressure (DBP, MAE ± SD 1.83 ± 0.50), and its performance agreed with standard criteria of MAE within 5 mmHg and SD within ±8 mmHg. In conclusion, this study successfully developed a low-cost, high-accuracy piezoelectric-based system for continuous beat-to-beat SBP and DBP measurement without multiple calibrations and complex regression analysis. The system is potentially suitable for continuous, long-term blood pressure-monitoring applications.

Pulse transit time based respiratory rate estimation with singular spectrum analysis

Respiratory rate (RR) is an important vital sign which can be difficult to measure accurately and unobtrusively in routine clinical practice. Pulse transit time (PTT), on the other hand, is unobtrusive to collect from electrocardiogram (ECG) and photoplethysmogram (PPG) signals. Using PTT is a novel method to estimate and monitor blood pressure (BP) and RR. This study aimed to estimate continuous RR using PTT with singular spectrum analysis to extract respiratory components. The performance of this method was validated on 17 subjects who carried out spontaneous breathing and controlled deep breathing conditions. Three types of estimated RR parameters (average RR by power spectral density (PSD) (RR_PSD), number of breaths (RR_#), and instantaneous RR (RR_inst)) were compared with the corresponding reference RR. The reference RR was collected using a respiratory belt. Our findings demonstrate that the PTT signal reliably tracked respiratory variation with a root mean square error of 0.84, 1.11, and 0.74 breaths/min for RR_PSD, RR_#, and RR_inst estimations, respectively. Overall, RR estimated by PTT was more accurate than heart/pulse rate interval, QRS area, and PPG amplitude, which were also extracted from ECG and PPG. The results suggest that it may be feasible to use PTT as an estimation of RR and that ECG and PPG may be relied upon for monitoring not only RR but also BP and heart rate. Graphical abstract The Pulse Transit Time (PTT) based Respiratory Rate (RR) estimation with Singular Spectrum Analysis (SSA) provides a superior performance than the method with other respiratory indicators extracted from Electrocardiogram (ECG) or Photoplethysmogram (PPG).

Cardio-ankle vascular index is linked to deranged metabolic status, especially high HbA1c and monocyte-chemoattractant-1 protein, in predialysis chronic kidney disease

INTRODUCTION AND PURPOSE

Arterial stiffness is an independent predictor of cardiovascular disease in chronic kidney disease (CKD). Cardio-ankle vascular index (CAVI) is a newly developed method used to assess arterial stiffness, independent of changes in blood pressure. CAVI reflects stiffness and atherosclerosis at the thoracic, abdominal, common iliac, femoral, and tibial artery levels. In predialysis stage 3-5 diabetic and nondiabetic CKD patients, CAVI levels and its relation to atherosclerosis-associated risk factors including monocyte-chemoattractant protein-1 (MCP-1), sclerostin, fibroblast growth factor-23 (FGF-23), Klotho, and 25-OH vitamin D were determined.

MATERIALS AND METHODS

The study was performed on three age-matched and gender-matched groups. Group 1 included 46 stage 3-5 nondiabetic CKD patients, group 2 included 44 stage 3-5 diabetic CKD patients, and group 3 included 44 non-uremic controls. All subjects underwent CAVI measurement. Serum glycated hemoglobin (HbA1c), total calcium, phosphorus, parathormone, FGF-23, Klotho, MCP-1, sclerostin, and 25-OH vitamin D were determined using standard methods.

RESULTS

CAVI level was 8.22 ± 0.18 m/s in diabetic CKD patients and significantly higher than in nondiabetic CKD (7.61 ± 0.18 m/s) and control (7.59 ± 0.17 m/s) patients. FGF-23 level was higher in the CKD groups than controls but not statistically significant. MCP-1 level was significantly higher in diabetic CKD patients. Klotho and sclerostin levels were significantly lower in diabetic CKD patients. In the whole cohort, CAVI showed positive correlations with age (r = 0.447, p < 0.0001), smoking (r = 0.331, p = 0.035), mean arterial blood pressure (MABP; r = 0.327, p < 0.0001), fasting blood glucose (r = 0.185, p = 0.033), and HbA1c (r = 0.258, p = 0.003). Stepwise regression analysis revealed that age (p = 0.0001, B = 0.461), MABP (p < 0.0001, B = 0.365), HbA1c (p = 0.003, B = 0.251), and MCP-1 (p = 0.013, B = 0.214) independently predicted CAVI levels.

CONCLUSION

Our results indicate higher CAVI levels, therefore, resulting in increased arterial stiffness in the setting of diabetic CKD. Apart from age and MABP, deranged metabolic status, especially increased HbA1c and MCP-1 levels, is also independently associated with increasing CAVI levels in CKD patients. These results emphasize the importance of metabolic control in the development of arterial stiffness in CKD patients, which is an early predictor of developing cardiovascular complications.

A New Wearable Device for Blood Pressure Estimation Using Photoplethysmogram

We present a novel smartwatch, CareUp ® , for estimating the Blood Pressure (BP) in real time. It consists of two pulse oximeters: one placed on the back and one on the front of the device. Placing the index finger on the front oximeter starts the acquisition of two photoplethysmograms (PPG); the signals are then filtered and cross-correlated to obtain a Time Delay between them, called Pulse Transit Time (PTT). The Heart Rate (HR) (estimated from the finger PPG) and the PTT are then input in a linear model to give an estimation of the Systolic and Diastolic BP. The performance of the smartwatch in measuring BP have been validated in the Institut Coeur Paris Centre Turin (ICPC), using a sphygmomanometer, on 44 subjects. During the validation, the measures of the CareUp ® were compared to those of two oscillometry-based devices already available on the market: Thuasne ® and Magnien ® . The results showed an accuracy comparable to the oscillometry-based devices and they almost agreed with the American Association for the Advancement of Medical Instrumentation standard for non-automated sphygmomanometers. The integration of the BP estimation algorithm in the smartwatch makes the CareUp ® an easy-to-use, wearable device for monitoring the BP in real time.

Constitutive interpretation of arterial stiffness in clinical studies: a methodological review

Clinical assessment of arterial stiffness relies on noninvasive measurements of regional pulse wave velocity or local distensibility. However, arterial stiffness measures do not discriminate underlying changes in arterial wall constituent properties (e.g., in collagen, elastin, or smooth muscle), which is highly relevant for development and monitoring of treatment. In arterial stiffness in recent clinical-epidemiological studies, we systematically review clinical-epidemiological studies (2012–) that interpreted arterial stiffness changes in terms of changes in arterial wall constituent properties (63 studies included of 514 studies found). Most studies that did so were association studies (52 of 63 studies) providing limited causal evidence. Intervention studies (11 of 63 studies) addressed changes in arterial stiffness through the modulation of extracellular matrix integrity (5 of 11 studies) or smooth muscle tone (6 of 11 studies). A handful of studies (3 of 63 studies) used mathematical modeling to discriminate between extracellular matrix components. Overall, there exists a notable gap in the mechanistic interpretation of stiffness findings. In constitutive model-based interpretation, we first introduce constitutive-based modeling and use it to illustrate the relationship between constituent properties and stiffness measurements (“forward” approach). We then review all literature on modeling approaches for the constitutive interpretation of clinical arterial stiffness data (“inverse” approach), which are aimed at estimation of constitutive properties from arterial stiffness measurements to benefit treatment development and monitoring. Importantly, any modeling approach requires a tradeoff between model complexity and measurable data. Therefore, the feasibility of changing in vivo the biaxial mechanics and/or vascular smooth muscle tone should be explored. The effectiveness of modeling approaches should be confirmed using uncertainty quantification and sensitivity analysis. Taken together, constitutive modeling can significantly improve clinical interpretation of arterial stiffness findings.

Coefficients in the CAVI Equation and the Comparison Between CAVI With and Without the Coefficients Using Clinical Data

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 (haβ) were compared in both an epidemiological study and an acute clinical study.

Methods: In the epidemiological study, the significances of CAVI and haβ 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 haβ values over a 20-min period.

Results: There was no discrepancy in terms of statistically significant differences between CAVI and haβ among subjects with or without risk factors. Furthermore, there was also no discrepancy in terms of statistically significant differences between CAVI and haβ 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 haβ. These results suggest that both are valid as indices of stiffness of the arterial tree from the origin of the aorta to the ankle.

Arterial Stiffness: A Prognostic Marker in Coronary Heart Disease. Available Methods and Clinical Application

Multiple biomarkers may predict short and long-term prognosis in patients with coronary heart disease, but their impact is limited when used in addition to established risk factors such blood pressure, cholesterol levels, diabetes mellitus, smoking as well as age and sex. Arteries are an integral part of the cardiovascular (CV) system. Arterial stiffness has been shown to be a predictor of cardiovascular events and mortality independent of traditional risk factors. It has also been shown that increased arterial stiffness may predict cardiovascular events in asymptomatic individuals without overt cardiovascular disease. Measuring arterial stiffness may, therefore, identify patients at risk at an early stage. Antihypertensive treatment has been shown to reduce arterial stiffness beyond its antihypertensive effect. Arterial stiffness could, therefore, be a surrogate marker of treatment that relates to prognosis. Arterial stiffness has mostly been used in research protocols, and its use as a prognostic indicator in clinical practice is still uncommon. Several methods exist that can determine parameters related to arterial stiffness, both local and in specific artery beds such as the aorta. In this brief review we present methods to evaluate arterial stiffness, their clinical utility, limitations and the advantages of a novel method, the Cardio-Ankle Vascular Index. Easier and more reproducible methods to evaluate arterial stiffness may increase the use of parameter as a risk factor for coronary heart disease in common clinical practice.

Aortic stiffness and blood pressure variability in young people: a multimodality investigation of central and peripheral vasculature

Introduction:

Increased blood pressure (BP) variability is a cardiovascular risk marker for young individuals and may relate to the ability of their aorta to buffer cardiac output. We used a multimodality approach to determine relations between central and peripheral arterial stiffness and BP variability.

Methods:

We studied 152 adults (mean age of 31 years) who had BP variability measures based on SD of awake ambulatory BPs, 24-h weighted SD and average real variability (ARV). Global and regional aortic distensibility was measured by cardiovascular magnetic resonance, arterial stiffness by cardio-ankle vascular index (CAVI) and pulse wave velocity (PWV) by SphygmoCor (carotid–femoral) and Vicorder (brachial–femoral).

Results:

In young people, free from overt cardiovascular disease, all indices of SBP and DBP variability correlated with aortic distensibility (global aortic distensibility versus awake SBP SD: r = −0.39, P < 0.001; SBP ARV: r = −0.34, P < 0.001; weighted 24-h SBP SD: r = −0.42, P < 0.001). CAVI, which closely associated with aortic distensibility, also related to DBP variability, as well as awake SBP SD (r = 0.19, P < 0.05) and weighted 24-h SBP SD (r = 0.24, P < 0.01), with a trend for SBP ARV (r = 0.17, P = 0.06). In contrast, associations with PWV were only between carotid–femoral PWV and weighted SD of SBP (r = 0.20, P = 0.03) as well as weighted and ARV of DBP.

Conclusion:

Greater BP variability in young people relates to increases in central aortic stiffness, strategies to measure and protect aortic function from a young age may be important to reduce cardiovascular risk.

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 CAVI₀. The present study aims to establish a method of calculating [Formula: see text] 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 CAVI₀ 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 CAVI₀ were estimated to be 0.842 [0.836 0.848] and 0.753 [0.721 0.786] (mean [95%CI]), respectively. Equations to estimate CAVI₀ from CAVI_VS, and to directly calculate CAVI₀ 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 [Formula: see text] during a study, as well as retrospective estimation of [Formula: see text] from CAVI_VS in already published studies or where the original transit time values are not available, paving the way for thorough comparison of CAVI₀ 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, CAVI₀. In the present study, we derived equations to directly obtain CAVI₀ using data from the VaSera device. Our results permit straightforward calculation of [Formula: see text] during a study, as well as retrospective estimation of [Formula: see text] from CAVI_VS in already published studies, paving the way for thorough comparison of CAVI₀ to CAVI_VS in clinical and research settings.

Options for Dealing with Pressure Dependence of Pulse Wave Velocity as a Measure of Arterial Stiffness: An Update of Cardio-Ankle Vascular Index (CAVI) and CAVI0

Pulse wave velocity (PWV), a marker of arterial stiffness, is known to change instantaneously with changes in blood pressure. In this mini-review, we discuss two main approaches for handling the blood pressure dependence of PWV: (1) converting PWV into a pressure-independent index, and (2) correcting PWV per se for the pressure dependence. Under option 1, we focus on cardio-ankle vascular index (CAVI). CAVI is essentially a form of stiffness index β - CAVI is estimated for a (heart-to-ankle) trajectory, whereas β is estimated for a single artery from pressure and diameter measurements. Stiffness index β, and therefore also CAVI, have been shown to theoretically exhibit a slight residual blood pressure dependence due to the use of diastolic blood pressure instead of a fixed reference blood pressure. Additionally, CAVI exhibits pressure dependence due to the use of an estimated derivative of the pressure-diameter relationship. In this mini-review, we will address CAVI's blood pressure dependence theoretically, but also statistically. Furthermore, we review corrected indices (CAVI₀ and β₀) that theoretically do not show a residual blood pressure dependence. Under option 2, three ways of correcting PWV are reviewed: (1) using an exponential relationship between pressure and cross-sectional area, (2) by statistical model adjustment, and (3) through reference values or rule of thumb. Method 2 requires a population to be studied to characterise the statistical model, and method 3 requires a representative reference study. Given these limitations, method 1 seems preferable for correcting PWV per se for its blood pressure dependence. In summary, several options are available to handle the blood pressure dependence of PWV. If a blood pressure-independent index is sought, CAVI₀ is theoretically preferable over CAVI. If correcting PWV per se is required, using an exponential pressure-area relationship provides the user with a method to correct PWV on an individual basis.

The Effect of Nitroglycerin on Arterial Stiffness of the Aorta and the Femoral-Tibial Arteries

Aim: The effect of nitroglycerin on proper arterial stiffness of the arterial tree has not been fully clarified. The cardio-ankle vascular index (CAVI), which is an application of the stiffness parameter β theory on the arterial tree from the origin of the aorta to the ankle, was developed recently. Furthermore, the stiffness of the aorta (heart-thigh β (htBeta)) and of the femoral-tibial arteries (thigh to ankle β (taBeta)) could be monitored by applying the same theory. The effects of nitroglycerin on CAVI, htBeta, and taBeta were studied comparing the values of healthy people and those of arteriosclerotic patients.

Methods: The subjects were healthy people (CAVI < 7.5, n = 25) and arteriosclerotic patients (CAVI > 9, n = 25). Nitroglycerin (0.3 mg) was administrated sublingually, and various arterial stiffness indices were measured at one-minute intervals for a period of 20 minutes using Vasera VS-1500 (Fukuda Denshi, Tokyo).

Results: After the administration of nitroglycerin in healthy people, CAVI decreased significantly after 5 min. [from 6.76(6.32–7.27) to 5.50(4.70–6.21), P < 0.05], and recovered after 15 min. htBeta [from 5.10(4.76–5.76) to 3.96(3.35–4.79), P < 0.05], and taBeta [from 14.41(10.80–16.33) to 10.72 (9.19–13.01), P < 0.05] also decreased significantly. In arteriosclerotic patients, CAVI decreased after 5 min. [from 10.47(9.67–11.29) to 9.71(8.74–10.57), P < 0.05] and recovered after 15 min. htBeta did not significantly change [from 12.00(11.46–13.21) to 11.81(10.14–13.83), ns], but taBeta decreased significantly [from 18.55(12.93–23.42) to 12.37(9.68–16.99), P < 0.05].

Conclusion: These results indicate that a nitroglycerin-induced decrease of arterial stiffness is more prominent in muscular arteries than in elastic arteries, and this effect was preserved much more prominently in arteriosclerotic patients than in healthy people.

Vascular Physiology according to Clinical Scenario in Patients with Acute Heart Failure: Evaluation using the Cardio-Ankle Vascular Index

Increased aortic stiffness may be an important cause of acute heart failure (AHF). Clinical scenario (CS), which classifies the pathophysiology of AHF based on the initial systolic blood pressure (sBP), was proposed to provide the most appropriate therapy for AHF patients. In CS, elevated aortic stiffness, vascular failure, has been considered as a feature of patients categorized as CS1 (sBP > 140 mmHg at initial presentation). However, whether elevated aortic stiffness, vascular failure, is present in such patients has not been fully elucidated. Therefore, we assessed aortic stiffness in AHF patients using the cardio-ankle vascular index (CAVI), which is considered to be independent of instantaneous blood pressure. Sixty-four consecutive AHF patients (mean age, 70.6 ± 12.8 years; 39 men) were classified with CS, based on their initial sBP: CS1: sBP > 140 mmHg (n = 29); CS2: sBP 100-140 mmHg (n = 22); and CS3: sBP < 100 mmHg (n = 13). There were significant group differences in CAVI (CS1 vs. CS2 vs. CS3: 9.7 ± 1.4 vs. 8.4 ± 1.7 vs. 8.3 ± 1.7, p = 0.006, analysis of variance). CAVI was significantly higher in CS1 than in CS2 (p = 0.02) and CS3 (p = 0.04). CAVI did not significantly correlate with sBP at the time of measurement of CAVI (r = 0.24 and p = 0.06). Aortic stiffness assessed using blood pressure-independent methodology apparently increased in CS1 AHF patients. We conclude that vascular failure is a feature of CS1 AHF initiation.

Assessment of Arterial Stiffness Using the Cardio-Ankle Vascular Index

BACKGROUND

Arterial stiffness is an independent predictor of outcomes for patients with cardiovascular disease. Although measurement of pulse wave velocity is a widely accepted, noninvasive approach for the assessment of arterial stiffness, its accuracy is affected by changes in blood pressure.

SUMMARY

The cardio-ankle vascular index (CAVI) is an index of the overall stiffness of the artery from the origin of the aorta to the ankle and is theoretically independent of blood pressure at the time of measurement. CAVI increases linearly with age and is elevated even in mild arteriosclerotic disease. It can identify differences in the degree of arteriosclerosis among patients with severe arteriosclerotic disease and better reflects the severity of disease of the coronary artery than does brachial-ankle pulse wave velocity. Patients with higher CAVI values show a poor prognosis compared with those with lower CAVI values. Furthermore, CAVI can be lowered by controlling diabetes mellitus and hypertension.

KEY MESSAGES

The primary aims of assessing arterial stiffness using CAVI are to assist in the early detection of arteriosclerosis, allowing timely treatment and lifestyle modification, and to quantitatively evaluate the progression of disease and the effectiveness of treatment. Whether CAVI-guided therapy can improve prognosis in high-risk patients needs to be further examined to confirm the clinical usefulness of this measure.

Association between the Cardio-Ankle Vascular Index and Executive Function in Community-Dwelling Elderly People

AIM

The aim of this study was to investigate the cross-sectional association between arterial stiffness (AS) measured with the cardio-ankle vascular index (CAVI) and executive function in community-dwelling elderly people.

METHODS

Subjects were 140 community-dwelling elderly people who participated in the study at Kobe, Japan during the period of August-September 2014, of which 126 (mean age±SD: 73.2±6.1, female: 67.5%) met the inclusion criteria and completed the study. Age, sex, body mass index, global cognition, existence of chronic disease, medication, smoking history, and years of education were assessed. The degree of AS was assessed using CAVI. Executive function was assessed using the Category Word Fluency Test (CWFT), Letter Word Fluency Test (LWFT), and Digit Symbol Substitution Test (DSST). We used a correlation analysis and multiple linear regression analysis to investigate whether higher CAVI was independently associated with lower executive function.

RESULTS

In the univariate analysis, higher mean CAVI correlated with lower CWFT (rho=－0.21, p=0.020), LWFT (rho=－0.32, p＜0.001), and DSST (rho=－0.31, p＜0.001). In the multivariate analysis, higher mean CAVI was associated with lower LWFT (β=－0.21, p=0.046) after adjusting for confounding factors, although there was no association with CWFT (β=－0.05, p=0.61) and DSST (β=－0.06, p=0.51).

CONCLUSIONS

We found that high CAVI was associated with lower LWFT. These results suggest that arterial stiffness is associated with lower performance in phonemic fluency.

Seeking a blood pressure-independent measure of vascular properties

Pulse wave velocity (PWV) and pulse pressure (PP) are blood pressure (BP)-dependent surrogates for vascular stiffness. Considering that there are no clinically useful markers for arterial stiffness that are BP-independent, our objective was to identify novel indices of arterial stiffness and compare them with previously described markers. PWV and PP were measured in young and old male Fisher rats and in young and old male spontaneously hypertensive rats (SHR) over a wide range of BPs. The BP dependence of these and several other indices of vascular stiffness were evaluated. An index incorporating PWV and PP was also constructed. Both PWV and PP increase in a non-linear manner with rising BP for both strains of animals (Fisher and SHRs). Age markedly changes the relationship between PWV or PP and BP. The previously described Ambulatory Arterial Stiffness Index (AASI) was able to differentiate between young and old vasculature, whereas the Cardio-Ankle Vascular Index (CAVI) did not reliably differentiate between the two. The novel Arterial Stiffness Index (ASI) differentiated stiffer from more compliant vasculature. Considering the limitations of the currently available indices of arterial stiffness, we propose a novel index of intrinsic arterial stiffness, the ASI, which is robust over a range of BPs and allows one to distinguish between compliant and stiff vasculature in both Fisher rats and SHRs. Further studies are necessary to validate this index in other settings.

Cardio-ankle vascular index predicts for the incidence of cardiovascular events in obese patients: a multicenter prospective cohort study (Japan Obesity and Metabolic Syndrome Study: JOMS)

OBJECTIVE

The cardio-ankle vascular index (CAVI) is an index of arterial stiffness less dependent on blood pressure and an indicator suitable for assessing the arterial dysfunction. However, it remains unclear whether CAVI can predict the outcome of cardiovascular diseases (CVD) in obese patients.

METHODS

A total of 425 obese Japanese outpatients (189 men and 236 women, mean age: 51.5 years) were enrolled in a multicenter prospective cohort Japan, the Japan Obesity and Metabolic Syndrome Study (JOMS). Primary analysis regarding measurements of cardiovascular risk factors including CAVI and the occurrence of macrovascular complications was based on following the participants over a 5-year period.

RESULTS

Of the eligible patients, 300 (78%) were followed into the fifth year. During the study period, 15 coronary heart disease, 7 stroke, and 6 arteriosclerosis obliterans events occurred. All events occurred in 28 patients, and CVD incidence rate was 15.8 per 1000 person-years. In the analysis of adjusted models for traditional risk factors, CAVI was a significant factor for the incidence of events. In addition, high CAVI and low HDL-cholesterol were significant factors for the incidence of events in Cox stepwise multivariate analysis when age- and sex-adjusted (CAVI [per 1]: HR = 1.44 [1.02-2.02], p = 0.037; HDL-cholesterol [per 1 mmol/L]: HR = 0.20 [0.06-0.69], p = 0.011). In addition, CAVI added value to atherosclerotic cardiovascular disease risk score in predicting the development of CVD.

CONCLUSION

This study demonstrates for the first time that CAVI is an effective predictor of CVD events in obese patients.

The Role of Monitoring Arterial Stiffness with Cardio-Ankle Vascular Index in the Control of Lifestyle-Related Diseases

Arteriosclerosis is a major contributor to cardiovascular diseases. One of the difficulties in controlling those diseases is the lack of a suitable indicator of arteriosclerosis or arterial injury in routine clinical practice. Arterial stiffness was supposed to be one of the monitoring indexes of arteriosclerosis. Cardio-ankle vascular index (CAVI) is reflecting the stiffness of the arterial tree from the origin of the aorta to the ankle, and one of the features of CAVI is independency from blood pressure at a measuring time. When doxazosin, an α1-adrenergic blocker, was administered, CAVI decreased, indicating that arterial stiffness is composed of both organic stiffness and functional stiffness, which reflects the contraction of arterial smooth muscle. CAVI shows a high value with aging and in many arteriosclerotic diseases, and is also high in persons possessing main coronary risk factors such as diabetes mellitus, metabolic syndrome, hypertension and smoking. Furthermore, when the most of those risk factors were controlled by proper methods, CAVI improved. Furthermore, the co-relationship between CAVI and heart function was demonstrated during treatment of heart failure. This paper reviews the principle and rationale of CAVI, and discusses the meaning of monitoring CAVI in following up so-called lifestyle-related diseases and cardiac dysfunction in routine clinical practice.

Association between the Postprandial Glucose Levels and Arterial Stiffness Measured According to the Cardio-ankle Vascular Index in Non-diabetic Subjects

OBJECTIVE

Although a relationship between post-challenge hyperglycemia and arterial stiffness has been reported, the relationship between the postprandial glucose levels and cardio-ankle vascular index (CAVI) in non-diabetic subjects is not clear. This study thus evaluated the association between the postprandial glucose levels after a composite meal and the degree of arterial stiffness measured according to CAVI in non-diabetic subjects.

METHODS

The subjects included 1,291 individuals (655 men and 636 women; mean age, 48.6 years; range, 23-85 years) who underwent medical examinations, including blood tests and CAVI assessments, between October 2005 and April 2012. The 1-hour postprandial glucose levels were determined after a 600-kcal traditional Japanese meal.

RESULTS

The CAVI values were significantly higher in the subjects with higher 1-hour postprandial glucose levels (≥140 mg/dL in men; ≥158 mg/dL in women). A simple regression analysis indicated that the CAVI values were significantly correlated with the 1-hour postprandial glucose levels in men (r=0.286, p<0.0001) and women (r=0.228, p<0.0001). After adjusting for age, BMI, systolic blood pressure, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, 1-hour postprandial glucose, homeostatis model assessment of insulin resistance, estimated glemerular filtration rate, and high sensitive C-reactive protein, stepwise multiple regression analysis demonstrated that the 1-hour postprandial glucose level was an independent predictor associated with the CAVI in men (p=0.003) and older women 50 years of age or older (p=0.003).

CONCLUSION

This study demonstrated that the 1-hour postprandial glucose levels are associated with increased CAVI values in non-diabetic men and older women 50 years of age or older.

Physical exercise improves arterial stiffness after spinal cord injury

OBJECTIVE/BACKGROUND

Aortic pulse wave velocity (PWV), the gold-standard assessment of central arterial stiffness, has prognostic value for cardiovascular disease risk in able-bodied individuals. The aim of this study was to compare aortic PWV in athletes and non-athletes with spinal cord injury (SCI).

DESIGN

Cross-sectional comparison.

METHODS

Aortic PWV was assessed in 20 individuals with motor-complete, chronic SCI (C2-T5; 18 ± 8 years post-injury) using applanation tonometry at the carotid and femoral arterial sites. Ten elite hand-cyclists were matched for sex to 10 non-athletes; age and time since injury were comparable between the groups. Heart rate and discrete brachial blood pressure measurements were collected throughout testing.

OUTCOME MEASURES

Aortic PWV, blood pressure, heart rate.

RESULTS

Aortic PWV was significantly lower in athletes vs. non-athletes (6.9 ± 1.0 vs. 8.7 ± 2.5 m/second, P = 0.044). There were no significant between-group differences in resting supine mean arterial blood pressure (91 ± 19 vs. 81 ± 10 mmHg) and heart rate (60 ± 10 vs. 58 ± 6 b.p.m.).

CONCLUSION

Athletes with SCI exhibited improved central arterial stiffness compared to non-athletes, which is in agreement with the previous able-bodied literature. This finding implies that chronic exercise training may improve arterial health and potentially lower cardiovascular disease risk in the SCI population.

Association between urinary 6-sulfatoxymelatonin excretion and arterial stiffness in the general elderly population: the HEIJO-KYO cohort

CONTEXT

Melatonin may have a preventive effect on atherosclerosis by regulating sleep quality and circadian biological rhythmicity. However, whether endogenous melatonin is associated with arterial stiffness, a marker reflecting atherosclerosis, is unclear.

OBJECTIVE

The objective of the study was to determine the association between endogenous melatonin and arterial stiffness.

DESIGN AND PARTICIPANTS

A total of 641 community-based elderly individuals were enrolled in this cross-sectional study (mean age 71.4 y).

MEASURES

We measured overnight urinary 6-sulfatoxymelatonin excretion (UME) and cardioankle vascular index (CAVI) as indices of melatonin secretion and arterial stiffness, respectively.

RESULTS

The median UME was 6.8 μg (interquartile range 4.1-10.5) and the mean value of CAVI was 9.1 ± 1.1. High CAVI (ie, ≥ 9.0) was observed in 334 participants (52.1%). Univariate logistic regression models revealed marginal to significant associations between high CAVI and age, gender, body mass index, hypertension, diabetes, estimated glomerular filtration rate, log-transformed UME, bedtime, duration in bed, daytime physical activity, and log-transformed nighttime physical activity. In the multivariate logistic regression model, simultaneously adjusted for the former independent variables, higher log-transformed UME was significantly associated with a lower odds ratio (OR) for high CAVI (adjusted OR 0.708; 95% confidence interval 0.536-0.935; P = .015). This inverse association between log-transformed UME and high CAVI indicated that an increase in log-transformed UME by 1 SD was associated with an 18.1% (95% confidence interval 1.4-31.9) decrease in high CAVI prevalence.

CONCLUSIONS

UME is significantly and inversely associated with arterial stiffness in the general elderly population. The association was independent of several major causes of atherosclerosis.

A blood pressure monitoring method for stroke management

Blood pressure is one important risk factor for stroke prognosis. Therefore, continuous monitoring of blood pressure is crucial for preventing and predicting stroke. However, current blood pressure devices are mainly air-cuff based, which only can provide measurements intermittently. This study proposed a new blood pressure estimation method based on the pulse transit time to realize continuous monitoring. The proposed method integrated a linear model with a compensation algorithm. A calibration method was further developed to guarantee that the model was personalized for individuals. Variation and variability of pulse transit time were introduced to construct the compensation algorithm in the model. The proposed method was validated by the data collected from 30 healthy subjects, aged from 23 to 25 years old. By comparing the estimated value to the measurement from an oscillometry, the result showed that the mean error of the estimated blood pressure was −0.2 ± 2.4 mmHg and 0.5 ± 3.9 mmHg for systolic and diastolic blood pressure, respectively. In addition, the estimation performance of the proposed model is better than the linear model, especially for the diastolic blood pressure. The results indicate that the proposed method has promising potential to realize continuous blood pressure measurement.

Evaluation of blood pressure control using a new arterial stiffness parameter, cardio-ankle vascular index (CAVI)

Arterial stiffness has been known to be a surrogate marker of arteriosclerosis, and also of vascular function. Pulse wave velocity (PWV) had been the most popular index and was known to be a predictor of cardiovascular events. But, it depends on blood pressure at measuring time. To overcome this problem, cardio-ankle vascular index (CAVI) is developed. CAVI is derived from stiffness parameter β by Hayashi, and the equation of Bramwell-Hill, and is independent from blood pressure at a measuring time. Then, CAVI might reflect the proper change of arterial wall by antihypertensive agents.

CAVI shows high value with aging and in many arteriosclerotic diseases and is also high in persons with main coronary risk factors. Furthermore, CAVI is decreased by an administration of α₁ blocker, doxazosin for 2-4 hours, Those results suggested that CAVI reflected the arterial stiffness composed of organic components and of smooth muscle cell contracture. Angiotensin II receptor blocker, olmesartan decreased CAVI much more than that of calcium channel antagonist, amlodipine, even though the rates of decreased blood pressure were almost same. CAVI might differentiate the blood pressure-lowering agents from the point of the effects on proper arterial stiffness.

This paper reviewed the principle and rationale of CAVI, and the possibilities of clinical applications, especially in the studies of hypertension.

Pulse wave velocity in four extremities for assessing cardiovascular risk using a new device

Pulse wave velocity (PWV) is used for evaluating atherosclerosis; however, it is far from routine use. The authors validate a new device measuring PWV independently in each limb and explore its usefulness. Validity was studied in 40 patients. PWV was compared with endovascular measurements and comparisons were made between PWV in the extremities in 220 patients. The correlation between brachial PWV and endovascular catheter was (r=0.83, P<.001). The correlation coefficients for interobserver and intraobserver were r=0.87 and r=0.91, respectively. The sum of PWV in limbs allowed better stratification of patients according to cardiovascular risk. The validity and reproducibility of PWV measured with this device was good. The sum of PWV in extremities was a good index for stratifying patients according to vascular risk. These results suggest that the device is useful in the evaluation of arteriosclerosis and could possibly replace measurement devices available today.

Urine 6-sulfatoxymelatonin levels are inversely associated with arterial stiffness in post-menopausal women

OBJECT

The secretion of melatonin, a pleiotropic hormone mainly synthesized by the pineal gland, typically decreases with age and may be associated with the development of aging-related pathologic conditions such as cardiovascular disease. Atherosclerosis is an aging-related disease, the pathogenesis of which involves chronic inflammation and increased oxidative stress. Since melatonin has both anti-oxidant and anti-inflammatory properties, it may be associated with atherosclerosis. Therefore, we investigated the relationship between urine concentrations of 6-sulfatoxymelatonin (aMT6s) and arterial stiffness in post-menopausal women.

METHODS

A total of 66 post-menopausal women participated in the study. Melatonin secretion was estimated by measuring aMT6s levels in first morning urine samples. The cardio-ankle vascular index (CAVI) was used as an indicator of arterial stiffness.

RESULTS

Estimated mean CAVI decreased gradually with increasing aMT6s quartiles. The multivariate logistic regression analysis showed that the fourth aMT6s quartile was associated with a high CAVI with an adjusted odds ratio of 0.03 (95% confidence interval, 0.01-0.47).

CONCLUSION

Our study revealed an inverse relationship between urine aMT6s and arterial stiffness as determined by CAVI. Although it is impossible to determine causality, our results suggest that melatonin may have a beneficial role in the pathogenesis of atherosclerosis. Further prospective studies are required to establish the clinical significance of our study.

Acute decrease of cardio-ankle vascular index with the administration of beraprost sodium

AIM

A novel arterial stiffness index, the cardio-ankle vascular index (CAVI), has been proposed. To clarify the properties of CAVI, the effects of beraprost sodium (BPS), a prostaglandin (PG) I2 analogue, which has a potent vasodilating effect, on CAVI were studied and comparing with brachialankle pulse wave velocity (baPWV) in healthy volunteers.

METHODS

Male volunteers (n=18, 46.3±4.2 yr) were enrolled in this study and administered BPS (40 µg). CAVI and baPWV were measured every hour for 4 hours.

RESULTS

When BPS was administered to 18 healthy volunteers, systolic blood pressure and diastolic blood pressure fluctuated slightly, but the means did not change. CAVI significantly decreased in the 1st hour from 8.3±0.34 (mean±SE) to 7.9±0.34 (p<0.05) and this decrease persisted for 3 hours, whereas baPWV did not significantly change. ΔbaPWV each time was significantly correlated with both Δsystolic blood pressure and Δdiastolic blood pressure, but ΔCAVI did not correlate with either Δsystolic blood pressure (r=-0.12, p=0.38) or Δdiastolc blood pressure (r=-0.22, p=0.10).

CONCLUSIONS

Beraprost sodium did not decrease blood pressure, but decreased CAVI, whereas baPWV did not change. These results indicate that CAVI partly reflected the contraction of arterial smooth muscle cells.

Electrocardiogram-assisted blood pressure estimation

Accurate automatic noninvasive assessment of blood pressure (BP) presents a challenge due to conditions like arrhythmias, obesity, and postural changes that tend to obfuscate arterial amplitude pulsations sensed by the cuff. Researchers tried to overcome this challenge by analyzing oscillometric pulses with the aid of a higher fidelity signal-the electrocardiogram (ECG). Moreover, pulse transit time (PTT) was employed to provide an additional method for BP estimation. However, these methods were not fully developed, suitably integrated, or tested. To address these issues, we present a novel method whereby ECG-assisted oscillometric and PTT (measured between ECG R-peaks and maximum slope of arterial pulse peaks) analyses are seamlessly integrated into the oscillometric BP measurement paradigm. The method bolsters oscillometric analysis (amplitude modulation) with more reliable ECG R-peaks provides a complementary measure with PTT analysis (temporal modulation) and fuses this information for robust BP estimation. We have integrated this technology into a prototype that comprises a BP cuff with an embedded conductive fabric ECG electrode, associated hardware, and algorithms. A pilot study has been undertaken on ten healthy subjects (150 recordings) to validate the performance of our prototype against United States Food and Drug Administration approved Omron oscillometric monitor (HEM-790IT). Our prototype achieves mean absolute difference of less than 5 mmHg and grade A as per the British Hypertension Society protocol for estimating BP, with the reference Omron monitor.