Disturbance of macro- and microcirculation: relations with pulse pressure and cardiac organ damage

Cerebral microcirculatory pulse wave propagation and pulse wave amplitude mapping in retrospectively gated MRI

To analyze cerebral arteriovenous pulse propagation and to generate phase-resolved pulse amplitude maps from a fast gradient-echo sequence offering flow-related enhancement (FREE). Brain MRI was performed using a balanced steady-state free precession sequence at 3T followed by retrospective k-space gating. The time interval of the pulse wave between anterior-, middle- and posterior cerebral artery territories and the superior sagittal sinus were calculated and compared between and older and younger groups within 24 healthy volunteers. Pulse amplitude maps were generated and compared to pseudo-Continuous Arterial Spin Labeling (pCASL) MRI maps by voxel-wise Pearson correlation, Sørensen-Dice maps and in regards to signal contrast. The arteriovenous delays between all vascular territories and the superior sagittal sinus were significantly shorter in the older age group (11 individuals, ≥ 31 years) ranging between 169 ± 112 and 246 ± 299 ms versus 286 ± 244 to 419 ± 299 ms in the younger age group (13 individuals) (P ≤ 0.04). The voxel-wise pulse wave amplitude values and perfusion-weighted pCASL values correlated significantly (Pearson-r = 0.33, P < 0.01). Mean Dice overlaps of high (gray) and low (white matter) regions were 73 ± 3% and 59 ± 5%. No differences in image contrast were seen in the whole brain and the white matter, but significantly higher mean contrast of 0.73 ± 0.23% in cortical gray matter in FREE-MRI compared to 0.52 ± 0.12% in pCASL-MRI (P = 0.01). The dynamic information of flow-related enhancement allows analysis of the cerebral pulse wave propagation potentially providing information about the (micro)circulation on a regional level. However, the pulse wave amplitude reveals weaknesses in comparison to true perfusion-weighting and could rather be used to calculate a pulsatility index.

Beat-to-beat finger photoplethysmography in atrial fibrillation patients undergoing electrical cardioversion

Atrial fibrillation (AF)-induced peripheral microcirculatory alterations have poorly been investigated. The present study aims to expand current knowledge through a beat-to-beat analysis of non-invasive finger photoplethysmography (PPG) in AF patients restoring sinus rhythm by electrical cardioversion (ECV). Continuous non-invasive arterial blood pressure and left middle finger PPG pulse oximetry waveform (POW) signals were continuously recorded before and after elective ECV of consecutive AF or atrial flutter (AFL) patients. The main metrics (mean, standard deviation, coefficient of variation), as well as a beat-to-beat analysis of the pulse pressure (PP) and POW beat-averaged value (aPOW), were computed to compare pre- and post-ECV phases. 53 patients (mean age 69 ± 8 years, 79% males) were enrolled; cardioversion was successful in restoring SR in 51 (96%) and signal post-processing was feasible in 46 (87%) patients. In front of a non-significant difference in mean PP (pre-ECV: 51.96 ± 13.25, post-ECV: 49.58 ± 10.41 mmHg; p = 0.45), mean aPOW significantly increased after SR restoration (pre-ECV: 0.39 ± 0.09, post-ECV: 0.44 ± 0.06 a.u.; p < 0.001). Moreover, at beat-to-beat analysis linear regression yielded significantly different slope (m) for the PP (RR) relationship compared to aPOW(RR) [PP(RR): 0.43 ± 0.18; aPOW(RR): 1.06 ± 0.17; p < 0.001]. Long (> 95th percentile) and short (< 5th percentile) RR intervals were significantly more irregular in the pre-ECV phases for both PP and aPOW; however, aPOW signal suffered more fluctuations compared to PP (p < 0.001 in both phases). Present findings suggest that AF-related hemodynamic alterations are more manifest at the peripheral (aPOW) rather than at the upstream macrocirculatory level (PP). Restoring sinus rhythm increases mean peripheral microvascular perfusion and decreases variability of the microvascular hemodynamic signals. Future dedicated studies are required to determine if AF-induced peripheral microvascular alterations might relate to long-term prognostic effects.

Baduanjin exercise in the treatment of hypertension: A systematic review and meta-analysis

Background

As a therapy to prevent and treat hypertension, exercise is widely used in clinical practice. But due to the lack of documentary evidence, Baduanjin as a relaxed and convenient mode of exercise is not currently recommended by professional health organizations to treat hypertension. The purpose of this article is to examine the efficacy of Baduanjin as an antihypertensive exercise therapy.

Methods

Our systematic retrieved of the entire relevant literatures in 12 databases. Finally, 28 eligible trials involving Baduanjin intervention in hypertension were included. After the quality assessment and bias risk assessment of the included trials, we analyzed the blood pressure values before and after the intervention, and performed meta-analysis on the random effect results. In order to explore the factors influencing the decrease of blood pressure, we also performed a subgroup analysis of the results.

Results

Participants (n = 2121) were adults (61.74 ± 5.85years of age, mean ± SD), with baseline blood pressure (systolic blood pressure (SBP) = 150.7 ± 9.2 mmHg, diastolic blood pressure (DBP) = 93.2 ± 8.8 mmHg). Baduanjin was practiced 7.5 ± 3.8 sessions / week for 28.2 ± 12.8 min /session for 16.7 ± 9.2 weeks. Overall, Baduanjin resulted in SBP (−9.3 mmHg, d = −1.49, 95%CI: −1.73 to −1.13) and DBP (−6.3 mmHg, d = −1.20, 95%CI: −1.51 to −0.88) vs. the control group (p &lt; 0.001). After a subgroup analysis of age, we found that SBP heterogeneity was significantly reduced in the elderly group.

Conclusion

Our results indicate that Baduanjin can effectively reduce blood pressure (i.e., 9.3 mmHg and 6.3 mmHg of SBP and DBP reductions, respectively), and reduce the incidence rate of cardiovascular disease in hypertensive patients. In addition, we will be more likely to recommend that the elderly exercise Baduanjin.

The Effect of Blood Flow-Restricted Low Resistance Training on Microvascular Circulation of Myocardium in Spontaneously Hypertensive Rats

Objective: The purpose of this study was to explore the effect of blood flow-restricted low resistance training on microvascular rarefaction in the myocardium of spontaneously hypertensive rats (SHRs).

Methods: Four-week-old male SHRs were randomly divided into the following groups: Wistar-Kyoto (WKY), SHR control (SHR-SED), high-intensity resistance training (HIRT), low-intensity resistance training (LIRT), and blood flow-restricted low resistance training (BFRT). The exercise groups began to receive exercise intervention for 8 weeks at the age of 7 weeks. Blood pressure (BP), heart rate (HR), cardiac function, capillary density, and Vascular endothelial growth factor -Phosphatidylinositol 3-kinase-Protein kinase B-Endothelial nitric oxide synthetase (VEGF-Pi3k-Akt-eNOS) were assessed.

Results: 1) BP and HR of BFRT decreased significantly, Ejection fraction (EF) and Fraction shortening (FS) increased, and the effect of BFRT on lowering BP and HR was better than that of other groups (p < 0.05); 2) The expression of VEGF, VEGFR2, p-VEGFR2, Pi3k, Akt, p-Akt, eNOS and p-eNOS in the myocardium of the BFRT was significantly upregulated, and eNOS expression was significantly higher than other groups (p < 0 05); 3) the expression of VEGF in the blood of the BFRT was significantly upregulated, higher than SHR-SED, lower than HIRT (p < 0.05), and there was no significant difference between BFRT and LIRT(p > 0.05); 4) the capillary density in the myocardium of BFRT was significantly higher than other exercise groups (p < 0 05).

Conclusion: Blood flow-restricted low resistance training can activate the VEGF-Pi3k-Akt-eNOS pathway, upregulate the expression of VEGF in blood, improve microvascular rarefaction, and promote myocardial microvascular circulation, thereby improving cardiac function and lowering blood pressure, achieving the preventive effect of early hypertension.

Serum Fibroblast Growth Factor 21 Level Is Associated with Aortic Stiffness in Patients on Maintenance Hemodialysis

Background. Fibroblast growth factor 21 (FGF-21) is a hormone that regulates glucose and lipid metabolism. High serum FGF-21 levels are associated with carotid atherosclerosis and coronary artery disease. This cross-sectional study aimed to assess the relationship between serum FGF-21 levels and carotid-femoral pulse wave velocity (cfPWV) in patients on maintenance hemodialysis (HD). Methods. Blood samples and baseline characteristics were collected from 130 HD patients. Serum FGF-21 concentrations were measured with an enzyme-linked immunosorbent assay kit. Aortic stiffness was defined as a carotid-femoral pulse wave velocity (cfPWV) of more than 10 m/s. Results. Of the 130 HD patients, aortic stiffness was diagnosed in 54 (41.5%). Serum FGF-21 levels were significantly higher in those with aortic stiffness than those without $\left(P<0.001\right)$ . The FGF-21 level was independently associated with aortic stiffness (odds ratio (OR): 1.008; 95% CI: 1.003–1.012; $P=0.001$ ) after adjusting for diabetes mellitus, age, hypertension, C-reactive protein, and body weight in multivariable logistic regression analysis. Multivariable forward stepwise linear regression analysis also confirmed that the logarithmically transformed FGF-21 level (β = 3.245, 95% CI: 1.593–4.987, $P<0.001$ ) was an independent predictor of cfPWV values. The area under the receiver operating characteristic (ROC) curve predicting aortic stiffness by the serum FGF-21 level was 0.693 (95% CI: 0.606–0.771, $P<0.001$ ). Conclusions. Serum FGF-21 level positively correlates with cfPWV and is also an independent predictor of aortic stiffness in maintenance HD patients.

Pulsatility damping in the microcirculation: Basic pattern and modulating factors

Blood flow pulsatility is an important determinant of macro- and microvascular physiology. Pulsatility is damped largely in the microcirculation, but the characteristics of this damping and the factors that regulate it have not been fully elucidated yet. Applying computational approaches to real microvascular network geometry, we examined the pattern of pulsatility damping and the role of potential damping factors, including pulse frequency, vascular viscous resistance, vascular compliance, viscoelastic behavior of the vessel wall, and wave propagation and reflection. To this end, three full rat mesenteric vascular networks were reconstructed from intravital microscopic recordings, a one-dimensional (1D) model was used to reproduce pulsatile properties within the network, and potential damping factors were examined by sensitivity analysis. Results demonstrate that blood flow pulsatility is predominantly damped at the arteriolar side and remains at a low level at the venular side. Damping was sensitive to pulse frequency, vascular viscous resistance and vascular compliance, whereas viscoelasticity of the vessel wall or wave propagation and reflection contributed little to pulsatility damping. The present results contribute to our understanding of mechanical forces and their regulation in the microcirculation.

Preliminary Findings on the Potential Use of Magnetic Resonance Elastography to Diagnose Lacunar Infarction

PURPOSE

Lacunar infarction is usually diagnosed by conventional technologies, such as CT and diffusion weighted imaging (DWI). To improve the accuracy of diagnosis, neurocognitive screening is still needed. Therefore, additional imaging methods that can assist and provide more accurate and rapid diagnostics are urgently needed. As an initial step towards potentially using MR elastography (MRE) for such diagnostic purposes, we tested the hypothesis that the mechanical properties of tissue in the vicinity of cerebral vasculature change following lacunar infarction in a way that can be quantified using MRE.

PATIENTS AND METHODS

MRE and MR angiography (MRA) images from 51 patients diagnosed with lacunar infarction and 54 healthy volunteers were acquired on a 3T scanner. All diagnoses were confirmed by matching neurocognitive test results to locations of flow obstruction in MRA. ROIs of the cerebral vessels segmented on the MRA images were mapped to the MRE images. Interpolation-based inversion was applied to estimate the regional biomechanical properties of ROIs that included cerebral vessels. The effects of lacunar infarction, sex, and age were analyzed using analysis of covariance (ANOCOVA).

RESULTS

Shear moduli over vessel ROIs were significantly lower for the lacunar infarction group than those of the healthy control group. A positive correlation between modulus over vessel ROIs and age was observed. However, no significant correlation was found between sex and the regional biomechanical properties of the vessel ROIs.

CONCLUSION

Results supported the hypothesis and suggest that biomechanical properties may be of utility in diagnosis of lacunar infarction.

Hemodynamics Challenges for the Navigation of Medical Microbots for the Treatment of CVDs

Microbots have been considered powerful tools in minimally invasive medicine. In the last few years, the topic has been highly studied by researchers across the globe to further develop the capabilities of microbots in medicine. One of many applications of these devices is performing surgical procedures inside the human circulatory system. It is expected that these microdevices traveling along the microvascular system can remove clots, deliver drugs, or even look for specific cells or regions to diagnose and treat. Although many studies have been published about this subject, the experimental influence of microbot morphology in hemodynamics of specific sites of the human circulatory system is yet to be explored. There are numerical studies already considering some of human physiological conditions, however, experimental validation is vital and demands further investigations. The roles of specific hemodynamic variables, the non-Newtonian behavior of blood and its particulate nature at small scales, the flow disturbances caused by the heart cycle, and the anatomy of certain arteries (i.e., bifurcations and tortuosity of vessels of some regions) in the determination of the dynamic performance of microbots are of paramount importance. This paper presents a critical analysis of the state-of-the-art literature related to pulsatile blood flow around microbots.

l-Theanine Protects Bladder Function by Suppressing Chronic Sympathetic Hyperactivity in Spontaneously Hypertensive Rat

Chronic sympathetic hyperactivity is known to affect metabolism and cause various organ damage including bladder dysfunction. In this study, we evaluated whether l-theanine, a major amino acid found in green tea, ameliorates bladder dysfunction induced by chronic sympathetic hyperactivity as a dietary component for daily consumption. Spontaneously hypertensive rats (SHRs), as an animal model of bladder dysfunction, were divided into SHR-water and SHR-theanine groups. After 6 weeks of oral administration, the sympathetic nervous system, bladder function, and oxidative stress of bladder tissue were evaluated. The mean blood pressure, serum noradrenaline level, and media-to-lumen ratio of small arteries in the suburothelium were significantly lower in the SHR-theanine than in the SHR-water group. Micturition interval was significantly longer, and bladder capacity was significantly higher in the SHR-theanine than in the SHR-water group. Bladder strip contractility was also higher in the SHR-theanine than in the SHR-water group. Western blotting of bladder showed that expression of malondialdehyde was significantly lower in the SHR-theanine than in the SHR-water group. These results suggested that orally administered l-theanine may contribute at least partly to the prevention of bladder dysfunctions by inhibiting chronic sympathetic hyperactivity and protecting bladder contractility.

Neurohormones, inflammatory mediators, and cardiovascular injury in the setting of heart failure

Neurohormones and inflammatory mediators have effects in both the heart and the peripheral vasculature. In patients with heart failure (HF), neurohormonal activation and increased levels of inflammatory mediators promote ventricular remodeling and development of HF, as well as vascular dysfunction and arterial stiffness. These processes may lead to a vicious cycle, whereby arterial stiffness perpetuates further ventricular remodeling leading to exacerbation of symptoms. Although significant advances have been made in the treatment of HF, currently available treatment strategies slow, but do not halt, this cycle. The current treatment for HF patients involves the inhibition of neurohormonal activation, which can reduce morbidity and mortality related to this condition. Beyond benefits associated with neurohormonal blockade, other strategies have focused on inhibition of inflammatory pathways implicated in the pathogenesis of HF. Unfortunately, attempts to target inflammation have not yet been successful to improve prognosis of HF. Further work is required to interrupt key maladaptive mechanisms involved in disease progression.

Low muscle strength and increased arterial stiffness go hand in hand

Low handgrip strength and increased arterial stiffness are both associated with poor health outcomes, but evidence on the relationship between handgrip strength and arterial stiffness is limited. In this cross-sectional analysis of combined baseline datasets from the LipidCardio and Berlin Aging Study II cohorts we aimed to examine whether handgrip strength (HGS) is associated with arterial stiffness. 1511 participants with a median age of 68.56 (IQR 63.13–73.08) years were included. Arterial stiffness was assessed by aortal pulse wave velocity (PWV) with the Mobil-O-Graph device. Handgrip strength was assessed with a handheld dynamometer.

The mean HGS was 39.05 ± 9.07 kg in men and 26.20 ± 7.47 kg in women. According to multivariable linear regression analysis per 5 kg decrease in handgrip strength there was a mean increase in PWV of 0.08 m/s after adjustment for the confounders age, sex, coronary artery disease, systolic blood pressure, body mass index, cohort, and smoking. Thus, there was evidence that low handgrip strength and increased arterial stiffness go hand in hand. Arterial stiffness can possibly create the missing link between low handgrip strength and increased cardiovascular morbidity and mortality. Causality and direction of causality remain to be determined.

Pulse Wave Analysis and Pulse Wave Velocity for Fistula Assessment

BACKGROUND/AIMS

Pulse wave analysis (PWA) and pulse wave velocity (PWV) provide information about arterial stiffness and elasticity, which is mainly used for cardiovascular risk stratification. In the presented prospective observational pilot study, we examined the hypothesis that radiocephalic fistula (RCF)-related changes of haemodynamics and blood vessel morphology including high as well as low flow can be seen in specific changes of pulse wave (PW) morphology.

METHODS

Fifty-six patients with RCF underwent local ambilateral peripheral PWA and PWV measurement with the SphygmoCor® device. Given that the output parameters of the SphygmoCor® are not relevant for the study objectives, we defined new suitable parameters for PWA in direct proximity to fistulas and established an appropriate analysing algorithm. Duplex sonography served as reference method.

RESULTS

Marked changes of peripheral PW morphology when considering interarm differences of slope and areas between the fistula and non-fistula arms were observed in the Arteria radialis, A. brachialis and arterialized Vena cephalica. The sum of the slope differences was found to correlate with an increased flow, while in patients with fistula failure no changes in PW morphology were seen. Moreover, PWV was significantly reduced in the fistula arm.

CONCLUSION

Beside duplex sonography, ambilateral peripheral PWA and PWV measurements are potential new clinical applications to characterize and monitor RCF function, especially in terms of high and low flow.

Arterial Stiffness in Hypertension and Function of Large Arteries

BACKGROUND

Arterial stiffness-typically assessed from non-invasive measurement of pulse wave velocity along a straight portion of the vascular tree between the right common carotid and femoral arteries-is a reliable predictor of cardiovascular risk in patients with essential hypertension.

METHODS

We reviewed how carotid-femoral pulse wave velocity increases with age and is significantly higher in hypertension (than in age- and gender-matched individuals without hypertension), particularly when hypertension is associated with diabetes mellitus.

RESULTS

From the elastic aorta to the muscular peripheral arteries of young healthy individuals, there is a gradual but significant increase in stiffness, with a specific gradient. This moderates the transmission of pulsatile pressure towards the periphery, thus protecting the microcirculatory network. The heterogeneity of stiffness between the elastic and muscular arteries causes the gradient to disappear or be inversed with aging, particularly in long-standing hypertension.

CONCLUSIONS

In hypertension therefore, pulsatile pressure transmission to the microcirculation is augmented, increasing the potential risk of damage to the brain, the heart, and the kidney. Furthermore, elevated pulse pressure exacerbates end-stage renal disease, particularly in older hypertensive individuals. With increasing age, the elastin content of vessel walls declines throughout the arterial network, and arterial stiffening increases further due to the presence of rigid wall material such as collagen, but also fibronectin, proteoglycans, and vascular calcification. Certain genes, mainly related to angiotensin and/or aldosterone, affect this aging process and contribute to the extent of arterial stiffness, which can independently affect both forward and reflected pressure waves.

Waveform analysis of human retinal and choroidal blood flow with laser Doppler holography

Laser Doppler holography was introduced as a full-field imaging technique to measure blood flow in the retina and choroid with an as yet unrivaled temporal resolution. We here investigate separating the different contributions to the power Doppler signal in order to isolate the flow waveforms of vessels in the posterior pole of the human eye. Distinct flow behaviors are found in retinal arteries and veins with seemingly interrelated waveforms. We demonstrate a full field mapping of the local resistivity index, and the possibility to perform unambiguous identification of retinal arteries and veins on the basis of their systolodiastolic variations. Finally we investigate the arterial flow waveforms in the retina and choroid and find synchronous and similar waveforms, although with a lower pulsatility in choroidal arteries. This work demonstrates the potential held by laser Doppler holography to study ocular hemodynamics in healthy and diseased eyes.

Small Artery Elastin Distribution and Architecture-Focus on Three Dimensional Organization

The distribution of ECM proteins within the walls of resistance vessels is complex both in variety of proteins and structural arrangement. In particular, elastin exists as discrete fibers varying in orientation across the adventitia and media as well as often resembling a sheet-like structure in the case of the IEL. Adding to the complexity is the tissue heterogeneity that exists in these structural arrangements. For example, small intracranial cerebral arteries lack adventitial elastin while similar sized arteries from skeletal muscle and intestinal mesentery exhibit a complex adventitial network of elastin fibers. With regard to the IEL, several vascular beds exhibit an elastin sheet with punctate holes/fenestrae while in others the IEL is discontinuous and fibrous in appearance. Importantly, these structural patterns likely sub-serve specific functional properties, including mechanosensing, control of external forces, mechanical properties of the vascular wall, cellular positioning, and communication between cells. Of further significance, these processes are altered in vascular disorders such as hypertension and diabetes mellitus where there is modification of ECM. This brief report focuses on the three-dimensional wall structure of small arteries and considers possible implications with regard to mechanosensing under physiological and pathophysiological conditions.

Arterial stiffness as a risk factor for clinical hypertension

In patients with uncomplicated essential hypertension, cardiac output remains within normal ranges and intravascular volume is normal or low, assuming the presence of a sufficient Windkessel effect and usual resistance and compliance calculations. However, mean circulatory pressure is elevated in these patients. In addition, vascular resistance is augmented, and most importantly, the viscoelasticity of the cardiovascular system is substantially impaired. Such considerations are essential to understanding the mechanisms behind carotid-femoral arterial stiffness, a major risk factor in individuals with hypertension. Arterial stiffness, measured from pulse wave velocity, is substantially increased in hypertension even independently of blood pressure levels. Structural vascular changes and endothelial dysfunction are consistently associated with vessel impairments in animal models of hypertension. Increased arterial stiffness has a major effect on pulse pressure (the difference between systolic and diastolic blood pressure), wave reflections, kidney function, and above all, cardiovascular risk. This increased cardiovascular risk is particularly deleterious in patients with hypertension and/or type 2 diabetes mellitus, who are at risk of both renal and cardiovascular events. In this Review, we discuss the importance of arterial stiffness in the diagnosis and management of hypertension and the need for new approaches for the treatment of hypertension in patients with or without diabetes and/or renal impairment.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.

Diagnostic and therapeutic problems of isolated systolic hypertension

Prevalence of isolated systolic hypertension increases with age, due to progressive elevation of SBP, and is a major risk factor for cardiovascular morbidity and mortality. Extensive research has shown that lowering SBP improves cardiovascular outcomes in patients with isolated systolic hypertension, yet SBP control rates remain largely inadequate regardless of antihypertensive treatment. Arterial stiffness is a major determinant of elevated SBP resulting from structural changes in the vascular system, mediated by neurohormonal alterations that occur with vascular ageing. Clinical data have demonstrated an independent association between arterial stiffness and cardiovascular outcomes. Therefore, arterial stiffness has the potential to be an important therapeutic target in the management of isolated systolic hypertension. Current antihypertensive treatments have limited effects on arterial stiffness, so the development of new treatments addressing neurohormonal alterations central to vascular ageing is important. Such therapies may represent effective strategies in the future management of SBP.

"Smooth Muscle Cell Stiffness Syndrome"-Revisiting the Structural Basis of Arterial Stiffness

In recent decades, the pervasiveness of increased arterial stiffness in patients with cardiovascular disease has become increasingly apparent. Though, this phenomenon has been well documented in humans and animal models of disease for well over a century, there has been surprisingly limited development in a deeper mechanistic understanding of arterial stiffness. Much of the historical literature has focused on changes in extracellular matrix proteins—collagen and elastin. However, extracellular matrix changes alone appear insufficient to consistently account for observed changes in vascular stiffness, which we observed in our studies of aortic stiffness in aging monkeys. This led us to examine novel mechanisms operating at the level of the vascular smooth muscle cell (VSMC)—that include increased cell stiffness and adhesion to extracellular matrix—which that may be interrelated with other mechanisms contributing to arterial stiffness. We introduce these observations as a new concept—the Smooth Muscle Cell Stiffness Syndrome (SMCSS)—within the field of arterial stiffness and posit that stiffening of vascular cells impairs vascular function and may contribute stiffening to the vasculature with aging and cardiovascular disease. Importantly, this review article revisits the structural basis of arterial stiffness in light of these novel findings. Such classification of SMCSS and its contextualization into our current understanding of vascular mechanics may be useful in the development of strategic therapeutics to directly target arterial stiffness.

Assessing intracranial vascular compliance using dynamic arterial spin labeling

Vascular compliance (VC) is an important marker for a number of cardiovascular diseases and dementia, which is typically assessed in the central and peripheral arteries indirectly by quantifying pulse wave velocity (PWV), and/or pulse pressure waveform. To date, very few methods are available for the quantification of intracranial VC. In the present study, a novel MRI technique for in-vivo assessment of intracranial VC was introduced, where dynamic arterial spin labeling (ASL) scans were synchronized with the systolic and diastolic phases of the cardiac cycle. VC is defined as the ratio of change in arterial cerebral blood volume (ΔCBV) and change in arterial pressure (ΔBP). Intracranial VC was assessed in different vascular components using the proposed dynamic ASL method. Our results show that VC mainly occurs in large arteries, and gradually decreases in small arteries and arterioles. The comparison of intracranial VC between young and elderly subjects shows that aging is accompanied by a reduction of intracranial VC, in good agreement with the literature. Furthermore, a positive association between intracranial VC and cerebral perfusion measured using pseudo-continuous ASL with 3D GRASE MRI was observed independent of aging effects, suggesting loss of VC is associated with a decline in perfusion. Finally, a significant positive correlation between intracranial and central (aortic arch) VC was observed using an ungated phase-contrast 1D projection PWV technique. The proposed dynamic ASL method offers a promising approach for assessing intracranial VC in a range of cardiovascular diseases and dementia.

Genetic determinants of arterial stiffness

Stiffness of large arteries (called arteriosclerosis) is an independent predictor of cardiovascular morbidity and mortality. Although previous studies have shown that arterial stiffness is moderately heritable, genetic factors contributing to arterial stiffness are largely unknown. In this paper, we reviewed the available literature on genetic variants that are potentially related to arterial stiffness. Most variants have shown mixed depictions of their association with arterial stiffness across multiple studies. Various methods to measure arterial stiffness at different arterial sites can contribute to these inconsistent results. In addition, studies in patient populations with hypertension or atherosclerosis may overestimate the impact of genetic variants on arterial stiffness. Future studies are recommended to standardize current measures of arterial stiffness in different age groups. Studies conducted in normal healthy subjects may also provide better opportunities to find novel genetic variants of arterial stiffness.

Fundus photography as a convenient tool to study microvascular responses to cardiovascular disease risk factors in epidemiological studies

The microcirculation consists of blood vessels with diameters less than 150 µm. It makes up a large part of the circulatory system and plays an important role in maintaining cardiovascular health. The retina is a tissue that lines the interior of the eye and it is the only tissue that allows for a non-invasive analysis of the microvasculature. Nowadays, high-quality fundus images can be acquired using digital cameras. Retinal images can be collected in 5 min or less, even without dilatation of the pupils. This unobtrusive and fast procedure for visualizing the microcirculation is attractive to apply in epidemiological studies and to monitor cardiovascular health from early age up to old age. Systemic diseases that affect the circulation can result in progressive morphological changes in the retinal vasculature. For example, changes in the vessel calibers of retinal arteries and veins have been associated with hypertension, atherosclerosis, and increased risk of stroke and myocardial infarction. The vessel widths are derived using image analysis software and the width of the six largest arteries and veins are summarized in the Central Retinal Arteriolar Equivalent (CRAE) and the Central Retinal Venular Equivalent (CRVE). The latter features have been shown useful to study the impact of modifiable lifestyle and environmental cardiovascular disease risk factors. The procedures to acquire fundus images and the analysis steps to obtain CRAE and CRVE are described. Coefficients of variation of repeated measures of CRAE and CRVE are less than 2% and within-rater reliability is very high. Using a panel study, the rapid response of the retinal vessel calibers to short-term changes in particulate air pollution, a known risk factor for cardiovascular mortality and morbidity, is reported. In conclusion, retinal imaging is proposed as a convenient and instrumental tool for epidemiological studies to study microvascular responses to cardiovascular disease risk factors.

A one-dimensional mathematical model for studying the pulsatile flow in microvascular networks

Techniques that model microvascular hemodynamics have been developed for decades. While the physiological significance of pressure pulsatility is acknowledged, most of the microcirculatory models use steady flow approaches. To theoretically study the extent and transmission of pulsatility in microcirculation, dynamic models need to be developed. In this paper, we present a one-dimensional model to describe the dynamic behavior of microvascular blood flow. The model is applied to a microvascular network from a rat mesentery. Intravital microscopy was used to record the morphology and flow velocities in individual vessel segments, and boundaries are defined according to the experimental data. The system of governing equations constituting the model is solved numerically using the discontinuous Galerkin method. An implicit integration scheme is adopted to increase computing efficiency. The model allows the simulation of the dynamic properties of blood flow in microcirculatory networks, including the pressure pulsatility (quantified by a pulsatility index) and pulse wave velocity (PWV). From the main input arteriole to the main output venule, the pulsatility index decreases by 66.7%. PWV obtained along arterioles declines with decreasing diameters, with mean values of 77.16, 25.31, and 8.30 cm/s for diameters of 26.84, 17.46, and 13.33 μm, respectively. These results suggest that the 1D model developed is able to simulate the characteristics of pressure pulsatility and wave propagation in complex microvascular networks.

Opposite Predictive Value of Pulse Pressure and Aortic Pulse Wave Velocity on Heart Failure With Reduced Left Ventricular Ejection Fraction

Although hypertension contributes significantly to worsen cardiovascular risk, blood pressure increment in subjects with heart failure is paradoxically associated with lower risk. The objective was to determine whether pulse pressure and pulse wave velocity (PWV) remain prognostic markers, independent of treatment in heart failure with reduced left ventricular function. The investigation involved 6632 patients of the Eplerenone Post–Acute Myocardial Infarction Heart Failure Efficacy and Survival Study. All subjects had acute myocardial infarction with left ventricular ejection fraction <40% and signs/symptoms of heart failure. Carotid-femoral PWV was measured in a subpopulation of 306 subjects. In the overall population, baseline mean arterial pressure <90 mm Hg was associated with higher all-cause death (hazard ratio, 1.14 [95% confidence interval, 1.00–1.30]; P <0.05), whereas higher left ventricular ejection fraction or pulse pressure was associated with lower rates of all-cause death, cardiovascular death/hospitalization, and cardiovascular death. In the subpopulation, increased baseline PWV was associated with worse outcomes (all-cause death: 1.16 [1.03–1.30]; P <0.05 and cardiovascular deaths: 1.16 [1.03–1.31]; P <0.05), independent of age and left ventricular ejection fraction. Using multiple regression analysis, systolic blood pressure and age were the main independent factors positively associated with pulse pressure or PWV, both in the entire population or in the PWV substudy. In heart failure and low ejection fraction, our results suggest that pulse pressure, being negatively associated with outcome, is more dependent on left ventricular function and thereby no longer a marker of aortic elasticity. In contrast, increased aortic stiffness, assessed by PWV, contributes significantly to cardiovascular death.

Decreased stroke volume−brachial pulse pressure ratio in patients with type 2 diabetes over 50 years: the role of peripheral neuropathy

BACKGROUND AND AIMS

To document the stroke volume to pulse pressure ratio (SV/PP, an index of total arterial compliance) and its correlates in patients with type 2 diabetes (T2DM) aged over 50 years whose peripheral neuropathy and silent myocardial ischemic (SMI) status were known.

METHODS AND RESULTS

A total of 360 patients with T2DM aged ≥ 50 years, without cardiac history or symptom, left ventricular systolic dysfunction, dilatation and hypokinesia, were retrospectively enrolled. The SV/PP was calculated from echocardiographic left ventricular measurements and brachial blood pressure at rest. Peripheral neuropathy was defined as the presence of any two or more of the following: neuropathic symptoms, decreased distal sensation, or decreased or absent ankle reflexes. SMI was defined as an abnormal stress myocardial scintigraphy and/or stress echocardiography. A low SV/PP ratio (<0.53 ml/m²/mmHg, first tertile) was associated with age, creatinine clearance, 24 h urinary albumin excretion rate, peripheral neuropathy, hypertension, serum total cholesterol and triglycerides levels (p < 0.05-0.0001). In multivariate analysis, age (OR 1.1 [1.0-1.2], p < 0.01), triglycerides (OR 1.5 [1.2-2.0], p = 0.01) and peripheral neuropathy (OR 2.2 [1.2-3.9], p = 0.009) were independently associated with a low SV/PP. The patients with peripheral neuropathy had lower SV (p < 0.01) and higher PP (p < 0.05) than those without, and only lower SV after adjustment for age and nephropathy. Similar results were obtained in the patients with and without SMI.

CONCLUSION

Peripheral neuropathy was independently associated with decreased SV/PP, mainly through decreased SV, in patients with T2DM over 50 years.

AORTIC STIFFNESS ASSESSMENT IN PATIENTS WITH ARTERIAL HYPERTENSION AND OBESITY

Cardiovascular disease (CVD) remains the leading cause of death in most developed countries. Morphological and functional status of large arteries plays an important role in the pathogenesis of CVD. At the moment, there are two main methods of aortic stiffness assessment: pulse wave velocity (PWV) measurement and central PW analysis. In advanced age, aortic stiffness increases, which manifests in increased PWV, elevated central blood pressure, and increased parameters of reflected PW. Similar changes can be observed in young patients with arterial hypertension. The existing evidence concerning obesity effects on aortic stiffness is contradictory and warrants further clarification. 

Interaction between chromosome 2 and 3 regulates pulse pressure in the stroke-prone spontaneously hypertensive rat

In an F2 cross between stroke-prone spontaneously hypertensive (SHRSP) and Wistar Kyoto (WKY) rats, we previously identified blood pressure quantitative trait loci (QTL) on rat chromosome (RNO) 2 and a pulse pressure QTL on RNO3. The aims of this study were to confirm the QTL on RNO3 and to investigate interaction between RNO2 and RNO3 loci through the generation and phenotypic assessment of single RNO3 congenic (SP.WKY(Gla)3a) and bicongenic (SP.WKY(Gla)2a/3a) strains. Hemodynamic profiling, vascular function, and renal histology were examined in these newly generated strains along with the previously reported RNO2 congenic strain (SP.WKY(Gla)2a). Our results demonstrate significant equivalent reduction in systolic, diastolic, and pulse pressure phenotypes in SP.WKY(Gla)3a and SP.WKY(Gla)2a rats, whereas greater reductions were observed with the SP.WKY(Gla)2a/3a bicongenic strain achieving blood pressure levels similar to normotensive WKY rats. Epistasis was observed between pulse pressure QTL on RNO2 and 3 at baseline and during 1% salt challenge. Vascular function and renal pathology studies indicate that QTL on RNO3 are responsible for salt-induced kidney pathology, whereas QTL on RNO2 seem to have greater impact on vascular function. RNO3 congenic and bicongenic strains have confirmed the importance of SHRSP alleles in the RNO3 congenic interval on pulse pressure variability and end-organ damage. These strains will allow interrogation of complex gene-gene and gene-environment interactions contributing to salt-sensitive hypertension and renal pathology in the SHRSP rat.

Aortic pulse wave velocity predicts focal white matter hyperintensities in a biracial cohort of older adults

Although the cross-sectional relationship of arterial stiffness with cerebral small vessel disease is consistently shown in middle-aged and young-old adults, it is less clear whether these associations remain significant over time in very old adults. We hypothesize that arterial stiffness is longitudinally associated with white matter characteristics, and associations are stronger within watershed areas. Neuroimaging was obtained in 2006-2008 from 303 elderly (mean age 82.9 years, 59% women, 41% black) with pulse wave velocity (PWV) measures in 1997-1998. Multivariable regression models estimated the coefficients for PWV (cm/sec) in relationship to presence, severity, and spatial distribution of white matter hyperintensities (WMH), gray matter volume, and fractional anisotropy from diffusion tensor, adjusting for demographic, cardiovascular risk factors, and diseases from 1997-1998 to 2006-2008. Higher PWV in 1997-1998 was associated with greater WMH volume in 2006-2008 within the left superior longitudinal fasciculus (age and total brain WMH adjusted, P=0.023), but not with WMH in other tracts or with fractional anisotropy or gray matter volume from total brain (P>0.2). Associations were stronger in blacks than in whites, remaining significant in fully adjusted models. Elderly with WMH in tracts related to processing speed and memory are more likely to have had higher PWV values 10 years prior, before neuroimaging data being available. Future studies should address whether arterial stiffness can serve as an early biomarker of covert brain structural abnormalities and whether early arterial stiffness control can promote successful brain aging, especially in black elderly.

Factors affecting ocular pulse amplitude in eyes with open angle glaucoma and glaucoma-suspect eyes

PURPOSE

To investigate the associations between ocular pulse amplitude (OPA) as measured by dynamic contour tonometry (DCT) and ocular and systemic factors in patients with open angle glaucoma (OAG) and in glaucoma suspects.

METHODS

One hundred and seventy-three glaucoma-suspect patients were consecutively enrolled. All subjects underwent intraocular pressure (IOP) measurement by DCT and Goldmann applanation tonometry (GAT), OPA measurement by DCT, Humphrey visual field (HVF) examination and central corneal thickness measurements. Arterial pulse amplitude (APA) and ocular perfusion pressure (OPP) were defined as the difference between systolic and diastolic BP and the difference between mean arterial pressure and IOP, respectively. All subjects also completed a systemized questionnaire on systemic vascular morbidities.

RESULTS

Seventy-four eyes were diagnosed with OAG, based on HVF results. The overall mean CCT was 538.2±37.6 μm. In all 173 eyes, OPA was associated with spherical equivalent (SE, p<0.001) and with IOP by GAT (p=0.013) by multivariate analysis. Multivariate analysis of the 77 subgroup eyes of patients for whom BP parameters were available also revealed that OPA was associated with SE (p=0.007) and with IOP by GAT (p<0.001). When the subjects were classified into the groups with low, intermediate and high cardiovascular risk based on the questionnaire, there was no difference in OPA among these groups (p>0.05).

CONCLUSIONS

Ocular pulse amplitude was associated with IOP measured by GAT and SE in patients with OAG and in glaucoma suspects. There was neither significant correlation between systemic hemodynamic parameters and OPA, nor difference of OPA in patients with different cardiovascular risk. OPA is primarily a measure of pressure, and there are certain limitations towards its use as a hemodynamic index.

Acupuncture Effects on the Pulse Spectrum of Radial Pressure Pulse in Dyspepsia

This study is to investigate the influences of acupuncture for dyspepsia on the Radial Pressure Pulse (RPP) between the Chun, Guan and Chy positions of the right/left wrist. Two series of experiments were designed; for the first series, 30 patients with dyspepsia (Group P) and 30 normal subjects (Group N) were seated to undergo the measurements of pulse pressure waveforms from radial artery by sphygmograph. The parameters of RPP included the spectral energy of 0–10 Hz (SE0–10Hz), 10–50 Hz (SE10–50Hz) and 13–50 Hz (SE13–50Hz). For the second series, acupuncture was administered at the right and left Tsu San Li (St-36) points for the same 30 dyspepsia patients, and then their pulse pressure waveforms were re-examined. The results showed that the SE0–10Hz at Right Guan (RB) (p < 0.05), the SE10–50Hz at RB (p < 0.01), and the SE13–50Hz at RB (p < 0.01) and Left Guan (LB) (p < 0.05) of Group P were significantly greater than that of Group N. After the acupuncture, there were significant decreases in the SE0–10Hz only at RB (p < 0.01), in the SE10–50Hz at RB (p < 0.01), Right Chy (RC) (p < 0.05) and LB (p < 0.05), and in the SE13–50Hz RB (p < 0.01), RC (p < 0.05) and LB (p < 0.01). We concluded that the pulse-frequency spectrum at RB was a more effective characteristic for dyspepsia patients, and the acupuncture had an effect on SE10–50Hz and SE13–50Hz more obviously than that on SE0–10Hz.

A new flow co-culture system for studying mechanobiology effects of pulse flow waves

Artery stiffening is known as an important pathological change that precedes small vessel dysfunction, but underlying cellular mechanisms are still elusive. This paper reports the development of a flow co-culture system that imposes a range of arterial-like pulse flow waves, with similar mean flow rate but varied pulsatility controlled by upstream stiffness, onto a 3-D endothelial-smooth muscle cell co-culture. Computational fluid dynamics results identified a uniform flow area critical for cell mechanobiology studies. For validation, experimentally measured flow profiles were compared to computationally simulated flow profiles, which revealed percentage difference in the maximum flow to be <10, <5, or <1% for a high, medium, or low pulse flow wave, respectively. This comparison indicated that the computational model accurately demonstrated experimental conditions. The results from endothelial expression of proinflammatory genes and from determination of proliferating smooth muscle cell percentage both showed that cell activities did not vary within the identified uniform flow region, but were upregulated by high pulse flow compared to steady flow. The flow system developed and characterized here provides an important tool to enhance the understanding of vascular cell remodeling under flow environments regulated by stiffening.

Application of Sphygmography to Detection of Dyspepsia and the Rhinitis

Diagnosis by radial arterial pulse is very important in Traditional Chinese Medicine (TCM). The objective of this study is to evaluate the effects of detection time and position on the parameters of time- and frequency-domain of radial pulse wave and to differentiate between Dyspepsia and Rhinitis by the statistical analysis of two signal types. A sphygmograph was developed to record radial pressure pulse for spectral analysis. The measurements were expressed as the pressure wave and its frequency. In this study, 135 subjects including the controls, Dyspepsias and Rhinitis were enrolled in this study. The signals were taken from three diagnosis positions of both wrists. Seven parameters of pressure wave and two parameters of spectrum analysis were evaluated by ANOVA test and Tukey's test. The results showed that the effects of detection time and position on the parameters taken from pulse wave were inconsistent. No regular rules or relationship could be established. The power spectra of 10–50 Hz and 13–50 Hz from sphygmography revealed a significant effect of health status, position and their interaction. There was a significant difference in the power spectra of 13–50 Hz between the control and Rhinitis, as well as between the control and Dyspepsia at right Guan position. The results of this study strongly suggest that the spectrum of sphygmogram might be more helpful than the pressure wave signals for detection of Dyspepsia and Rhinitis.

Vascular dysfunction as target organ damage in animal models of hypertension

Endothelial dysfunction is one of the main characteristics of chronic hypertension and it is characterized by impaired nitric oxide (NO) bioactivity determined by increased levels of reactive oxygen species. Endothelial function is usually evaluated by measuring the vasodilation induced by the local NO production stimulated by external mechanical or pharmacological agent. These vascular reactivity tests may be carried out in different models of experimental hypertension such as NO-deficient rats, spontaneously hypertensive rats, salt-sensitive rats, and many others. Wire myograph and pressurized myograph are the principal methods used for vascular studies. Usually, increasing concentrations of the vasodilator acetylcholine are added in cumulative manner to perform endothelium-dependent concentration-response curves. Analysis of vascular mechanics is relevant to identify arterial stiffness. Both endothelial dysfunction and vascular stiffness have been shown to be associated with increased cardiovascular risk.

Microvascular brain damage with aging and hypertension: pathophysiological consideration and clinical implications

Loss of cognitive function and hypertension are two common conditions in the elderly and both significantly contribute to loss of personal independency. Microvascular brain damage - the result of age-associated alteration in large arteries and the progressive mismatch of their cross-talk with small cerebral arteries - represents a potent risk factor for cognitive decline and for the onset of dementia in older individuals. The present review discusses the complexity of factors linking large artery to microvascular brain disease and to cognitive decline and the evidence for possible clinical markers useful for prevention of this phenomenon. The possibility of dementia prevention by cardiovascular risk factors control has not been demonstrated. In the absence of research clinical trials specifically and primarily designed to demonstrate the antihypertensive treatment efficacy for reducing the risk of dementia, further evidence demonstrating that it is possible to limit the progression of microvascular brain damage is needed.

Dynamic evaluation of renal resistive index in normoalbuminuric patients with newly diagnosed hypertension or type 2 diabetes

AIM/HYPOTHESIS

Renal resistive index is a useful measure for quantifying alterations in renal blood flow. In the present study we evaluated resistive index at baseline and after vasodilation induced by nitroglycerine in normoalbuminuric patients with type 2 diabetes or essential hypertension, relating the values to indices of systemic vascular dysfunction.

METHODS

Newly diagnosed treatment-naïve type 2 diabetic (n = 32) and hypertensive patients (n = 49) were compared with 27 age- and sex-matched healthy controls. Renal resistive index was obtained by duplex ultrasound at baseline and after 25 μg sublingual nitroglycerine. Endothelium-dependent (flow-mediated dilation) and -independent (response to nitroglycerine) vasodilation in the brachial artery was assessed by computerised edge detection system. Carotid-femoral pulse-wave velocity and augmentation index were assessed by applanation tonometry. Nitrotyrosine levels, an index of oxidative stress, were also measured.

RESULTS

Resistive index was higher in diabetic than in hypertensive patients and controls (p < 0.001), while changes in resistive index induced by nitroglycerine were lower in hypertensive patients compared with controls (p < 0.01), and were further reduced in type 2 diabetic patients. Hypertensive and diabetic patients showed significantly increased arterial stiffness, nitrotyrosine levels and reduced endothelial function than controls (p < 0.05). Changes in resistive index induced by nitroglycerine were independently related to serum glucose, reactive hyperaemia and aortic pulse-wave velocity in the overall population.

CONCLUSIONS/INTERPRETATION

These results support the dynamic evaluation of renal resistive index as an early detector of renal vascular alterations in the presence of type 2 diabetes and hypertension, even before the onset of microalbuminuria.

Peripheral and central augmentation indexes in relation to the CYP4F2 polymorphisms in Chinese

OBJECTIVE

Cytochrome (CYP) 4F2 isoform is a key metabolizing enzyme for the renal 20-hydroxyeicosatetraenoic acid (20-HETE), which, as an endogenous vasoconstrictor, may influence properties of the peripheral muscular arteries and arterioles. We, therefore, investigated the CYP4F2 polymorphisms in relation to arterial wave reflections, as measured by augmentation indexes (AIx) in Chinese.

METHODS

We performed arterial measurements by SphygmoCor and genotyped three CYP4F2 polymorphisms (V433M, rs3093089, and rs3093098) by PCR-restriction fragment length polymorphism in 1421 participants enrolled in the JingNing Population study. A replication study for the V433M polymorphism was performed in 924 Chinese recruited from a workplace setting. Urinary 20-HETE concentration was determined by ELISA in a randomly selected subsample of 318 JingNing individuals.

RESULTS

In spite of the fact that genetic associations were not significant (P ≥ 0.12) in all JingNing participants, there was significant (Pint ≤ 0.02) interaction of the V433M polymorphism with sex and pulse rate in relation to peripheral and central AIx. M433 allele carriers, compared with V433V homozygotes, had significantly greater peripheral (+5.0%, P = 0.0002) and central AIx (+3.2%, P = 0.001) in 693 men. The corresponding values were +2.7% (P = 0.04) and +1.9% (P = 0.04) in 490 individuals of the top tertile of pulse rate (≥ 76 beats/min), and were +4.0% (P = 0.02) and +3.3% (P = 0.02) in 315 replication participants with a pulse rate at least 76 beats/min. Urinary 20-HETE concentration was significantly higher (P = 0.002) in M433M (2.06 ng/ml) and V433M (1.13 ng/ml) individuals than in V433V homozygotes (0.98 ng/ml).

CONCLUSION

The CYP4F2 V433M polymorphism is associated with the size of arterial wave reflections in male Chinese, or individuals with a faster pulse rate.

Ocular blood flow analysis detects microvascular abnormalities in impaired glucose tolerance

OBJECTIVE

Waveform analysis has been used to assess vascular resistance and predict cardiovascular events. We aimed to identify microvascular abnormalities in patients with IGT using ocular waveform analysis. The effects of pioglitazone were also assessed.

METHODS

Forty patients with IGT and 24 controls were studied. Doppler velocity recordings were obtained from the central retinal, ophthalmic, and common carotid arteries, and sampled at 200 Hz. A discrete wavelet-based analysis method was employed to quantify waveforms. The RI was also determined. Patients with IGT were randomized to pioglitazone or placebo, and measurements were repeated after 12-week treatment.

RESULTS

In the ocular waveforms, significant differences in power spectra were observed in frequency band 4 (corresponding to frequencies between 6.25 and 12.50 Hz) between groups (p < 0.05). No differences in RI occurred. No association was observed between waveform parameters and fasting glucose or insulin resistance. Pioglitazone had no effect on waveform structure, despite significantly reducing insulin resistance, fasting glucose, and triglycerides (p < 0.05).

CONCLUSIONS

Analysis of ocular Doppler flow waveforms using the discrete wavelet transform identified microvascular abnormalities that were not apparent using RI. Pioglitazone improved glucose, insulin sensitivity, and triglycerides without influencing the contour of the waveforms.

Tissue Factor Pathway Inhibitor

Objective—

To investigate in women older than 60 whether aortic stiffness or pulse pressure (PP) is associated with selected procoagulant or anticoagulant factors and to examine whether pulsatile stretch influences these factors in human vascular smooth muscle cells (VSMCs) in vitro.

Methods and Results—

Aortic pulse wave velocity (PWV) and carotid PP were studied in 123 apparently healthy postmenopausal women. PWV, PP, von Willebrand factor, and free tissue factor pathway inhibitor (TFPI), but not mean arterial pressure, increased with age. Free TFPI and PWV were positively correlated, even after adjustment for age and PP and other confounding parameters. In vitro, 5% or 10% pulsatile stretch (at 1 Hz) enhanced TFPI synthesis and secretion by VSMCs in a time-independent manner (1 to 48 hours) without changes in protein level of smooth muscle myosin heavy chain. Application of 5% static stretch had no effect.

Conclusion—

In postmenopausal women, free TFPI increases as vascular wall function deteriorates and PP increases. These findings are supported by the increase in TFPI synthesized by VSMCs in response to cyclic stress in vitro. They suggest that VSMCs require pulsatility to interfere with the coagulation process and highlight the relevance of plasma free TFPI levels to cardiovascular diseases.

Arterial stiffness and gait speed in older adults with and without peripheral arterial disease

BACKGROUND

Central arterial stiffness is increasingly recognized as an important predictor of cardiovascular events and mortality in older adults; however, few studies have evaluated the association of arterial stiffness with mobility decline, a common consequence of vascular disease.

METHODS

We analyzed the association of pulse wave velocity (PWV), a measure of aortic stiffness, with longitudinal gait speed over 7 years in 2,172 participants in the Health, Aging and Body Composition (ABC) Study (mean age ± s.d. 73.6 ± 2.9 years, 48% men, 39% black).

RESULTS

In mixed-effects models adjusted for demographics, each s.d. (396 cm/s) higher PWV was associated with 0.015 (s.e. 0.004) m/s slower gait at baseline and throughout the study period in the full cohort (P < 0.001); this relationship was largely explained by hypertension and other vascular risk factors. Among participants with peripheral arterial disease (PAD) (n = 261; 12.7%), each s.d. higher PWV was independently associated with 0.028 (s.e. 0.010) m/s slower gait speed at baseline and throughout the study period (P < 0.01).

CONCLUSIONS

These findings suggest that aortic stiffness may be especially detrimental to mobility in older adults with already compromised arterial function.

Radial pressure pulse and heart rate variability in heat- and cold-stressed humans

This study aims to explore the effects of heat and cold stress on the radial pressure pulse (RPP) and heart rate variability (HRV). The subjects immersed their left hand into 45°C and 7°C water for 2 minutes. Sixty healthy subjects (age 25 ± 4 yr; 29 men and 31 women) were enrolled in this study. All subjects underwent the supine temperature measurements of the bilateral forearms, brachial arterial blood pressure, HRV and RPP with a pulse analyzer in normothermic conditions, and thermal stresses. The power spectral low-frequency (LF) and high-frequency (HF) components of HRV decreased in the heat test and increased in the cold test. The heat stress significantly reduced radial augmentation index (AIr) (P < .05), but the cold stress significantly increased AIr (P < .01). The spectral energy of RPP did not show any statistical difference in 0 ~ 10 Hz region under both conditions, but in the region of 10 ~ 50 Hz, there was a significant increase (P < .01) in the heat test and a significant decrease in the cold test (P < .01). The changes in AIr induced by heat and cold stress were significantly negatively correlated with the spectral energy in the region of 10 ~ 50 Hz (SE_10−50 Hz) but not in the region of 0 ~ 10 Hz (SE_0−10 Hz). The results demonstrated that the SE_10−50 Hz, which only possessed a small percentage in total pulse energy, presented more physiological characteristics than the SE_0−10 Hz under the thermal stresses.

The Cardiovascular Continuum extended: Aging effects on the aorta and microvasculature

The ‘Cardiovascular Continuum’ was described by Dzau and colleagues in 2006 to explain the development over many years of coronary disease with its complications, then end-stage heart failure. The Continuum identified different points along the way where the process could be interrupted by drug therapies or interventions, then described the trials that have been undertaken over the last three decades to establish their value. The approach summarized the major steps in cardiology through modern times, but it had an emphasis on coronary atherosclerosis in prosperous nations, and did not account fully for the problems of aging, which occur in all societies. Aging of the aorta and elastic arteries causes arterial stiffening and leads to development of cardiac failure and microvascular disease in highly perfused organs such as the brain and kidneys. The ‘Vascular Aging Continuum’ which we introduce, dovetails with the late phases of the Cardiovascular Continuum and provides a more comprehensive explanation, especially for vascular diseases in nations with little atherosclerosis. It will become more common in the Western World where attention to risk factors and widespread use of statins are responsible for a decrease in atherosclerotic disease, prolongation of life, and dominance of macrovascular and microvascular arterial disease, as well as of cardiac failure.

Increased arterial stiffness in obstructive sleep apnea: a systematic review

Obstructive sleep apnea is a prevalent disease that is associated with significant morbidity and mortality, particularly due to cardiovascular disease. An emerging cardiovascular risk factor, arterial stiffness, may also be involved in the cardiovascular complications of obstructive sleep apnea. The purpose of this review was to summarize the current literature regarding the effect of obstructive sleep apnea on arterial stiffness. We conducted a systematic literature review using PubMed, Embase and the Cochrane Library. We identified 24 studies that met search criteria investigating the effect of obstructive sleep apnea on arterial stiffness. Arterial stiffness was found to be increased in obstructive sleep apnea patients compared with controls or increased in severe compared with mild sleep apnea. In some studies, a positive correlation was identified between the degree of arterial stiffness and sleep apnea severity. In the two randomized, controlled trials and the two nonrandomized trials identified, treatment of obstructive sleep apnea with continuous positive airway pressure led to significant decreases in arterial stiffness. Obstructive sleep apnea appears to have an independent effect on arterial stiffness, which may be one of the mechanisms accounting for sleep apnea-associated cardiovascular risk.

The macrocirculation and microcirculation of hypertension

Changes in vascular structure that accompany hypertension may contribute to hypertensive end-organ damage. Both the macrovascular and microvascular levels should be considered, as interactions between them are believed to be critically important. Regarding the macrocirculation, the article first reviews basic concepts of vascular biomechanics, such as arterial compliance, arterial distensibility, and stress-strain relationships of arterial wall material, and then reviews how hypertension affects the properties of conduit arteries, particularly examining evidence that it accelerates the progressive stiffening that normally occurs with advancing age. High arterial stiffness may increase central systolic and pulse pressure by two different mechanisms: 1) Abnormally high pulse wave velocity may cause pressure waves reflected in the periphery to reach the central aorta in systole, thus augmenting systolic pressure; 2) In the elderly, the interaction of the forward pressure wave with high arterial stiffness is mostly responsible for abnormally high pulse pressure. At the microvascular level, hypertensive disease is characterized by inward eutrophic or hypertrophic arteriolar remodeling and capillary rarefaction. These abnormalities may depend in part on the abnormal transmission of highly pulsatile blood pressure into microvascular networks, especially in highly perfused organs with low vascular resistance, such as the kidney, heart, and brain, where it contributes to hypertensive end-organ damage.

Hypertension, systolic blood pressure, and large arteries

This article discusses the following: (1) factors modulating central and peripheral SBP and PP in hypertensive subjects; (2) mechanisms enhancing PP variations in this population; (3) Analysis of pulsatile arterial hemodynamics as predictors of CV risk; and (4) Pulsatile hemodynamics and strategies lowering CV risk in the treatment of hypertension.