Browsing by Subject "Embolism"
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Item Open Access Embolization of patent foramen ovale closure devices: incidence, role of imaging in identification, potential causes, and management.(Tex Heart Inst J, 2013) Goel, Sachin S; Aksoy, Olcay; Tuzcu, E Murat; Krasuski, Richard A; Kapadia, Samir RTranscatheter patent foramen ovale (PFO) closure is an alternative to antiplatelet or anticoagulative therapy in patients with cryptogenic stroke, and it is associated with a small incidence of periprocedural sequelae. Because embolization of PFO closure devices is a very rare procedural complication, data on its frequency, causes, and management are sparse. We sought to review the medical literature and the cases of PFO closure-device embolization at our institution with the aim of identifying likely problems and reporting potential solutions. Out of 310 adult patients who underwent transcatheter PFO closure from June 2002 through April 2011, there were 2 cases (0.6%) of PFO closure-device embolization. In both patients, hypermobile septum primum and thick septum secundum were present. In one patient, failure to use a sizing balloon might have resulted in an underestimation of the PFO's size. In both patients, device embolization was identified in a timely fashion, the embolized device was safely retrieved, and the PFO was percutaneously closed with success. The incidence of PFO closure-device embolization is very low. The cases described here underscore the importance of imaging in the identification of morphologic predispositions to closure-device malpositioning, in the recognition of impending embolization, and in the timely management of embolization.Item Open Access Plant water transport and photosynthesis in water-limited environments(2020) Mrad, AssaadTerrestrial ecosystems depend on vegetation for many indispensable services including carbon fixation from the atmosphere, food production, and the maintenance of the global water and carbon cycles. As the climate changes, temperature and precipitation patterns shift and extreme climatic events become more frequent. In many areas, droughts are increasing in intensity and frequency, posing a challenge to ecosystem health and food security. Plants depend on water for physiological functioning including photosynthesis. The ability of plants to continue supplying water to the leaves from the soil during droughts depends on the anatomy and structure of its vascular network, the xylem. Droughts cause gas bubbles, or embolisms, to spread within the xylem, blocking water movement.
A combination of modeling water flow in xylem of flowering plants and theoretical considerations derived from graph theory is used to explain the response of different xylem functional types to droughts. An open-source model of plant xylem hydraulics was developed with which it was shown how 'network' effects, such as the spatial distribution of anatomy throughout growth rings, alter the response of Maples to drought.
The xylem of similar flowering plants was further investigated through the model in addition to the the physics of percolation. This was the first instance percolation theory has ever been applied to embolism spread inside xylem. It was shown how embolism spread inside the xylem can be represented by an edge percolation process. The results indicate that an increased connectivity among the conduits in the xylem is a necessary feature in plant organs that are resistant to droughts.
The detrimental effects of droughts on plant water translocation cascade to inhibit photosynthesis. Soil-to-leaf resistance to drought is represented by a vulnerability to embolism curve (VC) that plots the percent loss in plant hydraulic conductivity as water potential declines. The whole-plant VC affects plant CO2 fixation under drought. The results show how different VC shapes give rise to typical isohydric and anisohydric plant responses to drought. To arrive at this conclusion, the calculus of variations is used to integrate plant hydraulics into the trade-off between CO2 fixation and transpiration during a drought.
Item Open Access Role of aquaporin activity in regulating deep and shallow root hydraulic conductance during extreme drought(Trees, 2014-05-30) Johnson, Daniel M; Sherrard, Mark E; Domec, Jean-Christophe; Jackson, Robert BKey message Deep root hydraulic conductance is upregulated during severe drought and is associated with upregulation in aquaporin activity. In 2011, Texas experienced the worst single-year drought in its recorded history and, based on tree-ring data, likely its worst in the past millennium. In the Edwards Plateau of Texas, rainfall was 58 % lower and the mean daily maximum temperatures were >5 °C higher than long-term means in June through September, resulting in extensive tree mortality. To better understand the balance of deep and shallow root functioning for water supply, we measured root hydraulic conductance (KR) in deep (~20 m) and shallow (5-10 cm) roots of Quercus fusiformis at four time points in the field in 2011. Deep roots of Q. fusiformis obtained water from a perennial underground (18-20 m) stream that was present even during the drought. As the drought progressed, deep root KR increased 2.6-fold from early season values and shallow root KR decreased by 50 % between April and September. Inhibitor studies revealed that aquaporin contribution to KR increased in deep roots and decreased in shallow roots as the drought progressed. Deep root aquaporin activity was upregulated during peak drought, likely driven by increased summer evaporative demand and the need to compensate for declining shallow root KR. A whole-tree hydraulic transport model predicted that trees with greater proportions of deep roots would have as much as five times greater transpiration during drought periods and could sustain transpiration during droughts without experiencing total hydraulic failure. Our results suggest that trees shift their dependence on deep roots versus shallow roots during drought periods, and that upregulation of aquaporin activity accounts for at least part of this increase. © 2014 Springer-Verlag Berlin Heidelberg.Item Open Access Screening of Multiple Biomarkers Associated With Ischemic Stroke in Atrial Fibrillation.(Journal of the American Heart Association, 2020-12-09) Hijazi, Ziad; Wallentin, Lars; Lindbäck, Johan; Alexander, John H; Connolly, Stuart J; Eikelboom, John W; Ezekowitz, Michael D; Granger, Christopher B; Lopes, Renato D; Pol, Tymon; Yusuf, Salim; Oldgren, Jonas; Siegbahn, AgnetaBackground To explore the pathophysiological features of ischemic stroke in patients with atrial fibrillation (AF), we evaluated the association between 268 plasma proteins and subsequent ischemic stroke in 2 large AF cohorts receiving oral anticoagulation. Methods and Results A case-cohort sample of patients with AF from the ARISTOTLE (Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation) trial, including 282 cases with ischemic stroke or systemic embolism and a random sample of 4124 without these events, during 1.9 years of follow-up was used for identification. Validation was provided by a similar case-cohort sample of patients with AF from the RE-LY (Randomized Evaluation of Long-Term Anticoagulation Therapy) trial, including 149 cases with ischemic stroke/systemic embolism and a random sample of 1062 without these events. In plasma obtained before randomization, 268 unique biomarkers were measured with OLINK proximity extension assay panels (CVD II, CVD III, and Inflammation) and conventional immunoassays. The association between biomarkers and outcomes was evaluated by random survival forest and adjusted Cox regression. According to random survival forest or Cox regression analyses, the biomarkers most strongly and consistently associated with ischemic stroke/systemic embolism were matrix metalloproteinase-9, NT-proBNP (N-terminal pro-B-type natriuretic peptide), osteopontin, sortilin, soluble suppression of tumorigenesis 2, and trefoil factor-3. The corresponding hazard ratios (95% CIs) for an interquartile difference were as follows: 1.18 (1.00-1.38), 1.55 (1.28-1.88), 1.28 (1.07-1.53), 1.19 (1.02-1.39), 1.23 (1.05-1.45), and 1.19 (0.97-1.45), respectively. Conclusions In patients with AF, of 268 unique biomarkers, the 6 biomarkers most strongly associated with subsequent ischemic stroke/systemic embolism represent fibrosis/remodeling (matrix metalloproteinase-9 and soluble suppression of tumorigenesis 2), cardiac dysfunction (NT-proBNP), vascular calcification (osteopontin), metabolism (sortilin), and mucosal integrity/ischemia (trefoil factor-3). Registration URL: https://www.clinicaltrials.gov. Unique Identifiers: NCT00412984 and NCT00262600.