Xylem embolism spread is largely prevented by interconduit pit membranes until the majority of conduits are gas-filled

Xylem embolism resistance varies across species influencing drought tolerance, yet little is known about the determinants of the embolism resistance of an individual conduit. Here we conducted an experiment using the optical vulnerability method to test whether individual conduits have a specific water potential threshold for embolism formation and whether pre-existing embolism in neighbouring conduits alters this threshold. Observations were made on a diverse sample of angiosperm and conifer species through a cycle of dehydration, rehydration and subsequent dehydration to death. Upon rehydration after the formation of embolism, no refilling was observed. When little pre-existing embolism was present, xylem conduits had a conserved, individual embolism-resistance threshold that varied across the population of conduits. The consequence of a variable conduit-specific embolism threshold is that a small degree of pre-existing embolism in the xylem results in apparently more resistant xylem in subsequent dehydrations, particularly in angiosperms with vessels. While our results suggest that pit membranes separating xylem conduits are critical for maintaining a conserved individual conduit threshold for embolism when little pre-existing embolism is present, as the percentage of embolized conduits increases, gas movement, local pressure differences and connectivity between conduits increasingly contribute to embolism spread.

USPIO-SWI Shows Fingolimod Enhanced Alteplase Action on Angiographic Reperfusion in eMCAO Rats

BACKGROUND

Noninvasive evaluation of the status of cerebral arteriole perfusion remains a practical challenge in murine stroke models, because conventional magnetic resonance imaging (MRI) is no longer capable of capturing these very small vessels.

PURPOSE

To investigate the feasibility of ultrasmall superparamagnetic iron oxide particles (USPIO)-based susceptibility weighted imaging (SWI)-MRI (USPIO-SWI) and T2* map-MRI (USPIO-T2* map) for monitoring angiographic perfusion in stroke rats.

STUDY TYPE

A preclinical randomized controlled trial.

ANIMAL MODEL

Normal rats (N = 9), embolic middle cerebral artery occlusion (eMCAO) rats (N = 66).

FIELD STRENGTH/SEQUENCE

7 T; T2* map (multigradient echo), SWI (3D gradient echo).

ASSESSMENT

Experiment 1: To develop a method for angiographic reperfusion evaluation with USPIO-SWI. Normal rats were used to optimize the USPIO dosage (5.6, 16.8, and 56 mg/kg ferumoxytol) as well as scan time points for cerebral arterioles. Contrast-to-noise ratio (CNR) was measured. Stroke rats were further used and the number of visual cortical vessels were counted. Experiment 2: To examine whether fingolimod (lymphocytes inhibitor) enhances the action of tissue plasminogen activator (tPA) in eMCAO rats on cerebral angiographic reperfusion.

STATISTICAL TESTS

Mann-Whitney test and two way-ANOVA were used. P < 0.05 was considered statistically significant.

RESULTS

CNR values of cerebral cortical penetrating arteries in normal rats were significantly increased to 4.4 ± 0.5 (5.6 mg/kg), 6.1 ± 0.5 (16.8 mg/kg), and 3.4 ± 0.9 (56 mg/kg) after USPIO injection. The number of visual cortical vessels on USPIO-SWI images in ischemic regions was significantly less than in control regions (5 ± 2 vs. 56 ± 20) of eMCAO rats. Compared with eMCAO rats who received tPA only, eMCAO rats who received the combination of fingolimod and tPA exhibited significantly higher proportion of complete angiographic reperfusion (69% vs. 17%).

DATA CONCLUSION

This study supports the feasibility of angiographic perfusion evaluation with USPIO-SWI in stroke rats.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 1.

Timing surgery and hemorrhagic complications in endocarditis with concomitant cerebral complications

BACKGROUND

To date, limited studies have been conducted regarding the safe timing of valvular repair for infectious endocarditis (IE) in patients with radiographic findings consistent with embolic stroke or infectious intracranial aneurysm (IIA).

METHODS

A single-center, retrospective review of valvular surgeries for IE was performed (2011-2019). Outcomes for patients who underwent cranial image screening and those who did not were subsequently compared.

RESULTS

276 patients underwent valvular repair for IE; 186 (67.4%) were male. The mean age was 51.0 (17.4) years. Mean time from imaging to surgery was 7.5 days. 124 (44.9%) underwent baseline cranial imaging. Of these, 22 (17.7%) had findings concerning for ischemic stroke from embolic origin. 65 patients underwent baseline diagnostic cerebral angiography. 10 (15%) of these patients harbored an IIA. Four out of these 10 (40%) underwent intervention for an IIA. Two of the four who underwent intervention (50.0%) had ruptured IIAs. The remaining six (60%) patients with IIAs received treatment with antibiotics alone. None of the patients with IIAs suffered from symptomatic hemorrhage after valvular surgery. No significant difference in symptomatic hemorrhage after valvular surgery between those with ischemic embolic stroke compared to those without (ischemic stroke-4.5% vs. no ischemic stroke-1.0%; p = 0.32).

CONCLUSIONS

Patients with radiographic evidence of ischemic stroke from septic emboli can safely undergo valvular surgery for IE without increased risk of symptomatic hemorrhage. We advocate for baseline CTA screening to evaluate for IIA in patients who present with a primary diagnosis of IE and propose a management algorithm.

Asymptomatic cerebral emboli following carotid artery stenting: a diffusion-weighted MRI study

Background

Silent cranial embolism due to carotid artery stenting has been demonstrated to cause dementia, cognitive decline, and even ischemic stroke. The purpose of this study was to compare the periprocedural asymptomatic cranial embolism rates of different stent designs used for extracranial carotid stenosis with diffusion-weighted magnetic resonance imaging.

Methods

A total of 507 consecutive patients who underwent carotid artery stenting at our center from December 2010 to June 2020 (mean age, 66.4 ± 9.5) were analyzed retrospectively. The patients were divided into 3 groups as open-cell stent (334 patients), closed-cell stent (102 patients), and hybrid-cell stent (71 patients) groups. Diffusion-weighted magnetic resonance imaging was performed for the patients before and after carotid artery stenting and compared. The diffusion limitations of 3 stent groups on cranial diffusion-weighted magnetic resonance imaging were compared with one another.

Results

Periprocedural asymptomatic same-side microembolism, which was the primary endpoint of our study, was detected in 58 (17.4%) patients in the open-cell stent group, 6 (5.9%) patients in the closed-cell group, and 8 (11.3%) patients in the hybrid cell group, and overall in 72 (14.2%) patients. On diffusion-weighted magnetic resonance imaging, periprocedural asymptomatic same-side cranial embolism was found to be statistically significantly higher in the open-cell group compared to the other two groups (P = .011).

Conclusions

The result of this study showed us that the rate of same-side cranial embolism detected on cranial diffusion-weighted magnetic resonance imaging after carotid artery stenting performed with open-cell stent was higher than those of the carotid artery stenting procedure performed with closed-cell and hybrid-cell stents.

Left Ventricular Thrombus Formation in a Structurally and Functionally Normal Heart: A Case Report and Literature Review

Left ventricular (LV) thrombosis usually occurs as a complication of acute anterior myocardial infarction (MI) and dilated cardiomyopathy. It also occurs in patients with a hypercoagulable state. However, in the setting of normal systolic function, LV thrombi are extremely rare. We present a case of a healthy woman who had LV thrombus despite normal LV systolic function that presented as an acute aortoiliac embolism.

Acute embolisms in multiple arterial districts following Ad26.COV2-S vaccine

A case of multiple arterial thrombosis/embolisms in a 74-year-old Caucasian man with no other cardiovascular risk factors who received Ad26.COV2-S vaccine 16 days before is reported. The unusual presentation required a longer diagnostic workup. The clinical manifestations and the therapy-specific response suggest an unusual presentation of Vaccine-induced immune thrombotic thrombocytopenia (VITT).

In vivo monitoring of drought-induced embolism in Callitris rhomboidea trees reveals wide variation in branchlet vulnerability and high resistance to tissue death

Damage to the plant water transport system through xylem cavitation is known to be a driver of plant death in drought conditions. However, a lack of techniques to continuously monitor xylem embolism in whole plants in vivo has hampered our ability to investigate both how this damage propagates and the possible mechanistic link between xylem damage and tissue death. Using optical and fluorescence sensors, we monitored drought-induced xylem embolism accumulation and photosynthetic damage in vivo throughout the canopy of a drought-resistant conifer, Callitris rhomboidea, during drought treatments of c. 1 month duration. We show that drought-induced damage to the xylem can be monitored in vivo in whole trees during extended periods of water stress. Under these conditions, vulnerability of the xylem to cavitation varied widely among branchlets, with photosynthetic damage only recorded once > 90% of the xylem was cavitated. The variation in branchlet vulnerability has important implications for understanding how trees like C. rhomboidea survive drought, and the high resistance of branchlets to tissue damage points to runaway cavitation as a likely driver of tissue death in C. rhomboidea branch tips.

Paradoxical Cerebellar Embolism Associated with Platypnea-orthodeoxia Syndrome

Platypnea-orthodeoxia syndrome is a rare clinical entity characterized by dyspnea and arterial blood deoxygenation in a sitting position. An 89-year-old woman was diagnosed with subacute cerebellar infarction. Her blood oxygen saturation decreased to 88% in a sitting position, resulting in dyspnea. Cardiological thoracic computed tomography revealed an unruptured aortic aneurysm, an enlarged ascending aorta, right atrial compression, and counterclockwise rotation of the heart. An anatomical distortion of the atrial septum induced by these abnormalities directed the atrial venous inflow such that the right-left shunt flow was exacerbated in a sitting position.

Brachial Artery Thrombosis in a Covid-19 Positive Patient with Thoracic Outlet Syndrome

Severe coronavirus disease 2019 (COVID-19) has been complicated by coagulopathy and thrombotic events including venous thromboembolism, pulmonary embolism, and arterial thrombus at a rate higher than has traditionally been seen with sepsis-induced coagulopathy or disseminated intravascular coagulation leading most centers to treat hospitalized patients with prophylactic anticoagulation. We present a case of a patient with thoracic outlet syndrome who presents with brachial artery thrombosis in the setting of infection with COVID-19. Both thoracic outlet syndrome and COVID-19 infection are independently associated with increased risk of thrombotic events. The induced hypercoagulable state from COVID-19 infection may result in acute arterial thrombosis in patients with predisposing anatomic differences consistent with thoracic outlet syndrome. Level of Evidence: V.

Hydrophilic Polymer Embolism: Implications for Manufacturing, Regulation, and Postmarket Surveillance of Coated Intravascular Medical Devices

ABSTRACT

Hydrophilic polymers are ubiquitously applied as surface coatings on catheters and intravascular medical technologies. Recent clinical literature has heightened awareness on the complication of hydrophilic polymer embolism, the phenomenon wherein polymer coating layers separate from catheter and device surfaces, and may be affiliated with a range of unanticipated adverse reactions. Significant system barriers have limited and delayed reporting on this iatrogenic complication, the full effects of which remain underrecognized by healthcare providers and manufacturers of various branded devices. In 2015, the United States Food and Drug Administration acknowledged rising clinical concerns and stated that the agency would work with stakeholders to further evaluate gaps that exist in current national and international device standards for coated intravascular medical technologies. The present article reviews current knowledge on this complication as well as factors that played a role in delaying detection and dissemination of information and new knowledge once hazards and clinical risks were identified. Furthermore, organ-specific effects and adverse reaction patterns are summarized, along with implications for device manufacturing, safety assurance, and regulation. Qualitative and quantitative particulate testing are needed to optimize coated intravascular device technologies. Moreover, general enhanced processes for medical device surveillance are required for timely adverse event management and to ensure patient safety.

Embolism of a Piece of Iron after Penetrating Neck Injury: From Right Internal Jugular Vein to Left Lower Lobe of the Lung

OBJECTIVE

This case report of a 40-year-old male patient describes the embolization of a piece of iron trapped in the jugular vein following an industrial injury.

CASE REPORT

The 40-year-old male patient was admitted to the emergency service for bleeding from the neck. In contrast to the first X-ray image, no foreign body was observed at the injury site or aspiration of fluid during emergency surgery. Following x-ray radiography, an opacity was observed in the left lower lobe of the lung, consistent with a foreign body. Echocardiography demonstrated no pathological manifestation in the atria, ventricles, or major pulmonary artery. There was no need to intervene because the patient was asymptomatic and had no noticeable symptoms of hemoptysis. The outpatient clinic's radiological and clinical control examinations were normal at the end of six months.

CONCLUSION

The movement of the foreign body to the lung within one or two hours may have resulted from our manipulation or may have occurred spontaneously. As a result, any foreign bodies that have invaded the vascular system should be removed as soon as possible.

Multiple thrombotic sources and embolic events at arterial sites in a patient with protein-C deficiency

Protein-C deficiency causes a thrombophilic environment in circulation. Although venous thromboembolism is the most common presentation, arterial events are rare. A 45 year-old woman with protein-C deficiency presented with multiple thromboembolic events including bilateral renal infarct and inferior ST-elevation myocardial infarction 3-days after coronary angiography via femoral approach which were normal coronary arteries. Computed tomographic angiography and transesophageal echocardioraphy displayed multiple thrombi sources including left atrium, left subclavian artery, sinus valsalva and descending aorta. Unfractionated-heparin and tissue plasminogen activator infusion were given. Although regression in ST-segment elevation and chest pain, no reduction in sizes of left atrial and aortic thrombus was observed by imaging modality. The patient refused surgical removal of thrombi, then warfarin therapy was planned. In patients with congenital thrombophilia and history of thromboembolism, anticoagulant treatment should be carefully managed during percutaneous diagnostic and interventional treatments and they should be performed by radial approach without interruption of anticoagulants.

From cells to stems: the effects of primary vascular construction on drought-induced embolism in fern rhizomes

While a considerable amount of data exists on the link between xylem construction and hydraulic function, few studies have focused on resistance to drought-induced embolism of primary vasculature in herbaceous plants. Ferns rely entirely on primary xylem and display a remarkable diversity of vascular construction in their rhizomes, making them an ideal group in which to examine hydraulic structure-function relationships. New optical methods allowed us to measure vulnerability to embolism in rhizomes, which are notoriously difficult to work with. We investigated five fern species based on their diverse xylem traits at the cellular, histological, and architectural levels. To link below- and above-ground hydraulics, we then measured leaf-stem vulnerability segmentation. Overall, rhizome vulnerability to embolism was correlated most strongly with cellular but not histological or architectural traits. Interestingly, at P_6-12 , species with increased architectural dissection were actually more vulnerable to embolism, suggesting different hydraulic dynamics at low compared to high percent embolism. Importantly, leaves fully embolize before stems reach P₈₈ , suggesting strong vulnerability segmentation. This is the first study to explore the functional implications of primary vascular construction in fern rhizomes and leaf-stem vulnerability segmentation. Strong segmentation suggests that leaves protect perennial rhizomes against severe drought stress and hydraulically induced mortality.

Effectiveness and safety of rivaroxaban versus warfarin among nonvalvular atrial fibrillation patients with obesity and diabetes

AIMS

To compare clinical outcomes of rivaroxaban and warfarin in patients with nonvalvular atrial fibrillation (NVAF) and concurrent obesity and diabetes.

METHODS

Patients aged ≥18 years were identified from a healthcare claims database with the following criteria: newly initiating rivaroxaban or warfarin, ≥1 medical claim with a diagnosis of AF, obesity determined by validated machine learning algorithm, and ≥1 claim with a diagnosis of diabetes or for antidiabetic medication. Treatment cohorts were matched using propensity scores and were compared for stroke/systemic embolism (SE) and major bleeding using Cox proportional hazards models.

RESULTS

A total of 9999 matched pairs of NVAF patients with obesity and diabetes who initiated treatment with rivaroxaban or warfarin were included. The composite risk of stroke/SE was significantly lower in the rivaroxaban cohort compared with the warfarin cohort (HR 0.82; 95% CI 0.74-0.90). Risks of ischemic and hemorrhagic strokes were also significantly reduced with rivaroxaban versus warfarin, but not SE. Major bleeding risk was similar between treatment cohorts (HR 0.92; 95% CI 0.78-1.09).

CONCLUSIONS

In NVAF patients with comorbidities of obesity and diabetes, rivaroxaban was associated with lower risks of stroke/SE and similar risk of major bleeding versus warfarin.

Device-detected atrial high rate episodes and the risk of stroke/thrombo-embolism and atrial fibrillation incidence: a systematic review and meta-analysis

BACKGROUND

Atrial High Rate Episodes (AHRE) are asymptomatic atrial tachy-arrhythmias detected through continuous monitoring with a cardiac implantable electronic device. The risks of stroke/Thromboembolic (TE) events and incident clinical Atrial Fibrillation (AF) associated with AHRE varies markedly.

OBJECTIVES

To assess the relationship between AHRE and TE events, and between AHRE and incident clinical AF.

METHODS

This systematic review and meta-analysis was conducted following the PRISMA recommendations. PubMed, Scopus, and Google Scholar were searched from inception to 18/02/2021 for studies reporting TE events and incident clinical AF in patients with AHRE, as compared with patients without.

RESULTS

Ten out of 8081 records fulfilled the inclusion criteria, for a total of 37 266 patients. Seven out of ten studies excluded patients with prior history of clinical AF (4961 patients), embracing the most recent definition of AHRE. The risk ratio (RR) for TE events in AHRE patients was 2.13 (95% CI: 1.53-2.95, I²: 0%). The incidence of clinical AF was reported in four studies excluding patients with a history of clinical AF (3574 patients). The RR for incident clinical AF was 3.34 (95%CI: 1.89-5.90, I²: 73%).

CONCLUSIONS

AHRE are significantly associated with systemic thromboembolism and incident clinical AF. Further studies are needed to improve patients' risk stratification and management.

Plasticity of the xylem vulnerability to embolism in Populus tremula x alba relies on pit quantity properties rather than on pit structure

Knowledge on variations of drought resistance traits are needed to predict the potential of trees to acclimate to coming severe drought events. Xylem vulnerability to embolism is a key parameter related to such droughts, and its phenotypic variability relies mainly on environmental plasticity. We investigated the structural determinants controlling the plasticity of vulnerability to embolism, focusing on the key elements involved in the air bubble entry in vessels, especially the intervessel pits. Poplar saplings (Populus tremula x alba (Aiton) Sm., 1804) grown in contrasted water availability or light exposure exhibited differences in the vulnerability to embolism (P50) in a range of 0.76 MPa. We then characterized the structural changes in features related to pit quantity and pit structure, from the pit ultrastructure to the organization of xylem vessels, using different microscopy techniques (transmission electron microscopy, scanning electron microscopy, light microscopy). A multispectral combination of X-ray microtomography and light microscopy analysis allowed measuring the vulnerability of each single vessel and testing some of the relationships between structural traits and vulnerability to embolism inside the xylem. The pit ultrastructure did not change, whereas the vessel dimensions increased with the vulnerability to embolism and the grouping index and fraction of intervessel cell wall both decreased with the vulnerability to embolism. These findings hold when comparing between trees or between the vessels inside the xylem of an individual tree. These results evidenced that plasticity of vulnerability to embolism in hybrid poplar occurs through changes in the pit quantity properties such as pit area and vessel grouping rather than changes on the pit structure.

[Vegetation Developed in the Artificial Graft of Ascending Aorta:Report of a Case]

The case was a 65-year-old woman. She underwent graft replacement of ascending aorta because she developed Stanford type A acute aortic dissection in November 2016. After six months she had a fever, so she underwent contrast-enhanced computed tomography and echocardiography at the previous hospital. An abnormal shadow was found in the artificial blood vessel, and the blood culture test was positive. The abnormal shadow was suspected to be a vegetation and was referred to our department. Vegetation was highly mobile and emergency surgery was performed considering the risk of embolism. Intraoperative findings showed that vegetation was attached to the anastomotic site of the artificial blood vessel. She was transferred to a rehabilitation hospital 57 days after the operation and is currently rehabilitating.

Seasonal patterns of callose deposition and xylem embolism in five boreal deciduous tree species

PREMISE

Phloem tissue allows for sugar transport along the entirety of a plant and, thus, is one of the most important anatomical structures related to growth. It is thought that the sugar-conducting sieve tube may overwinter and that its cells persist multiple seasons in deciduous trees. One possible overwintering strategy is to build up callose on phloem sieve plates to temporarily cease their function. We tested the hypothesis that five deciduous tree species produce callose on their sieve plates on a seasonal basis.

METHODS

Young shoots of five deciduous tree species were sampled periodically between April 2019 and February 2020 in Edmonton, Alberta, Canada. After enzymatic digestion of cytoplasmic constituents, cross sections were imaged using scanning electron microscopy to observe and quantify the level of callose deposition at monthly intervals, and sieve plate pore size was measured. Using a conductivity apparatus, we measured xylem native embolism during these sampling periods.

RESULTS

Contrary to past work on some of the same species, we found little evidence that sieve tubes overwinter by becoming occluded with callose. Instead, we found that most sieve plates remain open. Xylem embolism was minimal during the peak growing season, but increased over winter.

CONCLUSIONS

Many species had been assumed to deposit callose on sieve plates over winter, though anatomical and phenological phloem data were sparse. Our data do not support this notion.

Limited plasticity in embolism resistance in response to light in leaves and stems in species with considerable vulnerability segmentation

Xylem resistance to embolism is a key metric determining plant survival during drought. Yet, we have a limited understanding of the degree of plasticity in vulnerability to embolism. Here, we tested whether light availability influences embolism resistance in leaves and stems. The optical vulnerability method was used to assess stem and leaf resistance to embolism in Phellodendron amurense and Ilex verticillata acclimated to sun and shade microenvironments within the same canopy. In both species, we found considerable segmentation in xylem resistance to embolism between leaves and stems, but only minor acclimation in response to light availability. With the addition of a third species, Betula pubescens, which shows no vulnerability segmentation, we sought to investigate xylem anatomical traits that might correlate with strong vulnerability segmentation. We found a correlation between the area fraction of vessels in the xylem and embolism resistance across species and tissue types. Our results suggest that minimal acclimation of embolism resistance occurs in response to light environment in the same individual and that the degree of vulnerability segmentation between leaves and stems might be determined by the vessel lumen fraction of the xylem.

By the narrowest of margins: nano-scale modification of pit membranes and the fate of plants during drought. A commentary on: 'Intervessel pit membrane thickness best explains variation in embolism resistance amongst stems of Arabidopsis thaliana accessions'

This article comments on: Ajaree Thonglim, Sylvain Delzon, Maximilian Larter, Omid Karami, Arezoo Rahimi, Remko Offringa, Joost J. B. Keurentjes, Salma Balazadeh, Erik Smets and Frederic Lens, Intervessel pit membrane thickness best explains variation in embolism resistance amongst stems of Arabidopsis thaliana accessions, Annals of Botany, Volume 128, Issue 2, 23 July 2021, Pages 171–182, 10.1093/aob/mcaa196

Intervessel pit membrane thickness best explains variation in embolism resistance amongst stems of Arabidopsis thaliana accessions

BACKGROUND AND AIMS

The ability to avoid drought-induced embolisms in the xylem is one of the essential traits for plants to survive periods of water shortage. Over the past three decades, hydraulic studies have been focusing on trees, which limits our ability to understand how herbs tolerate drought. Here we investigate the embolism resistance in inflorescence stems of four Arabidopsis thaliana accessions that differ in growth form and drought response. We assess functional traits underlying the variation in embolism resistance amongst the accessions studied using detailed anatomical observations.

METHODS

Vulnerability to xylem embolism was evaluated via vulnerability curves using the centrifuge technique and linked with detailed anatomical observations in stems using light microscopy and transmission electron microscopy.

KEY RESULTS

The data show significant differences in stem P50, varying 2-fold from -1.58 MPa in the Cape Verde Island accession to -3.07 MPa in the woody soc1 ful double mutant. Out of all the anatomical traits measured, intervessel pit membrane thickness (TPM) best explains the differences in P50, as well as P12 and P88. The association between embolism resistance and TPM can be functionally explained by the air-seeding hypothesis. There is no evidence that the correlation between increased woodiness and increased embolism resistance is directly related to functional aspects. However, we found that increased woodiness is strongly linked to other lignification characters, explaining why mechanical stem reinforcement is indirectly related to increased embolism resistance.

CONCLUSIONS

The woodier or more lignified accessions are more resistant to embolism than the herbaceous accessions, confirming the link between increased stem lignification and increased embolism resistance, as also observed in other lineages. Intervessel pit membrane thickness and, to a lesser extent, theoretical vessel implosion resistance and vessel wall thickness are the missing functional links between stem lignification and embolism resistance.