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Arterial stiffness is an important, independent determinant of cardiovascular risk. Pulse wave velocity (PWV) has been used as a valuable index of arterial stiffness and as a surrogate marker for atherosclerosis. Chunghyul-dan (CHD) has anti-hyperlipidemic activity, anti-inflammatory activity and anti-atherogenic effects. To determine its clinical effect on increased arterial stiffness, we examined whether CHD improves arterial stiffness in patients with increased brachial-ankle PWV (baPWV). Thirty-five subjects with increased baPWV (> 1400 cm/sec) were recruited and randomized to a treatment group (20 subjects) or a control group (15 subjects). The treatment group was administered CHD at a dose of 600 mg three times a day for 8 weeks, and the control group received no medication (observation only). baPWV was assessed using a pulse pressure analyzer at baseline and after 8 weeks. Blood pressure and serum lipid profile were monitored in the treatment group. Our results indicate that baPWV was lowered significantly in the treatment group after 8 weeks of medication (p < 0.05), but not in the control group. Moreover, there were no significant changes in blood pressure and serum lipids profile except triglyceride level suggesting that the effect is largely independent of CHD's lipid-lowering effect or a blood pressure change. In conclusion, CHD appears to improve arterial stiffness in patients with increased PWV.

Indices obtained from the second derivative of the digital volume pulse waveform have been proposed to characterize vascular aging, arterial rigidity, and the effects of vasoactive drugs. The purpose of this study was to assess the effects of manual needling of PC6 on SD_DVP indices in healthy and untreated hypertensive subjects. AI, B:A, and D:A indices, based on the height of the wave components of SD_DVP, in 40 healthy subjects and 25 untreated hypertensive subjects were compared. DVP was obtained by measuring infrared light transmission through the finger. For each subject, 20-min-long DVP registration was obtained. PC6 was stimulated unilaterally by manual needling for 5 min (1–6 min). In each subject, pre-acupuncture DVP indices were compared to those of during acupuncture (1 vs. 4 min) and post-acupuncture (1 vs. 18 min). In healthy subjects, AI was significantly improved when comparing the pre- to the post-acupuncture values. In hypertensive subjects, the SD_DVP indices improved significantly as follows: the AI index when the value of pre-acupuncture comparing to that of during acupuncture and post-acupuncture values; B:A and D:A indices when the pre-comparing to post-acupuncture values. There were significant differences between healthy and hypertensive subjects in AI, B:A, and D:A at baseline and in B:A in the during acupuncture period; there were no significant differences at post-acupuncture. These results indicate that manual needling of PC6 produced acute effects on vascular pathophysiology. Moreover, PC6 needling produced changes in SD_DVP indices related to both large artery stiffness and the reflected wave originating in small arteries.

It has been found that a pronounced secondary systolic peak appears on the oscillometric wave recorded by a brachial oscillometric cuff as cuff pressure is raised to a suprasystolic level. This finding has accordingly motivated some studies aimed to explore the potential value carried by the cuff wave for assessing arterial stiffness. However, so far, there remain considerable controversies in the literature regarding the cardiovascular properties that dominate the characteristics of the cuff wave. In this context, we developed a simple arterial-tree model and applied it to investigate the respective influence on the cuff wave of various cardiovascular properties and the associated wave interaction phenomena. It was found that (1) neither aortic stiffness nor brachial arterial stiffness can uniquely determine the time lag (Δt) between the first and secondary peaks of the cuff wave, although both of them significantly influence Δt; and (2) the BAIx (an index that characterize the height of the secondary peak relative to the first) is sensitive to most of the investigated cardiovascular properties and physiological conditions, such as arterial stiffness, intensity of wave reflection in the lower body and heart rate, etc. These findings suggest that the reliability of assessing aortic stiffness based solely on the timings and heights of the two peaks is limited. Moreover, we argued that the controversial findings presented in previous model-based studies are likely to be caused by limitations related to the research objectives or computation conditions of the studies.

Diastolic augmentation index (DAI), calculated from radial artery pressure waveform, has been associated with the risk of cardiovascular disease. In the present study, we aimed to evaluate whether DAI could be used as a predictor of arterial stiffness and the effect of heart rate (HR) on it. Measurements of anthropometric parameters, blood pressure (BP), Augmentation index (AI) and DAI were taken in 242 healthy subjects (130 men and 112 women; age 16–78 years). DAI and AI were measured in a subgroup of 16 subjects (10 men and 6 women; age 19–69 years) in a two-month follow-up study, which aimed to investigate the effect of HR changes. Statistically, DAI was higher in women compared to men (44.8% ± 7.7% compared with 43.6% ± 6.9%, P < 0.05). DAI was decreased with age (men: r = -0.755, P < 0.05; women: r = -0.708, P < 0.05) and negatively correlated to AI (men: r = -0.704, P < 0.05; women: r = -0.756, P < 0.05). There was no significant change in DAI when HR ranged from 60 to 80 bpm. Multiple regression analysis demonstrated fewer determinants affect DAI compared with AI. These findings indicate that the simple radial DAI might be used as an index to assess vascular aging.

Pulse wave velocity (PWV), based on two-site measurement, is a well-known predictor of arterial stiffness. Interest focused increasingly on simplifying the PWV measurement results in attempts at determining it at a single site. We aimed to validate a new tonometric method (IIM-2010A) for assessment of PWV at radial artery in healthy subjects <65 years of age. PWV measurements were performed in 46 healthy adults (25 men and 21 women) aged 21–65 years (39.6 ± 15.5 years) using Complior device and IIM-2010A respectively. In a subgroup of 21 humans, the measurements were repeated after 1 week using IIM-2010A with the same protocol. There was a strong correlation between PWV obtained by IIM-2010A and PWV obtained by Complior, as well as between pulse transit time (PTT) measurements (r = 0.79 and r = 0.85, respectively, P < 0.01 for both). Although PTT was significantly lower measured by IIM-2010A, no significant difference was found in PWV. The mean difference of PWV with SD was -0.1 ± 1.2 m/s between two repeated measurements at intervals of 1 week. Bland–Altman's plot indicated no trend for the reproducibility of measurements to vary with their underlying mean value. Intraclass correlation coefficient (= 0.87) confirmed this excellent week-to-week reproducibility of PWV. The method provides a simple, easily-obtainable, and reproducible measurement of PWV in young and middle-aged subjects, and has potential to detect premature arterial aging for the management of primary prevention.

Arterial stiffness is a major contributor to cardiovascular diseases. The aim of this study is to explore the physiological significance of the brachial mechanical parameters, which could be estimated from oscillometric blood pressure (BP) measurement, and investigate on the potential of these arterial parameters as an index of arterial stiffness. The mechanical characteristics of brachial artery were modeled based on the collapsible tube theory, which includes two important parameters to describe the compliance of brachial artery. After the model validation, the arterial parameters were estimated from the measured oscillometric envelope of 56 subjects by solving an inverse problem. The physiological significance of these parameters was explored by analyzing their association with pulse wave velocity (PWV) as well as with the BP. Arterial compliance parameters were successfully estimated from the envelope of the oscillometric pulse wave in the BP measurement. The parameters were found to be linearly associated with age, PWV, and BP. These results suggest that our method may provide a potential approach to assess arterial compliance based on oscillometric measurement of BP.

Arterial stiffness, resulting in loss of the elastic properties of arteries walls, is an indicator of cardiovascular risk, though the presence of disease is not clinically evident. Augmentation index is an important biomarker of arterial stiffness by which the cardiac risk of the patient can be diagnosed. The current paper outlines the non-invasive assessment of arterial stiffness by analyzing the morphology or contour of PhotoPlethysmoGraph (PPG) signal. PPG pulse was optically acquired with the developed photometric measurement device and the desired features were extracted to determine PPG augmentation Index (PAI) through advanced signal processing implemented in MATLAB. PAI was quantified by the fourth derivative of the signal by enhancing the location of inflection point (augmentation point) after conditioning the signal by efficient pre-processing and filtering techniques. The results reveal that the statistical distribution of PAI for healthy subjects presents a very low value and a very tight distribution. On the contrary, patients have a higher value of PAI and a wide asymmetrical shape of distribution. This work also establishes the usefulness of PPG contour analysis in the investigation of changes in the elastic properties of the vascular system. In conclusion, PAI has revealed to be a non-invasive indicator for arterial stiffness assessments.

There is a need for new methods to measure the level of arterial stiffness easily at home. A previous report investigating the effect of measurement position on brachial–ankle pulse wave velocity (baPWV) showed that baPWV was higher in the sitting position than in the supine position. This was probably because the increased ankle PWV was associated with increased hydrostatic pressure in the arteries of lower extremities. Therefore, we investigated the effect of measurement position on the cardio-ankle vascular index (CAVI), which is hardly affected by blood pressure. CAVI was measured in 50 healthy males (20–74 years) in five positions: supine, sitting, sitting with the knees flexed at 0${}^{\circ }$, reclining 50${}^{\circ }$, and standing. Compared to other positions, CAVI in the supine position was the lowest ($P<0.01$); $t_{\mathrm{\text{b}}}$ (the time difference between the second heart sound and the notch of the pulse wave in the upper arm) in the supine position was the highest ($P<0.01$); and $t_{\mathrm{\text{ba}}}$ (the time difference between the minimum upper arm and ankle pulse wave pattern values) in the supine position was the highest ($P<0.01$). Thus, our results indicated that changes in measurement position reduced pulse arrival time (increasing pulse wave velocity). We also observed a good correlation between CAVI in the supine position and that in other positions. The present study showed that the measurement position affected CAVI as much as it affected baPWV. Accordingly, correcting for the measurement position would be required when the position differs from supine.

The reflected wave of Photoplethysmography (PPG) is generated due to impedance mismatch, when the pulse wave propagates along the arterial branches. The objective of the study is to estimate the reflected wave amplitude and duration from PPG and to determine whether it changes with age. Reflected wave of PPG was modeled using the lognormal model fitting method. The duration and amplitude of reflected wave and augmentation index from modeled PPG was compared with the Slope Sum Function (SSF) and second derivative of PPG. PPG was collected from 120 subjects with age $<$40 and $>$40 years old for carrying out this experiment. Reflected wave duration from modeled PPG and SSF method shows a mean square error value of $0.63\pm 0.29$ and $0.94\pm 0.8$ for subjects $<$40 and $>$40 years age, respectively. The amplitude of reflected wave from PPG model and Second Derivative of Photolethysmography (SDPPG) results in a mean square error of $2.31\pm 2.08$ and $2.32\pm 0.36$ for subjects $<$40 and $>$40 years age, respectively. Augmentation index calculated from PPG model and SDPPG was similar with good level of agreement in the scatter plot. The modeled PPG helps to identify the reflected wave parameter noninvasively and the results show a considerable variation in these parameters with age.