Comparison of two noninvasive devices for measurement of central systolic blood pressure with invasive measurement during cardiac catheterization

Afterload reduction after non-invasive vagus nerve stimulation in acute heart failure

Introduction

While central blood pressure (BP) has been recognized as a major indicator of left ventricular (LV) afterload, the reduction of central pressure decreases LV afterload and may prevent heart failure (HF) decompensation. Non-invasive transcutaneous vagus nerve stimulation (tVNS) was shown to improve cardiac function in HF patients. In this study, the relationship between active tVNS and reduction of central BP was investigated in patients with acute HF (AHF).

Methods

The 22 patients hospitalized for AHF after initial stabilization (median 80 yrs, males 60%) were randomly assigned to active or sham group. For 1 h daily over 5 days, low-level transcutaneous electrical stimulation (LLTS) (20 Hz, 1 mA) was performed after attaching an ear clip to the tragus (active group) or the earlobe (sham control group). Before and after stimulation, central aortic systolic pressure (CASP), brachial systolic BP (SBP), diastolic BP (DBP) as well as heart rate (HR) were noninvasively measured.

Results

No significant differences in baseline characteristics were observed between the active and sham groups. In the active group, CASP, SBP, DBP, and HR each decreased significantly after stimulation (all p < 0.05), whereas in the sham group, CASP, SBP, DBP, and HR each increased significantly after stimulation (all p < 0.05). All the changes in CASP, SBP, DBP and HR before and after stimulation were also significantly different between active and sham groups (all p < 0.01). There were no device-related side effects.

Conclusion

In this study, the left tragus tVNS resulted in an acute afterload reduction in the elderly AHF patients. Non-invasive LLTS may be useful and safe for reducing afterload in AHF.

Clinical trial registration

ClinicalTrials.gov, identifier UMIN000044121.

Personalized aortic pressure waveform estimation from brachial pressure waveform using an adaptive transfer function

BACKGROUND AND OBJECTIVE

The aortic pressure waveform (APW) provides reliable information for the diagnosis of cardiovascular disease. APW is often measured using a generalized transfer function (GTF) applied to the peripheral pressure waveform acquired noninvasively, to avoid the significant risks of invasive APW acquisition. However, the GTF ignores various physiological conditions, which affects the accuracy of the estimated APW. To solve this problem, this study utilized an adaptive transfer function (ATF) combined with a tube-load model to achieve personalized and accurate estimation of APW from the brachial pressure waveform (BPW).

METHODS

The proposed method was validated using APWs and BPWs from 34 patients. The ATF was defined using a tube-load model in which pulse transit time and reflection coefficients were determined from, respectively, the diastolic-exponential-pressure-decay of the APW and a piece-wise constant approximation. The root-mean-square-error of overall morphology, mean absolute errors of common hemodynamic indices (systolic blood pressure, diastolic blood pressure and pulse pressure) were used to evaluate the ATF.

RESULTS

The proposed ATF performed better in estimating diastolic blood pressure and pulse pressure (1.63 versus 1.94 mmHg, and 2.37 versus 3.10 mmHg, respectively, both P < 0.10), and produced similar errors in overall morphology and systolic blood pressure (3.91 versus 4.24 mmHg, and 2.83 versus 2.91 mmHg, respectively, both P > 0.10) compared to GTF.

CONCLUSION

Unlike the GTF which uses fixed parameters trained on existing clinical datasets, the proposed method can achieve personalized estimation of APW. Hence, it provides accurate pulsatile hemodynamic measures for the evaluation of cardiovascular function.

Wave reflection quantification analysis and personalized flow wave estimation based on the central aortic pressure waveform

Pulse wave reflections reflect cardiac afterload and perfusion, which yield valid indicators for monitoring cardiovascular status. Accurate quantification of pressure wave reflections requires the measurement of aortic flow wave. However, direct flow measurement involves extra equipment and well-trained operator. In this study, the personalized aortic flow waveform was estimated from the individual central aortic pressure waveform (CAPW) based on pressure-flow relations. The separated forward and backward pressure waves were used to calculate wave reflection indices such as reflection index (RI) and reflection magnitude (RM), as well as the central aortic pulse transit time (PTT). The effectiveness and feasibility of the method were validated by a set of clinical data (13 participants) and the Nektar1D Pulse Wave Database (4,374 subjects). The performance of the proposed personalized flow waveform method was compared with the traditional triangular flow waveform method and the recently proposed lognormal flow waveform method by statistical analyses. Results show that the root mean square error calculated by the personalized flow waveform approach is smaller than that of the typical triangular and lognormal flow methods, and the correlation coefficient with the measured flow waveform is higher. The estimated personalized flow waveform based on the characteristics of the CAPW can estimate wave reflection indices more accurately than the other two methods. The proposed personalized flow waveform method can be potentially used as a convenient alternative for the measurement of aortic flow waveform.

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.

Ambulatory monitoring of central arterial pressure, wave reflections, and arterial stiffness in patients at cardiovascular risk

This paper reviews current 24 h ambulatory noninvasive technologies for pulse wave analysis (PWA) providing central arterial pressure, pulse wave velocity, and augmentation index and the scientific evidence supporting their use in the clinical management of patients with arterial hypertension or at risk for cardiovascular complications.The most outstanding value of these techniques lies in the fact that they are user-friendly, mostly operator independent, and enable the evaluation of vascular function during daily-life conditions, allowing to obtain repeated measurements in different out-of-office circumstances, less artificial than those of the laboratory or doctor's office.Studies performed so far suggest that 24 h PWA may represent a potentially promising tool for evaluating vascular function, structure, and damage in daily-life conditions and promoting early screening in subjects at risk. The current evidence in favor of such an approach in the clinical practice is still limited and does not recommend its routine use. In particular, at the moment, there is a shortage of long-term prognostic studies able to support the predictive value of 24 h PWA. Finally, the accuracy of the measures is strongly dependent on the type of technology and device employed with lack of interoperability among the devices that deeply affects comparability of results among studies using different technologies. It is thus mandatory in the near future to promote proper validation studies, for instance using the ARTERY protocol, and to plan well-designed long-term longitudinal studies that may prove the accuracy and high predictive value of PWA in ambulatory conditions.

Spironolactone Reduces Aortic Stiffness in Patients With Resistant Hypertension Independent of Blood Pressure Change

Background

Aortic stiffness is an independent predictor of cardiovascular events in patients with arterial hypertension. Resistant hypertension is often linked to hyperaldosteronism and associated with adverse outcomes. Spironolactone, a mineralocorticoid receptor antagonist, has been shown to reduce both the arterial blood pressure (BP) and aortic stiffness in resistant hypertension. However, the mechanism of aortic stiffness reduction by spironolactone is not well understood. We hypothesized that spironolactone reduces aortic stiffness in resistant hypertension independently of BP change.

Methods and Results

Patients with uncontrolled BP (≥140/90 mm Hg) despite use of ≥3 antihypertensive medications (including diuretics) were prospectively recruited. Participants were started on spironolactone at 25 mg/d, and increased to 50 mg/d at 4 weeks while other antihypertensive medications were withdrawn to maintain constant mean BP. Phase‐contrast cardiac magnetic resonance imaging of the ascending aorta was performed in 30 participants at baseline and after 6 months of spironolactone treatment to measure aortic pulsatility, distensibility, and pulse wave velocity. Pulse wave velocity decreased (6.3±2.3 m/s to 4.5±1.8 m/s, P<0.001) and pulsatility and distensibility increased (15.9%±5.3% to 22.1%±7.9%, P<0.001; and 0.28%±0.10%/mm Hg to 0.40%±0.14%/mm Hg, P<0.001, respectively) following 6 months of spironolactone.

Conclusions

Our results suggest that spironolactone improves aortic properties in resistant hypertension independently of BP, which may support the hypothesis of an effect of aldosterone on the arterial wall. A larger prospective study is needed to confirm our findings.

Comparison of a tonometric with an oscillometric blood pressure monitoring device over 24 hours of ambulatory use

PURPOSE

Multiple devices capable of measuring ambulatory blood pressure without cuffs have been recently developed and it is required that they offer high-accuracy measurements. The purpose of this prospective study was to compare the performance of a tonometric blood pressure monitor with that of an oscillometric cuff-based device used as a reference in healthy and hypertensive subjects over 24 hours of ambulatory use.

MATERIALS AND METHODS

Conventional oscillometric cuff-based device (Oscar 2; Sun Tech Medical) was placed in the left arm of 33 subjects, and a watch-type device based on the tonometric method (Bpro; HealthSTATS International, Singapore) was positioned in the right wrist. Both devices were synchronized to measure simultaneously over 24 hours.

RESULTS

The difference between the means over 24 hours of the oscillometric and the tonometric devices was -0.9 mmHg for SBP and -4.5 mmHg for DBP; the standard deviations were 14.7 and 12.2 mmHg, respectively. Greater differences in bias and dispersion were observed overnight than during the daytime. The accuracy of the tonometric device for diagnosing hypertension was 75% and for detecting the non-dipper profile, 48%.

CONCLUSION

The test device presented a high disagreement (especially during the night) compared to the oscillometric cuff-based device against which it was initially calibrated. This disagreement resulted in limited accuracy for diagnosing patients with suspected arterial hypertension and detecting non-dipper profiles.

Age-specific association between invasively measured central blood pressure and left ventricular mass index

Background: The impact of age on the association between central aortic hemodynamics and left ventricular (LV) remodeling has not been well elucidated. We compared the relationship between measurements of central blood pressure (CBP) and LV mass index (LVMI) according to their ages (<50 years versus ≥50 years). Methods: A total of 305 consecutive subjects (64.4 ± 10.9 years, 60.7% males) who underwent invasive coronary angiography (ICA) for the evaluation of coronary artery disease were prospectively enrolled. Just before ICA, CBP was measured at the aortic root using a pig-tail catheter, and CBP indices, including aortic systolic blood pressure (aSBP), aortic pulse pressure (aPP), aortic fractional pulse pressure (=aPP/mean aortic pressure), and aortic pulsatility index (=aPP/diastolic aortic pressure), were recorded. All subjects underwent transthoracic echocardiography, and LVMI was measured on the same day of ICA. Results: In simple linear correlation analyses, LVMI was associated with all CBP indices in subjects aged <50 years (n = 29) (P < .05 for each), but not in those aged ≥50 years (n = 276) (P > .05 for each). In the younger age group (≤50 years), multivariable analysis showed that aSBP (β = 0.457, P= .021) and aPP (β = 0.610, P= .006) had a significant association with LVMI after adjusting for possible confounding factors. The results remained consistent even when analyzed in a 1:1 propensity score-matched cohort. In conclusion, invasively measured aPP showed the closest association with LVMI in subjects aged <50 years, but not those aged ≥50 years. Conclusion: Aortic pulsatile hemodynamic status appears to have a greater effect on LV remodeling in younger people than in older people.

Identifying Isolated Systolic Hypertension From Upper-Arm Cuff Blood Pressure Compared With Invasive Measurements

Isolated systolic hypertension (ISH) is the most common form of hypertension and is highly prevalent in older people. We recently showed differences between upper-arm cuff and invasive blood pressure (BP) become greater with increasing age, which could influence correct identification of ISH. This study sought to determine the difference between identification of ISH by cuff BP compared with invasive BP. Cuff BP and invasive aortic BP were measured in 1695 subjects (median 64 years, interquartile range [55-72], 68% male) from the INSPECT (Invasive Blood Pressure Consortium) database. Data were recorded during coronary angiography among 29 studies, using 21 different cuff BP devices. ISH was defined as ≥130/<80 mm Hg using cuff BP compared with invasive aortic BP as the reference. The prevalence of ISH was 24% (n=407) according to cuff BP but 38% (n=642) according to invasive aortic BP. There was fair agreement (Cohen κ, 0.36) and 72% concordance between cuff and invasive aortic BP for identifying ISH. Among the 28% of subjects (n=471) with misclassification of ISH status by cuff BP, 20% (n=96) of the difference was due to lower cuff systolic BP compared with invasive aortic systolic BP (mean, -16.4 mm Hg [95% CI, -18.7 to -14.1]), whereas 49% (n=231) was from higher cuff diastolic BP compared with invasive aortic diastolic BP (+14.2 mm Hg [95% CI, 11.5-16.9]). In conclusion, compared with invasive BP, cuff BP fails to identify ISH in a sizeable portion of older people and demonstrates the need to improve cuff BP measurements.

Central rather than brachial pressures are stronger predictors of cardiovascular outcomes: A longitudinal prospective study in a Chinese population

The purpose of this study was to assess the association of blood pressure (BP) measurements with the risk of cardiovascular disease (CVD) and examine whether central systolic BP (CSBP) predicts CVD better than brachial BP measurements (SBP and pulse pressure [PP]). Based on a cross-sectional study conducted in 2009-2010 with follow-up in 2016-2017 among 35- to 64-year-old subjects in China, we evaluated the performance of non-invasively predicted CSBP over brachial BP measurements on the first CVD events. Each BP measurement, individually and jointly with another BP measurement, was entered into the multivariate Cox proportional-hazards models, to examine the predictability of central and brachial BP measurements. Mean age of participants (n = 8710) was 50.1 years at baseline. After a median follow-up of 6.36 years, 187 CVD events occurred. CSBP was a stronger predictor for CVD than brachial BP measurements (CSBP, 1-standard deviation increment HR = 1.49, 95%CI: 1.31-1.70). With CSBP and SBP entering into models jointly, the HR for CSBP and SBP was 1.28 (1.04-1.58) and 1.22 (0.98-1.50), respectively. With CSBP and PP entering into models jointly, the HR for CSBP and PP was 1.51 (1.28-1.78) and 0.98 (0.83-1.15), respectively. For subgroup analysis, the association of CSBP with CVD was stronger than brachial BP measurements in women, those with hypertension and obesity. In the middle-aged Chinese population, noninvasively estimated CSBP may offer advantages over brachial BP measurements to predict CVD events, especially for participants with higher risk. These findings suggest prospective assessment of CSBP as a prevention and treatment target in further trials.

Intra-arterial analysis of the best calibration methods to estimate aortic blood pressure

OBJECTIVE

Estimation of aortic blood pressure (BP) requires peripheral BP waveform calibration. Mean arterial pressure (MAP)/DBP calibration is purported to estimate aortic BP more accurately than SBP/DBP calibration. However, this is based on inaccurate cuff calibration. Thus, direct comparisons of each calibration method using intra-arterial BP are required to confirm this, and was the aim of this study.

METHODS

Ascending aortic, brachial and radial artery intra-arterial BPs were measured among 107 patients (61.9 ± 10.0 years, 70% men) undergoing coronary angiography. Radial waveforms were calibrated with brachial SBP/DBP and brachial MAP/DBP to directly test the accuracy of estimated aortic SBP (derived using a commercial device) from each calibration compared with intra-arterial aortic SBP. Estimated aortic BP accuracy from aortic MAP/DBP, brachial and radial SBP/DBP calibrations of peripheral waveforms was also tested (six calibration methods in total; all using intra-arterial BP).

RESULTS

Estimated aortic SBP from brachial MAP/DBP calibration of radial waveforms had a significantly smaller mean difference than from brachial SBP/DBP calibration (-0.7 ± 7.5 mmHg versus -6.9 ± 7.3 mmHg, P < 0.0001 for difference). Of the other calibration methods, estimated aortic SBP was most accurate from aortic MAP/DBP calibration of radial waveforms (-1.8 ± 5.0 mmHg, P = 0.00023). However, for all calibration methods, aortic-to-brachial artery and/or brachial-to-radial artery SBP amplification had a major influence on estimated aortic SBP.

CONCLUSION

Brachial and aortic MAP/DBP were confirmed as the best calibration methods to estimate aortic SBP, but irrespective of calibration method, accuracy was significantly influenced by the level of SBP amplification. Thus, improved accuracy of estimated aortic SBP should be possible by closer consideration of SBP amplification or individual waveform characteristics that differ according to the level of SBP amplification.

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.

Current Status and Prospects of Health-Related Sensing Technology in Wearable Devices

The healthcare-related functions of wearable devices are very useful for continuous monitoring of biological information. Wearable devices equipped with communication function can be used for additional healthcare services. Among the wearable devices, the wristband type is most suitable for acquiring biological signals, and the wear preference of the user is high, so it is highly likely to be used more in the future. In this paper, the health-related functions of wristband were investigated and the technical limitations and prospects were also reviewed. Most current wristband-type devices are equipped with the combination of accelerometer, optical sensor, and electrodes for their health functions, and continuously measured data are expanding the possibility of discovering new medical meanings. The blood pressure measurement function without using cuff is the most useful and expected function among the health-related functions expected to be mounted on the wrist wearable device, in spite of its technical limits and difficulties.

Carotid pulse wave analysis: left or right, does it matter?

INTRODUCTION

Pulse wave analysis (PWA) over the carotid artery is one of the available methodological options to obtain central arterial pressures and other important hemodynamic parameters. However, limited data exist relating the PWA estimates of one carotid artery over the contralateral one as the majority of the available data rely on measures over the right carotid artery.

OBJECTIVE

To evaluate the agreement of the PWA estimates between the right carotid artery and the left carotid artery.

PATIENTS AND METHODS

A cross-sectional study of 38 patients, with a mean age of 28.85±1.70 years, was carried out. Brachial blood pressure was evaluated using a sphygmomanometer. Subsequently, PWA was obtained randomly over the left or the right carotid arteries with the Complior Analyse. All the evaluations were performed by the same experienced operator.

RESULTS

The overall mean differences observed by comparing the obtained parameters in each carotid territory were -1.50±8.06 mmHg for central systolic blood pressure (SBP), -1.63±7.98 mmHg for central pulse pressure, -3.37±27.80% for the augmentation index, and 1.50±8.06 mmHg for the SBP amplification, and were not statistically significant for all the parameters. The Bland-Altman analysis showed distinct correlations and concordance levels for different parameters: central SBP and central pulse pressure showed a very strong agreement (intraclass correlation of 0.926 and 0.886, respectively). In contrast, the concordance for the augmentation index and the SBP amplification was moderate (intraclass correlations between 0.5 and 0.8).

CONCLUSION

PWA provides similar measures of central blood pressure, whether measured over the right or the left carotid arteries, even though the morphological features of the pulse waves showed moderate agreement. The advantages of PWA over each arterial territory and the requirements that should mediate the choice of one of the both sides require further investigation.

Twenty-Four-Hour Ambulatory Pulse Wave Analysis in Hypertension Management: Current Evidence and Perspectives

The predictive value of vascular biomarkers such as pulse wave velocity (PWV), central arterial pressure (CAP), and augmentation index (AIx), obtained through pulse wave analysis (PWA) in resting conditions, has been documented in a variety of patient groups and populations. This allowed to make appropriate recommendations in clinical practice guidelines of several scientific societies. Due to advances in technologies, largely operator-independent methods are currently available for estimating vascular biomarkers also in ambulatory conditions, over the 24 h. According to the acceptable accuracy and reproducibility of 24-h ambulatory PWA, it appears to be a promising tool for evaluating vascular biomarkers in daily life conditions. This approach may provide an opportunity to further improve the early cardiovascular screening in subjects at risk. However, concerning the clinical use of PWA over the 24 h in ambulatory conditions at the moment, there is no sufficient evidence to support its routine clinical use. In particular, long-term outcome studies are needed to show the predictive value of 24-h PWV, CAP, and AIx values, provided by these devices, over and beyond peripheral blood pressure, and to answer the many technical and clinical questions still open. To this regard, the VASOTENS Registry, an international observational prospective study recently started, will help providing answers on a large sample of hypertensive patients recruited worldwide.

Effect of sodium nitrite on renal function and sodium and water excretion and brachial and central blood pressure in healthy subjects: a dose-response study

Sodium nitrite (NaNO₂) is converted to nitric oxide (NO) in vivo and has vasodilatory and natriuretic effects. Our aim was to examine the effects of NaNO₂ on hemodynamics, sodium excretion, and glomerular filtration rate (GFR). In a single-blinded, placebo-controlled, crossover study, we infused placebo (0.9% NaCl) or 0.58, 1.74, or 3.48 μmol NaNO₂·kg^-1·h^-1 for 2 h in 12 healthy subjects, after 4 days of a standard diet. Subjects were supine and water loaded. We measured brachial and central blood pressure (BP), plasma concentrations of renin, angiotensin II, aldosterone, arginine vasopressin (P-AVP), and plasma nitrite (P-[Formula: see text]), GFR by Cr-EDTA clearance, fractional excretion of sodium (FE_Na) free water clearance (C_H2O), and urinary excretion rate of guanosine 3',5'-cyclic monophosphate (U-cGMP). The highest dose reduced brachial systolic BP (5.6 mmHg, P = 0.003), central systolic BP (5.6 mmHg, P = 0.035), and C_H2O (maximum change from 3.79 to 1.27 ml/min, P = 0.031) and increased P-[Formula: see text] (from 0.065 to 0.766 μmol/l, P < 0.001), while reducing U-cGMP (from 444 to 247 pmol/min, P = 0.004). GFR, FE_Na, P-AVP, and the components in the renin-angiotensin-aldosterone system did not change significantly. In conclusion, intravenous NaNO₂ induced a dose-dependent reduction of brachial and central BP. The hemodynamic effect was not mediated by the renin-angiotensin-aldosterone system. NaNO₂ infusion resulted in a vasopressin-independent decrease in C_H2O and urine output but no change in urinary sodium excretion or GFR. The lack of increase in cGMP accompanying the increase in [Formula: see text] suggests a direct effect of nitrite or nitrate on the renal tubules and vascular bed with little or no systemic conversion to NO.

Comparison of non-invasive blood pressure monitoring using modified arterial applanation tonometry with intra-arterial measurement

Intermittent non-invasive blood pressure measurement with tourniquets is slow, can cause nerve and skin damage, and interferes with other measurements. Invasive measurement cannot be safely used in all conditions. Modified arterial tonometry may be an alternative for fast and continuous measurement. Our aim was to compare arterial tonometry sensor (BPro^®) with invasive blood pressure measurement to clarify whether it could be utilized in the postoperative setting. 28 patients who underwent elective surgery requiring arterial cannulation were analyzed. Patients were monitored post-operatively for 2 h with standard invasive monitoring and with a study device comprising an arterial tonometry sensor (BPro^®) added with a three-dimensional accelerometer to investigate the potential impact of movement. Recordings were collected electronically. The results revealed inaccurate readings in method comparison between the devices based on recommendations by Association for the Advancement of Medical Instrumentation (AAMI). On a Bland-Altman plot, the bias and precision between these two methods was 19.8 ± 16.7 (Limits of agreement - 20.1 to 59.6) mmHg, Spearman correlation coefficient r = 0.61. For diastolic pressure, the difference was 4.8 ± 7.7 (LoA - 14.1 to 23.6) mmHg (r = 0.72), and for mean arterial pressure it was 11.18 ± 11.1 (LoA - 12.1 to 34.2) mmHg (r = 0.642). Our study revealed inaccurate agreement (AAMI) between the two methods when measuring systolic and mean blood pressures during post-operative care. The readings for diastolic pressures were inside the limits recommended by AAMI. Movement increased the failure rate significantly (p < 0.001). Thus, arterial tonometry is not an appropriate replacement for invasive blood pressure measurement in these patients.

Relationship of Intraocular Pressure with Central Aortic Systolic Pressure

PURPOSE

To examine the relationship between central aortic systolic pressure (CASP) and intraocular pressure (IOP), and to compare the strength of any association with that of peripheral blood pressure and IOP.

METHODS

Adults ranging in age from 40 to 80 years were consecutively recruited from the population-based Singapore Chinese Eye Study. We measured CASP using arterial tonometry (BPro) and IOP using Goldmann applanation tonometry. All participants had a standardized examination including a complete ophthalmic and systemic examination. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured using peripheral blood pressure cuff. Univariable and multiple linear regression analyses were performed to examine the relationship between CASP and IOP. Standardized regression coefficients (sβ) were calculated to compare the associations between CASP and SBP with IOP.

RESULTS

A total of 372 consecutive Chinese participants were analyzed. After adjusting for age, gender, body mass index, total cholesterol, use of antihypertensive medication and central corneal thickness, each 10 mmHg increase in CASP was associated with 0.32 mmHg of IOP elevation [95% confidence interval (CI): 0.10-0.53, sβ = 0.160, p value = 0.004]. SBP also had a positive relationship with IOP (β = 0.279, 95% CI: 0.079-0.479, sβ = 0.152, p value = 0.006). Associations between IOP and CASP, SBP and DBP were similar in participants using antihypertensive medication to participant not using antihypertensives.

CONCLUSIONS

Increased CASP, as measured by arterial tonometry, is associated with higher IOP. Our results strengthen the relationship between systemic blood pressure and IOP.

Thresholds of Central Systolic Blood Pressure in a Normotensive Chinese Middle-Aged Population

An increasing body of evidence has emerged showing that the central systolic blood pressure (CSBP) is more relevant to the risk of cardiovascular (CV) diseases than brachial blood pressure. However, there are no agreed CSBP threshold values above which the risk of CV disease is increased. The aim of our study was to define the threshold values of the CSBP in a normotensive Chinese population; 10 012 adults 35 to 65 years of age were eligible for analysis. We excluded 3765 participants with hypertension, and the final normotensive reference sample consisted of 6247 participants. We defined abnormally high CSBP as exceeding the 90th percentile age- and sex-specific values in the normotensive population. The 90th percentile cutoff value for CSBP in the reference sample was 125 mm Hg in men and 126 mm Hg in women. The CSBP was significantly higher in participants with diabetes, history of CV disease, and hyperlipidemia (P < .001). The CSBP values increased with age (P < .001). We established that the 90th percentile of the CSBP threshold value in normotensive Chinese middle-aged population is 125 mm Hg for men and 126 mm Hg for women.

Evaluating the safety and efficacy of sodium-restricted/Dietary Approaches to Stop Hypertension diet after acute decompensated heart failure hospitalization: design and rationale for the Geriatric OUt of hospital Randomized MEal Trial in Heart Failure (GOURMET-HF)

BACKGROUND

Heart failure (HF) is a major public health problem affecting predominantly older adults. Nonadherence to diet remains a significant contributor to acute decompensated HF (ADHF). The sodium-restricted Dietary Approaches to Stop Hypertension (DASH/SRD) eating plan reduces cardiovascular dysfunction that can lead to ADHF and is consistent with current HF guidelines. We propose that an intervention that promotes adherence to the DASH/SRD by home-delivering meals will be safe and improve health-related quality of life (QOL) in older adults after hospitalization for ADHF.

METHODS/DESIGN

This is a 3-center, randomized, single-blind, controlled trial of 12-week duration designed to determine the safety and efficacy of home-delivered DASH/SRD-compliant meals in older adults after discharge from ADHF hospitalization. Sixty-six subjects will be randomized in a 1:1 stratified fashion by gender and left ventricular ejection fraction (<50% vs ≥50%). Study subjects will receive either preprepared, home-delivered DASH/SRD-compliant meals or usual dietary advice for 4weeks after hospital discharge. Investigators will be blinded to group assignment, food diaries, and urinary electrolyte measurements until study completion. The primary efficacy end point is the change in the Kansas City Cardiomyopathy Questionnaire summary scores for health-related QOL from study enrollment to 4weeks postdischarge. Safety evaluation will focus on hypotension, renal insufficiency, and hyperkalemia. Exploratory end points include echocardiography, noninvasive vascular testing, markers of oxidative stress, and salt taste sensitivity.

CONCLUSION

This randomized controlled trial will test the efficacy, feasibility, and safety of 4weeks of DASH/SRD after ADHF hospitalization. By testing a novel dietary intervention supported by multiple levels of evidence including preliminary data in outpatients with stable HF, we will address a critical evidence gap in the care of older patients with ADHF. If effective and safe, this intervention could be scaled to assess effects on readmission and healthcare costs in older adults after ADHF.

Validation of the pulse decomposition analysis algorithm using central arterial blood pressure

BACKGROUND

There is a significant need for continuous noninvasive blood pressure (cNIBP) monitoring, especially for anesthetized surgery and ICU recovery. cNIBP systems could lower costs and expand the use of continuous blood pressure monitoring, lowering risk and improving outcomes.The test system examined here is the CareTaker® and a pulse contour analysis algorithm, Pulse Decomposition Analysis (PDA). PDA's premise is that the peripheral arterial pressure pulse is a superposition of five individual component pressure pulses that are due to the left ventricular ejection and reflections and re-reflections from only two reflection sites within the central arteries.The hypothesis examined here is that the model's principal parameters P2P1 and T13 can be correlated with, respectively, systolic and pulse pressures.

METHODS

Central arterial blood pressures of patients (38 m/25 f, mean age: 62.7 y, SD: 11.5 y, mean height: 172.3 cm, SD: 9.7 cm, mean weight: 86.8 kg, SD: 20.1 kg) undergoing cardiac catheterization were monitored using central line catheters while the PDA parameters were extracted from the arterial pulse signal obtained non-invasively using CareTaker system.

RESULTS

Qualitative validation of the model was achieved with the direct observation of the five component pressure pulses in the central arteries using central line catheters. Statistically significant correlations between P2P1 and systole and T13 and pulse pressure were established (systole: R square: 0.92 (p < 0.0001), diastole: R square: 0.78 (p < 0.0001). Bland-Altman comparisons between blood pressures obtained through the conversion of PDA parameters to blood pressures of non-invasively obtained pulse signatures with catheter-obtained blood pressures fell within the trend guidelines of the Association for the Advancement of Medical Instrumentation SP-10 standard (standard deviation: 8 mmHg(systole: 5.87 mmHg, diastole: 5.69 mmHg)).

CONCLUSIONS

The results indicate that arterial blood pressure can be accurately measured and tracked noninvasively and continuously using the CareTaker system and the PDA algorithm. The results further support the physical model that all of the features of the pressure pulse envelope, whether in the central arteries or in the arterial periphery, can be explained by the interaction of the left ventricular ejection pressure pulse with two centrally located reflection sites.

Central blood pressure: current evidence and clinical importance

Pressure measured with a cuff and sphygmomanometer in the brachial artery is accepted as an important predictor of future cardiovascular risk. However, systolic pressure varies throughout the arterial tree, such that aortic (central) systolic pressure is actually lower than corresponding brachial values, although this difference is highly variable between individuals. Emerging evidence now suggests that central pressure is better related to future cardiovascular events than is brachial pressure. Moreover, anti-hypertensive drugs can exert differential effects on brachial and central pressure. Therefore, basing treatment decisions on central, rather than brachial pressure, is likely to have important implications for the future diagnosis and management of hypertension. Such a paradigm shift will, however, require further, direct evidence that selectively targeting central pressure, brings added benefit, over and above that already provided by brachial artery pressure.

Application of the N-Point Moving Average Method for Brachial Pressure Waveform–Derived Estimation of Central Aortic Systolic Pressure

The N-point moving average (NPMA) is a mathematical low-pass filter that can smooth peaked noninvasively acquired radial pressure waveforms to estimate central aortic systolic pressure using a common denominator of N/4 (where N=the acquisition sampling frequency). The present study investigated whether the NPMA method can be applied to brachial pressure waveforms. In the derivation group, simultaneously recorded invasive high-fidelity brachial and central aortic pressure waveforms from 40 subjects were analyzed to identify the best common denominator. In the validation group, the NPMA method with the obtained common denominator was applied on noninvasive brachial pressure waveforms of 100 subjects. Validity was tested by comparing the noninvasive with the simultaneously recorded invasive central aortic systolic pressure. Noninvasive brachial pressure waveforms were calibrated to the cuff systolic and diastolic blood pressures. In the derivation study, an optimal denominator of N/6 was identified for NPMA to derive central aortic systolic pressure. The mean difference between the invasively/noninvasively estimated (N/6) and invasively measured central aortic systolic pressure was 0.1±3.5 and −0.6±7.6 mm Hg in the derivation and validation study, respectively. It satisfied the Association for the Advancement of Medical Instrumentation standard of 5±8 mm Hg. In conclusion, this method for estimating central aortic systolic pressure using either invasive or noninvasive brachial pressure waves requires a common denominator of N/6. By integrating the NPMA method into the ordinary oscillometric blood pressure determining process, convenient noninvasive central aortic systolic pressure values could be obtained with acceptable accuracy.

Vascular calcification is not associated with increased ambulatory central aortic systolic pressure in prevalent dialysis patients

Introduction

Central aortic systolic pressure (CASP) strongly predicts cardiovascular outcomes. We undertook to measure ambulatory CASP in 74 prevalent dialysis patients using the BPro (HealthStats, Singapore) device. We also determined whether coronary or abdominal aortic calcification was associated with changes in CASP and whether interdialytic CASP predicted ambulatory measurement.

Methods

All patients underwent computed tomography for coronary calcium score, lateral abdominal radiography for aortic calcium score, echocardiography for left ventricular mass index and ambulatory blood pressure measurement using BPro calibrated to brachial blood pressure. HealthStats was able to convert standard BPro SOFT® data into ambulatory CASP.

Results

Ambulatory CASP was not different in those without and with coronary (137.6 vs 141.8 mmHg, respectively, p = 0.6) or aortic (136.6 vs 145.6 mmHg, respectively, p = 0.2) calcification. Furthermore, when expressed as a percentage of brachial systolic blood pressure to control for peripheral blood pressure, any difference in CASP was abolished: CASP: brachial systolic blood pressure ratio = 0.9 across all categories regardless of the presence of coronary or aortic calcification (p = 0.2 and 0.4, respectively). Supporting this finding, left ventricular mass index was also not different in those with or without vascular calcification (p = 0.7 and 0.8 for coronary and aortic calcification). Inter-dialytic office blood pressure and CASP correlated excellently with ambulatory measurements (r = 0.9 for both).

Conclusion

Vascular calcification was not associated with changes in ambulatory central aortic systolic pressure in this cohort of prevalent dialysis patients. Inter-dialytic blood pressure and CASP correlated very well with ambulatory measurement.

Low-sodium DASH diet improves diastolic function and ventricular-arterial coupling in hypertensive heart failure with preserved ejection fraction

BACKGROUND

Heart failure with preserved ejection fraction (HFPEF) involves failure of cardiovascular reserve in multiple domains. In HFPEF animal models, dietary sodium restriction improves ventricular and vascular stiffness and function. We hypothesized that the sodium-restricted dietary approaches to stop hypertension diet (DASH/SRD) would improve left ventricular diastolic function, arterial elastance, and ventricular-arterial coupling in hypertensive HFPEF.

METHODS AND RESULTS

Thirteen patients with treated hypertension and compensated HFPEF consumed the DASH/SRD (target sodium, 50 mmol/2100 kcal) for 21 days. We measured baseline and post-DASH/SRD brachial and central blood pressure (via radial arterial tonometry) and cardiovascular function with echocardiographic measures (all previously invasively validated). Diastolic function was quantified via the parametrized diastolic filling formalism that yields relaxation/viscoelastic (c) and passive/stiffness (k) constants through the analysis of Doppler mitral inflow velocity (E-wave) contours. Effective arterial elastance (Ea) end-systolic elastance (Ees) and ventricular-arterial coupling (defined as the ratio Ees:Ea) were determined using previously published techniques. Wilcoxon matched-pairs signed-rank tests were used for pre-post comparisons. The DASH/SRD reduced clinic and 24-hour brachial systolic pressure (155 ± 35 to 138 ± 30 and 130 ± 16 to 123 ± 18 mm Hg; both P=0.02), and central end-systolic pressure trended lower (116 ± 18 to 111 ± 16 mm Hg; P=0.12). In conjunction, diastolic function improved (c=24.3 ± 5.3 to 22.7 ± 8.1 g/s; P=0.03; k=252 ± 115 to 170 ± 37 g/s(2); P=0.03), Ea decreased (2.0 ± 0.4 to 1.7 ± 0.4 mm Hg/mL; P=0.007), and ventricular-arterial coupling improved (Ees:Ea=1.5 ± 0.3 to 1.7 ± 0.4; P=0.04).

CONCLUSIONS

In patients with hypertensive HFPEF, the sodium-restricted DASH diet was associated with favorable changes in ventricular diastolic function, arterial elastance, and ventricular-arterial coupling.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00939640.

24-hour central aortic systolic pressure and 24-hour central pulse pressure are related to diabetic complications in type 1 diabetes - a cross-sectional study

BACKGROUND

Non-invasive measurements of 24 hour ambulatory central aortic systolic pressure (24 h-CASP) and central pulse pressure (24 h-CPP) are now feasible. We evaluate the relationship between 24 h central blood pressure and diabetes-related complications in patients with type 1 diabetes.

METHODS

The study was cross-sectional, including 715 subjects: 86 controls (C), 69 patients with short diabetes duration (< 10 years), normoalbuminuria (< 30 mg/24 h) without receiving antihypertensive treatment (SN), 211 with longstanding diabetes (≥ 10 years) and normoalbuminuria (LN), 163 with microalbuminuria (30-299 mg/24 h) (Mi) and 186 with macroalbuminuria (> 300 mg/24 h) (Ma).24 h-CASP and 24 h-CPP was measured using a tonometric wrist-watch-like device (BPro, HealthStats, Singapore) and derived using N-point moving average.

RESULTS

In C, SN, LN, Mi and Ma mean ± SD 24 h-CASP was: 114 ± 17, 115 ± 13, 121 ± 13, 119 ± 16 and 121 ± 13 mmHg (p < 0.001); and 24 h-CPP: 38 ± 8, 38 ± 7, 44 ± 10, 46 ± 11 and 46 ± 11 mmHg, (p < 0.001).Following rigorous adjustment (24 h mean arterial pressure and conventional risk factors), 24 h-CASP and 24 h-CPP increased with diabetes, albuminuria degree, previous cardiovascular disease (CVD), retinopathy and autonomic dysfunction (p ≤ 0.031).Odds ratios per 1 standard deviation increase in 24 h-CASP, 24 h-CPP and 24 h systolic blood pressure (24 h-SBP) were for CVD: 3.19 (1.68-6.05), 1.43 (1.01-2.02) and 2.39 (1.32-4.33), retinopathy: 4.41 (2.03-9.57), 1.77 (1.17-2.68) and 3.72 (1.85-7.47) and autonomic dysfunction: 3.25 (1.65-6.41), 1.64 (1.12-2.39) and 2.89 (1.54-5.42).

CONCLUSIONS

24 h-CASP and 24 h-CPP was higher in patients vs. controls and increased with diabetic complications independently of covariates. Furthermore, 24 h-CASP was stronger associated to complications than 24 h-SBP.The prognostic significance of 24 h-CASP and 24 h-CPP needs to be determined in follow-up studies.

TRIAL REGISTRATION

ClinicalTrials.gov ID NCT01171248.

Novel description of the 24-hour circadian rhythms of brachial versus central aortic blood pressure and the impact of blood pressure treatment in a randomized controlled clinical trial: The Ambulatory Central Aortic Pressure (AmCAP) Study

Elevated brachial blood pressure (BP) is associated with increased cardiovascular risk and predicts morbidity and mortality in humans. Recently, 24-hour ambulatory BP monitoring and assessment of central aortic BP have been introduced to improve BP phenotyping. The Ambulatory Central Aortic Pressure (AmCAP) study combines these approaches and describes, for the first time, the diurnal patterns of simultaneously measured 24-hour ambulatory brachial and central pressures in a prespecified substudy embedded within a clinical trial of BP lowering in patients with hypertension. Twenty-four-hour ambulatory brachial and central pressure measurements were acquired using a tonometer mounted into the articulating strap of a wristwatch-like device (BPro) in 171 participants with hypertension recruited into the ASSERTIVE (AliSkiren Study of profound antihypERtensive efficacy in hyperTensIVE patients) trial. Participants were randomly assigned to BP lowering with either aliskiren 300 mg QD or telmisartan 80 mg QD for 12 weeks. Ambulatory brachial and central BP was measured in all participants both at baseline and at study end. Brachial and central BP both demonstrated typical diurnal patterns with lower pressures at night. However, night time was associated with smaller reductions in central relative to brachial pressure and decreased pulse pressure amplification (P<0.0001 for both). These effects were not modulated after BP lowering and were maintained after adjustment for day and night-time BP and heart rate (P=0.02). This study demonstrates that brachial and central pressure show different diurnal patterns, which are not modulated by BP-lowering therapy, with relatively higher night-time central pressures. These novel data indicate that night-time central BP may provide prognostic importance and warrants further investigation. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00865020.

Vascular and renal hemodynamic changes after renal denervation

BACKGROUND AND OBJECTIVES

Renal denervation (RDN) has been shown to be effective in reducing BP in treatment-resistant hypertension. Measurement of the renal and sympathetic activity revealed a decrease in sympathetic drive to the kidney and small resistance vessels after RDN. However, the consequences on renal perfusion and renal vascular resistance (RVR), as well as central hemodynamics, are unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Nineteen patients with treatment-resistant hypertension (office BP≥140/90 mmHg, despite at least three antihypertensive drugs [including a diuretic], and diagnosis confirmed by 24-hour ambulatory BP monitoring) underwent RDN between January and October 2011. Renal perfusion and RVR were noninvasively assessed by magnetic resonance imaging with arterial spin labeling, and renal function was assessed by estimating GFR before (day -1), after (day +1), and again after 3 months of RDN. Central hemodynamics was assessed using pulse wave analysis at day -1 and after 6 months of RDN.

RESULTS

Peripheral office BP (systolic, 158±26 versus 142±23 mmHg, P=0.002; diastolic, 83±13 versus 76±9 mmHg, P=0.02) and mean systolic 24-hour ambulatory BP (159±17 versus 152±17 mmHg, P=0.02) were significantly reduced 6 months after RDN. Renal perfusion was not statistically different between day -1 and day +1 (256.8 [interquartile range (IQR), 241-278] versus 263.4 [IQR, 252-277] ml/min per 100 g; P=0.17) as well as after 3 months (256.8 [IQR, 241-278] versus 261.2 [IQR, 240-285] ml/min per 100 g; P=0.27) after RDN. RVR dropped (432.1 [IQR, 359-525] versus 390.6 [IQR, 338-461] AU; P=0.02), whereas renal function was not statistically different at any time point. Central systolic BP (145±31 versus 131±28 mmHg; P=0.009), diastolic BP (85±18 versus 80±14 mmHg; P=0.03), and central pulse pressure (61±18 versus 52±18 mmHg; P=0.02) were significantly reduced 6 months after RDN. Central augmentation index (24±8 versus 20±8%; P=0.02) was decreased 6 months after RDN.

CONCLUSION

The data indicate that RDN significantly reduced peripheral and central BP. Despite reduced systemic BP, renal perfusion and function did not change after RDN.