Association of Central and Peripheral Blood Pressures With Intermediate Cardiovascular Phenotypes

Aortic Stiffness Is Associated With Higher Nighttime Ambulatory Blood Pressure in Middle-Aged and Older Adults

PURPOSE

The objective of this study was to determine the relationship between aortic stiffening and brachial and central ambulatory blood pressure (AMBP) in a nonclinical sample of middle-aged and older adults (MA/O). We hypothesized aortic stiffness would be positively associated with 24-hr, daytime, and nighttime brachial and central AMBP.

METHODS

Fifty-one participants aged ≥50 yr (21 males and 30 females, mean age 63.4 ± 9.0 yr) with a body mass index <35 kg/m 2 who also had a resting brachial blood pressure (BP) <160/100 mmHg with or without BP medications were recruited for this cross-sectional analysis. All participants underwent measures of aortic stiffness (carotid-femoral pulse wave velocity [cfPWV]) and 24-hr AMBP monitoring. Bivariate correlations assessed the relationship between cfPWV, brachial, and central AMBP. Partial correlations were used to independently adjust for traditional cardiovascular disease (CVD) risk factors including age, sex, waist circumference, glucose, and augmentation index normalized to heart rate 75 bpm, a surrogate measure of arterial stiffness, and in a multivariable combined model.

RESULTS

Nighttime brachial systolic BP ( r = 0.31) and central systolic BP ( r = 0.30) were correlated with cfPWV in the multivariable combined model ( P ≤ .05). Nighttime brachial pulse pressure and central pulse pressure were correlated with cfPWV after independently adjusting for all CVD risk factors ( P ≤ .05, all) but not when combined in the multivariable model ( P > .05).

CONCLUSIONS

Higher nighttime brachial and central AMBP with older age are related, in part, to greater aortic stiffening. Therefore, interventions to lower or prevent aortic stiffening may also lower nighttime BP in MA/O adults to lower CVD risk.

A generalized canine transfer function accurately reconstructs central aortic pressure waveforms to enable enhanced pulse wave analysis

Routine preclinical blood pressure evaluation is an important risk assessment tool. Although proximal aortic pressure is most relevant for key target organs, abdominal aortic pressures are more commonly recorded. Pulse pressure amplification and waveform distortion in abdominal waveforms make it inappropriate for central hemodynamic analytical methods without the use of a mathematical transfer function. Clinical transfer functions have been developed to estimate ascending aortic waveforms from brachial or radial artery waveforms in humans, but no preclinical analogues exist. The aim of this study was to develop a canine-specific transfer function to reconstruct thoracic aortic pressure waveforms from abdominal aortic data to enable the application of central hemodynamic analytical methods. Simultaneous abdominal and thoracic blood pressures were recorded from seven conscious, male beagle dogs administered 3 well-characterized pharmacologic standards and animals were appointed to a training (n = 3) or validation (n = 4) group at baseline and during dosing. A generalized transfer function was developed from the training group data and evaluated for its ability to synthesize thoracic pressure waves in the training and validation groups. Select hemodynamic parameters were evaluated in measured and synthesized thoracic data. There was a high degree of correlation between measured and synthesized thoracic parameters (r2 = 0.74-0.99). There was no difference between indices computed from synthesized or actual thoracic waveforms at baseline or after administration of pharmacologic standards. This work demonstrates that a generalized preclinical transfer function can reproduce thoracic pressure waves across a range of hemodynamic responses thus enabling the application of central hemodynamic analytical methods.

Relation of forward and backward traveling pressure waves with subclinical carotid artery wall remodeling and central pulse pressure

Central pulse pressure (PP) is the sum of forward and backward traveling pressure waves that have been associated with cardiovascular disease (CVD) risk. However, previous studies have reported differential findings regarding the importance of the forward versus the backward wave for CVD risk. Therefore, we sought to determine the degree to which the forward and backward pressure waves are associated with subclinical carotid artery wall remodeling and central PP in healthy adults. Using applanation tonometry, carotid pressure waveforms were acquired in 308 healthy individuals (aged 45 ± 17 years, range 19-80 years, 61% women), from which the time integral of the forward (PfTI) and backward (PbTI) pressure waves were derived via pressure-only wave separation analysis. Common carotid artery intima-media thickness (cIMT), a biomarker of subclinical CVD risk, was derived via B-mode ultrasonography measured ∼2 cm from the carotid bulb. Both PfTI (r = 0.31, P < 0.001) and PbTI (r = 0.40, P < 0.001) were correlated with cIMT. However, further analysis revealed that PbTI mediated the relation between PfTI and cIMT (proportion mediated = 156%, P < 0.001). The association between PbTI and cIMT remained after adjusting for age, sex, body mass index, blood glucose, low-density lipoprotein cholesterol, heart rate, brachial systolic pressure, and aortic stiffness (B = 0.02, 95% confidence interval = 0.01, 2.77, P < 0.001). Both PfTI (r = -0.58, P < 0.001) and PbTI (r = -0.50, P < 0.001) were correlated with central PP, however, PfTI fully mediated the association between PbTI and central PP (proportion mediated = 124%, P < 0.001). Although PfTI is correlated with higher central PP, it is PbTI that is directly associated with carotid artery wall remodeling.NEW & NOTEWORTHY The present study contributes to the growing body of evidence highlighting the physiological and clinical insight provided by the pulsatile hemodynamic components of central artery pulse pressure. The notable findings of this study are: 1) The reflected (backward) pressure wave is associated with carotid intima-media thickness independent of traditional cardiovascular risk factors, including systolic blood pressure and aortic stiffness. 2) The incident (forward) pressure wave, and not the reflected pressure wave, is associated with greater central pulse pressure.

Development of a Machine Learning Model of Postoperative Acute Kidney Injury Using Non-Invasive Time-Sensitive Intraoperative Predictors

Acute kidney injury (AKI) is a major postoperative complication that lacks established intraoperative predictors. Our objective was to develop a prediction model using preoperative and high-frequency intraoperative data for postoperative AKI. In this retrospective cohort study, we evaluated 77,428 operative cases at a single academic center between 2016 and 2022. A total of 11,212 cases with serum creatinine (sCr) data were included in the analysis. Then, 8519 cases were randomly assigned to the training set and the remainder to the validation set. Fourteen preoperative and twenty intraoperative variables were evaluated using elastic net followed by hierarchical group least absolute shrinkage and selection operator (LASSO) regression. The training set was 56% male and had a median [IQR] age of 62 (51-72) and a 6% AKI rate. Retained model variables were preoperative sCr values, the number of minutes meeting cutoffs for urine output, heart rate, perfusion index intraoperatively, and the total estimated blood loss. The area under the receiver operator characteristic curve was 0.81 (95% CI, 0.77-0.85). At a score threshold of 0.767, specificity was 77% and sensitivity was 74%. A web application that calculates the model score is available online. Our findings demonstrate the utility of intraoperative time series data for prediction problems, including a new potential use of the perfusion index. Further research is needed to evaluate the model in clinical settings.

The significance of central blood pressure for cardiovascular target organ damage in children and adolescents after kidney transplantation

BACKGROUND

Cardiovascular (CV) complications are important causes of morbidity and mortality in children after kidney transplantation (KTx). In adults, central blood pressure (cBP) is an accepted predictor of CV sequelae. We aimed to assess the prognostic value of cBP over peripheral blood pressure (pBP) for existing CV damage.

METHODS

We measured cBP and pBP in 48 pediatric KTx recipients (mean age: 13.5 ± 4.2 years). Assessment of left ventricular mass index (LVMI) and aortic pulse wave velocity (PWV) allowed detection of CV target organ damage. LVMI and PWV were used as endpoints in multivariable linear regression models, in which cBP and pBP were compared for their predictive value.

RESULTS

Using cBP z-scores, we identified a larger number of patients with uncontrolled or untreated hypertension compared to pBP (36% vs. 7%). Central systolic blood pressure (cSBP) was a significant independent predictor of LVMI, while peripheral systolic blood pressure (pSBP) was not. Comparing central (cDBP) and peripheral (pDBP) diastolic blood pressure for their predictive value on PWV revealed a greater estimate for cDBP (0.035 vs. 0.026 for pDBP) along with a slightly better model fit for cDBP.

CONCLUSIONS

Our data in a small group of patients provide first evidence that cBP measurements in pediatric KTx recipients might be helpful in identifying patients at risk for the development of CV sequelae. Investigating a larger patient number, ideally repeatedly, is needed to create further evidence supporting our findings. In light of available devices measuring cBP noninvasively, the implementation of such clinical studies post-KTx care should be feasible. A higher resolution version of the Graphical abstract is available as Supplementary information.

Low length-for-age Z-score within 1 month after birth predicts hyperdynamic circulation at the age of 21 years in rural Malawi

Low birth weight predisposes to the development of hypertension in middle- and high-income countries. We examined the relation of early life length-for-age score (Z-score) on cardiovascular function in young adults in Malawi, a low-income country. Capture of supine, seated, and standing brachial pulse waveforms (Mobil-O-Graph) were performed in 223 females and 152 males (mean age 21 years), and analyzed according to the length-for-age Z-score tertiles during the first month of life. Plasma LDL cholesterol in young adulthood was slightly lower in the lowest versus highest tertile. Otherwise, blood hemoglobin and plasma chemistry were similar in all tertiles. Irrespective of posture, blood pressure, forward and backward wave amplitudes, and pulse wave velocity were corresponding in all tertiles. In the three postures, the lowest tertile presented with 4.5% lower systemic vascular resistance than the highest tertile (p = 0.005), and 4.4% and 5.5% higher cardiac output than the middle and highest tertiles, respectively (p < 0.01). Left cardiac work was 6.8% and 6.9% higher in the lowest tertile than in the middle and highest tertiles, respectively (p < 0.01). To conclude, in a low-income environment, low length-for-age Z-score after birth predicted hyperdynamic circulation at 21 years of age without changes in blood pressure and metabolic variables.

Controls of Central and Peripheral Blood Pressure and Hemorrhagic/Hypovolemic Shock

The pressure exerted on the heart and blood vessels because of blood flow is considered an essential parameter for cardiovascular function. It determines sufficient blood perfusion, and transportation of nutrition, oxygen, and other essential factors to every organ. Pressure in the primary arteries near the heart and the brain is known as central blood pressure (CBP), while that in the peripheral arteries is known as peripheral blood pressure (PBP). Usually, CBP and PBP are correlated; however, various types of shocks and cardiovascular disorders interfere with their regulation and differently affect the blood flow in vital and accessory organs. Therefore, understanding blood pressure in normal and disease conditions is essential for managing shock-related cardiovascular implications and improving treatment outcomes. In this review, we have described the control systems (neural, hormonal, osmotic, and cellular) of blood pressure and their regulation in hemorrhagic/hypovolemic shock using centhaquine (Lyfaquin^®) as a resuscitative agent.

Distinct components of cardiovascular health are linked with age-related differences in cognitive abilities

Cardiovascular ageing contributes to cognitive impairment. However, the unique and synergistic contributions of multiple cardiovascular factors to cognitive function remain unclear because they are often condensed into a single composite score or examined in isolation. We hypothesized that vascular risk factors, electrocardiographic features and blood pressure indices reveal multiple latent vascular factors, with independent contributions to cognition. In a population-based deep-phenotyping study (n = 708, age 18-88), path analysis revealed three latent vascular factors dissociating the autonomic nervous system response from two components of blood pressure. These three factors made unique and additive contributions to the variability in crystallized and fluid intelligence. The discrepancy in fluid relative to crystallized intelligence, indicative of cognitive decline, was associated with a latent vascular factor predominantly expressing pulse pressure. This suggests that higher pulse pressure is associated with cognitive decline from expected performance. The effect was stronger in older adults. Controlling pulse pressure may help to preserve cognition, particularly in older adults. Our findings highlight the need to better understand the multifactorial nature of vascular aging.

Posture-Related Differences in Cardiovascular Function Between Young Men and Women: Study of Noninvasive Hemodynamics in Rural Malawi

Background

Cardiovascular risk is higher in men than in women, but little information exists about sex‐related differences in cardiovascular function from low‐income countries. We compared hemodynamics between sexes in rural Malawi in a cohort followed up since their birth.

Methods and Results

Supine, seated, and standing hemodynamics were recorded from 251 women and 168 men (mean age, 21 years; body mass index, 21 kg/m²) using oscillometric brachial waveform analyses (Mobil‐O‐Graph). The results were adjusted for estimated glomerular filtration rate, and plasma potassium, lipids, and glucose. Men had higher brachial and aortic systolic blood pressure and stroke index regardless of posture (P<0.001), and higher upright but similar supine diastolic blood pressure than women. Regardless of posture, heart rate was lower in men (P<0.001), whereas cardiac index did not differ between sexes. Women presented with lower supine and standing systemic vascular resistance index (P<0.001), whereas supine‐to‐standing increase in vascular resistance (P=0.012) and decrease in cardiac index (P=0.010) were higher in women. Supine left cardiac work index was similar in both sexes, whereas standing and seated left cardiac work index was higher in men than in women (P<0.001).

Conclusions

In young Malawian adults, men had higher systolic blood pressure, systemic vascular resistance, and upright cardiac workload, whereas women presented with higher posture‐related changes in systemic vascular resistance and cardiac output. These findings show systematic sex‐related differences in cardiovascular function in a cohort from a low‐income country with high exposure to prenatal and postnatal malnutrition and infectious diseases.

Microcirculation and Macrocirculation in Hypertension: A Dangerous Cross-Link?

Microcirculation and macrocirculation are tightly interconnected into a dangerous cross-link in hypertension. Small artery damage includes functional (vasoconstriction, impaired vasodilatation) and structural abnormalities (mostly inward eutrophic remodeling). These abnormalities are major determinants of the increase in total peripheral resistance and mean blood pressure (BP) in primary hypertension, which in the long term induces large artery stiffening. In turn, large artery stiffening increases central systolic and pulse pressures, which are further augmented by wave reflection in response to the structural alterations in small resistance arteries. Finally, transmission of high BP and flow pulsatility to small resistance arteries further induces functional and structural abnormalities, thus leading to increased total peripheral resistance and mean BP, thus perpetuating the vicious circle. Hyperpulsatility, in addition to higher mean BP, exaggerates cardiac, brain, and kidney damages and leads to cardiovascular, cerebral, and renal complications. The dangerous cross-link between micro and macrocirculation can be reversed into a virtuous one by ACE (angiotensin-converting enzyme) inhibitors, sartans, and calcium channel blockers. These three pharmacological classes are more potent than β-blockers and diuretics for reducing arterial stiffness and small artery remodeling. The same ranking was observed for their effectiveness at reducing left ventricular hypertrophy, preserving glomerular filtration rate, and preventing dementia, suggesting that they can act beyond brachial BP reduction, by breaking the micro/macrocirculation vicious circle.

Central Over Peripheral Blood Pressure: An Emerging Issue in Hypertension Research

Measurement of blood pressure is one of the most important and powerful clinical tools in clinical practice. Physicians use the classical method that was introduced more than 100 years ago with the emergence of the brachial cuff sphygmomanometer. The use of this method, despite its initial setbacks, spread like fire throughout the medical community with the boost by the early adoption by insurance companies to assess risk as well as the ease of use, the availability with the wide variety of devices, the good reproducibility and its predictive role. However, a long-forgotten dispute between measurements of peripheral (brachial) and central (aortic, carotid) blood pressure has resurfaced after the introduction of techniques and devices that can easily and accurately estimate non-invasively the central pressure waveform. Clinicians, until recently, focussed only on the pressure waveform trough (diastole) and peak (systole), ignoring the possible information provided by the rest of the arterial pressure waveform. Several restrictions exist with peripheral blood pressures measured with either an oscillometric or a sphygmomanometer device that blur the existing image of the ideal biomarker to describe the haemodynamic characteristics of the cardiovascular system. On the other hand, central pressures seem to be more pathophysiologically relevant to end-organ damage of the brain, heart and kidneys and on future events. Furthermore, measurement of the central waveform can provide clinically useful information, like the quantification of wave reflections with augmentation index, beyond blood pressure measured in the brachial artery. This article will explain the pathophysiological mechanisms linking central pressures to cardiovascular outcomes, review the evidence for the use of central blood pressure over peripheral pressures, elaborate on the prognostic role of central blood pressures and finally review the latest developments on the pharmacological modulation of central blood pressures.

Reservoir-Excess Pressure Parameters Independently Predict Cardiovascular Events in Individuals With Type 2 Diabetes

[Figure: see text].

Arterial Stiffness and Hypertension in the Elderly

Hypertension prevalence increases with age. Age and high blood pressure are the two main determinants of arterial stiffness. In elderly hypertensives, large arteries stiffen and systolic and pulse pressures increase, due to wave reflections. A major reason for measuring arterial stiffness in clinical practice in elderly hypertensive patients comes from the repeated demonstration that arterial stiffness and wave reflections have a predictive value for CV events. A large body of evidence has been published during the last two decades, concerning the epidemiology, pathophysiology, and pharmacology of large arteries in hypertension in various settings of age. Particularly, two expert consensus documents have reviewed the methodological agreements for measuring arterial stiffness. The concepts of Early Vascular Aging (EVA) and Supernormal Vascular Aging (SUPERNOVA) help to better understand on which determinants of arterial stiffness it is possible to act, in order to limit target organ damage and cardiovascular complications. This review will address the issues of the cellular and molecular mechanisms of arterial stiffening in elderly hypertensives, the consequences of arterial stiffening on central systolic and pulse (systolic minus diastolic, PP) pressures and target organs, the methodology for measuring arterial stiffness, central pulse pressure and wave reflection, the epidemiological determinants of arterial stiffening in elderly hypertensives, the pharmacology of arterial destiffening, and how the concepts of EVA and SUPERNOVA apply to the detection of organ damage and prevention of CV complications.

Haemodynamics of Hypertension in Children

PURPOSE OF REVIEW

To review the haemodynamic characteristics of paediatric hypertension.

RECENT FINDINGS

Pulsatile components of blood pressure are determined by left ventricular dynamics, aortic stiffness, systemic vascular resistance and wave propagation phenomena. Recent studies delineating these factors have identified haemodynamic mechanisms contributing to primary hypertension in children. Studies to date suggest a role of cardiac over activity, characterized by increased heart rate and left ventricular ejection, and increased aortic stiffness as the main haemodynamic determinants of primary hypertension in children.

Ballistocardiography and seismocardiography detection of hemodynamic changes during simulated obstructive apnea

OBJECTIVE

To investigate if modern seismocardiography (SCG) and ballistocardiography (BCG) are useful in the detection of hemodynamic changes occurring during simulated obstructive apneic events.

METHODS

Forty-seven healthy volunteers performed a voluntary maximum Mueller maneuver (MM) for 10 s, and SCG and BCG signals were simultaneously taken. The kinetic energy of a set of cardiac cycles before and during the apneic episode was automatically computed from the rotational and linear channels of the SCG and BCG waveforms and its temporal integral (i K) was derived (unit of measure: microjoules per second (µJ·s)). The estimated transmural pressure (eP _TM ) was assessed as the difference between systemic blood pressure and maximal inspiratory pressure (MIP). The Wilcoxon sign-rank test was used to evaluate differences in energy measurements between normal respiration and the loaded inspiration maneuver. Cardiac kinetic energies and the MIP produced during the MM were compared by linear regression analysis following log transformation in order to assess the correlation between variables.

MAIN RESULTS

The [Formula: see text] during normal breathing increased from 1.1(0.8; 1.4) to 1.9(1.4; 4.3) µJ·s during MM (p < 0.001). Meanwhile, [Formula: see text] increased from 54 (31; 92) to 84 (44; 153) µJ·s, (p < 0.001). The [Formula: see text] and [Formula: see text] of a set of cardiac cycles during the MM were negatively associated with the MIP (r: -0.59, p < 0.001 and r: -0.53, p = 0.001 for [Formula: see text] and [Formula: see text], respectively). When eP _TM was considered, this association became positive (r: +0.58, p < 0.001 and r:+0.60, p < 0.001, for [Formula: see text] and [Formula: see text], respectively). When the i K _LIN was considered as the comparative factor, correlations with the MIP and eP _TM were weak and insignificant. Men had higher values of i K than women.

SIGNIFICANCE

Simulated obstructive apnea elicits large rotational i K swings, which are related to the intensity of the inspiratory effort and, as such, to the intensity of the left ventricular afterload. Computation of cardiac kinetic energy through BCG and SCG may shed further light on the impact of obstructive respiratory events on the cardiovascular system.

Arterial Stiffness and Central Hemodynamics are Associated with Low Diurnal Urinary Sodium Excretion

BACKGROUND

Excessive salt intake is an important determinant of cardiovascular (CV) health, impacting arterial stiffness and central blood pressure. However, sodium exhibits several patterns of excretion in urine during day- and night-time, which could differently affect CV risk. Here, we sought to explore the relationship between the day:night urinary sodium excretion ratio and arterial stiffness and central hemodynamics in the general population.

METHODS

Cross-sectional analysis in 1062 subjects. Arterial stiffness (pulse-wave velocity, PWV), central blood pressure (central systolic blood pressure, cSBP; central diastolic blood pressure, cDBP), and other hemodynamic parameters were noninvasively assessed. Day- and night-time urinary sodium were separately detected. Analyses were performed according to the day:night urinary sodium excretion ratio tertiles (T1-T3).

RESULTS

Low day-time excretors (T1) showed significantly higher values of arterial stiffness when compared with high day-time excretors (T3) (cf-PWV 7.6 ± 1.9 vs 6.9 ± 1.5 m/sec; p ≤ 0.001), and higher central BP parameters (cSBP: 111.6 ± 12.1 vs 109.0 ± 11.1 mmHg, p ≤ 0.001; cDBP, 76.9 ± 9.2 vs 75.1 ± 9.3 mmHg, p ≤ 0.001). In multivariate linear-regression models (β, CI), the day:night ratio of sodium excretion was significantly associated with arterial stiffness (cf-PWV -0.386, -0.559, -0.213, p ≤ 0.001) and with central hemodynamic parameters (cSBP -1.655, -2.800, -0.510; p ≤ 0.001; cDBP -1.319, -2.218, -0.420, p ≤ 0.001). Associations persisted after controlling for multiple confounding factors. In logistic-regression models, the risk of increased arterial stiffness was significantly reduced as the day:night ratio of urinary sodium excretion increased (OR 0.40, 95% CI 0.25-0.65, p ≤ 0.001).

CONCLUSION

The individual, intra-daily pattern of urinary sodium excretion, characterised by low daytime excretion, is associated with increased arterial stiffness and central blood pressure. Further studies are advocated to clarify the clinical utility of assessing the daily pattern of sodium excretion.

The association of smoothness index of central blood pressure with ambulatory carotid femoral pulse wave velocity after 20-week treatment with losartan in combination with amlodipine versus hydrochlorothiazide

Supplemental Digital Content is available in the text

The aim of this study was to identify associations between the smoothness index of central SBP (CSBP) and changes of ambulatory carotid femoral pulse wave velocity in response to 20-week treatments with losartan and amlodipine vs. losartan and hydrochlorthiazide combinations.

Comparison of central SBP in children estimated from a brachial cuff alone, brachial cuff-calibrated applanation radial tonometry and brachial cuff-calibrated carotid wall-tracking

OBJECTIVES

We compared the agreement between different techniques to estimate central SBP (cSBP) in children and the relative impact of different methods of measuring peripheral blood pressure (BP).

METHODS

A total of 135 children, aged 12.9 ± 3.0 years including 67 boys, 85 with chronic kidney disease were studied. We measured cSBP using radiofrequency ultrasound carotid wall-tracking (Esaote ART.LAB system, a previously validated reference method), transformation of the radial artery pressure waveform obtained by tonometry (SphygmoCor) and a cuff-based system (cBP301; Centron Diagnostics) during a single visit. Carotid and radial tonometric-derived values were calibrated from mean and diastolic values of brachial BP obtained by aneroid sphygmomanometer. Brachial cuff only values were calibrated from the same aneroid sphygmomanometer values and from oscillometric values obtained from the brachial cuff.

RESULTS

cSBP values estimated from radial tonometry were closely correlated with those obtained from the carotid (r = 0.959, mean difference -0.61 ± 3.5 mmHg). cSBP values estimated by the brachial cuff only method agreed reasonably well with those obtained from the carotid (r = 0.847, mean difference 5 ± 7.4 mmHg) when calibrated by the same method but when calibrated by oscillometric values from the brachial cuff, agreement was less good (r = 0.659, mean difference 8.7 ± 11.4 mmHg).

CONCLUSION

Radial tonometry with a radial-to-central transfer function can be used to estimate cSBP in children with acceptable accuracy when compared with the invasively validated carotid reference method. All methods are subject to errors introduced by calibration from peripheral BP.

Comparing Office, Central, Home and Ambulatory Blood Pressure in Predicting Left Ventricular Mass

The blood pressure measurement method that more accurately predicts a left ventricular mass is controversial, and the evidence suggesting superiority of central over brachial measurements is contradictory. The aim of this study was to compare the relationship between the different clinic and out-of-clinic blood pressure measurements methods with left ventricular mass in patients who attended a specialised hypertension centre for a central blood pressure measurement. An analysis was performed on the correlations between left ventricular mass and central and brachial blood pressure measurements made in the clinic, and home, as well as 24-h systolic blood pressure measurements. A linear regression analysis was then performed to assess the independent relationship of each blood pressure measurement with left ventricular mass. The results on 824 treated and 123 untreated patients showed no significant differences between correlations, although home readings tended to have the best correlations. In regression adjusted models, for each 10 mmHg increase in systolic home blood pressure the left ventricular mass increased 10 g/m² (95% CI; 3.7-27, p=.01, _adjR² 0.38), and for 24-h ambulatory systolic blood pressure it increased 2.3 g/m² (95% CI 0.76-3.9, p<.01, _adjR² 0.15) in treated and untreated patients, respectively. The association of systolic blood pressure with left ventricular mass was better explained by home and 24-h ambulatory monitoring than to clinic-based measurements in treated and untreated patients, respectively. In the clinic, however, the central measurement was not superior to brachial blood pressure.

Prevalence of Hypertension Defined by Central Blood Pressure Measured Using a Type II Device in a Nationally Representative Cohort

OBJECTIVES

Central blood pressure (BP) can be used to define hypertension. A central BP approach may be more sensitive than a conventional brachial BP approach in detecting hypertension. We aimed to compare the 2 approaches in estimating the prevalence hypertension in a nationally representative population.

METHODS

A total of 2,742 adults older than 19 years participated in the 2013-2016 National Nutrition and Health Survey in Taiwan. Central and brachial BP were simultaneously measured using a cuff-based stand-alone central BP monitor purporting to measure invasive central BP (type II device). Central hypertension was defined by central systolic (SBP)/diastolic BP (DBP) ≥130 or 90 mm Hg or using antihypertensive medications, and brachial hypertension was defined by brachial SBP/DBP ≥140 or 90 mm Hg or using antihypertensive medications.

RESULTS

The World Health Organization-standardized and national weighted prevalence rates of central hypertension were 27.95% and 32.48%, respectively, and both were significantly higher than those of brachial hypertension (20.80% and 25.43%, both P < 0.001). The national weighted prevalence rates of concordant central and brachial hypertension, concordant central and brachial nonhypertension, isolated central hypertension, and isolated brachial hypertension were 25.13%, 67.22%, 7.35%, and 0.30%, respectively. Most subjects with the isolated central hypertension (97%) were within the range of brachial prehypertension, but only 38.0% of subject with brachial prehypertension had central hypertension.

CONCLUSION

Almost one-third of a nationally representative population had hypertension detected by a central BP approach. Hypertension detection using a conventional brachial BP approach may underestimate the prevalence of hypertension and result in a less effective hypertension control.

Steady State vs. Pulsatile Blood Pressure Component and Regional Cerebral Perfusion

BACKGROUND

Arterial blood pressure (BP) can be divided into steady state component that is determined by mean arterial pressure and pulsatile component that is explored by pulse pressure (PP). We determined relationships between BP components and regional cerebral perfusion.

METHODS

A total of 52 apparently healthy and cognitively normal adults aged 40-60 years were studied. Regional cerebral perfusion was measured using functional magnetic resonance imaging (MRI) arterial spin labeling technique in 10 a priori regions of interest.

RESULTS

There were 5 regions with cerebral perfusion values significantly associated with either pulsatile BP component (i.e., hippocampus, posterior insula, and central white matter) or both steady and pulsatile components (i.e., anterior white matter, and occipitoparietal area). After controlling for body mass index, education, age, and sex, associations between pulsatile BP components and regional cerebral perfusion remained significant in 2 regions (i.e., hippocampus and anterior white matter). Multiple linear regression analyses revealed that brachial systolic pressure (β = -0.35, P = 0.03) and PP (β = -0.36, P = 0.02) explained 11 and 12% of the variability in hippocampus perfusion, independent of the entered covariates.

CONCLUSIONS

The present preliminary study indicated that pulsatile component of BP was more strongly related to regional cerebral perfusion in areas susceptible to cerebrovascular diseases than steady state component.

Relationship Between 24-Hour Ambulatory Central Systolic Blood Pressure and Left Ventricular Mass: A Prospective Multicenter Study

We investigated the relationship between left ventricular mass and brachial office as well as brachial and central ambulatory systolic blood pressure in 7 European centers. Central systolic pressure was measured with a validated oscillometric device, using a transfer function, and mean/diastolic pressure calibration. M-mode images were obtained by echocardiography, and left ventricular mass was determined by one single reader blinded to blood pressure. We studied 289 participants (137 women) free from antihypertensive drugs (mean age: 50.8 years). Mean office blood pressure was 145/88 mm Hg and mean brachial and central ambulatory systolic pressures were 127 and 128 mm Hg, respectively. Mean left ventricular mass was 93.3 kg/m², and 25.6% had left ventricular hypertrophy. The correlation coefficient between left ventricular mass and brachial office, brachial ambulatory, and central ambulatory systolic pressure was 0.29, 0.41, and 0.47, respectively (P=0.003 for comparison between brachial office and central ambulatory systolic pressure and 0.32 for comparison between brachial and central ambulatory systolic pressure). The results were consistent for men and women, and young and old participants. The areas under the curve for prediction of left ventricular hypertrophy were 0.618, 0.635, and 0.666 for brachial office, brachial, and central ambulatory systolic pressure, respectively (P=0.03 for comparison between brachial and central ambulatory systolic pressure). In younger participants, central ambulatory systolic pressure was superior to both other measurements. Central ambulatory systolic pressure, measured with an oscillometric cuff, shows a strong trend toward a closer association with left ventricular mass and hypertrophy than brachial office/ambulatory systolic pressure.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01278732.

Aldosterone breakthrough does not alter central hemodynamics

Introduction:

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are widely used in congestive heart failure and chronic kidney disease, but up to 40% of patients will experience aldosterone breakthrough, with aldosterone levels rising above pre-treatment levels after 6–12 months of renin-angiotensin-aldosterone system blockade. Aldosterone breakthrough has been associated with worsening congestive heart failure and chronic kidney disease, yet the pathophysiology remains unclear. Breakthrough has not been associated with elevated peripheral blood pressure, but no studies have assessed its effect on central blood pressure.

Methods:

Nineteen subjects with well-controlled peripheral blood pressure on stable doses of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker had aldosterone levels checked and central blood pressure parameters measured using the SphygmoCor system. The central blood pressure parameters of subjects with or without breakthrough, defined as serum aldosterone >15 ng/dl, were compared.

Results:

Of the 19 subjects, six had breakthrough with a mean aldosterone level of 33.8 ng/dl, and 13 were without breakthrough with a mean level of 7.1 ng/dl. There was no significant difference between the two groups in any central blood pressure parameter.

Conclusions:

We found no correlation between aldosterone breakthrough and central blood pressure. The clinical impact of aldosterone breakthrough likely depends on its non-genomic, pro-fibrotic, pro-inflammatory effects rather than its regulation of extracellular volume.

2016 European Society of Hypertension guidelines for the management of high blood pressure in children and adolescents

Increasing prevalence of hypertension (HTN) in children and adolescents has become a significant public health issue driving a considerable amount of research. Aspects discussed in this document include advances in the definition of HTN in 16 year or older, clinical significance of isolated systolic HTN in youth, the importance of out of office and central blood pressure measurement, new risk factors for HTN, methods to assess vascular phenotypes, clustering of cardiovascular risk factors and treatment strategies among others. The recommendations of the present document synthesize a considerable amount of scientific data and clinical experience and represent the best clinical wisdom upon which physicians, nurses and families should base their decisions. In addition, as they call attention to the burden of HTN in children and adolescents, and its contribution to the current epidemic of cardiovascular disease, these guidelines should encourage public policy makers to develop a global effort to improve identification and treatment of high blood pressure among children and adolescents.

Contribution of backward and forward wave pressures to age-related increases in aortic pressure in a community sample not receiving antihypertensive therapy

Reports on the contribution of aortic forward (Pf) and backward (Pb) wave pressures to age-related increases in central aortic pulse pressure (PPc) have been confounded by the use of participants receiving antihypertensive therapy. We assessed the relative contribution of Pf and Pb to age-related increases in PPc (radial applanation tonometry and SphygmoCor software using an assumed triangular wave for wave separation analysis) in 892 community participants not receiving antihypertensive therapy. We validated our results using aortic flow waves (echocardiography) for wave separation analysis in 254 of these participants. In multivariate regression models in those aged <50 years, adjustments for both Pb and a Pf-independent measure of reflected wave function (RM = Pb/Pf), but not Pf abolished the impact of age on PPc. However, in those aged >50 years, adjustments for Pf (β-coefficient: 0.25 ± 0.06 vs. 0.74 ± 0.08; P < .0001) and Pb (0.04 ± 0.04 vs. 0.74 ± 0.08; P < .0001), but not RM markedly decreased the relationship between age and PPc. On product of coefficient mediation analysis, whether assessed in men or in women, in those participants aged <50 years, independent of several confounders and mean arterial pressure, Pb (P < .005), but not Pf contributed to age-related increases in PPc. In contrast, in those participants aged ≥50 years, independent of several confounders and mean arterial pressure, Pb (P < .005) and Pf (P < .01) contributed to age-related increases in PPc, and Pb effects were markedly diminished by adjustments for Pf (0.26 ± 0.002 vs. 0.52 ± 0.003 mm Hg per year, P < .0001 for comparison). In conclusion, independent of the effects of antihypertensive therapy, aortic backward waves contribute to age-related increases in aortic PPc across the adult lifespan, but at an older age, this effect may be attributed in part to the impact of forward on backward wave pressures.

How to Measure 24-hour Central Blood Pressure and Its Potential Clinical Implications

The evaluation of 24-hour central blood pressure (24h cBP) combines the cBP non-invasive assessment with the 24-h ambulatory BP measurement. The major strength of the 24-h cBP evaluation is the ability to assess the degree of circadian changes between central and peripheral BP, namely 24-h BP amplification. This allows an accurate quantification of the degree of spatial and temporal BP variability in each single individual. BP amplification depends from a number of factors, such as the interaction between pressure and flow pulsatile motions, vasomotor tone, arterial tapering and other physiological and anthropometrical determinants. The assessment of 24-h BP amplification, a relatively pressure-independent parameter, may be helpful in better refining the risk of organ damage and future CV events over traditional measures of office and 24-h brachial BP. Currently, only few devices enable the assessment of 24-h cBP. These devices are based on peripheral (brachial or radial) BP waveform detection, and reconstruction of central BP waveform through mathematical models. The estimation of 24-h cBP imputed from multivariate regression equations was also proposed. Clinical data are still scarce and, although suggesting a possible superiority of 24-h cBP over brachial BP in the association with markers of organ damage, they are limited by methodological and technical aspects. There is urgent need of a standardized methodology and rigorous validation protocols for the 24-h cBP assessment. The field of 24-h cBP measurement still requires significant advancements of scientific knowledge before its introduction into clinical practice.

Genetic, physiological and comparative genomic studies of hypertension and insulin resistance in the spontaneously hypertensive rat

We previously mapped hypertension-related insulin resistance quantitative trait loci (QTLs) to rat chromosomes 4, 12 and 16 using adipocytes from F2 crosses between spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats, and subsequently identified Cd36 as the gene underlying the chromosome 4 locus. The identity of the chromosome 12 and 16 genes remains unknown. To identify whole-body phenotypes associated with the chromosome 12 and 16 linkage regions, we generated and characterised new congenic strains, with WKY donor segments introgressed onto an SHR genetic background, for the chromosome 12 and 16 linkage regions. We found a >50% increase in insulin sensitivity in both the chromosome 12 and 16 strains. Blood pressure and left ventricular mass were reduced in the two congenic strains consistent with the congenic segments harbouring SHR genes for insulin resistance, hypertension and cardiac hypertrophy. Integrated genomic analysis, using physiological and whole-genome sequence data across 42 rat strains, identified variants within the congenic regions in Upk3bl, RGD1565131 and AABR06087018.1 that were associated with blood pressure, cardiac mass and insulin sensitivity. Quantitative trait transcript analysis across 29 recombinant inbred strains showed correlation between expression of Hspb1, Zkscan5 and Pdgfrl with adipocyte volume, systolic blood pressure and cardiac mass, respectively. Comparative genome analysis showed a marked enrichment of orthologues for human GWAS-associated genes for insulin resistance within the syntenic regions of both the chromosome 12 and 16 congenic intervals. Our study defines whole-body phenotypes associated with the SHR chromosome 12 and 16 insulin-resistance QTLs, identifies candidate genes for these SHR QTLs and finds human orthologues of rat genes in these regions that associate with related human traits. Further study of these genes in the congenic strains will lead to robust identification of the underlying genes and cellular mechanisms.

Summary: Comparative genome analyses identify candidate genes for hypertension and insulin resistance on rat chromosomes 12 and 16, and marked enrichment of insulin resistance genes in the syntenic regions of the human genome.

Is Noninvasive Brachial Systolic Blood Pressure an Accurate Estimate of Central Aortic Systolic Blood Pressure?

OBJECTIVES

Noninvasive brachial systolic blood pressure (nSBP-B) usually approaches invasive central systolic blood pressure (iSBP-C) with a high correlation. Whether nSBP-B is an accurate estimate of iSBP-C remained to be investigated. Thus, this study aimed to compare the errors of nSBP-B and noninvasive central systolic blood pressure (nSBP-C) with different techniques in estimating iSBP-C.

METHODS

Simultaneous invasive high-fidelity central aortic pressure waveforms and the noninvasive left brachial pulse volume recording (PVR) waveform were recorded in a Generation group ( N = 40) and a Validation group ( N = 100). The accuracy of the noninvasive estimates of iSBP-C obtained from analysis of the calibrated PVR waveform using the generalized transfer function (GTF), pulse waveform analysis (PWA), and N-point moving average (NPMA) methods was examined in the Validation group by calculating the mean absolute error (MAE).

RESULTS

In Generation group, the MAE was 4.6±4.1mm Hg between nSBP-B and invasive brachial SBP, and 6.8±5.5mm Hg between nSBP-B and iSBP-C. In comparison, the MAE of between iSBP-C and nSBP-C with PWA, NPMA, and GTF were 5.5±4.5, 5.8±4.9, and 5.9±5.0mm Hg, respectively. In Validation group, the MAE of nSBP-B (6.9±4.6mm Hg) for estimating iSBP-C was significantly greater than that of PWA (5.0±3.4mm Hg) and NPMA (6.1±4.4mm Hg), and GTF (6.1±4.9mm Hg). The percentage of absolute band error ≤5mm Hg was 62% for nSBP-B, 69% for GTF, 83% for PWA, and 69% for NPMA.

CONCLUSIONS

The accuracy of nSBP-B was inferior to the n SBP-C measures in estimating iSBP-C.

Aerobic Exercise Training and Arterial Changes in African Americans versus Caucasians

African Americans (AA) have increased carotid artery intima-media thickness and decreased vascular function compared with their Caucasian (CA) peers. Aerobic exercise prevents and potentially reverses arterial dysfunction.

PURPOSE

The purpose of this study was to examine the effect of 8 wk of moderate- to high-intensity aerobic training in young healthy sedentary AA and CA men and women.

METHODS

Sixty-four healthy volunteers (men, 28; women, 36) with mean age 24 yr underwent measures of arterial structure, function, and blood pressure (BP) variables at baseline, after the 4-wk control period, and 8 wk after training.

RESULTS

There was a significant increase in VO2peak among both groups after exercise training. Brachial systolic BP decreased significantly after the control period in both groups but not after exercise training. Carotid pulse pressure decreased significantly in both groups after exercise training as compared with that in baseline. There was no change in any of the other BP variables. AA had higher intima-media thickness at baseline and after the control period but it significantly decreased after exercise training compared with that of CA. AA had significantly lower baseline forearm blood flow and reactive hyperemia compared with those of CA, but exercise training had no effect on these variables. There was no significant difference in arterial stiffness (central pulse wave velocity) and wave-reflection (augmentation index) between the two groups at any time point.

CONCLUSIONS

This is the first study to show that 8 wk of aerobic exercise training causes significant improvement in the arterial structure in young, healthy AA, making it comparable with the CA and with minimal effects on BP variables.

Different associations between blood pressure indices and carotid artery damages in a community-based population of China

Different blood pressure (BP) indices had varying associations with carotid intima-media thickness (cIMT) and plaques in clinical practice. However, insufficient evidence has focused on this issue, especially in Chinese population. Herein we examined associations of different BP indices with cIMT and plaques cross-sectionally in a community-based atherosclerosis cohort. We qualitatively measured cIMT and plaques, and also measured central systolic blood pressure and brachial systolic blood pressure (baSBP), from which pulse pressure (PP), and second PP (PP2) were calculated. Logistic multivariate regression was used to assess the associations with BP indices and carotid artery hypertrophy (increased cIMT) and the extent of atherosclerosis (presence of plaques). Each BP index was significantly and independently associated with increased cIMT and plaques except the association of baSBP with plaques. When every two BP indices were put into one model, brachial pressure indices were associated with increased cIMT independently of central pressures, whereas the association between central pressure indices and plaque presence were stronger than those of brachial pressures. In addition, SBP indices were associated with increased cIMT independently of PP indices, whereas PP indices were more strongly related to plaques. In conclusion, central and PP indices might be associated with plaques; however, brachial and SBP indices might be associated with increased cIMT. Nevertheless, whether these BP indices predict increased cIMT and plaque progression warrants further longitudinal and laboratory studies.

Noninvasive Central Systolic Blood Pressure Is More Strongly Related to Kidney Function Decline Than Peripheral Systolic Blood Pressure in a Chinese Community-Based Population

This study aimed to investigate the association of noninvasive central aortic blood pressure with kidney function decline in a Chinese community-based population with normal kidney function at baseline. A total of 3153 Chinese participants from an atherosclerosis cohort were included in our analysis. The primary outcome was renal function decline defined as a drop in estimated glomerular filtration rate (eGFR) category accompanied by a ≥25% drop in eGFR from baseline; or a sustained decline in eGFR of >5 mL/min per 1.73 m(2)/y. The secondary outcomes were rapid eGFR decline (a decline in eGFR of >3 mL/min per 1.73 m(2)/y) and new incidence of chronic kidney disease. Participants were 56.6±8.5 years old, 36.0% were males, and 48.8% had hypertension. Mean (SD) baseline eGFR was 101.2±10.6 mL/min per 1.73 m(2) After a mean 2.35-year follow-up, the incidence of renal function decline, rapid eGFR decline and chronic kidney disease were 7.3%, 19.7%, and 0.7%, respectively. In multivariate logistic-regression analyses, central and peripheral systolic blood pressure (SBP) were both independently associated with all outcomes after adjustment for various confounders. When peripheral SBP was forced into the model with central SBP simultaneously, its significant association with the 3 outcomes all disappeared; however, central SBP was still significantly related with all outcomes even after further adjusting peripheral SBP. In conclusion, central SBP is a stronger predictor compared with peripheral SBP for early kidney function decline in a Chinese community-based population with normal kidney function at baseline.

Brachial Pressure Control Fails to Account for Most Distending Pressure-Independent, Age-Related Aortic Hemodynamic Changes in Adults

BACKGROUND

Although several characteristics of aortic function, which are largely determined by age, predict outcomes beyond brachial blood pressure (BP), the extent to which brachial BP control accounts for age-related variations in aortic function is uncertain. We aimed to determine the extent to which brachial BP control in the general population (systolic/diastolic BP < 140/90 mm Hg) accounts for age-related aortic hemodynamic changes across the adult lifespan.

METHODS

Central aortic pulse pressure (PPc), backward wave pressure (Pb), pulse wave velocity (PWV), and PP amplification (PPamp) (applanation tonometry and SphygmoCor software) were determined in 1,185 participants from a community sample (age >16 years; 36.4% uncontrolled BP).

RESULTS

With adjustments for distending pressure (mean arterial pressure, MAP), no increases in PPc, Pb, or PWV and decreases in PPamp were noted in those with an uncontrolled brachial BP younger than 50 years. In those older than 50 years with an uncontrolled brachial BP, MAP-adjusted aortic hemodynamic variables were only modestly different to those with a controlled brachial BP (PPc, 46±14 vs. 42±15 mm Hg, P < 0.02, Pb, 23±8 vs. 21±8 mm Hg, PWV, 8.42±3.21 vs. 8.19±3.37 m/second, PPamp, 1.21±0.17 vs. 1.21±0.14). Nonetheless, with adjustments for MAP, marked age-related increases in PPc, Pb, and PWV and decreases in PPamp were noted in those with uncontrolled and controlled brachial BP across the adult lifespan (P < 0.0001).

CONCLUSION

Brachial BP control in the general population fails to account for most distending pressure-independent, age-related changes in aortic hemodynamics across the adult lifespan.

Central Pressure Appraisal: Clinical Validation of a Subject-Specific Mathematical Model

Introduction

Current evidence suggests that aortic blood pressure has a superior prognostic value with respect to brachial pressure for cardiovascular events, but direct measurement is not feasible in daily clinical practice.

Aim

The aim of the present study is the clinical validation of a multiscale mathematical model for non-invasive appraisal of central blood pressure from subject-specific characteristics.

Methods

A total of 51 young male were selected for the present study. Aortic systolic and diastolic pressure were estimated with a mathematical model and were compared to the most-used non-invasive validated technique (SphygmoCor device, AtCor Medical, Australia). SphygmoCor was calibrated through diastolic and systolic brachial pressure obtained with a sphygmomanometer, while model inputs consist of brachial pressure, height, weight, age, left-ventricular end-systolic and end-diastolic volumes, and data from a pulse wave velocity study.

Results

Model-estimated systolic and diastolic central blood pressures resulted to be significantly related to SphygmoCor-assessed central systolic (r = 0.65 p <0.0001) and diastolic (r = 0.84 p<0.0001) blood pressures. The model showed a significant overestimation of systolic pressure (+7.8 (-2.2;14) mmHg, p = 0.0003) and a significant underestimation of diastolic values (-3.2(-7.5;1.6), p = 0.004), which imply a significant overestimation of central pulse pressure. Interestingly, model prediction errors mirror the mean errors reported in large meta-analysis characterizing the use of the SphygmoCor when non-invasive calibration is performed.

Conclusion

In conclusion, multi-scale mathematical model predictions result to be significantly related to SphygmoCor ones. Model-predicted systolic and diastolic aortic pressure resulted in difference of less than 10 mmHg in the 51% and 84% of the subjects, respectively, when compared with SphygmoCor-obtained pressures.

Association of Central Versus Brachial Blood Pressure With Target-Organ Damage: Systematic Review and Meta-Analysis

Accumulating evidence suggests that central blood pressure (BP) may reflect the hemodynamic stress on target organs more accurately than brachial BP. A systematic review assessing the relationship of central versus brachial BP with preclinical target-organ damage was performed. Meta-analysis of cross-sectional data showed that central compared with brachial systolic BP was more closely associated with (1) left ventricular mass index (12 studies, n=6431; weighted age [SD], 49.9 [13.1] years; 51% hypertensives): pooled correlation coefficients r=0.30; 95% confidence interval (CI), 0.23-0.37 versus r=0.26; 95% CI, 0.19-0.33, respectively; P<0.01 for difference; (2) carotid intima-media thickness (7 studies, n=6136; weighted age, 55.6 [13.2] years; 48% hypertensives): r=0.27; 95% CI, 0.19-0.34 versus r=0.23; 95% CI, 0.16-0.30, respectively; P<0.01 for difference; (3) pulse-wave velocity (14 studies, n=3699; weighted age, 53.9 [13.3] years; 53% hypertensives): r=0.42; 95% CI, 0.37-0.47 versus r=0.39; 95% CI, 0.33-0.45, respectively; P<0.01 for difference. Four studies assessing urine albumin excretion (n=3718; weighted age, 56.4 [5] years; 69% hypertensives) reported similar correlations (P=not significant) with central (r=0.22; 95% CI, 0.14-0.29) and brachial systolic BP (r=0.22; 95% CI, 0.12-0.32). Similar findings were observed for central compared with brachial pulse pressure in terms of relationship with target-organ damage. Metaregression analyses did not reveal any significant effect of age. In conclusion, central compared with brachial BP seems to be more strongly associated with most of the investigated indices of preclinical organ damage.

American Society of Hypertension position paper: central blood pressure waveforms in health and disease

A number of devices are available which noninvasively estimate central aortic blood pressure using a variety of approaches such as tonometry or oscillometry. In this position paper, we discuss how the central pressure waveform is generated and measured, how central pressure waveforms appear in health and disease, the predictive value of central blood pressure measurements, the effects of interventions on waveforms, and areas of future need in this field of clinical and research endeavor.

The structural factor of hypertension: large and small artery alterations

Pathophysiological studies have extensively investigated the structural factor in hypertension, including large and small artery remodeling and functional changes. Here, we review the recent literature on the alterations in small and large arteries in hypertension. We discuss the possible mechanisms underlying these abnormalities and we explain how they accompany and often precede hypertension. Finally, we propose an integrated pathophysiological approach to better understand how the cross-talk between large and small artery changes interacts in pressure wave transmission, exaggerates cardiac, brain and kidney damage, and lead to cardiovascular and renal complications. We focus on patients with essential hypertension because this is the most prevalent form of hypertension, and describe other forms of hypertension only for contrasting their characteristics with those of uncomplicated essential hypertension.

Central aortic blood pressure from ultrasound wall-tracking of the carotid artery in children: comparison with invasive measurements and radial tonometry

Differences between central aortic root (c) and peripheral (p) systolic blood pressure (SBP) may be particularly marked in children, but noninvasive methods for assessing cSBP in children have not been validated. We compared estimates of cSBP obtained from radiofrequency ultrasound wall tracking of the carotid artery (ART.LAB system) with that measured directly by a catheter in the aortic root at the time of arterial cannulation. Carotid waveforms were calibrated from invasive measurements of mean and diastolic pressures. In 9 children aged 10.5 ± 5.0 years (mean ± SD), cSBP obtained from carotid wall tracking was highly correlated with invasive measures of cSBP (r=0.99) with mean (± SD) difference 3.9 ± 2.5 mm Hg. Second, we compared values of cSBP obtained from the carotid with those obtained using noninvasive applanation tonometry at the radial artery and a radial-to-aortic transfer function (SphygmoCor). Both carotid and radial tonometric measurements were calibrated from the same peripheral mean and diastolic measurements of blood pressure obtained by sphygmomanometry. In 84 children aged 13.2 ± 3.2 years, there was excellent agreement between the 2 methods (r=0.95; P<0.001) with mean difference 0.71 ± 3.7 mm Hg (95% confidence interval =-1.53 to 1.01). This invasive validation study confirms that cSBP as estimated by carotid wall tracking provides an acceptable measurement of true cSBP when calibration is from true mean and diastolic pressures. Close agreement of cSBP obtained by carotid wall tracking and radial tonometry suggests that these provide similar results when calibrated from the same peripheral blood pressure measurements.

Central aortic reservoir-wave analysis improves prediction of cardiovascular events in elderly hypertensives

Several morphological parameters based on the central aortic pressure waveform are proposed as cardiovascular risk markers, yet no study has definitively demonstrated the incremental value of any waveform parameter in addition to currently accepted biomarkers in elderly, hypertensive patients. The reservoir-wave concept combines elements of wave transmission and Windkessel models of arterial pressure generation, defining an excess pressure superimposed on a background reservoir pressure. The utility of pressure rate constants derived from reservoir-wave analysis in prediction of cardiovascular events is unknown. Carotid blood pressure waveforms were measured prerandomization in a subset of 838 patients in the Second Australian National Blood Pressure Study. Reservoir-wave analysis was performed and indices of arterial function, including the systolic and diastolic rate constants, were derived. Survival analysis was performed to determine the association between reservoir-wave parameters and cardiovascular events. The incremental utility of reservoir-wave parameters in addition to the Framingham Risk Score was assessed. Baseline values of the systolic rate constant were independently predictive of clinical outcome (hazard ratio, 0.33; 95% confidence interval, 0.13-0.82; P=0.016 for fatal and nonfatal stroke and myocardial infarction and hazard ratio, 0.38; 95% confidence interval, 0.20-0.74; P=0.004 for the composite end point, including all cardiovascular events). Addition of this parameter to the Framingham Risk Score was associated with an improvement in predictive accuracy for cardiovascular events as assessed by the integrated discrimination improvement and net reclassification improvement indices. This analysis demonstrates that baseline values of the systolic rate constant predict clinical outcomes in elderly patients with hypertension and incrementally improve prognostication of cardiovascular events.