Status Update and Interim Results from the Asymptomatic Carotid Surgery Trial-2 (ACST-2)

Objectives: ACST-2 is currently the largest trial ever conducted to compare carotid artery stenting (CAS) with carotid endarterectomy (CEA) in patients with severe asymptomatic carotid stenosis requiring revascularization. Methods: Patients are entered into ACST-2 when revascularization is felt to be clearly indicated, when CEA and CAS are both possible, but where there is substantial uncertainty as to which is most appropriate. Trial surgeons and interventionalists are expected to use their usual techniques and CE-approved devices. We report baseline characteristics and blinded combined interim results for 30-day mortality and major morbidity for 986 patients in the ongoing trial up to September 2012. Results: A total of 986 patients (687 men, 299 women), mean age 68.7 years (SD ± 8.1) were randomized equally to CEA or CAS. Most (96%) had ipsilateral stenosis of 70-99% (median 80%) with contralateral stenoses of 50-99% in 30% and contralateral occlusion in 8%. Patients were on appropriate medical treatment. For 691 patients undergoing intervention with at least 1-month follow-up and Rankin scoring at 6 months for any stroke, the overall serious cardiovascular event rate of periprocedural (within 30 days) disabling stroke, fatal myocardial infarction, and death at 30 days was 1.0%. Conclusions: Early ACST-2 results suggest contemporary carotid intervention for asymptomatic stenosis has a low risk of serious morbidity and mortality, on par with other recent trials. The trial continues to recruit, to monitor periprocedural events and all types of stroke, aiming to randomize up to 5,000 patients to determine any differential outcomes between interventions. Clinical trial: ISRCTN21144362. © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved

Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable. Funding: UK Medical Research Council and Health Technology Assessment Programme

Wind regime and development of star dune on Erg Chebbi (South Marocco)

Wydmy gwiaździste (wydmy piramidalne, demkhas, ghourds, rhourds, oghrouds) są najmniej rozpoznanymi formami akumulacji eolicznej. Ich występowanie wiąże się z obszarami charakteryzującymi się złożonym reżimem wiatru - o co najmniej trzech kierunkach wiatru wydmotwórczego. Wykorzystując przestrzenne modele 16 form wydmowych, wykonane na podstawie szczegółowych pomiarów terenowych, przeanalizowano kształt wydm ergu Chebbi. Położenie i przebieg ramion porównano z reżimem wiatru. Określono dominujące kierunki wiatru wydmotwórczego dla wydm gwiaździstych oraz wydm poprzecznych w różnych fazach rozwoju, od form inicjalnych do dojrzałych. Stwierdzono, że rozwój wydm gwiaździstych ergu Chebbi związany jest tylko z dwoma kierunkami wiatru wydmotwórczego: SW i NE. Uzyskane wyniki pozwalają wnioskować, że obszary, na których dominują dwa kierunki wiatru, stanowią potencjalne regiony tworzenia się wydm gwiaździstych.Star dunes (pyramid dunes, demkhas, ghourds, rhourds, oghrouds) are the least studied dune type. Their development is typically associated with multidirectional wind regime. The aim of the study was to analyze the star dunes shape and correlate it with wind regime. This was made on the basis of detailed field measurements conducted within the Erg Chebbi (S Morocco), which allow to create 3D models of 16 dune forms. The position and orientation of dune arms were compared with wind regime. This allow to determine the main wind directions, which influence the development of star and transverse dunes in this area. The analysis is made for dune in different stages, from initial to mature forms. The results show that development of star dune on Erg Chebbi is connected with two wind directions, SW and NE wind. This allows to conclude that the areas with two dominant wind directions (bimodal wind regime) are the potential regions of star dune development

Star dune shape variability in the area of bimodal wind regime

Contemporary morphological changes of star dunes are observed mainly in certain parts of these dunes. They occur as lateral migration of crestlines of dune arms and modifications of inclination of their slopes. The aim of the research was to determine annual variability of shapes of compound and complex star dunes in bimodal wind regime. Precise measurements of 5 star dunes were performed with use of GPS RTK in March, 2011, and March, 2012, on Erg Chebbi (Morocco). Based on these measurements, 3D models of the dunes were created, which in turn, allowed for calculation of annual magnitude and direction of crestlines migration of star dune main arms. The results show that the resultant drift direction was in accordance with long-term regime of active wind in the study area. Both, the resultant drift direction and its magnitude were similar in all studied dunes. Variability of star dune shapes occurred to be independent from their stage of development (size of a dune) or its type. The most important feature determining morphodynamics of the star dune arms are: i) the angle between the arms and the active wind, and ii) slope inclination of the arms

Shape of barchan dunes as an indicator of wind regime: a case study from the Moroccan Western Sahara

Barchans are characterized by a symmetric shape independently of their stage of development and the axis of symmetry parallels to the dominant wind direction. However, shape of the dunes can be modified by several factors, among which most important are: change of wind regime, dune collisions or interaction of closely spaced dunes, ground surface relief, asymmetric sediment supply. The aim of the study was to analyze the impact of short-term (diurnal) and long-term (seasonal) changes in wind direction and velocity on shape of barchan dunes. The study was conducted in southern Moroccan area of Western Sahara, between Tarfaya and Laâyoune. This area is characterised by significant variability of active wind (RDP/DP=0,66) which is unfavourable for barchans development. Measurements were conducted in two spring seasons of 2011 and 2012 and two autumn seasons of 2007 and 2011. 52 isolated barchans were selected for detailed studies. Based on GPS-RTK measurements, precise 3D models of the landforms were obtained allowing the detailed analysis of dune shapes. Changes of basie morphological parameters were analyzed as well as shape changes occurring the windward slope and within dunes horns. The shapes of the barchans were correlated with the short-term and the long-term wind regime. It was found that basic morphological parameters are not good indicators of wind variability, with the exception of barchan horns lengths which change according to the seasonal wind regime. Short-term wind regime changes are well registered by: i) "collars" developing along the dune crestlines, ii) "tongues" developing at the ends of dune horns and iii) location of the dune apex. On the other hand, beaded horns testify for very strong wind. I was found, that mentioned features develop and undergo modification during first days or even hours of changed wind regime. The analyzes of barchan shapes, performed in different seasons, proved that even a several-month long period of highly diversified wind regime does not change basie shape of the barchans. Therefore, it can be inferred that barchans development does not depend exclusively on wind regime

Degradation of terraced slopes in Mediterranean conditions: selected examples from the Aegean Islands (Greece)

The main aim of the study was to estimate the influence of relief, lithology, climatic conditions, methods of wall construction and actual agricultural practice on the degradation of traditional agricultural terraces on the example of three Greek islands. We selected 7 research plots situated in 5 different geological settings - 3 on the Ikaria island, 2 on Thira, and 2 near Plati village on the SW edge of Lassithi Plateau on the Crete island. We used the following methods: GPS RTK measurements, mapping of erosion features, georadar profliling, infiltration rate measurements and interviews with farmers. We find that lithology is the most important factor controlling terraces degradation, but only in relation to methods of cultivation. Traditional agricultural practice helps terraces to remain stable, because cultivated field increases the possibility of infiltration and limits surface runoff. Heavy rainfalls do not affecting terraces stability due to high ground infiltration rate or high permeability of dry-stone walls. Terraces are more stable if they are concordant to the natural slope profile. On the terraced slope erosion is lower than on non-terraced slope. This is true only on the slope with very limited vegetation cover

Th e sources of moisture in the barchans of Western Sahara

The aim of the study was to determine the impact of climatic and meteorological conditions on aeolian sand transport within barchans. The study area was located at Western Sahara, around the towns of Tarfaya and Laâyoune. Particular attention was paid to the factors that increase the moisture content of the surface and subsurface layers of sand dunes. It could be one of the important factors to have an influence on threshold wind velocity. Western Sahara dune fields are situated in the zone of the dominant wind direction from the northern sector, which determines the barchan dunes shape and orientation, as well as the supply of moisture from the Atlantic Ocean. The results of investigations confirm that dunes receive quite a lot of moisture from rainfall and such phenomena as fog as well. Studies have confirmed that the water supply from the fog is comparable to, or even exceeds the amount of water from rainfall in the area. Wetted surface layer reduces the transport of aeolian material, even in case of a wind speed greater than 4-5 ms⁻¹. The presence of fog and dew does not affect the moisture of the deeper sand layers, which occurs after rainfall. Analysis of aeolian sand transport within the barchan dunes in the areas such a Western Sahara, should not be therefore limited to the measurement of wind speed and its direction. It must include the investigations on other meteorological elements, especially air temperature and humidity conditions, responsible for the amount of atmospheric deposits on the dune surface

Impact of river channels morphodynamic on human activity in the High Atlas Mountains. Case Study of Upper Dades Valley, Morocco

The paper describes the results of research in the Upper Dades Valley in the High Atlas Mountains in Morocco. The purpose of the research was to identify the impact of river channels changes, fluvial accumulation nad erosion on human activity. Fieldwork and maps were used to characterize the structure of the Dades river channel and the intensity of present-day fluvial processes. Research data show that the Upper Dades Valley is shaped primarily by short but frequent and intense hydrometeorological events. The structure of the Dades river channel indicates a complex functionality. Tributary episodic riviers and gorges sections supply most of the weathering material. Narrow sections of Dades channel serve for material as transfer zones, while deposition occurs across broader areas. Research has shown that extreme fluvial processes occurring in semi-arid mountains result in fast river chanels changes and accelerated deposition of weathering material across valley floors, which usually leads to limits on the development of agriculture in such areas

Second asymptomatic carotid surgery trial (ACST-2): a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86–1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91–1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable. Funding: UK Medical Research Council and Health Technology Assessment Programme