Photoplethysmographic assessment of pulse wave reflection: blunted response to endothelium-dependent beta2-adrenergic vasodilation in type II diabetes mellitus

Predicting Arterial Stiffness From Single-Channel Photoplethysmography Signal: A Feature Interaction-Based Approach

Arterial stiffness (AS) serves as a crucial indicator of arterial elasticity and function, typically requiring expensive equipment for detection. Given the strong correlation between AS and various photoplethysmography (PPG) features, PPG emerges as a convenient method for assessing AS. However, the limitations of independent PPG features hinder detection accuracy. This study introduces a feature selection method leveraging the interactive relationships between features to enhance the accuracy of predicting AS from a single-channel PPG signal. Initially, an adaptive signal interception method was employed to capture high-quality signal fragments from PPG sequences. 58 PPG features, deemed to have potential contributions to AS estimation, were extracted and analyzed. Subsequently, the interaction factor (IF) was introduced to redefine the interaction and redundancy between features. A feature selection algorithm (IFFS) based on the IF was then proposed, resulting in a combination of interactive features. Finally, the Xgboost model is utilized to estimate AS from the selected features set. The proposed approach is evaluated on datasets of 268 male and 124 female subjects, respectively. The results of AS estimation indicate that IFFS yields interacting features from numerous sources, rejects redundant ones, and enhances the association. The interaction features combined with the Xgboost model resulted in an MAE of 122.42 and 142.12 cm/sec, an SDE of 88.16 and 102.56 cm/sec, and a PCC of 0.88 and 0.85 for the male and female groups, respectively. The findings of this study suggest that the stated method improves the accuracy of predicting AS from single-channel PPG, which can be used as a non-invasive and cost-effective screening tool for atherosclerosis.

pyPPG: a Python toolbox for comprehensive photoplethysmography signal analysis

Objective.Photoplethysmography is a non-invasive optical technique that measures changes in blood volume within tissues. It is commonly and being increasingly used for a variety of research and clinical applications to assess vascular dynamics and physiological parameters. Yet, contrary to heart rate variability measures, a field which has seen the development of stable standards and advanced toolboxes and software, no such standards and limited open tools exist for continuous photoplethysmogram (PPG) analysis. Consequently, the primary objective of this research was to identify, standardize, implement and validate key digital PPG biomarkers.Approach.This work describes the creation of a standard Python toolbox, denotedpyPPG, for long-term continuous PPG time-series analysis and demonstrates the detection and computation of a high number of fiducial points and digital biomarkers using a standard fingerbased transmission pulse oximeter.Main results.The improved PPG peak detector had an F1-score of 88.19% for the state-of-the-art benchmark when evaluated on 2054 adult polysomnography recordings totaling over 91 million reference beats. The algorithm outperformed the open-source original Matlab implementation by ∼5% when benchmarked on a subset of 100 randomly selected MESA recordings. More than 3000 fiducial points were manually annotated by two annotators in order to validate the fiducial points detector. The detector consistently demonstrated high performance, with a mean absolute error of less than 10 ms for all fiducial points.Significance.Based on these fiducial points,pyPPGengineered a set of 74 PPG biomarkers. Studying PPG time-series variability usingpyPPGcan enhance our understanding of the manifestations and etiology of diseases. This toolbox can also be used for biomarker engineering in training data-driven models.pyPPGis available onhttps://physiozoo.com/.

Insights into vascular physiology from sleep photoplethysmography

STUDY OBJECTIVES

Photoplethysmography (PPG) in consumer sleep trackers is now widely available and used to assess heart rate variability (HRV) for sleep staging. However, PPG waveform changes during sleep can also inform about vascular elasticity in healthy persons who constitute a majority of users. To assess its potential value, we traced the evolution of PPG pulse waveform during sleep alongside measurements of HRV and blood pressure (BP).

METHODS

Seventy-eight healthy adults (50% male, median [IQR range] age: 29.5 [23.0, 43.8]) underwent overnight polysomnography (PSG) with fingertip PPG, ambulatory blood pressure monitoring, and electrocardiography (ECG). Selected PPG features that reflect arterial stiffness: systolic to diastolic distance (∆T_norm), normalized rising slope (Rslope) and normalized reflection index (RI) were derived using a custom-built algorithm. Pulse arrival time (PAT) was calculated using ECG and PPG signals. The effect of sleep stage on these measures of arterial elasticity and how this pattern of sleep stage evolution differed with participant age were investigated.

RESULTS

BP, heart rate (HR) and PAT were reduced with deeper non-REM sleep but these changes were unaffected by the age range tested. After adjusting for lowered HR, ∆T_norm, Rslope, and RI showed significant effects of sleep stage, whereby deeper sleep was associated with lower arterial stiffness. Age was significantly correlated with the amount of sleep-related change in ∆T_norm, Rslope, and RI, and remained a significant predictor of RI after adjustment for sex, body mass index, office BP, and sleep efficiency.

CONCLUSIONS

The current findings indicate that the magnitude of sleep-related change in PPG waveform can provide useful information about vascular elasticity and age effects on this in healthy adults.

Nocturnal Blood Pressure Estimation from Sleep Plethysmography Using Machine Learning

BACKGROUND

Elevated nocturnal blood pressure (BP) is a risk factor for cardiovascular disease (CVD) and mortality. Cuffless BP assessment aided by machine learning could be a desirable alternative to traditional cuff-based methods for monitoring BP during sleep. We describe a machine-learning-based algorithm for predicting nocturnal BP using single-channel fingertip plethysmography (PPG) in healthy adults.

METHODS

Sixty-eight healthy adults with no apparent sleep or CVD (53% male), with a median (IQR) age of 29 (23-46 years), underwent overnight polysomnography (PSG) with fingertip PPG and ambulatory blood pressure monitoring (ABPM). Features based on pulse morphology were extracted from the PPG waveforms. Random forest models were used to predict night-time systolic blood pressure (SBP) and diastolic blood pressure (DBP).

RESULTS

Our model achieved the highest out-of-sample performance with a window length of 7 s across window lengths explored (60 s, 30 s, 15 s, 7 s, and 3 s). The mean absolute error (MAE ± STD) was 5.72 ± 4.51 mmHg for SBP and 4.52 ± 3.60 mmHg for DBP. Similarly, the root mean square error (RMSE ± STD) was 6.47 ± 1.88 mmHg for SBP and 4.62 ± 1.17 mmHg for DBP. The mean correlation coefficient between measured and predicted values was 0.87 for SBP and 0.86 for DBP. Based on Shapley additive explanation (SHAP) values, the most important PPG waveform feature was the stiffness index, a marker that reflects the change in arterial stiffness.

CONCLUSION

Our results highlight the potential of machine learning-based nocturnal BP prediction using single-channel fingertip PPG in healthy adults. The accuracy of the predictions demonstrated that our cuffless method was able to capture the dynamic and complex relationship between PPG waveform characteristics and BP during sleep, which may provide a scalable, convenient, economical, and non-invasive means to continuously monitor blood pressure.

Stretchable Photodiodes with Polymer-Engineered Semiconductor Nanowires for Wearable Photoplethysmography

Healthcare systems worldwide have been stressed to provide sufficient resources to serve the increasing and aging population in our society. The situation became more challenging at the time of pandemic. Technology advancement, especially the adoption of wearable health monitoring devices, has provided an important supplement to current clinical equipment. Most health monitoring devices are rigid, however, human tissues are soft. Such a difference has prohibited intimate contact between the two and jeopardized wearing comfortableness, which hurdles measurement accuracy especially during longtime usage. Here, we report a soft and stretchable photodiode that can conformally adhere onto the human body without any pressure and measure cardiovascular variables for an extended period with higher reliability than commercial devices. The photodiode used a composite light absorber consisting of an organic bulk heterojunction embedded into an elastic polymer matrix. It is discovered that the elastic polymer matrix not only improves the morphology of the bulk heterojunction for obtaining the desired mechanical properties but also alters its electronic band structure and improves the electrical properties that lead to a reduced dark current and enhanced photovoltage in the stretchable photodiode. The work has demonstrated high fidelity measurements and longtime monitoring of heat rate variability and oxygen saturation, potentially enabling next-generation wearable photoplethysmography devices for point-of-care diagnosis of cardiovascular diseases in a more accessible and affordable way.

Impaired β 2 -adrenergic endothelium-dependent vasodilation in patients previously hospitalized with coronavirus disease 2019

AIM

The pulse wave response to salbutamol (PWRS) - change in augmentation index (AIx) - provides a means to assess endothelial vasodilator function in vivo . Endothelial dysfunction plays a relevant role in the pathogenesis of hypertension and cardiovascular disease and appears to underlie many of the complications of coronavirus disease 2019 (COVID-19). However, to what degree this persists after recovery is unknown.

METHODS

Individuals previously hospitalized with COVID-19, those recovered from mild symptoms and seronegative controls with well known risk factors for endothelial dysfunction were studied. To assess the involvement of nitric oxide-cyclic guanosine monophosphate pathway (NO-cGMP) on PWRS, sildenafil was also administrated in a subsample.

RESULTS

One hundred and one participants (60 men) aged 47.8 ± 14.1 (mean ± SD) years of whom 33 were previously hospitalized with COVID-19 were recruited. Salbutamol had minimal effect on haemodynamics including blood pressure and heart rate. It reduced AIx in controls ( n  = 34) and those recovered from mild symptoms of COVID-19 ( n  = 34) but produced an increase in AIx in those previously hospitalized: mean change [95% confidence interval] -2.85 [-5.52, -0.188] %, -2.32 [-5.17,0.54] %, and 3.03 [0.06, 6.00] % for controls, those recovered from mild symptoms and those previously hospitalized, respectively ( P  = 0.001). In a sub-sample ( n  = 22), sildenafil enhanced PWRS (change in AIx 0.05 [-2.15,2.24] vs. -3.96 [-7.01. -2.18], P  = 0.006) with no significant difference between hospitalized ( n  = 12) and nonhospitalized participants ( n  = 10).

CONCLUSIONS

In patients previously hospitalized with COVID-19, there is long-lasting impairment of endothelial function as measured by the salbutamol-induced stimulation of the NO-cGMP pathway that may contribute to cardiovascular complications.

Influence of Maternal Ethanol Exposure on Systemic Hemodynamic Variables and Histopathological Changes in the Aorta Wall of Male Rat Offspring: A Three-month Follow-up

Background

Alcohol consumption in pregnancy is associated with an increased risk of cardiovascular abnormalities, but the mechanisms are unknown. This study evaluated the impact of ethanol exposure on the offspring's aorta structural, functional, and molecular alterations on postnatal (PN) both on days 21 and 90.

Methods

This experimental study was conducted at Urmia University of Medical Sciences (Urmia, Iran) in 2019. Twenty Pregnant Wistar rats on the seventh day of Gestation Day (GD) were randomly divided into two groups: control and ethanol-treated groups (n=10 per group). From the seventh day of GD throughout lactation, rats in the ethanol group were fed binge alcohol (4.5 g/Kg body weight) once daily. Systemic hemodynamic variables in the offspring were analyzed using waveform contour analysis 90 days after birth. On postnatal days (PN) 21 and 90, aorta wall histological alterations and the level of inflammatory factors were assessed in the aorta of male offspring. The statistical differences were examined via an independent samples t test. P<0.05 was considered to be statistically significant.

Results

The results revealed that offspring in the ethanol group had higher systolic, diastolic, mean arterial pressure, and dicrotic pressure than the control group (P<0.001). The level of aorta tissue tumor necrosis factor (TNF)-α, intercellular adhesion molecule (ICAM)-1, nuclear factor (NF)-κ, and endothelin-1 were significantly higher in the ethanol offspring group than in the control group (P<0.001). Histopathological changes such as total aorta thickness, tunica media, tunica adventitia, elastin fiber thickness, fiber interval, and elastin/media ratio significantly increased in the aorta of the offspring of the ethanol group compared to the control group 21 and 90 days after birth.

Conclusion

Our findings suggest that prenatal and early postnatal ethanol exposure-induced cardiovascular abnormalities are, in part, due to predisposing the aorta to atherosclerosis, which was mediated through the aorta wall remodeling and inflammation process.

The Hybrid Excess and Decay (HED) model: an automated approach to characterising changes in the photoplethysmography pulse waveform

Photoplethysmography offers a widely used, convenient and non-invasive approach to monitoring basic indices of cardiovascular function, such as heart rate and blood oxygenation. Systematic analysis of the shape of the waveform generated by photoplethysmography might be useful to extract estimates of several physiological and psychological factors influencing the waveform. Here, we developed a robust and automated method for such a systematic analysis across individuals and across different physiological and psychological contexts. We describe a psychophysiologically-relevant model, the Hybrid Excess and Decay (HED) model, which characterises pulse wave morphology in terms of three underlying pressure waves and a decay function. We present the theoretical and practical basis for the model and demonstrate its performance when applied to a pharmacological dataset of 105 participants receiving intravenous administrations of the sympathomimetic drug isoproterenol (isoprenaline). We show that these parameters capture photoplethysmography data with a high degree of precision and, moreover, are sensitive to experimentally-induced changes in interoceptive arousal within individuals. We conclude by discussing the possible value in using the HED model as a complement to standard measures of photoplethysmography signals.

Diagnostic Features and Potential Applications of PPG Signal in Healthcare: A Systematic Review

Recent research indicates that Photoplethysmography (PPG) signals carry more information than oxygen saturation level (SpO2) and can be utilized for affordable, fast, and noninvasive healthcare applications. All these encourage the researchers to estimate its feasibility as an alternative to many expansive, time-wasting, and invasive methods. This systematic review discusses the current literature on diagnostic features of PPG signal and their applications that might present a potential venue to be adapted into many health and fitness aspects of human life. The research methodology is based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines 2020. To this aim, papers from 1981 to date are reviewed and categorized in terms of the healthcare application domain. Along with consolidated research areas, recent topics that are growing in popularity are also discovered. We also highlight the potential impact of using PPG signals on an individual’s quality of life and public health. The state-of-the-art studies suggest that in the years to come PPG wearables will become pervasive in many fields of medical practices, and the main domains include cardiology, respiratory, neurology, and fitness. Main operation challenges, including performance and robustness obstacles, are identified.

A Data-Driven Model with Feedback Calibration Embedded Blood Pressure Estimator Using Reflective Photoplethysmography

Ambulatory blood pressure (BP) monitoring (ABPM) is vital for screening cardiovascular activity. The American College of Cardiology/American Heart Association guideline for the prevention, detection, evaluation, and management of BP in adults recommends measuring BP outside the office setting using daytime ABPM. The recommendation to use night–day BP measurements to confirm hypertension is consistent with the recommendation of several other guidelines. In recent studies, ABPM was used to measure BP at regular intervals, and it reduces the effect of the environment on BP. Out-of-office measurements are highly recommended by almost all hypertension organizations. However, traditional ABPM devices based on the oscillometric technique usually interrupt sleep. For all-day ABPM purposes, a photoplethysmography (PPG)-based wrist-type device has been developed as a convenient tool. This optical, noninvasive device estimates BP using morphological characteristics from PPG waveforms. As measurement can be affected by multiple variables, calibration is necessary to ensure that the calculated BP values are accurate. However, few studies focused on adaptive calibration. A novel adaptive calibration model, which is data-driven and embedded in a wearable device, was proposed. The features from a 15 s PPG waveform and personal information were input for estimation of BP values and our data-driven calibration model. The model had a feedback calibration process using the exponential Gaussian process regression method to calibrate BP values and avoid inter- and intra-subject variability, ensuring accuracy in long-term ABPM. The estimation error of BP (ΔBP = actual BP—estimated BP) of systolic BP was −0.1776 ± 4.7361 mmHg; ≤15 mmHg, 99.225%, and of diastolic BP was −0.3846 ± 6.3688 mmHg; ≤15 mmHg, 98.191%. The success rate was improved, and the results corresponded to the Association for the Advancement of Medical Instrumentation standard and British Hypertension Society Grading criteria for medical regulation. Using machine learning with a feedback calibration model could be used to assess ABPM for clinical purposes.

Theoretical and Experimental Study on Assessment of Flow-Mediated Dilatation Using the Cuff Method in Brachial Arteries

Endothelial dysfunction has been shown to be an important risk factor in the pathogenesis of atherosclerosis, hypertension, and heart failure. The flow-mediated vasodilation (FMD) of the peripheral arteries is an endothelium-dependent function, which is assessed by measuring the diameter change in the brachial artery before and after ischemic stress. Brachial-artery ultrasound scanning (BAUS) is the gold standard for assessing the FMD in clinical practice. However, ultrasonography requires an operator or physician with a professional training to perform accurate measurement of the diameter of the brachial artery. Thus, some studies have used the cuff method to measure the FMD in percentage, the value of which is significantly larger than that using BAUS. The goal of this study was to explore this phenomenon. We explain the interaction between the volume changes (oscillation magnitudes in volume due to cardiac pulsations) of the artery and cuff bladder under different transmural pressures when a sphygmomanometer is wrapped around an upper arm. The compliance of the cuff bladder would be of a fixed value when the cuff pressure is low. The cuff-volume change could be replaced with a cuff-pressure change (oscillation magnitude in cuff pressure due to cardiac pulsation). With the cuff method, the FMDc could be assessed with pressure changes. Then, an inequality formula regarding FMD values by both BAUS (FMDu) and the cuff method (FMDc) was derived; FMDc > 2*FMDu + FMDu2. In order to experimentally verify this inequality formula, fifty-one subjects, including thirty-eight healthy adults and thirteen patients with hypertension, participated in this study. The systolic and diastolic diameters of their brachial arteries and cuff-pressure changes due to cardiac pulsations were separately measured by BAUS and a pressure sensor before and after an ischemic stress. The results showed that FMDu and FMDc were 8.1 ± 4.3% and 121.6 ± 48.6% in the healthy group and 4.5 ± 1.1% and 55.2 ± 22.8% in the patient group, respectively. Thus, the experimental findings comply with the theoretically derived inequality formula.

Relationship Between Arterial Stiffness Index, Pulse Pressure, and Magnetic Resonance Imaging Markers of White Matter Integrity: A UK Biobank Study

Background

Alzheimer's disease and dementia in general constitute one of the major public health problems of the 21st century. Research in arterial stiffness and pulse pressure (PP) play an important role in the quest to reduce the risk of developing dementia through controlling modifiable risk factors.

Objective

The aim of the study is to investigate the association between peripheral PP, arterial stiffness index (ASI) and brain integrity, and to discover if ASI is a better predictor of white matter integrity than peripheral PP.

Materials and Methods

17,984 participants 63.09 ± 7.31 from the UK Biobank were used for this study. ASI was estimated using infrared light (photoplethysmography) and peripheral PP was calculated by subtracting the diastolic from the systolic brachial blood pressure value. Measure of fractional anisotropy (FA) was obtained from diffusion imaging to estimate white matter microstructural integrity. White matter hyperintensities were segmented from the combined T1 and T2-weighted FLAIR images as a measure of irreversible white matter damage.

Results

An important finding is that peripheral PP better predicts white matter integrity when compared to ASI. This finding is consistent until 75 years old. Interestingly, no significant relationship is found between either peripheral PP or ASI and white matter integrity after 75 years old.

Conclusion

These results suggest that ASI from plethysmography should not be used to estimate cerebrovascular integrity in older adults and further question the relationship between arterial stiffness, blood pressure, and white matter damage after the age of 75 years old.

Assessing hemodynamics from the photoplethysmogram to gain insights into vascular age: A review from VascAgeNet

The photoplethysmogram (PPG) signal is widely measured by clinical and consumer devices, and it is emerging as a potential tool for assessing vascular age. The shape and timing of the PPG pulse wave are both influenced by normal vascular aging, changes in arterial stiffness and blood pressure, and atherosclerosis. This review summarizes research into assessing vascular age from the PPG. Three categories of approaches are described: 1) those which use a single PPG signal (based on pulse wave analysis), 2) those which use multiple PPG signals (such as pulse transit time measurement), and 3) those which use PPG and other signals (such as pulse arrival time measurement). Evidence is then presented on the performance, repeatability and reproducibility, and clinical utility of PPG-derived parameters of vascular age. Finally, the review outlines key directions for future research to realize the full potential of photoplethysmography for assessing vascular age.

Aqueous Azadirachta indica (Neem) Extract Attenuates Insulin Resistance to Improve Glycemic Control and Endothelial Function in Subjects with Metabolic Syndrome

Neem (Azadirachta indica) exhibits multiple therapeutic benefits in preclinical studies, but clinical studies are lacking. This clinical study investigated the efficacy and safety of an aqueous A. indica leaf and twig extract (NEEM) on metabolic parameters in subjects with metabolic syndrome (MetS). Subjects were randomized to receive (1) placebo or (2) 125 mg, (3) 250 mg, or (4) 500 mg of NEEM twice daily (n = 20/group) for 12 weeks. Fasting blood sugar (FBS) and insulin, postprandial blood sugar (PPBS), insulin resistance (IR), hemoglobin A1c (HbA1c), endothelial function, circulating markers of inflammation and oxidative stress, lipid profiles, and platelet aggregation were measured at weeks 0, 4, 8, and 12. NEEM supplementation dose dependently improved the trajectories for FBS, PPBS, IR, and HbA1c over time, as well as endothelial function and most markers of inflammation and oxidative stress. Therefore, NEEM may be considered a promising therapeutic to attenuate the hyperglycemia and associated cardiometabolic derangements in people with MetS. Clinical trial registration no.: CTRI/2019/03/018034 [registered on: March 12, 2019].

Indexing cerebrovascular health using near-infrared spectroscopy

Near-infrared spectroscopy (NiRS) is a relatively new technology of brain imaging with its potential in the assessment of cerebrovascular health only recently discovered. Encouraging early results suggest that NiRS can be used as an inexpensive and portable cerebrovascular health tracking device using a recently proposed pulse relaxation function (PReFx). 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PReFx, however, did not have significant correlations with any of the vascular health factors. The proposed timing index is a reliable indicator of cerebrovascular aging factors in the NiRS waveform.

Effect of Omega-3 Fatty Acid Alone and in Combination with Proprietary Chromium Complex on Endothelial Function in Subjects with Metabolic Syndrome: A Randomized, Double-Blind, Parallel-Group Clinical Study

Metabolic syndrome (MetS) represents a cluster of metabolic abnormalities that include hypertension, central obesity, insulin resistance, and dyslipidemia and is strongly associated with an increased risk of diabetes, cardiovascular diseases (CVD), and all-cause mortality. Early diagnosis is important to employ lifestyle and risk factor modification. Existing therapies are limited. Studies report positive effect of omega-3 fatty acids (ω-3FA) on symptoms of metabolic syndrome. The present study was undertaken to evaluate the effect of ω-3FA alone and in combination with proprietary chromium complex (PCC) on endothelial function in subjects with metabolic syndrome. In this randomized, double-blind, parallel-group study, subjects were enrolled into the study after ethics committee (EC) approval and informed consent. Eligible subjects were randomized to receive ω-3FA concentrate 2000 mg (Group A-18 subjects), ω-3FA concentrate 2000 mg + PCC200 mcg (Group B-19 subjects), and ω-3FA concentrate 2000 mg + PCC400 mcg (Group C-21 subjects) daily for 12 weeks. Endothelial dysfunction as measured by reflection index (RI), biomarkers of oxidative stress (NO, MDA, and glutathione), and inflammation (hsCRP, endothelin-1, ICAM-1, and VCAM-1) were evaluated at baseline, 4, and 12 weeks. Lipid-profile and platelet-aggregation tests were performed at baseline and 12 weeks. Adverse drug reactions were recorded. Compliance was assessed by pill count method. GraphPad Prism8 was used for statistical analysis. Significant changes were seen from 4 weeks onwards in all the parameters evaluated. Significant improvement in RI% (mean ± SD = -2.56 ± 0.77 to -3.27 ± 0.67-group A, -2.33 ± 0.76 to 4.72 ± 0.79-group B; -2.39 ± 1.13 to 6.46 ± 1.00-group C) was seen at 12 weeks. Significant improvement in biomarkers of oxidative stress and inflammation was seen with all the treatment groups. Similarly, significant improvement in lipid profile was seen in group B and group C, while group A showed change in HDL, VLDL, and TG. Group C demonstrated the best response in the parameters evaluated. Three patients in group C reported gastrointestinal adverse events, which resolved spontaneously; none stopped the therapy. So, the addition of PCC to ω-3FA may prove to have beneficial effect in reducing cardiovascular morbidity in MetS patients.

A randomised placebo controlled trial of VSL#3® probiotic on biomarkers of cardiovascular risk and liver injury in non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is associated with increased cardiovascular risk irrespective of conventional risk factors. The role of gut-liver interaction is implicated in its development. We investigated the effects of VSL#3^® probiotic supplementation on biomarkers of cardiovascular risk and liver injury in patients with NAFLD.

METHODS

A randomised, double-blinded, placebo-controlled, proof-of-concept study was undertaken. Patients with NAFLD were randomly allocated to take 2 sachets VSL#3^® probiotic or placebo twice daily for 10 weeks. Measurements of endothelial function (digital photoplethysmography, sVCAM-1 and cGMP), oxidative stress (glutathione ratio and LHP), inflammation (hsCRP), insulin resistance (HOMA-IR) and liver injury [transaminases, fibrosis risk score and acoustic structure quantification (ASQ)] were undertaken before and after intervention. Difference in baseline characteristics between the treatment groups was analysed using independent t-test or Mann Whitney U test for non-parametric data. Independent t-test was used to compare the outcomes at the end of the study between the two treatment groups. Wilcoxon Signed Rank test was used to determine the difference in fibrosis risk scores before and after treatment. Spearman's correlation was used to determine any association between cardiovascular and hepatic markers at baseline.

RESULTS

Thirty-five patients completed the study (28 males and 7 females) with a mean age of 57 ± 8 years, body mass index of 32.6 ± 5.0 kg/m² and a relatively short duration of NAFLD (median duration 0.3 IQR 2.0 years). No significant difference was observed in biomarkers of cardiovascular risk and liver injury following VSL#3^® supplementation. Significant correlations were noted between sVCAM-1 and hsCRP (rho = 0.392, p = 0.01), and HOMA-IR and AST (rho = 0.489, p < 0.01) at baseline.

CONCLUSIONS

This is the first study to evaluate the effect of VSL#3^® on ASQ in patients with NAFLD. VSL#3^® did not significantly improve markers of cardiovascular risk and liver injury in patients with NAFLD. However, the study supports an association between endothelial dysfunction and inflammation in patients with NAFLD and suggests that NAFLD is linked with insulin resistance.

TRIAL REGISTRATION

ISRCTN05474560 ( https://doi.org/10.1186/ISRCTN05474560 ) Registered 9 August 2012 (retrospectively registered).

A single arm trial using passive simulated jogging for blunting acute hyperglycemia

Glycemic fluctuations increase oxidative stress, promote endothelial dysfunction and cardiovascular disease. Reducing glycemic fluctuations is beneficial. We previously reported that a portable motorized passive simulated jogging device, (JD) reduces 24 h glycemic indices in type 2 and non-diabetic subjects. This study evaluates effectiveness and feasibility of JD in blunting large glycemic fluctuation induced by an oral glucose tolerance test (OGTT). The study was performed in 10 adult participants mean age 41.3 ± 13.5 year using interstitial glucose monitor (IG). Each participant fasted for 8 h. followed by an OGTT (Pre-JD), thereafter JD was used for 90 min per day for 7 days, without change to diet or activities of daily living. A repeat OGTT (Post-JD) was performed after completion. The integrated area under the curve (iAUC_2h–4h) was computed for the OGTT Pre-JD and Post-JD. Seven days of JD blunted the glucose fluctuation produced by OGTT. JD decreased AUC_2h by 17 ± 4.7% and iAUC_4h by 15 ± 5.9% (p < 0.03). In healthy mostly obese participants 7 days of JD blunts the hyperglycemic response produced by an OGTT. JD may be an adjunct to current glycemic management, it can be applied in different postures for those who cannot (due to physical or cognitive limitations) or will not exercise.

Trial registration:ClinicalTrials.gov NCT03550105 (08-06-2018).

Wireless, non-invasive, wearable device for continuous remote monitoring of hemodynamic parameters in a swine model of controlled hemorrhagic shock

Accurate and continuous monitoring of critically ill patients is frequently achieved using invasive catheters, which is technically complex. Our purpose was to evaluate the validity and accuracy of a photoplethysmography (PPG)-based remote monitoring device compared to invasive methods of arterial line (AL) and Swan-Ganz (SG) catheters in a swine model of controlled hemorrhagic shock. Following a baseline phase, hemorrhagic shock was induced in 11 pigs by bleeding 35% of their blood volume, followed by a post-bleeding follow-up phase. Animals were monitored concomitantly by the PPG device, an AL and a SG catheter, for a median period of 447 min. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP, respectively), and cardiac output (CO) were recorded continuously. The complete data set consisted of 1312 paired observations. Correlations between the PPG-based technique and the invasive methods were significant (p < 0.001) during baseline, bleeding and follow-up phases for HR (r = 0.90–0.98), SBP (r = 0.90–0.94), DBP (r = 0.89–0.93), and CO (r = 0.76–0.90). Intraclass correlations for all phases combined were 0.96, 0.92, 0.93 and 0.87 for HR, SBP, DBP and CO, respectively. Correlations for changes in CO, SBP and DBP were significant (p < 0.001) and strong (r > 0.88), with concordance rates (determined by quadrant plots) of 86%, 66% and 68%, respectively. The novel PPG-based device was accurate and valid compared to existing invasive techniques and might be used for continuous monitoring in several clinical settings following further studies.

A randomized, double-blind, positive-controlled, prospective, dose-response clinical study to evaluate the efficacy and tolerability of an aqueous extract of Terminalia bellerica in lowering uric acid and creatinine levels in chronic kidney disease subjects with hyperuricemia

Background

Hyperuricemia is an independent risk factor in chronic kidney disease (CKD). Allopurinol and febuxostat are prescription medicines used to treat hyperuricemia but suffer side-effects. Earlier clinical study has shown that an aqueous extract of Terminalia bellerica (TBE), significantly reduced uric acid levels with no serious adverse effects in hyperuricemic subjects. The objective of this study is to determine the efficacy and tolerability of TB in reducing uric acid and creatinine levels in CKD subjects.

Methods

59-subjects were randomized to three groups-40 mg-once-daily febuxostat, 500 mg-twice-daily and 1000 mg-twice-daily of TBE. Serum uric acid, creatinine levels and estimated-glometular-filtration-rate were measured at baseline, 4, 8, 12, 16, 20, 24-weeks. Biomarkers of oxidative-stress, endothelial function, systemic inflammation, and platelet-aggregation were evaluated at baseline, 4, 8, 12, 24-weeks. Adverse drug reactions were recorded. Statistical analysis evaluated using GraphPadPrism4.

Results

55-subjects completed 24-week study. Starting at 4-weeks, all treatment groups showed a significant decrease in serum uric acid levels from baseline (p ≤ 0.0001). At 24-weeks, febuxostat, T.bellerica 500 mg-twice-daily, and T.bellerica 1000 mg-twice-daily doses decreased mean-percentage serum uric acid by 63.70 ± 4.62, 19.84 ± 6.43 and 33.88% ± 4.95% respectively (p ≤ 0.0001). Significant decrease in serum creatinine with all the groups starting at 16-weeks was seen (p ≤ 0.005-p ≤ 0.0001). At 24-weeks, the mean-percentage change in creatinine levels was 23.71 ± 12.50, 11.70 ± 9.0, and 24.42 ± 8.14, respectively with febuxostat, T.bellerica 500 mg-twice-daily and T.bellerica 1000 mg-twice-daily. Statistically significant (p ≤ 0.05) increase in estimated glomerular filtration rate-(eGFR) was seen at 20 (p ≤ 0.05) and 24-weeks (p ≤ 0.01) for both febuxostat vs T.bellerica 500 mg-twice-daily and T.bellerica 1000 mg-twice-daily vs T.bellerica 500 mg-twice-daily. There was no statistically significant difference between febuxostat and T.bellerica 1000 mg-twice-daily, with an increase of eGFR of 41.38 and 40.39 ml/min/1.73m² respectively, with the inference that T.bellerica at 1000 mg-twice-daily dose is as good as febuxostat 40 mg-once-daily. Positive improvements were made by all the groups in endothelial function and the related biomarkers and high-sensitivity C-reactive protein. None of the products showed effect on platelet aggregation.

Conclusion

In this 24-week study Febuxostat 40 mg, T. bellerica 500 mg-twice-daily and 1000 mg-twice-daily, significantly decreased the serum uric acid and creatinine levels, increased eGFR in CKD subjects. T. bellerica 500 mg-twice-daily and 1000 mg-twice-daily were one-third and more than half as effective at 24-weeks, respectively. T. bellerica extract may be considered a natural alternative for reducing serum uric acid levels.

Trial registration

This study was registered with the Clinical Trials Registry – India (CTRI) with the registration number: CTRI/2019/11/022093 [Registered on: 21/11/2019] Trial Registered Retrospectively.

Effect of an aqueous extract of Terminalia chebula on endothelial dysfunction, systemic inflammation, and lipid profile in type 2 diabetes mellitus: A randomized double-blind, placebo-controlled clinical study

Endothelial dysfunction is a crucial complication in type 2 diabetic patients, related to cardiovascular risk. Terminalia chebula (TC), a traditional ayurvedic herb, is known for its antioxidant and antihyperlipidemic activity. A prospective, randomized, double-blind, placebo-controlled clinical study was undertaken to evaluate the effects of an aqueous extract of T. chebula 250 and 500 mg versus placebo on endothelial dysfunction and biomarkers of oxidative stress in type 2 diabetic patients. A total of 60 eligible patients were randomized to receive either T. chebula 250 mg, T. chebula 500 mg, or placebo twice daily for 12 weeks. The subjects were assessed based on the endothelial function, the levels of nitric oxide, malondialdehyde, glutathione, high sensitivity C-reactive protein, glycosylated hemoglobin, and lipid profile at baseline and after 12 weeks of treatment. Treatment with T. chebula 250 mg and T. chebula 500 mg for 12 weeks significantly improved the endothelial function (reflection index) compared to placebo (absolute changes: - T. chebula 250: -2.55 ± 1.82% vs. T. chebula 500: -5.21 ± 2.41% vs. placebo: 1.40 ± 2.11%). Other cardiovascular risk indicators were also significantly ameliorated in the treatment groups compared to placebo. In conclusion, T. chebula (especially, 500 mg BID dose) significantly minimized the cardiovascular risk factors in patients with type 2 diabetes compared to placebo.

Associations Between Depression, Arterial Stiffness, and Metabolic Syndrome Among Adults in the UK Biobank Population Study: A Mediation Analysis

Importance

Previous research has linked a history of depression with arterial stiffness (AS) during midlife.

Objective

To assess the association of depression with elevated midlife AS and to investigate the extent to which this association is mediated via metabolic syndrome (MetS).

Design, Settings, and Participants

This population-based retrospective cohort study analyzed data collected between March 2006 and December 2010 from 124 445 participants aged 40 to 69 years from the UK Biobank. Participants without data on AS at baseline (n = 332 780) or who reported a previous diagnosis of cardiovascular disease (n = 45 374) were not eligible. Data analysis was performed from May to August 2019.

Exposures

Lifetime history of depression was assessed via verbal interview and linked hospital-based clinical depression diagnosis. Metabolic syndrome was defined as the presence of 3 or more of hypertension, dyslipidemia, hyperglycemia, hypertriglyceridemia, and unhealthy waist circumference.

Main Outcomes and Measures

Peripherally assessed AS index (ASI) using digital photoplethysmography.

Results

Of 124 445 included participants with ASI assessed, 71 799 (57.7%) were women, and the mean (SD) age was 56 (8) years. A total of 10 304 participants (8.3%) reported a history of depression. Study findings indicated a significant direct association between depression and ASI levels (β = 0.25; 95% CI, 0.17-0.32). A significant indirect association was also observed between depression and ASI levels (β = 0.10; 95% CI, 0.07-0.13), indicating that 29% of the association of depression with ASI was mediated by MetS. The proportion of mediation increased to 37% when C-reactive protein was added to the MetS criteria (direct association: β = 0.21; 95% CI, 0.15-0.28; indirect association: β = 0.13; 95% CI, 0.10-0.17). Concerning components of MetS, the strongest indirect association was for waist circumference, accounting for 25% of the association between depression and ASI levels (direct association: β = 0.26; 95% CI, 0.18-0.34; indirect association: β = 0.09; 95% CI, 0.06-0.11). Among men, hypertriglyceridemia accounted for 19% of the association between depression and ASI (direct association: β = 0.22; 95% CI, 0.05-0.40; indirect association: β = 0.05; 95% CI, 0.02-0.08).

Conclusions and Relevance

One-third of the association of depression with elevated ASI levels during midlife may be accounted for by combined MetS and inflammatory processes. Unhealthy waist circumference and hypertriglyceridemia emerged as the most important potential targets for preventive interventions within women and men, respectively.

The Influence of Dialytic Modality on Arterial Stiffness, Pulse Wave Reflections, and Vasomotor Function

Background

Measurements of aortic stiffness [aortic pulse wave velocity (PWV) and augmentation index (AIx)] have been established as powerful predictors of survival on hemodialysis (HD). Abnormal endothelial-dependent and endothelial-independent vascular reactivity and increased arterial stiffness are commonly described in HD patients. There is, however, a lack of information on the comparative impact of different renal replacement therapies (RRTs) on PWV and AIx, and how these different methods might influence endothelial-dependent abnormal vasodilatation.

Objective

To describe in a cross-sectional design arterial compliance and distensibility in continuous ambulatory peritoneal dialysis (CAPD) versus HD versus renal transplant (RTx) patients, compared with age- and blood pressure-matched essential hypertensive controls. The PWV and aortic AIx were determined from contour analysis of arterial waveforms recorded by applanation tonometry in 40 CAPD, 41 HD, 20 RTx patients (with normal serum creatinine), and 20 controls with essential hypertension (all normotensive under treatment). Endothelial-dependent and endothelial-independent vascular reactivities were assessed by changes in AIx following challenges with inhaled salbutamol and sublingual nitroglycerin respectively.

Results

CAPD patients had significantly stiffer arteries than all other categories. The PWV was 8.29 ± 1.09 m/second in CAPD patients, significantly higher ( p < 0.05) compared to HD subjects (7.19 ± 1.87 m/s). Both dialysis subgroups had significantly higher PWV values compared to RTx patients (6.59 ± 1.62 m/s) and essential hypertensive controls (6.34 ± 1.32 m/s), p < 0.05. The AIx had a profile similar to PWV in different RRTs. All groups with the exception of CAPD subjects had a significant decrease in AIx following salbutamol. Moreover, the vasodilatation induced by either nitroglycerin or salbutamol was significantly blunted compared to HD. Overall, both dialysis categories had more abnormal responses compared to RTx patients and essential hypertensive controls.

Conclusion

CAPD is associated with stiffer arteries and more profoundly abnormal endothelial-dependent vasomotor function, compared to matched HD subjects. These differences in arterial physical properties might explain differences seen in cardiac structure and function between the RRTs.

Mathematical relationships of patterns of 35 rat haemodynamic parameters for conditions of hypertension resulting from decreased nitric oxide bioavailability

NEW FINDINGS

What is the central question of this study? Can the cross-relationship between 35 rat arterial pulse waveform (APW) parameters be described by known mathematical functions and can mathematical parameters be obtained for conditions in a model of hypertension resulting from decreased NO bioavailability? What is the main finding and its importance? Mathematical functions and their parameters were obtained that approximate the cross-relationships of 35 APW parameters to systolic blood pressure and to the augmentation index in conditions of decreased NO bioavailability. The results enable APW parameters to be assigned to decreased NO bioavailability, which may have predictive or diagnostic value.

ABSTRACT

Information obtained from the arterial pulse waveform (APW) using haemodynamic parameters (HPs) is useful for characterization of the cardiovascular system in particular (patho)physiological conditions. Our goal was to find out whether the relationships between rat HPs could be described by simple mathematical functions and to find mathematical parameters for conditions of high blood pressure (BP) resulting from decreased NO bioavailability. The right jugular vein of anaesthetized Wistar rats was cannulated for i.v. administration of N^ω -nitro-l-arginine methyl ester (l-NAME). The left common carotid artery was cannulated to detect the APW. From 10 points on the rat APW we defined 35 HPs (some were known already) and found 595 cross-relationships between HPs showing unique patterns for particular cardiovascular conditions. Here we show parallel time-dependent changes of 35 HPs and some of their cross-relationships in condition of high BP induced by l-NAME. We found that most of the time-dependent changes of 35 HPs and their relationships were very well fitted by simple mathematical functions, e.g. a linear function, exponential growth, exponential decay or exponential rise to maximum. The results may enable the mathematical functions to be assigned for decreased NO bioavailability, which may have predictive or diagnostic value for conditions of high BP. Using this approach, it may be possible to find unique cross-relationship patterns of HPs and mathematical functions between HPs for different cardiovascular (patho)physiological or drug-modulating conditions. This knowledge can be used in studying the molecular mechanisms of particular (patho)physiological conditions or drug actions and may have predictive or diagnostic value.

Evaluation of the Effect of Fish Oil Alone and in Combination with a Proprietary Chromium Complex on Endothelial Dysfunction, Systemic Inflammation and Lipid Profile in Type 2 Diabetes Mellitus - A Randomized, Double-Blind, Placebo-Controlled Clinical Study

PURPOSE

This study was conducted to evaluate the effectiveness of fish oil alone and with an adjunct, a proprietary chromium complex (PCC), on cardiovascular parameters - endothelial dysfunction, lipid profile, systemic inflammation and glycosylated hemoglobin - in a 12-week randomized, double-blind, placebo-controlled clinical study in type 2 diabetes mellitus subjects.

PATIENTS AND METHODS

In this randomized, double-blind, parallel group study, 59 subjects in three groups completed the study: Group A, fish oil 2000 mg; Group B, fish oil 2000 mg + PCC 10 mg (200 µg of Cr³⁺); and Group C, fish oil 2000 mg + PCC 20 mg (400 µg of Cr³⁺) daily for 12 weeks (2000 mg of fish oil contained 600 mg of eicosapentaenoic acid [EPA] and 400 mg of docosahexaenoic acid [DHA], the omega-3 fatty acids). Endothelial function, by estimating reflection index (RI), biomarkers of oxidative stress (nitric oxide [NO], malondialdehyde [MDA], glutathione [GSH]) and inflammatory biomarkers (high-sensitivity C-reactive protein [hsCRP], intercellular adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1], endothelin-1) were evaluated at baseline, and 4 and 12 weeks. Lipid profile, platelet aggregation and glycosylated hemoglobin [HbA1c) were tested at baseline and 12 weeks. Any reported adverse drug reactions were recorded. Statistical analysis was performed using GraphPad Prism 8.

RESULTS

The present study shows that fish oil by itself, at a dose of 2000 mg (600 mg of EPA + 400 mg of DHA) per day, led to significant, but only modest, improvement in cardiovascular parameters (RI from -2.38±0.75 to -3.92±0.60, MDA from 3.77±0.16 to 3.74±0.16 nM/mL, NO from 30.60±3.18 to 32.12±3.40 µM/L, GSH from 568.93±5.91 to 583.95±6.53 µM/L; p≤0.0001), including triglyceride levels. However, when PCC was added to fish oil, especially at the 20 mg dose, there were highly significant improvements in all the parameters tested (RI from -2.04±0.79 to -8.73±1.36, MDA from 3.67±0.39 to 2.89±0.34 nM/mL, NO from 28.98±2.93 to 40.01±2.53 µM/L, GSH from 553.82±8.18 to 677.99±10.19 µM/L; p≤0.0001), including the lipid profile. It is noteworthy that the triglycerides were decreased significantly by addition of 20 mg of PCC although the dose of fish oil was only 2 g/day and the baseline triglyceride levels were only about 200 mg/dL. Fish oil alone did not significantly decrease the HbA1c, whereas the addition of 20 mg of PCC did.

CONCLUSION

Addition of PCC, especially at 20 mg dose, significantly improves the efficacy of fish oil in addressing cardiovascular risk factors compared to fish oil given alone.

Evaluation of the Effect of an Aqueous Extract of Azadirachta indica (Neem) Leaves and Twigs on Glycemic Control, Endothelial Dysfunction and Systemic Inflammation in Subjects with Type 2 Diabetes Mellitus - A Randomized, Double-Blind, Placebo-Controlled Clinical Study

PURPOSE

Neem tree (Azadirachta indica) offers different bioactives ranging from pesticides to therapeutic molecules, depending on which part of the plant is used and the extraction methodology and the solvent used. This study was aimed at evaluating the safety and efficacy of a standardized aqueous extract of Azadirachta indica leaves and twigs (NEEM) on glycemic control, endothelial dysfunction, and systemic inflammation in patients with type 2 diabetes mellitus (T2DM).

METHODS

In this randomized, double-blind, placebo-controlled clinical study (RCT), 80 T2DM subjects, who have already been on standard metformin therapy, received either 125 mg, 250 mg, 500 mg of NEEM or placebo twice daily for 12 weeks. Postprandial blood sugar level (PPBS), fasting blood sugar level (FBS), glycosylated hemoglobin (HbA1c), insulin resistance (IR), endothelial function, oxidative stress, systemic inflammation, IL-6 and TNF-α, platelet aggregation and lipid profile were assessed. Adverse drug reactions, if any, were noted. GraphPad Prism 8 was used to perform statistical analysis.

RESULTS

NEEM at the doses of 125, 250, and 500 mg BID significantly reduced PPBS (from 194.4±14 to 173.1±12.8mg/dL, 192.3±17.1 to 161.8±9.7mg/dL, and 205.9±7.2 to 159.3±7.1mg/dL, respectively), FBS (from 119.2±5.0 to 109.2±5.7mg/dL, 115.5±4.4 to 103.7±4.2mg/dL, and 120.7±4.2 to 97.3±3.7mg/dL, respectively), HbA1c (from 6.87 ± 0.4% to 6.64 ± 0.4%, 7.52 ± 0.4% to 6.86 ± 0.3%, and 7.78 ± 0.2% to 6.26 ± 0.4%, respectively), and IR (from 4.5 ± 1.2 to 3.4 ± 0.9, 3.8 ± 1.1 to 2.5 ± 0.6, and 4.6 ± 1.3 to 2.0 ± 0.6, respectively) compared to placebo. Also, NEEM significantly improved endothelial function, decreased oxidative stress and systemic inflammation compared to placebo. The efficacy was significant with all the doses, but no effect on platelet aggregation or lipid profile was observed.

CONCLUSION

NEEM may significantly ameliorate hyperglycemia, endothelial dysfunction, and systemic inflammation, on top of what metformin could do, in subjects with T2DM.

Whole body periodic acceleration in normal and reduced mucociliary clearance of conscious sheep

The purpose of this investigation was to ascertain whether nitric oxide (NO) released into the circulation by a noninvasive technology called whole body periodic acceleration (WBPA) could increase mucociliary clearance (MCC). It was based on observations by others that nitric oxide donor drugs increase ciliary beat frequency of nasal epithelium without increasing mucociliary clearance. Tracheal mucous velocity (TMV), a reflection of MCC, was measured in sheep after 1-hour treatment of WBPA and repeated after pretreatment with the NO synthase inhibitor, L-NAME to demonstrated action of NO. Aerosolized human neutrophil elastase (HNE) was administered to sheep to suppress TMV as might occur in cystic fibrosis and other inflammatory lung diseases. WBPA increased TMV to a peak of 136% of baseline 1h after intervention, an effect blocked by L-NAME. HNE reduced TMV to 55% of baseline but slowing was reversed by WBPA, protection lost in the presence of L-NAME. NO released into the circulation from eNOS by WBPA can acutely access airway epithelium for improving MCC slowed in cystic fibrosis and other inflammatory lung diseases as a means of enhancing host defense against pathogens.

Modeling arterial pulse waves in healthy aging: a database for in silico evaluation of hemodynamics and pulse wave indexes

The arterial pulse wave (PW) is a rich source of information on cardiovascular (CV) health. It is widely measured by both consumer and clinical devices. However, the physical determinants of the PW are not yet fully understood, and the development of PW analysis algorithms is limited by a lack of PW data sets containing reference CV measurements. Our aim was to create a database of PWs simulated by a computer to span a range of CV conditions, representative of a sample of healthy adults. The typical CV properties of 25-75 yr olds were identified through a literature review. These were used as inputs to a computational model to simulate PWs for subjects of each age decade. Pressure, flow velocity, luminal area, and photoplethysmographic PWs were simulated at common measurement sites, and PW indexes were extracted. The database, containing PWs from 4,374 virtual subjects, was verified by comparing the simulated PWs and derived indexes with corresponding in vivo data. Good agreement was observed, with well-reproduced age-related changes in hemodynamic parameters and PW morphology. The utility of the database was demonstrated through case studies providing novel hemodynamic insights, in silico assessment of PW algorithms, and pilot data to inform the design of clinical PW algorithm assessments. In conclusion, the publicly available PW database is a valuable resource for understanding CV determinants of PWs and for the development and preclinical assessment of PW analysis algorithms. It is particularly useful because the exact CV properties that generated each PW are known.NEW & NOTEWORTHY First, a comprehensive literature review of changes in cardiovascular properties with age was performed. Second, an approach for simulating pulse waves (PWs) at different ages was designed and verified against in vivo data. Third, a PW database was created, and its utility was illustrated through three case studies investigating the determinants of PW indexes. Fourth, the database and tools for creating the database, analyzing PWs, and replicating the case studies are freely available.

Arterial Stiffness Parameters Correlate with Estimated Cardiovascular Risk in Humans: A Clinical Study

Arterial stiffness is said to be a novel predictor of cardiovascular events. This study investigated the correlation between arterial stiffness parameters and the estimated cardiovascular disease risk (RISK) in a Polish cohort of patients divided by age, sex, and body-mass index (BMI). The cross-sectional study enrolled 295 patients who met the inclusion criteria. Subjects were divided into three age groups, four weight groups, and by gender. The stiffness of the vessels was assessed by the measurement of the stiffness index (SI) and reflection index (RI). An individual 10-year RISK was calculated for each patient using the Heart Risk Calculator algorithm by the American Heart Association. A correlation between the SI and estimated RISK was observed (rS 0.42, p < 0.05). The strongest relationship was presented for women, the age group 40-54, and individuals with normal weight. The correlation between RI and calculated RISK was observed (rS 0.19, p < 0.05), the highest correlation was noticed for people aged 40-54 and obese. In conclusion, both SI and RI are correlated with estimated cardiovascular risk, however SI seems to be more useful than RI to predict the individual risk of future cardiovascular events. Both of these can be measured using non-invasive techniques, which demonstrates their potential utility in clinical practice.

An Unobtrusive and Calibration-free Blood Pressure Estimation Method using Photoplethysmography and Biometrics

We introduce a novel paradigm to unobtrusively and optically measure blood pressure (BP) without calibration. The algorithm combines photoplethysmography (PPG) waveform analysis and biometrics to estimate BP, and was evaluated in subjects with various age, height, weight and BP levels (n = 1249). In the young population (<50 years old) with low, medium and high systolic blood pressures (SBP, <120 mmHg; 120-139 mmHg; ≥140 mmHg), the fitting errors are 6.3 ± 7.2, -3.9 ± 7.2 and -20.2 ± 14.2 mmHg for SBP respectively; In the older population (>50 years old) with the same categories, the fitting errors are 12.8 ± 9.0, 0.5 ± 8.2 and -14.6 ± 11.5 mmHg for SBP respectively. A simple personalized calibration reduces fitting errors significantly (n = 147), and good peripheral perfusion helps to improve the fitting accuracy. In conclusion, PPG may be used to calculate BP without calibration in certain populations. When calibrated, it shows great potential to serially monitor BP fluctuation, which can bring tremendous economic and health benefits.

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.

Endothelium-dependent adaptation of arterial wall viscosity during blood flow increase is impaired in essential hypertension

BACKGROUND AND AIMS

Arterial wall viscosity (AWV) is regulated by endothelium-derived NO and epoxyeicosatrienoic acids (EETs) under baseline physiological conditions. Whether these factors regulate AWV during blood flow increase and whether this mechanism is affected in essential hypertensive patients (HT) remain unknown.

METHODS

The evolution of radial artery diameter, wall thickness and arterial pressure in response to an increase in flow induced by hand skin heating were measured in 18 untreated HT and 14 normotensive controls (NT) during local infusion of saline and the respective pharmacological inhibitors of NO-synthase and EETs synthesis by cytochrome P450, L-NMMA and/or fluconazole. AWV was estimated by the ratio of the viscous energy dissipated (W_V) to the elastic energy stored (W_E) obtained from the pressure-diameter relationship. Concomitant changes in operating conditions, which influence the AWV, were taken into account by calculating the midwall stress.

RESULTS

Baseline W_V and W_E were higher in HT than in NT but W_V/W_E was similar. In saline condition, W_V/W_E increased in HT during heating but not in NT. In the presence of L-NMMA and/or fluconazole, W_V/W_E increased during heating in NT. In contrast, these inhibitors did not modify the increase in W_V/W_E during heating in HT compared to saline. In all conditions, a larger increase in W_V than W_E was responsible for the increase in W_V/W_E.

CONCLUSIONS

The release of NO and EETs maintains a stable AWV during flow increase and this endothelial adaptive regulation is lost during essential hypertension, which may promote excessive viscous energy dissipation and cardiovascular uncoupling. Restoration of EETs availability with inhibitors of soluble epoxide hydrolase could thus constitute a promising pharmacological approach to restore the endothelial adaptive regulation of AWV.

Noninvasive continuous detection of arterial hypotension during induction of anaesthesia using a photoplethysmographic signal: proof of concept

BACKGROUND

During general anaesthesia, intraoperative hypotension (IOH), defined as a mean arterial pressure (MAP) reduction of > 20%, is frequent and may lead to complications. Pulse oximetry is mandatory in the operating room, making the photoplethysmographic signal and parameters, such as relative dicrotic notch height (Dic_pleth) or perfusion index (PI), readily available. The purpose of this study was to investigate whether relative variations of Dic_pleth and PI could detect IOH during anaesthesia induction, and to follow their variations during vasopressor boluses.

METHODS

MAP, Dic_pleth, and PI were monitored at 1-min intervals during target control induction of anaesthesia with propofol and remifentanil in 61 subjects. Vasopressor infusion (norepinephrine or phenylephrine) was performed when hypotension occurred according to the decision of the physician.

RESULTS

The delta in Dic_pleth and PI accurately detected IOH, with areas under the receiver operating characteristic curves (AUC) of 0.86 and 0.83, respectively. The optimal thresholds were -19% (sensitivity 79%; specificity 84%) and 51% (sensitivity 82%; specificity 74%) for ΔDic_pleth and ΔPI, respectively. There was no difference between the ROC of ΔDic_pleth and ΔPI (P=0.22). Combining both ΔDic_pleth and ΔPI further improved the hypotension detection power (AUC=0.91) with a sensitivity and specificity of 84%. MAP variations were correlated with ΔDic_pleth and ΔPI during vasopressor infusion (r=0.73 and -0.62, respectively; P<0.001).

CONCLUSIONS

The relative variation in Dic_pleth and PI derived from the photoplethysmographic signal can be used as a non invasive, continuous, and simple tool to detect intraoperative hypotension, and to track the vascular response to vasoconstrictor drugs during induction of general anaesthesia.

CLINICAL TRIAL REGISTRATION

NCT03756935.

Continuous non-invasive determination of nocturnal blood pressure variation using photoplethysmographic pulse wave signals: comparison of pulse propagation time, pulse transit time and RR-interval

OBJECTIVE

Cardiovascular diseases are the leading cause of death, whereas nocturnal ambulatory blood pressure (BP) is the most potent predictor for cardiovascular risk. The volume clamp and pulse transit time (PTT) are common methods for continuous non-invasive BP measurement, but have drawbacks during unsupervised ambulatory use and undisturbed sleep. The pulse propagation time (PPT), defined as the time between pulse wave systolic peak and diastolic peak, provides valid information about the pressure pulse waveform. However, the use of PPT for nocturnal BP variation determination and whether such variation is affected by BP or heart rate (i.e. RR-interval or RRI) has not been investigated.

APPROACH

To assess whether the PPT method is suitable for ubiquitous nocturnal BP monitoring, we compared systolic blood pressure (SBP) estimates derived from PPT, PTT, and RRI signals with parallel recorded BP measurements. The RRI-derived SBP signals were used as a baseline for testing a potential heart rate dependency. This work provides an overview of BP measurements, presents the developed real-time signal analysis, and describes the performance assessment. The signal analysis was validated with data records from 42 subjects acquired from an ergometry and sleep laboratory in equal parts.

MAIN RESULTS

The algorithms applied to the ergometry laboratory database achieved a correlation coefficient between reference SBP and estimated SBP_PPT of 0.89 (p  <  0.001) with bias 0.1 mmHg and limits of agreement (LoA)  -29.8 to 30.0 mmHg, SBP_PTT of 0.97 (p  <  0.001) with bias 0.0 mmHg and LoA  -15.2 to 15.3 mmHg, and SBP_RRI of 0.96 (p  <  0.001) with bias 0.0 mmHg and LoA  -19.5 to 19.5 mmHg. For the sleep laboratory database, the correlation coefficient was 0.95 (p  <  0.001) with bias 0.2 mmHg and LoA  -18.3 to 18.8 mmHg for SBP_PPT, 0.88 (p  <  0.001) with bias 0.0 mmHg and LoA  -25.0 to 24.9 mmHg for SBP_PTT, and 0.88 (p  <  0.001) with bias of 0.1 mmHg and LoA  -23.6 to 23.7 mmHg for SBP_RRI. A heart rate dependency of PPT or PTT could not be found. The analysis of variance shows no significant differences between the reference SBP values and the estimated values for either the ergometry (F(3, 627)  =  2.27, p  =  0.08) or the sleep laboratory (F(3, 327)  =  2.28, p  =  0.08).

SIGNIFICANCE

In conclusion, the PPT method seems to be an interesting alternative for continuous determination of SBP during simplified cardiovascular monitoring and sleep screening compared to more expensive devices based on volume clamp or PTT methods.

Effectiveness of a 4-week rehabilitation program on endothelial function, blood vessel elasticity in patients with chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) may have considerable cardiovascular risk. Physical activity has a paramount role in COPD treatment. Our aim was to evaluate the applicability of arteriograph in COPD and measure the effectiveness of pulmonary rehabilitation on endothelial function.

Methods

A total of 40 patients with COPD (FEV₁: 45.43±20.20%pred, BMI: 27.99±6.98 kg/m², male: female was 21:19, age: 65.47±7.39 years) participated in a 4-week rehabilitation program. We used a patented, invasively validated Arteriograph. Blood pressure, pulse, augmentation index (AIX), pulse wave velocity (PWV), diastolic area index (DAI) were registered with functional measurements in pulmonary rehabilitation.

Results

Pulmonary rehabilitation was effective in 6 minutes walking distance (6MWD: 335.32±110.43 vs. 398.32±126.21 m), maximal inspiratory pressure (MIP: 57.72±22.69 vs. 63.63±18.01 cmH₂O), chest wall expansion (CWE: 2.84±1.26 vs. 4.00±1.76 cm), breath holding time (BHT: 25.77±10.63 to 29.21±11.60 sec) and grip strength (GS: 24.87±11.88 vs. 27.03±11.43 kg) (P<0.05). Improvement in quality of life was monitored by COPD assessment test marker (CAT: 17.00±8.49 vs. 11.89±7.31, P<0.05). Systolic (133.38±22.15 vs. 126.48±20.22 mmHg) and diastolic blood pressure (76.95±14.37 vs. 75.4±12.7 mmHg) showed a reduction tendency. Pulse also decreased (76.95±14.37 vs. 72.53±13.65 bpm). AIX levels showed slight improvement (3.54±35.59% vs. 2.93±30.79%); 23 patients peripheral circulation progressed. The PWV data showed abnormal elasticity with minimal change (11.74±2.13 vs. 11.4±2.73 m/s); although 20 patients showed improvement. DAI detected slightly diminished coronary circulation with moderate improvement (43.32±6.81 vs. 47.1±7.01 m/s).

Conclusions

Elevated arterial stiffness, high PWV turned the COPD patients to the high/very high-risk cluster. Rehabilitation resulted significant improvement in MIP, CWE, BHT, 6MWD, CAT with mild, but favorable changes in blood pressure, pulse, AIX, PWV. As a consequence of the four weeks rehabilitation period overall quality of life improved and cardiovascular risk showed a reduction tendency in COPD.

Changes of Arterial Pulse Waveform Characteristics with Gestational Age during Normal Pregnancy

Arterial pulse waveform analysis has been widely used to reflect physiological changes in the cardiovascular system. This study aimed to comprehensively investigate the changes of waveform characteristics of both photoplethysmographic (PPG) and radial pulses with gestational age during normal pregnancy. PPG and radial pulses were simultaneously recorded from 130 healthy pregnant women at seven gestational time points. After normalizing the arterial pulse waveforms, the abscissa of notch point, the total pulse area and the reflection index were extracted and compared between different measurement points and between the PPG and radial pulses using post-hoc multiple comparisons with Bonferrioni correction. The results showed that the effect of gestational age on all the three waveform characteristics was significant (all p < 0.001) after adjusting for maternal age, heart rate and blood pressures. All the three waveform characteristics demonstrated similar changing trends with gestational age, and they were all significantly different between the measurements from gestational week 12–15 and the others (all p < 0.05, except for the PPG total pulse area between the first and second measurement points). In conclusion, this study has comprehensively quantified similar changes of both PPG and radial pulse waveform characteristics with gestational age.

Changes of blood pressure following initiation of physical inactivity and after external addition of pulses to circulation

PURPOSE

To determine whether an innovative, motorized, wellness device that effortlessly produces physical activity (JD) can mitigate the hypertensive effects of prolonged sitting or lying down.

METHODS

Twenty-two normotensive and hypertensive adults of both genders gave informed consent to participate in a randomized controlled crossover study of a passive simulated jogging device (JD) in both supine and seated postures. Each study participant was monitored with a continuous non-invasive arterial pressure monitoring device (CNAP) over 60 min. The initial 10 min served as baseline for each posture. The subjects were randomized to begin with either JD or SHAM control for 30 min, and monitoring was continued for an additional 10 min in one posture; three days later posture and order of JD or SHAM were changed.

RESULTS

In both seated and supine postures, SHAM was associated with a significant rise in blood pressure (BP) which was observed within 5-10 min; it continued to rise or remain elevated for over a 40-min observation period. In contrast, JD produced a significant decrease in both systolic and diastolic blood pressure in both postures. During recovery in seated posture JD decreased systolic and diastolic BP by - 8.1 and - 7.6 mmHg, respectively. In supine posture, a similar decrease in BP occurred.

CONCLUSIONS

There is rapid onset of increase in systolic and diastolic BP with physical inactivity in both supine and seated postures. Administration of JD significantly decreased BP in both postures. Further studies are needed to assess long-term effectiveness.

Treating endothelial dysfunction with vitamin D in chronic kidney disease: a meta-analysis

Background

Vitamin D deficiency is common in patients with chronic kidney disease (CKD), and is associated with endothelial dysfunction and cardiovascular disease. We performed a meta-analysis to assess the effect of vitamin D treatment on flow mediated vasodilation (FMD) in CKD patients.

Methods

PubMed/Medline, Web of Science, Embase and Cochrane trials and reviews were searched systematically for randomized controlled trials (RCT:s) using any vitamin D compound, at any stage of CKD, with FMD as outcome. Fixed and random effects models were performed using the standardized mean difference effect size post treatment for each trial. Heterogeneity was assessed by I² statistics.

Results

4 trials were included, comprising 305 patients. One used both 1 and 2 μg for two intervention groups and was therefore split in two during the analysis. Patients in the included trials had a mean age of 44–65 years and were all in CKD 3 to 4. One study used cholecalciferol, the others all used paricalcitol as treatment. Study duration was 12–16 weeks. Intervention with vitamin D was associated with ameliorated FMD (STANDmean ES 0.78, 95% CI 0.55–1.01) in a fixed model. Heterogeneity was substantial (I² = 84%). Secondary analysis with random model analysis also showed significant results.

Conclusions

Short term intervention with vitamin D is associated with improvements in endothelial function, as measured by FMD. This indicates positive effects of vitamin D on vascular disease in CKD. Limitations of this meta-analysis are the small number of studies performed, and the short duration of intervention.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-1042-y) contains supplementary material, which is available to authorized users.

The interrelation of endothelial function and microvascular reactivity in different vascular beds, and risk assessment in hypertension: results from the Doxazosin-ramipril study

There are several non-invasive methods to study endothelial function, but their interrelation and association to cardiovascular risk have not been well evaluated. We studied macrovascular and microvascular endothelial function simultaneously in different vascular beds in relation to cardiovascular mortality risk (Systematic Coronary Risk Evaluation, SCORE) and hypertension induced cardiac organ damage, and their interrelationship. The study investigated 71 hypertensive patients by forearm post-ischemic flow-mediated vasodilation, pulse wave analysis (applanation tonometry) and beta 2-adrenoceptor agonist stimulation for changes in reflection index, skin microvascular reactivity by laser Doppler fluxmetry with iontophoresis and heat-induced hyperaemia, and coronary microvascular function by subendocardial viability ratio (derived from pulse wave analysis). Flow mediated vasodilation related inversely to SCORE (r =  0.34, P = 0.011). Adding microalbuminuria and pulse wave velocity strengthened the associations. Pulse wave reflection changes did not relate to SCORE. Skin microvascular reactivity related inversely to SCORE (peak flux change to sodium nitroprusside r =  0.29, P = 0.033, and to heating r =  0.31, P = 0.018). Subendocardial viability ratio did not relate to SCORE. Endothelial function indices showed no consistent relation to cardiac target organ damage. The agreement between the different methods for evaluating indices of macrovascular and microvascular endothelial function was weak. In conclusion, indices of macrovascular and microvascular endothelial function relate to cardiovascular mortality risk. Their use may improve cardiovascular risk prediction in hypertension. However, methods representing different vascular beds show little interrelationship and are not interchangeable, which may depend on different pathogenetic mechanisms representing different aspects of future cardiovascular risk.

Trial registry: NCT02901977

Levenberg-Marquardt Neural Network Algorithm for Degree of Arteriovenous Fistula Stenosis Classification Using a Dual Optical Photoplethysmography Sensor

This paper proposes a noninvasive dual optical photoplethysmography (PPG) sensor to classify the degree of arteriovenous fistula (AVF) stenosis in hemodialysis (HD) patients. Dual PPG measurement node (DPMN) becomes the primary tool in this work for detecting abnormal narrowing vessel simultaneously in multi-beds monitoring patients. The mean and variance of Rising Slope (RS) and Falling Slope (FS) values between before and after HD treatment was used as the major features to classify AVF stenosis. Multilayer perceptron neural networks (MLPN) training algorithms are implemented for this analysis, which are the Levenberg-Marquardt, Scaled Conjugate Gradient, and Resilient Back-propagation, to identify the degree of HD patient stenosis. Eleven patients were recruited with mean age of 77 ± 10.8 years for analysis. The experimental results indicated that the variance of RS in the HD hand between before and after treatment was significant difference statistically to stenosis (p < 0.05). Levenberg-Marquardt algorithm (LMA) was significantly outperforms the other training algorithm. The classification accuracy and precision reached 94.82% and 92.22% respectively, thus this technique has a potential contribution to the early identification of stenosis for a medical diagnostic support system.

Measurement of area difference ratio of Photoplethysmographic pulse wave in patients with pre-eclampsia

Background

Preeclampsia (PE) is associated with an increase in maternal arterial stiffness, which may be reflected by photoplethysmography (PPG) of the pulse wave. The aim of this study was to investigate area difference ratio (ADR), a novel parameter derived from PPG, in women with and without preeclampsia.

Methods

Patients with and without preeclampsia in the third trimester were enrolled. All patients had photoplethysmography of the pulse wave assessed. ADR was compared between the two groups.

Results

Seventy-two patients in the third trimester of gestation, of which 36 had preeclampsia and 36 did not, were enrolled. The ADR was lower in the preeclampsia group vs. the non-preeclampsia group (0.725 [IQR 0.681–0.779] vs. 0.752 [IQR 0.717–0.910], P < 0.01).

Conclusions

Measuring the ADR through analyzing PPG of the pulse wave may be a useful diagnostic tool in patients with preeclampsia.

Assessing mental stress from the photoplethysmogram: a numerical study

OBJECTIVE

Mental stress is detrimental to cardiovascular health, being a risk factor for coronary heart disease and a trigger for cardiac events. However, it is not currently routinely assessed. The aim of this study was to identify features of the photoplethysmogram (PPG) pulse wave which are indicative of mental stress.

APPROACH

A numerical model of pulse wave propagation was used to simulate blood pressure signals, from which simulated PPG pulse waves were estimated using a transfer function. Pulse waves were simulated at six levels of stress by changing the model input parameters both simultaneously and individually, in accordance with haemodynamic changes associated with stress. Thirty-two feature measurements were extracted from pulse waves at three measurement sites: the brachial, radial and temporal arteries. Features which changed significantly with stress were identified using the Mann-Kendall monotonic trend test.

MAIN RESULTS

Seventeen features exhibited significant trends with stress in measurements from at least one site. Three features showed significant trends at all three sites: the time from pulse onset to peak, the time from the dicrotic notch to pulse end, and the pulse rate. More features showed significant trends at the radial artery (15) than the brachial (8) or temporal (7) arteries. Most features were influenced by multiple input parameters.

SIGNIFICANCE

The features identified in this study could be used to monitor stress in healthcare and consumer devices. Measurements at the radial artery may provide superior performance than the brachial or temporal arteries. In vivo studies are required to confirm these observations.

A new method for the assessment of endothelial function with peripheral arterial volume

Background

Currently, many methodological approaches have been developed to assess peripheral endothelial function. However, a development of the noninvasive and automated technique for routinely assessing endothelial function is still required. We evaluated the potential value of a new method to measure peripheral endothelial function with reactive hyperemia peripheral arterial volume (RH-PAV) in patients with chest pain.

Methods

We used a novel oximeter-like probe to detect the peripheral arterial volume (PAV) of the finger and compared it with brachial flow-mediated dilation (FMD) performed in 93 consecutive patients with chest pain. The RH-PAV index was defined as the ratio of the digital pulse volume during reactive hyperemia relative to the baseline.

Results

Ninety-three patients (53 men, 58 ± 5 years) completed the study, and 53 patients demonstrated coronary artery disease (CAD) following scheduled coronary angiography. There was a moderate linear relationship between PAV and FMD (r = 0.69, p < 0.01). Similar to FMD, PAV was more impaired in patients who have more cardiovascular risk factors (CRFs). The subjects with CAD had lower PAV and FMD, compared with those without CAD (1.05 ± 0.23 VS. 1.41 ± 0.37, p < 0.01; 6.7% ± 2.9% VS. 10.4% ± 2.9%, p < 0.01, respectively), and the relationships between FMD and PAV were also significant in both CAD (r = 0.54, p < 0.01) and non-CAD (r = 0.62, p < 0.01) patients.

Conclusions

Endothelial function of digital artery assessed with the novel PAV method demonstrated a profile similar to that of brachial artery measured with FMD. The hyperemia PAV was decreased by factors which were considered to impair endothelial function, suggesting that PAV has the potential to be a novel method to study endothelial function.

Salbutamol-induced Decrease in Augmentation Index is Related to the Parallel Increase in Heart Rate

The change in augmentation index following salbutamol inhalation has been applied to evaluate endothelial function. We examined the contribution of salbutamol-induced increase in heart rate to the observed decrease in augmentation index. Haemodynamics were recorded using whole-body impedance cardiography and continuous pulse wave analysis from tonometric radial blood pressure. All subjects (n = 335, mean age 46, body mass index 26, 48% men) were without medications with cardiovascular influences. The effects of salbutamol inhalation (0.4 mg) versus the endothelium-independent agent nitroglycerin resoriblet (0.25 mg) were examined during passive head-up tilt, as the haemodynamic influences of these compounds depend on body position. Salbutamol decreased augmentation index by ~3-4% units in supine and upright positions. Although salbutamol moderately increased cardiac index (+4.5%) and decreased systemic vascular resistance (-8.5%), the significant haemodynamic explanatory factors for decreased augmentation index in multivariate analysis were increased supine heart rate, and increased upright heart rate and decreased ejection duration (p < 0.001 for all, r²  = 0.36-0.37). Sublingual nitroglycerin decreased supine and upright augmentation index by ~15% units and ~23% units, respectively. The haemodynamic explanatory factors for these changes in multivariate analysis were increased heart rate, reduced ejection duration and reduced systemic vascular resistance (p ≤ 0.021 for all, r²  = 0.22-0.34). In conclusion, the lowering influence of salbutamol on augmentation index may be largely explained by increased heart rate, suggesting that this effect may not predominantly reflect endothelial function.

On the impact of modelling assumptions in multi-scale, subject-specific models of aortic haemodynamics

Simulation of haemodynamics has become increasingly popular within the research community. Irrespective of the modelling approach (zero-dimensional (0D), one-dimensional (1D) or three-dimensional (3D)), in vivo measurements are required to personalize the arterial geometry, material properties and boundary conditions of the computational model. Limitations in in vivo data acquisition often result in insufficient information to determine all model parameters and, hence, arbitrary modelling assumptions. Our goal was to minimize and understand the impact of modelling assumptions on the simulated blood pressure, flow and luminal area waveforms by studying a small region of the systemic vasculature—the upper aorta—and acquiring a rich array of non-invasive magnetic resonance imaging and tonometry data from a young healthy volunteer. We first investigated the effect of different modelling assumptions for boundary conditions and material parameters in a 1D/0D simulation framework. Strategies were implemented to mitigate the impact of inconsistencies in the in vivo data. Average relative errors smaller than 7% were achieved between simulated and in vivo waveforms. Similar results were obtained in a 3D/0D simulation framework using the same inflow and outflow boundary conditions and consistent geometrical and mechanical properties. We demonstrated that accurate subject-specific 1D/0D and 3D/0D models of aortic haemodynamics can be obtained using non-invasive clinical data while minimizing the number of arbitrary modelling decisions.