An-Bang Liu

Arterial Stiffness Using Radial Arterial Waveforms Measured at the Wrist as an Indicator of Diabetic Control in the Elderly

Although current technique of photoplethysmography (PPG) is a popular noninvasive method of waveform contour analysis in assessing arterial stiffness, data obtained are frequently affected by various environmental and physiological factors. We proposed an easily operable air pressure sensing system (APSS) for radial arterial signal capturing. Totally, 108 subjects (young, the aged with or without diabetes) were recruited from July 2009 to May 2010. Arterial waveform signals from the wrist were obtained and analyzed using Hilbert-Huang transformation (HHT). Through ensemble empirical mode decomposition (EEMD), the signals were decomposed into eight intrinsic mode functions (IMF1-8) of which IMF5 was found to be the desired signal with a discernible diastolic peak. The results showed significant differences in reflection index (RI) and stiffness index (SI) from the young subjects and those from the aged participants with or without diabetes. Significant differences in RI and SI were also noted between subjects with well-controlled diabetes and those without. Good reproducibility and correlation were demonstrated. In conclusion, the present study proposed the application of radial arterial signal capturing subsystem and HHT in acquiring more reliable data on RI and SI compared with the conventional PPG method.

Multiscale Entropy Analysis of Pulse Wave Velocity for Assessing Atherosclerosis in the Aged and Diabetic

This study proposed a dynamic pulse wave velocity (PWV)-based biomedical parameter in assessing the degree of atherosclerosis for the aged and diabetic populations. Totally, 91 subjects were recruited from a single medical institution between July 2009 and October 2010. The subjects were divided into four groups: young healthy adults (Group 1, n = 22), healthy upper middle-aged adults (Group 2, n = 28), type 2 diabetics with satisfactory blood sugar control (Group 3, n = 21), and unsatisfactory blood sugar control (Group 4, n = 20). A self-developed six-channel electrocardiography (ECG)-PWV-based equipment was used to acquire 1000 successive recordings of PWVfoot values within 30 min. The data, thus, obtained were analyzed with multiscale entropy (MSE). Large-scale MSE index (MEILS) was chosen as the assessment parameter. Not only did MEILS successfully differentiate between subjects in Groups 1 and 2, but it also showed a significant difference between Groups 3 and 4. Compared with the conventional parameter of PWVfoot and MEI on R-R interval [i.e., MEI (RRI)] in evaluating the degree of atherosclerotic change, the dynamic parameter, MEILS (PWV), could better reflect the impact of age and blood sugar control on the progression of atherosclerosis.

Novel application of parameters in waveform contour analysis for assessing arterial stiffness in aged and atherosclerotic subjects

OBJECTIVE Although contour analysis of pulse waves has been proposed as a non-invasive means in assessing arterial stiffness in atherosclerosis, accurate determination of the conventional parameters is usually precluded by distorted waveforms in the aged and atherosclerotic objects. We aimed at testing reliable indices in these patient populations. METHODS Digital volume pulse (DVP) curve was obtained from 428 subjects recruited from a health screening program at a single medical center from January 2007 to July 2008. Demographic data, blood pressure, and conventional parameters for contour analysis including pulse wave velocity (PWV), crest time (CT), stiffness index (SI), and reflection index (RI) were recorded. Two indices including normalized crest time (NCT) and crest time ratio (CTR) were also analysed and compared with the known parameters. RESULTS Though ambiguity of dicrotic notch precluded an accurate determination of the two key conventional parameters for assessing arterial stiffness (i.e. SI and RI), NCT and CTR were unaffected because the sum of CT and T(DVP) (i.e. the duration between the systolic and diastolic peak) tended to remain constant. NCT and CTR also correlated significantly with age, systolic and diastolic blood pressure, PWV, SI and RI (all P<0.01). CONCLUSION NCT and CTR not only showed significant positive correlations with the conventional parameters for assessment of atherosclerosis (i.e. SI, RI, and PWV), but they also are of particular value in assessing degree of arterial stiffness in subjects with indiscernible peak of diastolic wave that precludes the use of conventional parameters in waveform contour analysis.

Application of a Modified Entropy Computational Method in Assessing the Complexity of Pulse Wave Velocity Signals in Healthy and Diabetic Subjects

Using 1000 successive points of a pulse wave velocity (PWV) series, we previously distinguished healthy from diabetic subjects with multi-scale entropy (MSE) using a scale factor of 10. One major limitation is the long time for data acquisition (i.e., 20 min). This study aimed at validating the sensitivity of a novel method, short time MSE (sMSE) that utilized a substantially smaller sample size (i.e., 600 consecutive points), in differentiating the complexity of PWV signals both in simulation and in human subjects that were divided into four groups: healthy young (Group 1; n = 24) and middle-aged (Group 2; n = 30) subjects without known cardiovascular disease and middle-aged individuals with well-controlled (Group 3; n = 18) and poorly-controlled (Group 4; n = 22) diabetes mellitus type 2. The results demonstrated that although conventional MSE could differentiate the subjects using 1000 consecutive PWV series points, sensitivity was lost using only 600 points. Simulation study revealed consistent results. By contrast, the novel sMSE method produced significant differences in entropy in both simulation and testing subjects. In conclusion, this study demonstrated that using a novel sMSE approach for PWV analysis, the time for data acquisition can be substantially reduced to that required for 600 cardiac cycles (~10 min) with remarkable preservation of sensitivity in differentiating among healthy, aged, and diabetic populations.

Six-channel ECG-based pulse wave velocity for assessing whole-body arterial stiffness

Abstract Background. Despite the proposal of different means of non-invasive arterial stiffness assessment, none offers simultaneous information on whole-body peripheral arterial condition. We investigated the validity of applying a six-channel electrocardiogram-based pulse wave velocity (ECG-PWV) measurement system for this purpose. Methods. The study consisted of two parts. Part One enrolled hypertensive (Group 1, n = 32) and normal (Group 2, n = 32) subjects, whereas Part Two recruited diabetic (Group 3, n = 50) and normal (Group 4, n = 50) subjects. To validate the application of ECG-PWV in assessing peripheral arterial stiffness in different parts of body, ECG-PWV data were compared with three other parameters including the cardio-ankle vascular index (CAVI), pulse wave velocity–digital volume pulse (PWV-DVP) and intima-media thickness (IMT). Results. ECG-PWV in healthy subjects in Part One correlated significantly with CAVI and PWV-DVP (p < 0.05), whereas ECG-PWV and CAVI were significantly different between the hypertensive and normal subjects. Moreover, comparison of IMT and ECG-PWV from different sites showed significant correlation only between IMT and ECG-PWV from earlobe (r = 0.495, p = 0.004). No significant association, however, was noted between IMT and CAVI. For Part Two, significant differences existed between diabetic and normal subjects in body weight, waist circumference, level of HbA1c, fasting blood sugar, serum creatinine and ECG-PWV from the foot. However, no significant difference was noted in PWV-DVP between two groups. Conclusions. Six-channel ECG-PWV measurement system showed remarkable correlation with IMT in hypertensive subjects and with key anthropometric and biochemical parameters in diabetic patients, suggesting its validity in assessing whole-body arterial stiffness in subjects with peripheral arterial diseases within 10 min.

Assessment of autonomic dysfunction in patients with type 2 diabetes using reactive hyperemia

It is known that aging and type 2 diabetes mellitus contribute to atherosclerosis and autonomic dysfunction. By using the air pressure sensing system (APSS), peak-peak intervals (PPIs) of wrist arterial waveforms from baseline and reactive hyperemia (RH) were obtained. Through frequency domain analysis of heart rate variability (HRV) and nonlinear Poincaré method, the HRV of healthy young individuals (Group 1, n=25), healthy upper middle-aged individuals (Group 2, n=22), and patients with type 2 diabetes (Group 3, n=28) were assessed. By using the standard deviation (SD) of the instantaneous PPI variability (SD1)/the SD of the long PPI variability (SD2) ratio (SSR), PPIs of the same individuals before and after RH induction were compared. Reduced SSR₁₋₁₀ was noted only in patients with diabetes. Moreover, a significient correlation between SSR₁₋₁₀ and endothelial function was observed in all subjects (r=0.290, p=0.033) after RH. However, no correlation with low-frequency to high-frequency power ratio (LHR) was noted before and after RH. In conclusion, according to our results, campared to the baseline, there were more significant changes of SSR₁₋₁₀ after RH in patients with diabetes; and, a significient correlation between SSR₁₋₁₀ and endothelial function at the moment of RH was noted.

Endothelium function assessment with radial pulse wave signals

This study proposes a method of measuring vasodilatation via air pressure sensing to assess the function of endothelium cells. The vasodilatation index is calculated according to the change of area of waveform caused by stimulation to the blood vessels, and uses this index to reflect the function of endothelium cells; therefore, early self-monitoring of cardiovascular dysfunction and arterial stiffness can be easily and effectively achieved. Only a few minutes are needed for conducting a self endothelial function assessment. Furthermore, this study improves the high cost pressure sensors used in Reactive Hyperemia Peripheral Arterial Tonometry (RH-PAT) and its inconveniences. 30 test subjects with no previous cardiovascular disease record were included for testing the reproducibility of the instrument. It has been proven that the air pressure sensing method proposed in this study has higher reproducibility and practicality than the Photoplethysmography (PPG) system for assessing the function of endothelium cells.

Digital Pulse Volume Based Endothelial Function Detector for Early Stage Formation of Atherosclerosis

In this paper, we discuss the development of an easy-to-use non-intrusive endothelial function assessment instrument. The instrument records the digital pulse volume (DPV) from the fingers. We studied 42 subjects (28 men and 14 women, 22 to 64 years of age) and showed the good performance of self-developed system for monitoring endothelial function. The system is capable to apply both area under the curve of DPV and traditional amplitude methods for endothelial function assessment. Both methods are highly correlated as well as able to reflect the changes of blood flow volume in reactive hyperemia. At home, only a few minutes are needed for conducting a self endothelial function assessment. Therefore, early self-monitoring of cardiovascular dysfunction and arterial stiffness can be easily and effectively achieved.

Difference in bilateral digital volume pulse as a novel non-invasive approach to assessing arteriosclerosis in aged and diabetic subjects: A preliminary study

Objective: This study aimed at validating photoplethysmography for assessing bilateral blood pressure differences through investigating the correlations of digital volume pulse with arteriosclerosis risk. Methods: Totally, 111 subjects (70 healthy and 41 diabetic) were recruited. Demographic, blood pressure and anthropometric data were recorded. Blood was collected for determining serum cholesterol, total triglyceride, total cholesterol, high-/low-density lipoprotein cholesterol, fasting blood sugar and glycated haemoglobin concentrations. Arterial stiffness was assessed with electrocardiogram-based pulse wave velocity, crest time and inter-digital volume pulse differences. Results: Receiver operating characteristic curve demonstrated high inter-digital volume pulse difference sensitivity to glycated haemoglobin level over 6.5%. Linear regression analysis demonstrated significant correlation between inter-digital volume pulse difference and electrocardiogram-based pulse wave velocity (r = 0.692, p < 0.001). Compared with electrocardiogram-based pulse wave velocity, inter-digital volume pulse difference exhibited highly significant correlations with age, glycated haemoglobin level, pulse pressure, total cholesterol/high-density lipoprotein ratio, crest time, high-density lipoprotein and systolic blood pressure (all ps < 0.001). Conclusion: In conclusion, the results not only demonstrated successful application of a novel non-invasive waveform contour index, inter-digital volume pulse difference, in differentiating young from aged subjects and patients with good diabetic control from those with poor diabetic control but also validated its use in identifying arteriosclerosis risks. The results, therefore, endorse its domestic application as non-invasive tool for arteriosclerosis risk screening.

Simultaneous assessment of autonomic nervous and vascular endothelial functions in a rat model.

Abstract Despite the importance of translational medicine in cardiovascular research, rat vascular endothelial function and sympathetic activity assessment remains challenging. This study consisted of two parts: part A examined the consistency of reactive hyperemia-elicited dilatation index (DI) before (DIOriginal) and after (DIEEMD) ensemble empirical mode decomposition (EEMD) using Wistar-Kyoto (WKY) rats (n=7). Part B compared the endothelial function and heart rate variability of normal WKY rats (group 1, n=9) with those of spontaneously hypertensive rats (group 2, n=9) at two time points of development. The SD1/SD2 ratio (SSR) was obtained from Poincaré plot analysis to evaluate sympathetic activities. Using a Bland-Altman plot, part A of the study demonstrated a lower agreement of DIOriginal than that of DIEEMD. In part B, despite no significant difference in DIEEMD between the two groups at age 10 weeks, DIEEMD was higher in group 1 (2.25±0.63 vs. 1.43±0.41 for groups 1 and 2, respectively, p=0.004) at 20 weeks. Although no notable change in SSR existed in group 1 between the two time points, a significant difference existed in group 2 (p<0.001). In conclusion, using algorithms of Poincaré plot analysis and EEMD, the impact of age and hypertension on rat vascular endothelial function and heart rate variability can be reliably assessed.