Relationship between augmentation index obtained from carotid and radial artery pressure waveforms

Central blood pressure and peripheral augmentation index following acute submaximal arm versus leg exercise

BACKGROUND

Aerobic exercises like running and cycling may lower cardiovascular disease (CVD) risk through favorable effects on central blood pressure and vascular function. Arm ergometry is a popular exercise modality used in rehabilitation settings, but little is known regarding the central hemodynamic and vascular effects of this form of exercise.

PURPOSE

To compare the acute effects of leg versus arm exercise on central blood pressure and vascular function.

METHODS

Twenty-one participants (n = 11 female, Age 21 ± 3, BMI 24.5 ± 3.2 kg/m2) completed two visits to the Human Performance Laboratory. Central systolic blood pressure (cSBP), central diastolic blood pressure (cDBP), and peripheral augmentation index (pAIx) were measured using a brachial oscillometric blood pressure cuff with measures being taken before and after 20 min of acute moderate-intensity (submaximal) arm or leg cycling exercise.

RESULTS

There was a condition-by-time interaction for pAIx (p = 0.011). pAIx slightly increased following arm exercise but significantly decreased following leg exercise. There was a condition-by-time interaction for cDBP (p = 0.011). cDBP significantly decreased following arm exercise but increased immediately following leg exercise. There was no condition-by-time interaction for cSBP (p = 0.721). There were similar acute increases in cSBP immediately post-exercise for both conditions.

CONCLUSION

Arm exercise increased pAlx and decreased cDBP compared to leg exercise. As an increase in pAIx may increase left ventricular work and a reduction in cDBP may reduce coronary perfusion pressure, these findings suggest that a single bout of arm exercise may not have the same favorable acute effect on central hemodynamic load as a single bout of leg exercise.

Beat-to-beat analysis of hemodynamic response to mental and psychological stress in sickle cell anemia

Objectives

Vaso-occlusive crises (VOCs) are a hallmark symptom of sickle cell disease (SCD). Physical stressors can trigger decreased microvascular blood flow and increase the risk for VOCs. However, the effect of mental and psychological stressors on vascular physiology in SCD is not well-established. We hereby examined fluctuations in continuous blood pressure (BP) to evaluate hemodynamic changes in SCD patients during mental and psychological stress.

Methods

Thirteen SCD (HbSS) subjects from the Children's Hospital Los Angeles and 11 healthy (HbAA) volunteers were recruited. Continuous BP was recorded as subjects participated in two mental and one psychological stress tasks. Systolic beat-to-beat BP variability (BPV) measurements were calculated for each subject. Three very short-term BPV metrics served as outcome measures: standard deviation, coefficient of variation, and average real variability. Linear mixed effects models evaluated associations between patient factors and outcome measures.

Results

SCD patients were associated with increased systolic BPV and exhibited a distinct increase in BPV in response to psychological stress. All subjects exhibited a decrease in systolic BPV in response to mental stress tasks. During mental stress, both groups displayed increased augmentation index, reflective of stress-induced vasoconstriction, while psychological stress in SCD patients led to both decreased mean arterial pressure and increased AI, suggestive of uncompensated vasoconstriction.

Conclusion

These findings emphasize the impact of mental and psychological stressors on vascular function in SCD, the potential for monitoring physiological signals to predict VOC events, and the importance of counseling SCD patients on lifestyle practices to reduce their stress to prevent pain.

Pulse signal may be a key bridge connecting cardiology and pulse diagnosis of TCM

Objective

This study extracts atherosclerosis indices from six channels of C u n k o u and discusses the data distribution, aims to explore the connection between cardiology of modern medicine (MM) and traditional Chinese medicine (TCM) pulse diagnosis.

Methods

We use a device capable of simultaneously collecting the pulse signals of the Cun, G u a n and Chi to test the population participating in routine physical examinations. Firstly, we collected pressure pulse waves from six channels of C u n k o u of 1045 healthy subjects (578 men and 467 women, average age=37.99±16.02 years). Secondly, we extracted the two most common arteriosclerosis indices pulse transit time (PTT) and Augmentation index (AIx) from six-channel pulse waves. Lastly, T-test and correlation test were taken to analyze the differences and relevance of the atherosclerosis indices extracted from six channels of C u n k o u .

Results

When analyzing AIx and PTT at different wrist, it was found that AIx of left wrist is significantly higher than that of right wrist (P<0.001), while the PTT of left wrist is significantly lower than that of right wrist (P<0.001), a phenomenon that is common in both men and women. Furthermore, regardless of whether it is left or right wrist, the AIx at Chi channel is higher than that at Cun (P<0.05) and G u a n (P<0.05). At the same time, the PTT at G u a n is bigger than that at Cun in two wrists (P<0.05). However, when the specific channel is not considered, there is no significant difference in AIx and PTT between each channel and the corresponding wrist (P>0.05). In addition, regardless of gender, when the specific channel is not considered, AIx and PTT of each wrist are significantly correlated with age (P<0.001).

Conclusions

The differences of the atherosclerosis indices AIx and PTT in six channels support that the method of six-channel pulse diagnosis is indispensable in TCM. Additionally, the pulse waves obtained from each channel can be utilized as a dependable foundation for diagnosing atherosclerotic conditions. This study is beneficial for promoting the integration of TCM and MM in diagnosing disease.

An in silico study of the effects of cardiovascular aging on carotid flow waveforms and indexes in a virtual population

Cardiovascular aging is strongly associated with increased risk of cardiovascular disease and mortality. Moreover, health and lifestyle factors may accelerate age-induced alterations, such as increased arterial stiffness and wall dilation, beyond chronological age, making the clinical assessment of cardiovascular aging an important prompt for preventative action. Carotid flow waveforms contain information about age-dependent cardiovascular properties, and their ease of measurement via noninvasive Doppler ultrasound (US) makes their analysis a promising tool for the routine assessment of cardiovascular aging. In this work, the impact of different aging processes on carotid waveform morphology and derived indexes is studied in silico, with the aim of establishing the clinical potential of a carotid US-based assessment of cardiovascular aging. One-dimensional (1-D) hemodynamic modeling was employed to generate an age-specific virtual population (VP) of N = 5,160 realistic carotid hemodynamic waveforms. The resulting VP was statistically validated against in vivo aging trends in waveforms and indexes from the literature, and simulated waveforms were studied in relation to age and underlying cardiovascular parameters. In our study, the carotid flow augmentation index (FAI) significantly increased with age (with a median increase of 50% from the youngest to the oldest age group) and was strongly correlated to local arterial stiffening (r = 0.94). The carotid pulsatility index (PI), which showed less pronounced age variation, was inversely correlated with the reflection coefficient at the carotid branching (r = -0.88) and directly correlated with carotid net forward wave energy (r = 0.90), corroborating previous literature where it was linked to increased risk of cerebrovascular damage in the elderly. There was a high correlation between corrected carotid flow time (ccFT) and cardiac output (CO) (r = 0.99), which was not affected by vascular age. This study highlights the potential of carotid waveforms as a valuable tool for the assessment of cardiovascular aging.NEW & NOTEWORTHY An age-specific virtual population was generated based on a 1-D model of the arterial circulation, including newly defined literature-based specific age variations in carotid vessel properties. Simulated carotid flow/velocity waveforms, indexes, and age trends were statistically validated against in vivo data from the literature. A comprehensive study of the impact of aging on carotid flow waveform morphology was performed, and the mechanisms influencing different carotid indexes were elucidated. Notably, flow augmentation index (FAI) was found to be a strong indicator of local carotid stiffness.

Rapid Prototyping Flexible Capacitive Pressure Sensors Based on Porous Electrodes

Flexible pressure sensors are widely applied in tactile perception, fingerprint recognition, medical monitoring, human-machine interfaces, and the Internet of Things. Among them, flexible capacitive pressure sensors have the advantages of low energy consumption, slight signal drift, and high response repeatability. However, current research on flexible capacitive pressure sensors focuses on optimizing the dielectric layer for improved sensitivity and pressure response range. Moreover, complicated and time-consuming fabrication methods are commonly applied to generate microstructure dielectric layers. Here, we propose a rapid and straightforward fabrication approach to prototyping flexible capacitive pressure sensors based on porous electrodes. Laser-induced graphene (LIG) is produced on both sides of the polyimide paper, resulting in paired compressible electrodes with 3D porous structures. When the elastic LIG electrodes are compressed, the effective electrode area, the relative distance between electrodes, and the dielectric property vary accordingly, thereby generating a sensitive pressure sensor in a relatively large working range (0-9.6 kPa). The sensitivity of the sensor is up to 7.71%/kPa^-1, and it can detect pressure as small as 10 Pa. The simple and robust structure allows the sensor to produce quick and repeatable responses. Our pressure sensor exhibits broad potential in practical applications in health monitoring, given its outstanding comprehensive performance combined with its simple and quick fabrication method.

Sex modification of the association of the radial augmentation index and incident hypertension in a Chinese community-based population

BACKGROUND

Arterial stiffness, as assessed by aortic ultrasound and pulse wave velocity, is associated with incident hypertension. However, there is still no consensus on whether the augmentation index (AI) affects new onset of hypertension. This study investigated the relationship of radial AI (rAI) and incident hypertension in a Chinese community-based population without hypertension at baseline.

METHOD

A total of 1,615 Chinese non-hypertensive participants from an atherosclerosis cohort in Beijing, China were included in our analysis. Baseline rAI normalized to heart rate of 75 beats/min (rAIp75) was obtained using HEM-9000AI. New-onset hypertension was defined as blood pressure ≥ 140/90 mmHg or self-reported hypertension or taking anti-hypertensive medications at the follow up survey. Multivariate regression models were used to evaluate the impact of rAIp75 on the risk of new-onset hypertension.

RESULTS

After a mean 2.35-year follow-up, 213 (13.19%) participants developed incident hypertension. No significant relation between rAIp75 and incident hypertension was observed in the whole population after adjustment for possible confounders (adjusted odds ratio (OR) and 95% confidence interval (CI): 1.09 [0.95-1.27];P = 0.2260). However, rAIp75 was significantly associated with incident hypertension in women, but not in men (adjusted OR and 95% CI: 1.29 [1.06-1.56],P = 0.0113 for women; 0.91 [0.72-1.15],P = 0.4244 for men; P for interaction = 0.0133).

CONCLUSIONS

Sex modified the effect of the rAI on incident hypertension in a Chinese, community-based, non-hypertensive population. Screening of the rAI could be considered in women with a high risk of hypertension for the purpose of primary intervention.

High-performance wearable strain sensors based on fragmented carbonized melamine sponges for human motion detection

Strain sensors with a large strain sensing range and high sensitivity are in high demand due to their various potential applications ranging from human motion detection to soft robotics. In this study, high-performance strain sensors are developed by fragmenting carbonized melamine sponges that are commercially available. The strain sensors, based on fragmented carbonized melamine sponges (FCMS), demonstrate high sensitivity with a gauge factor (GF) of 18.7 at an FCMS density of 1.07 mg cm^-2 and a large strain sensing range of up to 80%. As a comparison, the strain sensor based on unfragmented carbonized melamine sponges has only a GF of ∼8.0 and limited stretchability (<7%). In situ tension tests indicate that the strain-response mechanism of the sensor is mainly ascribed to the reorientation of individual FCMS at low strains (<40%), while crack propagation dominates the strain-response behavior of the sensor at strains larger than 40%. The high sensitivity and large strain sensing range of the sensor, as well as the low-cost and scalable fabrication method, enable diverse applications. It can not only detect large-strain human arthrosis movements, but it also exhibits the capability to monitor subtle human physiological activity.

Diastolic Augmentation Index Improves Radial Augmentation Index in Assessing Arterial Stiffness

Arterial stiffness is an important risk factor for cardiovascular events. Radial augmentation index (AI_r) can be more conveniently measured compared with carotid-femoral pulse wave velocity (cfPWV). However, the performance of AI_r in assessing arterial stiffness is limited. This study proposes a novel index AI_rd, a combination of AI_r and diastolic augmentation index (AI_d) with a weight α, to achieve better performance over AI_r in assessing arterial stiffness. 120 subjects (43 ± 21 years old) were enrolled. The best-fit α is determined by the best correlation coefficient between AI_rd and cfPWV. The performance of the method was tested using the 12-fold cross validation method. AI_rd (r = 0.68, P < 0.001) shows a stronger correlation with cfPWV and a narrower prediction interval than AI_r (r = 0.61, P < 0.001), AI_d (r = −0.17, P = 0.06), the central augmentation index (AI_c) (r = 0.61, P < 0.001) or AI_c normalized for heart rate of 75 bpm (r = 0.65, P < 0.001). Compared with AI_r (age, P < 0.001; gender, P < 0.001; heart rate, P < 0.001; diastolic blood pressure, P < 0.001; weight, P = 0.001), AI_rd has fewer confounding factors (age, P < 0.001; gender, P < 0.001). In conclusion, AI_rd derives performance improvement in assessing arterial stiffness, with a stronger correlation with cfPWV and fewer confounding factors.

Primary study for detection of arterial blood pressure waveform components

The paper presents a technique to detect significant systolic peaks, the percussion (P) and tidal peak (T) and diastolic peak (D) from the arterial blood pressure (ABP) waveform. The technique is aimed at robust detection even in presence of significant noise. Singular Value Decomposition (SVD) based dominant period extraction of the ABP waveform followed by wavelet transform and local peak detection is applied to detect the points of interest. MIMIC-II ABP databse serves as a training dataset to select SVD and wavelet transform parameters and CSL Benchmark database is used to analyze the technique. Salient systolic peak detection for the CSL dataset was performed with positive predictive value and sensitivity figures of 98.48% and 99.24% respectively.

The Relationships Between the Arterial Stiffness Index Measured at the Radial Artery and Left Ventricular Diastolic Dysfunction in Asymptomatic High Risk Patients Without Atherosclerotic Cardiovascular Disease

Arterial stiffness is associated with atherosclerosis and left ventricular (LV) diastolic function in general or hypertensive patients. However, the relationships between the arterial stiffness index measured at the radial artery and LV diastolic dysfunction in asymptomatic high-risk patients without atherosclerotic cardiovascular disease (ASCVD) have not been fully established.A total 532 statin-naïve patients (male:female ratio, 230:302, mean age, 56.0 ± 9.2 years) without ASCVD were enrolled from among subjects who simultaneously underwent transthoracic echocardiography and noninvasive semiautomated radial artery applanation tonometry from July 2011 to May 2014. Of these patients, 213 were categorized as the statin benefit group (Benefit) according to guidelines for blood cholesterol treatment, and the rest were placed in the nonbenefit control group (NoBenefit). Each group was subdivided into two groups (Y or N) according to antihypertensive medication administration. Thus, there were 4 groups: BenefitN (n = 80), BenefitY (n = 133), NoBenefitN (n = 251), and NoBenefitY (n = 68). There were significant differences in echocardiographic parameters of LV function and indices of arterial stiffness between the Benefit and NoBenefit groups. After adjusting for several risk factors, independent significant associations between echocardiographic parameters of LV diastolic function and arterial indices were identified with multivariate linear regression analysis in the Benefit patients.Parameters of arterial stiffness measured at the radial artery are associated with echocardiographic indices of LV diastolic function in asymptomatic high-risk patients without ASCVD. Therapies that prevent progression of arterial stiffness and reduce late-systolic pressure overload may help to reduce the prevalence of LV diastolic dysfunction in this population.

Arterial Stiffness, Central Pulsatile Hemodynamic Load, and Orthostatic Hypotension

The association between central pulsatile hemodynamic load, arterial stiffness, and orthostatic hypotension (OH) is unclear. The authors recruited 1099 participants from the community. Questionnaire, physical examination, and laboratory tests were performed. To assess the correlation between central pulsatile hemodynamic load, arterial stiffness, and OH, multiple logistic regression analysis was performed, and the discriminatory power was assessed by the area under the receiver operating curve. The prevalence of OH in this population was 5.6%. After adjusting for potential confounders, brachial-ankle pulse wave velocity (BaPWV) was significantly and positively correlated with OH in both the hypertension and nonhypertension groups (all P<.05), while central systolic blood pressure (CSBP) was only significantly associated with OH in the hypertension subgroup. In addition, BaPWV seemed to have a better discriminatory power than CSBP in both subgroups. BaPWV appears to be a better indicator of OH than CSBP in routine clinical practice.

Evaluation of 24-Hour Arterial Stiffness Indices and Central Hemodynamics in Healthy Normotensive Subjects versus Treated or Untreated Hypertensive Patients: A Feasibility Study

Objective. Central blood pressure (BP) and vascular indices estimated noninvasively over the 24 hours were compared between normotensive volunteers and hypertensive patients by a pulse wave analysis of ambulatory blood pressure recordings. Methods. Digitalized waveforms obtained during each brachial oscillometric BP measurement were stored in the device memory and analyzed by the validated Vasotens technology. Averages for the 24 hours and for the awake and asleep subperiods were computed. Results. 142 normotensives and 661 hypertensives were evaluated. 24-hour central BP, pulse wave velocity (PWV), and augmentation index (AI) were significantly higher in the hypertensive group than in the normotensive group (119.3 versus 105.6 mmHg for systolic BP, 75.6 versus 72.3 mmHg for diastolic BP, 10.3 versus 10.0 m/sec for aortic PWV, −9.7 versus −40.7% for peripheral AI, and 24.7 versus 11.0% for aortic AI), whereas reflected wave transit time (RWTT) was significantly lower in hypertensive patients (126.6 versus 139.0 ms). After adjusting for confounding factors a statistically significant between-group difference was still observed for central BP, RWTT, and peripheral AI. All estimates displayed a typical circadian rhythm. Conclusions. Noninvasive assessment of 24-hour arterial stiffness and central hemodynamics in daily life dynamic conditions may help in assessing the arterial function impairment in hypertensive patients.

Differences in effects of age and blood pressure on augmentation index

BACKGROUND

The effect of age on the augmentation index (AI) differs between young adults and the elderly, and the AI reaches a plateau after the age of 60 years. We examined whether the effects of age and an elevation in blood pressure on the AI differ between young adults and the elderly, between subjects with and without high blood pressure, or between subjects with and without a high AI.

METHODS

The radial AI was measured in 10,190 subjects who were either healthy or had hypertension (n = 5,477 men and 4,743 women).

RESULTS

In both sexes, a phased increase in the radial AI with age could only be confirmed up to an age of 60 years. A phased increase in the radial AI with the systolic blood pressure (SBP) could be confirmed up to an SBP of >170 mm Hg. Among subjects categorized within the highest age tertile, the highest SBP tertile, or the highest radial AI tertile, stepwise multivariable analyses demonstrated that SBP, but not age, was a significant independent factor influencing the radial AI.

CONCLUSIONS

The effect of age and blood pressure on AI differ not only between young adults and the elderly but also between those with and those without high blood pressure or between those with and those without a high AI. The effect of an elevation in blood pressure, but not aging, on the AI is significant in the elderly, in subjects with high blood pressure, or in those with a high AI.

Regular physical activity is associated with improved small artery distensibility in young to middle-age stage 1 hypertensives

The aim of the present study was to investigate the association of physical activity with small artery elasticity in the early stage of hypertension. We examined 366 young-to-middle-age stage 1 hypertensives (mean blood pressure 145.6±10.3/92.5±5.8 mmHg), divided into two categories of physical activity, sedentary (n=264) and non-sedentary (n=102) subjects. The augmentation index was measured using the Specaway DAT System. Small artery compliance (C2) was measured by applanation tonometry, at the radial artery, with an HDI CR2000 device. After 6 years of follow-up, arterial distensibility assessment was repeated in 151 subjects. Heart rate was lower in active than in sedentary subjects (71.2±8.9 vs 76.6±9.7 bpm, p<0.001). After adjusting for age, sex, heart rate, smoking, and blood pressure, C2 was higher (8.0±2.6 vs 6.4±3.0 ml/mmHg × 100, p=0.008) in non-sedentary than in sedentary patients. The augmentation index was smaller in the former (8.8±20.1 vs 16.8±26.5%, p=0.044) but the difference lost statistical significance after further adjustment for blood pressure. After 6 years, C2 was still higher in the non-sedentary than sedentary subjects. In addition, an improvement in the augmentation index accompanied by a decline in total peripheral resistance was found in the former. These data show that regular physical activity is associated with improved small artery elasticity in the early phase of hypertension. This association persists over time and is independent of blood pressure and heart rate.

A new tonometric device for radial augmentation index and subendocardial viability ratio: potential use in health screening

Augmentation index (AIx) and subendocardial viability ratio (SEVR) are widely accepted indices of wave reflection and myocardial oxygen demand relative to supply. This study aimed to validate a new tonometric device (IIM-2010A) for obtaining AIx and SEVR from radial artery. A total of 68 outpatients (32 men and 36 women) aged 20 to 76 years (44.7±16.6 years) recruited from a health screening center participated in the study. AIx was obtained from radial pressure using the HEM-9000AI and IIM-2010A devices, while SEVR was measured from carotid pressure with the tonometric method and from radial pressure by the IIM-2010A device. In a subgroup of 24 patients, the measurements of AIx and SEVR were repeated after an interval of 10 minutes. The correlation of radial AIx between the IIM-2010A and HEM-9000AI devices was highly significant (r=0.956, P<.01). Radial SEVR determined from IIM-2010A was also highly related to carotid SEVR (r=0.864, P<.01), although the value was about 13.1% lower. There was no statistically significant difference between the repeated measurements of both indices. The lower coefficient of variation (2.9% vs 4.3% for AIx, 3.3% vs 4.1% for SEVR) and higher intraclass correlation coefficient (0.96 vs 0.91 for AIx, 0.93 vs 0.86 for SEVR) of IIM-2010A confirmed better short-term reproducibility, compared with the HEM-9000AI device and carotid tonometry. The new tonometric device IIM-2010A is effective and reproducible in calculating radial AIx and SEVR and has potential use in health screening.

Abnormal pressure-wave reflection in pregnant women with chronic hypertension: association with maternal and fetal outcomes

The current study tested the hypothesis that abnormal pressure-wave reflection may have an important role in identifying pregnant women with chronic hypertension who might develop pre-eclampsia (PE) and/or fetal growth restriction. Pulse-wave analyses were performed to assess maternal arterial stiffness during 26-32 weeks of gestation in 41 women with chronic hypertension. We measured the central systolic pressure (CSP) and augmentation index (AIx) noninvasively using pulse waveforms of the radial artery with an automated applanation tonometric system. In a multiple regression analysis that included AIx-75 (AIx at a heart rate of 75 beats per minute), brachial systolic pressure, maternal height, smoking status, gestational age at testing and the presence of antihypertensive treatment at testing as independent determinants, AIx-75 was the only significant determinant of birth weight, whereas the brachial systolic pressure was not. In pregnant women with chronic hypertension who subsequently developed both superimposed PE and fetal growth restriction, CSP, AIx, AIx-75, and the brachial systolic and pulse pressures were all significantly higher than those who did not develop superimposed PE nor small for gestational age. In contrast, AIx-75 was the only significantly elevated hemodynamic parameter in patients who developed fetal growth restriction but not superimposed PE. In addition, CSP was the only significantly elevated hemodynamic parameter in patients who developed superimposed PE but not fetal growth restriction. Abnormal pressure-wave reflection during 26-32 weeks of gestation showed a stronger correlation with birth weight than conventional brachial blood pressure. Our findings might provide new insight into the pathophysiology of fetal growth restriction as well as superimposed PE in pregnancies complicated with chronic hypertension.

The clinical usefulness of central hemodynamics to evaluate diastolic dysfunction in subjects without hypertension

Objective

Diastolic dysfunction is associated with increased arterial stiffness in patients with hypertension. However, the role of arterial stiffness in diastolic dysfunction in subjects without hypertension has not been fully established.

Materials and methods

A total of 287 subjects (male:female ratio 121:166, mean age 53.0±14.4 years) without hypertension or any heart disease who simultaneously received transthoracic echocardiography and noninvasively semiautomated radial artery applanation tonometry (with an Omron HEM-9000AI) in the Department of Internal Medicine, St Vincent’s Hospital, from July 2011 to September 2012, were enrolled in this study.

Results

A total of 147 subjects (male:female ratio 59:88, mean age 61.7±9.9 years), representing 51.2% of the 287 subjects, had diastolic dysfunction (defined as abnormal relaxation pattern of mitral inflow). There were significant differences in systolic blood pressure (BP), pulse pressure, late systolic peak pressure (SBP₂), and radial augmentation index (RaAIx) between normal diastolic function and diastolic dysfunction. ΔBP was defined as systolic BP minus SBP₂, because of the difference in systolic BP between the two groups. ΔBP (odds ratio [OR] 1.059, 95% confidence interval [CI] 1.005–1.115; P=0.032) and RaAIx (odds ratio 1.027, 95% CI 1.009–1.044, P=0.003) were associated with diastolic dysfunction. A receiver operating-characteristic curve showed that ΔBP (area under the curve 0.875, 95% CI 0.832–0.911) and RaAIx (area under the curve 0.878, 95% CI 0.835–0.914) were associated with diastolic dysfunction.

Conclusion

We found that ΔBP and increased RaAIx were associated with diastolic dysfunction in subjects without hypertension after adjustment for age and sex. Therefore, it is suggested that noninvasive estimation of central BP may be useful to reflect diastolic dysfunction in subjects with normal peripheral BP.

Ivabradine therapy to unmask heart rate-independent effects of β-blockers on pulse wave reflections

BACKGROUND

Prior studies suggest that β-blockers lead to increased pulse wave reflections, thereby negating the blood pressure lowering effects on cardiovascular mortality. Parts of these effects may be induced by the heart rate reduction under β-blockade. The aim of this study was to unmask heart rate-independent effects of β-blockade on pulse wave reflections by switching therapy from β-blockers to ivabradine, an I f channel inhibitor without impact on systemic hemodynamics.

METHODS

14 male patients (age 61 ± 3 years, LVEF 62 ± 1 %) with arterial hypertension and coronary artery disease (CAD) under chronic β-blocker therapy at moderate dosage and additional renin-angiotensin system-blocking therapy were included. We determined radial augmentation index (rAI) by radial applanation tonometry in patients under β-blockade both at rest and during early recovery after exercise. β-Blockers were then replaced by ivabradine. Six weeks later, patients were re-tested at rest and after exercise under ivabradine therapy.

RESULTS

Mean heart rate (68 ± 3 vs. 63 ± 3 bpm; p = ns) and resting mean arterial pressure (98 ± 2 vs. 98 ± 2 mmHg; p = ns) were not different between β-blocker or ivabradine therapy, respectively. The rAI remained unchanged after switching therapy from β-blocker to ivabradine (86 ± 2 vs. 84 ± 4 %; p = ns). Post exercise, the rAI revealed an identical decrease in both groups (-7.2 ± 2.4 vs. -5.4 ± 2.5 %, p = ns). The increase in heart rate between resting conditions and early recovery post exercise was inversely correlated with the decrease of rAI under β-blockade (r = -0.70; p < 0.01) and showed a trend towards correlation under ivabradine (r = -0.52; p = 0.07).

CONCLUSION

In men at the age of 60 years and CAD, β-blockade does not exert heart rate-independent, pleiotropic effects on peripheral pulse wave reflections, both at rest or after exercise. Our results fit well within recent studies, demonstrating the fundamental influence of heart rate on rAI.

Association of resting heart rate with cardiovascular function: a cross-sectional study in 522 Finnish subjects

Background

High resting heart rate (HR) is associated with increased cardiovascular risk in general populations, possibly due to elevated blood pressure (BP) or sympathetic over-activity. We studied the association of resting HR with cardiovascular function, and examined whether the hemodynamics remained similar during passive head-up tilt.

Methods

Hemodynamics were recorded using whole-body impedance cardiography and continuous radial pulse wave analysis in 522 subjects (age 20–72 years, 261 males) without medication influencing HR or BP, or diagnosed diabetes, coronary artery, renal, peripheral arterial, or cerebrovascular disease. Correlations were calculated, and results analysed according to resting HR tertiles.

Results

Higher resting HR was associated with elevated systolic and diastolic BP, lower stroke volume but higher cardiac output and work, and lower systemic vascular resistance, both supine and upright (p < 0.05 for all). Subjects with higher HR also showed lower supine and upright aortic pulse pressure and augmentation index, and increased resting pulse wave velocity (p < 0.001). Upright stroke volume decreased less in subjects with highest resting HR (p < 0.05), and cardiac output decreased less in subjects with lowest resting HR (p < 0.009), but clear hemodynamic differences between the tertiles persisted both supine and upright.

Conclusions

Supine and upright hemodynamic profile associated with higher resting HR is characterized by higher cardiac output and lower systemic vascular resistance. Higher resting HR was associated with reduced central wave reflection, in spite of elevated BP and arterial stiffness. The increased cardiac workload, higher BP and arterial stiffness, may explain why higher HR is associated with less favourable prognosis in populations.

Trial registration

ClinicalTrials.gov, NCT01742702

A NEW METHOD FOR DETERMINING SUBENDOCARDIAL VIABILITY RATIO FROM RADIAL ARTERY PRESSURE WAVES

Aortic subendocardial viability ratio (SEVR), an index of myocardial oxygen demand relative to supply, has been used for the early detection of hemodynamic changes. We aimed to validate a new method for determining SEVR directly from radial pressures. Hemodynamic parameters were measured in 231 outpatients (108 males and 123 females) for physical examination, aged from 20–77 years (45.9 ± 17.3 years), including 210 healthy and 21 hypertensive subjects. Aortic SEVR was obtained using a validated device (SphygmoCor; AtCor Medical, Sydney, Australia), and radial SEVR was obtained using a portable vascular testing device (IIM-2010A; Institute and Intelligent of Machines, Hefei, China). Radial SEVR was strongly related to aortic SEVR (r = 0.824, p < 0.01), with approximately 15.7% lower value. Aortic and radial SEVR had similar independent predictors, including diastolic time fraction (DTF), systolic blood pressure, diastolic blood pressure, age, and height. DTF exerted the most influence on both of them. In healthy subjects, there were significant changes in aortic and radial SEVR between age groups in both males and females (p < 0.05 for both ). Changes in aortic and radial SEVR with aging were parallel though the differences between them increased. These results suggested that the simple and easily obtainable radial SEVR could provide equivalent information to aortic SEVR, and has potential for the primary prevention of cardiovascular disease in health screening.

Maternal arterial stiffness in normotensive pregnant women who subsequently deliver babies that are small for gestational age

OBJECTIVE

To assess the association between maternal arterial stiffness and delivery of a baby that is small for gestational age (SGA) in normotensive pregnant women.

STUDY DESIGN

Pulse wave analyses were performed to assess maternal arterial stiffness at 26-33 weeks of gestation in 40 normotensive women who subsequently delivered SGA babies (SGA group) and 111 normotensive women who delivered babies with normal growth (control group).

RESULTS

Central systolic pressure (CSP), augmentation index (AIx) and AIx at a heart rate of 75 beats/min (AIx-75) were significantly higher in the SGA group compared with the control group, but this was not the case for brachial systolic pressure, brachial diastolic pressure or brachial pulse pressure. Birth weight was significantly correlated with CSP (r=-0.26, p<0.01), AIx (r=-0.33, p<0.01) and AIx-75 (r=-0.27, p<0.01), but not with brachial systolic pressure, brachial diastolic pressure or brachial pulse pressure.

CONCLUSION

Increased arterial stiffness may be involved, in part, in the pathogenesis of SGA in normotensive women, suggesting an association between fetal growth and maternal endothelial function. Pulse wave analysis may be a clinically applicable method for assessment of maternal arterial stiffness, and may be more relevant to intrauterine fetal growth than conventional brachial blood pressure.

Association of beta-blocker use with increased aortic wave reflection

Studies have found less cardiovascular risk reduction in patients treated with beta-blockers (BBs) compared with other agents. We compared the severity of aortic atherosclerosis, arterial stiffness, and wave reflection in patients treated and not treated with BBs. Seventy-two patients, 37 treated with BBs and 35 not treated, referred for transesophageal echocardiography were studied. Augmentation index (AI), heart-rate-corrected AI (AI-75), aortic systolic (SBP) and diastolic blood pressure, pulse wave velocity (PWV), and aortic intima-media thickness (MAIMT) were measured. There were no differences in MAIMT (2.8 +/- 1.6 mm vs. 2.4 +/- 1.2 mm, P = .20) and PWV (8.9 +/- 2.0 m/s vs. 8.5 +/- 2.6 m/s, P = .46) between the BB and non-BB groups. The BB group had higher AI (28.7 +/-11.9% vs. 22.3 +/- 14.1%, P = .04), AI-75 (27.7 +/- 10.7% vs. 20.1+/- 11.0%, P = .005), aortic SBP (140 +/- 21 mm Hg vs. 125 +/- 21 mm Hg, P = .01), and aortic pulse pressure (62 +/- 20 mm Hg vs. 47 +/- 19 mm Hg, P = .01) than the non-BB group despite similar brachial blood pressure. BB use was associated with increased aortic wave reflection despite similar degree of aortic atherosclerosis.

RADIAL DIASTOLIC AUGMENTATION INDEX IS A USEFUL PREDICTOR OF ARTERIAL STIFFNESS

Diastolic augmentation index (DAI), calculated from radial artery pressure waveform, has been associated with the risk of cardiovascular disease. In the present study, we aimed to evaluate whether DAI could be used as a predictor of arterial stiffness and the effect of heart rate (HR) on it. Measurements of anthropometric parameters, blood pressure (BP), Augmentation index (AI) and DAI were taken in 242 healthy subjects (130 men and 112 women; age 16–78 years). DAI and AI were measured in a subgroup of 16 subjects (10 men and 6 women; age 19–69 years) in a two-month follow-up study, which aimed to investigate the effect of HR changes. Statistically, DAI was higher in women compared to men (44.8% ± 7.7% compared with 43.6% ± 6.9%, P < 0.05). DAI was decreased with age (men: r = -0.755, P < 0.05; women: r = -0.708, P < 0.05) and negatively correlated to AI (men: r = -0.704, P < 0.05; women: r = -0.756, P < 0.05). There was no significant change in DAI when HR ranged from 60 to 80 bpm. Multiple regression analysis demonstrated fewer determinants affect DAI compared with AI. These findings indicate that the simple radial DAI might be used as an index to assess vascular aging.

Central aortic blood pressure and augmentation index during normal pregnancy

The current study tested the hypothesis that pregnancy-related changes are more pronounced in central hemodynamics, and both central aortic systolic blood pressure (cSBP) and augmentation index (AIx) are independent from brachial systolic blood pressure (bSBP) in normal pregnant subjects. In 830 healthy pregnant women from 12 to 36 weeks gestation, we measured cSBP and AIx-75 (AIx at heart rate of 75 beats per minute) non-invasively by pulse waveforms of the radial artery using an automated applanation tonometric system. In 69 pregnant women, we recorded these data longitudinally. cSBP and AIx-75 significantly declined during pregnancy, reaching its nadir in mid-pregnancy and rising towards term. Pregnancy-related changes were more pronounced in AIx-75 compared with cSBP, but less evident in bSBP. AIx-75, but not cSBP, was independent from bSBP throughout pregnancy. cSBP and AIx-75, but not bSBP, were significantly increased in healthy pregnant women older than 35 years. This study established normal values for pulse wave analysis parameters throughout pregnancy, and indicated that pulse wave analysis might offer additional and independent information about maternal arterial compliance to conventional brachial blood pressure measurements. These data may be used as the basis for further investigation into the role of pulse wave analysis in the assessment, management and prediction of disorders, which might interfere with pregnancy-related cardiovascular adaptations.

Isolated systolic hypertension of young-to-middle-age individuals implies a relatively low risk of developing hypertension needing treatment when central blood pressure is low

OBJECTIVES

The clinical significance of isolated systolic hypertension (ISH) in the young is still controversial. Aim of the present study was to investigate whether prognosis of ISH in young-to-middle-age individuals differs according to central blood pressure (BP).

DESIGN

We studied 354 participants screened for stage 1 hypertension and 34 normotensive controls to determine which individuals developed hypertension needing drug therapy. Among the hypertensive patients, 67 had ISH and were divided according to whether their central SBP, measured with applanation tonometry, was above (ISH-high) or below (ISH-low) the median (120.5 mmHg). Large artery (C1) and small artery (C2) compliance were also measured.

RESULTS

Compared to normotensive individuals, ISH-high had decreased C1 (P = 0.02) and C2 (P = 0.01), and higher peripheral resistance (P = 0.01). In contrast, in ISH-low, all these variables were similar to those in normotensive individuals. During 9.5 years of follow-up, incident hypertension was more common among participants with systolic-diastolic hypertension (SDH) and ISH-high than the other two groups [odds ratio (OR) = 6.2, 95% confidence interval (CI) = 1.8-21.1, P = 0.003 for SDH; OR = 6.0, 95% CI = 1.5-24.0, P = 0.01 for ISH-high, versus normotensive individuals]. Among ISH-low, incidence of hypertension was only slightly higher than that in normotensive individuals (OR = 1.1, 95% CI 0.2-5.3, P = 0.90) and lower than that in ISH-high (P = 0.03). These associations remained significant when ambulatory BP was included in the models or when the 125 mmHg cut-off for central BP was used to identify ISH subgroups.

CONCLUSION

These data show that young-to-middle-age ISH individuals with low central BP have a lower risk of hypertension needing treatment than those with high central BP. These results are applicable mainly to male individuals.

Relationships of night/day heart rate ratio with carotid intima media thickness and markers of arterial stiffness

OBJECTIVES

To analyze the relationship between office and ambulatory heart rate, and its variability, and arterial stiffness in patients with primary arterial hypertension.

METHODS

A cross-sectional study was conducted in a primary care setting, with the inclusion of 356 hypertensive patients aged 30-80 years. Office and ambulatory blood pressure, heart rate, night/day heart rate ratio and the corresponding standard deviations, were determined. Arterial stiffness was assessed according to carotid intima media thickness, pulse wave velocity, the central and peripheral augmentation index, and the ambulatory arterial stiffness index.

RESULTS

Carotid intima media thickness, central and peripheral augmentation index, and ambulatory arterial stiffness index were negatively correlated to office and ambulatory heart rate and its standard deviation, and positively correlated to the night/day heart rate ratio. Pulse wave velocity showed a negative correlation to 24 h standard deviation heart rate and a positive correlation to nocturnal heart rate and the night/day heart rate ratio. For each 10 bpm increment in 24 h heart rate, the pulse wave velocity increased 0.42 m/s (95%CI: 0.23-0.60) and ambulatory arterial stiffness index decreased 0.01 (95%CI: 0.01-0.02); in the case of office heart rate, the peripheral augmentation index decreased 4.74 (95%CI: 3.15-6.33) and central augmentation index decreased 3.52 (95%CI: 2.43-4.30), while for 24 h standard deviation heart rate, carotid intima media thickness decreased 0.03 mm (95%CI: 0.01-0.06).

CONCLUSIONS

Office and ambulatory heart rate, and the corresponding standard deviations, are inversely associated to the arterial stiffness markers, with the exception of pulse wave velocity, where a direct correlation is observed. A greater increase in night/day ratio, i.e., a lesser decrease in nocturnal heart rate, is associated to increased arterial stiffness.

Effect of mirthful laughter on vascular function

In contrast to the well-established scientific evidence linking negative emotional states (e.g., depression, anxiety, or anger) to increased risk for cardiovascular disease, much less is known about the association between positive emotional states (e.g., laughter, happiness) and cardiovascular health. We determined the effects of mirthful laughter, elicited by watching comic movies, on endothelial function and central artery compliance. Seventeen apparently healthy adults (23 to 42 years of age) watched 30 minutes of a comedy or a documentary (control) on separate days (crossover design). Heart rate and blood pressure increased significantly while watching the comedy, whereas no such changes were seen while watching the documentary. Ischemia-induced brachial artery flow-mediated vasodilation (by B-mode ultrasound imaging) increased significantly after watching the comedy (17%) and decreased with watching the documentary (-15%). Carotid arterial compliance (by simultaneous application of ultrasound imaging and applanation tonometry) increased (10%) significantly immediately after watching the comedy and returned to baseline 24 hours after the watching, whereas it did not change significantly throughout the documentary condition. Comedy-induced changes in arterial compliance were significantly associated with baseline flow-mediated dilation (r = 0.63). These results suggest that mirthful laughter elicited by comic movies induces beneficial impact on vascular function.

Association of serum cystatin C with pulse wave velocity, but not pressure wave reflection, in subjects with normal renal function or mild chronic kidney disease

BACKGROUND

This prospective cross-sectional study was conducted to clarify whether serum cystatin C levels might be associated with not only arterial stiffness, but also the pressure wave reflection, in middle-aged Japanese subjects with normal renal function or mild chronic kidney disease (CKD) (stage 1 or 2 CKD) (i.e., creatinine-based estimate of the glomerular filtration rate (eGFRcr) > or =60 ml/min/1.73 m(2) plus a result of the urine dipstick test for proteinuria of <1+).

METHODS

In 2,904 Japanese subjects (45 +/- 9 years old), the brachial-ankle pulse wave velocity (baPWV), radial augmentation index adjusted to a heart rate of 75 beats/min (rAI75), and serum cystatin C levels were measured.

RESULTS

Multivariate linear regression analysis demonstrated that the serum cystatin C levels were significantly correlated with the baPWV (standardized coefficient = 0.04, P < 0.01) even after adjustments for confounding variables, but not with the AI75 (standardized coefficient = 0.01, P = 0.71). adjusted values of the baPWV, but not those of rAI75, were higher in subjects with serum cystatin C levels in the highest tertile than in those with serum cystatin levels in the intermediate or lowest tertile.

CONCLUSION

In middle-aged Japanese subjects with normal renal function or mild CKD (stage 1 or 2 CKD) (eGFRcr >60 ml/min/1.73 m(2) plus a result of the urine dipstick test for proteinuria of <1+), the serum cystatin C levels may reflect facet of cardiovascular risk associated with arterial stiffness, but not that associated with the pressure wave reflection.

Racial Differences in Relation Between Carotid and Radial Augmentation Index

BACKGROUND: Augmented central artery wave reflection is a cardiovascular disease risk factor. Augmentation index (AI) obtained from peripheral artery waveforms provides qualitatively similar information to AI from central artery waveforms. Little information is available, however, regarding the influence of racial difference in association between central and peripheral AI. METHODS: We studied 47 White adults (45+/-17 yr, 20 women) and 94 age-matched Asian adults (45+/-14 yr, 42 women). RESULTS: The White group was significantly taller than the Asian group, whereas there were no significant group differences in blood pressure and heart rate. Carotid and radial AI tended to be lower in White compared with Asian adults (P<0.10 for both). Such tendency disappeared when the difference in height was taken into account using ANCOVA (P=0.84 and P=0.77, respectively). Radial AI was strongly and positively correlated with carotid AI in White adults (r=0.75, P<0.0001) as well as in Asian adults (r=0.82, P<0.0001). The slope and intercept of linear regression line between radial and carotid AI of White adults were highly comparable with those of Asian adults. CONCLUSION: AI in the conveniently located peripheral vasculature may provide a surrogate measure of central AI irrespective of difference in race (e.g., Asian vs. White populations).

Arterial wave reflection in HIV-infected and HIV-uninfected Rwandan women

To assess differences in arterial wave reflection, a marker of atherosclerosis, in HIV-positive and HIV-negative Rwandan women, applanation tonometry was performed on 276 HIV(+) and 67 HIV(-) participants. Radial artery pressure waveforms were recorded and central aortic waveforms were derived by validated transfer function. Central augmentation index (C-AI), central pulse pressure (C-PP), and peripheral augmentation index (P-AI) were measured. HIV(+) participants were younger and had lower diastolic blood pressure (BP) and 41% of the HIV(+) women were taking antiretroviral therapy (ART). Mean C-AI and P-AI were significantly lower in HIV-infected than in uninfected participants (20.3 +/- 12.0 vs. 25.5 +/- 12.1, p = 0.002 and 74.6 +/- 18.8 vs. 83.7 +/- 20.0, p < 0.001). After age matching, C-AI, C-PP, and P-AI were similar among the groups. On multivariate analysis, age, heart rate, weight, and mean arterial pressure were independently associated with C-AI (R(2) = 0.33, p < 0.0001). Among HIV-infected women, current CD4 count did not correlate with C-AI (Rho = -0.01, p = 0.84), C-PP (Rho = 0.09, p = 0.16), or P-AI (Rho = -0.01, p = 0.83). In conclusion, HIV infection was not associated with increased arterial wave reflection in women with little exposure to antiretroviral therapy and without CV risk factors. Whether long-term ART increases measures of arterial stiffness remains unknown.

Role of the augmentation index in hypertension

Recent studies have revealed the clinical usefulness of central blood pressure (BP) as an index of risk for cardiovascular disease. The arterial pulse waveform is the sum of the forward pressure wave generated by left ventricular ejection and a backward propagating wave that is subsequently reflected from the peripheral site, and the time point at which these forward and backward propagating waves merge and the amplitude of the reflected (backward) wave affect the level of central BP. The augmentation index (AIx) has been proposed as a measure of the wave reflection, and its clinical usefulness has also been evaluated. In the process, the non-linear relationship between age and AIx, the prognostic value of AIx, and the various effects of antihypertensive drugs on AIx have been shown. However, the clinical usefulness of AIx has not been established, and several questions about its use remain. Future studies will be needed to address these questions, and may contribute to important changes in the management of cardiovascular disease. In this review, we present recent findings on the AIx and discuss the role of this parameter in clinical practice.

Relationship between augmentation index and flow-mediated vasodilation in the brachial artery

Recent studies have shown that the augmentation index (AI) is a predictor of cardiovascular complications. Endothelial dysfunction is the initial step in the pathogenesis of atherosclerosis, which in turn can lead to cardiovascular complications. Endothelial function assessed by flow-mediated dilation (FMD) can serve as an independent predictor of cardiovascular events. However, there is little information on the relationship between AI and FMD in the human vasculature, and we therefore investigated this relationship in the present study. A total of 100 subjects (71 males and 29 females; age range, 22-88 years; mean age, 59 +/- 17 years), including 83 patients with cardiovascular diseases (e.g., atherosclerosis, hypertension, coronary heart disease, stroke and peripheral arterial disease) and 17 healthy subjects were enrolled. High-resolution ultrasonography (automated vessel-diameter measurements; eTRACKING system), a linear array transducer (13 MHz) and an arm holding device were used to measure the arterial diameter response to reactive hyperemia and sublingual nitroglycerine (NTG, 75 micrograms) in all subjects. AI measured using an automated device was significantly correlated with FMD (r = -0.38, p < 0.0001). There was no significant correlation between AI and vascular response to NTG. Multiple regression analysis showed that FMD was a significant independent predictor of AI (p < 0.05). These findings suggest that increase in arterial stiffness may be associated with grade of endothelial dysfunction and that AI may be an index of not only arterial stiffness but also endothelial function.

Attenuated radial augmentation index is associated with successful long-term antihypertensive treatment

Pulse wave analysis was performed in apparently normal volunteers (n=164) and in essentially hypertensive patients without cardiovascular complications (n=171) using a newly developed non-invasive pulse wave measurement device (HEM-9010AI). Our results suggest that early wave reflections measured by radial augmentation index (AIr) are enhanced in volunteers with systolic blood pressure (SBP) >or= 160 mm Hg compared with the volunteers with their SBP<160 mmHg (98+/-18 vs 88+/-12, P<0.05). Furthermore, AIr is lower in hypertensive patients with long-term antihypertensive treatment than in those with short-term treatment (84+/-10 vs 89+/-13, P<0.01).