Consistent stoichiometric long-term relationships between nutrients and chlorophyll-a across shallow lakes

Aquatic ecosystems are threatened by eutrophication from nutrient pollution. In lakes, eutrophication causes a plethora of deleterious effects, such as harmful algal blooms, fish kills and increased methane emissions. However, lake-specific responses to nutrient changes are highly variable, complicating eutrophication management. These lake-specific responses could result from short-term stochastic drivers overshadowing lake-independent, long-term relationships between phytoplankton and nutrients. Here, we show that strong stoichiometric long-term relationships exist between nutrients and chlorophyll a (Chla) for 5-year simple moving averages (SMA, median R² = 0.87) along a gradient of total nitrogen to total phosphorus (TN:TP) ratios. These stoichiometric relationships are consistent across 159 shallow lakes (defined as average depth < 6 m) from a cross-continental, open-access database. We calculate 5-year SMA residuals to assess short-term variability and find substantial short-term Chla variation which is weakly related to nutrient concentrations (median R² = 0.12). With shallow lakes representing 89% of the world's lakes, the identified stoichiometric long-term relationships can globally improve quantitative nutrient management in both lakes and their catchments through a nutrient-ratio-based strategy.

Machine learned interatomic potential for dispersion strengthened plasma facing components

Tungsten (W) is a material of choice for the divertor material due to its high melting temperature, thermal conductivity, and sputtering threshold. However, W has a very high brittle-to-ductile transition temperature, and at fusion reactor temperatures (≥1000 K), it may undergo recrystallization and grain growth. Dispersion-strengthening W with zirconium carbide (ZrC) can improve ductility and limit grain growth, but much of the effects of the dispersoids on microstructural evolution and thermomechanical properties at high temperatures are still unknown. We present a machine learned Spectral Neighbor Analysis Potential for W-ZrC that can now be used to study these materials. In order to construct a potential suitable for large-scale atomistic simulations at fusion reactor temperatures, it is necessary to train on ab initio data generated for a diverse set of structures, chemical environments, and temperatures. Further accuracy and stability tests of the potential were achieved using objective functions for both material properties and high temperature stability. Validation of lattice parameters, surface energies, bulk moduli, and thermal expansion is confirmed on the optimized potential. Tensile tests of W/ZrC bicrystals show that although the W(110)-ZrC(111) C-terminated bicrystal has the highest ultimate tensile strength (UTS) at room temperature, observed strength decreases with increasing temperature. At 2500 K, the terminating C layer diffuses into the W, resulting in a weaker W-Zr interface. Meanwhile, the W(110)-ZrC(111) Zr-terminated bicrystal has the highest UTS at 2500 K.

Nitrate as a predictor of cyanobacteria biomass in eutrophic lakes in a climate change context

We aimed to predict cyanobacteria biomass and nitrate (NO₃^-) concentrations in Lake Võrtsjärv, a large, shallow, and eutrophic lake in Estonia. We used a model chain based on the succession of a mechanistic (INCA-N) model and an empirical, generalized linear model. INCA-N model calibration and validation was performed with long term climate and catchment parameters. We constructed twelve scenarios as combinations of climate forcing from the Intergovernmental Panel on Climate Change (IPCC, 3 scenarios), land conversion (forest to agriculture, 2 scenarios), and fertilizer use (2 scenarios). Models predicted 46% of the variance of cyanobacteria biomass and 65% of that of NO₃^- concentrations. The model chain simulated that scenarios comprising both forest conversion to agricultural lands and a greater use of fertilizer per surface area unit would cause increases in lacustrine NO₃^- (up to twice the historical mean) and cyanobacteria biomass (up to a four-fold increase compared to the historical mean). The changes in NO₃^- concentrations and cyanobacteria biomass were more pronounced in low and moderate warming scenarios than in high warming scenarios because of increased denitrification rates in a warmer climate. Our findings show the importance of reducing anthropogenic pressures on lake catchments in order to reduce harmful pollutant and microalgae proliferation, and highlight the counterintuitive effects of multiple stressor interactions on lake functioning.

External Sources Inhibit Benthic Phosphorus Fluxes in the Lower Great Miami River, Southwest Ohio

Human activities have increased nutrient loadings to aquatic ecosystems, especially during the past century. During low river flow in late summer and early fall, elevated concentrations of phosphorus (P) and nitrogen are present in the temperate Lower Great Miami River and contribute to its eutrophication. Although wastewater treatment plants are suspected of being major sources of P to the river, riverbed sediment has not been examined as an additional potential source of P. Benthic P fluxes were measured at 11 representative locations along the Lower Great Miami River during 3 sampling campaigns in late summer and early fall of 2015. Benthic fluxes of filtered total P (range, -1.6-12 mg m^-2  d^-1 ) were related inversely to filtered total P concentrations in river water (p = 0.002, r = -0.60). This relationship suggests that elevated P in river water inhibits mobilization from sediment, likely by minimizing the concentration gradient between porewater and overlying water. To effectively mitigate long-term effects of legacy P stored in Lower Great Miami River sediments, external sources must continue to be managed and discharges reduced to allow legacy P to be mobilized and flushed from the system. Reducing nutrient loading will help protect water quality in the Lower Great Miami River, in other comparable rivers, and in downstream aquatic habitats. Environ Toxicol Chem 2020;39:1517-1525. © 2020 SETAC.

Hurricane Disturbance Stimulated Nitrification and Altered Ammonia Oxidizer Community Structure in Lake Okeechobee and St. Lucie Estuary (Florida)

Nitrification is an important biological link between oxidized and reduced forms of nitrogen (N). The efficiency of nitrification plays a key role in mitigating excess N in eutrophic systems, including those with cyanobacterial harmful algal blooms (cyanoHABs), since it can be closely coupled with denitrification and removal of excess N. Recent work suggests that competition for ammonium (NH₄⁺) between ammonia oxidizers and cyanoHABs can help determine microbial community structure. Nitrification rates and ammonia-oxidizing archaeal (AOA) and bacterial (AOB) community composition and gene abundances were quantified in Lake Okeechobee and St. Lucie Estuary in southern Florida (United States). We sampled during cyanobacterial (Microcystis) blooms in July 2016 and August 2017 (2 weeks before Hurricane Irma) and 10 days after Hurricane Irma made landfall. Nitrification rates were low during cyanobacterial blooms in Lake Okeechobee and St. Lucie Estuary, while low bloom conditions in St. Lucie Estuary coincided with greater nitrification rates. Nitrification rates in the lake were correlated (R² = 0.94; p = 0.006) with AOA amoA abundance. Following the hurricane, nitrification rates increased by an order of magnitude, suggesting that nitrifiers outcompeted cyanobacteria for NH₄⁺ under turbid, poor light conditions. After Irma, AOA and AOB abundances increased in St. Lucie Estuary, while only AOB increased in Lake Okeechobee. AOA sequences clustered into three major lineages: Nitrosopumilales (NP), Nitrososphaerales (NS), and Nitrosotaleales (NT). Many of the lake OTUs placed within the uncultured and uncharacterized NS δ and NT β clades, suggesting that these taxa are ecologically important along this eutrophic, lacustrine to estuarine continuum. After the hurricane, the AOA community shifted toward dominance by freshwater clades in St. Lucie Estuary and terrestrial genera in Lake Okeechobee, likely due to high rainfall and subsequent increased turbidity and freshwater loading from the lake into the estuary. AOB community structure was not affected by the disturbance. AOA communities were consistently more diverse than AOB, despite fewer sequences recovered, including new, unclassified, eutrophic ecotypes, suggesting a wider ecological biogeography than the oligotrophic niche originally posited. These results and other recent reports contradict the early hypothesis that AOB dominate ammonia oxidation in high-nutrient or terrestrial-influenced systems.

Ammonium recycling supports toxic Planktothrix blooms in Sandusky Bay, Lake Erie: Evidence from stable isotope and metatranscriptome data

Sandusky Bay, Lake Erie, receives high nutrient loadings (nitrogen and phosphorus) from the Sandusky River, which drains an agricultural watershed. Eutrophication and cyanobacterial harmful algal blooms (cyanoHABs) persist throughout summer. Planktothrix agardhii is the dominant bloom-forming species and the main producer of microcystins in Sandusky Bay. Non-N₂ fixing cyanobacteria, such as Planktothrix and Microcystis, thrive on chemically reduced forms of nitrogen, such as ammonium (NH₄⁺) and urea. Ammonium regeneration and potential uptake rates and total microbial community demand for NH₄⁺ were quantified in Sandusky Bay. Potential NH₄⁺ uptake rates in the light increased from June to August at all stations. Dark uptake rates also increased seasonally and, by the end of August, were on par with light uptake rates. Regeneration rates followed a similar pattern and were significantly higher in August than June. Ammonium uptake kinetics during a Planktothrix-dominated bloom in Sandusky Bay and a Microcystis-dominated bloom in Maumee Bay were also compared. The highest half saturation constant (K_m) in Sandusky Bay was measured in June and decreased throughout the season. In contrast, K_m values in Maumee Bay were lowest at the beginning of summer and increased in October. A significant increase in V_max in Sandusky Bay was observed between July and the end of August, reflective of intense competition for depleted NH₄⁺. Metatranscriptome results from Sandusky Bay show a shift from cyanophycin synthetase (luxury NH₄⁺ uptake; cphA1) expression in early summer to cyanophycinase (intracellular N mobilization; cphB/cphA2) expression in August, supporting the interpretation that the microbial community is nitrogen-starved in late summer. Combined, our results show that, in late summer, when nitrogen concentrations are low, cyanoHABs in Sandusky Bay rely on regenerated NH₄⁺ to support growth and toxin production. Increased dark NH₄⁺ uptake late in summer suggests an important heterotrophic contribution to NH₄⁺ depletion in the phycosphere. Kinetic experiments in the two bays suggest a competitive advantage for Planktothrix over Microcystis in Sandusky Bay due to its higher affinity for NH₄⁺ at low concentrations.

Reduced forms of nitrogen are a driver of non-nitrogen-fixing harmful cyanobacterial blooms and toxicity in Lake Erie

Western Lake Erie (WLE) experiences anthropogenic eutrophication and annual, toxic cyanobacterial blooms of non-nitrogen (N) fixing Microcystis. Numerous studies have shown that bloom biomass is correlated with an increased proportion of soluble reactive phosphorus loading from the Maumee River. Long term monitoring shows that the proportion of the annual Maumee River N load of non-nitrate N, or total Kjeldahl nitrogen (TKN), has also increased significantly (Spearman's ρ = 0.68, p = 0.001) over the last few decades and is also significantly correlated to cyanobacterial bloom biomass (Spearman's ρ = 0.64, p = 0.003). The ratio of chemically reduced N to oxidized N (TKN:NO3) concentrations was also compared to extracted chlorophyll and phycocyanin concentrations from all weekly sampling stations within WLE from 2009 to 2015. Both chlorophyll (Spearman's ρ = 0.657, p < 0.0001) and phycocyanin (Spearman's ρ = 0.714, p < 0.0001) were significantly correlated with TKN:NO3. This correlation between the increasing fraction of chemically reduced N from the Maumee River and increasing bloom biomass demonstrates the urgent need to control N loading, in addition to current P load reductions, to WLE and similar systems impacted by non-N-fixing, toxin-producing cyanobacteria.

Tree water-use strategies to improve stormwater retention performance of biofiltration systems

Biofiltration systems are highly valued in urban landscapes as they remove pollutants from stormwater runoff whilst contributing to a reduction in runoff volumes. Integrating trees in biofilters may improve their runoff retention performance, as trees have greater transpiration than commonly used sedge or herb species. High transpiration rates will rapidly deplete retained water, creating storage capacity prior to the next runoff event. However, a tree with high transpiration rates in a biofilter system will likely be frequently exposed to drought stress. Selecting appropriate tree species therefore requires an understanding of how different trees use water and how they respond to substrate drying. We selected 20 tree species and quantified evapotranspiration (ET) and drought stress (leaf water potential; Ψ) in relation to substrate water content. To compare species, we developed metrics which describe: (i) maximum rates of ET under well-watered conditions, (ii) the sensitivity of ET and (iii) the response of Ψ to declining substrate water content. Using these three metrics, we classified species into three groups: risky, balanced or conservative. Risky and balanced species showed high maximum ET, whereas conservative species always had low ET. As substrates dried, the balanced species down-regulated ET to delay the onset of drought stress; whereas risky species did not. Therefore, balanced species with high ET are more likely to improve the retention performance of biofiltration systems without introducing significant drought risk. This classification of tree water use strategies can be easily integrated into water balance models and improve tree species selection for biofiltration systems.

It Takes Two to Tango: When and Where Dual Nutrient (N & P) Reductions Are Needed to Protect Lakes and Downstream Ecosystems

Preventing harmful algal blooms (HABs) is needed to protect lakes and downstream ecosystems. Traditionally, reducing phosphorus (P) inputs was the prescribed solution for lakes, based on the assumption that P universally limits HAB formation. Reduction of P inputs has decreased HABs in many lakes, but was not successful in others. Thus, the "P-only" paradigm is overgeneralized. Whole-lake experiments indicate that HABs are often stimulated more by combined P and nitrogen (N) enrichment rather than N or P alone, indicating that the dynamics of both nutrients are important for HAB control. The changing paradigm from P-only to consideration of dual nutrient control is supported by studies indicating that (1) biological N fixation cannot always meet lake ecosystem N needs, and (2) that anthropogenic N and P loading has increased dramatically in recent decades. Sediment P accumulation supports long-term internal loading, while N may escape via denitrification, leading to perpetual N deficits. Hence, controlling both N and P inputs will help control HABs in some lakes and also reduce N export to downstream N-sensitive ecosystems. Managers should consider whether balanced control of N and P will most effectively reduce HABs along the freshwater-marine continuum.

Mitigating cyanobacterial harmful algal blooms in aquatic ecosystems impacted by climate change and anthropogenic nutrients

Mitigating the global expansion of cyanobacterial harmful blooms (CyanoHABs) is a major challenge facing researchers and resource managers. A variety of traditional (e.g., nutrient load reduction) and experimental (e.g., artificial mixing and flushing, omnivorous fish removal) approaches have been used to reduce bloom occurrences. Managers now face the additional effects of climate change on watershed hydrologic and nutrient loading dynamics, lake and estuary temperature, mixing regime, internal nutrient dynamics, and other factors. Those changes favor CyanoHABs over other phytoplankton and could influence the efficacy of control measures. Virtually all mitigation strategies are influenced by climate changes, which may require setting new nutrient input reduction targets and establishing nutrient-bloom thresholds for impacted waters. Physical-forcing mitigation techniques, such as flushing and artificial mixing, will need adjustments to deal with the ramifications of climate change. Here, we examine the suite of current mitigation strategies and the potential options for adapting and optimizing them in a world facing increasing human population pressure and climate change.

A process for energy-efficient high-solids fed-batch enzymatic liquefaction of cellulosic biomass

The enzymatic hydrolysis of cellulosic biomass is a key step in the biochemical production of fuels and chemicals. Economically feasible large-scale implementation of the process requires operation at high solids loadings, i.e., biomass concentrations >15% (w/w). At increasing solids loadings, however, biomass forms a high viscosity slurry that becomes increasingly challenging to mix and severely mass transfer limited, which limits further addition of solids. To overcome these limitations, we developed a fed-batch process controlled by the yield stress and its changes during liquefaction of the reaction mixture. The process control relies on an in-line, non-invasive magnetic resonance imaging (MRI) rheometer to monitor real-time evolution of yield stress during liquefaction. Additionally, we demonstrate that timing of enzyme addition relative to biomass addition influences process efficiency, and the upper limit of solids loading is ultimately limited by end-product inhibition as soluble glucose and cellobiose accumulate in the liquid phase.

Controlling cyanobacterial blooms in hypertrophic Lake Taihu, China: will nitrogen reductions cause replacement of non-N2 fixing by N2 fixing taxa?

Excessive anthropogenic nitrogen (N) and phosphorus (P) inputs have caused an alarming increase in harmful cyanobacterial blooms, threatening sustainability of lakes and reservoirs worldwide. Hypertrophic Lake Taihu, China’s third largest freshwater lake, typifies this predicament, with toxic blooms of the non-N₂ fixing cyanobacteria Microcystis spp. dominating from spring through fall. Previous studies indicate N and P reductions are needed to reduce bloom magnitude and duration. However, N reductions may encourage replacement of non-N₂ fixing with N₂ fixing cyanobacteria. This potentially counterproductive scenario was evaluated using replicate, large (1000 L), in-lake mesocosms during summer bloom periods. N+P additions led to maximum phytoplankton production. Phosphorus enrichment, which promoted N limitation, resulted in increases in N₂ fixing taxa (Anabaena spp.), but it did not lead to significant replacement of non-N₂ fixing with N₂ fixing cyanobacteria, and N₂ fixation rates remained ecologically insignificant. Furthermore, P enrichment failed to increase phytoplankton production relative to controls, indicating that N was the most limiting nutrient throughout this period. We propose that Microcystis spp. and other non-N₂ fixing genera can maintain dominance in this shallow, highly turbid, nutrient-enriched lake by outcompeting N₂ fixing taxa for existing sources of N and P stored and cycled in the lake. To bring Taihu and other hypertrophic systems below the bloom threshold, both N and P reductions will be needed until the legacy of high N and P loading and sediment nutrient storage in these systems is depleted. At that point, a more exclusive focus on P reductions may be feasible.

A shift in the archaeal nitrifier community in response to natural and anthropogenic disturbances in the northern Gulf of Mexico

The Gulf of Mexico is affected by hurricanes and suffers seasonal hypoxia. The Deepwater Horizon oil spill impacted every trophic level in the coastal region. Despite their importance in bioremediation and biogeochemical cycles, it is difficult to predict the responses of microbial communities to physical and anthropogenic disturbances. Here, we quantify sediment ammonia-oxidizing archaeal (AOA) community diversity, resistance and resilience, and important geochemical factors after major hurricanes and the oil spill. Dominant AOA archetypes correlated with different geochemical factors, suggesting that different AOA are constrained by distinct parameters. Diversity was lowest after the hurricanes, showing weak resistance to physical disturbances. However, diversity was highest during the oil spill and coincided with a community shift, suggesting a new alternative stable state sustained for at least 1 year. The new AOA community was not significantly different from that at the spill site 1 year after the spill. This sustained shift in nitrifier community structure may be a result of oil exposure.

Genetic and clinical factors predict lithium's effects on PER2 gene expression rhythms in cells from bipolar disorder patients

Bipolar disorder (BD) is associated with abnormal circadian rhythms. In treatment responsive BD patients, lithium (Li) stabilizes mood and reduces suicide risk. Li also affects circadian rhythms and expression of 'clock genes' that control them. However, the extent to which BD, Li and the circadian clock share common biological mechanisms is unknown, and there have been few direct measurements of clock gene function in samples from BD patients. Hence, the role of clock genes in BD and Li treatment remains unclear. Skin fibroblasts from BD patients (N=19) or healthy controls (N=19) were transduced with Per2::luc, a rhythmically expressed, bioluminescent circadian clock reporter gene, and rhythms were measured for 5 consecutive days. Rhythm amplitude and period were compared between BD cases and controls with and without Li. Baseline period was longer in BD cases than in controls. Li 1 mM increased amplitude in controls by 36%, but failed to do so in BD cases. Li 10 mM lengthened period in both BD cases and controls. Analysis of clock gene variants revealed that PER3 and RORA genotype predicted period lengthening by Li, whereas GSK3β genotype predicted rhythm effects of Li, specifically among BD cases. Analysis of BD cases by clinical history revealed that cells from past suicide attempters were more likely to show period lengthening with Li 1 mM. Finally, Li enhanced the resynchronization of damped rhythms, suggesting a mechanism by which Li could act therapeutically in BD. Our work suggests that the circadian clock's response to Li may be relevant to molecular pathology of BD.

Endovascular Treatment of the Common Femoral Artery for Limb Ischemia

Objective:

To determine the short- and mid-term outcomes of percutaneous endovascular common femoral artery (CFA) revascularization (eCFR) of the CFA.

Methods:

A review of patients who underwent eCFR for limb ischemia between 2006 and 2012 was performed. Limb salvage, patient survival, survival free from reintervention, and survival free from amputation rates were determined. Median (range) follow-up was 28 (1-71) months.

Results:

In all, 115 patients underwent 121 eCFR for CFA occlusion (n = 13) or stenosis (n = 108); 109 (90%) were technically successful and 7 (6%) had significant perioperative complications; access site hematoma (n = 2) and thromboembolism (n = 5). Thirty-day mortality and amputation rates were 2.5% and 0.8%, respectively. The 1- and 3-year limb salvage rates were 97% and 97%, respectively. The 1- and 3-year survival free from reintervention rates were 77% and 57%, respectively. The 1- and 3-year survival free from amputation rates were 84% and 70%, respectively.

Conclusion:

These novel data demonstrate that eCFR is a durable treatment for patients with limb ischemia associated with CFA disease.

Isolated Percutaneous Transluminal Angioplasty of the Profunda Femoris Artery for Limb Ischemia

Objective:

To compare the outcome of endovascular profunda femoral artery revascularization (ePFR) with ePFR and concurrent endovascular femoropopliteal revascularization (eFPR).

Methods:

A retrospective review of the consecutive patients with PFA and femoropopliteal vaso-occulsive disease who underwent ePFR or ePFR + eFPR for severe limb ischemia was performed.

Results:

A total of 18 ePFRs and 26 ePFR + eFPRs were performed; 17 (94%) ePFRs and 22 (85%) ePFR + eFPRs were technically successful. The 12-month survival free from amputation and reintervention rates following isolated ePFR were 78% and 72%, respectively, and following ePFR + eFPR were 96% and 81%, respectively. There was no significant difference in the survival free from amputation ( P = .4) or reintervention ( P = .91) rates between the 2 groups.

Conclusion:

These contemporary data suggest isolated ePFRs and ePFR + eFPRs are associated with good and comparable early limb salvage rates.

Functional genetic variation in the Rev-Erbα pathway and lithium response in the treatment of bipolar disorder

Bipolar disorder (BD) is characterized by disruptions in circadian rhythms such as sleep and daily activity that often normalize after lithium treatment in responsive patients. As lithium is known to interact with the circadian clock, we hypothesized that variation in circadian 'clock genes' would be associated with lithium response in BD. We determined genotype for 16 variants in seven circadian clock genes and conducted a candidate gene association study of these in 282 Caucasian patients with BD who were previously treated with lithium. We found that a variant in the promoter of NR1D1 encoding Rev-Erbα (rs2071427) and a second variant in CRY1 (rs8192440) were nominally associated with good treatment response. Previous studies have shown that lithium regulates Rev-Erbα protein stability by inhibiting glycogen synthase kinase 3β (GSK3β). We found that GSK3β genotype was also suggestive of a lithium response association, but not statistically significant. However, when GSK3β and NR1D1 genotypes were considered together, they predicted lithium response robustly and additively in proportion to the number of response-associated alleles. Using lymphoblastoid cell lines from patients with BD, we found that both the NR1D1 and GSK3β variants are associated with functional differences in gene expression. Our findings support a role for Rev-Erbα in the therapeutic mechanism of lithium and suggest that the interaction between Rev-Erbα and GSK3β may warrant further study.

Controlling harmful cyanobacterial blooms in a hyper-eutrophic lake (Lake Taihu, China): the need for a dual nutrient (N & P) management strategy

Harmful cyanobacterial blooms, reflecting advanced eutrophication, are spreading globally and threaten the sustainability of freshwater ecosystems. Increasingly, non-nitrogen (N(2))-fixing cyanobacteria (e.g., Microcystis) dominate such blooms, indicating that both excessive nitrogen (N) and phosphorus (P) loads may be responsible for their proliferation. Traditionally, watershed nutrient management efforts to control these blooms have focused on reducing P inputs. However, N loading has increased dramatically in many watersheds, promoting blooms of non-N(2) fixers, and altering lake nutrient budgets and cycling characteristics. We examined this proliferating water quality problem in Lake Taihu, China's 3rd largest freshwater lake. This shallow, hyper-eutrophic lake has changed from bloom-free to bloom-plagued conditions over the past 3 decades. Toxic Microcystis spp. blooms threaten the use of the lake for drinking water, fisheries and recreational purposes. Nutrient addition bioassays indicated that the lake shifts from P limitation in winter-spring to N limitation in cyanobacteria-dominated summer and fall months. Combined N and P additions led to maximum stimulation of growth. Despite summer N limitation and P availability, non-N(2) fixing blooms prevailed. Nitrogen cycling studies, combined with N input estimates, indicate that Microcystis thrives on both newly supplied and previously-loaded N sources to maintain its dominance. Denitrification did not relieve the lake of excessive N inputs. Results point to the need to reduce both N and P inputs for long-term eutrophication and cyanobacterial bloom control in this hyper-eutrophic system.

Percutaneous ultrasound-guided thrombin injection for the treatment of iatrogenic femoral artery pseudoaneurysms

PURPOSE

To audit our experience with ultrasound-guided thrombin injection for the treatment of iatrogenic femoral artery pseudoaneurysms.

METHODS

A retrospective study of 85 consecutive patients undergoing percutaneous ultrasound-guided thrombin injection of post-catheterization femoral pseudoaneurysms during the period January 2002 to May 2007.

RESULTS

Pseudoaneurysms had a mean maximum diameter of 3.3 cm (range 1.0-7.6 cm) and a mean neck width of 3.4mm (range 1.0-7.0mm). No statistically significant correlation existed between maximum diameter and neck width (Kendall's rank correlation tau b=-0.09, p=0.5). The median dose of thrombin injected was 425 U (range 100-1500 U). The procedure resulted in complete sac thrombosis in 81 (95%) patients. Seventy-nine pseudoaneurysms thrombosed immediately after one injection, whereas two required a second thrombin injection. There were no procedural complications. The maximum diameter of the pseudoaneurysm was predictive of procedural success (Wilcoxon's rank sum test, p=0.001) and of the 5 patients with a pseudoaneurysm measuring ≥6 cm, ultrasound-guided thrombin injection was unsuccessful in 4 (4/5 versus 0/80, p<0.0001, Fisher's exact test). Three of these necessitated implantation of a stent-graft, whereas one required repeated thrombin injection and coil placement. In contrast, the pseudoaneurysm neck width did not seem to relate to the success of the procedure.

CONCLUSION

Percutaneous ultrasound-guided thrombin injection of is a quick, effective and safe treatment for iatrogenic femoral pseudoaneurysms. For larger pseudoaneurysms, although it is worth attempting more than one thrombin injection, endovascular repair may eventually be required.

Oil migration in chocolate-peanut butter paste confectionery as a function of chocolate formulation

Migration of oil from high oil content filling to the chocolate coating can result in undesirable quality changes in filled chocolate confectionery products. The objective of this study was to monitor and model peanut oil migration in a 2-layer chocolate-peanut butter paste model confectionery. Spatial and temporal oil content changes were evaluated using magnetic resonance imaging. Five formulations of chocolate, which varied in chocolate particle size, milk fat content, and emulsifier level, were assessed at 2 temperatures, 20 and 30 degrees C. The spatial and temporal experimental data were modeled using a Fickian-based diffusion model, fitting for the diffusion coefficient, D, over a time frame of 17 d. Values of the diffusion coefficient ranged from 1.82 to 3.23 x 10(-11) m2/s for the chocolate formulations stored at 30 degrees C. No significant mass transfer took place in the 20 degrees C samples over the experimental time frame. This study describes the dynamic nature of the interface between the chocolate and peanut butter paste layers, quantifies the mass transfer from the peanut butter paste to the chocolate, and reinforces the importance of temperature control.

Is Infrainguinal Bypass Grafting Successful Following Failed Angioplasty?

OBJECTIVES

Angioplasty is often used in the management of lower limb ischaemia and can reduce the need for infrainguinal bypass in some patients. There is an associated failure rate with this technique and bypass surgery is often used in this situation as a secondary limb salvage procedure. We aimed to evaluate the outcome of infrainguinal bypass grafting following failed attempt at angioplasty.

METHODS

All cases of infrainguinal bypass at a single centre over a seven year period were identified and notes reviewed. Cases were divided into four groups according to their indication for surgery; acute ischaemia, chronic critical ischaemia, failed angioplasty and an 'other' group including aneurysmal disease and claudicants. The failed angioplasty group was compared with the other three groups. Survival analysis was performed using Kaplan Meier curves and groups compared in terms of long term patency and survival.

RESULTS

Primary patency was 61.2% in the failed angioplasty group at 12 months compared with 60.6% in the other groups (P=1.11). There was also no significant difference in primary patency at 60 months (50% vs 40.6%, P=0.26). Survival at 12 months was also comparable between the groups (failed angioplasty group 74.2% compared with 77.3% in the other groups, P=0.662) as was 60 months survival (33.3% and 35.4% respectively, P=0.166).

DISCUSSION

In this study, outcome of infrainguinal bypass following failed angioplasty was comparable to outcome of surgery performed for another indication. This paper supports the use of distal bypass surgery for limb salvage in cases where minimal access techniques have failed.

The value of urgent carotid surgery for crescendo transient ischemic attacks

OBJECTIVE

This study audited operative risk in patients undergoing urgent carotid surgery for crescendo transient ischemic attacks (TIAs).

METHODS

Interrogation of the vascular unit database (January 1992 to July 2004) identified 42 patients operated on urgently for crescendo TIAs, which were defined as>or=3 TIAs within the preceding 7 days. Stroke, death, and any major cardiac events were analyzed.

RESULTS

Thirty-nine patients underwent conventional endarterectomy, and three underwent interposition vein bypass. Crescendo TIA patients had sustained a median of five TIAs (range, 3 to 20) in the 7 days before surgery. Three patients died or had a stroke after surgery, for a combined stroke/death rate of 7%. This compares with 2.4% in 1000 patients undergoing elective carotid endarterectomy in this unit during the same time period. The combined stroke/death/major cardiac event rate was 14% (n=6).

CONCLUSIONS

The combined risk of neurologic and cardiac complications after urgent carotid surgery for crescendo TIA is higher than that expected after elective cases but is still acceptable considering the natural history of patients with unstable neurologic symptoms.

Carotid plaque instability and ischemic symptoms are linked to immaturity of microvessels within plaques

BACKGROUND

Instability and rupture of carotid atherosclerotic plaques leads to thromboemboli and ischemic symptoms. Angiogenesis occurs within atherosclerotic plaques, and plaque vulnerability and symptomatic carotid disease have been associated with increased numbers of microvessels. In addition to microvessel number, it is possible that the phenotypes of intraplaque vessels could influence plaque stability. To test this, the morphology and maturity of vessels within plaques from symptomatic and asymptomatic patients was determined.

METHODS

Carotid plaques were collected after endarterectomy from a cohort of 13 asymptomatic patients and 30 symptomatic patients. Plaques were sectioned and immunostained for the presence of endothelial cells, vascular smooth muscle cells, macrophages, and vascular endothelial growth factor. Sections were assessed for microvessel morphology, maturity as judged by smooth muscle cell cover, and the presence of vascular endothelial growth factor and macrophages.

RESULTS

Two types of vascular structure were observed within plaques, microvessels and dilated, highly irregular multilobular vessels. These irregular dysmorphic vessels were found almost exclusively in plaques from symptomatic patients. The dysmorphic vessels lacked smooth muscle cells and were highly immature. Plaques also contained vascular endothelial growth factor, and this was observed adjacent to the dysmorphic vessels. This growth factor was found colocalized with macrophages.

CONCLUSIONS

Symptomatic carotid plaques contain abnormal, immature microvessels similar to those found in tumors and healing wounds. Such vessels could contribute to plaque instability by acting as sites of vascular leakage by inflammatory cell recruitment. The immature vessels within plaques may be therapeutic targets for promoting plaque stabilization.

Duplex imaging immediately prior to carotid endarterectomy

INTRODUCTION

In this centre, angiography is used only in selected cases, whilst duplex ultrasound (DU) is the main imaging method prior to carotid endarterectomy (CEA). DU has no associated morbidity and so can be repeated immediately before surgery to detect changes in the carotid plaque or degree of stenosis.

PATIENTS AND METHODS

We retrospectively examined our Vascular Surgery Audit database for the last 500 patients admitted for CEA. In each case, the DU scan was repeated immediately before surgery.

RESULTS

From 500 admissions, repeat DU immediately prior to surgery detected 8 (1.6%) situations where CEA would no longer have been an appropriate intervention. In four cases, the degree of stenosis was found to be less than 70% on the repeat scan - in three cases the internal carotid artery (ICA) had occluded or sub-occluded and in one case there was a dissection of the ICA plaque.

CONCLUSIONS

DU can be repeated, with no associated morbidity, immediately prior to surgery. Such a practice changes management decisions in 1.6% of admissions for CEA, allowing surgery unjustified by current evidence to be avoided. This policy also serves several other important purposes: it is a method of internal validation, provides a means of improving training of vascular technologists and of achieving quality assurance in DU techniques.

Endovascular Abdominal Aortic Aneurysm Repair in the Presence of a Kidney Transplant: Therapeutic Considerations

Abdominal aortic aneurysm (AAA) repair in the presence of a kidney transplant can be extremely challenging, as it carries significant risks of renal ischemia. Endovascular repair is an attractive option, as it can be performed with little or no impairment of renal arterial flow. We describe the endovascular management of a recurrent AAA in a patient with a functioning renal transplant using a custom-made aorto-uni-iliac device. We discuss the planning and the potential problems of the technique.

Estuarine microbial food web patterns in a Lake Erie coastal wetland

Composition and distribution of planktonic protists were examined relative to microbial food web dynamics (growth, grazing, and nitrogen cycling rates) at the Old Woman Creek (OWC) National Estuarine Research Reserve during an episodic storm event in July 2003. More than 150 protistan taxa were identified based on morphology. Species richness and microbial biomass measured via microscopy and flow cytometry increased along a stream-lake (Lake Erie) transect and peaked at the confluence. Water column ammonium (NH4+) uptake (0.06 to 1.82 microM N h(-1)) and regeneration (0.04 to 0.55 microM N h(-1)) rates, measured using 15NH4+ isotope dilution, followed the same pattern. Large light/dark NH4+ uptake differences were observed in the hypereutrophic OWC interior, but not at the phosphorus-limited Lake Erie site, reflecting the microbial community structural shift from net autotrophic to net heterotrophic. Despite this shift, microbial grazers (mostly choreotrich ciliates, taxon-specific growth rates up to 2.9 d(-1)) controlled nanophytoplankton and bacteria at all sites by consuming 76 to 110% and 56 to 97% of their daily production, respectively, in dilution experiments. Overall, distribution patterns and dynamics of microbial communities in OWC resemble those in marine estuaries, where plankton productivity increases along the river-sea gradient and reaches its maximum at the confluence.

Comparing denitrification estimates for a Texas estuary by using acetylene inhibition and membrane inlet mass spectrometry

Characterizing denitrification rates in aquatic ecosystems is essential to understanding how systems may respond to increased nutrient loading. Thus, it is important to ensure the precision and accuracy of the methods employed for measuring denitrification rates. The acetylene (C2H2) inhibition method is a simple technique for estimating denitrification. However, potential problems, such as inhibition of nitrification and incomplete inhibition of nitrous oxide reduction, may influence rate estimates. Recently, membrane inlet mass spectrometry (MIMS) has been used to measure denitrification in aquatic systems. Comparable results were obtained with MIMS and C2H2 inhibition methods when chloramphenicol was added to C2H2 inhibition assay mixtures to inhibit new synthesis of denitrifying enzymes. Dissolved-oxygen profiles indicated that surface layers of sediment cores subjected to the MIMS flowthrough incubation remained oxic whereas cores incubated using the C2H2 inhibition methods did not. Analysis of the microbial assemblages before and after incubations indicated significant changes in the sediment surface populations during the long flowthrough incubation for MIMS analysis but not during the shorter incubation used for the C2H2 inhibition method. However, bacterial community changes were also small in MIMS cores at the oxygen transition zone where denitrification occurs. The C2H2 inhibition method with chloramphenicol addition, conducted over short incubation intervals, provides a cost-effective method for estimating denitrification, and rate estimates are comparable to those obtained by the MIMS method.

Noninvasive augmentation of microvessel number in patients with peripheral vascular disease

OBJECTIVE

Therapeutic angiogenesis has great potential for the treatment of ischemic diseases. One possible route for noninvasive induction of microvessels has recently been suggested by the finding that subcontractile electrical stimulation induces increased vascularization in animals. The present study tests the ability of such stimulation to augment microvessel number in patients with peripheral vascular disease.

DESIGN OF STUDY

Overall, 36 patients were randomly assigned to control (n = 12) and treatment (n = 24) groups. Patients in the treatment group received localized subcontractile electrical stimulation on the feet of their ischemic limbs for three 60-minute periods each day over a 6-week period. Microvessel density was determined by capillary microscopy before treatment, at 3 and 6 weeks during treatment, and 4 weeks after completion. Transcutaneous oxygen tension was also determined at this site.

RESULTS

Microvessel density determined by capillary microscopy was significantly increased (1.25-fold, P <.005) during and after treatment in patients receiving electrical stimulation. Transcutaneous oxygen tension was similarly increased in the treated patients (1.24-fold, P <.05). No changes were observed in these parameters in untreated patients examined in parallel.

CONCLUSION

Localized subcontractile electrical stimulation can increase microvessel density and tissue perfusion in patients with peripheral vascular disease.

Low atmospheric pressure is associated with rupture of abdominal aortic aneurysms

INTRODUCTION

the rate of rupture of abdominal aortic aneurysms (AAAs) has been shown to have a seasonal variation with more ruptures occurring during the winter months. One of the main meterological changes between the seasons is a change in atmospheric pressure. The aim of this study was to investigate whether there was any relationship between atmospheric pressure and the incidence of AAA rupture.

METHODS

all cases of ruptured AAA admitted to a single hospital over a ten year period were identified from hospital records. Daily atmospheric pressure readings from the nearest weather recording station to the hospital were obtained for the same period. Cases were only included if rupture could be confirmed by reviewing the patients case-notes.

RESULTS

admission rates for ruptured AAA showed a monthly variation with the highest rate in December and the lowest in August. There was a statistically significant correlation between the number of cases admitted in any particular month and the mean atmospheric pressure for the previous month. Neither daily minimum, maximum or mean pressure, weekly mean pressure or daily pressure variability were significantly different between those days when a ruptured AAA was admitted and those when no ruptured AAA was admitted.

CONCLUSIONS

low atmospheric pressure is associated with increased rate of AAA rupture. The method by which this change in pressure precipitates rupture cannot be determined from this study.

Tie-1 receptor tyrosine kinase endodomain interaction with SHP2: potential signalling mechanisms and roles in angiogenesis

The endothelial receptor tyrosine kinase plays an essential role in vascular development where it is thought to be required for vessel maturation and stabilization. The ligands responsible for activating Tie-1, its signalling pathways and specific cellular functions are however not known. As with some other receptor tyrosine kinases, Tie-1 is subject to extracellular proteolytic cleavage generating a membrane bound receptor fragment comprising the intracellular and transmembrane domains. Here we examine the signalling potential of this Tie-1 endodomain. We show that the Tie-1 endodomain has poor ability to induce tyrosine phosphorylation. However, on formation the endodomain physically associates with a number of tyrosine phosphorylated signalling intermediates including the tyrosine phosphatase and adaptor protein SHP2. The assembly of this multimolecular complex is consistent with the endodomain having a ligand-independent signalling role in the endothelial cell. The potential roles of ectodomain cleavage and cleavage activated signalling in regulating microvessel stability in angiogenesis, vessel remodelling and regression are considered.

Systemic diseases associated with various types of retinal vein occlusion

PURPOSE

To investigate systemic diseases associated with various types of retinal vein occlusion.

METHODS

We investigated prospectively in 1090 consecutive patients with retinal vein occlusion, almost all Caucasian (consistent with the racial pattern here), the prevalence of associated systemic disorders before or at the onset of various types of retinal vein occlusion. The patients were categorized into six types of retinal vein occlusion based on defined criteria: nonischemic and ischemic central retinal vein occlusion, nonischemic and ischemic hemi-central retinal vein occlusion, and major and macular branch retinal vein occlusion. The patients had a detailed ophthalmic and systemic evaluation according to our protocol. For data analysis, patients were divided into three age groups: young (younger than 45 years), middle-aged (45 to 64 years), and elderly (65 years or older). The observed prevalence rates of major systemic diseases were compared among central retinal vein occlusion, hemi-central retinal vein occlusion, and branch retinal vein occlusion using a polytomous logistic regression analysis adjusting for gender and age. Logistic regression adjusting for age and gender was also used to compare the observed prevalence of systemic disease between nonischemic and ischemic in central retinal vein occlusion and hemi-central retinal vein occlusion and between major and macular branch retinal vein occlusion. These observed prevalence rates were also compared with those expected in a gender-matched and age-matched control population from estimates from the US National Center for Health Statistics.

RESULTS

There was a significantly higher prevalence of arterial hypertension in branch retinal vein occlusion compared with central retinal vein occlusion (P < .0001) and hemi-central retinal vein occlusion (P = .028). Branch retinal vein occlusion also had a significantly higher prevalence of peripheral vascular disease (P = .0002), venous disease (P = .011), peptic ulcer (P = .031), and other gastrointestinal disease (P < .0001) compared with central retinal vein occlusion. The proportion of patients with branch retinal vein occlusion with cerebrovascular disease was also significantly (P = .049) greater than that of the combined group of patients with central retinal vein occlusion and patients with hemi-central retinal vein occlusion. There was no significant difference in prevalence of any systemic disease between central retinal vein occlusion and hemi-central retinal vein occlusion. A significantly greater prevalence of arterial hypertension (P = .025) and diabetes mellitus (P = .011) was present in the ischemic central retinal vein occlusion compared with the nonischemic central retinal vein occlusion. Similarly, arterial hypertension (P = .0002) and ischemic heart disease (P = .048) were more prevalent in major branch retinal vein occlusion than in macular branch retinal vein occlusion. Relative to the US white control population, the combined group of patients with central retinal vein occlusion and patients with hemi-central retinal vein occlusion had a higher prevalence of arterial hypertension (P < .0001), peptic ulcer (P < .0001), diabetes mellitus (in ischemic type only, P < .0001), and thyroid disorder (P < .0001). The patients with branch retinal vein occlusion showed a greater prevalence of arterial hypertension (P < or = .005), cerebrovascular disease (P = .007), chronic obstructive pulmonary disease (P = .012), peptic ulcer (P < .0001), diabetes (in young only, P = .0005), and thyroid disorder (P = .003) compared with the US white control population.

CONCLUSIONS

The findings of our study revealed that a variety of systemic disorders may be present in association with different types of retinal vein occlusion and in different age groups, and that their relative prevalence differs significantly, so that the common practice of generalizing about these disorders for the entire group of patients with retinal vein occlusion can be misleading. The presence of a particular associated systemic disease does not necessarily imply a cause-and-effect relationship with that type of retinal vein occlusion; the particular disease may or may not be one of the risk factors in a multifactorial scenario predisposing an eye to develop a particular type of retinal vein occlusion. Based on our study, we think that apart from a routine medical evaluation, an extensive and expensive workup for systemic diseases is unwarranted in the vast majority of patients with retinal vein occlusion.

The Prince Edward Island Conceptual Model for Nursing: a nursing perspective of primary health care

The philosophy of primary health care (PHC) recognizes that health is a product of individual, social, economic, and political factors and that people have a right and a duty, individually and collectively, to participate in the course of their own health. The majority of nursing models cast the client in a dependent role and do not conceptualize health in a social, economic, and political context. The Prince Edward Island Conceptual Model for Nursing is congruent with the international move towards PHC. It guides the nurse in practising in the social and political environment in which nursing and health care take place. This model features a nurse/client partnership, the goal being to encourage clients to act on their own behalf. The conceptualization of the environment as the collective influence of the determinants of health gives both nurse and client a prominent position in the sociopolitical arena of health and health care.

Angiogenesis and the atherosclerotic carotid plaque: an association between symptomatology and plaque morphology

PURPOSE

Symptomatic carotid disease resulting from generation of thromboemboli has been associated with plaque instability and intraplaque hemorrhage. These features of the lesion could be influenced by the fragility and position of neovessels within the plaque. The purpose of this study was to determine whether any association exists between neovessel density, position, morphology, and thromboembolic sequelae.

METHODS

Carotid endarterectomy samples were collected from 15 asymptomatic patients with greater than 80% stenoses and from 13 highly symptomatic patients who had suffered ipsilateral carotid stenotic events within 1 month of surgery. Both groups were matched for gender, age, risk factors, degree of carotid artery stenosis, and plaque size. Samples were stained with hematoxylin/eosin and van Geison. Immunohistochemistry was performed by using an endothelial specific antibody to CD31. Plaques were assessed for histologic characteristics, and neovessels were counted and characterized by size, site, and shape.

RESULTS

There were significantly more neovessels in plaques (P <.00001) and fibrous caps (P <.0001) in symptomatic compared with asymptomatic plaques. Neovessels in symptomatic plaques were larger (P <.004) and more irregular. There was a significant increase in plaque necrosis and rupture in symptomatic plaques. Plaque hemorrhage and rupture were associated with more neovessels within the plaque (P <.017, P <.001) and within the fibrous cap (P <.046, P <.004). Patients with preoperative and intraoperative embolization had significantly more plaque and fibrous cap neovessels (P <.025, P <.001).

CONCLUSION

Symptomatic carotid disease is associated with increased neovascularization within the atherosclerotic plaque and fibrous cap. These vessels are larger and more irregular and may contribute to plaque instability and the onset of thromboembolic sequelae.

Potential roles of metalloprotease mediated ectodomain cleavage in signaling by the endothelial receptor tyrosine kinase Tie-1

The orphan receptor tyrosine kinase Tie-1 is expressed predominantly in endothelial cells. Expression of this receptor is increased in physiologic angiogenesis and pathologic situations including tumor growth and arteriovenous malformations. Tie-1 is essential for vascular development where it acts in later stages of angiogenesis to suppress endothelial activation and stabilize the newly formed vessel. Stimulation of protein kinase C in endothelial cells results in endoproteolytic cleavage of Tie-1, releasing the extracellular ligand-binding domain of the receptor. We show that this is mediated by a metalloprotease. Immunoprecipitation and immunoblotting of lysates prepared from human placentas confirm that Tie-1 truncation occurs in vivo. We propose cleavage of this receptor may be a mechanism for inducing vessel destabilization by preventing ligand-activated signaling through Tie-1. Using an antibody that recognizes the carboxy terminus of the intracellular domain, we show that the Tie-1 endodomain formed on cleavage persists as a cell-associated fragment for several hours. Subcellular fractionation reveals this tyrosine kinase containing receptor fragment to be localized in the membrane fraction of the cell. Immunoprecipitation with antibodies recognizing phosphotyrosine demonstrates that cleavage of Tie-1 stimulates association of newly generated endodomain with cellular phosphoproteins. Furthermore, there was a marked induction of tyrosine phosphorylation of several proteins after PMA-induced endodomain generation. These data indicate that ectodomain cleavage may be a mechanism for down-regulating ligand-induced signaling through Tie-1 while activating an alternative ligand-independent signaling pathway in endothelial cells. Ectodomain cleavage occurs in some other receptor tyrosine kinases. We suggest that rather than solely being a means of down-regulating receptor activity, ectodomain cleavage may be a novel way for a receptor to switch between two alternative signaling pathways.

Variations on the slotted-tube resonator: rectangular and elliptical coils

Two designs (one rectangular, one elliptical) are proposed as efficient alternatives to noncylindrical birdcage RF coils. These designs are based on the slotted-tube resonator and their performance relies on the natural current distribution in the conductors due to the eddy current effects at high frequencies. A Finite element method program, solving the full set of Maxwell's equations, has been employed to accurately characterize and optimize the field homogeneity of the proposed noncylindrical coils. The optimum configuration of each design is presented, taking into account the effect of the RF shield. The proposed designs are compared to several configurations presented in the literature. Two coils (one rectangular, one elliptical) have been constructed and tested in a 0.6 T imaging system. A rectangular coil has been built to operate at 300 MHz. MR images substantiate the usefulness of these coils.

Vascular surgical society of great britain and ireland: angiogenesis and the atherosclerotic carotid plaque: association between symptomatology and plaque morphology

BACKGROUND: Symptomatic carotid disease due to thromboembolism has been associated with acute plaque instability and intraplaque haemorrhage. These features may be influenced by the fragility and position of plaque neovessels. The purpose of this study was, therefore, to determine whether any association existed between neovessel density, position, morphology and thromboembolic sequelae. METHODS: Carotid endarterectomy (CEA) samples were collected from 15 asymptomatic patients with greater than 80 per cent stenosis and from 13 patients with greater than 80 per cent stenosis and symptoms within 30 days of CEA. Groups were matched for sex, age, risk factors and plaque size. Samples were stained with haematoxylin and eosin, and Van Gieson stains. An endothelial-specific antibody to CD31 was used for immunohistochemistry. Plaques were assessed for histological characteristics while neovessels were counted and characterized by size, site and shape. RESULTS: There were more neovessels in plaques (P < 0.00001) and fibrous caps (P < 0.0001) from symptomatic than asymptomatic patients. Symptomatic plaque neovessels were larger in size (P < 0.004) and more irregular in shape. There was a significant increase in plaque necrosis and rupture in symptomatic plaques. Plaque haemorrhage and rupture were associated with more neovessels within the plaque (P < 0.02, P < 0. 001) and fibrous cap (P < 0.05, P < 0.004). Patients with preoperative or intraoperative embolization had more plaque and fibrous cap neovessels (P < 0.03, P < 0.001). CONCLUSION: Symptomatic carotid disease is associated with increased neovascularization within the atherosclerotic plaque and fibrous cap; these vessels appear larger in size, more irregular in shape and may contribute to plaque instability and onset of thromboembolic events.

Experience of supraclavicular exploration and decompression for treatment of thoracic outlet syndrome

The purpose of this study was to assess the symptomatic outcome of patients with thoracic outlet syndrome who underwent decompression of the thoracic outlet. In our unit we prefer the supraclavicular approach, performing anterior scalenectomy with excision of fibrous bands or cervical ribs if present. Operative details were gained by theater logbook and case note review. Over a 6-year period, 31 patients (37 limbs) underwent thoracic outlet decompression. Of the 37 affected limbs, the indications for surgery were a combination of both neurological and vascular symptoms in 24 patients (65%), neurological symptoms in 24 (65%), and 4 patients (11%) had vascular symptoms alone. All patients were assessed for postoperative outcome either at out-patient clinics or by personal contact. From the results of this study we concluded that supraclavicular scalenectomy and cervical rib excision with selective first rib excision is a safe and effective procedure for most patients with thoracic outlet syndrome.

Prevalence of true vein graft aneurysms: implications for aneurysm pathogenesis

BACKGROUND

Circumstantial evidence suggests that arterial aneurysms have a different cause than atherosclerosis and may form part of a generalized dilating diathesis. The aim of this study was to compare the rates of spontaneous aneurysm formation in vein grafts performed either for popliteal aneurysms or for occlusive disease. The hypothesis was that if arterial aneurysms form a part of a systemic process, then the rates of vein graft aneurysms should be higher for patients with popliteal aneurysms than for patients with lower limb ischemia caused by atherosclerosis.

METHODS

Infrainguinal vein grafting procedures performed from 1990 to 1995 were entered into a prospective audit and graft surveillance program. Aneurysmal change was defined as a focal increase in the graft diameter of 1.5 cm or greater, excluding false aneurysms and dilatations after graft angioplasty.

RESULTS

During the study period, 221 grafting procedures were performed in 200 patients with occlusive disease and 24 grafting procedures were performed in 21 patients with popliteal aneurysms. Graft surveillance revealed spontaneous aneurysm formation in 10 of the 24 bypass grafts (42%) for popliteal aneurysms but in only 4 of the 221 grafting procedures (2%) that were performed for chronic lower limb ischemia.

CONCLUSION

This study provides further evidence that aneurysmal disease is a systemic process, and this finding has clinical implications for the treatment of popliteal aneurysms.