Minimum Vessel Diameter Research Articles

Simultaneous stent implantation for pulmonary artery bifurcation stenosis in infants.

Pulmonary artery (PA) bifurcation stenosis often requires simultaneous stent placement, which may be technically challenging. Limited data exist regarding this practice in infants. We aim to report the procedural outcomes and safety of bifurcation stent placement in infants. We performed a single-center retrospective review of infants younger than 12 months who underwent simultaneous stent placement for PA bifurcation stenosis from January 1, 2001 through December 31, 2019. Seventeen infants underwent simultaneous PA bifurcation stent placement. The median age was 6.4 months (1.1-10.1 months), and weight was 5.8 kg (3-10.6 kg). Nine (52.9%) patients had had prior PA intervention. Most stents were placed in central PAs (28, 82.4%), followed by lobar branches (6, 17.6%). All patients received pre-mounted stents. The peak gradient across each branch decreased from 47.4 ± 16 to 18.7 ± 13 mm Hg (P less than .0001). The right ventricle to systemic systolic pressure ratio decreased from systemic (1.0 ± 0.3) to just over half systemic (0.58 ± 0.2) (P = .0001). The minimum vessel diameter increased from 3.6 ± 1.5 to 6.0 ± 1.9 mm (P less than .0001). There were 4 (23.5%) patients with high severity adverse events. There were no procedure-related deaths. The median follow-up period was 83.8 months (5.3 months-19.4 years). All patients had subsequent PA re-intervention at a median time of 8.1 months (2.9 months-8.8 years), and median time to re-operation was 19.1 months (2.9 months-7.5 years). Simultaneous PA stent placement is an effective strategy for relief of bifurcation stenosis in infants. Future transcatheter interventions are necessary to account for patient growth, but may delay the need for re-operation.

Prospective Study of Upper Limb Vessel Diameters and their Association with Arteriovenous Fistula Maturation in End Stage Renal Disease Patients

Purpose: For the creation of an upper limb arteriovenous fistula (AVF), the 2018 Clinical Practice Guidelines of the European Society for Vascular Surgery (ESVS) suggest a minimum vessel diameter of 2 mm and 3 mm for radiocephalic (RCAVF) and brachiocephalic AVFs (BCAVF), respectively. However, there have been no large scale studies in Indian patients to substantiate these guidelines. The aim of this study was to estimate the upper limb vessel diameters and their association with the maturation of AVF at six weeks.

Efficacy of the Flow Re-direction Endoluminal Device for cerebral aneurysms and causes of failed deployment

PurposeThe Flow Re-direction Endoluminal Device (FRED) has recently become available for flow diversion in Japan. We have encountered cases that failed to deploy the FRED. In this study, we report our initial experience with the FRED for cerebral aneurysms and clarify the causes of failed FRED deployment.MethodsA retrospective data analysis was performed to identify patients treated with the FRED between June 2020 and March 2021. Follow-up digital subtraction angiography was performed at 3 and 6 months and assessed using the O’Kelly-Marotta (OKM) grading scale.ResultsThirty-nine aneurysms in 36 patients (average age: 54.4 years) were treated with the FRED. The average sizes of the dome and neck were 9.9 mm and 5.2 mm, respectively. In nine patients, additional coiling was performed. In one patient (2.6%), proximal vessel injury caused direct carotid-cavernous fistula during deployment. Ischaemic complications were encountered in one patient (2.6%) with transient symptoms. Angiographic follow-up at 6 months revealed OKM grade C or D in 86.6% of patients. FRED deployment was successful in 35 (92.1%) procedures. In the failure group, the differences between the FRED and the minimum vessel diameter (P = 0.04) and the rate of the parent vessel having an S-shaped curve (P = 0.04) were greater than those in the success group.ConclusionsFlow diversion using the FRED is effective and safe for treating cerebral aneurysms. The use of the FRED for patients with an S-shaped curve in the parent vessel and oversizing of more than 2 mm should be considered carefully.

Abstract 14957: Comparison of Coronary Tree Detection and Diameter Quantification From a Deep Learning Convolutional Neural Network With Quantitative Coronary Angiography

Introduction: QCA (Quantitative Coronary Angiography) is an accepted standard for assessing coronary artery stenosis severity. QCA computes the percentage diameter reduction of the lesion, improving upon visual inspection since it provides a numerical quantification of stenosis severity. However, it can be costly, and it requires human input to correct the boundaries of the vessel. AngioNet is a fully-automatic deep learning convolutional neural network trained to identify coronary trees and their vessel diameters in angiograms, and could be a cost-effective alternative to QCA. To explore the accuracy of AngioNet, we compared its ability to identify vessels and their diameter when compared with QCA. Methods: Angiograms with 3-vessel QCA reports from 89 patients acquired at Madras Medical Mission were used. The entire vessel tree was segmented for each angiogram using AngioNet. A fast-marching method was used to calculate the radius along the vessel’s centerline. Vessel diameter was compared in two regions corresponding to the regions marked in the QCA report: the most proximal region, containing the maximum vessel diameter, and the region of stenosis. If no stenosis was present, the distal region containing minimum diameter was selected. The difference in maximum and minimum vessel diameter between QCA and AngioNet was computed, and a Bland-Altman plot (see figure) was used to determine the interchangeability of both methods. Results: The mean absolute difference between both measurements was 0.27mm. The standardized difference was 0.215, corresponding to a 91.5% overlap of their distributions. Lastly, 97% of data points were within the limits of agreement, suggesting minimal clinical differences and that both methods may be interchangeable. Conclusions: Deep learning convolutional networks may be used to assess vessel diameters at a level that agrees well with those of QCA. AngioNet has the potential to automate the detection of stenosis severity.

Wood anatomy and conductivity in lianas, shrubs and trees of Bignoniaceae

This work compares potential xylem hydraulic efficiency among Bignoniaceae lianas, shrubs and trees. Five species from each growth habit were analysed to determine variance among habits based on quantitative and qualitative wood anatomical features. Potential hydraulic conductivity was calculated for each species in order to compare efficiency of water transport. Cambial variants are present in the Bignonieae tribe, as phloem wedges in lianas and phloem arcs in shrubs. Lianas present vessel dimorphism, quantitatively evidenced by the ratio of maximum by minimum vessel diameter of about 20, higher percentage of vessel area and lower percentage of fibres compared with the self-supporting species studied here. Potential hydraulic conductivity is higher in lianas due to the presence of wider vessels and it is hypothesised that the narrow vessels can function as back-up for water conduction when wider vessels are cavitated.

Impact of Vessel Diameter Measured by Preprocedural Computed Tomography Angiography on Immediate and Late Outcomes of Endovascular Therapy for Iliac Artery Diseases.

We evaluated whether vessel diameters measured by preprocedural computed tomography angiography (CTA) affects the immediate and late outcomes of endovascular therapy for iliac artery diseases.Methods and Results:A total of 254 patients who underwent endovascular treatment for iliac artery diseases were retrospectively evaluated. Minimum vessel diameters were measured on preprocedural CTA images at target lesions, common iliac arteries, and external iliac arteries (EIA). Predictors of immediate and late procedural outcomes were analyzed. Procedural failure or vessel-specific complications occurred in 29 patients (11%): wire passage failure (n=10), rupture (n=8), and distal embolization (n=11). Target lesion revascularization (TLR) was required in 6.0% at 2 years. Independent predictors of procedural failure or vessel-specific complications were small minimum vessel diameter of the target lesion (odds ratio [OR]=0.68, P=0.008) or EIA (OR=0.67, P=0.008), and chronic total occlusions (OR=3.78, P=0.036). Small minimum EIA diameter (hazard ratio [HR]=0.66, P=0.017) and chronic total occlusions (HR=4.45, P=0.024) were independent predictors of TLR in patients with technical success. Small vessel diameter of the target lesion or EIA was an independent predictor of procedural failure or vessel-specific complications. Small vessel diameter, particularly of the EIA, was also associated with increased TLR after successful endovascular therapy for iliac artery lesions.

Intracranial blood flow changes after extracranial carotid artery stenting.

Carotid artery stenting is an endovascular treatment option for patients with extracranial carotid stenosis. However, intracranial blood flow changes following stenting have not been established. To determine the effects of stenting on intracranial blood flow. Records of patients who underwent stenting at our institution between 2004 and 2012 and had flow rates obtained pre- and poststenting by the use of quantitative magnetic resonance angiography were retrospectively reviewed. Percentage stenosis, stenosis length, and minimum vessel diameter were measured from cerebral angiography images. Eighteen patients were included. Mean age was 65 years with 67% presenting with symptomatic stenosis. Degree of stenosis ranged from 60% to 90%. Internal carotid artery (ICA) mean flow improved significantly poststenting from 174.9 ± 83.6 mL/min to 250.7 ± 91.2 mL/min (P = .011). Ipsilateral middle cerebral artery (MCA) flow, however, was not significantly altered poststenting (107.8 ± 41.6 mL/min vs 114.3 ± 36.3 mL/min; P = .28). Univariate analysis revealed that improved minimum vessel diameter after stenting, but not percentage stenosis (P = .18) or stenosis length (P = .45), is significantly associated with increased ICA flow (P = .02). However, improved percentage stenosis, stenosis length, minimum vessel diameter, and ICA flow poststenting were not significantly associated with increased MCA flow (P = .64, .38, .13, .37, respectively). ICA flow was compromised at baseline, improving 43% on average poststenting. Increased minimum vessel diameter was the factor most significantly associated with increased flow. Conversely, MCA flow was not significantly compromised at baseline nor altered after stenting, suggesting compensatory intracranial collateral supply prestenting that redistributes following ICA revascularization.

Wood anatomy reflects the distribution of Krascheninnikovia ceratoides (Chenopodiaceae)

Wood anatomy characters of the Eurasian/North American half-shrub Krascheninnikovia ceratoides were investigated on plants from different parts of the wide distribution area. The secondary xylem is developed as result of anomalous secondary thickening. The vessels are small (commonly <50 μm) and the secondary xylem is rayless. Differences in vessel diameter exist between the main axis, basal branches and flowering shoots. The maximum as well as the minimum vessel diameter in the flowering shoots is significantly smaller compared to the basal branches, as well as in the main axis in all provenances. The length of thick-walled libriform fibre cells varies between the main axis and the basal branches of the same plant individual, but in the short main axis the length of libriform fibre cells is relatively constant (193–217 μm), independent of provenance and climate. Obviously, the length of libriform fibre cells is a conservative character and dependent on plant size. The vessel diameter is a more sensitive parameter for ecological studies. It varies more clearly, considering the vessel position in the plant axis system, in relation with climate differences of the provenances of the examined plants. Plants from a temperate, semi-humid climate have the largest vessel diameter in basal branches and flowering shoots, while the vessel diameter of plants from an arid temperate climate in Central Asia is smallest. The vessel diameters depend not only on climate, but also on the position in the axial system of the plants. There is a trade-off between average vessel number and their maximum diameter in flowering shoots of populations from Russia and Mongolia. Thus, vessel diameters depend on both, position in the axial system of the plant and climatic conditions.

Pulmonary artery stents: Long‐term follow‐up

Determine the long-term outcomes of branch pulmonary artery (PA) stents. PA stents in congenital heart disease effectively relieve stenoses in the short-term. Published long-term data are limited. Patients enrolled in an FDA IDE protocol from 1989-92 were included. Clinical follow-up and catheterization data were evaluated. Patients were included if >5 year follow-up data was available or if mortality occurred following the initial procedure. There were five deaths: four due to progression of their underlying heart disease, and one from a complication during a follow-up catheterization. Clinical data for 43 surviving patients demonstrated 39 patients (91%) are in NYHA class I or II. Seven patients underwent surgical intervention during the follow-up period (five RV-PA conduit, two Fontan revisions), but none addressed PA stenosis. Final repeat catheterizations were performed in 36 patients (55 stents) 7.2 +/- 4.3 years post stent insertion with 1.2 +/- 0.9 further procedures with stent dilations. In this subgroup, the minimum vessel diameter increased from 4.7 +/- 1.8 to 13.4 +/- 2.4 mm (P < 0.001), and the pressure gradient improved from 41 +/- 25 to 9 +/- 11 mm Hg (P < 0.001). Higher initial gradient and smaller balloons were associated with a final stent diameter of <14 mm (P = 0.030 and 0.046). Jailed vessels occurred in 49% of stents with abnormal angiographic flow in 18/55. Six repeat catheterizations resulted in complications, including the one procedural death. Stents implants for PA stenoses provide effective improvement in vessel caliber in the long-term. Although repeat interventions are necessary, this procedure reduces RV pressure and provides an important alternative to surgery for residual PA obstruction.

Wood identification of Dalbergia nigra (CITES Appendix I) using quantitative wood anatomy, principal components analysis and naive Bayes classification

Dalbergia nigra is one of the most valuable timber species of its genus, having been traded for over 300 years. Due to over-exploitation it is facing extinction and trade has been banned under CITES Appendix I since 1992. Current methods, primarily comparative wood anatomy, are inadequate for conclusive species identification. This study aims to find a set of anatomical characters that distinguish the wood of D. nigra from other commercially important species of Dalbergia from Latin America. Qualitative and quantitative wood anatomy, principal components analysis and naïve Bayes classification were conducted on 43 specimens of Dalbergia, eight D. nigra and 35 from six other Latin American species. Dalbergia cearensis and D. miscolobium can be distinguished from D. nigra on the basis of vessel frequency for the former, and ray frequency for the latter. Principal components analysis was unable to provide any further basis for separating the species. Naïve Bayes classification using the four characters: minimum vessel diameter; frequency of solitary vessels; mean ray width; and frequency of axially fused rays, classified all eight D. nigra correctly with no false negatives, but there was a false positive rate of 36.36 %. Wood anatomy alone cannot distinguish D. nigra from all other commercially important Dalbergia species likely to be encountered by customs officials, but can be used to reduce the number of specimens that would need further study.

Simultaneous stent implantation to treat bifurcation stenoses in the pulmonary arteries: Initial results and long‐term follow up

Balloon angioplasty of bifurcating pulmonary artery (PA) stenoses is often inadequate, and stent treatment often requires simultaneous implantation of two stents. This study evaluates initial results and long-term follow up of transcatheter stent placement in bifurcating PAs. This is a retrospective review of patients (pts) who had bifurcating PA stents placed in main and lobar branches from 1993 to 2007. Forty-nine pts had bifurcating PA stents placed at a median age of 10.9 years (range 1-43 years). The mean minimum vessel diameter increased from 5.7 +/- 2.5 mm to 11.0 +/- 3.6 mm (P < 0.001), the mean gradient across the stenoses decreased from 37.0 +/- 26.9 to 9.2 +/- 13 mm Hg (P < 0.001), whereas the mean RV:FA ratio decreased from 0.76 +/- 0.29 to 0.53 +/- 0.24 (P < 0.001). There was one death due to severe pulmonary hemorrhage. F/U data were available in 38 pts (mean duration 6.3 +/- 4.1 years, range 1.2-13.1 years). Thirty pts underwent repeat catheterizations (mean 2.3 +/- 2.2 years poststent), with 26 requiring further interventions: Fifteen had balloon angioplasty alone and 11 had additional stents placed. There were no complications at f/u catheterization. Six pts underwent further palliative surgeries, although none for repair of branch PA stenoses. Simultaneous transcatheter placement of bifurcating PA stents provides immediate gradient relief of bifurcating stenoses in the proximal or lobar branch PAs and reduces RV systolic pressure. Further interventions can be safely performed in future procedures, and the presence of stents does not complicate future surgeries.

Stenting of stenotic or occluded iliofemoral veins, superior and inferior vena cavae in children with congenital heart disease: Acute results and intermediate follow up

To determine the short and intermediate term outcome following systemic venous stent placement in children with congenital heart disease. Patients with congenital heart disease are at risk of stenosis or occlusion of systemic veins following indwelling lines or catheterizations. Stent dilation may ameliorate symptoms and open the vessel for use during future procedures. We report our acute and intermediate results. All patients with systemic venous stent placement in the iliofemoral veins, inferior or superior vena cava at our institution between 1998 and 2006 were included. Initial and the follow-up catheterization data were reviewed retrospectively. 70 stents were placed in 33 patients (36 vessels). Median age was 2.6 years (0.2-14.2) and weight 11.5 kg (3.8-78.7). 17/36 vessels (47%) were occluded requiring recanalization. Following stent delivery, the mean minimum vessel diameter increased from 3.1 +/- 3.2 to 7.2 +/- 3.0 mm (P < 0.001). There were no major complications. Seventeen patients and vessels had a total of 62 follow-up catheterizations, with median length of follow-up 4.1 years (0.7-9.3). During intermediate follow up, 7/17 vessels (41%) required additional intervention. Six patients had additional balloon dilation of existing stents, and one additional stent was placed. Vessels were further dilated to 8.4 +/- 3.5 mm at the last catheterization. Systemic venous stents are safe and effective in recanalizing stenosed or occluded vessels. At follow-up, reocclusion can occur, however, previously placed stents can be safely recanalized if necessary. Future studies will determine if stenting is indicated in a broader population.

The measurement of temperature with electron paramagnetic resonance spectroscopy.

An electron paramagnetic resonance (EPR) technique, potentially suitable for in vivo temperature measurements, has been developed based on the temperature response of nitroxide stable free radicals. The response has been substantially enhanced by encapsulating the nitroxide in a medium of a fatty acid mixture inside a proteinaceous microsphere. The mixture underwent a phase transition in the temperature range required by the application. The phase change dramatically altered the shape of the EPR spectrum, providing a highly temperature sensitive signal. Using the nitroxide dissolved in a cholesterol and a long-chain fatty acid ester, we developed a mixture which provides a peakheight ratio change from 3.32 to 2.11, with a standard deviation of 0.04, for a temperature change typical in biological and medical applications, from 38 to 48 degrees C. This translated to an average temperature resolution of 0.2 degree C for our experimental system. The average diameter of the nitroxide mixture-filled microspheres was approximately 2 microns. Therefore, they are compatible with in vivo studies where the microspheres could be injected into the microvasculature having a minimum vessel diameter of the order of 8 microns. This temperature measuring method has various potential clinical applications, especially in monitoring and optimizing the treatment of cancer with hyperthermia. However, several problems regarding temperature and spatial resolution need to be resolved before this technique can be successfully used to monitor temperatures in vivo.

Predicting Liquid Re-Entrainment in Horizontal Separators

Summary The design procedure for horizontal-separator sizing results in a range of configurations of vessel diameter and length that will perform adequate-liquid separation. The actual diameter chosen depends on a trade-off between smaller, more economic diameters and the larger diameters needed to preventre-entrainment of previously separated liquid droplets that can break away from the gas/liquid interface. The lower diameter limit has been determined previously by design guidelines based on the slenderness ratio of the vessel. This article presents a procedure for determining the lower diameter limit and calculating the maximum gas capacity of a horizontal separator on the basis of liquid re-entrainment. The method is based on correlations for predicting the onset of liquid re-entrainment developed by Ishii and Grolmes. The procedure uses known and predicted liquid and gas properties and may be used in conjunction with normal design procedures for more economic horizontal-separator designs. Introduction Entrainment refers to liquid droplets breaking away from a gas/liquid interface to become suspended in the gas phase. The term re-entrainment is used in horizontal-separator design because it generally is assumed that droplets have settled to the liquid phase and then are returned to the gas phase. Liquid re-entrainment is caused by high gas velocities. Momentum transfer from the gas to the liquid and associated pressure variations on the gas/liquid interface cause disturbances in the two-phase boundary. These disturbances manifest themselves as waves and ripples. Gas-to-liquid momentum transfer to a disturbed interface is more efficient than to a smooth surface, which allows droplets to break away from the liquid phase. Re-entrainment must be avoided in horizontal separators because it is the reverse of the gas/liquid separation desired. This necessity imposes an upperlimit on the gas velocity allowed across the liquid surface in the gravity settling section of the separator, which places a lower limit in the vessel on the cross-sectional area for gas flow. Vessel design therefore is limited by a combination of minimum vessel diameter and maximum liquid level because these determine the cross-sectional area. Previously, such rules of thumb as a maximum slenderness ratio of 4:5 have been used to avoid re-entrainment.1 This article presents a procedure for predicting when re-entrainment is possible on the basis of previously developed correlations and discusses modifications to design procedures to produce more economical horizontal-separator designs. Re-Entrainment Theory Re-entrainment is a physical phenomenon of two-phase stratified fluid flow. The onset of re-entrainment occurs at the boundary of the stratified wavy and annular mist two-phase flow regimes at relatively high gas/liquid velocities, as Fig. 12 shows. Re-entrainment is caused by rapid momentum transfer from gas to liquid. For the purposes of this article, only the onset of re-entrainment must be predicted because no amount of re-entrainment can be allowed in a horizontal separator. Ishii and Grolmes3 and Ishii and Kaichiro4 proposed correlations for predicting the minimum velocity required for re-entrainment of liquid into gas for concurrent flow. The equations (see Appendix) are based on interpretation of experimental data taken from several gas/liquid systems, including water or oil and nitrogen or helium. The correlations use the Reynolds film number and an interfacial viscosity number to characterize the two-phase flow. These are defined asEquation 1and Equation 2 N Ref is a measure of the turbulence of the liquidphase and indicates which mechanism of re-entrainment is most likely for the flow conditions considered. Ishii and Grolmes3 proposed three distinct mechanisms forre-entrainment. For NRef&amp;lt;160, a wave undercut mechanism was proposed where gas impinges on the gas/liquid interface, undercutting it and breaking displaced liquid away from the interface. Athigher NRef, roll wave shear, where the tops of waves are sheared off by high relative velocities between gas and liquid, becomes the dominant mechanism. NRef&amp;gt;1,635 indicates a highly turbulent condition dominated by interfacial properties. AsNRef increases, the liquid surface becomes rougher, and the importance of NRef diminishes asymptotically. These mechanisms occur in three flow regimes, called low Reynolds number(&amp;lt;160), transition (160 to 1,635), and rough turbulent (&amp;gt;1,635).Re-entrainment is more likely at high NRef. N μ is a measure of the resiliency of the liquid surface under turbulent conditions. In physical terms, it is the ratio of viscous forces induced in the liquid by flow to the surface tension maintaining the gas/liquid interface. Re-entrainment becomes more likely with higherNμ. The tendency of liquids to re-entrain increases appreciably as Nμ exceeds 1/15.