Publications by authors named "William K Cornwell"

83 Publications

Managing Atrial Fibrillation in Patients With Heart Failure and Reduced Ejection Fraction: A Scientific Statement From the American Heart Association.

Circ Arrhythm Electrophysiol 2021 Jun 15;14(6):HAE0000000000000078. Epub 2021 Jun 15.

Atrial fibrillation and heart failure with reduced ejection fraction are increasing in prevalence worldwide. Atrial fibrillation can precipitate and can be a consequence of heart failure with reduced ejection fraction and cardiomyopathy. Atrial fibrillation and heart failure, when present together, are associated with worse outcomes. Together, these 2 conditions increase the risk of stroke, requiring oral anticoagulation in many or left atrial appendage closure in some. Medical management for rate and rhythm control of atrial fibrillation in heart failure remain hampered by variable success, intolerance, and adverse effects. In multiple randomized clinical trials in recent years, catheter ablation for atrial fibrillation in patients with heart failure and reduced ejection fraction has shown superiority in improving survival, quality of life, and ventricular function and reducing heart failure hospitalizations compared with antiarrhythmic drugs and rate control therapies. This has resulted in a paradigm shift in management toward nonpharmacological rhythm control of atrial fibrillation in heart failure with reduced ejection fraction. The primary objective of this American Heart Association scientific statement is to review the available evidence on the epidemiology and pathophysiology of atrial fibrillation in relation to heart failure and to provide guidance on the latest advances in pharmacological and nonpharmacological management of atrial fibrillation in patients with heart failure and reduced ejection fraction. The writing committee's consensus on the implications for clinical practice, gaps in knowledge, and directions for future research are highlighted.
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http://dx.doi.org/10.1161/HAE.0000000000000078DOI Listing
June 2021

Global abundance estimates for 9,700 bird species.

Proc Natl Acad Sci U S A 2021 May;118(21)

Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, UNSW Sydney, Sydney, NSW 2052, Australia.

Quantifying the abundance of species is essential to ecology, evolution, and conservation. The distribution of species abundances is fundamental to numerous longstanding questions in ecology, yet the empirical pattern at the global scale remains unresolved, with a few species' abundance well known but most poorly characterized. In large part because of heterogeneous data, few methods exist that can scale up to all species across the globe. Here, we integrate data from a suite of well-studied species with a global dataset of bird occurrences throughout the world-for 9,700 species (∼92% of all extant species)-and use missing data theory to estimate species-specific abundances with associated uncertainty. We find strong evidence that the distribution of species abundances is log left skewed: there are many rare species and comparatively few common species. By aggregating the species-level estimates, we find that there are ∼50 billion individual birds in the world at present. The global-scale abundance estimates that we provide will allow for a line of inquiry into the structure of abundance across biogeographic realms and feeding guilds as well as the consequences of life history (e.g., body size, range size) on population dynamics. Importantly, our method is repeatable and scalable: as data quantity and quality increase, our accuracy in tracking temporal changes in global biodiversity will increase. Moreover, we provide the methodological blueprint for quantifying species-specific abundance, along with uncertainty, for any organism in the world.
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http://dx.doi.org/10.1073/pnas.2023170118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8166167PMC
May 2021

Is color data from citizen science photographs reliable for biodiversity research?

Ecol Evol 2021 May 30;11(9):4071-4083. Epub 2021 Mar 30.

Evolution and Ecology Research Centre School of Biological, Earth and Environmental Sciences University of New South Wales Sydney NSW Australia.

Color research continuously demands better methods and larger sample sizes. Citizen science (CS) projects are producing an ever-growing geo- and time-referenced set of photographs of organisms. These datasets have the potential to make a huge contribution to color research, but the reliability of these data need to be tested before widespread implementation.We compared the difference between color extracted from CS photographs with that of color extracted from controlled lighting conditions (i.e., the current gold standard in spectrometry) for both birds and plants. First, we tested the ability of CS photographs to quantify interspecific variability by assessing > 9,000 CS photographs of 537 Australian bird species with controlled museum spectrometry data. Second, we tested the ability of CS photographs to quantify intraspecific variability by measuring petal color data for two plant species using seven methods/sources with varying levels of control.For interspecific questions, we found that by averaging out variability through a large sample size, CS photographs capture a large proportion of across species variation in plumage color within the visual part of the spectrum (  = 0.68-0.71 for RGB space and 0.72-0.77 for CIE-LAB space). Between 12 and 14 photographs per species are necessary to achieve this averaging effect for interspecific studies. Unsurprisingly, the CS photographs taken with commercial cameras failed to capture information in the UV part of the spectrum. For intraspecific questions, decreasing levels of control increase the color variation but averaging larger sample sizes can partially mitigate this, aside from particular issues related to saturation and irregularities in light capture.CS photographs offer a very large sample size across space and time which offers statistical power for many color research questions. This study shows that CS photographs contain data that lines up closely with controlled measurements within the visual spectrum if the sample size is large enough, highlighting the potential of CS photographs for both interspecific and intraspecific ecological or biological questions. With regard to analyzing color in CS photographs, we suggest, as a starting point, to measure multiple random points within the ROI of each photograph for both patterned and unpatterned patches and approach the recommended sample size of 12-14 photographs per species for interspecific studies. Overall, this study provides groundwork in analyzing the reliability of a novel method, which can propel the field of studying color forward.
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http://dx.doi.org/10.1002/ece3.7307DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8093748PMC
May 2021

The Society of Thoracic Surgeons Intermacs 2020 Annual Report.

Ann Thorac Surg 2021 03 16;111(3):778-792. Epub 2021 Jan 16.

Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, Michigan. Electronic address:

The Society of Thoracic Surgeons (STS)-Interagency Registry for Mechanically Assisted Circulatory Support (Intermacs) 2020 Annual Report reviews outcomes on 25,551 patients undergoing primary isolated continuous-flow left ventricular assist device (LVAD) implantation between 2010 and 2019. In 2019, 3198 primary LVADs were implanted, which is the highest annual volume in Intermacs history. Compared with the previous era (2010-2014), patients who received an LVAD in the most recent era (2015-2019) were more likely to be African American (26.8% vs 22.9%, P < .0001) and more likely to be bridged to durable LVAD with temporary mechanical support devices (36.8% vs 26.0%, P < .0001). In 2019, 50% of patients were INTERMACS Profile 1 or 2 before durable LVAD, and 73% received an LVAD as destination therapy. Magnetic levitation technology has become the predominant design, accounting for 77% of devices in 2019. The 1- and 2-year survival in the most recent era has improved compared with 2010 to 2014 (82.3% and 73.1% vs 80.5% and 69.1%, respectively; P < .0001). Major bleeding and infection continue to be the leading adverse events. Incident stroke has declined in the current era to 12.7% at 1 year. STS-Intermacs research publications are highlighted, and the new quality initiatives are introduced.
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http://dx.doi.org/10.1016/j.athoracsur.2020.12.038DOI Listing
March 2021

Impairments in Blood Pressure Regulation and Cardiac Baroreceptor Sensitivity Among Patients With Heart Failure Supported With Continuous-Flow Left Ventricular Assist Devices.

Circ Heart Fail 2021 01 19;14(1):e007448. Epub 2021 Jan 19.

Department of Medicine-Cardiology (C.S., G.C., M.B., A.V.A., E.W., W.K.C.), University of Colorado Anschutz Medical Campus, Aurora.

Background: Continuous-flow (CF) left ventricular assist devices (LVADs) improve outcomes for patients with advanced heart failure (HF). However, the lack of a physiological pulse predisposes to side-effects including uncontrolled blood pressure (BP), and there are little data regarding the impact of CF-LVADs on BP regulation.

Methods: Twelve patients (10 males, 60±11 years) with advanced heart failure completed hemodynamic assessment 2.7±4.1 months before, and 4.3±1.3 months following CF-LVAD implantation. Heart rate and systolic BP via arterial catheterization were monitored during Valsalva maneuver, spontaneous breathing, and a 0.05 Hz repetitive squat-stand maneuver to characterize cardiac baroreceptor sensitivity. Plasma norepinephrine levels were assessed during head-up tilt at supine, 30 and 60. Heart rate and BP were monitored during cardiopulmonary exercise testing.

Results: Cardiac baroreceptor sensitivity, determined by Valsalva as well as Fourier transformation and transfer function gain of Heart rate and systolic BP during spontaneous breathing and squat-stand maneuver, was impaired before and following LVAD implantation. Norepinephrine levels were markedly elevated pre-LVAD and improved-but remained elevated post-LVAD (supine norepinephrine pre-LVAD versus post-LVAD: 654±437 versus 323±164 pg/mL). BP increased during cardiopulmonary exercise testing post-LVAD, but the magnitude of change was modest and comparable to the changes observed during the pre-LVAD cardiopulmonary exercise testing.

Conclusions: Among patients with advanced heart failure with reduced ejection fraction, CF-LVAD implantation is associated with modest improvements in autonomic tone, but persistent reductions in cardiac baroreceptor sensitivity. Exercise-induced increases in BP are blunted. These findings shed new light on mechanisms for adverse events such as stroke, and persistent reductions in functional capacity, among patients supported by CF-LVADs. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03078972.
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http://dx.doi.org/10.1161/CIRCHEARTFAILURE.120.007448DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7818348PMC
January 2021

Right ventricular function and cardiopulmonary performance among patients with heart failure supported by durable mechanical circulatory support devices.

J Heart Lung Transplant 2021 Feb 22;40(2):128-137. Epub 2020 Nov 22.

Division of Cardiology, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado. Electronic address:

Background: Patients with continuous-flow left ventricular assist devices (CF-LVADs) experience limitations in functional capacity and frequently, right ventricular (RV) dysfunction. We sought to characterize RV function in the context of global cardiopulmonary performance during exercise in this population.

Methods: A total of 26 patients with CF-LVAD (aged 58 ± 11 years, 23 males) completed a hemodynamic assessment with either conductance catheters (Group 1, n = 13) inserted into the right ventricle to generate RV pressure‒volume loops or traditional Swan‒Ganz catheters (Group 2, n = 13) during invasive cardiopulmonary exercise testing. Hemodynamics were collected at rest, 2 sub-maximal levels of exercise, and peak effort. Breath-by-breath gas exchange parameters were collected by indirect calorimetry. Group 1 participants also completed an invasive ramp test during supine rest to determine the impact of varying levels of CF-LVAD support on RV function.

Results: In Group 1, pump speed modulations minimally influenced RV function. During upright exercise, there were modest increases in RV contractility during sub-maximal exercise, but there were no appreciable increases at peak effort. Ventricular‒arterial coupling was preserved throughout the exercise. In Group 2, there were large increases in pulmonary arterial, left-sided filling, and right-sided filling pressures during sub-maximal and peak exercises. Among all participants, the cardiac output‒oxygen uptake relationship was preserved at 5.8:1. Ventilatory efficiency was severely abnormal at 42.3 ± 11.6.

Conclusions: Patients with CF-LVAD suffer from limited RV contractile reserve; marked elevations in pulmonary, left-sided filling, and right-sided filling pressures during exercise; and severe ventilatory inefficiency. These findings explain mechanisms for persistent reductions in functional capacity in this patient population.
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http://dx.doi.org/10.1016/j.healun.2020.11.009DOI Listing
February 2021

Reducing intracranial pressure by reducing central venous pressure: assessment of potential countermeasures to spaceflight-associated neuro-ocular syndrome.

J Appl Physiol (1985) 2021 02 3;130(2):283-289. Epub 2020 Dec 3.

Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.

Spaceflight-associated neuro-ocular syndrome (SANS) involves unilateral or bilateral optic disc edema, widening of the optic nerve sheath, and posterior globe flattening. Owing to posterior globe flattening, it is hypothesized that microgravity causes a disproportionate change in intracranial pressure (ICP) relative to intraocular pressure. Countermeasures capable of reducing ICP include thigh cuffs and breathing against inspiratory resistance. Owing to the coupling of central venous pressure (CVP) and intracranial pressure, we hypothesized that both ICP and CVP will be reduced during both countermeasures. In four male participants (32 ± 13 yr) who were previously implanted with Ommaya reservoirs for treatment of unrelated clinical conditions, ICP was measured invasively through these ports. Subjects were healthy at the time of testing. CVP was measured invasively by a peripherally inserted central catheter. Participants breathed through an impedance threshold device (ITD, -7 cmHO) to generate negative intrathoracic pressure for 5 min, and subsequently, wore bilateral thigh cuffs inflated to 30 mmHg for 2 min. Breathing through an ITD reduced both CVP (6 ± 2 vs. 3 ± 1 mmHg; = 0.02) and ICP (16 ± 3 vs. 12 ± 1 mmHg; = 0.04) compared to baseline, a result that was not observed during the free breathing condition (CVP, 6 ± 2 vs. 6 ± 2 mmHg, = 0.87; ICP, 15 ± 3 vs. 15 ± 4 mmHg, = 0.68). Inflation of the thigh cuffs to 30 mmHg caused no meaningful reduction in CVP in all four individuals (5 ± 4 vs. 5 ± 4 mmHg; = 0.1), coincident with minimal reduction in ICP (15 ± 3 vs. 14 ± 4 mmHg; = 0.13). The application of inspiratory resistance breathing resulted in reductions in both ICP and CVP, likely due to intrathoracic unloading. Spaceflight causes pathological changes in the eye that may be due to the absence of gravitational unloading of intracranial pressure (ICP) under microgravity conditions commonly referred to as spaceflight-associated neuro-ocular syndrome (SANS), whereby countermeasures aimed at lowering ICP are necessary. These data show that impedance threshold breathing acutely reduces ICP via a reduction in central venous pressure (CVP). Whereas, acute thigh cuff inflation, a popular known spaceflight-associated countermeasure, had little effect on ICP and CVP.
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http://dx.doi.org/10.1152/japplphysiol.00786.2020DOI Listing
February 2021

Whole body passive heating versus dynamic lower body exercise: a comparison of peripheral hemodynamic profiles.

J Appl Physiol (1985) 2021 01 22;130(1):160-171. Epub 2020 Oct 22.

Department of Sport Science, University of Innsbruck, Innsbruck, Austria.

Passive heating has emerged as a therapeutic intervention for the treatment and prevention of cardiovascular disease. Like exercise, heating increases peripheral artery blood flow and shear rate, which is thought to be a primary mechanism underpinning endothelium-mediated vascular adaptation. However, few studies have compared the increase in arterial blood flow and shear rate between dynamic exercise and passive heating. In a fixed crossover design study, 15 moderately trained healthy participants (25.6 ± 3.4 yr) (5 female) underwent 30 min of whole body passive heating (42°C bath), followed on a separate day by 30 min of semi-recumbent stepping exercise performed at two workloads corresponding to the increase in cardiac output (Qc) (Δ3.72 L·min) and heart rate (HR) (Δ40 beats/min) recorded at the end of passive heating. At the same Qc (Δ3.72 L·min vs. 3.78 L·min), femoral artery blood flow (1,599 mL/min vs. 1,947 mL/min) ( = 0.596) and shear rate (162 s vs. 192 s) ( = 0.471) measured by ultrasonography were similar between passive heating and stepping exercise. However, for the same HR intensity, femoral blood flow (1,599 mL·min vs. 2,588 mL·min) and shear rate (161 s vs. 271 s) were significantly greater during exercise, compared with heating (both = <0.001). The results indicate that, for moderately trained individuals, passive heating increases common femoral artery blood flow and shear rate similar to low-intensity continuous dynamic exercise (29% V̇o); however, exercise performed at a higher intensity (53% V̇o) results in significantly larger shear rates toward the active skeletal muscle. Passive heating and exercise increase blood flow through arteries, generating a frictional force, termed shear rate, which is associated with positive vascular health. Few studies have compared the increase in arterial blood flow and shear rate elicited by passive heating with that elicited by dynamic continuous exercise. We found that 30 min of whole body passive hot-water immersion (42°C bath) increased femoral artery blood flow and shear rate equivalent to exercising at a moderate intensity (∼57% HR).
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http://dx.doi.org/10.1152/japplphysiol.00291.2020DOI Listing
January 2021

Rapidly mapping fire effects on biodiversity at a large-scale using citizen science.

Sci Total Environ 2021 Feb 11;755(Pt 2):142348. Epub 2020 Sep 11.

Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, UNSW Sydney, Sydney, NSW 2052, Australia; Ecology & Evolution Research Centre, School of Biological, Earth and Environmental Sciences, UNSW Sydney, Sydney, NSW 2052, Australia.

The unprecedented scale of the 2019-2020 eastern Australian bushfires exemplifies the challenges that scientists and conservation biologists face monitoring the effects on biodiversity in the aftermath of large-scale environmental disturbances. After a large-scale disturbance, conservation policy and management actions need to be both timely and informed by data. By working with the public, often widely spread out over such disturbed areas, citizen science offers a unique opportunity to collect data on biodiversity responses at the appropriate scale. We detail a citizen science project, hosted through iNaturalist, launched shortly after the 2019-2020 bushfire season in eastern Australia. It rapidly (1) provided accurate data on fire severity, relevant to future recovery; and (2) delivered data on a wide range (mosses to mammals) of biodiversity responses at a scale that matched the geographic extent of these fires.
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http://dx.doi.org/10.1016/j.scitotenv.2020.142348DOI Listing
February 2021

Shifts in fine root traits within and among species along a fine-scale hydrological gradient.

Ann Bot 2021 03;127(4):473-481

Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences, UNSW Sydney, Sydney, NSW, Australia.

Background And Aims: Lessons from above-ground trait ecology and resource economics theory may not be directly translatable to below-ground traits due to differences in function, trade-offs and environmental constraints. Here we examine root functional traits within and across species along a fine-scale hydrological gradient. We ask two related questions: (1) What is the relative magnitude of trait variation across the gradient for within- versus among-species variation? (2) Do correlations among below-ground plant traits conform with predictions from resource-economic spectrum theory?

Methods: We sampled four below-ground fine-root traits (specific root length, branching intensity, root tissue density and root dry matter content) and four above-ground traits (specific leaf area, leaf size, plant height and leaf dry matter content) in vascular plants along a fine-scale hydrological gradient within a wet heathland community in south-eastern Australia. Below-ground and above-ground traits were sampled both within and among species.

Key Results: Root traits shifted both within and among species across the hydrological gradient. Within- and among-species patterns for root tissue density showed similar declines towards the wetter end of the gradient. Other root traits showed a variety of patterns with respect to within- and among-species variation. Filtering of species has a stronger effect compared with the average within-species shift: the slopes of the relationships between soil moisture and traits were steeper across species than slopes of within species. Between species, below-ground traits were only weakly linked to each other and to above-ground traits, but these weak links did in some cases correspond with predictions from economic theory.

Conclusions: One of the challenges of research on root traits has been considerable intraspecific variation. Here we show that part of intraspecific root trait variation is structured by a fine-scale hydrological gradient, and that the variation aligns with among-species trends in some cases. Patterns in root tissue density are especially intriguing and may play an important role in species and individual response to moisture conditions. Given the importance of roots in the uptake of resources, and in carbon and nutrient turnover, it is vital that we establish patterns of root trait variation across environmental gradients.
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http://dx.doi.org/10.1093/aob/mcaa175DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7988525PMC
March 2021

Cardiac Emergencies in Patients with Left Ventricular Assist Devices.

Heart Fail Clin 2020 Jul;16(3):295-303

Department of Medicine-Cardiology, University of Colorado Anschutz Medical Campus, 12631 East 17th Avenue, B130, Office 7107, Aurora, CO 80045, USA. Electronic address:

Continuous-flow left ventricular assist devices are frequently used for management of patients with advanced heart failure with reduced ejection fraction. Although technologic advancements have contributed to improved outcomes, several complications arise over time. These complications result from several factors, including medication effects, physiologic responses to chronic exposure to circulatory support that is minimally/entirely nonpulsatile, and dysfunction of the device itself. Clinical presentation can range from chronic and indolent to acute, life-threatening emergencies. Several areas of uncertainty exist regarding best practices for managing complications; however, growing awareness has led to development of new guidelines to reduce risk and improve outcomes.
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http://dx.doi.org/10.1016/j.hfc.2020.02.003DOI Listing
July 2020

New insights into resting and exertional right ventricular performance in the healthy heart through real-time pressure-volume analysis.

J Physiol 2020 07 18;598(13):2575-2587. Epub 2020 May 18.

Department of Medicine, Division of Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.

Key Points: Despite growing interest in right ventricular form and function in diseased states, there is a paucity of data regarding characteristics of right ventricular function - namely contractile and lusitropic reserve, as well as ventricular-arterial coupling, in the healthy heart during rest, as well as submaximal and peak exercise. Pressure-volume analysis of the right ventricle, during invasive cardiopulmonary exercise testing, demonstrates that that the right heart has enormous contractile reserve, with a three- or fourfold increase in all metrics of contractility, as well as myocardial energy production and utilization. The healthy right ventricle also demonstrates marked augmentation in lusitropy, indicating that diastolic filling of the right heart is not passive. Rather, the right ventricle actively contributes to venous return during exercise, along with the muscle pump. Ventricular-arterial coupling is preserved during submaximal and peak exercise in the healthy heart.

Abstract: Knowledge of right ventricular (RV) function has lagged behind that of the left ventricle and historically, the RV has even been referred to as a 'passive conduit' of lesser importance than its left-sided counterpart. Pressure-volume (PV) analysis is the gold standard metric of assessing ventricular performance. We recruited nine healthy sedentary individuals free of any cardiopulmonary disease (42 ± 12 years, 78 ± 11 kg), who completed invasive cardiopulmonary exercise testing during upright ergometry, while using conductance catheters inserted into the RV to generate real-time PV loops. Data were obtained at rest, two submaximal levels of exercise below ventilatory threshold, to simulate real-world scenarios/activities of daily living, and maximal effort. Breath-by-breath oxygen uptake was determined by indirect calorimetry. During submaximal and peak exercise, there were significant increases in all metrics of systolic function by three- to fourfold, including cardiac output, preload recruitable stroke work, and maximum rate of pressure change in the ventricle (dP/dt ), as well as energy utilization as determined by stroke work and pressure-volume area. Similarly, the RV demonstrated a significant, threefold increase in lusitropic reserve throughout exercise. Ventricular-arterial coupling, defined by the quotient of end-systolic elastance and effective arterial elastance, was preserved throughout all stages of exercise. Maximal pressures increased significantly during exercise, while end-diastolic volumes were essentially unchanged. Overall, these findings demonstrate that the healthy RV is not merely a passive conduit, but actively participates in cardiopulmonary performance during exercise by accessing an enormous amount of contractile and lusitropic reserve, ensuring that VA coupling is preserved throughout all stages of exercise.
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http://dx.doi.org/10.1113/JP279759DOI Listing
July 2020

Exercise Capacity in Mechanically Supported Advanced Heart Failure Patients: It Is All About the Beat.

ASAIO J 2020 04;66(4):339-342

From the Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah.

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http://dx.doi.org/10.1097/MAT.0000000000001164DOI Listing
April 2020

Bionic women and men - Part 2: Arterial stiffness in heart failure patients implanted with left ventricular assist devices.

Exp Physiol 2020 05 22;105(5):755-758. Epub 2020 Apr 22.

School of Sport & Health Sciences, Cardiff Metropolitan University, Cardiff, UK.

New Findings: What is the topic of this review? This review discusses how implantation of continuous flow left ventricular assist devices impact arterial stiffness and outcome. What advances does it highlight? Not all patients implanted with continuous flow left ventricular assist devices show an increase in arterial stiffness. However, in those patients where arterial stiffness increases, levels of composite outcome (stroke, gastrointestinal bleeding, pump thrombosis and death) is significantly higher than those who's arterial stiffness does not increase.

Abstract: In parallel with the major advances in clinical care, technological advancements and implantation of mechanical circulatory support in patients with severe heart failure have resulted in these patients living longer. However, these patients are still at increased risk of stroke and gastrointestinal bleeding. The unique continuous flow produced by various left ventricular assist devices (LVADs) has been suggested as one potential reason for this increased risk of stroke and gastrointestinal bleeding. Furthermore, these continuous-flow (CF) devices challenge our understanding of circulatory blood pressure and flow regulation in relationship to organ health. In healthy pulsatile and dynamic systems, arterial stiffness is a major independent risk factor for stroke. However, to date, there are limited data regarding the impact of CF-LVAD therapy on arterial stiffness. The purpose of this report is to discuss the variable impact of CF-LVAD therapy on arterial stiffness and attempt to highlight some potential mechanisms linking these associations in this unique population.
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http://dx.doi.org/10.1113/EP088326DOI Listing
May 2020

Bionic women and men - Part 4: Cardiovascular, cerebrovascular and exercise responses among patients supported with left ventricular assist devices.

Exp Physiol 2020 05 18;105(5):763-766. Epub 2020 Mar 18.

Department of Medicine-Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.

New Findings: LVAD patients are predisposed to hypertension which may increase the risk of stroke. Hypertension may result from markedly elevated levels of sympathetic nerve activity, which occurs through a baroreceptor-mediated pathway in response to chronic exposure to a non-physiologic (and reduced) pulse. Cerebral autoregulatory processes appear to be preserved in the absence of a physiologic pulse. Nevertheless, the rate of ischemic/embolic and hemorrhagic stroke is unacceptably high and is a major cause of morbidity and mortality in these patients. Despite normalization of a resting cardiac output, LVAD patients suffer from persistent, severe reductions in functional capacity.

Abstract: Current generation left ventricular assist devices (LVADs) have led to significant improvements in survival compared to medical therapy alone, when used for management of patients with advanced heart failure. However, there are a number of side-effects associated with LVAD use, including hypertension, gastrointestinal bleeding, stroke, as well as persistent and severe limitations in functional capacity despite normalization of a resting cardiac output. These issues are, in large part, related to chronic exposure to a non-physiologic pulse, which contributes to a hyperadrenergic environment characterized by markedly elevated levels of sympathetic nerve activity through a baroreceptor-mediated pathway. In addition, these machines are unable to participate in, or contribute to, normal cardiovascular/autonomic reflexes that attempt to modulate flow through the body. Efforts to advance device technology and develop biologically sensitive devices may resolve these issues, and lead to further improvements in quality-of-life, functional capacity, and ultimately, survival, for the patients they support.
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http://dx.doi.org/10.1113/EP088325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7195248PMC
May 2020

Bionic women and men - Part 1: Cardiovascular lessons from heart failure patients implanted with left ventricular assist devices.

Exp Physiol 2020 05 3;105(5):749-754. Epub 2020 Apr 3.

School of Sport & Health Sciences, Cardiff Metropolitan University, Cardiff, CF5 2YB, UK.

New Findings: What is the topic of this review? Patients with advanced heart failure who are implanted with left ventricular assist devices (LVADs) present an opportunity to understand the human circulation under extreme conditions. What advances does it highlight? LVAD patients have a unique circulation that is characterized by a reduced or even absent arterial pulse. The remarkable survival of these patients is accompanied by circulatory complications, including stroke, gastrointestinal bleeding and right-heart failure. Understanding the mechanisms related to the complications in LVAD patients will help the patients and also advance our fundamental understanding of the human circulation in general.

Abstract: Some humans with chronic, advanced heart failure are surgically implanted with a left ventricular assist device (LVAD). Because the LVAD produces a continuous flow, a palpable pulse is often absent in these patients. This allows for a unique investigation of the human circulation and has created a controversy around the 'need' for a pulse. The medical debate has also generated a more generic, fundamental discussion into what is 'normal' arterial physiology and health. The comprehensive study and understanding of the arterial responses to drastically altered haemodynamics due to continuous-flow LVADs, at rest and during activity, presents an opportunity to significantly increase our current understanding of the fundamental components of arterial regulation (flow, blood pressure, sympathetic activity, endothelial function, pulsatility) in a way that could never have been studied previously. In a series of four articles, we summarize the talks presented at the symposium entitled 'Bionic women and men - Physiology lessons from implantable cardiac devices' presented at the 2019 Annual Meeting of The Physiological Society in Aberdeen, UK. The articles highlight the novel questions generated by physiological phenomena observed in LVAD patients and propose future areas of interest within the field of cardiovascular physiology.
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http://dx.doi.org/10.1113/EP088323DOI Listing
May 2020

Bionic women and men - Part 3: Right ventricular dysfunction in patients implanted with left ventricular assist devices.

Exp Physiol 2020 05 18;105(5):759-762. Epub 2020 Mar 18.

Department of Medicine - Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.

New Findings: What is the topic of this review? Right heart dysfunction remains a major adverse event in patients with end stage heart failure undergoing left ventricular assist device placement. This article reviews the pathophysiology and clinical considerations of right heart failure in this patient population. What advances does it highlight? This review highlights the anatomic and physiological peculiarities of the interplay between left and right heart function in patients undergoing LVAD therapy. These would allow us to further advance our understanding of right ventricular function.

Abstract: The adaptation of the right ventricular (RV) output to a left ventricular assist device (LVAD) often determines the fate of patients with pulmonary hypertension secondary to left heart failure. Pre-existing right heart dysfunction in patients with advanced left heart failure is the consequence of increased (arterial) afterload and not simply the consequence of myocardial disease. If unaccounted for, it has the potential of accelerating into clinical right heart failure after LVAD, leading to significant morbidity and mortality. After LVAD implantation, the RV has to face increased flow generated by the LVAD, cardiac arrhythmias and exaggerated functional interactions between both ventricles. Understanding the key physiological mechanisms of RV dysfunction in patients with end-stage heart failure will allow us to predict and therefore prevent RV failure after LVAD implantation.
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http://dx.doi.org/10.1113/EP088324DOI Listing
May 2020

TRY plant trait database - enhanced coverage and open access.

Glob Chang Biol 2020 01 31;26(1):119-188. Epub 2019 Dec 31.

Arizona State University, Tempe, AZ, USA.

Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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http://dx.doi.org/10.1111/gcb.14904DOI Listing
January 2020

From dangerous branches to urban banyan: Facilitating aerial root growth of Ficus rubiginosa.

PLoS One 2019 30;14(12):e0226845. Epub 2019 Dec 30.

School of Biological, Earth and Environmental Sciences, UNSW Sydney, Sydney, NSW, Australia.

Large urban trees have many benefits. However, falling branches pose a serious hazard to both people and infrastructure. In several tree species, aerial roots grow down from branches to the ground. These roots are capable of thickening to support the branches, lessening the risk of tree failure. Unfortunately, in urban environments most aerial roots die before reaching the ground. Here, we report a new method for encouraging aerial roots to reach the ground, developed by the second-year botany class at UNSW Sydney. Our class tested three experimental treatments on aerial roots of Ficus rubiginosa Desf. ex Vent. (Port Jackson Fig)-PVC pipes filled with sphagnum moss, PVC pipes filled with potting mix, and PVC pipes filled with sphagnum moss and topped with funnels to catch extra rainwater. All three treatments significantly improved aerial root growth, with 26 of the 30 (87%) treatment roots reaching the ground after one year compared to 0 of the 10 control roots. Our method was successful for roots up to 3 m above the ground, suggesting the potential growth rate of aerial roots is substantial when conditions are favourable. Our novel approach is an attractive and cost-effective alternative to slings and other artificial supports. This project is an example of using undergraduate practical classes to teach science while simultaneously addressing important real-world problems.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0226845PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6936823PMC
April 2020

Fungal functional ecology: bringing a trait-based approach to plant-associated fungi.

Biol Rev Camb Philos Soc 2020 04 25;95(2):409-433. Epub 2019 Nov 25.

Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, CA, 92697, U.S.A.

Fungi play many essential roles in ecosystems. They facilitate plant access to nutrients and water, serve as decay agents that cycle carbon and nutrients through the soil, water and atmosphere, and are major regulators of macro-organismal populations. Although technological advances are improving the detection and identification of fungi, there still exist key gaps in our ecological knowledge of this kingdom, especially related to function. Trait-based approaches have been instrumental in strengthening our understanding of plant functional ecology and, as such, provide excellent models for deepening our understanding of fungal functional ecology in ways that complement insights gained from traditional and -omics-based techniques. In this review, we synthesize current knowledge of fungal functional ecology, taxonomy and systematics and introduce a novel database of fungal functional traits (Fun ). Fun is built to interface with other databases to explore and predict how fungal functional diversity varies by taxonomy, guild, and other evolutionary or ecological grouping variables. To highlight how a quantitative trait-based approach can provide new insights, we describe multiple targeted examples and end by suggesting next steps in the rapidly growing field of fungal functional ecology.
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http://dx.doi.org/10.1111/brv.12570DOI Listing
April 2020

Optimizing future biodiversity sampling by citizen scientists.

Proc Biol Sci 2019 10 2;286(1912):20191487. Epub 2019 Oct 2.

Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, UNSW Sydney, Sydney, New South Wales 2052, Australia.

We are currently in the midst of Earth's sixth extinction event, and measuring biodiversity trends in space and time is essential for prioritizing limited resources for conservation. At the same time, the scope of the necessary biodiversity monitoring is overwhelming funding for professional scientific monitoring. In response, scientists are increasingly using citizen science data to monitor biodiversity. But citizen science data are 'noisy', with redundancies and gaps arising from unstructured human behaviours in space and time. We ask whether the information content of these data can be maximized for the express purpose of trend estimation. We develop and execute a novel framework which assigns every citizen science sampling event a marginal value, derived from the importance of an observation to our understanding of overall population trends. We then make this framework predictive, estimating the expected marginal value of future biodiversity observations. We find that past observations are useful in forecasting where high-value observations will occur in the future. Interestingly, we find high value in both 'hotspots', which are frequently sampled locations, and 'coldspots', which are areas far from recent sampling, suggesting that an optimal sampling regime balances 'hotspot' sampling with a spread across the landscape.
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http://dx.doi.org/10.1098/rspb.2019.1487DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6790778PMC
October 2019

Effect of acute and chronic xenon inhalation on erythropoietin, hematological parameters, and athletic performance.

J Appl Physiol (1985) 2019 12 15;127(6):1503-1510. Epub 2019 Aug 15.

Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.

This study aimed to assess the efficacy of acute subanesthetic dosages of xenon inhalation to cause erythropoiesis and determine the effect of chronic xenon dosing on hematological parameters and athletic performance. To assess the acute effects, seven subjects breathed three subanesthetic concentrations of xenon: 30% fraction of inspired xenon (Fi) for 20 min, 50% Fi for 5 min, and 70% Fi for 2 min. Erythropoietin (EPO) was measured at baseline, during, and after xenon inhalation. To determine the chronic effects, eight subjects breathed 70% Fi for 2 min on 7 consecutive days, and EPO, total blood, and plasma volume were measured. Phase II involved assessment of 12 subjects for EPO, total blood volume, maximal oxygen uptake, and 3-km time before and after random assignment to 4 wk of xenon or sham gas inhalation. Fi 50% and 70% stimulated an increase in EPO at 6 h [+2.3 mIU/mL; 95% confidence interval (CI) 0.1-4.5; = 0.038] and at 192 h postinhalation (+2.9 mIU/mL; 95% CI 0.6-5.1; = 0.017), respectively. Seven consecutive days of dosing significantly elevated plasma volume (+491 mL; 95% CI 194-789; = 0.002). Phase II showed no significant effect on EPO, hemoglobin mass, plasma volume, maximal oxygen uptake, or 3-km time. Acute exposure to subanesthetic doses of xenon caused a consistent increase in EPO, and 7 consecutive days of xenon inhalation significantly expanded plasma volume. However, this physiological response appeared to be transient, and 4 wk of xenon inhalation did not stimulate increases in plasma volume or erythropoiesis, leaving cardiorespiratory fitness and athletic performance unchanged. This is the first study to examine each element of the cascade by which xenon inhalation is purported to take effect, starting with measurement of the hypoxia-inducible factor effector, erythropoietin, to hemoglobin mass and blood volume and athletic performance. We found that acute exposure to xenon increased serum erythropoietin concentration, although major markers of erythropoiesis remained unchanged. While daily dosing significantly expanded plasma volume, no physiological or performance benefits were apparent following 4 wk of dosing.
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http://dx.doi.org/10.1152/japplphysiol.00289.2019DOI Listing
December 2019

Safety, hemodynamic effects, and detection of acute xenon inhalation: rationale for banning xenon from sport.

J Appl Physiol (1985) 2019 12 15;127(6):1511-1518. Epub 2019 Aug 15.

Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.

This study aimed to quantify the sedative effects, detection rates, and cardiovascular responses to xenon. On 3 occasions, participants breathed xenon (FXe 30% for 20 min; FXe 50% for 5 min; FXe 70% for 2 min) in a nonblinded design. Sedation was monitored by a board-certified anesthesiologist. During 70% xenon, participants were also verbally instructed to operate a manual value with time-to-task failure being recorded. Beat-by-beat hemodynamics were measured continuously by ECG, photoplethysmography, and transcranial Doppler. Over 48 h postadministration, xenon was measured in blood and urine by gas chromatography-mass spectrometry. Xenon caused variable levels of sedation and restlessness. Task failure of the self-operating value occurred at 60-90 s in most individuals. Over the first minute, 50% and 70% xenon caused a substantial reduction in total peripheral resistance ( < 0.05). All dosages caused an increase in cardiac output ( < 0.05). By the end of xenon inhalation, slight hypertension was observed after all three doses ( < 0.05), with an increase in middle cerebral artery velocity ( < 0.05). Xenon was consistently detected, albeit in trace amounts, up to 3 h after all three doses of xenon inhalation in blood and urine with variable results thereafter. Xenon inhalation caused sedation incompatible with self-operation of a breathing apparatus, thus causing a potential life-threatening condition in the absence of an anesthesiologist. Yet, xenon can only be reliably detected in blood and urine up to 3 h postacute dosing. Breathing xenon in dosages conceivable for doping purposes (FXe 30% for 20 min; FXe 50% for 5 min; FXe 70% for 2 min) causes an initial rapid fall in total peripheral resistance with tachycardia and thereafter a mild hypertension with elevated middle cerebral artery velocity. These dose duration intervals cause sedation that is incompatible with operating a breathing apparatus and can only be detected in blood and urine samples with a high probability for up to ~3 h.
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http://dx.doi.org/10.1152/japplphysiol.00290.2019DOI Listing
December 2019

Improving big citizen science data: Moving beyond haphazard sampling.

PLoS Biol 2019 06 27;17(6):e3000357. Epub 2019 Jun 27.

Australian Museum Research Institute, Australian Museum, Sydney, New South Wales, Australia.

Citizen science is mainstream: millions of people contribute data to a growing array of citizen science projects annually, forming massive datasets that will drive research for years to come. Many citizen science projects implement a "leaderboard" framework, ranking the contributions based on number of records or species, encouraging further participation. But is every data point equally "valuable?" Citizen scientists collect data with distinct spatial and temporal biases, leading to unfortunate gaps and redundancies, which create statistical and informational problems for downstream analyses. Up to this point, the haphazard structure of the data has been seen as an unfortunate but unchangeable aspect of citizen science data. However, we argue here that this issue can actually be addressed: we provide a very simple, tractable framework that could be adapted by broadscale citizen science projects to allow citizen scientists to optimize the marginal value of their efforts, increasing the overall collective knowledge.
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http://dx.doi.org/10.1371/journal.pbio.3000357DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6619805PMC
June 2019

Good neighbors aplenty: fungal endophytes rarely exhibit competitive exclusion patterns across a span of woody habitats.

Ecology 2019 09 24;100(9):e02790. Epub 2019 Jul 24.

Department of Biological Sciences, The George Washington University, Washington, D.C., 20052, USA.

Environmental forces and biotic interactions, both positive and negative, structure ecological communities, but their relative roles remain obscure despite strong theory. For instance, ecologically similar species, based on the principle of limiting similarity, are expected to be most competitive and show negative interactions. Specious communities that assemble along broad environmental gradients afford the most power to test theory, but the communities often are difficult to quantify. Microbes, specifically fungal endophytes of wood, are especially suited for testing community assembly theory because they are relatively easy to sample across a comprehensive range of environmental space with clear axes of variation. Moreover, endophytes mediate key forest carbon cycle processes, and although saprophytic fungi from dead wood typically compete, endophytic fungi in living wood may enhance success through cooperative symbioses. To classify interactions within endophyte communities, we analyzed fungal DNA barcode variation across 22 woody plant species growing in woodlands near Richmond, New South Wales, Australia. We estimated the response of endophytes to the measured wood environment (i.e., 11 anatomical and chemical wood traits) and each other using latent-variable models and identified recurrent communities across wood environments using model-based classification. We used this information to evaluate whether (1) co-occurrence patterns are consistent with strong competitive exclusion, and (2) a priori classifications by trophic mode and phylum distinguish taxa that are more likely to have positive vs. negative associations under the principle of limiting similarity. Fungal endophytes were diverse (mean = 140 taxa/sample), with differences in community composition structured by wood traits. Variation in wood water content and carbon concentration were associated with especially large community shifts. Surprisingly, after accounting for wood traits, fungal species were still more than three times more likely to have positive than negative co-occurrence patterns. That is, patterns consistent with strong competitive exclusion were rare, and positive interactions among fungal endophytes were more common than expected. Confirming the frequency of positive vs. negative interactions among fungal taxa requires experimental tests, and our findings establish clear paths for further study. Evidence to date intriguingly suggests that, across a wide range of wood traits, cooperation may outweigh combat for these fungi.
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http://dx.doi.org/10.1002/ecy.2790DOI Listing
September 2019

HeartMate II System Controller Failure Presenting as Driveline Fault With Repeated Pump Stoppages.

Circ Heart Fail 2019 07 19;12(7):e005738. Epub 2019 Jun 19.

Department of Surgery, Division of Cardiothoracic Surgery (J.C.C., J.D.P.), University of Colorado School of Medicine, Aurora.

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http://dx.doi.org/10.1161/CIRCHEARTFAILURE.118.005738DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6613777PMC
July 2019

Datastorr: a workflow and package for delivering successive versions of 'evolving data' directly into R.

Gigascience 2019 05;8(5)

Evolution & Ecology Research Centre, and School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney NSW 2052, Australia.

The sharing and re-use of data has become a cornerstone of modern science. Multiple platforms now allow easy publication of datasets. So far, however, platforms for data sharing offer limited functions for distributing and interacting with evolving datasets- those that continue to grow with time as more records are added, errors fixed, and new data structures are created. In this article, we describe a workflow for maintaining and distributing successive versions of an evolving dataset, allowing users to retrieve and load different versions directly into the R platform. Our workflow utilizes tools and platforms used for development and distribution of successive versions of an open source software program, including version control, GitHub, and semantic versioning, and applies these to the analogous process of developing successive versions of an open source dataset. Moreover, we argue that this model allows for individual research groups to achieve a dynamic and versioned model of data delivery at no cost.
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http://dx.doi.org/10.1093/gigascience/giz035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6506717PMC
May 2019

When to cut your losses: Dispersal allocation in an asexual filamentous fungus in response to competition.

Ecol Evol 2019 Apr 12;9(7):4129-4137. Epub 2019 Mar 12.

Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences University of New South Wales Sydney NSW Australia.

Fungal communities often form on ephemeral substrates and dispersal is critical for the persistence of fungi among the islands that form these metacommunities. Within each substrate, competition for space and resources is vital for the local persistence of fungi. The capacity to detect and respond by dispersal away from unfavorable conditions may confer higher fitness in fungi. Informed dispersal theory posits that organisms are predicted to detect information about their surroundings which may trigger a dispersal response. As such, we expect that fungi will increase allocation to dispersal in the presence of a strong competitor.In a laboratory setting, we tested how competition with other filamentous fungi affected the development of conidial pycnidiomata (asexual fruiting bodies) in over 10 days. was not observed to produce more asexual fruiting bodies or produce them earlier when experiencing interspecific competition with other filamentous fungi. However, we found that a trade-off existed between growth rate and allocation to dispersal. We also observed a defensive response to specific interspecific competitors in the form of hyphal melanization of the colony which may have an impact on the growth rate and dispersal trade-off.Our results suggest that have the capacity to detect and respond to competitors by changing their allocation to dispersal and growth. However, allocation to defence may come at a cost to growth and dispersal. Thus, it is likely that optimal life history allocation in fungi constrained to ephemeral resources will depend on the competitive strength of neighbors surrounding them.
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http://dx.doi.org/10.1002/ece3.5041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6467841PMC
April 2019

Device Therapy and Arrhythmia Management in Left Ventricular Assist Device Recipients: A Scientific Statement From the American Heart Association.

Circulation 2019 05;139(20):e967-e989

Left ventricular assist devices (LVADs) are an increasingly used strategy for the management of patients with advanced heart failure with reduced ejection fraction. Although these devices effectively improve survival, atrial and ventricular arrhythmias are common, predispose these patients to additional risk, and complicate patient management. However, there is no consensus on best practices for the medical management of these arrhythmias or on the optimal timing for procedural interventions in patients with refractory arrhythmias. Although the vast majority of these patients have preexisting cardiovascular implantable electronic devices or cardiac resynchronization therapy, given the natural history of heart failure, it is common practice to maintain cardiovascular implantable electronic device detection and therapies after LVAD implantation. Available data, however, are conflicting on the efficacy of and optimal device programming after LVAD implantation. Therefore, the primary objective of this scientific statement is to review the available evidence and to provide guidance on the management of atrial and ventricular arrhythmias in this unique patient population, as well as procedural interventions and cardiovascular implantable electronic device and cardiac resynchronization therapy programming strategies, on the basis of a comprehensive literature review by electrophysiologists, heart failure cardiologists, cardiac surgeons, and cardiovascular nurse specialists with expertise in managing these patients. The structure and design of commercially available LVADs are briefly reviewed, as well as clinical indications for device implantation. The relevant physiological effects of long-term exposure to continuous-flow circulatory support are highlighted, as well as the mechanisms and clinical significance of arrhythmias in the setting of LVAD support.
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http://dx.doi.org/10.1161/CIR.0000000000000673DOI Listing
May 2019

Delayed febrile response with bloodstream infections in patients with continuous-flow left ventricular assist devices.

J Investig Med 2019 03 29;67(3):653-658. Epub 2019 Jan 29.

Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.

Bloodstream infections (BSIs) are common in patients with continuous-flow left ventricular assist devices (CF-LVADs). Whether CF-LVADs modulate the febrile response to BSIs is unknown. We retrospectively compared the febrile response to BSIs in patients with heart failure (HF) with CF-LVADs versus a control population of patients with HF receiving inotropic infusions. BSIs were adjudicated using the Centers for Disease Control and Prevention and the National Healthcare Safety Network criteria. Febrile status (temperature ≥38°C, 100.4 °F), temperature at presentation with BSI, and the highest temperature within 72 hours (Tmax) were collected. We observed 59 BSIs in LVAD patients and 45 BSIs in controls. LVAD patients were more likely to be afebrile and to have a lower temperature at presentation than control (88% vs 58%, p=0.002, and 37°C ±0.7 vs 37.7°C ±1.0, p=0.0009, respectively). By 72 hours, the difference in afebrile status diminished (53% vs 44%, p=0.42), and the Tmax was similar between the LVAD and control groups (37.9°C±0.9 vs 38.2°C±0.8, respectively, p=0.10). In conclusion, at presentation with a BSI, the vast majority of CF-LVAD patients were afebrile, an event which occurred at a higher frequency when compared with patients with advanced HF on chronic inotropes via an indwelling venous catheter. These data alert clinicians to have a very low threshold to obtain blood cultures in CF-LVAD patients even in the absence of fever. Further study is needed to determine whether a delayed or diminished febrile response represents another pathophysiological consequence of CF-LVADs.
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http://dx.doi.org/10.1136/jim-2018-000893DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6391164PMC
March 2019