Estimation of central aortic pressure waveform by mathematical transformation of radial tonometry pressure. Validation of generalized transfer function

Effects of aerobic, resistance and concurrent exercise on pulse wave reflection and autonomic modulation in men with elevated blood pressure

The acute effects of exercise modes on pulse wave reflection (PWR) and their relationship with autonomic control remain undefined, particularly in individuals with elevated blood pressure (BP). We compared PWR and autonomic modulation after acute aerobic (AE), resistance (RE), and concurrent exercise (CE) in 15 men with stage-1 hypertension (mean ± SE: 34.7 ± 2.5 years, 28.4 ± 0.6 kg/m², 133 ± 1/82 ± 2 mmHg). Participants underwent AE, RE, and CE on different days in counterbalanced order. Applanation tonometry and heart rate variability assessments were performed before and 30-min postexercise. Aortic pressure decreased after AE (− 2.4 ± 0.7 mmHg; P = 0.01), RE (− 2.2 ± 0.6 mmHg; P = 0.03), and CE (− 3.1 ± 0.5 mmHg; P = 0.003). Augmentation index remained stable after RE, but lowered after AE (− 5.1 ± 1.7%; P = 0.03) and CE (− 7.6 ± 2.4% P = 0.002). Systolic BP reduction occurred after CE (− 5.3 ± 1.9 mmHg). RR-intervals and parasympathetic modulation lowered after all conditions (~ 30–40%; P < 0.05), while the sympathovagal balance increased after RE (1.2 ± 0.3–1.3 ± 0.3 n.u., P < 0.05). Changes in PWR correlated inversely with sympathetic and directly with vagal modulation in CE. In conclusion, AE, RE, and CE lowered central aortic pressure, but only AE and CE reduced PWR. Overall, those reductions related to decreased parasympathetic and increased sympathetic outflows. Autonomic fluctuations seemed to represent more a consequence than a cause of reduced PWR.

Role of arterial stiffness in the association between hand grip strength and cardiovascular events: the Korean Genome and Epidemiology Study

BACKGROUND

Hand grip strength (HGS) has been associated with cardiovascular events. However, the exact mechanism responsible for the inverse association between HGS and cardiovascular events has not been established. The aim of this study was to assess whether arterial stiffness mediates this association.

METHODS

We studied 1508 participants (age; 60 ± 5, men; 47.5%) from the Ansan cohort of the Korean Genome Epidemiology Study. Participants were assessed for various parameters of arterial stiffness as well as HGS. The augmentation index (AIx) and brachial-ankle pulse wave velocity (baPWV) were evaluated by using an applanation tonometer and automated waveform analyzer, respectively. Carotid intima medial thickness (IMT) was measured by B-mode ultrasonogram with a 7.5-MHz linear array transducer. HGS was evaluated using a Jamar dynamometer.

RESULTS

With increased grip strength, AIx decreased (r = 0.437, P < 0.001). baPWV (r = 0.044, P = 0.107) and carotid IMT (r = 0.005, P = 0.856) had no significant correlation with grip strength. This trend was consistently observed regardless of hypertension, but was more pronounced in participants with hypertension.

CONCLUSION

HGS was significantly correlated with AIx, but not with baPWV and carotid IMT. Our findings suggest that central arterial stiffness could mediate the association between HGS and cardiovascular events.

Maternal hemodynamics, arterial stiffness and elastic aortic properties in twin pregnancy

OBJECTIVE

There is scant information about maternal cardiovascular hemodynamic change during twin pregnancies. Aim of the study is to investigate longitudinal changes in maternal arterial stiffness, elastic aortic properties and ventricular-arterial coupling (VAC) in uncomplicated twin pregnancies compared to singleton ones.

APPROACH

In this prospective longitudinal study, we performed applanation tonometry and transthoracic echocardiography in the first (T1; 10-15 weeks' gestation (w)), second (T2; 19-26 w) and third trimesters (T3; 30-38 w) in women with uncomplicated twin pregnancies, both monochorionic and dichorionic. Heart-rate-corrected augmentation index (AIx@75) was studied as indicator of arterial stiffness. Aortic diameters and elastic properties were calculated. VAC was defined as the ratio between aortic elastance (Ea) and left ventricular end-systolic elastance (Ees). Finally, stroke volume (SV), cardiac output (CO) and total vascular resistance (TVR) were evaluated. The findings were compared to those of women with uncomplicated singleton pregnancies.

MAIN RESULTS

Thirty women with twin gestations (11 monochorionic) and 30 singleton controls were obtained for analysis. Blood pressure and TVR significantly decreased from T1 to T2 and then rose in T3, with higher values in twins than in singletons. AIx@75 showed the same trend in both groups with lower values at T2 in twins. SV and CO linearly increased throughout gestation with no significant intergroup difference. Aortic diameters and elastic properties remained stable throughout gestation, with no significant intergroup differences. Both Ea and Ees were greater (i.e. worse) in twins than in singletons at T1 and T3, showing a significant linear trend towards reduction in the two groups, meaning lower vascular and ventricular loads. Using longitudinal analysis blood pressure, TVR, Ea and Ees depended from both multiple gestation and gestational age.

SIGNIFICANCE

In twins, maternal hemodynamics does not seem to undergo more significant changes than in singletons being characterized by higher blood pressures and TVR with no differences in CO, SV, aortic dimensions and elastic properties. Despite VAC is maintained within its normal range, total vascular load (i.e., Ea) resulted higher in twin than singleton pregnancies throughout gestation. It is conceivable that these findings may represent one of the underlying cause for the increased risk of adverse obstetric outcomes described in multiple gestations.

Parathyroid hormone may play a role in the pathophysiology of primary hypertension

Parathyroid hormone has been related with the risk of hypertension, but the matter remains controversial. We examined the association of parathyroid hormone with central blood pressure and its determinants in 622 normotensive or never-treated hypertensive subjects aged 19-72 years without diabetes, cardiovascular or renal disease, or cardiovascular medications. The methods were whole-body impedance cardiography and analyses of pulse wave and heart rate variability. Cardiovascular function was examined in sex-specific tertiles of plasma parathyroid hormone (mean concentrations 3.0, 4.3 and 6.5 pmol/L, respectively) during head-up tilt. Explanatory factors for haemodynamics were further investigated using linear regression analyses. Mean age was 45.0 (s.d. 11.7) years, BMI 26.8 (4.4) kg/m2, seated office blood pressure 141/90 (21/12) mmHg, and 309 subjects (49.7%) were male. Only five participants had elevated plasma parathyroid hormone and calcium concentrations. Highest tertile of parathyroid hormone presented with higher supine and upright aortic diastolic blood pressure (P < 0.01) and augmentation index (P < 0.01), and higher upright systemic vascular resistance (P < 0.05) than the lowest tertile. The tertiles did not present with differences in pulse wave velocity, cardiac output, or measures of heart rate variability. In linear regression analyses, parathyroid hormone was an independent explanatory factor for aortic systolic (P = 0.005) and diastolic (P = 0.002) blood pressure, augmentation index (P = 0.002), and systemic vascular resistance (P = 0.031). To conclude, parathyroid hormone was directly related to central blood pressure, wave reflection, and systemic vascular resistance in subjects without cardiovascular comorbidities and medications. Thus, parathyroid hormone may play a role in the pathophysiology of primary hypertension.

Primary aldosteronism: Higher volume load, cardiac output and arterial stiffness than in essential hypertension

BACKGROUND

The diagnostics of primary aldosteronism (PA) are usually carried out in patients taking antihypertensive medications. We compared haemodynamics between medicated PA, medicated essential hypertension (EH), never-medicated EH and normotensive controls (n = 130 in all groups).

METHODS

The hypertensive groups were matched for age (53 years), sex (84 male/46 female) and body mass index (BMI) (30 kg m^-2 ); normotensive controls had similar sex distribution (age 48 years, BMI 27 kg m^-2 ). Haemodynamics were recorded using whole-body impedance cardiography and radial pulse wave analysis, and the results were adjusted as appropriate. Radial blood pressure recordings were calibrated by brachial blood pressure measurements from the contralateral arm.

RESULTS

Radial and aortic systolic and diastolic blood pressure was similar in PA and never-medicated EH, and higher than in medicated EH and normotensive controls (P ≤ 0.001 for all comparisons). Extracellular water balance was ~ 4% higher in PA than in all other groups (P < 0.05 for all), whilst cardiac output was ~ 8% higher in PA than in medicated EH (P = 0.012). Systemic vascular resistance and augmentation index were similarly increased in PA and both EH groups when compared with controls. Pulse wave velocity was higher in PA and never-medicated EH than in medicated EH and normotensive controls (P ≤ 0.033 for all comparisons).

CONCLUSIONS

Medicated PA patients presented with corresponding systemic vascular resistance and wave reflection, but higher extracellular water volume, cardiac output and arterial stiffness than medicated EH patients. Whether the systematic evaluation of these features would benefit the clinical diagnostics of PA remains to be studied in future.

Influence of noninvasive central blood pressure devices for afterload monitoring with aortic velocity-pressure Loop in anesthetized patients

BACKGROUND

Global afterload angle (GALA) is a parameter derived from velocity-pressure loop (VP Loop), for continuous assessment of cardiac afterload in the operating room. It has been validated with invasive measure of central pressure. The aim of this study was to evaluate the feasibility of noninvasive VP Loop obtained with central pressure measured with two different noninvasive tonometers.

METHODS

A prospective, observational, monocentric study was conducted in 51 patients under general anesthesia. Invasive central pressure (cPINV) was measured with a fulfilled intravascular catheter, and noninvasive central pressure signals were obtained with two applanation tonometry devices: radial artery tonometry (cPSHYG: Sphygmocor tonometer) and carotid tonometry (cPCOMP: Complior tonometer). Three VP Loops were built: VP LoopINV, VP LoopSPHYG and VP LoopCOMP. Patients were separated according to cardiovascular risk factors.

RESULTS

In the 51 patients under general anesthesia, cPSHYG was adequately obtained in 48 patients (89%) but, compared to cPINV, SBP was underestimated (-4 ± 6 mmHg, P < 0.0001), augmentation index (AIXSPHYG) and a GALASPHYG were overestimated (+13 ± 19%, P = 0.0077 and +4 ± 8°, P = 0.0024, respectively) with large limit of agreement (LOA) (-21 to 47% and -13 to 21° for AIXSPHYG and GALASPHYG, respectively). With the Complior, the failure rate of measurement for cPCOMP was 41%. SBP was similar (3 ± 17 mmHg, P = 0.32), AIXCOMP was underestimated (-11 ± 19%, P = 0.0046) and GALACOMP was similar but with large LOA (-50 to 26% and -20 to 18° for AIXCOMP and GALACOMP, respectively).

CONCLUSION

In anesthetized patient, the reliability of noninvasive central pressure monitoring by tonometry seems too limited to monitor cardiac afterload with VP Loop.

Factors independently associated with cardiorespiratory fitness in patients with non-alcoholic fatty liver disease

Low cardiorespiratory fitness (CRF) is associated with non-alcoholic fatty liver disease (NAFLD) and low CRF is an important risk factor for cardiovascular disease. The factors that influence CRF in NAFLD are poorly understood and it has been suggested that reduced hepatic mitochondrial function (HMF) may be linked to low CRF. Therefore, our aim was to determine the factors associated with CRF in NAFLD.

METHODS

Ninety-seven patients with NAFLD were studied. CRF was assessed by treadmill testing and expressed as maximal O₂ consumption (VO₂ peak) per lean body mass. HMF was assessed by the ¹³ C-ketoisocaproate breath test. Multivariable linear regression modelling was undertaken to test the independence of associations with CRF.

RESULTS

Mean (SD) age was 51 (13) years and 61% were men. With CRF as the outcome, age (B coefficient -0.3, 95%CI -0.4, -0.2, P < .0001), total body fat mass (B coefficient -0.2, 95%CI -0.3, -0.05, P = .01), type 2 diabetes mellitus (T2DM) (B coefficient -3.6, 95%CI -1.1, -6.1, P = .005), smoking status (B coefficient -5.7, 95%CI -1.9, -9.5, P = .004), serum γ-glutamyl transferase (GGT) (B coefficient -0.04, 95%CI -0.05, -0.02, P < .0001), HMF (B coefficient -0.5, 95%CI -0.8, -0.1, P = .01) and diastolic function (B coefficient 0.1, 95%CI 0.05, 0.13, P < .0001) were independently associated with CRF. This model explained 60% of the total variance in CRF (R²  = 0.6, P < .0001); and this model with GGT alone explained 24% of the variance in CRF.

CONCLUSIONS

In patients with NAFLD, HMF is independently associated with CRF and a model with GGT alone explained most of the variance in CRF.

Aldosterone-to-renin ratio is related to arterial stiffness when the screening criteria of primary aldosteronism are not met

Aldosterone-to-renin ratio (ARR) is a screening tool for primary aldosteronism (PA), but the significance of ARR when the PA criteria are not met remains largely unknown. In this cross-sectional study we investigated the association of ARR with haemodynamic variables in 545 normotensive and never-medicated hypertensive subjects (267 men, 278 women, age range 19-72 years) without suspicion of PA. Supine haemodynamic data was recorded using whole-body impedance cardiography and radial tonometric pulse wave analysis. In sex-adjusted quartiles of ARR, determined as serum aldosterone to plasma renin activity ratio, the mean values were 282, 504, 744 and 1467 pmol/µg of angiotensin I/h, respectively. The only difference in haemodynamic variables between the ARR quartiles was higher pulse wave velocity (PWV) in the highest quartile versus other quartiles (p = 0.004), while no differences in blood pressure (BP), heart rate, wave reflections, cardiac output or systemic vascular resistance were observed between the quartiles. In linear regression analysis with stepwise elimination, ARR was an independent explanatory factor for PWV (β = 0.146, p < 0.001, R2 of the model 0.634). In conclusion, ARR was directly and independently associated with large arterial stiffness in individuals without clinical suspicion of PA. Therefore, ARR could serve as a clinical marker of cardiovascular risk.Trial registration: ClinicalTrails.gov: NCT01742702.

Imaging Protocol, Feasibility, and Reproducibility of Cardiovascular Phenotyping in a Large Tri-Ethnic Population-Based Study of Older People: The Southall and Brent Revisited (SABRE) Study

Background: People of South Asian and African Caribbean ethnicities living in UK have a high risk of cardiometabolic disease. Limited data exist regarding detailed cardiometabolic phenotyping in this population. Methods enabling this are widely available, but the practical aspects of undertaking such studies in large and diverse samples are seldom reported. Methods: The Southall and Brent Revisited (SABRE) study is the UK's largest tri-ethnic longitudinal cohort. Over 1,400 surviving participants (58-85 years) attended the 2nd study visit (2008-2011); during which, comprehensive cardiovascular phenotyping, including 3D-echocardiography [3D-speckle-tracking (3D-STE)], computed tomography, coronary artery calcium scoring, pulse wave velocity, central blood pressure, carotid artery ultrasound, and retinal imaging, were performed. We describe the methods used with the aim of providing a guide to their feasibility and reproducibility in a large tri-ethnic population-based study of older people. Results: Conventional echocardiography and all vascular measurements showed high feasibility (>90% analyzable of clinic attendees), but 3D-echocardiography (3DE) and 3D-STE were less feasible (76% 3DE acquisition feasibility and 38% 3D-STE feasibility of clinic attendees). 3D-STE feasibility differed by ethnicity, being lowest in South Asian participants and highest in African Caribbean participants (p < 0.0001). Similar trends were observed in men (P < 0.0001) and women (P = 0.005); however, in South Asians, there were more women with unreadable 3D-images compared to men (67 vs. 58%). Intra- and inter-observer variabilities were excellent for most of conventional and advanced echocardiographic measures. The test-retest reproducibility was good-excellent and fair-good for conventional and advanced echocardiographic measures, respectively, but lower than when re-reading the same images. All vascular measures demonstrated excellent or fair-good reproducibility. Conclusions: We describe the feasibility and reproducibility of detailed cardiovascular phenotyping in an ethnically diverse population. The data collected will lead to a better understanding of why people of South Asian and African Caribbean ancestry are at elevated risk of cardiometabolic diseases.

Early vascular ageing biomarkers in osteoporotic outpatients: a pilot study

Osteoporosis and atherosclerosis are significant public health problems that often coexist, especially in the elderly. Although some studies have reported an age-dependent relationship, others have suggested a causal relationship between osteoporosis and atherosclerosis. The aim of our study was to evaluate the cardiovascular risk in a population of patients with osteoporosis by measuring carotid intima-media thickness (cIMT) and carotid-femoral pulse wave velocity (cf-PWV). A total of 58 patients with osteoporosis and an equal number of healthy control subjects were enrolled. All subjects underwent (1) a bone densitometry examination using dual X-ray absorptiometry, (2) a vascular evaluation for the measurements of cIMT and cf-PWV and (3) a blood sample for the evaluation of lipids and phosphocalcic metabolism. Patients with osteoporosis had a significant increase in cIMT and cf-PWV. There was also a significant inverse correlation between the femoral neck BMD and cf-PWV values. In conclusion, osteoporotic outpatients have earlier vascular ageing, with an increase of arterial stiffness. These data support a possible association between osteoporosis and atherosclerosis independent of age.

An instrument for measuring blood pressure and assessing cardiovascular health from the fingertip

Despite blood pressure being one the leading modifiable risk factors for cardiovascular disease and death, it is severely under-monitored. For this challenge we propose a finger artery non-invasive tono-oscillometric monitor (FANTOM) which is an automated low-cost instrument for measuring blood pressure and hemodynamic parameters from the fingertip. The sensing technology is highly scalable and could be integrated to a pulse oximeter probe for increased patient comfort. A tonometric cuff-less mechatronic system is used to apply pressure on the fingertip for (i) measuring oscillometric blood pressure, (ii) recording arterial waveform and for (iii) constructing central blood pressure (CBP) waveform. Clinical study on volunteers (n = 33) was performed against a commercially available arm cuff device yielding systolic and diastolic readings ((mean±SD) mmHg) of (-0.9 ± 7.3) mmHg and (-3.3 ± 6.6) mmHg respectively. The results comply with the Association for the Advancement of Medical Instrumentation (AAMI) standard for non-invasive blood pressure monitors. The arterial pulse recording morphology was compared against a volume clamp device (CNSystems CNAP 500) (n = 3) resulting in similar performance. Comparison of CBP against a pulse wave analysis (PWA) device (Atcor Medical Sphygmocor XCEL) (n = 5) revealed central aortic systolic pulse (CASP) and central augmentation index (cAIx) estimates with precision and accuracy of (2.0 ± 3.7) mmHg and (1.4 ± 6.2)% respectively. In conclusion, the results indicate that the proposed technology could be useful in the development of new portable or wearable blood pressure monitors. The sensing technology is highly scalable and could be integrated to a pulse oximeter probe for increased patient comfort.

Experimental investigation into the effect of compliance of a mock aorta on cardiac performance

Demand for heart transplants far exceeds supply of donated organs. This is attributed to the high percentage of donor hearts that are discarded and to the narrow six-hour time window currently available for transplantation. Ex-vivo heart perfusion (EVHP) provides the opportunity for resuscitation of damaged organs and extended transplantation time window by enabling functional assessment of the hearts in a near-physiologic state. Present work investigates the fluid mechanics of the ex-vivo flow loop and corresponding impact on cardiac performance. A mechanical flow loop is developed that is analogous to the region of the EVHP system that mimics in-vivo systemic circulation, including the body’s largest and most compliant artery, the aorta. This investigation is focused on determining the effect of mock aortic tubing compliance on pump performance. A custom-made silicone mock aorta was developed to simulate a range of in-vivo conditions and a physiological flow was generated using a commercial ventricular assist device (VAD). Monitored parameters, including pressure, tube distension and downstream velocity, acquired using time-resolved particle imaging velocimetry (PIV), were applied to an unsteady Bernoulli analysis of the flow in a novel way to evaluate pump performance as a proxy for cardiac workload. When compared to the rigid case, the compliant mock aorta case demonstrated healthier physiologic pressure waveforms, steadier downstream flow and reduced energetic demands on the pump. These results provide experimental verification of Windkessel theory and support the need for a compliant mock aorta in the EVHP system.

Sodium Intake Is Associated With Renal Resistive Index in an Adult Population-Based Study

Renal resistive index (RRI) has been associated with adverse renal and cardiovascular outcomes. Although traditionally considered a marker of intrinsic renal damage, RRI could also reflect systemic vascular dysfunction. As sodium intake was linked to alterations in vascular properties, we wished to characterize the association of salt consumption with RRI in the general adult population. Participants were recruited in a population-based study in Switzerland. RRI was measured by ultrasound in 3 segmental arteries. Sodium intake (UNa; mmol/24 h) was estimated on 24-hour urine samples. Carotido-femoral pulse wave velocity was obtained by applanation tonometry. Mixed multivariate regression models were used with RRI or pulse wave velocity as independent variables and UNa as dependent variable, adjusting for possible confounders. We included 1002 patients in the analyses with 528 (52.7%) women and mean age of 47.2±17.4. Mean values of UNa and RRI were 141.8±61.1 mmol/24 h and 63.8±5.5%, respectively. In multivariate analysis, UNa was positively associated with RRI (P=0.002) but not with pulse wave velocity (P=0.344). Plasma renin activity and aldosterone did not modify the relationship between UNa and RRI (P=0.087 for interaction). UNa/urinary potassium ratio was positively associated with pulse wave velocity ≥12 m/s (P=0.033). Our results suggest that dietary salt consumption has a direct impact on renal hemodynamic in the adult general population. Alterations in vascular properties likely explain those findings, but inadequate renal vaso-motor response is also possible. Sodium intake could thus potentially be linked to underlying structural systemic damages affecting this population.

A novel method to assess valvulo-arterial load in patients with aortic valve stenosis

INTRODUCTION

Ventricular function in elderly patients with aortic stenosis is impeded both by restricted aortic flow and arterial stiffening. A number of patients continue to have exertional intolerance after relief of aortic valvular obstruction due to unrecognized ventriculo-arterial coupling mismatch.

HYPOTHESIS

Quantification of valvulo-arterial load (VAL), using a simultaneous applanation tonometry/cardiac magnetic resonance (CMR) technique, can accurately assess the relative contributions of aortic stiffness and valve gradient in older patients with aortic stenosis.

METHODS

Elderly patients with aortic stenosis underwent a simultaneous applanation tonometry/CMR protocol. CMR provided left ventricular volume and aortic flow simultaneously with radial applanation tonometry pressure acquisition. Central aortic pressure was derived by transformation of the radial applanation tonometry waveform. VAL was determined as the relationship of derived aortic pressure to CMR aortic flow in frequency domain (central illustration).

RESULTS

Twenty patients (age 80 ± 9 years; 12 males; blood pressure 140/75 ± 20 mmHg) with aortic stenosis on transthoracic echocardiogram (16 severe; mean gradient 45 ± 16 mmHg; aortic valve area 0.8 ± 0.2 cm2) were enrolled. Derived aortic pressure and flow waveforms correlated well with invasive data. Increased VAL was significantly associated with advanced age (P = 0.04) and raised SBP (P < 0.01), irrespective of aortic stenosis severity.

CONCLUSION

Difficulties in the measurement and accuracy of ventriculo-arterial coupling means that it is not routinely measured in patients with aortic stenosis. We describe a new noninvasive index that provides an accurate assessment of valvular and arterial load on the left ventricle. VAL may help detect those at risk of ventriculo-arterial coupling mismatch and assist in selection of those most likely to benefit from an invasive procedure.

Dynamic and isometric handgrip exercise increases wave reflection in healthy young adults

Early return and increased magnitude of wave reflection augments pulsatile load, wastes left ventricular effort, and is associated with cardiovascular events. Acute handgrip (HG) exercise increases surrogate measures of wave reflection such as augmentation index. However, augmentation index does not allow distinguishing between timing versus magnitude of wave reflection and is affected by factors other than wave reflection per se. Wave separation analysis decomposes central pressure into relative contributions of forward (Pf) and backward (Pb) pressure wave amplitudes to calculate reflection magnitude (RM = Pb/Pf) and determine the timing of apparent wave reflection return. We tested the hypothesis that acute dynamic and isometric HG exercise increases RM and decreases reflected wave transit time (RWTT). Applanation tonometry was used to record radial artery pressure waveforms in 30 adults (25 ± 4 yr) at baseline and during dynamic and isometric HG exercise. Wave separation analysis was performed offline using a physiological flow wave to derive Pf, Pb, RM, and RWTT. We found that RM increased during dynamic and isometric HG exercise compared with baseline (P = 0.04 and P < 0.01, respectively; baseline 40 ± 5, dynamic 43 ± 6, isometric 43 ± 7%). Meanwhile, RWTT decreased during dynamic and isometric HG exercise compared with baseline (P = 0.03 and P < 0.001, respectively; baseline 164 ± 23, dynamic 155 ± 23, isometric 148 ± 20 ms). Moreover, the changes in RM and RWTT were not different between dynamic and isometric HG exercise. The present data suggest that wave reflection timing (RWTT) and magnitude (RM) are important factors that contribute to increased central blood pressure during HG exercise.NEW & NOTEWORTHY This study demonstrated that wave reflection magnitude is increased while reflected wave transit time is decreased during handgrip exercise in healthy young adults. The larger backward pressure waves and earlier return of these pressure waves were not different between dynamic and isometric handgrip exercise. These acute changes in wave reflection during handgrip exercise transiently augment pulsatile load.

Anxiety, depression, chronic inflammation and aortic stiffness in Crohn's disease: the brain--gut--vascular axis

BACKGROUND

Patients with Crohn's disease have an increased aortic stiffness, a known cardiovascular risk factor. Anxiety, a key factor of the brain--gut axis in patients with Crohn's disease, is implicated in the pathogenesis and progression of the disease, and is linked with aortic stiffening in other clinical settings.

OBJECTIVES

Considering that depression is frequently linked to anxiety in Crohn's disease, we performed a mediation analysis to reveal the potential link between anxiety, depression and aortic stiffness in these patients.

METHODS

Multicentre observational cross-sectional study of 86 consecutive patients with Crohn's disease and 86 matched control individuals. The connections between anxiety, depression, disease duration, aortic pulse wave velocity (aPWV), brachial and central SBP were tested using partial least squares structural equations modelling.

RESULTS

In patients with Crohn's disease, anxiety (path coefficient: 0.220, P = 0.01) and disease duration (path coefficient: 0.270, P = 0.02) were associated with aPWV that in turn was associated with brachial SBP (path coefficient: 0.184, P = 0.03). These associations were even stronger in patients with active disease. The connection between anxiety and aPWV was in part mediated by central SBP (indirect effect: 0.090, P = 0.01; indirect-to-total effect ratio: 41%) as well as, in a pilot substudy, by sympathetic hyperactivity. Anxiety and depression were highly correlated in patients with Crohn's disease. Consequently, results were confirmed when anxiety was substituted by depression.

CONCLUSION

The connections of anxiety, depression and chronic inflammation with aPWV and SBP could suggest the first evidence of a brain--gut--vascular axis and new potential targets for therapy in patients with Crohn's disease.

Treatment to reduce vascular calcification in hemodialysis patients using vitamin K (Trevasc-HDK): A study protocol for a randomized controlled trial

INTRODUCTION

End stage renal failure patients on hemodialysis have significant vascular calcification This is postulated to be related to sub-clinical vitamin K deficiency, which is prevalent in hemodialysis patients. Vitamin K deficiency result in the failure of the matrix GLA protein (MGP) to undergo carboxylation. MGP is a natural local inhibitor of vascular calcification and the lack of functional carboxylated MGP may contribute to increase vascular calcification. Vitamin K supplement should therefore correct this anomaly and decrease the rate or severity of vascular calcification in this population of patients on long-term maintenance hemodialysis. Our study seeks to evaluate the prevalence and the progression of vascular calcification in a cohort of maintenance hemodialysis patients. It will also evaluate the efficacy of vitamin K supplementation in reducing the progression of vascular calcification in this group of patients.

METHODS

This will be a single-center randomized, prospective and open-label interventional clinical trial of end stage renal failure patients on hemodialysis. We aim to recruit 200 patients. Eligible patients will be randomized to either the standard care arm or active treatment arm. Active treatment arm patients will receive standard care plus supplementation with oral vitamin K2 isoform 360 mcg 3 times weekly for a total duration of 18 months. Primary outcome measured will be absolute difference in coronary artery calcification score at 18-month between control and intervention arms. Secondary outcomes will be to compare absolute difference in aortic valve calcification, percentage of patients with regression of coronary artery calcification of at least 10%, absolute difference in aortic and systemic arterial stiffness, mortality from any cause and major adverse cardiovascular over the same period.

DISCUSSION

Evidence of successful regression or retardation of vascular calcification will support the conduct of larger and longer-term trials aimed at reducing cardiovascular disease mortality and major adverse cardiovascular events in this high-risk population using a safe and inexpensive strategy TRIAL REGISTRATION:: ClinicalTrials.gov NCT02870829. Registered on 17 August 2016 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT02870829National University Hospital's Institutional Review Board (2015/01000).

Improvement in Angiotensin 1-7 precedes and correlates with improvement in Arterial stiffness and endothelial function following Renin-Angiotensin system inhibition in type 2 diabetes with newly diagnosed hypertension

BACKGROUND AND AIM

Studies in cell cultures and animal models have revealed the possible pathophysiological factors associated with vascular endothelial dysfunction. However, the same in human subjects has not been clearly established. The current study uses a novel approach to identify the factors associated with endothelial function and arterial function by altering these vascular parameters using Angiotensin-Converting-Enzyme (ACE) inhibition.

METHODS

Diabetic patients with newly diagnosed hypertension (n = 60) were recruited for the study. Flow-mediated-dilation (FMD), carotid-femoral (cf), carotid-radial (cr) Pulse-wave-velocity (PWV), Augmentation-Index, Carotid-Intima-Media-Thickness (CIMT), serum levels of Renin, Angiotensin II (AngII), Angiotensin-Converting-Enzyme2 (ACE2), Angiotensin1-7 (Ang1-7), E-selectin, Vascular-Cell-Adhesion-Molecule-1 (VCAM-1), Highly-sensitive-C-Reactive-Protein (hsCRP) and Interleukin-10 were measured at baseline (V1), after 1 week (V2) and 3 months (V3) of ACE inhibition in patients of diabetes with newly diagnosed hypertension. The amplitude of change after 1 week (V₂-V₁) and 3 months (V₃-V₁) for the clinical and various parameters were correlated with the change in endothelial function and arterial stiffness.

RESULTS

Carotid radial-PWV_V2-V1 (p = 0.001) and Ang1-7_V2-V1 (p = 0.01) emerged as independent predictors of FMD_V2-V1. Renin_V2-V1 and VCAM-1_V2-V1 independently predicted E-selectin_V2-V1 [(p = 0.01) and (p = 0.001), respectively]. ACE 2_V2-V1 was the only independent predictor of cf-PWV_V2-V1. The same parameters remained as independent predictors of the respective vascular factors after 3 months of ACE inhibition.

CONCLUSION

The study highlights the role of AngII/Ang1-7 balance in alteration of endothelial function and central arterial stiffness in humans in addition to identifying the interrelationship between the renin-angiotensin-aldosterone-system components and clinically ascertainable parameters.

Observer-Based Deconvolution of Deterministic Input in Coprime Multichannel Systems With Its Application to Noninvasive Central Blood Pressure Monitoring

Estimating central aortic blood pressure (BP) is important for cardiovascular (CV) health and risk prediction purposes. CV system is a multichannel dynamical system that yields multiple BPs at various body sites in response to central aortic BP. This paper concerns the development and analysis of an observer-based approach to deconvolution of unknown input in a class of coprime multichannel systems applicable to noninvasive estimation of central aortic BP. A multichannel system yields multiple outputs in response to a common input. Hence, the relationship between any pair of two outputs constitutes a hypothetical input-output system with unknown input embedded as a state. The central idea underlying our approach is to derive the unknown input by designing an observer for the hypothetical input-output system. In this paper, we developed an unknown input observer (UIO) for input deconvolution in coprime multichannel systems. We provided a universal design algorithm as well as meaningful physical insights and inherent performance limitations associated with the algorithm. The validity and potential of our approach were illustrated using a case study of estimating central aortic BP waveform from two noninvasively acquired peripheral arterial pulse waveforms. The UIO could reduce the root-mean-squared error (RMSE) associated with the central aortic BP by up to 27.5% and 28.8% against conventional inverse filtering (IF) and peripheral arterial pulse scaling techniques.

Evaluation of systo-diastolic cardiac function and arterial stiffness in subjects with new diagnosis of coeliac disease without cardiovascular risk factors

In literature, there are conflicting opinions on the development of cardiovascular disease risk in patients with coeliac disease (CD). The aim of the research was to identify in young subjects without cardiovascular risk factor and newly diagnosed CD, alterations in different instrumental parameters that are associated with an augmented cardiovascular risk. Twenty-one consecutive young adults with a new diagnosis of CD and without cardiovascular risk factors were prospectively enrolled and underwent transthoracic echocardiography to analyse ascending aorta elastic properties [including tissue Doppler imaging strain (TDI-ε)] and left ventricular 2D strains (global longitudinal, radial and circumferential), and applanation tonometry by SphygmoCor. Cases were compared with 21 age- and sex-matched healthy controls. Mean age of the cases was 38 ± 9 years and 15 of them (71%) were female. Brachial and central blood pressure was higher in the CD group. Elastic properties of the ascending aorta were all impaired in the CD group: TDI-ε was altered in 57% of cases (0% of controls, p < 0.001). Concentric remodelling and grade I diastolic dysfunction were present in 38% and 24% of cases, respectively (0% of controls, p < 0.001). Global longitudinal strain was normal in all subjects, while radial and circumferential strain were altered in 67% and 35%, respectively (0% of controls, p < 0.001). In young subjects without cardiovascular risk factor, a newly diagnosed CD is associated with altered aortic elastic properties, left ventricular concentric remodelling and diastolic dysfunction and altered radial and circumferential strain.

Measurement, Analysis and Interpretation of Pressure/Flow Waves in Blood Vessels

The optimal performance of the cardiovascular system, as well as the break-down of this performance with disease, both involve complex biomechanical interactions between the heart, conduit vascular networks and microvascular beds. ‘Wave analysis’ refers to a group of techniques that provide valuable insight into these interactions by scrutinizing the shape of blood pressure and flow/velocity waveforms. The aim of this review paper is to provide a comprehensive introduction to wave analysis, with a focus on key concepts and practical application rather than mathematical derivations. We begin with an overview of invasive and non-invasive measurement techniques that can be used to obtain the signals required for wave analysis. We then review the most widely used wave analysis techniques—pulse wave analysis, wave separation and wave intensity analysis—and associated methods for estimating local wave speed or characteristic impedance that are required for decomposing waveforms into forward and backward wave components. This is followed by a discussion of the biomechanical phenomena that generate waves and the processes that modulate wave amplitude, both of which are critical for interpreting measured wave patterns. Finally, we provide a brief update on several emerging techniques/concepts in the wave analysis field, namely wave potential and the reservoir-excess pressure approach.

Relationship between arterial stiffness and variability of home blood pressure monitoring

Variability of blood pressure (BP) is known as a prognostic value for the subsequent target organ damage in hypertensive patients. Arterial stiffness is a risk factor for cardiovascular morbidity and mortality. The relationship between the arterial stiffness and the BP variability has been controversial. The objective of the present study was to investigate the relationship between arterial stiffness and home BP variability in patients with high normal BP and new onset hypertension (HTN).Four hundred sixty three patients (252 males, 49 ± 12 year-old) with high normal BP or HTN were enrolled. Using radial applanation tonometry, pulse wave analysis (PWA) was performed for evaluation of systemic arterial stiffness. All patients underwent both home BP monitoring (HBPM) and PWA. Home BP variability was calculated as the standard deviation (SD) of 7 measurements of HBPM. Multiple linear regression analysis was performed to estimate and test the independent effects of home BP variability on the arterial stiffness.Mutivariate analysis showed that both systolic and diastolic morning BP variabilities were correlated with arterial stiffness expressed as augmentation pressure (AP, β-coefficient = 1.622, P = .01 and β-coefficient = 1.07, P = .035). The SDs of systolic and diastolic BP of evening were also associated with AP (β-coefficient = 1.843, P = .001 and β-coefficient = 1.088, P = .036). The SDs of morning and evening systolic BP were associated with augmentation index (AI, β-coefficient = 1.583, P = .02 and β-coefficient = 1.792, P = .001) and heart rate (75 bpm) adjusted AI (β-coefficient = 1.592, P = .001 and β-coefficient = 1.792, P = .001).In present study, the variability of systolic BP was closely related with arterial stiffness. The home BP variability might be important indicator of arterial stiffness.

Evaluation of arterial stiffness in cardiac surgical patients using applanation tonometry

Context:

Applanation tonometry enables the noninvasive analysis of arterial pressure wave morphology. Applanation tonometry provides the augmentation index (AIx, %), an index of arterial stiffness that partially reflects arterial-ventricular (A-V) coupling. In addition, applanation tonometry provides the dP/dt (rate of intraventricular pressure variation over time), which reflects myocardial contractility, and the sub-endocardial viability ratio (SEVR, %), which is an indicator of myocardial oxygen supply and demand. There are no data on how cardiac surgery can modify these tonometry-derived indexes.

Aim:

The aim was to assess changes in AIx, dP/dt, and SEVR in patients undergoing cardiac surgery.

Subjects and Methods:

This observational study was conducted at the University Hospital of Siena. We studied 32 patients before cardiac surgery in intensive care unit (ICU) on admission and at ICU discharge. We measured AIx, dP/dt, and SEVR using applanation tonometry (SphygmoCor). Changes in variables over time were evaluated by analysis of variance for repeated measurements.

Results:

AIx decreased significantly from T1 [28.8%, interquartile range (IQR) 21.6–36.6%] to T2 (16.2% IQR 8.1–22.4%) and T3 (14.5% IQR 7.9–23.6%) (P = 0.01). dP/dt increased significantly from T1 (635 mmHg/ms, IQR 534–756 mmHg/ms) to T3 (751 mmHg/ms, IQR 651–1013 mmHg/ms; P = 0.03). The SEVR was lower at T2 than at T1, but returned toward T1 values by T3.

Conclusions:

Cardiac surgery was associated with an improvement in arterial stiffness, A-V coupling, and myocardial contractility as assessed using applanation tonometry. The results suggest, however, a transient imbalance between myocardial oxygen supply and demand in the immediate postoperative period.

The association between sympatho-vagal balance and central blood pressures

Purpose

High central blood pressure is more predictive of cardiovascular disease (CVD) versus high peripheral blood pressure. Measures of central pressures (CPs) include, central systolic blood pressure (CSBP) and central diastolic blood pressure. Measures of central pressures augmentation (CPsA) include augmentation pressure (AP) and the augmentation index @ 75 beats·min-1 (AIx@75). Increased sympathetic tone (ST) is also associated with CVD. The low to high frequency ratio (LF/HF) is often used to determine sympatho-vagal balance. Given the association between ST, CPs, CPsA and CVD there is a need to understand the association between these predictors of CVD. The aims of this study were to examine the association between the LF/HF ratio, CPs, and CPsA in men and women collectively and based on gender.

Methods

We measured the LF/HF ratio, CSBP, AP, and AIx@75 in 102 participants (41F/61M). The LF/HF ratio was determined via power spectral density analysis. CSBP, AP, and AIx@75 were determined via applanation tonometry.

Results

The LF/HF ratio was inversely associated with AP (r = -0.26) and AIx @75 (r = -0.29) in the combined group of men and women. The LF/HF ratio was inversely associated with CSBP (r = -0.27), AP (r = -0.28), and AIx@75 (r = -0.32) in men, but not in women.

Conclusion

There is an inverse association between the LF/HF ratio, AP, and AIx@75 in men and women combined. The association between the LF/HF ratio, CSBP, AP, and AIx@75, differs based on gender.

Maternal Glycemia During Pregnancy and Child Carotid Intima Media Thickness, Pulse Wave Velocity, and Augmentation Index

BACKGROUND

In women without diabetes, little is known about the consequences of hyperglycemia during pregnancy for the offspring's cardiovascular structure and function.

OBJECTIVE

To investigate the association of maternal glycemia during pregnancy with cardiovascular risk markers in their children in GUSTO, a Singaporean birth cohort study.

METHODS

Around 26 weeks' gestation, a 75 g oral glucose tolerance test was performed and fasting plasma glucose (FPG) and 2-hour postprandial plasma glucose (PPPG) concentrations were measured. Gestational diabetes mellitus (GDM) was defined using WHO 1999 diagnostic criteria. At 6 years of age, we measured the child's carotid intima-media thickness (cIMT), carotid-femoral pulse wave velocity (cfPWV), aortic augmentation index (AIx), and blood pressure (BP). Association of maternal glycemia during pregnancy with cardiovascular risk markers in their children were analyzed using multiple linear and logistic regressions.

RESULTS

Analysis were performed on 479 mother-child dyads. Higher maternal FPG was associated with higher cIMT and, in males, with a higher cfPWV in the offspring (adjusted β [CI 95%], cIMT: 0.08 per 10mm increase [0.02; 0.15], cfPWV: 0.36 m/s [0.01; 0.70]). Higher 2-hour PPPG was associated with higher cfPWV and AIx. Gestational diabetes mellitus was associated with higher AIx. No association was found between maternal glycemia and their offspring blood pressure.

CONCLUSIONS

among mothers without pre-existing diabetes, higher glycemia during pregnancy was associated with mild structural and functional vascular changes in their children at 6 years of age across a continuum. These results support the necessity to monitor maternal glycemia during pregnancy even in the absence of pre-existing diabetes or diagnosed GDM.

Novel Imaging Revealing Inner Dynamics for Cardiovascular Waveform Analysis via Unsupervised Manifold Learning

BACKGROUND

Cardiovascular waveforms contain information for clinical diagnosis. By learning and organizing the subtle change of waveform morphology from large amounts of raw waveform data, unsupervised manifold learning helps delineate a high-dimensional structure and display it as a novel 3-dimensional (3D) image. We hypothesize that the shape of this structure conveys clinically relevant inner dynamics information.

METHODS

To validate this hypothesis, we investigate the electrocardiography (ECG) waveform for ischemic heart disease and arterial blood pressure (ABP) waveform in dynamic vasoactive episodes. We model each beat or pulse to be a point lying on a manifold-like a surface-and use the diffusion map (DMap) to establish the relationship among those pulses. The output of the DMap is converted to a 3D image for visualization. For ECG datasets, first we analyzed the non-ST-elevation ECG waveform distribution from unstable angina to healthy control in the 3D image, and we investigated intraoperative ST-elevation ECG waveforms to show the dynamic ECG waveform changes. For ABP datasets, we analyzed waveforms collected under endotracheal intubation and administration of vasodilator. To quantify the dynamic separation, we applied the support vector machine (SVM) analysis and reported the total accuracy and macro-F1 score. We further performed the trajectory analysis and derived the moving direction of successive beats (or pulses) as vectors in the high-dimensional space.

RESULTS

For the non-ST-elevation ECG, a hierarchical tree structure comprising consecutive ECG waveforms spanning from unstable angina to healthy control is presented in the 3D image (accuracy = 97.6%, macro-F1 = 96.1%). The DMap helps quantify and visualize the evolving direction of intraoperative ST-elevation myocardial episode in a 1-hour period (accuracy = 97.58%, macro-F1 = 96.06%). The ABP waveform analysis of Nicardipine administration shows interindividual difference (accuracy = 95.01%, macro-F1 = 96.9%) and their common directions from intraindividual moving trajectories. The dynamic change of the ABP waveform during endotracheal intubation shows a loop-like trajectory structure, which can be further divided using the manifold learning knowledge obtained from Nicardipine.

CONCLUSIONS

The DMap and the generated 3D image of ECG or ABP waveforms provides clinically relevant inner dynamics information. It provides clues of acute coronary syndrome diagnosis, shows clinical course in myocardial ischemic episode, and reveals underneath physiological mechanism under stress or vasodilators.

Leukocyte telomere length is inversely associated with arterial wave reflection in 566 normotensive and never-treated hypertensive subjects

Telomeres are short segments in chromosome ends, the length of which is reduced during cell lifecycles. We examined the association of mean leukocyte telomere length (LTL) and short telomere proportion (STP) with hemodynamic variables in normotensive and never-treated hypertensive volunteers (n=566, 19-72 years). STP and mean LTL were determined using Southern blotting, and supine hemodynamics recorded using continuous tonometric pulse wave analysis and whole-body impedance cardiography. The analyses were adjusted for age, body mass index (BMI), alcohol use, smoking, plasma chemistry, and estimated glomerular filtration rate (eGFR). In univariate analyses, mean LTL and STP both correlated with age, BMI, eGFR, aortic blood pressure, augmentation index, and pulse wave velocity (p<0.05 for all). Mean LTL also correlated with systemic vascular resistance (p<0.05). In linear regression analyses of all hemodynamic variables, mean LTL was only an independent explanatory factor for augmentation index (Beta -0.006, p=0.032), while STP was not an explanatory factor for any of the hemodynamic variables, in contrast to age, BMI and several cardiovascular risk factors. To conclude, augmentation index was predominantly related with chronological aging, but also with mean LTL, suggesting that this variable of central wave reflection is a modest marker of vascular biological aging.

Accelerated Early Vascular Aging Among Adolescents With Obesity and/or Type 2 Diabetes Mellitus

Background The normal rate of subclinical vascular aging from adolescence to young adulthood has not been well-characterized. We conducted a 5-year longitudinal study among adolescents with normal-weight, obesity, and/or type 2 diabetes mellitus to examine trajectories of early vascular aging. Methods and Results Adolescents (mean [SD] age 17.6 [3.5]; 35.3% male) had either normal weight (n=141), obesity (n=156), or type 2 diabetes mellitus (n=151) at baseline. Primary metrics used for early vascular aging included measures of vascular structure (carotid intima-media thickness [cIMT]; common, internal, and bulb) and arterial stiffness (carotid-femoral pulse wave velocity, and augmentation index). Longitudinal (5-year) outcomes were examined using generalized estimating equations adjusting for baseline value, sex, race, and age. Compared with participants with normal weight, those with obesity had greater positive change in common cIMT (0.05 mm [0.03, 0.06]; P<0.001), bulb cIMT (0.02 mm [0.00, 0.05]; P=0.033), internal cIMT (0.03 mm [0.01, 0.05]; P<0.001), and pulse wave velocity carotid-femoral (0.38 m/sec [0.14, 0.61]; P=0.001), and those with type 2 diabetes mellitus had greater positive change in common cIMT (0.05 mm [0.04, 0.07]; P<0.001), bulb cIMT (0.06 mm [0.04, 0.09]; P<0.001), internal cIMT (0.04 mm [0.02, 0.07]; P<0.001), augmentation index (4.67% [2.20, 7.13]; P<0.001), and pulse wave velocity carotid-femoral (0.74 m/sec [0.46, 1.02]; P<0.001). Higher baseline systolic blood pressure was associated with greater positive change in common cIMT (0.007 mm [0.003, 0.011]; P<0.001), bulb cIMT (0.009 mm [0.002, 0.016]; P=0.01), internal cIMT (0.008 mm [0.003, 0.013]; P=0.001), and pulse wave velocity carotid-femoral (0.066 m/sec [0.002, 0.130]; P=0.042). Conclusions These longitudinal data support the hypothesis that the presence of obesity, type 2 diabetes mellitus, and elevated baseline systolic blood pressure in early life accelerates the progression of risk factors key in the development of early vascular aging.

Reconstruction of Continuous Brachial Arterial Pressure From Continuous Finger Arterial Pressure Using a Two-Level Optimization Strategy

OBJECTIVE

We attempt to reconstruct brachial arterial pressure (BAP) waves from finger arterial pressure waves measured using the vascular unloading technique without arm-cuff calibration. A novel method called two-level optimization (TOP) strategy is proposed as follows.

METHODS

We first derive a simplified transfer function (TF) based on a tube-load model with only two parameters to be estimated, a coefficient B and a time delay ∆t. Then, at level one, two minimization problems are formulated to estimate the optimal coefficient B^opt and time delay ∆t^opt. Then, we can derive an optimal TF h^opt(t). However, this derivation requires true (or reference) BAP waves. Therefore, at level two, we apply multiple linear regression (MLR) to further model the relationship between the derived optimal parameters and subjects' physiologic parameters. Hence, eventually, one can estimate coefficient B^MLR and time delay ∆t^MLR from subject's physiologic parameters to derive the MLR-based TF h^MLR(t) for the BAP reconstruction.

RESULTS

Twenty-one volunteers were recruited for the data collection. The mean ± standard deviation of the root mean square errors between the reference BAP waves and the BAP waves reconstructed by h^opt(t), h^MLR(t), and a generalized transfer function (GTF) were 3.46 ± 1.42 mmHg, 3.61 ± 2.28 mmHg, and 6.80 ± 3.73 mmHg (significantly larger with p < 0.01), respectively.

CONCLUSIONS

The proposed method can be considered as a semi-individualized TF which reconstructs significantly better BAP waves than a GTF.

SIGNIFICANCE

The proposed TOP strategy can potentially be useful in more general reconstruction of proximal BP waves.

Cardiovascular target organ damage in premenopausal systemic lupus erythematosus patients and in controls: Are there any differences?

OBJECTIVE

to analyze the presence of cardiac and vascular preclinical damage in premenopausal women with systemic lupus erythematosus (SLE) and controls, matched for demographic characteristics and for other cardiovascular risk factors.

METHODS

33 women (mean age 32 ± 7 years) with SLE clinically stable (SLEDAI Score 2.5 ± +1.5) and 33 controls, matched (MC) for sex, age, body mass index (BMI), clinic blood pressure (BP) and antihypertensive treatment (if present) underwent: 24-h BP monitoring, echocardiography with tissue Doppler analysis for left ventricular (LV) structure, systolic and diastolic function, echo-tracking carotid ultrasound for intima-media thickness (IMT) and carotid distensibility measurement, and pulse wave velocity measurement for aortic stiffness (PWV).

RESULTS

by definition no difference was observed for age, sex, BMI and clinic BP values; Framingham risk score was low in SLE and MC (1.3 ± 2.7 vs 1.5 ± 2.3%, p = ns). 24-h BP was similar in SLE and in MC. Systolic function parameters, including LV longitudinal systolic function, an early index of LV systolic dysfunction, were reduced in SLE as compared to MC. Carotid IMT and carotid and aortic stiffness parameters were not different in SLE and MC. At multivariate regression analysis, PWV was independently associated with LV mass in controls and with the steroid weekly dose in SLE patients.

CONCLUSIONS

in young patients with SLE and low activity index of the disease, we did not observe significant vascular alterations as compared to controls with similar CV risk. The early LV systolic impairment observed in SLE patients needs confirmation.

Determinants of Increased Central Excess Pressure in Dialysis: Role of Dialysis Modality and Arteriovenous Fistula

BACKGROUND

Arterial reservoir-wave analysis (RWA)-a new model of arterial hemodynamics-separates arterial wave into reservoir pressure (RP) and excess pressure (XSP). The XSP integral (XSPI) has been associated with increased risk of clinical outcomes. The objectives of the present study were to examine the determinants of XSPI in a mixed cohort of hemodialysis (HD) and peritoneal dialysis (PD) patients, to examine whether dialysis modality and the presence of an arteriovenous fistula (AVF) are associated with increased XSPI.

METHOD

In a cross-sectional study, 290 subjects (232 HD and 130 with AVF) underwent carotid artery tonometry (calibrated with brachial diastolic and mean blood pressure). The XSPI was calculated through RWA using pressure-only algorithms. Logistic regression was used for determinants of XSPI above median. Through forward conditional linear regression, we examined whether treatment by HD or the presence of AVF is associated with higher XSPI.

RESULTS

Patients with XSPI above median were older, had a higher prevalence of diabetes and cardiovascular disease, had a higher body mass index, and were more likely to be on HD. After adjustment for confounders, HD was associated with a higher risk of higher XSPI (odds ratio = 2.39, 95% confidence interval: 1.16-4.98). In a forward conditional linear regression analysis, HD was associated with higher XSPI (standardized coefficient: 0.126, P = 0.012), but on incorporation of AVF into the model, AVF was associated with higher XSPI (standardized coefficient: 0.130, P = 0.008) and HD was excluded as a predictor.

CONCLUSION

This study suggests that higher XSPI in HD patients is related to the presence of AVF.

Quantitative Comparison of the Performance of Piezoresistive, Piezoelectric, Acceleration, and Optical Pulse Wave Sensors

The accurate measurement of the arterial pulse wave is beneficial to clinical health assessment and is important for the effective diagnosis of many types of cardiovascular disease. A variety of sensors have been developed for the non-invasive detection of these waves, but the type of sensor has an impact on the measurement results. Therefore, it is necessary to compare and analyze the signals obtained under a range of conditions using various pulse sensors to aid in making an informed choice of the appropriate type. From the available types we have selected four: a piezoresistive strain gauge sensor (PESG) and a piezoelectric Millar tonometer (the former with the ability to measure contact force), a circular film acceleration sensor, and an optical reflection sensor. Pulse wave signals were recorded from the left radial, carotid, femoral, and digital arteries of 60 subjects using these four sensors. Their performance was evaluated by analyzing their susceptibilities to external factors (contact force, measuring site, and ambient light intensity) and by comparing their stability and reproducibility. Under medium contact force, the peak-to-peak amplitude of the signals was higher than that at high and low force levels and the variability of signal waveform was small. The optical sensor was susceptible to ambient light. Analysis of the intra-class correlation coefficients (ICCs) of the pulse wave parameters showed that the tonometer and accelerometer had good stability (ICC > 0.80), and the PESG and optical sensor had moderate stability (0.46 < ICC < 0.86). Intra-observer analysis showed that the tonometer and accelerometer had good reproducibility (ICC > 0.75) and the PESG and optical sensor had moderate reproducibility (0.42 < ICC < 0.91). Inter-observer analysis demonstrated that the accelerometer had good reproducibility (ICC > 0.85) and the three other sensors had moderate reproducibility (0.52 < ICC < 0.96). We conclude that the type of sensor and measurement site affect pulse wave characteristics and the careful selection of appropriate sensor and measurement site are required according to the research and clinical need. Moreover, the influence of external factors such as contact pressure and ambient light should be fully taken into account.

Central blood pressure for the management of hypertension: Is it a practical clinical tool in current practice?

Since noninvasive central blood pressure (BP) measuring devices are readily available, central BP has gained growing attention regarding its clinical application in the management of hypertension. The disagreement between central and peripheral BP has long been recognized. Some previous studies showed that noninvasive central BP may be better than the conventional brachial BP in association with target organ damages and long-term cardiovascular outcomes. Recent studies further suggest that the central BP strategy for confirming a diagnosis of hypertension may be more cost-effective than the conventional strategy, and guidance of hypertension management with central BP may result in less use of medications to achieve BP control. Despite the use of central BP being promising, more randomized controlled studies comparing central BP-guided therapeutic strategies with conventional care for cardiovascular events reduction are required because noninvasive central and brachial BP measures are conveniently available. In this brief review, the rationale supporting the utility of central BP in clinical practice and relating challenges are summarized.

Changes in hemodynamics associated with metabolic syndrome are more pronounced in women than in men

The increase in cardiovascular risk associated with metabolic syndrome (MS) seems higher in women than in men. We examined hemodynamics during head-up tilt in 252 men and 250 women without atherosclerosis, diabetes, or antihypertensive medication, mean age 48 years, using whole-body impedance cardiography and radial pulse wave analysis. MS was defined according to Alberti et al. 2009. Men and women with MS presented with corresponding elevations of systolic and diastolic blood pressure (10-14%, p ≤ 0.001) versus controls. Supine pulse wave velocity (16-17%, p < 0.001) and systemic vascular resistance (7-9%, p ≤ 0.026), and upright cardiac output (6-11%, p ≤ 0.008) were higher in both MS groups than controls. Elevation of supine aortic characteristic impedance was higher in women than in men with MS (16% vs. 8%, p = 0.026), and in contrast to men, no upright impedance reduction was observed in women. When upright, women but not men with MS showed faster return of reflected pressure wave (p = 0.036), and smaller decrease in left cardiac work (p = 0.035) versus controls. The faster upright return of reflected pressure, lower upright decrease in left cardiac work, and higher elevation of aortic characteristic impedance may contribute to the greater increase in MS-related cardiovascular risk in women than in men.

Plasma total calcium concentration is associated with blood pressure and systemic vascular resistance in normotensive and never-treated hypertensive subjects

Purpose: The underlying causes of primary hypertension are not fully understood. Evidence on the relation of plasma calcium concentration with blood pressure (BP) is inconsistent and relies largely on studies utilizing office BP measurements in populations using cardiovascular drugs. In many studies adjustment for confounders was not optimal. In this cross-sectional study we examined the association of plasma total calcium concentration with the haemodynamic determinants of blood pressure.Subjects and methods: Supine haemodynamics were recorded using pulse wave analysis, whole-body impedance cardiography, and heart rate variability analysis in 618 normotensive or never-treated hypertensive subjects (aged 19-72 years) without diabetes, cardiovascular or renal disease, or cardiovascular medications. Linear regression analysis was used to investigate factors associated with haemodynamic variables.Results: Mean age was 45.0 years, body mass index 26.8 kg/m², seated office BP 141/89 mmHg, and 307 subjects (49.7%) were male. Mean values of routine blood and plasma chemistry analyses were within the reference limits of the tests except for low-density lipoprotein cholesterol (3.05 mmol/l). In the laboratory, mean supine radial BP was 131/75 mmHg, and both systolic and diastolic BP correlated directly with plasma total calcium concentration (r = 0.25 and r = 0.22, respectively, p < 0.001 for both). In regression analysis plasma total calcium concentration was an independent explanatory variable for radial and aortic systolic and diastolic BP, and systemic vascular resistance, but not for cardiac output, pulse wave velocity, or any of the heart rate variability parameters.Conclusion: Plasma total calcium concentration was directly associated with systolic and diastolic BP and systemic vascular resistance in normotensive or never-treated hypertensive subjects without comorbidities and cardiovascular medications. Higher plasma calcium concentration potentially plays a role in primary hypertension via an effect on vascular resistance.

Noninvasive Cardiac Output and Central Systolic Pressure From Cuff-Pressure and Pulse Wave Velocity

GOAL

We introduce a novel approach to estimate cardiac output (CO) and central systolic blood pressure (cSBP) from noninvasive measurements of peripheral cuff-pressure and carotid-to-femoral pulse wave velocity (cf-PWV).

METHODS

The adjustment of a previously validated one-dimensional arterial tree model is achieved via an optimization process. In the optimization loop, compliance and resistance of the generic arterial tree model as well as aortic flow are adjusted so that simulated brachial systolic and diastolic pressures and cf-PWV converge towards the measured brachial systolic and diastolic pressures and cf-PWV. The process is repeated until full convergence in terms of both brachial pressures and cf-PWV is reached. To assess the accuracy of the proposed framework, we implemented the algorithm on in vivo anonymized data from 20 subjects and compared the method-derived estimates of CO and cSBP to patient-specific measurements obtained with Mobil-O-Graph apparatus (central pressure) and two-dimensional transthoracic echocardiography (aortic blood flow).

RESULTS

Both CO and cSBP estimates were found to be in good agreement with the reference values achieving an RMSE of 0.36 L/min and 2.46 mmHg, respectively. Low biases were reported, namely -0.04 ± 0.36 L/min for CO predictions and -0.27 ± 2.51 mmHg for cSBP predictions.

SIGNIFICANCE

Our one-dimensional model can be successfully "tuned" to partially patient-specific standards by using noninvasive, easily obtained peripheral measurement data. The in vivo evaluation demonstrated that this method can potentially be used to obtain central aortic hemodynamic parameters in a noninvasive and accurate way.

Dialysis initiation improves calcification propensity

Background

Cardiovascular morbidity and mortality is high in patients starting dialysis and could be related to modifications of calcification inducers and inhibitors by dialysis, promoting cardiovascular events. The impact of dialysis initiation on serum calcification propensity evolution and arterial stiffness is unknown. We therefore prospectively determined the evolution of the one-half maximal transition time (T50) value and its main determinants as well as pulse wave velocity over the first 3 months of dialysis initiation.

Methods

We analysed the evolution of T50, fetuin-A and mineral metabolism parameters before dialysis initiation (M0) and monthly until Month 3 (M3) in incident patients starting haemodialysis (HD) or peritoneal dialysis (PD) in two tertiary Swiss university hospitals. Arterial stiffness was assessed by pulse tonometry at M0 and M3 and biological parameters were compared between M0 and M3 and before/after HD. Linear mixed models were used to assess parameter evolution over time, taking into account repeated measures and other influencing variables.

Results

Forty-six patients on HD and 12 on PD were followed. Among them, 45 were male (78%) with a median age of 67 years (25th–75th quartile range 54–77). T50 significantly increased between M0 and M3 from 183 (120–266) to 246 min (175–330) (P &lt; 0.001). Fetuin-A, calcium and magnesium also increased while phosphate decreased. Factors associated with T50 changes over time were fetuin-A, phosphate and magnesium (P &lt; 0.001). Fetuin-A changes were associated with inflammation-related factors (albumin, C-reactive protein) but not calcium and phosphate levels. Arterial stiffness was not significantly modified over 3 months. PD and HD initiation showed similar trends.

Conclusions

Dialysis initiation significantly improves calcification propensity and fetuin-A levels. These modifications do not explain the high mortality related to dialysis initiation. The clinical relevance of using T50 values to initiate dialysis awaits further studies.

On the importance of the nonuniform aortic stiffening in the hemodynamics of physiological aging

Mathematical models of the arterial tree constitute a valuable tool to investigate the hemodynamics of aging and pathology. Rendering such models as patient specific could allow for the assessment of central hemodynamic variables of clinical interest. However, this task is challenging, particularly with respect to the tuning of the local area compliance that varies significantly along the arterial tree. Accordingly, in this study, we demonstrate the importance of taking into account the differential effects of aging on the stiffness of central and peripheral arteries when simulating a person’s hemodynamic profile. More specifically, we propose a simple method for effectively adapting the properties of a generic one-dimensional model of the arterial tree based on the subject’s age and noninvasive measurements of aortic flow and brachial pressure. A key element for the success of the method is the implementation of different mechanisms of arterial stiffening for young and old individuals. The designed methodology was tested and validated against in vivo data from a population of n = 20 adults. Carotid-to-femoral pulse wave velocity was accurately predicted by the model (mean error = 0.14 m/s, SD = 0.77 m/s), with the greatest deviations being observed for older subjects. In regard to aortic pressure, model-derived systolic blood pressure and augmentation index were both in good agreement (mean difference of 2.3 mmHg and 4.25%, respectively) with the predictions of a widely used commercial device (Mobil-O-Graph). These preliminary results encourage us to further validate the method in larger samples and consider its potential as a noninvasive tool for hemodynamic monitoring.

NEW & NOTEWORTHY We propose a technique for adapting the parameters of a validated one-dimensional model of the arterial tree using noninvasive measurements of aortic flow and brachial pressure. Emphasis is given on the adjustment of the arterial tree distensibility, which incorporates the nonuniform effects of aging on central and peripheral vessel elasticity. Our method could find application in the derivation of important hemodynamic indices, paving the way for novel diagnostic tools.

Relationship between arterial stiffness and chronic kidney disease in patients with primary hypertension

To investigate the association of noninvasive indices of arterial stiffness with chronic kidney disease (CKD) in patients with primary hypertension, 547 (mean age 60 years, 63% males) hypertensive hospital inpatients were recruited, comprising 337 hypertensives without CKD and 210 hypertensives with CKD. Noninvasive arterial stiffness indices were obtained, including central arterial haemodynamics derived from the radial artery waveform using SphygmoCor V8.0 system, carotid-femoral pulse wave velocity (cfPWV), large and small artery elasticity indices (C1, C2 respectively). Intima-media thickness (IMT) was evaluated by ultrasonography. The diagnosis of CKD was assessed by the estimated glomerular filtration rate (eGFR) or urinary albumin creatinine ratio (ACR). Compared with hypertension without CKD, hypertensive patients with CKD were older, had higher central systolic blood pressure, cfPWV, and IMT (all P < 0.01). With decreasing eGFR, cfPWV and augmentation index adjusted to heart rate of 75 bpm increased progressively whereas C2 decreased (P < 0.05) in subjects with CKD. In the overall population, cfPWV showed a significant trend of a negative association with eGFR (P = 0.04) after adjusting for age, gender, and brachial systolic blood pressure. Multiple logistic analysis showed that 1 SD (3 m/s) increase in cfPWV entailed a 1.35 (95% Cl: 1.018-1.790) times higher likelihood of the presence of CKD even after adjustment for confounding factors. The association of arterial stiffness and CKD suggests that cfPWV may be a potential hemodynamic index to evaluate cardiovascular risk in CKD patients with primary hypertension.

Coronary wave intensity patterns in stable coronary artery disease: influence of stenosis severity and collateral circulation

Objective

Wave intensity analysis is a method that allows separating pulse waves into components generated proximally and in the periphery of arterial trees, as well as characterising them as accelerating or decelerating. The early diastolic suction wave (eaDSW) is one of the most prominent wave events in the coronaries. The aim of this study was to determine whether (1) microvascular dilatation directly influences its energy, (2) stenosis severity can be assessed proximal to stenoses, (3) distal pulse wave entrapment exists in the presence of stenoses and (4) coronary collaterals influence wave entrapment.

Methods

In 43 coronary artery disease patients, Doppler flow velocity and pressure measurements were performed in a proximal coronary segment at rest, in a distal segment at rest, during adenosine-induced hyperaemia and during balloon occlusion. Wave energies were calculated as the area under the wave intensity curves.

Results

The eaDSW energy showed a significant increase during hyperaemia, but did not differ between proximal and distal segments. There was no significant correlation between eaDSW energy and coronary stenosis severity. Pulse wave entrapment could not be observed consistently in the distal segments. Consequently, the effect of coronary collaterals on pulse wave entrapment could not be studied.

Conclusions

Microvascular dilation in the coronary circulation increases distal eaDSW energy. However, it does not show any diagnostically useful variation between measurement sites, various stenosis degrees and amount of collateral flow. The assessment eaDSW and its reflections were not useful for the quantification of coronary stenosis severity or the collateral circulation in clinical practice.

Liquorice ingestion attenuates vasodilatation via exogenous nitric oxide donor but not via β2-adrenoceptor stimulation

We examined the effect of liquorice ingestion on haemodynamic responses to exogenous nitric oxide donor (nitroglycerin) and β2-adrenoceptor agonist (salbutamol), and 11β-hydroxysteroid dehydrogenase activity, in 21 volunteers and 21 reference subjects. Haemodynamic data was captured before and after sublingual nitroglycerin (0.25 mg) and inhaled salbutamol (400 μg) during orthostatic challenge utilising radial pulse wave analysis and whole-body impedance cardiography. The recordings were performed at baseline and following two weeks of liquorice intake (290-370 mg/d glycyrrhizin). Urinary cortisone and cortisol metabolites were examined. Liquorice intake elevated aortic systolic and diastolic blood pressure and systemic vascular resistance when compared with the reference group. Following research drug administration the liquorice-induced increase in systemic vascular resistance was observed in the presence of nitroglycerin (p<0.05) but no longer in the presence of salbutamol. Liquorice ingestion decreased cardiac chronotropic response to upright posture (p = 0.032) in unadjusted analysis, but when adjusted for age and sex the difference in the upright change in heart rate was no longer significant. The urinary cortisone to cortisol metabolite ratio decreased from 0.70 to 0.31 (p<0.001) after liquorice intake indicating significant inhibition of the 11β-hydroxysteroid dehydrogenase type 2. In the reference group the haemodynamic variables remained virtually unchanged. These results suggest that liquorice exposure impaired vasodilatation in vivo that was induced by exogenous nitric oxide donor but not that induced by β2-adrenoceptor stimulation. Trial registration: EU Clinical Trials Register 2006-002065-39 ClinicalTrials.gov NCT01742702.

Age-Dependent Impairment in Endothelial Function and Arterial Stiffness in Former High Class Male Athletes Is No Different to That in Men With No History of Physical Training

Background

Physical activity is generally considered to exert positive effects on the cardiovascular system in humans. However, surprisingly little is known about the delayed effect of professional physical training performed at a young age on endothelial function and arterial stiffness in aging athletes. The present study aimed to assess the impact of long‐lasting professional physical training (endurance and sprint) performed at a young age on the endothelial function and arterial stiffness reported in older age in relation to glycocalyx injury, prostacyclin and nitric oxide production, inflammation, basal blood lipid profile, and glucose homeostasis.

Methods and Results

This study involved 94 male subjects with varied training backgrounds, including young athletes (mean age ∼25 years), older former high class athletes (mean age ∼60 years), and aged‐matched untrained control groups. Aging increased arterial stiffness, as reflected by an enhancement in pulse wave velocity, augmentation index, and stiffness index (P<10⁻⁴), as well as decreased endothelial function, as judged by the attenuation of flow‐mediated vasodilation (FMD) in the brachial artery (P=0.03). Surprisingly, no effect of the training performed at a young age on endothelial function and arterial stiffness was observed in the former athletes. Moreover, no effect of training performed at a young age (P>0.05) on blood lipid profile, markers of inflammation, and glycocalyx shedding were observed in the former athletes.

Conclusions

Our study clearly shows that aging, but not physical training history, represents the main contributing factor responsible for decline in endothelial function and increase in arterial stiffness in former athletes.

Correlations between invasively measured aortic pressures and left ventricular end-diastolic pressure in patients undergoing coronary angiography

OBJECTIVE

Data on ventricular-arterial coupling using invasive hemodynamic studies are limited. This study was performed to clarify the interaction between aortic pressures and left ventricular end-diastolic pressure (LVEDP) using invasive catheterization.

PATIENTS AND METHODS

A total of 104 consecutive stable patients (mean age, 65.8 ± 10.0 years; 56% men) undergoing invasive coronary angiography (ICA) were prospectively evaluated. LVEDP and central aortic pressures [systolic blood pressure (aSBP) and diastolic blood pressure (aDBP)] were sequentially measured using a pigtail catheter before ICA. Aortic pulse pressure (aPP) was defined by the difference between aSBP and aDBP.

RESULTS

A total of 82 patients (79%) had obstructive coronary artery disease (≥50% stenosis). The mean LVEDP value was 18.7 ± 6.4 mmHg. Univariable analyses showed that aSBP (r = 0.309, P = 0.001) and aPP (r = 0.286, P = 0.003) significantly correlated with LVEDP, whereas aDBP was not correlated with LVEDP (P > 0.05). Multivariable analysis revealed that aSBP (β = 0.345, P = 0.001) and aPP (β = 0.276, P = 0.018) remained independent predictors of LVEDP even after controlling for potential confounders.

CONCLUSION

Invasively measured aSBP and aPP were independently associated with invasively measured LVEDP in patients undergoing ICA. This result provides additional evidence of a close interaction between central aortic pressure and LV diastolic function in this population.

Estimation of central arterial pressure from the radial artery in patients undergoing invasive neuroradiological procedures

Backgrounds

Central arterial pressure can be derived from analysis of the peripheral artery waveform. The aim of this study was to compare central arterial pressures measured from an intra-aortic catheter with peripheral radial arterial pressures and with central arterial pressures estimated from the peripheral pressure wave using a pressure recording analytical method (PRAM).

Methods

We studied 21 patients undergoing digital subtraction cerebral angiography under local or general anesthesia and equipped with a radial arterial catheter. A second catheter was placed in the ascending aorta for central pressure wave acquisition. Central (AO) and peripheral (RA) arterial waveforms were recorded simultaneously by PRAM for 90–180 s. During an off-line analysis, AO pressures were reconstructed (AO_rec) from the RA trace using a mathematical model obtained by multi-linear regression analysis. The AO_rec values obtained by PRAM were compared with the true central pressure value obtained from the catheter placed in the ascending aorta.

Results

Systolic, diastolic and mean pressures ranged from 79 to 180 mmHg, 47 to 102 mmHg, and 58 to 128 mmHg, respectively, for AO, and 83 to 174 mmHg, 47 to 107 mmHg, and 60 to 129 mmHg, respectively, for RA. The correlation coefficients between AO and RA were 0.86 (p < 0.01), 0.83 (p < 0.01) and 0.86 (p < 0.01) for systolic, diastolic and mean pressures, respectively, and the mean differences − 0.3 mmHg, 2.4 mmHg and 1.5 mmHg. The correlation coefficients between AO and AO_rec were 0.92 (p < 0.001), 0.87 (p < 0.001) and 0.92 (p < 0.001), for systolic, diastolic and mean pressures, respectively, and the mean differences 0.01 mmHg, 1.8 mmHg and 1.2 mmHg.

Conclusions

PRAM can provide reliable estimates of central arterial pressure.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0844-1) contains supplementary material, which is available to authorized users.

Noninvasive validation of central and peripheral augmentation index estimated by a novel wrist-worn tonometer

BACKGROUND

The validation of new blood pressure devices with easier use and more rapid data collection may facilitate the incorporation of these measures into clinical practice. We analyze the reliability and validity of Pulse Wave Analysis as reported by a novel wrist-worn device, easy and quick to use, comparing central and peripheral augmentation index (AIx) with the same measures from the SphygmoCor. Additionally, we analyzed clinical relevance through the association of the Pulse Wave Analysis, as reported by a novel wrist-worn device, with other cardiovascular parameters.

METHODS

Cross-sectional study including 254 participants. Mean age was 51.9 ± 13.4 years and 53% were women.

MEASUREMENTS

peripheral AIx (PAIx) and central AIx (CAIx) by the wrist-worn device and SphygmoCor (MM3); carotid-femoral (cf) pulse wave velocity (PWV) by SphygmoCor (MM3); cardioankle-vascular index (CAVI), ankle-brachial index (ABI) and brachial-ankle (ba) PWV by the Vasera device and carotid-intima media thickness (IMT) by ultrasonography.

RESULTS

Intra-observer intra-class correlation coefficient (ICC) for PAIx was 0.886 (95% CI 0.803-0.934) and for CAIx 0.943 (95% CI 0.901-0.968) with Bland Altman limits of agreement -0.75 (-23.8 to 21.8) and 0.08 (-15.7 to 15.9), respectively. Inter-observer ICC for PAIx was 0.952 (95% CI 0.915-0.972) and CAIx 0.893 (95% CI 0.811-0.939) with limits of agreement -0.45 (-13.7 to 12.8) and 0.43 (-17.7 to 18.5), respectively. Comparing the wrist-worn device with SphygmoCor, the ICC was 0.849 (95% CI 0.798-0.887) for PAIx, and 0.783 (95% CI 0.711-0.838) for CAIx. In Bland-Altman, limits of agreement for PAIx 1.03 (-20.67 to 22.73), and for CAIx -2.14 (-24.79 to 20.50). PAIx and CAIx, from the wrist-worn device, correlated with age, CAVI, ABI, baPWV, cfPWV, IMT, glomerular filtration and cardiovascular risk.

CONCLUSION

AIx measurements by wrist-worn device shows a good intra-observer and inter-observer reliability, inter-device noninvasive reliability and validity when compared with SphygmoCor, and clinical relevance by association with measures of vascular structure and function, end-organ damage and cardiovascular risk.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02623894; https://clinicaltrials.gov/ct2/show/NCT02623894.

Tapered vs. Uniform Tube-Load Modeling of Blood Pressure Wave Propagation in Human Aorta

In this paper, tapered vs. uniform tube-load models are comparatively investigated as mathematical representation for blood pressure (BP) wave propagation in human aorta. The relationship between the aortic inlet and outlet BP waves was formulated based on the exponentially tapered and uniform tube-load models. Then, the validity of the two tube-load models was comparatively investigated by fitting them to the experimental aortic and femoral BP waveform signals collected from 13 coronary artery bypass graft surgery patients. The two tube-load models showed comparable goodness of fit: (i) the root-mean-squared error (RMSE) was 3.3+/−1.1 mmHg in the tapered tube-load model and 3.4+/−1.1 mmHg in the uniform tube-load model; and (ii) the correlation was r = 0.98+/−0.02 in the tapered tube-load model and r = 0.98+/−0.01 mmHg in the uniform tube-load model. They also exhibited frequency responses comparable to the non-parametric frequency response derived from the aortic and femoral BP waveforms in most patients. Hence, the uniform tube-load model was superior to its tapered counterpart in terms of the Akaike Information Criterion (AIC). In general, the tapered tube-load model yielded the degree of tapering smaller than what is physiologically relevant: the aortic inlet-outlet radius ratio was estimated as 1.5 on the average, which was smaller than the anatomically plausible typical radius ratio of 3.5 between the ascending aorta and femoral artery. When the tapering ratio was restricted to the vicinity of the anatomically plausible typical value, the exponentially tapered tube-load model tended to underperform the uniform tube-load model (RMSE: 3.9+/−1.1 mmHg; r = 0.97+/−0.02). It was concluded that the uniform tube-load model may be more robust and thus preferred as the representation for BP wave propagation in human aorta; compared to the uniform tube-load model, the exponentially tapered tube-load model may not provide valid physiological insight on the aortic tapering, and its efficacy on the goodness of fit may be only marginal.