From peripheral finger-derived pulse waveforms to aortic pressure waveform features: an application of a generalized transfer function

OBJECTIVE

Aortic (central) pressure features are associated with cardiovascular complications and can be algorithmically derived from non-invasive peripheral arterial waveforms. This has conventionally been performed with a pressure waveform (i.e., tonometry or oscillometry) rather than with the optical-based sensor (photoplethysmography (PPG)) that is predominantly used in wearable health devices. Extraction of aortic features from a peripheral PPG waveform has yet to be investigated. This study aims to compare aortic features extracted from peripheral arterial waveforms acquired with different sensor modalities using the same transfer function.

DESIGN AND METHOD

Radial tonometry (reference), finger volume-clamped PPG (Peňáz) and fingertip PPG waveforms were measured in participants (n=29, 36±16 years, 15 female) under baseline conditions. Waveforms were converted into an aortic pressure waveform using the transfer function. Waveform features were extracted from the converted waveform. Extracted features were compared with correlation plots and a Bland-Altman analysis.

RESULTS

Aortic pressure features extracted from a finger using the Peňáz technique were comparable to radial tonometry derived features. Aortic features extracted from a fingertip waveform were more variable in comparison to radial tonometry-derived features.

CONCLUSIONS

Aortic (central) pressure waveform features contain valuable haemodynamic information and have the capacity to be easily and conveniently implemented in wearable health devices. Future use of these features in wearable health devices incorporating PPG requires the development, and/or, optimization of a unique transfer function to more accurately represent the aortic pressure waveform for cardiovascular assessment.Clinical Relevance- Aortic pressure features might be used in wearable health devices following the development of a unique transfer function for optical-transduced peripheral vascular signals.

Positive association between triglyceride glucose index and central systolic blood pressure among hypertensive adults

BACKGROUND

While studies have suggested the association between triglyceride-glucose (TyG) index, a reliable surrogate for insulin resistance and hypertension data are limited to the correlation of TyG and central blood pressure. This study aims to test the hypothesis that a higher TyG index is associated with elevated central systolic blood pressure (cSBP).

METHODS

A total of 9249 Chinese hypertensive adults from the H-type Hypertension and Stroke Prevention and Control Project were analyzed in this study. cSBP was measured noninvasively using an A-Pulse CASPro device. TyG index was calculated as ln [fasting triglycerides (mg/dL) × fasting glucose (mg/dL)/2]. Smoothing curve and multivariate linear regression models [beta coefficient (β) with 95% CI] were applied to analyze the association between TyG index and cSBP. Subgroup analyses were conducted to explore potential modifications to such a correlation.

RESULTS

The overall mean TyG index is 8.8 ± 0.7, and the total mean cSBP is 131.3 ± 12.8 mmHg. TyG index was observed to be independently and positively associated with cSBP among the total population (β = 0.92, 95% CI: 0.53-1.31, P < 0.001), and participants who do not use antihypertensive drugs (β = 1.03, 95% CI: 0.46-1.60, P < 0.001), which is in accordance with the result of the smoothing curve. The association between TyG index and cSBP appears robust in all tested subgroups.

CONCLUSIONS

TyG index is positively and independently associated with cSBP among hypertensive adults. Our study result suggests that TyG index might serve as an effective marker for vascular function.

Simultaneous adaption of the gain and phase of a generalized transfer function for aortic pressure waveform estimation

GOAL

This paper proposes and validates a completely adaptive transfer function (CATF) based on an autoregressive exogenous (ARX) model which adjusts the gain and phase of a generalized transfer function (GTF) simultaneously to estimate the aortic pressure waveform from a brachial pressure waveform.

METHODS

Invasive aortic and brachial pressure waveforms were recorded from 34 subjects for the validation of the proposed method. Individual transfer functions (ITFs) were trained based on the pressure waveforms using an ARX model. The GTF was derived by averaging the ITFs. CATF was then obtained by adjusting both the gain and phase of the GTF using regression formulas calculated from the ITFs and brachial hemodynamic parameters. Meanwhile the quantitative contributions of the adaption of gain and phase of the GTF were investigated respectively. The root-mean-square-error of the total waveform and absolute errors of common hemodynamic indices including systolic and diastolic blood pressures (SBP and DBP, respectively), pulse pressure (PP) and augmentation index were used to evaluate the performance of the proposed method in the data divided into low, middle and high PP amplification groups.

RESULTS

The CATF achieved lower errors for DBP and PP in the low PP amplification group (1.79 versus 2.10 mmHg and 5.08 versus 6.23 mmHg, respectively, both P < 0.05) and PP in the middle amplification group (1.43 versus 1.92 mmHg, P < 0.05) compared with the GTF.

SIGNIFICANCE

The proposed method provides a step towards the development of an improved and clinically useful non-invasive approach for estimating the aortic pressure waveform from a peripheral pressure waveform.

Comparison between invasive and non-invasive assessment of blood pressure in hypertensive disorders of pregnancy

BACKGROUND

The management of hypertensive disorders of pregnancy (HDP) during hospitalization requires an accurate blood pressure (BP) measurement, mainly by invasive intra-arterial reading. Nevertheless, little is known about the precision of non-invasive (NI) central BP measurements in HDP. We aimed to assess the accuracy of NI central BP assessment in comparison to invasive BP measurement in HDP. This cross-sectional study included all patients with HDP that were admitted to university hospitals for high BP control, from December 2018 till December 2019, and 10 healthy matched non-hypertensive controls. Patients were compared for demographic, anthropometric, and echocardiographic data. In all subjects, invasive BP assessment was done by radial arterial cannulation and NI assessment of BP was performed by an oscillometric automated device (Mobil-O-Graph); the comparison was done after initial control of BP.

RESULTS

One hundred patients were included and divided into 3 groups (pre-existing hypertension (HTN), gestational HTN, and pre-eclampsia). There was no statistically significant difference between NI central and invasive methods in measuring both systolic BP (SBP) (126.39 ± 14.5 vs 127.43 ± 15.3, p = 0.5) and diastolic BP (82.41 ± 9.0 vs 83.78 ± 8.9, p = 0.14) among the total studied population. A strong positive correlation was found between NI central and invasive SBP (r = 0.96, p < 0.001). HDP was associated with an increase in arterial stiffness, left ventricular diastolic dysfunction, and complications.

CONCLUSION

Non-invasive measurement of BP using oscillometric automated devices is as accurate as the invasive method, and it is a practical safe method in pregnant women with hypertensive disorders (CTR no. = NCT04303871).

Cardiovascular Outcomes in the Acute Phase of COVID-19

The cumulative number of cases in the current global coronavirus disease 19 (COVID-19) pandemic, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has exceeded 100 million, with the number of deaths caused by the infection having exceeded 2.5 million. Recent reports from most frontline researchers have revealed that SARS-CoV-2 can also cause fatal non-respiratory conditions, such as fatal cardiovascular events. One of the important mechanisms underlying the multiple organ damage that is now known to occur during the acute phase of SARS-CoV-2 infection is impairment of vascular function associated with inhibition of angiotensin-converting enzyme 2. To manage the risk of vascular dysfunction-related complications in patients with COVID-19, it would be pivotal to clearly elucidate the precise mechanisms by which SARS-CoV-2 infects endothelial cells to cause vascular dysfunction. In this review, we summarize the current state of knowledge about the mechanisms involved in the development of vascular dysfunction in the acute phase of COVID-19.

Understanding Vascular Age: Are Clinical scoring systems useful for Early Vascular Aging Syndrome Prediction ?

INTRODUCTION

Early vascular aging syndrome (EVAS) is defined as increased arterial stiffness compared to age and sex matched patients, EVAS is measured by pulse wave velocity (PWV).

AIM

In our study we aim to identify in patients with high risk of EVAS using the CHADS2, CHA2DS2-VASc, and CHA2DS2-VASc-HS scores.

METHODS

The CHADS2, CHA2DS2-VASc-HS and CHADS2VASC scoring systems are advised to determine management strategies in patients with nonvalvular atrial fibrillation. As they contain similar risk factors for the development or presence of EVAS, we believed that this risk scoring system could also be used to predict EVAS. This study was designed as a retrospective observational study. 2108 consecutive patients who had undergone 24-h blood pressure monitoring and measured PWV levels were included in the study. The patients were divided into the two groups according to corrected Pwv values.

RESULTS

CHADS2, CHA2DS2-VASc, and CHA2DS2-VASc-HS scores were positively correlated with PWV values (r =0.251, p < 0.001; r = 0.457, p < 0.001; and r = 0.385, p < 0.001, respectively). CHA2DS2-VASc-HS score was statistically better than CHA2DS2, CHA2DS2-VASc score to predict early vascular aging syndrome (p < 0.001). For the prediction of EVAS, the cut-off value of CHA2DS2-VASc-HS score was ≥ 1.5 with a sensitivity of 49% and a specificity of 50 % (AUC 0.605; 95% [CI] 0.58-0.63) in the ROC curve analyses.

CONCLUSIONS

The CHA2DS2-VASc-HS scoring system might be used in daily clinical practice to calculate the total risk assessment of EVAS. This score is relatively simple to use and time-saving technique.

Changes to cardiovascular risk factors over 7 years: a prospective cohort study of in situ urbanised residents in the Chaoyang District of Beijing

OBJECTIVES

To examine changes in cardiovascular risk factors of in situ urbanised residents between 2010 and 2017.

DESIGN

Population-based cohort study.

SETTING

The Chaoyang District of Beijing, China.

PARTICIPANTS

A total of 942 in situ urbanised rural residents aged 35-64 who participated in the cardiovascular disease (CVD) risk factors study in China between 2010 and 2017.

MAIN OUTCOME MEASURES

Lifestyles (smoking, drinking and effective exercise) and medical history (diabetes, hypertension, dyslipidaemia, overweight and obesity) were self-reported. New cases of diabetes, hypertension, dyslipidaemia, overweight and obesity were confirmed by physical examination or blood biochemical tests. Multiple linear regression and log-binomial models analyses adjusted for sociodemographic confounders were conducted to evaluate any changes of clinical indexes and to estimate prevalence rate ratios (PRRs), respectively.

RESULTS

During the study period of 2010-2017, diastolic blood pressure elevated by 3.55 mm Hg, central blood pressure increased by 4.39 mm Hg, total cholesterol decreased by 0.29 mmol/L and hypertension increased significantly (PRR=1.25, p<0.05) after adjusting for demographic, lifestyle and family history factors. Effective exercise rate (PRR=1.57), prevalence of diabetes (PRR=1.36) and dyslipidaemia (PRR=1.19) all increased from 2010 to 2017. However, these changes were not significant after adjusting for confounders (p>0.05). Prevalence of smoking, drinking, hypertension, overweight and obesity was significantly higher in males than females in both 2010 and 2017. In 2017, the 10-year risk of atherosclerotic CVD increased in 29.8% of participants and decreased in 6.1% of individuals.

CONCLUSIONS

CVD risk factors augmented remarkably for in situ urbanised rural residents aged 35-64 in the Chaoyang District of Beijing, especially those indicators related to blood pressure. Awareness of the direction and magnitude of these risk factor changes may be beneficial in informing targeted strategies for preventing CVDs of in situ urbanised populations.

Effect of oral L-citrulline on brachial and aortic blood pressure defined by resting status: evidence from randomized controlled trials

Background

Experimental evidence indicates that oral L-citrulline (L-Cit) may reduce resting blood pressure (BP) as well as BP responses to exercise and cold exposure (non-resting). However, results from human intervention trials are inconsistent. This study aims to summarize the clinical evidence regarding the effects of L-Cit supplementation on brachial systolic blood pressure (SBP), brachial diastolic blood pressure (DBP), in addition to aortic SBP and aortic DBP at rest and non-resting conditions.

Methods

Multiple databases including PubMed, Embase, Cochrane library, Web of Science, and Clinical Trials were searched systematically. Randomized controlled trials of human participants were quantitatively meta-analyzed.

Results

Fourteen trials contained in eight studies were available for quantitative syntheses for brachial BP. Results showed that L-Cit supplementation significantly reduced both brachial SBP (− 4.490 mmHg, 95% CI: − 7.332 to − 1.648, P = 0.002) and brachial DBP (− 3.629 mmHg, 95% CI: − 5.825 to − 1.434, P = 0.001). Nine of the trials were meta-analyzed for aortic BP which showed that L-Cit intervention significantly reduced aortic SBP (− 6.763 mmHg, 95% CI: − 10.991 to − 2.534, P = 0.002), but not aortic DBP (− 3.396 mmHg, 95% CI: − 7.418 to 0.627, P = 0.098). The observed reducing effects of L-Cit appeared stronger for non-resting than for resting brachial SBP (P for difference = 0.044).

Conclusion

L-Cit supplementation significantly decreased non-resting brachial and aortic SBP. Brachial DBP was significantly lowered by L-Cit regardless of resting status. Given the relatively small number of available trials in the stratified analyses and the potential limitations of these trials, the present findings should be interpreted cautiously and need to be confirmed in future well-designed trials with a larger sample size.

The Role of Myokines and Adipokines in Hypertension and Hypertension-related Complications

The cross-talk between skeletal muscle and adipose tissue has been identified to play a key role in the regulation of blood pressure and the development of hypertension. The role of different adipokines and myokines in hypertension and hypertension-related complications remains unclear. In the present study, 98 hypertensive patients and 24 normotensive controls were recruited, and additional subgroup analyses of hypertension-related complications were also performed. The levels of the circulating bone-derived factors leptin, apelin, fractalkine, brain-derived neurotrophic factor (BDNF), leukemia inhibitory factor (LIF), myostatin, fatty-acid-binding protein 3 (FABP3), irisin, follistatin-related protein 1 (FSTL1), oncostatin M, fibroblast growth factor 21 (FGF21) and musclin were measured by a protein liquid chip assay. The circulating levels of BDNF and musclin were decreased, whereas the leptin and irisin levels were increased, in hypertensive patients compared with those in the control individuals. Further logistic analysis indicated that the irisin level was positively correlated with SBP and an independent predictor for hypertension after adjustment. In nonobese subjects, the concentrations of DKK1, BDNF and FSTL1 were decreased, whereas the concentrations of leptin and irisin were increased. Irisin and DKK1 might be associated with hypertension. Additional subgroup analyses showed that irisin is significantly associated with hypertension-related stroke. In conclusion, we found that increased irisin levels are associated with hypertension and hypertension-related stroke. These findings indicate that irisin may be involved in the pathophysiology of hypertension.

Vascular Mild Cognitive Impairment: Identifying Disease in Community-Dwelling Older Adults, Reducing Risk Factors, and Providing Support. The Osaki-Tajiri and Kurihara Projects

Vascular mild cognitive impairment (MCI) is a critical disease. Its prognosis includes not only onset of vascular dementia, but also death by cardiovascular disease. The vascular risk factors for vascular MCI are treatable, and appropriate treatment can prevent or delay the progression to dementia. Therefore, this group is an excellent candidate for secondary prevention. However, community-dwelling older adults with vascular MCI are often undetected and are not clinically identified until they develop frank dementia. Furthermore, older adults with undetected vascular MCI often have decreased ability to follow their medication regimens and this poor medication adherence worsens their vascular comorbidities. This vicious cycle needs to be prevented through community-based interventions. There is evidence that treatment of hypertension or diabetes mellitus could lead to a reduced incidence of vascular MCI and dementia. In this review article, we first explain the background and etiology of vascular MCI. We then summarize phenotype of subcortical vascular dementia which is often unrecognized or "hidden" in the community. Then we introduce the Osaki-Tajiri and Kurihara Projects which have been conducted in Northern Japan, as an example of prevention projects aimed to identify early-stage vascular MCI in the community, reduce the risk factors and facilitate their treatment. Early identification of vascular MCI in the community could lead to a large reduction in the dementia burden worldwide. The outreach efforts presented here could be useful in developing secondary prevention strategies targeted to vascular MCI.

Estimation of Cardiovascular Risk Predictors from Non-Invasively Measured Diametric Pulse Volume Waveforms via Multiple Measurement Information Fusion

This paper presents a novel multiple measurement information fusion approach to the estimation of cardiovascular risk predictors from non-invasive pulse volume waveforms measured at the body's diametric (arm and ankle) locations. Leveraging the fact that diametric pulse volume waveforms originate from the common central pulse waveform, the approach estimates cardiovascular risk predictors in three steps by: (1) deriving lumped-parameter models of the central-diametric arterial lines from diametric pulse volume waveforms, (2) estimating central blood pressure waveform by analyzing the diametric pulse volume waveforms using the derived arterial line models, and (3) estimating cardiovascular risk predictors (including central systolic and pulse pressures, pulse pressure amplification, and pulse transit time) from the arterial line models and central blood pressure waveform in conjunction with the diametric pulse volume waveforms. Experimental results obtained from 164 human subjects with a wide blood pressure range (systolic 144 mmHg and diastolic 103 mmHg) showed that the approach could estimate cardiovascular risk predictors accurately (r ≥ 0.78). Further analysis showed that the approach outperformed a generalized transfer function regardless of the degree of pulse pressure amplification. The approach may be integrated with already available medical devices to enable convenient out-of-clinic cardiovascular risk prediction.

Comparison of Central, Ambulatory, Home and Office Blood Pressure Measurement as Risk Markers for Mild Cognitive Impairment in Hypertensive Patients

Aims

We compared the role of central blood pressure (BP), ambulatory BP monitoring (ABPM), home-measured BP (HMBP) and office BP measurement as risk markers for the development of mild cognitive impairment (MCI).

Methods

70 hypertensive patients on combination medical therapy were studied. Their mean age was 64.97 ± 8.88 years. Eighteen (25.71%) were males and 52 (74.28%) females. All of the patients underwent full physical examination, laboratory screening, echocardiography, and office, ambulatory, home and central BP measurement. The neuropsychological tests used were: Mini Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA). SPSS 19 was used for the statistical analysis with a level of significance of 0.05.

Results

The mean central pulse pressure values of patients with MCI were significantly (p = 0.016) higher than those of the patients without MCI. There was a weak negative correlation between central pulse pressure and the results from the MoCA and MMSE (r = −0.283, p = 0.017 and r = −0.241, p = 0.044, respectively). There was a correlation between ABPM and MCI as well as between HMBP and MCI.

Conclusions

The correlation of central BP with target organ damage (MCI) is as good as for the other types of measurements of BP (home and ambulatory). Office BP seems to be the poorest marker for the assessment of target organ damage.

Association of elevated resting pulse rate with increased risk of hypertension development in children: A prospective study in Suzhou, China

BACKGROUND

Elevated resting heart rate (RHR) or resting pulse rate (RPR) is associated with increased risk of hypertension development. However, information is limited to adults. The purpose of this study is to analyze this association among Chinese children in a prospective design.

METHODS

A total of 4861 children who participated in the Blood Pressure Surveillance Program (2011-2017) were selected in this research. To investigate the association between RPR and hypertension development, children were divided into 4 groups according to the quartiles of RPR at baseline. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using logistic regression model.

RESULTS

Over a mean follow-up of 3.0 ± 0.1 years, there were 384 cases of incident hypertension. Compared to boys and girls in the 1st quartile, those in the 4th quartile were 1.73 (95% CI 1.13, 2.65), 2.22 (95% CI 1.43, 3.45) times more likely to have hypertension, respectively. Every 10 bpm increase in RPR was associated with a 26% greater risk of hypertension development in boys (OR: 1.26; 95% CI 1.10, 1.44), while this risk was 1.28 (95% CI 1.13, 1.44) in girls. Baseline blood pressure (BP) and body mass index (BMI) did not have significant interactions with RPR on risk of hypertension development.

CONCLUSION

This study confirms the relationship between elevated RPR and increased risk of hypertension development in children, independent of confounders including baseline BP and BMI. An elevated RPR could be considered as a risk factor for the assessment of hypertension, no matter from a clinical setting or a public health perspective.

Relationship between Resting Heart Rate, Blood Pressure and Pulse Pressure in Adolescents

Background:

High resting heart rate is considered an important factor for increasing mortality chance in adults. However, it remains unclear whether the observed associations would remain after adjustment for confounders in adolescents.

Objectives:

To analyze the relationship between resting heart rate, blood pressure and pulse pressure in adolescents of both sexes.

Methods:

A cross-sectional study with 1231 adolescents (716 girls and 515 boys) aged 14-17 years. Heart rate, blood pressure and pulse pressure were evaluated using an oscillometric blood pressure device, validated for this population. Weight and height were measured with an electronic scale and a stadiometer, respectively, and waist circumference with a non-elastic tape. Multivariate analysis using linear regression investigated the relationship between resting heart rate and blood pressure and pulse pressure in boys and girls, controlling for general and abdominal obesity.

Results:

Higher resting heart rate values were observed in girls (80.1 ± 11.0 beats/min) compared to boys (75.9 ± 12.7 beats/min) (p ≤ 0.001). Resting heart rate was associated with systolic blood pressure in boys (Beta = 0.15 [0.04; 0.26]) and girls (Beta = 0.24 [0.16; 0.33]), with diastolic blood pressure in boys (Beta = 0.50 [0.37; 0.64]) and girls (Beta = 0.41 [0.30; 0.53]), and with pulse pressure in boys (Beta = -0.16 [-0.27; -0.04]).

Conclusions:

This study demonstrated a relationship between elevated resting heart rate and increased systolic and diastolic blood pressure in both sexes and pulse pressure in boys even after controlling for potential confounders, such as general and abdominal obesity.

Fundamento:

A frequência cardíaca de repouso é considerada um importante fator de aumento de mortalidade em adultos. Entretanto, ainda é incerto se as associações observadas permanecem após ajuste para fatores de confusão em adolescentes.

Objetivos:

Analisar a relação entre frequência cardíaca de repouso, pressão arterial e pressão de pulso em adolescentes dos dois sexos.

Métodos:

Estudo transversal com 1231 adolescentes (716 meninas e 515 meninos, idade de 14-17 anos). Frequência cardíaca, pressão arterial e pressão de pulso foram avaliadas com esfigmomanômetro oscilométrico validado para essa população. Peso e altura foram medidos com balança eletrônica e estadiômetro, respectivamente, e a circunferência abdominal, com uma fita inextensível. Análise multivariada com regressão linear investigou a relação entre frequência cardíaca de repouso, pressão arterial e pressão de pulso em meninos e meninas, controlando para obesidade geral e abdominal.

Resultados:

Valores maiores de frequência cardíaca de repouso foram observados em meninas (80,1 ± 11,0 bpm) em comparação a meninos (75,9 ± 12,7 bpm) (p ≤ 0,001). Frequência cardíaca de repouso associou-se com pressão arterial sistólica em meninos [Beta = 0,15 (0,04; 0,26)] e meninas [Beta = 0,24 (0,16; 0,33)], com pressão arterial diastólica em meninos [Beta = 0,50 (0,37; 0,64)] e meninas [Beta = 0,41 (0,30; 0,53)], e com pressão de pulso apenas em meninos [Beta = -0,16 (-0,27; -0,04)].

Conclusões:

Este estudo demonstrou a relação da frequência cardíaca de repouso elevada com aumento das pressões arteriais sistólica e diastólica em ambos os sexos e com pressão de pulso em meninos, mesmo após controle para potenciais fatores de confusão, como obesidade geral e abdominal.

Investigation of Viscoelasticity in the Relationship Between Carotid Artery Blood Pressure and Distal Pulse Volume Waveforms

We investigated the relationship between carotid artery blood pressure (BP) and distal pulse volume waveforms (PVRs) via subject-specific mathematical modeling. We conceived three physical models to define the relationship: a tube-load model augmented with a gain (TLG), Voigt (TLV), and standard linear solid (TLS) models. We compared these models using PVRs measured via BP cuffs at an upper arm and an ankle as well as carotid artery tonometry waveform collected from 133 subjects. At both upper arm and ankle, PVR was related to carotid artery tonometry by TLV and TLS models better than by TLG model; when root-mean-squared over all the subjects, the systolic and diastolic BP errors between measured carotid artery tonometry waveform and the one estimated from distal PVR reduced from 4.3 mmHg and 4.6 mmHg (TLG) to 1.1 mmHg and 1.0 mmHg (TLS) for the upper arm (p < 0.0167), and from 2.1 mmHg and 1.7 mmHg (TLG) to 2.1 mmHg and 1.5 mmHg (TLV) for the ankle. Further, TLV and TLS models exhibited superior Akaike's Information Criterion (AIC) in both locations than TLG model. However, the difference between TLG versus TLV and TLS models associated with the ankle was not large. Therefore, the relationship of central arterial BP to arm PVR arises from both wave reflection and viscoelasticity while the relationship to ankle PVR mainly arises from wave reflection. These findings may imply that an effective subject-specific transfer function for estimating accurate central arterial BP from an arm PVR should account for the impact of viscoelasticity.

Effects of non-fat dairy products added to the routine diet on vascular function: a randomized controlled crossover trial

BACKGROUND AND AIMS

High consumption of low- and non-fat dairy products is associated with reduced risk of high blood pressure (BP) and central arterial stiffness. However, interventional studies to determine if the addition of non-fat dairy products to the diet is capable of reducing central BP and improving vascular function are lacking. The aim of this study was to determine if the solitary addition of non-fat dairy products to the normal routine diet would reduce central BP and improve vascular function in middle-aged and older adults with elevated BP.

METHODS AND RESULTS

Using a randomized, crossover intervention study design, forty-nine adults (44% men, 53 ± 2 years, 170 ± 2 cm, 88 ± 3 kg; mean ± SEM) with elevated BP (134 ± 1/81 ± 1 mm Hg) underwent a High Dairy condition (+4 servings/day of conventional non-fat dairy products) and No Dairy condition (+4 servings/day fruit products) in which all dairy products were removed. Both dietary conditions lasted 4 weeks with a 2-week washout before crossing over into the alternate condition. The High Dairy condition produced reductions in central systolic BP (-3 ± 1 mm Hg) and carotid-femoral pulse wave velocity (-0.5 ± 0.1 m/sec), with a concomitant increase in brachial flow-mediated dilation (+1.1 ± 0.4%) and cardiovagal baroreflex sensitivity (+5 ± 1 ms/mm Hg) (P < 0.05 for all vs. baseline). In the No Dairy condition, brachial flow-mediated dilation was reduced (-1.0 ± 0.1%, P < 0.05 vs. baseline).

CONCLUSIONS

The solitary manipulation of conventional dairy products in the normal routine diet modulates levels of central BP and vascular function in middle-aged and older adults with elevated BP.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01577030.

High Definition Oscillometry: Non-invasive Blood Pressure Measurement and Pulse Wave Analysis

Non-invasive monitoring of blood pressure has become increasingly important in research. High-Definition Oscillometry (HDO) delivers not only accurate, reproducible and thus reliable blood pressure but also visualises the pulse waves on screen. This allows for on-screen feedback in real time on data validity but even more on additional parameters like systemic vascular resistance (SVR), stroke volume (SV), stroke volume variances (SVV), rhythm and dysrhythmia. Since complex information on drug effects are delivered within a short period of time, almost stress-free and visible in real time, it makes HDO a valuable technology in safety pharmacology and toxicology within a variety of fields like but not limited to cardiovascular, renal or metabolic research.

Central Pulse Pressure and Variability in Matrix Metalloproteinases Genes and Their Inhibitors in Patients With Ischemic Heart Disease

Matrix metalloproteinases (MMPs) as well as their inhibitors (TIMPs) play a crucial role in controlling extracellular matrix turnover and have recently been associated with atherosclerosis, myocardial and vascular injury. Moreover, the genetic variability of MMP genes has been suggested to play an important role in vascular remodeling and age-related arterial stiffening. This study aims to describe associations of 14 selected polymorphisms in genes for MMPs and TIMPs with selected cardiovascular parameters (including central pulse pressure), clinical conditions and drug treatment profiles in 411 stable ischemic patients with preserved systolic function of the left ventricle. The genotyping of 14 single-nucleotide polymorphisms in 8 genes was carried out either using 5′ exonuclease (TaqMan®) reagents or by restriction analysis. Numerous associations of the investigated polymorphisms with systolic and diastolic blood pressure, maximum left ventricular end diastolic pressure and ejection fraction were observed. While some of the observed effects were found to be age-dependent, associations with clinical conditions (hypertension, diabetes mellitus, angina pectoris) were only observed in women and associations with four groups of drugs (statins, nitrates, calcium channel blockers, anti-aggregation drugs) were only observed in men. The results of this study indicate that the genetic variability of MMPs and TIMPs is an important factor which influences cardiovascular functions and may have important consequences for individual therapy customization in the future.

Nebivolol reduces central blood pressure in stage I hypertensive patients: experimental single cohort study

CONTEXT AND OBJECTIVES

Assessment of central blood pressure (BP) has grown substantially over recent years because evidence has shown that central BP is more relevant to cardiovascular outcomes than peripheral BP. Thus, different classes of antihypertensive drugs have different effects on central BP despite similar reductions in brachial BP. The aim of this study was to investigate the effect of nebivolol, a β-blocker with vasodilator properties, on the biochemical and hemodynamic parameters of hypertensive patients.

DESIGN AND SETTING

Experimental single cohort study conducted in the outpatient clinic of a university hospital.

METHODS

Twenty-six patients were recruited. All of them underwent biochemical and hemodynamic evaluation (BP, heart rate (HR), central BP and augmentation index) before and after 3 months of using nebivolol.

RESULTS

88.5% of the patients were male; their mean age was 49.7 ± 9.3 years and most of them were overweight (29.6 ± 3.1 kg/m2) with large abdominal waist (102.1 ± 7.2 cm). There were significant decreases in peripheral systolic BP (P = 0.0020), diastolic BP (P = 0.0049), HR (P < 0.0001) and central BP (129.9 ± 12.3 versus 122.3 ± 10.3 mmHg; P = 0.0083) after treatment, in comparison with the baseline values. There was no statistical difference in the augmentation index or in the biochemical parameters, from before to after the treatment.

CONCLUSIONS

Nebivolol use seems to be associated with significant reduction of central BP in stage I hypertensive patients, in addition to reductions in brachial systolic and diastolic BP.

Comparison of high-definition oscillometry -- a non-invasive technology for arterial blood pressure measurement -- with a direct invasive method using radio-telemetry in awake healthy cats

This study compared indirect blood pressure measurements using a non-invasive method, high-definition oscillometry (HDO), with direct measurements using a radio-telemetry device in awake cats. Paired measurements partitioned to five sub-ranges were collected in six cats using both methods. The results were analysed for assessment of correlation and agreement between the two methods, taking into account all pressure ranges, and with data separated in three sub-groups, low, normal and high ranges of systolic (SBP) and diastolic (DBP) blood pressure. SBP data displayed a mean correlation coefficient of 0.92 ± 0.02 that was reduced for low SBP. The agreement level evaluated from the whole data set was high and slightly reduced for low SBP values. The mean correlation coefficient of DBP was lower than for SBP (ie, 0.81 ± 0.02). The bias for DBP between the two methods was 22.3 ± 1.6 mmHg, suggesting that HDO produced lower values than telemetry. These results suggest that HDO met the validation criteria defined by the American College of Veterinary Internal Medicine consensus panel and provided a faithful measurement of SBP in conscious cats. For DBP, results suggest that HDO tended to underestimate DBP. This finding is clearly inconsistent with the good agreement reported in dogs, but is similar to outcomes achieved in marmosets and cynomolgus monkeys, suggesting that this is not related to HDO but is species related. The data support that the HDO is the first and only validated non-invasive blood pressure device and, as such, it is the only non-invasive reference technique that should be used in future validation studies.

Effects of resistance training on central blood pressure in obese young men

Central blood pressure is a predictor of the risk of cardiovascular disease (CVD), and the effects of resistance training (RT) on central blood pressure are largely unknown. This study explored the effects of high-intensity RT on central blood pressure, indices of arterial stiffness and wave reflection and inflammatory/atherogenic markers in overweight or obese, sedentary young men. Thirty-six participants were randomized to RT (12 weeks of training, 3/wk, n=28) or control groups (C, 12 weeks of no training, n=8) and assessed for changes in central and brachial blood pressures, augmentation index (AIx), carotid-femoral pulse wave velocity (cfPWV), carotid intima-media thickness (cIMT), body composition, lipids and inflammatory/atherogenic markers. High-intensity RT resulted in decreased central and brachial systolic/diastolic blood pressures (all P0.03), despite not altering AIx (P=0.34) or cfPWV (P=0.43). The vascular endothelial growth factor increased (P=0.03) after RT, without any change in cIMT, C-reactive protein, oxidized LDL (oxLDL) or other inflammatory markers (all P0.1). Changes in the central systolic blood pressure (cSBP) were positively correlated with changes in oxLDL (r=0.42, P=0.03) and soluble E-selectin (r=0.41, P=0.04). In overweight/obese young men, high-intensity RT decreases cSBP, independently of weight loss and changes in arterial stiffness. The cardioprotective effects of RT may be related to effects on central blood pressure.

Effectiveness of the direct renin inhibitor, aliskiren, in patients with resistant hypertension

Currently there is no consensus regarding which add-on therapy to use in resistant hypertension. We have conducted an open observational study of the use of aliskiren in resistant hypertensive patients. Forty-three patients with resistant hypertension were included in the study. The inclusion criteria were as follows: 1) office blood pressure (BP) > 140/90 mmHg despite treatment with at least three or more antihypertensive drugs; 2) no prior therapy with aliskiren; and 3) no renal insufficiency. Follow-up BP was determined at 1 and 3 months. Baseline BP was 153 ± 12/79 ± 12 mmHg. After 3 months, systolic BP (SBP) and diastolic BP (DBP) dropped significantly: 140 ± 19/73 ± 13 mmHg (P < 0.0001). Twenty-one patients (49%) had an office BP < 140/90 mmHg, and these patients were assigned to the good BP control group. Another 22 were placed into the poor BP control group. BP reductions from baseline in the good BP control group (SBP/ DBP: 19 ± 11/8 ± 7 mmHg) were larger than those in the poor BP control group (5 ± 15/3 ± 9 mmHg, P < 0.05). Mean BP (MBP) values at baseline, 1, and 3 months were higher in the poor BP control group. There was no significant difference in pulse pressure at baseline between the 2 groups. In multivariate analysis, only MBP at baseline correlated with lack of BP control. Aliskiren administration to resistant hypertensive patients was effective in reducing BP. The present findings suggest aliskiren may be useful as a fourth-line or fifth-line treatment added to other drugs in the treatment of resistant hypertension.

Decreased expression of γ-carboxylase in diabetes-associated arterial stiffness: impact on matrix Gla protein

AIMS

Arterial stiffness is accelerated in type 1 diabetic patients. Medial artery calcification (MAC) contributes to the development of arterial stiffness. Vitamin K oxidoreductase (VKOR) reduces the vitamin K required by γ-carboxylase to activate matrix γ-carboxyglutamic acid (Gla) protein (MGP), an inhibitor of vascular calcification. This study aimed to evaluate the hypothesis that diabetes reduces the γ-carboxylation of MGP in the aortic wall, leading to increased vascular calcification, and the role of γ-carboxylase and VKOR in this γ-carboxylation deficit.

METHODS AND RESULTS

Type 1 diabetes was induced in male Wistar rats with a single ip injection of streptozotocin. Augmentation of arterial stiffness in diabetic rats was shown by a 44% increase in aortic pulse wave velocity. Aortic and femoral calcification were increased by 26 and 56%, respectively. γ-Carboxylated MGP (cMGP, active) was reduced by 36% and the aortic expression of γ-carboxylase was reduced by 58%. Expression of γ-carboxylase correlated with cMGP (r= 0.59) and aortic calcification (r = -0.57). VKOR aortic expression and activity were not modified by diabetes. Vitamin K plasma concentrations were increased by 191% in diabetic rats. In ex vivo experiments with aortic rings, vitamin K supplementation prevented the glucose-induced decrease in γ-carboxylase expression.

CONCLUSION

Our results suggest that reduced cMGP, through an impaired expression of γ-carboxylase, is involved in the early development of MAC in diabetes, and therefore, in the acceleration of arterial stiffness. A defect in vitamin K uptake by target cells could also be involved.

Aortic pulse pressure is associated with the localization of coronary artery disease based on coronary flow lateralization

BACKGROUND

Aortic pulse pressure (APP) is related to arterial stiffness and associated with the presence and extent of coronary artery disease (CAD). Besides, the left coronary artery (LCA) has a predominantly diastolic flow while the right coronary artery (RCA) receives systolic and diastolic flow. Thus, we hypothesized that increased systolic-diastolic pressure difference had a greater atherogenic effect on the RCA than on the LCA.

METHODS

A random sample of 433 CAD patients (145 females, 288 males, mean age 65.0 ± 11.1 years) undergoing coronary angiography at Staten Island University Hospital between January 2005 and May 2008 was studied. Coronary lesion was defined as a ≥50% luminal stenosis. Patients were divided into three groups, with isolated LCA lesions (n = 154), isolated RCA lesions (n = 36) or mixed LCA and RCA lesions (n = 243).

RESULTS

APP differed significantly between groups, being highest when the RCA alone was affected (67.6 ± 20.3 mm Hg for LCA vs. 78.8 ± 22.0 for RCA vs. 72.7 ± 22.6 for mixed, P = 0.008 for analysis of variance (ANOVA)). Age and gender were not associated with CAD location. Heart rate was associated with CAD location, lowest in RCA group, and negatively correlated with APP. However, left ventricular ejection fraction (LVEF) was lower in the mixed CAD group and positively correlated with APP. The association between APP and right-sided CAD persisted in multivariate logistic regression adjusting for confounders, including heart rate, LVEF and medication use. A similar but less significant pattern was seen with brachial arterial pressures.

CONCLUSIONS

Aortic pulse pressure may affect CAD along with coronary flow phasic patterns.

The evolution and refinement of traditional risk factors for cardiovascular disease

Traditional risk factors for cardiovascular disease such as systemic hypertension and hypercholesterolemia, all described more than half a century ago, are relatively few in number. Efforts to expand the epidemiologic canon have met with limited success because of the high hurdle of causality. Fortunately, another solution to current deficiencies in risk assessment-in particular, the underestimation of risk both before and after initiation of pharmacotherapy-may exist. Parallel to the investigation of novel biomarkers, such as high-sensitivity C-reactive protein, ongoing research has yielded improved metrics of known causative conditions. This evolution of traditional risk factors, heralded by measures such as ambulatory blood pressure, central hemodynamics, low density lipoprotein particle concentration, genetic testing, and "vascular age," may better address the detection gap in cardiovascular disease.

Benefits of once-daily therapies in the treatment of hypertension

In patients with hypertension, 24-hour blood pressure control is the major therapeutic goal. The number of daily doses is one characteristic of an antihypertensive agent that may affect the adequacy of 24-hour control. One measure of therapeutic coverage is the 24-hour trough-to-peak ratio, which determines the suitability of an agent for once-daily administration. The closer an agent is to a 100% trough-to-peak ratio, the more uniform the 24-hour coverage and therefore blood pressure control. High trough-to-peak ratio, long-acting antihypertensive medications lower blood pressure more gradually, which reduces the likelihood of adverse events attributable to abrupt drug action that occurs with shorter-acting agents. In hypertension, the natural diurnal variation of blood pressure may be altered, including elevated nighttime pressures. An optimal once-daily hypertension therapy would not only lower blood pressure but also normalize any blunted circadian variations in blood pressure. The benefits of once-daily agents with sustained therapeutic coverage may also be explained, in part, by increased patient adherence to simpler regimens as well as lower loss of blood pressure control during virtually inevitable intermittent noncompliance. Studies have demonstrated that once-daily antihypertensive agents have the highest adherence compared with twice-daily or multiple daily doses, including greater adherence to the prescribed timing of doses.

Arterial stiffness, central hemodynamics, and cardiovascular risk in hypertension

This review summarizes several scientific contributions at the recent Satellite Symposium of the European Society of Hypertension, held in Milan, Italy. Arterial stiffening and its hemodynamic consequences can be easily and reliably measured using a range of noninvasive techniques. However, like blood pressure (BP) measurements, arterial stiffness should be measured carefully under standardized patient conditions. Carotid-femoral pulse wave velocity has been proposed as the gold standard for arterial stiffness measurement and is a well recognized predictor of adverse cardiovascular outcome. Systolic BP and pulse pressure in the ascending aorta may be lower than pressures measured in the upper limb, especially in young individuals. A number of studies suggest closer correlation of end-organ damage with central BP than with peripheral BP, and central BP may provide additional prognostic information regarding cardiovascular risk. Moreover, BP-lowering drugs can have differential effects on central aortic pressures and hemodynamics compared with brachial BP. This may explain the greater beneficial effect provided by newer antihypertensive drugs beyond peripheral BP reduction. Although many methodological problems still hinder the wide clinical application of parameters of arterial stiffness, these will likely contribute to cardiovascular assessment and management in future clinical practice. Each of the abovementioned parameters reflects a different characteristic of the atherosclerotic process, involving functional and/or morphological changes in the vessel wall. Therefore, acquiring simultaneous measurements of different parameters of vascular function and structure could theoretically enhance the power to improve risk stratification. Continuous technological effort is necessary to refine our methods of investigation in order to detect early arterial abnormalities. Arterial stiffness and its consequences represent the great challenge of the twenty-first century for affluent countries, and "de-stiffening" will be the goal of the next decades.

Increased arterial stiffness weakens the relationship between wave reflection and the central pressure indexes in men younger than 60 years of age

BACKGROUND

Interactions among age, arterial stiffness, and pressure wave reflection affect the central blood pressure (CBP). We evaluated our hypothesis that the contribution of the wave reflection to the CBP indexes is reduced at higher levels of arterial stiffness, independent of the effect of age.

METHODS

In 2,691 Japanese men aged <60 years old who are not suffering from cardiovascular disease or receiving medications for cardiovascular risk factors, the brachial-ankle pulse wave velocity (PWV), radial augmentation index (AI), and second peak of the radial pressure waveform (SBP2), a marker of CBP, were measured.

RESULTS

The increase in the radial AI associated with increase of the brachial-ankle PWV became attenuated at brachial-ankle PWV values of ≥15 m/s. Stepwise multivariate linear regression analysis demonstrated that 33.6% of the total variation in the value of SBP2 and 54.0% of the total variation in the value of the SBP2 minus the diastolic blood pressure, a marker of the central pulse pressure (CPP), were accounted for by the change of the radial AI in the group with brachial-ankle PWV values of <15 m/s, with the corresponding percentages of 16.2 and 38.0% in the group with brachial-ankle PWV values of ≥15 m/s (P < 0.01).

CONCLUSIONS

In non-elderly Japanese men, the contribution of the wave reflection to the CBP indexes may be reduced in subjects with higher levels of arterial stiffness, independent of the effect of age. Notwithstanding, the wave reflection may still be the major determinant of the CPP at any given level of arterial stiffness.

Calibration mode influences central blood pressure differences between SphygmoCor and two newer devices, the Arteriograph and Omron HEM-9000

The objective of this study was to compare central systolic blood pressure (cSBP) and augmentation index (AIx) from two recently introduced devices, Omron HEM-9000 (OM) and Arteriograph (AG), not using a transfer function with those of the widely used SphygmoCor (SC) calibrated on brachial blood pressure like OM. Random-order manufacturer-recommended measurements using SC and OM by radial tonometry and AG were taken on the left arm in 35 men (54±10 years) after 5 min supine rest. Results are means (95% confidence interval) of differences using paired t-tests. cSBP by OM was 4.1 (1.0-7.1) mm Hg higher than by AG. Both OM and AG estimated the mean cSBP to be significantly higher than did SC (114.8 mm Hg) by 12.5 (10.3-14.7) and 8.6 (4.9-12.3) mm Hg, respectively, although closely correlating with SC (r=0.9). Calibrating SC with diastolic blood pressure (DBP) and more accurate mean arterial pressure (as DBP+0.4 × PP) resulted in significantly higher cSBP statistically not different from AG's cSBP: 0.9 (-1.1 to +2.9) mm Hg, and closer to OM's: 5.1 (3.4-6.8) mm Hg. Radial AIx from SC and OM disagreed by 3 (0.7-5.4)%, and correlated (r=0.8) with AG's brachial AIx. AG's aortic AIx was 7.9 (5.7-10.2)% higher than SC's, but closely correlated (r=0.9). Clinically significant, higher cSBP measured by AG, OM and more accurately calibrated SC adds to previous data suggesting that SC measurements by classic calibration underestimate cSBP. Invasive studies involving all three devices would be more illuminating.

An angiotensin II- and NF-kappaB-dependent mechanism increases connexin 43 in murine arteries targeted by renin-dependent hypertension

AIMS

Connexins (Cxs) play a role in the contractility of the aorta wall. We investigated how connexins of the endothelial cells (ECs; Cx37, Cx40) and smooth muscle cells (SMCs; Cx43, Cx45) of the aorta change during renin-dependent and -independent hypertension.

METHODS AND RESULTS

We subjected both wild-type (WT) mice and mice lacking Cx40 (Cx40(-/-)), to either a two-kidney, one-clip procedure or to N-nitro-l-arginine-methyl-ester treatment, which induce renin-dependent and -independent hypertension, respectively. All hypertensive mice featured a thickened aortic wall, increased levels of Cx37 and Cx45 in SMC, and of Cx40 in EC (except in Cx40(-/-) mice). Cx43 was up-regulated, with no effect on its S368 phosphorylation, only in the SMCs of renin-dependent models of hypertension. Blockade of the renin-angiotensin system of Cx40(-/-) mice normalized blood pressure and prevented both aortic thickening and Cx alterations. Ex vivo exposure of WT aortas, carotids, and mesenteric arteries to physiologically relevant levels of angiotensin II (AngII) increased the levels of Cx43, but not of other Cx. In the aortic SMC line of A7r5 cells, AngII activated kinase-dependent pathways and induced binding of the nuclear factor-kappa B (NF-kappaB) to the Cx43 gene promoter, increasing Cx43 expression.

CONCLUSION

In both large and small arteries, hypertension differently regulates Cx expression in SMC and EC layers. Cx43 is selectively increased in renin-dependent hypertension via an AngII activation of the extracellular signal-regulated kinase and NF-kappaB pathways.

Blood pressure and vascular calcification

The aim of this study was to determine the associations between the presence and extent of calcified atherosclerosis in multiple vascular beds and systolic blood pressure, diastolic blood pressure, pulse pressure, mean arterial pressure, isolated systolic hypertension, and hypertension. A total of 9510 patients (42.5% women) underwent electron beam computed tomography scanning as part of a routine health maintenance screening. At the same visit, blood pressure was measured with the participant in the seated position using a mercury sphygmomanometer. Mean age was 58+/-11.4 years, and body mass index was 27.1+/-4.5. The prevalences of any calcification in the carotids, coronaries, subclavians, thoracic aorta, abdominal aorta, and iliacs were 31.9%, 57.2%, 31.7%, 37.0%, 54.3%, and 48.8%, respectively. In separate multivariable logistic models containing traditional cardiovascular disease risk factors, pulse pressure and systolic blood pressure were significantly associated with the presence of calcification in all of the vascular beds except the iliacs and subclavians, respectively, with pulse pressure having stronger magnitudes of the associations for most of the vascular beds. Age-stratified analyses indicated that these associations were stronger in those >60 years of age compared with subjects <60 years of age, and sex-stratified analyses demonstrated that men had a greater association compared with women. Also, the magnitudes of the associations for isolated systolic hypertension were, in general, larger than those for hypertension. Pulse pressure and isolated systolic hypertension are robust and important correlates for calcified atherosclerosis in different vascular beds. Isolated systolic hypertension may be clinically relevant in diagnosing or preventing calcified atherosclerosis.