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Christopher M Wallace - One of the best experts on this subject based on the ideXlab platform.
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the natural history and predictive features of hemorrhage from brain arteriovenous malformations
2009Co-Authors: Leodante Da Costa, Christopher M Wallace, Karel G Ter Brugge, Cian Okelly, Robert A Willinsky, Michael TymianskiAbstract:Background and Purpose—Patients harboring brain arteriovenous malformations (bAVMs) are at a lifelong risk for hemorrhagic strokes, but the natural history is poorly understood. We examined the impact of demographic and angiographic features on the likelihood of future hemorrhage. Methods—A prospectively accrued database of bAVM patients maintained at the Toronto Western Hospital was analyzed; 678 consecutive, prospectively enrolled bAVM patients were followed for 1931.7 patient-years. The rate of hemorrhage over long-term follow-up was recorded. The impact of baseline clinical and radiographic features and Partial Treatment on time to hemorrhage were analyzed using survival analysis. Neurological outcome after hemorrhage was assessed using the Glasgow Outcome Score. Results—Hemorrhage rates were 4.61% per year for the entire cohort (n678), 7.48% per year for bAVMs with initial hemorrhagic presentation (n258), 4.16% per year for initial seizure presentation (n260), 3.99% per year for patients not harboring aneurysms (n556), 6.93% per year for patients with associated aneurysms (n122), and 5.42% per year for bAVMs with deep venous drainage (n365). Hemorrhagic presentation was a significant independent predictor of future hemorrhage (HR, 2.15; P0.01), whereas associated aneurysms (HR, 1.59; P0.07) and deep venous drainage (HR, 1.59; P0.07) showed a trend toward significance. Hemorrhage risk was unchanged in patients who underwent Partial arteriovenous malformation embolization (n211; HR, 0.875; P0.32). Conclusion—Brain arteriovenous malformations presenting with hemorrhage, with deep venous drainage, or associated aneurysms have 2-fold greater likelihood of a future hemorrhage. Partial Treatment by embolization does not alter these risks. This natural history should be taken into account in the Treatment strategy. (Stroke. 2009;40:100-105.)
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clinical course of cranial dural arteriovenous fistulas with long term persistent cortical venous reflux
2002Co-Authors: Marc J C Van Dijk, Robert A Willinsky, Karel G Terbrugge, Christopher M WallaceAbstract:Background and Purpose— The natural history of aggressive (Borden 2 and 3) cranial dural arteriovenous fistulas (DAVFs) is not well described. Reported annual mortality and hemorrhage rates vary widely and range up to 20% per year. A consecutive single-center cohort of 236 cases that presented with a cranial DAVF between June 1984 and May 2001 was reviewed for the consequences of long-term persistent cortical venous reflux (CVR). Methods— A group of 118 cranial DAVFs was selected for the presence of CVR. All patients were offered Treatment aimed at the disconnection of the CVR. Patients who declined or had Partial Treatment with persistence of the CVR had long-term clinical and angiographic follow-up to study the disease course of this select group. Results— Treatment was instituted in 101 of the 118 patients (85.6%). Three patients were lost to follow-up. The remaining 14 nontreated patients (11.9%) and the Partially treated patients (n=6) were assessed clinically and angiographically over time. The mean...
Owen Sparrow - One of the best experts on this subject based on the ideXlab platform.
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the natural history of cranial dural arteriovenous fistulae with cortical venous reflux the significance of venous ectasia
2012Co-Authors: Diederik Bulters, Nijaguna Mathad, David Culliford, John Millar, Owen SparrowAbstract:BACKGROUND The quoted risk of hemorrhage from dural arteriovenous fistulae with cortical venous reflux varies widely, and the influence of angiographic grade on clinical course has not previously been reported. OBJECTIVE To assess the risk of hemorrhage and the influence of angiographic grade on this risk, compared with known predictors of hemorrhage such as presentation. METHODS Seventy-five fistulae with cortical venous reflux identified in our arteriovenous malformations clinic between 1992 and 2007 were followed up clinically, and their angiograms were reviewed. RESULTS There were 8 hemorrhages in 90 years of follow-up. The annual incidence of hemorrhage before any Treatment was 13%, and 4.7% after Partial Treatment, giving an overall incidence of 8.9% before definitive Treatment. Borden and Cognard grades were poor discriminators of risk for lesions with the exception of Cognard type IV lesions. These lesions, characterized by venous ectasia, had a 7-fold increase in the incidence of hemorrhage (3.5% no ectasia vs 27% with ectasia). Patients presenting with hemorrhage (20%) or nonhemorrhagic neurological deficit (22%) had a higher incidence of hemorrhage than those with a benign presentation (4.3%), but this may be directly linked to the presence of venous ectasia. CONCLUSION In this series untreated dural arteriovenous fistulae with cortical venous reflux had a 13% annual incidence of hemorrhage after diagnosis. There was a significant difference between those with and without venous ectasia. This should be confirmed by further studies, but probably defines a high-risk subgroup of patients that requires rapid intervention.
Robert A Willinsky - One of the best experts on this subject based on the ideXlab platform.
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the natural history and predictive features of hemorrhage from brain arteriovenous malformations
2009Co-Authors: Leodante Da Costa, Christopher M Wallace, Karel G Ter Brugge, Cian Okelly, Robert A Willinsky, Michael TymianskiAbstract:Background and Purpose—Patients harboring brain arteriovenous malformations (bAVMs) are at a lifelong risk for hemorrhagic strokes, but the natural history is poorly understood. We examined the impact of demographic and angiographic features on the likelihood of future hemorrhage. Methods—A prospectively accrued database of bAVM patients maintained at the Toronto Western Hospital was analyzed; 678 consecutive, prospectively enrolled bAVM patients were followed for 1931.7 patient-years. The rate of hemorrhage over long-term follow-up was recorded. The impact of baseline clinical and radiographic features and Partial Treatment on time to hemorrhage were analyzed using survival analysis. Neurological outcome after hemorrhage was assessed using the Glasgow Outcome Score. Results—Hemorrhage rates were 4.61% per year for the entire cohort (n678), 7.48% per year for bAVMs with initial hemorrhagic presentation (n258), 4.16% per year for initial seizure presentation (n260), 3.99% per year for patients not harboring aneurysms (n556), 6.93% per year for patients with associated aneurysms (n122), and 5.42% per year for bAVMs with deep venous drainage (n365). Hemorrhagic presentation was a significant independent predictor of future hemorrhage (HR, 2.15; P0.01), whereas associated aneurysms (HR, 1.59; P0.07) and deep venous drainage (HR, 1.59; P0.07) showed a trend toward significance. Hemorrhage risk was unchanged in patients who underwent Partial arteriovenous malformation embolization (n211; HR, 0.875; P0.32). Conclusion—Brain arteriovenous malformations presenting with hemorrhage, with deep venous drainage, or associated aneurysms have 2-fold greater likelihood of a future hemorrhage. Partial Treatment by embolization does not alter these risks. This natural history should be taken into account in the Treatment strategy. (Stroke. 2009;40:100-105.)
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clinical course of cranial dural arteriovenous fistulas with long term persistent cortical venous reflux
2002Co-Authors: Marc J C Van Dijk, Robert A Willinsky, Karel G Terbrugge, Christopher M WallaceAbstract:Background and Purpose— The natural history of aggressive (Borden 2 and 3) cranial dural arteriovenous fistulas (DAVFs) is not well described. Reported annual mortality and hemorrhage rates vary widely and range up to 20% per year. A consecutive single-center cohort of 236 cases that presented with a cranial DAVF between June 1984 and May 2001 was reviewed for the consequences of long-term persistent cortical venous reflux (CVR). Methods— A group of 118 cranial DAVFs was selected for the presence of CVR. All patients were offered Treatment aimed at the disconnection of the CVR. Patients who declined or had Partial Treatment with persistence of the CVR had long-term clinical and angiographic follow-up to study the disease course of this select group. Results— Treatment was instituted in 101 of the 118 patients (85.6%). Three patients were lost to follow-up. The remaining 14 nontreated patients (11.9%) and the Partially treated patients (n=6) were assessed clinically and angiographically over time. The mean...
Yuqing Sun - One of the best experts on this subject based on the ideXlab platform.
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a critical review of risks characteristics and Treatment strategies for potentially toxic elements in wastewater from shale gas extraction
2019Co-Authors: Yuqing Sun, Di Wang, Daniel C W Tsang, Linling Wang, Yujie FengAbstract:Abstract Shale gas extraction via horizontal drilling and hydraulic fracturing (HF) has enhanced gas production worldwide, which has altered global energy markets and reduced the prices of natural gas and oil. Water management has become the most challenging issue of HF, as it demands vast amounts of freshwater and generates high volumes of complex liquid wastes contaminated by diverse potentially toxic elements at variable rates. This critical review focuses on characterizing HF wastewater and establishing strategies to mitigate environmental impacts. High prioritization was given to the constituents with mean concentrations over 10 times greater than the maximum contamination level (MCL) guidelines for drinking water. A number of potentially harmful organic compounds in HF wastewaters were identified via the risk quotient approach to predict the associated toxicity for freshwater organisms in recipient surface waters. Currently, two options for HF wastewater Treatment are preferred, i.e., disposal by deep well injection or on-site re-use as a fracturing fluid. Supplementary Treatment will be enforced by increasingly rigorous regulations. Partial Treatment and reuse remain the preferred method for managing HF wastewater where feasible. Otherwise, advanced technologies such as membrane separation/distillation, forward osmosis, mechanical vapor compression, electrocoagulation, advanced oxidation, and adsorption-biological Treatment will be required to satisfy the sustainable requirements for reuse or surface discharge.
Diederik Bulters - One of the best experts on this subject based on the ideXlab platform.
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the natural history of cranial dural arteriovenous fistulae with cortical venous reflux the significance of venous ectasia
2012Co-Authors: Diederik Bulters, Nijaguna Mathad, David Culliford, John Millar, Owen SparrowAbstract:BACKGROUND The quoted risk of hemorrhage from dural arteriovenous fistulae with cortical venous reflux varies widely, and the influence of angiographic grade on clinical course has not previously been reported. OBJECTIVE To assess the risk of hemorrhage and the influence of angiographic grade on this risk, compared with known predictors of hemorrhage such as presentation. METHODS Seventy-five fistulae with cortical venous reflux identified in our arteriovenous malformations clinic between 1992 and 2007 were followed up clinically, and their angiograms were reviewed. RESULTS There were 8 hemorrhages in 90 years of follow-up. The annual incidence of hemorrhage before any Treatment was 13%, and 4.7% after Partial Treatment, giving an overall incidence of 8.9% before definitive Treatment. Borden and Cognard grades were poor discriminators of risk for lesions with the exception of Cognard type IV lesions. These lesions, characterized by venous ectasia, had a 7-fold increase in the incidence of hemorrhage (3.5% no ectasia vs 27% with ectasia). Patients presenting with hemorrhage (20%) or nonhemorrhagic neurological deficit (22%) had a higher incidence of hemorrhage than those with a benign presentation (4.3%), but this may be directly linked to the presence of venous ectasia. CONCLUSION In this series untreated dural arteriovenous fistulae with cortical venous reflux had a 13% annual incidence of hemorrhage after diagnosis. There was a significant difference between those with and without venous ectasia. This should be confirmed by further studies, but probably defines a high-risk subgroup of patients that requires rapid intervention.