Estimation of wave reflection in aorta from radial pulse waveform by artificial neural network: a numerical study

BACKGROUND AND OBJECTIVE

Wave reflection in aorta has been shown to have incremental value for predicting cardiovascular events. However, its estimation by wave separation analysis (WSA) is complex.

METHODS

In this study, a novel method was proposed based on a cascade artificial neural network (ANN) for wave reflection estimation by the frequency features of radial pressure waveform alone. The simulation database of 4000 samples was generated by a 55-segment transmission line model of human arterial tree and was used for evaluating the ANN with 10-fold cross validation for the estimation of reflection magnitude (RM_ANN) and reflection index (RI_ANN) of wave reflection in aorta. RM and RI also were estimated by the WSA with a triangle waveform of aortic flow (RM_WSA and RI_WSA) and with a real aortic flow waveform (RM_Ref and RI_Ref) as reference values.

RESULTS

The results showed the correlation coefficient and mean difference between RM_ANN and RM_Ref (R² = 0.92, mean ± standard deviation (SD) = 0.0 ± 0.02) and those between RI_ANN and RI_Ref (R² = 0.91, mean ± SD = 0.0 ± 0.01) were better than those between RM_WSA and RM_Ref (R² = 0.51, mean ± SD = 0.01 ± 0.07) and those between RI_WSA and RI_Ref (R² = 0.50, mean ± SD = 0.0 ± 0.02). As the sample diversity in the simulation database was increased but the total number of samples keeps constant, the advantage of the ANN, though decreased slightly, became more significant than those of WSA (RM_ANN VS. RM_Ref and RI_ANN VS. RI_Ref: R² = 0.88 and 0.88, mean ± SD = 0.0 ± 0.05 and 0.0 ± 0.05; RM_WSA VS. RM_Ref and RI_WSA VS. RI_Ref: R² = 0.24 and 0.24, mean ± SD = 0.07 ± 0.24 and 0.02 ± 0.08, respectively). In addition, the ANN can achieve better results than the traditional method WSA even only two hidden neurons are used.

CONCLUSIONS

ANN is a potential method for the estimation of wave reflection in aorta by a single radial pulse waveform, but further validation of this method in clinic trials is needed.

Evaluation of the effects of a standardized aqueous extract of Phyllanthus emblica fruits on endothelial dysfunction, oxidative stress, systemic inflammation and lipid profile in subjects with metabolic syndrome: a randomised, double blind, placebo controlled clinical study

BACKGROUND

Endothelial dysfunction (ED) has been observed in individuals with metabolic syndrome (MetS) and contributes to the initiation and progression of atherosclerosis. The primary management of MetS involves lifestyle modifications and treatment of its individual components with drugs all of which have side effects. Thus, it would be of advantageous if natural products would be used as adjuncts or substitutes for conventional drugs. The aim of the present study was to evaluate the effect of standardized aqueous extract of fruits of Phyllanthus emblica (P. emblica) 250 mg and 500 mg twice daily on ED, oxidative stress, systemic inflammation and lipid profile in subjects with MetS.

METHODS

In this randomised, double-blind, placebo-controlled clinical study endothelial function was measured by calculating reflection index (RI) using digital plethysmograph. Oxidative stress biomarkers used were nitric oxide (NO), glutathione (GSH) and malondialdehyde (MDA). Systemic inflammation was measured by determining high sensitivity C-reactive protein (hsCRP) and dyslipidemia by lipid profile. ANOVA, paired and unpaired t-test were used. P-value < 0.05 was considered statistically significant.

RESULTS

Out of 65 screened subjects all 59 enrolled completed the study. P. emblica aqueous extract (PEE), 250 mg and 500 mg twice daily dosing, showed significant reduction in mean RI, measure of endothelial function, at 8 and 12 weeks (p <  0.001) compared to baseline and placebo. Significant mean % change was seen in oxidative stress biomarkers, NO (+ 41.89%, + 50.7%), GSH (+ 24.31%, + 53.22%) and MDA (- 21.02%, - 31.44%), and systemic inflammation biomarker, hsCRP (- 39.68%, - 53.77%) (p <  0.001) at 12 weeks with 250 mg and 500 mg twice daily dosage respectively. Significant mean % change was also seen at 12 weeks with TC (- 7.71%, - 11.11%), HDL-C (+ 7.33% + 22.16%, p <  0.05), LDL-C (- 11.39%, - 21.8%) and TG (- 9.81%, - 19.22%) respectively with 250 mg and 500 mg twice daily (p <  0.001). PEE 500 mg twice daily was significantly more efficacious than the 250 mg twice daily and placebo. No participant discontinued the study because of adverse events.

CONCLUSIONS

P.emblica aqueous extract significantly improved endothelial function, oxidative stress, systemic inflammation and lipid profile at both dosages tested, but especially at 500 mg twice daily. Thus, this product may be used as an adjunct to conventional therapy (lifestyle modification and pharmacological intervention) in the management of metabolic syndrome.

TRIAL REGISTRATION

This study was registered with Clinical Trials Registry - India (CTRI) with the registration number of CTRI/2017/09/009606 . The study was registered retrospectively on 4th September 2017.

Significance of arterial stiffness in Tridosha analysis: A pilot study

Background

The variations in Tridoshas are the basis for disease diagnosis and treatment in Ayurveda. The doshas are assessed by sensing the pulse manually with fingers which depends on skill of the physician. There is a need to measure doshas using instruments and study them objectively.

Objective

Arterial stiffness is well established pulse parameter in modern medicine and is closely associated to kathinya in the context of Ayurveda. The aim of our study was to measure arterial stiffness using Nadi Tarangini, a pulse acquisition system, and investigate the significant variations of stiffness across Tridosha locations.

Materials and methods

A total of 42 samples of vata, pitta and kapha pulses with proper systolic and diastolic peaks were included in the study. The arterial stiffness parameters namely stiffness index (SI) and reflection index (RI) were considered for the study. The data was analyzed using one-way ANOVA followed by Tamhane's T2 test. The changes in SI and RI between males and females were assessed using independent samples t test.

Results

SI at vata (5.669 ± 1.165) was significantly low compared to pitta (8.910 ± 3.509) and kapha (8.021 ± 2.814); RI at vata (0.846 ± 0.071) was significantly low compared to pitta (0.945 ± 0.043) and kapha (0.952 ± 0.033). SI at kapha was significantly low in females compared to males.

Conclusion

The SI and RI acquired using Nadi Tarangini have shown significant variations across Tridosha locations. The framework developed to measure the arterial stiffness across Tridosha locations can be used for the interventional studies in Ayurveda which in turn can help in disease diagnosis and treatment.

Correlation of Adiposity Indices with Electrocardiographic Ventricular Variables and Vascular Stiffness in Young Adults

INTRODUCTION

Excess adiposity constitute an important public health problem because of the associated increased risk of hypertension, coronary heart disease, type 2 diabetes and other disorders. Not only the contribution of general measures of adiposity but also central measures of adiposity have been observed.

AIM

To compare and correlate the central and general adiposity indices with ventricular electrocardiographic variables and vascular stiffness indices in normal, overweight and obese young adults.

MATERIALS AND METHODS

This was a cross-sectional study. Nearly ninety subjects were enrolled and were divided into 30 normal weight, 30 overweight and 30 obese group based on the BMI classification of WHO for Asian population with their age ranging from 18-25 years. Waist and hip circumferences were measured using stretchable tape. Two novel indices-conicity index and abdominal volume index were calculated using standard formula. ECG and pulse wave were recorded using the Physiopac - Medicaid systems. Statistical analysis was done using SPSS version 19.0 software. ANOVA test was done to compare the variables among three groups. Pearson's correlation coefficients were applied to establish the correlations between variables.

RESULTS

In our study Body Mass Index (BMI) and Conicity Index (CI) was significantly and strongly correlated with the ventricular electrocardiographic variables especially with QRS duration, QTc interval and with vascular stiffness indices. These indices can be used to assess the electrocardiographic abnormalities and vascular stiffness status.

CONCLUSION

Excess adipose tissue in young adults was closely linked to ventricular depolarization and repolarization abnormalities and also to increased vascular stiffness. Adiposity indices in particular (BMI, CI) provide a simple and non invasive approach to assess these abnormalities at the earliest in order to prevent future complications.

Investigation of peripheral photoplethysmographic morphology changes induced during a hand-elevation study

A hand-elevation study was carried out in the laboratory in order to alter peripheral blood flow with the aim of increasing understanding of factors affecting the morphology of peripheral photoplethysmographic signals. Photoplethysmographic (PPG) signals were recorded from twenty healthy volunteer subjects during a hand-elevation study in which the right hand was raised and lowered relative to heart level, while the left hand remained static. Red and infrared (IR) PPG signals were obtained from the right and left index fingers using a custom-made PPG processing system. PPG features were identified using a feature-detection algorithm based on the first derivative of the PPG signal. The systolic PPG amplitude, the reflection index, crest time, pulse width at half height, and delta T were calculated from 20 s IR PPG signals from three positions of the right hand with respect to heart level (-50, 0, +50 cm) in 19 volunteers. PPG features were found to change with hand elevation. On lowering the hand to 50 cm below heart level, ac systolic PPG amplitudes from the finger decreased by 68.32 %, while raising the arm increased the systolic amplitude by 69.99 %. These changes in amplitude were attributed to changes in hydrostatic pressure and the veno-arterial reflex. Other morphological variables, such as crest time, were found to be statistically significantly different across hand positions, indicating increased vascular resistance on arm elevation than on dependency. It was hypothesized that these morphological PPG changes were influenced by changes in downstream venous resistance, rather than arterial, or arteriolar, resistance. Changes in hand position relative to heart level can significantly affect the morphology of the peripheral ac PPG waveform. These alterations are due to a combination of physical effects and physiological responses to changes in hand position, which alter vascular resistance. Care should be taken when interpreting morphological data derived from PPG signals and methods should be standardized to take these effects into account.

Assessment of vascular function in individuals with hyperglycemia: a cross-sectional study of glucose - induced changes in digital volume pulse

Background

Arterial stiffness is an independent risk factor for cardiovascular disease and its progression may be accelerated in the presence of hyperglycemia, either fasting or postprandial. The current study assessed vascular function in subjects with pre-diabetes hyperglycemia, using digital volume pulse analysis technique.

Methods

We conducted a cross-sectional study examining vascular function in the fasting and postprandial (glucose-induced) state in 44 adults, consisting of 17 subjects with pre-diabetic hyperglycemia and 27 normoglycemic volunteers. Photoplethysmography of the digital volume pulse (DVP) was used to determine stiffness index (SI) and reflective index (RI), as main measures of larger artery stiffness and vascular tone, respectively.

Results

Our results showed a significantly higher (Ln) fasting SI in the hyperglycemic group compared with the control group (2.19 ± 0.32 vs. 1.96 ± 0.22, P = 0.005). However, this pattern reversed after adjustment for potential confounders. In multiple linear regression analysis, (Ln) SI was related to age (β = 0.01, 95% CI: 0.01-0.02, P < 0.001) and systolic blood pressure (SBP) (β = 0.01, 95% CI: 0.00-0.01, P < 0.05), but not with W/H, diastolic blood pressure (DBP), fasting plasma glucose (FPG) or serum lipids. Furthermore, age (β = 0.02, 95% CI: 0.01-0.03, P < 0.001) and mean arterial pressure (MAP) (β = 0.01, 95% CI: 0.00-0.02, P < 0.05) were found as the strong predictors of fasting SI in hyperglycemic group. Neither FPG nor 2-h plasma glucose was a significant predictor for SI in hyperglycemic group, after accounting for age and MAP. Subjects with hyperglycemia had a 15% blunted change in postprandial AUCs for RI, adjusted for the respective baseline measurements (−9.40 ± 3.59 vs. -11.00 ± 2.84%) but these did not attain statistical significance.

Conclusion

Increased arterial stiffness in pre-diabetic subjects is strongly associated with age and MAP. The increased DVP-derived SI reported in patients with pre-diabetic hyperglycemia may result from different frequently accompanied risk factors not just glycemic changes in this range.