Clinical application of wave intensity for the treatment of essential hypertension

Cardiovascular challenges in the era of antiretroviral therapy for AIDS/ HIV: A comprehensive review of research advancements, pathophysiological insights, and future directions

Cardiovascular disease, particularly coronary heart disease, is becoming more common among those living with HIV. Individuals with HIV face an increased susceptibility to myocardial infarction, also known as a heart attack, as compared to the general population in developed countries. This heightened risk can be attributed mainly to the presence of effective antiretroviral drugs and the resulting longer lifespan. Some cardiac issues linked to non-antiretroviral medications, including myocarditis, endocarditis, cardiomyopathy with dilation, pulmonary hypertension, and oedema of the heart, may affect those not undergoing highly active antiretroviral therapy (ART). Impaired immune function and systemic inflammation are significant contributors to this phenomenon after initiating highly aggressive antiretroviral treatment ART. It is becoming more challenging to determine the best course of treatment for HIV-associated cardiomyopathy due to new research suggesting that protease inhibitors might have a negative impact on the development of HF. Currently, the primary focus of research on ART medications is centered on the cardiovascular adverse effects of nucleoside reverse transcriptase inhibitors and protease inhibitors. This review paper thoroughly evaluates the advancements achieved in cardiovascular disease research and explores the potential implications for prospects. Additionally, it considers the field's future prospects while examining how ART might be altered and its clinical applications.

Laryngeal Cyst in Children : A Retrospective Analysis

Aim: To study the presentation, management and outcome of laryngeal cysts in children. Materials and methods: This is a retrospective observational study of children with Laryngeal cysts who were managed in the Department of Paediatric Surgery between April 2015 to Jan 2022. Observations and Results: Eight children with laryngeal cysts were included, 5 were girls. Age ranged from 3 days to 10 years (median 5 months). Weight ranged from 3kg to 40kg (median 6.3 kg). All presented with stridor. Three children had co-morbid conditions, one each with Leucocyte adhesion deficiency type -1, atrial septal defect & PHACES syndrome. Two children had severe respiratory distress and required tracheostomy at presentation. All children underwent MLB. The cysts were 2 subglottic cysts (one inflammatory cyst) and 6 vallecular cyst. Five underwent endoscopic excision of cysts, 1 underwent excision with lateral cervical approach, 1 underwent endoscopic de-roofing of cyst and airway reconstruction with anterior costal cartilage graft (associated Sub glottis stenosis). Conclusion: Laryngeal cysts are a rare cause of stridor in children. MLB is the best diagnostic tool. Treatment with excision / deroofing of the cyst endoscopically, is safe and effective in paediatric age group.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03495-w.

Sepsis and bronchopulmonary dysplasia as potential risk factors for parenteral nutrition-associated cholestasis in neonates: a meta-analysis of retrospective studies

INTRODUCTION

The aim of this study was to evaluate whether sepsis and bronchopulmonary dysplasia (BPD) are risk factors for parenteral nutrition-associated cholestasis (PNAC) and to provide suggestions for the prevention of PNAC in infants.

EVIDENCE ACQUISITION

Electronic databases (PubMed, EBSCO, Elsevier, Springer, Wiley, and Cochrane) were searched for studies published up to October 22, 2017. Associations between sepsis, BPD and PNAC were assessed using odds ratios (ORs) and 95% confidence intervals (CIs). Heterogeneity was assessed using the I2 statistic, and subgroup analyses were performed.

EVIDENCE SYNTHESIS

Nine studies incorporating a total of 2248 cases were included in the meta-analysis. Sepsis was significantly associated with PNAC (pooled OR=2.04; 95% CI: 1.23-2.85), but BPD was not (pooled OR=1.22; 95% CI: 0.65-1.78). In a subgroup analysis, BPD was not associated with PNAC in either the non-Asian group (pooled OR=1.38; 95% CI: 0.58-2.18) or the Asian group (pooled OR=1.05; 95% CI: 0.26-1.84).

CONCLUSIONS

Sepsis, but not BPD, was a risk factor for PNAC in this meta-analysis. Further studies are needed to confirm the findings.

Fungal commensalism modulated by a dual-action phosphate transceptor

Successful host colonization by fungi in fluctuating niches requires response and adaptation to multiple environmental stresses. However, our understanding about how fungal species thrive in the gastrointestinal (GI) ecosystem by combing multifaceted nutritional stress with respect to homeostatic host-commensal interactions is still in its infancy. Here, we discover that depletion of the phosphate transceptor Pho84 across multiple fungal species encountered a substantial cost in gastrointestinal colonization. Mechanistically, Pho84 enhances the gastrointestinal commensalism via a dual-action activity, coordinating both phosphate uptake and TOR activation by induction of the transcriptional regulator Try4 and downstream commensalism-related transcription. As such, Pho84 promotes Candida albicans commensalism, but this does not translate into enhanced pathogenicity. Thus, our study uncovers a specific nutrient-dependent dual-action regulatory pathway for Pho84 on fungal commensalism.

Degradation of methylene blue using Co-dopant of Mg and Se into hydroxyapatite composite

In this work, a comparative study of different Magnesium ions content was incorporated into hydroxyapatite (HAP) modified with selenite ions aiming to develop the degradation performance of methylene blue. Although the dopant metal (Mg²⁺ ) has a relatively low ratio, it makes a change in microstructure, morphology, surface area, external surface charge, particle size, and degradation performance. The effect of magnesium and selenium binary doping on microstructural and degradation of methylene blue has been evaluated. The external surface charge measured by zeta potential clarified that the highest negativity was -11.8 mV and it was accomplished in 1.0Mg/Se-HAP. Also, the roughness average grew from 36.8 nm reaching 59.2 nm upon the additional Mg (II). Moreover, TEM micrographs showed that compositions were formed in rod shapes. The process of degradation are optimized, showing effectiveness in methylene blue (MB) degradation of 62.4 % after 150 min of exposure to visible light. Electrostatic attraction and H-bonding and coordination have a vital role in the adsorption process. The recyclability of the as-prepared compositions exhibited that the effectiveness has been reduced to be about 54.2 % after five times of re-using.

Retro-enantio isomer of angiopep-2 assists nanoprobes across the blood-brain barrier for targeted magnetic resonance/fluorescence imaging of glioblastoma

Glioblastoma (GBM), one of the most common primary intracranial malignant tumours, is very difficult to be completely excised by surgery due to its irregular shape. Here, we use an MRI/NIR fluorescence dual-modal imaging nanoprobe that includes superparamagnetic iron oxide nanoparticles (SPIONs) modified with indocyanine (Cy7) molecules and peptides (ANG or DANG) to locate malignant gliomas and guide accurate excision. Both peptides/Cy7-SPIONs probes displayed excellent tumour-homing properties and barrier penetrating abilities in vitro, and both could mediate precise aggregation of the nanoprobes at gliomas sites in in vivo magnetic resonance imaging (MRI) and ex vivo near-infrared (NIR) fluorescence imaging. However, compared with ANG/Cy7-SPIONs probes, DANG/Cy7-SPIONs probes exhibited better enhanced MR imaging effects. Combining all these features together, this MRI/NIR fluorescence imaging dual-modal nanoprobes modified with retro-enantio isomers of the peptide have the potential to accurately display GBMs preoperatively for precise imaging and intraoperatively for real-time imaging.

Perfluoroalkyl Substances Stimulate Insulin Secretion by Islet β Cells via G Protein-Coupled Receptor 40

The potential causal relationship between exposure to environmental contaminants and diabetes is troubling. Exposure of perfluoroalkyl substances (PFASs) is found to be associated with hyperinsulinemia and the enhancement of insulin secretion by islet β cells in humans, but the underlying mechanism is still unclear. Here, by combining in vivo studies with both wild type and gene knockout mice and in vitro studies with mouse islet β cells (β-TC-6), we demonstrated clearly that 1 h exposure of perfluorooctanesulfonate (PFOS) stimulated insulin secretion and intracellular calcium level by activating G protein-coupled receptor 40 (GPR40), a vital free fatty acid regulated membrane receptor on islet β cells. We further showed that the observed effects of PFASs on the mouse model may also exist in humans by investigating the molecular binding interaction of PFASs with human GPR40. We thus provided evidence for a novel mechanism for how insulin-secretion is disrupted by PFASs in humans.

Crop Improvement Through Temperature Resilience

Abnormal environmental temperature affects plant growth and threatens crop production. Understanding temperature signal sensing and the balance between defense and development in plants lays the foundation for improvement of temperature resilience. Here, we summarize the current understanding of cold signal perception/transduction as well as heat stress response. Dissection of plant responses to different levels of cold stresses (chilling and freezing) illustrates their common and distinct signaling pathways. Axillary bud differentiation in response to chilling is presented as an example of the trade-off between defense and development. Vernalization is a cold-dependent development adjustment mediated by O-GlcNAcylation and phosphorylation to sense long-term cold. Recent progress on major quantitative trait loci genes for heat tolerance has been summarized. Molecular mechanisms in utilizing temperature-sensitive sterility in super hybrid breeding in China are revealed. The way to improve crop temperature resilience using integrative knowledge of omics as well as systemic and synthetic biology, especially the molecular module program, is summarized.

Comparison of invasive and non-invasive aortic wave intensity and wave power analyses in sheep

OBJECTIVE

Wave intensity (WI) and wave power (WP) analyses are powerful approaches for assessing ventricular-vascular interactions and arterial dynamics using invasive and non-invasive methods. However, in vivo comparison of these methods for large arteries is lacking. This study assessed agreement, correlation and relative changes in wave size in invasive and non-invasive aortic WI/WP analyses, and associated sources of error.

APPROACH

The proximal descending thoracic aorta (DTA) of nine wethers was instrumented with a micromanometer and perivascular transit-time flow probe to measure high-fidelity blood pressure (P) and flow (Q) for invasive WI/WP analyses at baseline and during haemodynamic perturbations produced by cardiac pacing, distal DTA constriction and dobutamine-induced inotropic stimulation. In 212 experimental runs, concurrent echocardiographic DTA diameter and velocity (U) data were acquired for non-invasive WI/WP analyses, with measurement of forward compression wave (FCW), backward compression wave (BCW) and forward decompression wave (FDW) cumulative intensity (CI), cumulative power (CP) and wave-related pressure changes (ΔP).

MAIN RESULTS

Although agreement between invasive and non-invasive FCW, BCW and FDW CI/CP measures was variable (bias  -84% to  +7%), correlation was good (R  =  0.66-0.84), with lower bias and higher correlation for ΔP variables and similar relative changes in FCW and BCW CI/ΔP during haemodynamic perturbations. Main error sources were overestimation of invasive U due to assumed fixed vessel diameter, inaccuracies in non-invasive Q, and non-invasive underestimation of peak P/U and Q rates of change.

SIGNIFICANCE

Despite variable agreement, non-invasive CI/CP indices correlate well with invasive measurements, and detect relative changes in major waves induced by haemodynamic perturbations.

Heme oxygenase-1 ameliorates hypoxia/reoxygenation via suppressing apoptosis and enhancing autophagy and cell proliferation though Sirt3 signaling pathway in H9c2 cells

Cardiomyocyte infarction could lead to high morbidity and mortality worldwide. Recent studies demonstrated that Heme oxygenase-1 (HO-1) could exert cardiac protective effect and arouse attention. However, the detailed mechanism is still unclear. Our study provided evidences of the protective effect of HO-1 overexpression on cardiomyocytes against hypoxia/reoxygenation (H/R). We divided the treatment into four groups: the control group, H/R group, H/R+HO-1 group, and H/R+Null group. Immunofluorescent study was utilized to label the BrdU-positive and LC3-positive cells. Flow cytometry and TUNEL assay were used to examine the cell apoptosis. Protein levels of Bax, Bcl-2, Sirt3, beclin-1, LC3-I, and LC3-II were both measured using western blotting. The results indicated that HO-1 overexpression decreased the cell apoptosis and enhanced the cell proliferation. The level of Sirt3 and autophagy were also increased in H/R+HO-1 group compared with H/R group. However, ZnPP, a HO-1 inhibitor, and SiRNA of Sirt3 are both reversed the decrease of cell apoptosis of HO-1 overexpression. Moreover, ZnPP also decreased the expression of Sirt3 in HO-1 overexpression treatment group. In summary, HO-1 overexpression protects cardiomyocytes against H/R injury via ameliorating cell apoptosis and enhancing cell proliferation and autophagy through Sirt3 signaling pathway.

Vallecular cyst in the pediatric population: Evaluation and management

OBJECTIVE

To review the presentation of pediatric vallecular cysts and outline an approach for evaluation and management.

METHODS

Medical records of patients diagnosed with vallecular cyst between 2005 and 2017 were reviewed. Data on demographics, clinical characteristics, diagnostic methods, surgical procedures, and outcomes were collected and analyzed. A comprehensive literature search for pediatric cases of vallecular cyst was conducted for comparative analysis.

RESULTS

Twenty patients underwent surgery for congenital vallecular cysts during the study period. Age at diagnosis ranged from birth to 8 years (median age = 1.1 years). The most common preoperative symptom was inspiratory stridor (45%) followed by feeding difficulties (40%). Eight patients (40%) initially presented with laryngomalacia and 7 (35%) with feeding difficulties. Imaging was obtained in 16 patients and consisted of plain films, ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI). Marsupialization of the cyst was performed in all 20 patients. Three patients (15%) presented with recurrence.

CONCLUSION

Vallecular cysts can cause feeding difficulties due to upper airway obstruction and pressure at the laryngeal inlet. Diagnostic work-up for vallecular cysts should include a detailed medical history, complete head and neck examination including endoscopic examination, and appropriate imaging, as each of these components complements the histopathologic findings. Our findings indicate that performing marsupialization is associated with low rate of recurrence or complication.

[Left ventricular Tei-index for evaluation of cardiac function in hypertensive patients with left ventricular hypertrophy after radiochemotherapy]

OBJECTIVE

To assess the clinical value of left ventricular Tei-index in early evaluation of cardiac function in hypertensive patients with left ventricular hypertrophy after radiochemotherapy.

METHODS

Thirty hypertensive patients with malignancies and left ventricular hypertrophy and 30 hypertensive patients with malignancies without left ventricular hypertrophy were enrolled in this study, with 30 normotensive patients with malignancies as the control group. Left ventricular Tei-index and cardiac function indexes of the patients were detected using Doppler echocardiography before and after radiochemotherapy, and the changes in the cardiac function index and left ventricular Tei-index were compared among the 3 groups.

RESULTS

After radiochemotherapy, left ventricular Tei-index was significantly higher in hypertensive patients with left ventricular hypertrophy than in the control patients and hypertensive patients without left ventricular hypertrophy (P<0.05), and was similar between the latter two groups. No significant differences were found in the changes of left ventricular ejection fraction (EF), ratio of the early to late ventricular filling velocities (E/A ratio), or end-systolic volume (EDV) among the 3 groups after radiochemotherapy.

CONCLUSION

Tei-index is more sensitive than traditional echocardiography in assessing the changes of cardiac functions in hypertensive patients with left ventricular hypertrophy after chemotherapy.

Metformin ameliorates hypoxia/reoxygenation-induced cardiomyocyte apoptosis based on the SIRT3 signaling pathway

Myocardial hypoxia/reoxygenation (H/R) injury is one of the main causes of death and disability worldwide. However, a limited number of therapies are available to minimize the detrimental effects of this injury. Recently, researchers have demonstrated that metformin exerts direct cardioprotective effects against H/R. The aim of this study was to investigate the underlying mechanisms of how metformin affects myocardial hypoxia/reoxygenation (H/R) injury. In our study, the activities of lactate dehydrogenase (LDH) and superoxide dismutase (SOD) as well as the levels of malondialdehyde (MDA) were measured. Following H/R injury, LDH activity and MDA levels were evidently increased, while SOD activity and cell viability significantly decreased. Surprisingly, metformin downregulated the levels of relative reactive oxygen species (ROS) and upregulated the levels of relative SOD following H/R injury. Furthermore, metformin-treated cells exhibited reduced cell death, which was demonstrated to be associated with increased SIRT3 expression compared to that in the control group, as evidenced by blocking of the protective effects of metformin on cell apoptosis by the SIRT3 inhibitor Nicotinamide (NAM). Therefore, our results demonstrate that metformin improves cells viability following H/R, and this cardioprotective effect is partly mediated by the SIRT3 signaling pathway.

A review of wave mechanics in the pulmonary artery with an emphasis on wave intensity analysis

Mean pulmonary arterial pressure and pulmonary vascular resistance (PVR) remain the most common haemodynamic measures to evaluate the severity and prognosis of pulmonary hypertension. However, PVR only captures the non-oscillatory component of the right ventricular hydraulic load and neglects the dynamic compliance of the pulmonary arteries and the contribution of wave transmission. Wave intensity analysis offers an alternative way to assess the pulmonary vasculature in health and disease. Wave speed is a measure of arterial stiffness, and the magnitude and timing of wave reflection provide information on the degree of impedance mismatch between the proximal and distal circulation. Studies in the pulmonary artery have demonstrated distinct differences in arterial wave propagation between individuals with and without pulmonary vascular disease. Notably, greater wave speed and greater wave reflection are observed in patients with pulmonary hypertension and in animal models exposed to hypoxia. Studying wave propagation makes a valuable contribution to the assessment of the arterial system in pulmonary hypertension, and here, we briefly review the current state of knowledge of the methods used to evaluate arterial waves in the pulmonary artery.

Children's Bonding with Parents and Grandparents and Its Associated Factors

Previous literature has focused on the importance of both parental and grandparental bonding. However, few studies have been conducted to measure children's bonding with parents and grandparents simultaneously, especially tested by the same instrument that offers more comparable results. Therefore, we studied the relationships between parental and grandparental bonding using the Parental Bonding Instrument (PBI), and possible associations between these bonds and sociodemographic variables in 905 Chinese children aged 10-14 years. Children's bonding with mother, father, and grandparents were positively correlated, and the final mixed-effect model showed that several sociodemographic factors (e.g., gender, only children, parents' marital status, and mother's occupation) were associated with parental and grandparental bonding.

Improved antifouling and antimicrobial efficiency of ultrafiltration membranes with functional carbon nanotubes

In this study, functional polymer brush grafted carbon nanotubes (p-CNTs) were developed as multifunctional modifiers for PES membrane modification.

Leiomyosarcoma of the great saphenous vein

A 56-year-old male patient presented with a complaint of two painful, hard, palpable nodules in the right lower limb. A Doppler ultrasound scan revealed the presence of nodules, likely to be neoplastic. Computed angiography showed two solid hypervascular nodules in the right great saphenous vein, fed by branches of the posterior tibial artery. Embolization of the nodules using surgical cyanoacrylate was performed, followed by an excisional biopsy. Anatomical pathology and immunohistochemical analysis identified the nodule as a high-grade leiomyosarcoma, characterized by ten mitotic figures per ten high-power fields, necrosis and cell pleomorphism. Immunohistochemical analysis results were positive for caldesmon and desmin labeling. A second surgical procedure was performed to enlarge the free margins.

One-pot cross-linked copolymerization for the construction of robust antifouling and antibacterial composite membranes

This study reports a highly efficient, convenient and universal protocol for the fabrication of robust antifouling and antibacterial polymeric membranes via one-pot cross-linked copolymerization of functional monomers.

Quantification of the spatial strain distribution of scoliosis using a thin-plate spline method

The objective of this study was to quantify the three-dimensional spatial strain distribution of a scoliotic spine by nonhomogeneous transformation without using a statistically averaged reference spine. The shape of the scoliotic spine was determined from computed tomography images from a female patient with adolescent idiopathic scoliosis. The shape of the scoliotic spine was enclosed in a rectangular grid, and symmetrized using a thin-plate spline method according to the node positions of the grid. The node positions of the grid were determined by numerical optimization to satisfy symmetry. The obtained symmetric spinal shape was enclosed within a new rectangular grid and distorted back to the original scoliotic shape using a thin-plate spline method. The distorted grid was compared to the rectangular grid that surrounded the symmetrical spine. Cobb's angle was reduced from 35° in the scoliotic spine to 7° in the symmetrized spine, and the scoliotic shape was almost fully symmetrized. The scoliotic spine showed a complex Green-Lagrange strain distribution in three dimensions. The vertical and transverse compressive/tensile strains in the frontal plane were consistent with the major scoliotic deformation. The compressive, tensile and shear strains on the convex side of the apical vertebra were opposite to those on the concave side. These results indicate that the proposed method can be used to quantify the three-dimensional spatial strain distribution of a scoliotic spine, and may be useful in quantifying the deformity of scoliosis.

Orthostatic hypertension-a new haemodynamic cardiovascular risk factor

Orthostatic hypertension-a condition characterized by a hyperactive pressor response to orthostatic stress-is an emerging risk factor for cardiovascular disease and is associated with hypertensive target-organ damage (resulting in silent cerebrovascular disease, left ventricular hypertrophy, carotid atherosclerosis and/or chronic kidney disease) and cardiovascular events (such as coronary artery disease and lacunar stroke). The condition is also considered to be a form of prehypertension as it precedes hypertension in young, normotensive adults. Orthostatic blood pressure changes can be assessed using orthostatic stress tests, including clinic active standing tests, home blood pressure monitoring and the head-up tilting test. Devices for home and for ambulatory blood pressure monitoring that are equipped with position sensors and do not induce a white-coat effect have increased the sensitivity and specificity of diagnosis of out-of-clinic orthostatic hypertension. Potential major mechanisms of orthostatic hypertension are sympathetic hyperactivity (as a result of hypersensitivity of the cardiopulmonary and arterial baroreceptor reflex) and α-adrenergic hyperactivation. Orthostatic hypertension is also associated with morning blood pressure surge and extreme nocturnal blood pressure dipping, both of which increase the pulsatile haemodynamic stress of central arterial pressure and blood flow in patients with systemic haemodynamic atherothrombotic syndrome.

Arterial wave reflection during antihypertensive therapy with barnidipine: a 6-month, open-label study using an integrated cardiovascular ultrasound approach in patients with newly diagnosed hypertension

BACKGROUND

Increased central aortic pressure resulting from large artery stiffening and increased wave reflection is associated with higher hypertension-related morbidity.

OBJECTIVE

The goal of this study was to evaluate the effects of a vasodilator-based therapy with the calcium channel blocker barnidipine on arterial stiffness, wave reflection, and left ventricular (LV) performance using an integrated cardiovascular ultrasound approach (including wave intensity analysis).

METHODS

Newly diagnosed, previously untreated patients with grade 1 or 2 essential hypertension (systolic blood pressure [BP] > or =140 and <180 mm Hg, and/or diastolic BP > or =90 and <110 mm Hg), and with no signs of clinical cardiovascular disease, were eligible for study. Carotid artery mechanics were investigated at baseline and after 3 and 6 months of barnidipine therapy (10-20 mg once daily, according to an open-label design) using a double-beam carotid ultrasound technique. This provided a simultaneous recording of diameter-derived pressure and flow velocity signals and allowed analysis of wave intensity. Indices of local arterial stiffness and wave reflection, as well as separated forward and backward pressure waves, were estimated. LV geometry, mass, and systolic and diastolic performance were also assessed using Doppler echocardiography. All ultrasound examinations and readings were performed by investigators blinded to patient demographics and treatment phase. Normotensive control subjects (office BP <140/90 mm Hg) were included as a reference group.

RESULTS

Twenty-one white, treatment-naive patients with hypertension (mean [SD] age, 58 [8] years; 14 males; mean body mass index, 27 [5] kg/m(2); mean BP, 159 [14]/96 [5] mm Hg) were enrolled. Twenty normotensive subjects comprised the control group. Compared with the control subjects, patients with hypertension had a higher mean augmentation index ([AIx] 22.0% [7.0%] vs 13.1% [5.2%]; P < 0.01), Peterson's pressure-strain elastic modulus (175 [49] vs 126 [41] kPa; P < 0.01), and forward and backward pressure waves (137 [17] vs 108 [7] mm Hg [P < 0.001] and 21 [6] vs 17 [5] mm Hg [P < 0.05], respectively) at baseline. After 6 months of barnidipine treatment, mean office BP in the patients with hypertension decreased from 159 (14)/96 (5) mm Hg at baseline to 138 (16)/81 (9) mm Hg (P < 0.001) due to a significant reduction in forward and backward pressure waves, and AIx decreased to 17.0% (8.0%) (P < 0.01); there were no significant changes in indices of intrinsic arterial stiffness. A significant direct relationship between AIx and pulse pressure (r = 0.45 [P < 0.05]) was observed at baseline in hypertensive patients but not after therapy (r = 0.26 [P = NS]). Mean stress-adjusted LV midwall shortening increased from 110% (17%) at baseline to 118% (13%) at 6 months (P < 0.05), which was comparable to baseline values in the control subjects (119% [10%]).

CONCLUSION

In these middle-aged patients with newly diagnosed mild to moderate hypertension, vasodilator therapy with barnidipine reduced central BP by a parallel reduction of forward and backward pressure waves, together with a later arrival of the reflected waves, with no significant changes in intrinsic arterial stiffness.

Arterial wave intensity and ventricular-arterial coupling by vascular ultrasound: rationale and methods for the automated analysis of forwards and backwards running waves

Wave intensity (WI) in the circulation is estimated noninvasively as the product of instantaneous changes in pressure and velocity. We recorded diameter as a surrogate for pressure, and velocity in the right common carotid artery using an Aloka SSD-5500 ultrasound scanner. We developed automated software, applying the water hammer equation to obtain local wave speed from the slope of a pressure/velocity loop during early systole to separate net WI into individual forwards and backwards-running waves. A quality index was developed to test for noisy data. The timing, duration, peak amplitude and net energy of separated WI components were measured in healthy subjects with a wide age range. Age and arterial stiffness were independent predictors of local wave speed, whereas backwards-travelling waves correlated more strongly with ventricular systolic function than with age-related changes in arterial stiffness. Separated WI offers detailed insight into ventricular-arterial interactions that may be useful for assessing the relative contributions of ventricular and vascular function to wave travel.

Wave intensity amplification and attenuation in non-linear flow: implications for the calculation of local reflection coefficients

Local reflection coefficients (R) provide important insights into the influence of wave reflection on vascular haemodynamics. Using the relatively new time-domain method of wave intensity analysis, R has been calculated as the ratio of the peak intensities (R(PI)) or areas (R(CI)) of incident and reflected waves, or as the ratio of the changes in pressure caused by these waves (R(DeltaP)). While these methods have not yet been compared, it is likely that elastic non-linearities present in large arteries will lead to changes in the size of waves as they propagate and thus errors in the calculation of R(PI) and R(CI). To test this proposition, R(PI), R(CI) and R(DeltaP) were calculated in a non-linear computer model of a single vessel with various degrees of elastic non-linearity, determined by wave speed and pulse amplitude (DeltaP(+)), and a terminal admittance to produce reflections. Results obtained from this model demonstrated that under linear flow conditions (i.e. as DeltaP(+)-->0), R(DeltaP) is equivalent to the square-root of R(PI) and R(CI) (denoted by R(PI)(p) and R(CI)(p)). However for non-linear flow, pressure-increasing (compression) waves undergo amplification while pressure-reducing (expansion) waves undergo attenuation as they propagate. Consequently, significant errors related to the degree of elastic non-linearity arise in R(PI) and R(CI), and also R(PI)(p) and R(CI)(p), with greater errors associated with larger reflections. Conversely, R(Delta)(P) is unaffected by the degree of non-linearity and is thus more accurate than R(PI) and R(CI).

Pulse wave propagation in a model human arterial network: Assessment of 1-D numerical simulations against in vitro measurements

A numerical model based on the nonlinear, one-dimensional (1-D) equations of pressure and flow wave propagation in conduit arteries is tested against a well-defined experimental 1:1 replica of the human arterial tree. The tree consists of 37 silicone branches representing the largest central systemic arteries in the human, including the aorta, carotid arteries and arteries that perfuse the upper and lower limbs and the main abdominal organs. The set-up is mounted horizontally and connected to a pulsatile pump delivering a periodic output similar to the aortic flow. Terminal branches end in simple resistance models, consisting of stiff capillary tubes leading to an overflow reservoir that reflects a constant venous pressure. The parameters required by the numerical algorithm are directly measured in the in vitro set-up and no data fitting is involved. Comparison of experimental and numerical pressure and flow waveforms shows the ability of the 1-D time-domain formulation to capture the main features of pulse wave propagation measured throughout the system test. As a consequence of the simple resistive boundary conditions used to reduce the uncertainty of the parameters involved in the simulation, the experimental set-up generates waveforms at terminal branches with additional non-physiological oscillations. The frequencies of these oscillations are well captured by the 1-D model, even though amplitudes are overestimated. Adding energy losses in bifurcations and including fluid inertia and compliance to the purely resistive terminal models does not reduce the underdamped effect, suggesting that wall visco-elasticity might play an important role in the experimental results. Nevertheless, average relative root-mean-square errors between simulations and experimental waveforms are smaller than 4% for pressure and 19% for the flow at all 70 locations studied.