Changes In Vessel Size Research Articles

Contrast-enhanced computed tomography for exvivo assessment of human kidneys: A proof-of-concept study.

Ex vivo perfusion of transplant-declined human organs has emerged as a promising platform to study the response of an organ to novel therapeutic strategies. However, to fully realize the capability of this platform for performing translational research in human organ pathophysiology, there is a need for robust assays to assess organ function and disease. State-of-the-art research methods rely on analyses of biopsies taken during perfusion, which both damages the organ and only provides localized information. Developing non-invasive, whole organ methods of assessment is critical to the further development of this research platform. We use ex vivo cold infusion scanning (EXCIS) with contrast-enhanced computed tomography (CT) to quantify perfusion in kidneys preserved ex vivo. EXCIS-CT computes three complementary metrics for whole organ assessment: a dynamic assessment of contrast filling, a measure of vascular network anatomical structure, and a static assessment of perfusion heterogeneity. These metrics were applied to a series of six transplant-declined human kidneys, which demonstrated a range of anatomies and perfusion. Lastly, two transplant-declined human kidneys were imaged before and after a 1-h period of ex vivo normothermic perfusion (NMP). We found variable responses to NMP, with one kidney maintaining the vascular network and hemodynamics and the other showing significant changes in vessel size and spatial perfusion profile. EXCIS-CT provides metrics that can be used to characterize whole organ perfusion and vascular function.

Preoperative and postoperative vascular characteristics in AVF creation surgery

Background: Early postoperative vascular ultrasound can predict the maturity of arteriovenous fistulas as well as detect complications.
 Objective: To present the characteristics of upper extremity vessels on ultrasound prior to AVF surgery and to analyze the changes in vessel size and flow rate postoperatively.
 Subjects and methods: We prospectively describe 80 cases of AVF formation at Dong Nai General Hospital from April 2022 to April 2023. Vascular ultrasound evaluations were conducted preoperatively and at 1 day, 2 weeks and 6 weeks postoperatively to evaluate the diameter and the blood flow of vessels used to create AVFs.
 Results: Eighty patients underwent AVF surgery. In forearm AVFs, the median diameter of the feeding artery and the draining vein were 2.12 (1.83 – 2.5) mm and 3.38 (2.9 – 3.80) mm, respectively. In upper-arm AVFs, the median diameter of the feeding artery and the draining vein were 3.67 (3.45 – 3.99) mm and 4.0 (3.64 – 4.05) mm, respectively. The draining vein flow rate showed a strong correlation with the brachial artery flow rate (R2 = 0.94, correlation coefficient = 0.88). The diameter and flow rate of the draining vein at 6 weeks post-surgery displayed significant correlations with their respective values at 2 weeks post-surgery, with correlation coefficients of 0.92 (R2 = 0.66) and 1.04 (R2 = 0.86), respectively. After 6 weeks post-surgery, non-diabetic patients exhibited larger draining vein diameters and higher flow rates compared with diabetic patients.
 Conclusions: The study highlighted the predictive potential of vascular ultrasound at the 2-week postoperative mark for AVF maturation The brachial artery flow rate can serve as a reliable indicator of AVF flow rate. Given the tendency for diabetic patients to exhibit smaller draining vein diameter and lower AVF flow rate than non-diabetic patients, particular caution is recommended when performing preoperative ultrasound mapping in this patient population.

Effect of batch size on the granule properties in planetary centrifugal granulation.

A granulation method using a planetary centrifugal mixer, called planetary centrifugal granulation, has been developed for small-scale production, such as extemporaneous preparation in pharmacies. Although the impact of its operational parameters on granulation is described, the scale effect has not been investigated. Therefore, we aimed to reveal the effects of vessel size and vessel filling rate on granule properties. In this study, ibuprofen 20% granules consisting of lactose, cornstarch, sodium carmellose, and talc were used as model granules. Granulation was performed using geometrically similar containers, 6-58 mL, with a filling rate of 20-70%. After granulation, we monitored the granule properties, for example, median diameter (d50), span of particle size distribution, and sphericity. At filling rates of 40% and 50% in the 58-mL vessel, the granules grew larger in diameter, and at a rate of 30%, the granules showed a higher sphericity. When the filling rate was 30%, d50 became larger and the span decreased as the vessel size increased. The yields of the granules were higher than 95% when using the 12-58 mL vessel. Lastly, the drug content uniformity and drug dissolution behavior of the granules produced in different vessel size were examined. The granules showed similar drug consistencies and drug dissolution profiles. In conclusion, the quality of the products was not affected by changes in vessel size. Thus, pharmacists could prepare and compound the granule formulations with high yield and appropriate quality using an adequate vessel in the same manner.

Do Large Vessels Affect Hemodynamic Monitoring by Near Infrared Spectroscopy?

Near Infrared Spectroscopy (NIRS) is a widely used technique to assess local tissue oxygenation and blood volume. However, several confounding factors complicate its interpretation. Among these is the potential influence exerted on NIRS variables by large vessels possibly located within the sample volume. This influence is generally neglected, according to the consideration that infrared light entering a large vessel is completely absorbed and thus not backscattered to the receiving optode. On the other hand, vessel size changes vary the amount of light absorbed and thus should profoundly affect NIRS variables. Aim of this study is to ascertain whether vessel size changes, as produced by venous occlusion, can affect NIRS blood volume indices. NIRS monitoring was performed over the basilic vein (BV) in 12 subjects (9 M – 3 F; age 31±8 yr) simultaneously to ultrasound assessment of BV size at the same location, while a second NIRS probe was positioned on the biceps muscle (BM), over a virtually vessel-free area. The arm was elevated (~60°) to induce vein collapse and subjected to venous occlusion, according to two pressure profiles: slow (from 0 to 60 mmHg in 135 s; plateau, 30 s; deflation to 0 mmHg in 135 s) and fast (step inflation to 40 mmHg maintained for 30 s). The cross-sectional area of the BV was continuously recorded along with a NIRS blood volume indicator, i.e., the total hemoglobin concentration (tHb). The tHb index detected a blood volume increase 1.7 and 2.5 times larger over BV than over BM during both slow (p<0.01) and fast (p<0.01) venous occlusions, respectively. The responses to slow venous occlusion exhibited different time courses: tHbBM exhibited a rather linear rise with time, while tHbBV showed a steeper rise at the beginning of the response, resulting in a higher convexity of the curve (p=0.01), similar to the time course of BV size. Similar patterns could be observed also in response to fast occlusions (p<0.05) and also on THI tracings (p<0.05 for both slow and fast occlusions). On average, tHbBV tracings were better correlated to BV area tracings (r=0.90) than tHbBM (r=0.83, p<0.001, after Z-transform), in response to the slow occlusion. In addition, respiratory oscillations in BV size were observed in tHbBV and not in tHbBM. In conclusion, these results challenge the long standing belief that large vessels are excluded from the NIRS sample volume. Experimental evidence strongly supports the concept that size changes of large vessels may profoundly affect NIRS variables. Neglecting this possibility may potentially introduce relevant artefacts in NIRS variables in all conditions affecting venous blood pressure, such as postural changes, or the extravascular pressure, such as muscle contraction.

Changes in Microvascular Morphology in Subcortical Vascular Dementia: A Study of Vessel Size Magnetic Resonance Imaging.

Background: Cerebral small vessel disease is the most common cause of subcortical vascular dementia (SVaD). Unfortunately, conventional imaging techniques do not always demonstrate the microvascular pathology that is associated with small vessel disease. The purpose of this study was to evaluate the changes in the microvascular structure of SVaD and to identify how the microvascular changes in vessel size, detected with imaging, affect the gray matter.Methods: Ten SVaD patients and 12 healthy controls underwent vessel size imaging with gradient-echo and spin-echo sequences before and after contrast agent injection. Four microvessel index maps, including total blood volume fraction (BVf), mean vessel density (Q), mean vessel diameter (mVD), and vessel size index (VSI) were calculated. ROI value of each microvessel parameter was compared between SVaD patients and controls. Voxel-wise comparison of microvessel parameters was also performed to assess the regional difference. The relationship between the microvessel parameters in white matter and total gray matter volume (TGV) were assessed.Results: Both mVD and VSI were significantly different between the SVaD and controls in the ROI-based comparisons (unpaired t-test, p < 0.05). mVD and VSI were significantly increased in the SVaD group at the subcortical, periventricular white matter, basal ganglia, and thalami compared with the controls (FDR corrected, p < 0.05). VSI in the white matter areas were significantly negatively correlated with TGV (r = −0.446, p < 0.05).Conclusions: The increase of mVD and VSI in SVaD patients reflects the damage of the microvessels in the white matter, and these changes may lead to the damage of the gray matter.

Sonic Hedgehog upregulation does not enhance the survival and engraftment of stem cell-derived cardiomyocytes in infarcted hearts.

The engraftment of human stem cell-derived cardiomyocytes (hSC-CMs) is a promising treatment for remuscularizing the heart wall post-infarction, but it is plagued by low survival of transplanted cells. We hypothesize that this low survival rate is due to continued ischemia within the infarct, and that increasing the vascularization of the scar will ameliorate the ischemia and improve hSC-CM survival and engraftment. An adenovirus expressing the vascular growth factor Sonic Hedgehog (Shh) was injected into the infarcted myocardium of rats immediately after ischemia/reperfusion, four days prior to hSC-CM injection. By two weeks post-cell injection, Shh treatment had successfully increased capillary density outside the scar, but not within the scar. In addition, there was no change in vessel size or percent vascular volume when compared to cell injection alone. Micro-computed tomography revealed that Shh failed to increase the number and size of larger vessels. It also had no effect on graft size or heart function when compared to cell engraftment alone. Our data suggests that, when combined with the engraftment of hSC-CMs, expression of Shh within the infarct scar and surrounding myocardium is unable to increase vascularization of the infarct scar, and it does not improve survival or function of hSC-CM grafts.

Validation of the Gatortail method for accurate sizing of pulmonary vessels from 3D medical images.

Detailed characterization of changes in vessel size is crucial for the diagnosis and management of a variety of vascular diseases. Because clinical measurement of vessel size is typically dependent on the radiologist's subjective interpretation of the vessel borders, it is often prone to high inter- and intra-user variability. Automatic methods of vessel sizing have been developed for two-dimensional images but a fully three-dimensional (3D) method suitable for vessel sizing from volumetric X-ray computed tomography (CT) or magnetic resonance imaging has heretofore not been demonstrated and validated robustly. In this paper, we refined and objectively validated Gatortail, a method that creates a mathematical geometric 3D model of each branch in a vascular tree, simulates the appearance of the virtual vascular tree in a 3D CT image, and uses the similarity of the simulated image to a patient's CT scan to drive the optimization of the model parameters, including vessel size, to match that of the patient. The method was validated with a 2-dimensional virtual tree structure under deformation, and with a realistic 3D-printed vascular phantom in which the diameter of 64 branches were manually measured 3 times each. The phantom was then scanned on a conventional clinical CT imaging system and the images processed with the in-house software to automatically segment and mathematically model the vascular tree, label each branch, and perform the Gatortail optimization of branch size and trajectory. Previously proposed methods of vessel sizing using matched Gaussian filters and tubularity metrics were also tested. The Gatortail method was then demonstrated on the pulmonary arterial tree segmented from a human volunteer's CT scan. The standard deviation of the difference between the manually measured and Gatortail-based radii in the 3D physical phantom was 0.074mm (0.087 in-plane pixel units for image voxels of dimension 0.85×0.85×1.0mm) over the 64 branches, representing vessel diameters ranging from 1.2 to 7mm. The linear regression fit gave a slope of 1.056 and an R2 value of 0.989. These three metrics reflect superior agreement of the radii estimates relative to previously published results over all sizes tested. Sizing via matched Gaussian filters resulted in size underestimates of >33% over all three test vessels, while the tubularity-metric matching exhibited a sizing uncertainty of >50%. In the human chest CT data set, the vessel voxel intensity profiles with and without branch model optimization showed excellent agreement and improvement in the objective measure of image similarity. Gatortail has been demonstrated to be an automated, objective, accurate and robust method for sizing of vessels in 3D non-invasively from chest CT scans. We anticipate that Gatortail, an image-based approach to automatically compute estimates of blood vessel radii and trajectories from 3D medical images, will facilitate future quantitative evaluation of vascular response to disease and environmental insult and improve understanding of the biological mechanisms underlying vascular disease processes.

Change in the distal vessel luminal diameter following chronic total occlusion revascularization.

Coronary chronic total occlusions (CTO) occur when there is complete, or near complete occlusion of a vessel, angiographically appreciated by the presence of a collateral circulation with late filling of the occluded vessel. With restoration of anterograde blood flow there is alteration in vascular wall stress which may influence distal vessel size. We sought to determine if the distal vessel size changes following revascularization of the CTO. We retrospectively reviewed patients who underwent successful CTO revascularization and who subsequently underwent repeat angiography. We measured the size of the vessel proximal and distal to the stented segment to assess for change in luminal diameter. Thirty-seven successful CTO revascularization procedures were reviewed. The mean age was 70.3, with 81% male. The most commonly revascularised artery was the right coronary artery (RCA). The median time between angiograms was 194days. The indexed luminal diameter distal to the stented segment had a greater increase in size compared to the proximal segment (31.1 vs 4.8%, p<0.0001). The increase in distal vessel was seen in both RCA (34.5 vs 8%, p<0.001) and non-RCA (28.7 vs 1.9%, p<0.001). The distal vessel had a more marked increase in distal luminal diameter if there was no resting hypokinesis in the territory supplied by the CTO (35.6 vs 15.0%, p<0.01). The luminal diameter distal to a revascularized CTO has a greater increase in size compared to the proximal vessel and persists over time. This may have implications on determining stent sizing during CTO procedures as well as determining suitable vessels for attempted revascularization.

Cardiac neural crest ablation results in early endocardial cushion and hemodynamic flow abnormalities.

Cardiac neural crest cell (CNCC) ablation creates congenital heart defects (CHDs) that resemble those observed in many syndromes with craniofacial and cardiac consequences. The loss of CNCCs causes a variety of great vessel defects, including persistent truncus arteriosus and double-outlet right ventricle. However, because of the lack of quantitative volumetric measurements, less severe defects, such as great vessel size changes and valve defects, have not been assessed. Also poorly understood is the role of abnormal cardiac function in the progression of CNCC-related CHDs. CNCC ablation was previously reported to cause abnormal cardiac function in early cardiogenesis, before the CNCCs arrive in the outflow region of the heart. However, the affected functional parameters and how they correlate with the structural abnormalities were not fully characterized. In this study, using a CNCC-ablated quail model, we contribute quantitative phenotyping of CNCC ablation-related CHDs and investigate abnormal early cardiac function, which potentially contributes to late-stage CHDs. Optical coherence tomography was used to assay early- and late-stage embryos and hearts. In CNCC-ablated embryos at four-chambered heart stages, great vessel diameter and left atrioventricular valve leaflet volumes are reduced. Earlier, at cardiac looping stages, CNCC-ablated embryos exhibit abnormally twisted bodies, abnormal blood flow waveforms, increased retrograde flow percentage, and abnormal cardiac cushions. The phenotypes observed in this CNCC-ablation model were also strikingly similar to those found in an established avian fetal alcohol syndrome model, supporting the contribution of CNCC dysfunction to the development of alcohol-induced CHDs.

Testing Foundations of Biological Scaling Theory Using Automated Measurements of Vascular Networks.

Scientists have long sought to understand how vascular networks supply blood and oxygen to cells throughout the body. Recent work focuses on principles that constrain how vessel size changes through branching generations from the aorta to capillaries and uses scaling exponents to quantify these changes. Prominent scaling theories predict that combinations of these exponents explain how metabolic, growth, and other biological rates vary with body size. Nevertheless, direct measurements of individual vessel segments have been limited because existing techniques for measuring vasculature are invasive, time consuming, and technically difficult. We developed software that extracts the length, radius, and connectivity of in vivo vessels from contrast-enhanced 3D Magnetic Resonance Angiography. Using data from 20 human subjects, we calculated scaling exponents by four methods—two derived from local properties of branching junctions and two from whole-network properties. Although these methods are often used interchangeably in the literature, we do not find general agreement between these methods, particularly for vessel lengths. Measurements for length of vessels also diverge from theoretical values, but those for radius show stronger agreement. Our results demonstrate that vascular network models cannot ignore certain complexities of real vascular systems and indicate the need to discover new principles regarding vessel lengths.

Root characteristics of C4 grasses limit reliance on deep soil water in tallgrass prairie

C4 grass species in the mesic tallgrass prairie of central North America can exhibit both high root production and deep rooting in the soil profile (>2 m). Differences in root growth and the types of roots produced vary according to local environmental gradients and management practices. The production of deep roots in tallgrass prairie has been historically presumed as a mechanism for water uptake when surface soils are dry. We examined changes in root biomass, total root length, root width, and theoretical hydraulic conductivity using roots collected from deep soil cores in upland and lowland topographic positions in grazed and ungrazed watersheds of the Konza Prairie Biological Station in north-eastern Kansas, USA. Root biomass, total root length, and theoretical hydraulic conductivity were highest in roots found in the top 20 cm of the soil profile, and then declined exponentially with increasing soil depth. Compared to grazed areas, ungrazed locations had more root biomass and total root length of roots in the most superficial soil layers. No differences in rooting profiles were present among topographic contrasts. Theoretical hydraulic conductivity of axial root xylem did not vary by topographic position or grazing contrasts, and declines in conductivity by depth were driven by changes in the number of vessels per stele, rather than changes in vessel size. Irrespective of differences by grazing treatment or topographic position, significant reductions in root biomass, total root length, and theoretical hydraulic conductivity of grass roots at soil depths greater than 1 m suggest deep roots in this grassland have limited functional significance for water uptake.

A better water status in wheat seedlings induced by Azospirillum under osmotic stress is related to morphological changes in xylem vessels of the coleoptile

Water stress can have major impacts on plant growth and development. Although it has been demonstrated that Azospirillum brasilense Sp245 improved growth and water status in wheat seedlings under salt and osmotic stresses, knowledge of the effects the bacteria could elicit in plant shoot morphology is still scarce. The aim of this work was to examine the average vessel area and the water potential of coleoptiles from seedlings inoculated with A. brasilense Sp245 and non-inoculated controls growing either in water or in osmotic stress conditions. Changes in vessel size have an important role in the adaptation to unfavourable environmental conditions. We found that coleoptiles of Azospirillum-inoculated seedlings showed wider xylem vessels and less negative water potential when grown in 20% PEG 8000. We concluded that Azospirillum inoculation induced wider xylem vessels that might imply an enhanced coleoptile hydraulic conductance which in turn could explain the better water status observed.

The Role of Self-expanding Stents in Patients with Atypical Coronary Anatomy.

Despite advances with new generation stents, there remains some atypical coronary anatomy where optimal stenting continues to be a challenge; such as stent sizing in large, ectatic or aneurysmal vessels; tapered vessels; and in vasoconstricted arteries such as in ST-segment elevation myocardial infarction or chronic total occlusions. Balloon-expandable stents are tubular and cannot easily accommodate vessel diameter variations; thrombotic vessels increase the risk of distal embolisation and no-reflow; positive remodelling and vasodilation often result in subsequent malapposition; and patients with bifurcation lesions have a higher risk of adverse events. The STENTYS BMS and DES(P) stents have a self-expanding design, which enables a better anatomical fit to the vessel, even with diameter variations (up to 6.0 millimetres [mm]), and can adapt to changes in vessel size over time. The stents deploy atraumatically from distal to proximal, which could reduce distal embolisation and contain disconnectable bridges, which can be opened up at a side branch. Self-apposing technology could therefore provide a potential solution to current challenges with balloon-expandable stent technology.

Anatomic and Functional Evaluation of Bifurcation Lesions Undergoing Percutaneous Coronary Intervention

We sought to investigate the mechanism of geometric changes after main branch (MB) stent implantation and to identify the predictors of functionally significant "jailed" side branch (SB) lesions. Seventy-seven patients with bifurcation lesions were prospectively enrolled from 8 centers. MB intravascular ultrasound was performed before and after MB stent implantation, and fractional flow reserve was measured in the jailed SB. The vessel volume index of both the proximal and distal MB was increased after stent implantation. The plaque volume index decreased in the proximal MB (9.1+/-3.0 to 8.4+/-2.4 mm(3)/mm, P=0.001), implicating plaque shift, but not in the distal MB (5.4+/-1.8 to 5.3+/-1.7 mm(3)/mm, P=0.227), implicating carina shifting to account for the change in vessel size (N=56). The mean SB fractional flow reserve was 0.71+/-0.20 (N=68) and 43% of the lesions were functionally significant. Binary logistic-regression analysis revealed that preintervention % diameter stenosis of the SB (odds ratio=1.05; 95% CI, 1.01 to 1.09) and the MB minimum lumen diameter located distal to the SB ostium (odds ratio=3.86; 95% CI, 1.03 to 14.43) were independent predictors of functionally significant SB jailing. In patients with > or =75% stenosis and Thrombolysis In Myocardial Infarction grade 3 flow in the SB, no difference in post-stent angiographic and intravascular ultrasound parameters was found between SB lesions with and without functional significance. Both plaque shift from the MB and carina shift contribute to the creation/aggravation of an SB ostial lesion after MB stent implantation. Anatomic evaluation does not reliably predict the functional significance of a jailed SB stenosis.

Quantitative impact of cardiovascular risk factors and vascular closure devices on the femoral artery after repeat cardiac catheterization

We evaluated the exact quantitative long-term impact of repeated catheterizations, vascular closure devices, and cardiovascular risk factors on the femoral artery after cardiac catheterization. A total of 2,102 available femoral angiograms from 827 consecutive patients were analyzed using caliper-based quantitative vascular analysis. These patients underwent coronary interventions between January 2005 and April 2007 and had at least one additional catheterization procedure through the ipsilateral femoral access site from December 2001 until January 2008. Multivariate analysis was performed to control for confounding variables. The primary outcome was change in artery size. The average punctured artery diameter was 6.5 +/- 2.1 mm. The average time between the first case and last follow-up was 349 days. There was no significant change of the punctured artery size over time after the index procedure (P = .15) and no change associated with the use of vascular closure devices (P = .25) after multivariate analysis. Smaller arteries were associated with female gender (-1.22 mm, P < .0001), presence of angiographic peripheral vascular disease (PVD, -1.19 mm, P < .0001), and current (-0.48 mm, P = .001) or former (-0.23 mm, P = .01) smoking status, whereas previous statin therapy was associated with an increase in artery size (+0.47 mm, P < .0001). Vascular closure devices were used less often compared with manual compression in cases preceding the first detection of angiographic PVD (P < .001). Vascular closure devices are not associated with a change in the artery size or progression of PVD. Overall, there is no change in vessel size over time after repeat catheterizations, with a decrease in vessel size associated with current and former smoking and an increase with previous statin therapy.

Mechanisms Underlying Maternal Venous Adaptation in Pregnancy

To define the effects of pregnancy on mechanical properties and reactivity, mesenteric veins from late pregnant and virgin control (nonpregnant) rats were pressurized to determine gestational changes in size and distensibility. Reactivity studies used an adrenergic constrictor (norepinephrine) and an endothelium-mediated vasodilator (acetylcholine). The contribution of nitric oxide to endothelial function was evaluated with pharmacologic inhibition of nitric oxide synthase. Roles of nitric oxide and cyclic guanosine monophosphate in smooth muscle vasodilation were determined using an nitric oxide donor with and without cyclic guanosine monophosphate inhibition using ODQ, a selective inhibitor of guanylyl cyclase. In pregnancy, endothelium-dependent vasodilation markedly increased (largely due to endogenous nitric oxide), smooth muscle response to nitric oxide decreased (primarily related to cyclic guanosine monophosphate production), and norepinephrine sensitivity decreased considerably, with no changes in vessel size or distensibility. Our results identify a provasodilatory state in the systemic venous system, which would serve to facilitate the accommodation to plasma volume expansion requisite for normal pregnancy.

A bioabsorbable everolimus-eluting coronary stent system (ABSORB): 2-year outcomes and results from multiple imaging methods

Drug-eluting metallic coronary stents predispose to late stent thrombosis, prevent late lumen vessel enlargement, hinder surgical revascularisation, and impair imaging with multislice CT. We assessed the safety of the bioabsorbable everolimus-eluting stent (BVS). 30 patients with a single de-novo coronary artery lesion were followed up for 2 years clinically and with multiple imaging methods: multislice CT, angiography, intravascular ultrasound, derived morphology parameters (virtual histology, palpography, and echogenicity), and optical coherence tomography (OCT). Clinical data were obtained from 29 of 30 patients. At 2 years, the device was safe with no cardiac deaths, ischaemia-driven target lesion revascularisations, or stent thromboses recorded, and only one myocardial infarction (non-Q wave). 18-month multislice CT (assessed in 25 patients) showed a mean diameter stenosis of 19% (SD 9). At 2-year angiography, the in-stent late loss of 0.48 mm (SD 0.28) and the diameter stenosis of 27% (11) did not differ from the findings at 6 months. The luminal area enlargement on OCT and intravascular ultrasound between 6 months and 2 years was due to a decrease in plaque size without change in vessel size. At 2 years, 34.5% of strut locations presented no discernible features by OCT, confirming decreases in echogenicity and in radiofrequency backscattering; the remaining apparent struts were fully apposed. Additionally, vasomotion occurred at the stented site and adjacent coronary artery in response to vasoactive agents. At 2 years after implantation the stent was bioabsorbed, had vasomotion restored and restenosis prevented, and was clinically safe, suggesting freedom from late thrombosis. Late luminal enlargement due to plaque reduction without vessel remodelling needs confirmation.

MyD88-dependent, superoxide-initiated inflammation is necessary for flow-mediated inward remodeling of conduit arteries

Vascular remodeling normalizes abnormal hemodynamic stresses through structural changes affecting vessel size and wall thickness. We investigated the role of inflammation in flow-mediated vascular remodeling using a murine model of partial outflow reduction without flow cessation or neointima formation. Common carotid arteries decreased in size after ipsilateral external carotid artery ligation in wild-type mice, but not in myeloid differentiation protein-88 (MyD88)–deficient mice. Inward remodeling was associated with MyD88-dependent and superoxide-initiated cytokine and chemokine production, as well as transient adventitial macrophage accumulation and activation. Macrophage depletion prevented flow-mediated inward vascular remodeling. Expression of MyD88 by intrinsic vascular cells was necessary for cytokine and chemokine production and changes in vessel size, whereas MyD88 expression by bone marrow–derived cells was obligatory for changes in vessel size. We conclude that there are at least two distinct roles for MyD88 in flow-mediated inward remodeling of conduit arteries. Our findings suggest that inflammation is necessary for vascular adaptation to changes in hemodynamic forces.

Determining exercise‐induced blood flow reserve in lower extremities using phase contrast MRI

To study the changes in limb blood flow during lower extremity exercise using phase contrast (PC) MRI in normal volunteers. Healthy volunteers performed plantar flexion exercise (<1 W) for four minutes. Flow velocity was measured using cardiac-gated, cine PC-MRI sequences (fast gradient recalled echo [GRE]; multishot echo planar imaging [EPI]) on a 3T scanner at the level of the superficial femoral artery (SFA): 1) preexercise; 2) immediately postexercise; 3) during three minutes recovery; and 4) postrecovery. At rest there was a triphasic flow waveform in the SFA. During exercise it changed to a monophasic pattern with an increase in total flow; there were variable changes in vessel size and flow velocity. The waveform regained the triphasic pattern during recovery. The exercise-induced flow reserve (FR) was 167 +/- 90%. PC-MRI demonstrates that the resting triphasic flow waveform transforms into a monophasic pattern with submaximal exercise and returns to baseline with recovery. This increase in the regional blood flow allows for measurement of exercise-induced FR in the SFA.

Video rate electrical impedance tomography of vascular changes: preclinical development

Peripheral vasculature disease is strongly correlated with cardiovascular-associated mortality. Monitoring circulation health, especially in the peripheral limbs, is vital to detecting clinically significant disease at a stage when it can still be addressed through medical intervention. Electrical impedance tomography (EIT) maps the electrical properties of tissues within the body and has been used to image dynamically varying physiology, including blood flow. Here, we suggest that peripheral vasculature health can be monitored with EIT by imaging the hemodynamics of peripheral vessels and the surrounding tissues during reactive hyperemia testing. An analysis based on distinguishability theory is presented that indicates that an EIT system capable of making measurements with a precision of 50 µV may be able to detect small changes in vessel size associated with variations in blood flow. An EIT system with these precision capabilities is presented that is able to collect data at frame rates exceeding 30 fps over a broad frequency range up to 10 MHz. The system's high speed imaging performance is verified through high contrast phantom experiments and through physiological imaging of induced ischemia with a human forearm. Region of interest analysis of the induced ischemia images shows a marked decrease in conductivity over time, changing at a rate of approximately −3 × 10−7 S m−1 s−1, which is the same order of magnitude as reported in the literature. The distinguishability analysis suggests that a system such as the one developed here may provide a means to characterize the hemodynamics associated with blood flow through the peripheral vasculature.