Changes In Vascular Compliance Research Articles

Evaluation of the Information Content for Determining the Vascular Tone Type of the Lower Extremities in Varicose Veins: A Case Study

The incidence of cardiovascular diseases is continuously increasing around the world. Therefore, the study of new methods for diagnosing cardiovascular diseases is very important. Early diagnosis and evaluation of the effectiveness of treatments are among the most important tasks. In this work, we study changes in vascular compliance and vascular tone of the lower extremities in a patient diagnosed with an early stage of varicose veins. The study is based on recording the bioimpedance signals of the lower extremities and their parts using the Rheo-32 multichannel device. Registration in the monitoring system takes place in two stages: the first in a state of relaxation, and the second after applying a local massage on one of the legs for five minutes. The results indicate a change in the type of vascular tone of the lower extremities after the massage, while the type of vascular tone changes and shifts on average towards the normotonic type. The method proposed in this study makes it possible to quantitatively and qualitatively assess changes in the tone of the vessels of the extremities.

Quantitative Blood Volume Analysis and Hemodynamic Measures of Vascular Compliance in Patients With Worsening Heart Failure

The role of blood volume (BV) expansion vs a change in vascular compliance in worsening heart failure (HF) remains under debate. We aimed to assess the relationship between BV and resting and stress hemodynamics in worsening HF and to further elucidate the significance of BV in cardiac decompensation. Patients with worsening HF underwent radiolabeled indicator-dilution BV analysis and cardiac catheterization. Intravascular volumes and resting/stress hemodynamics were recorded. Provocative stress maneuvers included change in systolic blood pressure (ΔSBP) from lying to standing and Valsalva and intracardiac pressure changes with leg raise. Correlation between BV and invasive hemodynamics were assessed by linear regression. Of 27 patients with worsening HF, patients' characteristics included mean age 61 ± 12 years, 70% male, 19% Black, and mean ejection fraction 29% ± 15%. Of the patients, 13 (48%) had hypervolemia as measured by total BV, which weakly correlated with ΔSBP by position (R2 = 0.009) and Valsalva (R2 = 0.003) and with right atrial (R2 = 0.049) and pulmonary capillary wedge (R2 = 0.047) pressure changes during leg raise. In patients with worsening HF, BV mildly correlated with intracardiac pressures at rest. Provocative maneuvers intended to test vascular compliance did not correlate with BV, indicating that compliance may serve as a stand-alone metric in HF.

Effects of Power Walking on Body Composition and Vascular Compliance in Inactive, Smoking, and Obese Middle-aged Women

본 연구는 파워 워킹이 비활동적이면서 흡연을 하는 비만 중년여성을 대상으로 신체조성과 혈관 탄성에 미치는 영향을 규명 하는데 있다. 대상자들은 D 광역시 콜 센터에 근무하는 자들로 흡연을 시작한 지 6년 이상이었고, 규칙적인 스포츠활동에 참여하지 않았으며, 비만 이외에 어떠한 질환도 없었다. 실험 목적과 절차를 충분히 설명한 후 자발적으로 참여 의사를 밝히 18명을 대상으로 파워 워킹 운동프로그램을 적용하였다. 개인별 운동강도는 폴라 측정기를 이용하여 컨트롤 하였으며, 1-3주 50%HRmax, 4-6주 60%HRmax로 설정하여 다음과 같은 결과를 얻었다. 첫째, 신체조성의 변화는 파워 워킹 참여 후 체중, 체지방율, BMI에서 유의한 감소를 보였다(p<.05). 둘째, 혈관 탄성의 변화는 파워 워킹 참여 후 오른손, 왼손, 오른발, 왼발에서 유의한 증가를 보였다(p<.05) 따라서 비활동적이면서 흡연을 하는 비만 중년여성에게 규칙적인 파워 워킹은 체중과 체지방을 감소시키고, 혈관 기능을 개선 시켜 건강한 일상생활을 하는데 필수적인 운동요법이라고 할 수 있다.This study aims to examine the effects of power walking on body composition and vascular compliance in inactive, smoking, and obese middle-aged women. At the time of this study, the subjects were working for a call center in D metropolitan city, had been smoking for six years or more, were not participating in regular sports activities, and had no diseases besides obesity. After fully explaining the experimental purpose and procedure, a power walking exercise program was conducted with 18 total subjects who voluntarily agreed to participate in the program. The individual exercise intensity was controlled by using a polar measuring instrument. Applying 50% HRmax for 1-3 weeks and 60% HRmax for 4-6 weeks, the results were obtained as follows. First, regarding the change in body composition, there were significant decrease in weight, body fat percentage, and BMI after participating in the power walking (p<.05). Second, regarding the change in vascular compliance, there were significant increase in the right hand, left hand, right foot, and left foot after participating in the program (p<.05). Such results imply that regular power walking may be an essential exercise therapy for healthy daily life by reducing both weight and body fat percentage, as well as improving vascular function in inactive, smoking, and obese middle-aged women.

Vasodilatation by carbon dioxide and sodium nitroglycerin reduces compliance of the cerebral arteries in humans.

What is the central question of this study? Vascular compliance importantly contributes to the regulation of cerebral perfusion and complex mechanisms are known to influence compliance of a vascular bed: while vasodilatation mediates changes in vascular resistance, does it also affect compliance, particularly in the cerebral vasculature? What is the main finding and its importance? Cerebral vasodilatation, elicited by hypercapnia and sodium nitroglycerin administration, reduced cerebrovascular compliance by approximately 26% from baseline. This study provides new insight into mechanisms mediating cerebrovascular compliance. Changes in vascular resistance and vascular compliance contribute to the regulation of cerebral perfusion. While changes in vascular resistance are known to be mediated by vasodilatation, the mechanisms contributing to changes in vascular compliance are complex. In particular, whether vasodilatation affects compliance of the vasculature within the cranium remains unknown. Therefore, the present study examined the impact of two vasodilatation pathways on cerebrovascular compliance in humans. Fifteen young, healthy adults (26±5years, seven females) completed two protocols: (i) sublingual sodium nitroglycerin (SNG; 0.4mg) and (ii) hypercapnia (5-6% carbon dioxide gas mixture for 4 min). Blood pressure waveforms (finger photoplethysmography) and middle cerebral artery blood velocity waveforms (transcranial Doppler ultrasound) were input into a modified Windkessel model and an index of cerebrovascular compliance (Ci) was calculated. During the SNG protocol, Ci decreased 24±17% from baseline ((5.0±2.3)×10-4 cms-1 mmHg-1 ) to minute 10 ((3.6±1.2)×10-4 cms-1 mmHg-1 ; P=0.009). During the hypercapnia protocol, Ci decreased 28±9% from baseline ((4.4±1.9)×10-4 cms-1 mmHg-1 ) to minute 4 ((3.1±1.4)×10-4 cms-1 mmHg-1 ; P<0.001). Cerebral vasodilatory stimuli induced by nitric oxide and carbon dioxide mechanisms reduced compliance of the cerebral vascular bed by approximately 26% from supine baseline values.

Rapid changes in vascular compliance contribute to cerebrovascular adjustments during transient reductions in blood pressure in young, healthy adults.

Characterization of dynamic cerebral autoregulation has focused primarily on adjustments in cerebrovascular resistance in response to blood pressure (BP) alterations. However, the role of vascular compliance in dynamic autoregulatory processes remains elusive. The present study examined changes in cerebrovascular compliance and resistance during standing-induced transient BP reductions in nine young, healthy adults (3 women). Brachial artery BP (Finometer) and middle cerebral artery blood velocity (BV; Multigon) waveforms were collected. Beginning 20 beats before standing and continuing 40 beats after standing, individual BP and BV waveforms of every second heartbeat were extracted and input into a four-element modified Windkessel model to calculate indexes of cerebrovascular resistance (Ri) and compliance (Ci). Standing elicited a transient reduction in mean BP of 20 ± 9 mmHg. In all participants, a large increase in Ci (165 ± 84%; P < 0.001 vs. seated baseline) occurred 2 ± 2 beats following standing. Reductions in Ri occurred 11 ± 3 beats after standing (Ci vs. Ri delay: P < 0.001). The increase in Ci contributed to maintained systolic BV before the decrease in Ri. The present results demonstrate rapid, large but transient increases in Ci that precede reductions in Ri, in response to standing-induced reductions in BP. Therefore, Ci represents a discreet component of cerebrovascular responses during acute decreases in BP and, consequently, dynamic autoregulation.NEW & NOTEWORTHY Historically, dynamic cerebral autoregulation has been characterized by adjustments in cerebrovascular resistance following systematic changes in blood pressure. However, with the use of Windkessel modeling approaches, this study revealed rapid and large increases in cerebrovascular compliance that preceded reductions in cerebrovascular resistance following standing-induced blood pressure reductions. Importantly, the rapid cerebrovascular compliance response contributed to preservation of systolic blood velocity during the transient hypotensive phase. These results broaden our understanding of dynamic cerebral autoregulation.

엘리트선수 경력자의 유산소성 운동이 혈관탄성의 회복력에 미치는 영향

The purpose of this study is to examine the effects of regular exercise done in the past on the improvement of vascular compliance and provide specific data that regular exercise is a positive factor for vascular health by comparing vascular compliance changes before and after 12 weeks of aerobic exercise between elite athletes who have exercised for many years and ordinary people. 10 retired athletes who have more than 5 years of track record and no regular exercise for more than 3 years after retirement and 13 people who have not regularly exercised for more than 3 years were selected as the subjects of this study.BR For a period of 12 weeks, the 10 people in the exercise-experienced group and 13 people in the control group, selected as above, conducted 70-minute-aerobic exercise on a treadmill for 3 times a week with a rate of perceived effort less than 17. PASW 18.0 statistical program was used to calculate the mean and standard deviation of each item from the collected results. For the general characteristics of the subjects, descriptive statistics were performed and repeated measure ANOVA was also carried out for the effectiveness of experimental treatment on the exercise-experienced and control groups. The significance level was verified near at p.05BR The results showed that the vascular compliance values of the left hand, right hand, left foot and right foot of both of the control group and exercise-experienced groups was increased after 12 weeks of exercise. Hypothesis testing of each item revealed that there is no statistical significance in all parts of left hand, right hand, left foot and right foot. However, statistical significance was found in left foot (F=29.9769, p.001) and right foot (F=33.058, p.001) by hypothesis testing between items. In addition, positive changes of vascular compliance were observed to progress faster in the exercise-experienced group compared to the control group.

Effects of Cross-Clamping on Vascular Mechanics: Comparing Waveform Analysis With a Numerical Model

BackgroundImmediate changes in vascular mechanics during aortic cross-clamping remain widely unknown. By using a numerical model of the arterial network, vascular compliance and resistance can be estimated and the time constant of pressure waves can be calculated and compared with results from the classic arterial waveform analysis. MethodsExperimental data were registered from continuous invasive radial artery pressure measurements from 11 patients undergoing vascular surgery. A stable set of beats were chosen immediately before and after each clamping event. Through the arterial waveform analysis, the time constant was calculated for each individual beat and for a mean beat of each condition as to compare with numerical simulations. Overall proportional changes in resistance and compliance during clamping and unclamping were calculated using the numerical model. ResultsArterial waveform analysis of individual beats indicated a significant 10% median reduction in the time constant after clamping, and a significant 17% median increase in the time constant after unclamping. There was a positive correlation between waveform analysis and numerical values of the time constant, which was moderate (ρ = 0.51; P = 0.01486) during clamping and strong (ρ = 0.77; P ≤ 0.0001) during unclamping. After clamping, there was a significant 16% increase in the mean resistance and a significant 23% decrease in the mean compliance. After unclamping, there was a significant 19% decrease in the mean resistance and a significant 56% increase in the mean compliance. ConclusionsThere are significant hemodynamic changes in vascular compliance and resistance during aortic clamping and unclamping. Numerical computer models can add information on the mechanisms of injury due to aortic clamping.

The stop-flow arm equilibrium pressure in preoperative patients: Stressed volume and correlations with echocardiography.

The distending intravascular pressure at no flow conditions reflects the stressed volume. While this haemodynamic variable is recognised as clinically important, there is a paucity of reports of its range and responsiveness to volume expansion in patients without cardiovascular disease and no reports of correlations to echocardiographic assessments of left ventricular filling. Twenty-seven awake (13 male), spontaneously breathing patients without any history of cardiopulmonary, vascular or renal disease were studied prior to induction of anaesthesia. The no-flow equilibrium pressure in the arm following rapid circulatory occlusion (Parm ) was measured via a radial arterial catheter. Transthoracic echocardiography was used to measure left ventricular end diastolic area and volume as well as the diameter of the inferior vena cava. The Parm and echocardiographic variables were measured before and after administration of 500mL 0.9% NaCl over 10minutes. Changes were analysed by paired t test, Pearson's correlation and multiple linear regression. Parm increased overall from 22±5mmHg to 25±6mmHg (mean difference 3.0±4.5mmHg, P=0.002) following the fluid bolus with corresponding increases in arterial pressure and echocardiographic variables. Variability in the direction of the Parm response reflected concomitant changes in vascular compliance. Only weak correlations were observed between changes in Parm and inferior vena cava diameter indexed to body surface area (R2 =0.29, P=0.01). Preoperative measurements of Parm increased following acute expansion of the intravascular volume. Echocardiography demonstrated poor correlation with Parm .

A pilot study to measure vascular compliance changes during fistula maturation using open-source software.

Autogenous arteriovenous fistulas are the preferred access for hemodialysis. Yet when created, fistulas often fail to mature, requiring surgical or radiologic interventions before their use. This pilot study measures the vascular wall elasticity and flow gradient using an open-source ultrasound software program designed to aid in assessing fistula maturation. A total of seven end-stage renal disease patients were enrolled for our study after providing informed consent. Ultrasound scanning was performed for the inflow artery, post-arterial anastomotic segment, and outflow vein at initial and follow-up evaluation. Conventional digital imaging and communications in medicine data were collected from the ultrasound machine. The vessel diameter and distensibility of artery, post-arterial anastomotic segment, and vein were computed from the digital imaging and communications in medicine data using an open-source ultrasound software program. The vessel diameter of artery and vein increased from 4.6 ± 1.1 mm to 6.0 ± 1.1 mm and from 5.8 ± 0.7 mm to 7.5 ± 0.9 mm from 1 to 6 weeks post-operation, respectively. Conversely, the vessel diameter of post-arterial anastomotic segment decreased from 4.2 ± 1.0 mm to 3.5 ± 0.9 mm from 1 to 6 weeks post-operation. The distensibility of artery and post-arterial anastomotic segment increased from 3.4% ± 0% to 5.9% ± 1.1% and 3.7% ± 1.2% to 4.9% ± 1.4%, respectively, while the distensibility of vein decreased from 5.0% ± 1.3% to 2.6% ± 0.4% from 1 to 6 weeks post-operation. This study demonstrates that the change in vessel diameter and distensibility related to the healthy remodeling as the vein dilates during maturation.

Does cardiac resynchronization therapy restore peripheral circulatory homeostasis?

AimsTo evaluate whether peripheral circulatory ‘remodelling’ as measured by changes in vascular compliance and in markers of nitric oxide signalling contributes to patient response to cardiac resynchronization therapy (CRT).Methods and resultsEffects of CRT were evaluated in 33 patients pre‐procedure and 6 months post‐procedure. Peak oxygen consumption, 6 min walk distance, New York Heart Association class, and quality of life score were evaluated. Augmentation index and its interactions with nitric oxide (NO) were evaluated by applanation tonometry. Platelet NO responsiveness and content of thioredoxin‐interacting protein were assessed. Plasma concentrations of N‐terminal proBNP, asymmetric and symmetric dimethylarginine (SDMA), high sensitivity C‐reactive protein, catecholamines, and matrix metalloproteinases‐2 and ‐9 were assessed. Despite significant improvement in 6 min walk distance (P = 0.005), New York Heart Association class (P < 0.001), quality of life (P = 0.001), and all echocardiographic parameters post‐CRT, there were no significant changes in augmentation index measurements, thioredoxin‐interacting protein content, and platelet NO response. Significant falls in N‐terminal proBNP (P = 0.008) and SDMA (P = 0.013; independent of renal function) occurred. Falls in SDMA predicted reduction in high‐sensitivity C‐reactive protein (P = 0.04) and increases in peak oxygen consumption (P = 0.04). There were no correlations between changes in echocardiographic parameters and those in vascular function.ConclusionsThese data suggest that the beneficial effects of CRT over 6 months are independent of any change in peripheral NO‐related signalling. However, there is evidence that suppression of inflammation occurs, and its magnitude predicts extent of clinical improvement.

The photoplethysmographic amplitude to pulse pressure ratio can track sudden changes in vascular compliance and resistance during liver graft reperfusion: A beat-to-beat analysis.

During liver transplantation, the thermodilution cardiac output (CO) technique cannot respond to sudden hemodynamic changes associated with postreperfusion syndrome. Photoplethysmography (PPG) can reflect changes in intravascular volume and thus can be used to assess vasomotor tone and arterial stiffness on the pressure–volume relation. We investigated whether a beat-to-beat analysis of the arterial pressure–PPG relationship can estimate dynamic changes in vascular characteristics immediately after liver graft reperfusion.In 10 recipients, arterial blood pressure and PPG waveforms recorded simultaneously were analyzed from the beginning of fall to nadir in systolic blood pressure immediately after reperfusion. On a beat-to-beat basis, we compared the ratio of the amplitude of PPG to arterial pulse pressure (PPGamp/PP, as relative vascular compliance) to total peripheral resistance (TPR) and Windkessel compliance (Cwk) obtained from the Modelflow CO algorithm.Following graft reperfusion, PPGamp/PP and Cwk increased (median 41.5%; P = .005 and 42.0%; P < .001, respectively), whereas TPR decreased (median −46.4%; P < .001). Beat-to-beat PPGamp/PP was negatively correlated with TPR (median r = –0.80 [95% CI –0.85 to –0.76] on linear regression and r2 = 0.84 [95% CI 0.73–0.92] on curvilinear regression), and was positively correlated with Cwk (median r = 0.86 [95% CI 0.81–0.91] on linear regression and r2 = 0.88 [95% CI 0.75–0.96] on curvilinear regression).Our results suggest that relative compliance, obtained from beat-to-beat analysis of PPG and arterial pressure waveforms, can track abrupt changes in vascular characteristics associated with postreperfusion syndrome. This simple index would contribute to differential diagnoses of sudden hypotension.

Abstract 259: Genetic Inactivation of Sirt3 Does Not Alter Endothelial Function or Vascular Compliance in Hypercholesterolemic Mice

Endothelial dysfunction and arterial stiffening major risk factors associated with progression of atherosclerosis and increased risk of acute coronary events. Recent data suggest sirtuins may play a role in protecting against a variety age-related diseases, and we recently reported that sirtuins are reduced in the aging vasculature. The roles of SIRT3 (a deacetylase that is largely restricted to the mitochondria) in the regulation of vasomotor function and arterial stiffness, however, remains poorly understood. Therefore, we hypothesized that genetic inactivation of SIRT3 in hypercholesterolemic mice will impair endothelial function and reduce vascular compliance compared to hypercholesterolemic mice with normal levels of SIRT3. We used Ldlr -/- /ApoB 100/100 (LA) mice that were either wild-type for SIRT3 (LA-SIRT3 +/+ ) or null for SIRT3 (LA-SIRT3 -/- ) and fed a western diet for 12 months. At time of sacrifice, aorta was removed for isolated organ chamber baths to measure changes in endothelium-dependent relaxation to acetylcholine (ACH), and carotid arteries were harvested to assess changes in vascular compliance using a pressurized cannulation system. Surprisingly, losses of SIRT3 did not impair relaxation to ACH in aorta compared to LA-SIRT3 +/+ mice (38.2±4.4%, 37.0±4.4%, respectively). Furthermore, reductions in SIRT3 did not impact vascular compliance or distensibility in carotid arteries from the same animals. In conclusion, in contrast to our hypothesis, inactivation of SIRT3 does not impact vasomotor function or conduit vessel compliance in advanced atherosclerosis. Importantly, this and may be explained by a “floor-effect”, and future work examining the effect of SIRT3 overexpression on vascular function and pathology will be instrumental in determining its biological role and ultimate therapeutic utility.

Detailed Measurement of Wall Strain with 3D Speckle Tracking in the Aortic Root: A Case of Bionic Support for Clinical Decision Making

Three-dimensional (3D) wall motion tracking (WMT) based on ultrasound imaging enables estimation of aortic wall motion and deformation. It provides insights into changes in vascular compliance and vessel wall properties essential for understanding the pathogenesis and progression of aortic diseases. In this report, we employed the novel 3D WMT analysis on the ascending aorta aneurysm (AA) to estimate local aortic wall motion and strain in case of a patient scheduled for replacement of the aortic root. Although progression of the diameter indicates surgical therapy, at present we addressed the question for optimal surgical time point. According to the data, AA in our case has enlarged diameter and subsequent reduced circumferential wall strain, but area tracking data reveals almost normal elastic properties. Virtual remodeling of the aortic root opens a play list for different loading conditions to determine optimal surgical intervention in time.

Assessment of Prescribing Pattern of Antihypertensive Medications in Elderly Hypertensive

Introduction : In elderly hypertensive patients, blood pressure is over 140/90mmHg. Diuretics, renin angiotensin aldosterone system inhibitors, beta blockers, calcium channel blockers, alpha blockers and direct vasodilators are commonly prescribed to treat geriatric hypertensive patients. The choice of drugs for a particular patient changes at short intervals because of factors like changes in vascular compliance, efficacy, side effects, cost and launch of new drugs in pharmaceutical market. These facts indicate the need for assessment of prescribing pattern of antihypertensives. Objective: The prescribing pattern of antihypertensive medications was assessed in elderly patients who were suffering from hypertension. Methodology: It was a prospective observational study for six months carried out on in-patients who were admitted to general medicine units. The study protocol was approved by the human ethical committee. The patients of either sex and aged above 60 years and satisfying the study criteria such as diagnosed newly as suffering from hypertension as per Joint National Committee (JNC-7) guidelines and prescribed with antihypertensive medications were enrolled. The clinical, social and medication data was collected from the case records into a specialised patient profile form to analyze prescribing pattern of medications. All the data was analyzed using descriptive statistics. Results and Discussion: Totally 93 prescriptions were collected from the study patients. The proportion of male to female patients was 53:46 and their mean age was 68.74 ± 8.6years. Of 93 prescriptions, 50 (53.76%) prescriptions were containing antihypertensive medications as monotherapy and 43 (46.23%) prescriptions were containing antihypertensive medications as combination drug therapy. Of 50 prescriptions that were containing single antihypertensive medications, amlodepine was frequently 26 (52%) found prescribed among others. The results obtained in our study were similar to the study results conducted by Mohammed A et al. Among 43 prescriptions that were containing combination of antihypertensive medications, telmisartan+ hydrochlorothiazide were the drug combinations that were frequently 22 (51.16%) found prescribed among others.The results obtained in our study were similar to the study results conducted by Arshad HM et al. This combination was reported as fixed dose combinations used in hospitals in for treating patients enrolled in other studies. Conclusion: The medications such as amlodipine and telmisartanand hydrochlorothiazide are frequently prescribed as monotherapy and combination therapy respectievely to treat elderly patients suffering from hypertension.

Pregnancy induces persistent changes in vascular compliance in primiparous women

Pregnancy induces rapid, progressive, and substantial changes to the cardiovascular system. The low recurrence risk of preeclampsia, despite familial predisposition, suggests an adaptation associated with pregnancy that attenuates the risk for subsequent preeclampsia. We aimed to evaluate the persistent effect of pregnancy on maternal cardiovascular physiology. Forty-five healthy nulliparous women underwent baseline cardiovascular assessment before conception and repeated an average of 30 months later. After baseline evaluation, 17 women conceived singleton pregnancies and all delivered at term. The remaining 28 women comprised the nonpregnant control group. We measured mean arterial blood pressure, cardiac output, plasma volume, pulse wave velocity, uterine blood flow, and flow-mediated vasodilation at each visit. There was a significant decrease in mean arterial pressure from the prepregnancy visit to postpartum in women with an interval pregnancy (prepregnancy, 85.3±1.8; postpartum, 80.5±1.8 mm Hg), with no change in nonpregnant control subjects (visit 1, 80.3±1.4; visit 2, 82.8±1.4 mm Hg) (P=.002). Pulse wave velocity was significantly decreased in women with an interval pregnancy (prepregnancy, 2.73±0.05; postpartum, 2.49±0.05 m/s), as compared with those without an interval pregnancy (visit 1, 2.56±0.04; visit 2, 2.50±0.04 m/s) (P=.005). We did not observe a residual effect of pregnancy on cardiac output, plasma volume, uterine blood flow, or flow-mediated vasodilation. Our observations of decreased mean arterial pressure and reduced arterial stiffness following pregnancy suggest a significant favorable effect of pregnancy on maternal cardiovascular remodeling. These findings may represent a mechanism by which preeclampsia risk is reduced in subsequent pregnancies.

Measurement of aortic wall strain with 3D speckle tracking*

Aims: Non-invasive ultrasound coupled with speckle tracking may estimate aortic wall motion and deformation providing important insight into changes in vascular compliance and vessel wall properties which are necessary for understanding the pathogenesis and progression of aortic diseases, such as atherosclerosis and aneurysm. So far, 2D speckle tracking has been used in arterial wall strain measurement. In this study, the novel 3D speckle tracking technique was employed to estimate aortic wall motion and strain.

Vascular Compliance Changes of the Coronary Vessel Wall After Bioresorbable Vascular Scaffold Implantation in the Treated and Adjacent Segments

Implantation of a metallic prosthesis creates local stiffness with a subsequent mismatch in the compliance of the vessel wall, disturbances in flow and heterogeneous distribution of wall shear stress. Polymeric bioresorbable ABSORB scaffolds have less stiffness than metallic platform stents. We sought to analyze the mismatch in vascular compliance after ABSORB implantation and its long-term resolution with bioresorption. A total of 83 patients from the ABSORB trials underwent palpography investigations (30 and 53 patients from ABSORB Cohorts A and B, respectively) to measure the compliance of the scaffolded and adjacent segments at various time points (from pre-implantation up to 24 months). The mean of the maximum strain values was calculated per segment by utilizing the Rotterdam Classification (ROC) score and expressed as ROC/mm. Scaffold implantation lead to a significant decrease in vascular compliance (median [IQR]) at the scaffolded segment (from 0.37 [0.24-0.45] to 0.14 [0.09-0.23], P<0.001) with mismatch in compliance in a paired analysis between the scaffolded and adjacent segments (proximal: 0.23 [0.12-0.34], scaffold: 0.12 [0.07-0.19], distal: 0.15 [0.05-0.26], P=0.042). This reported compliance mismatch disappears at short- and mid-term follow-up. The ABSORB scaffold decreases vascular compliance at the site of scaffold implantation. A compliance mismatch is evident immediately post-implantation and in contrast to metallic stents disappears in the mid-term, likely leading to a normalization of the rheological behavior of the scaffolded segment.

Measurement of cerebral microvascular compliance in a model of atherosclerosis with optical coherence tomography

Optical coherence tomography (OCT) has recently been used to produce 3D angiography of microvasculature and blood flow maps of large vessels in the rodent brain in-vivo. However, use of this optical method for the study of cerebrovascular disease has not been fully explored. Recent developments in neurodegenerative diseases has linked common cardiovascular risk factors to neurodegenerative risk factors hinting at a vascular hypothesis for the development of the latter. Tools for studying cerebral blood flow and the myogenic tone of cerebral vasculature have thus far been either highly invasive or required ex-vivo preparations therefore not preserving the delicate in-vivo conditions. We propose a novel technique for reconstructing the flow profile over a single cardiac cycle in order to evaluate flow pulsatility and vessel compliance. A vascular model is used to simulate changes in vascular compliance and interpret OCT results. Comparison between atherosclerotic and wild type mice show a trend towards increased compliance in the smaller arterioles of the brain (diameter < 80μm) in the disease model. These results are consistent with previously published ex-vivo work confirming the ability of OCT to investigate vascular dysfunction.

Air Pollution and Cardiovascular Disease in the Multi-Ethnic Study of Atherosclerosis

Research to date demonstrates a relationship between exposure to ambient air pollutants and cardiovascular disease (CVD). Many studies have shown associations between short-term exposures to elevated levels of air pollutants and CVD events, and several cohort studies suggest effects of long-term exposure on cardiovascular mortality, coronary heart disease events, and stroke. The biologic mechanisms underlying this long-term exposure relationship are not entirely clear but are hypothesized to include systemic inflammation, autonomic nervous system imbalance, changes in vascular compliance, altered cardiac structure, and development of atherosclerosis. The Multi-Ethnic Study of Atherosclerosis provides an especially well-characterized population in which to investigate the relationship between air pollution and CVD and to explore these biologic pathways. This article reviews findings reported to date within this cohort and summarizes the aims and anticipated contributions of a major ancillary study, the Multi-Ethnic Study of Atherosclerosis and Air Pollution.

Characterization of 7- and 19-month-old Tg2576 mice using multimodal in vivo imaging: limitations as a translatable model of Alzheimer's disease

With 90% of neuroscience clinical trials failing to see efficacy, there is a clear need for the development of disease biomarkers that can improve the ability to predict human Alzheimer's disease (AD) trial outcomes from animal studies. Several lines of evidence, including genetic susceptibility and disease studies, suggest the utility of fluorodeoxyglucose positron emission tomography (FDG-PET) as a potential biomarker with congruency between humans and animal models. For example, early in AD, patients present with decreased glucose metabolism in the entorhinal cortex and several regions of the brain associated with disease pathology and cognitive decline. While several of the commonly used AD mouse models fail to show all the hallmarks of the disease or the limbic to cortical trajectory, there has not been a systematic evaluation of imaging-derived biomarkers across animal models of AD, contrary to what has been achieved in recent years in the Alzheimer's Disease Neuroimaging Initiative (ADNI) (Miller, 2009). If animal AD models were found to mimic endpoints that correlate with the disease onset, progression, and relapse, then the identification of such markers in animal models could afford the field a translational tool to help bridge the preclinical-clinical gap. Using a combination of FDG-PET and functional magnetic resonance imaging (fMRI), we examined the Tg2576 mouse for global and regional measures of brain glucose metabolism at 7 and 19 months of age. In experiment 1 we observed that at younger ages, when some plaque burden and cognitive deficits have been reported, Tg2576 mice showed hypermetabolism as assessed with FDG-PET. This hypermetabolism decreased with age to levels similar to wild type (WT) counterparts such that the 19-month-old transgenic (Tg) mice did not differ from age matched WTs. In experiment 2, using cerebral blood volume (CBV) fMRI, we demonstrated that the hypermetabolism observed in Tg mice at 7 months could not be explained by changes in hemodynamic parameters as no differences were observed when compared with WTs. Taken together, these data identify brain hypermetabolism in Tg2576 mice which cannot be accounted for by changes in vascular compliance. Instead, the hypermetabolism may reflect a neuronal compensatory mechanism. Our data are discussed in the context of disease biomarker identification and target validation, suggesting little or no utility for translational based studies using Tg2576 mice.