Synchronous retreat of Thwaites and Pine Island glaciers in response to external forcings in the presatellite era.

Today, relatively warm Circumpolar Deep Water is melting Thwaites Glacier at the base of its ice shelf and at the grounding zone, contributing to significant ice retreat. Accelerating ice loss has been observed since the 1970s; however, it is unclear when this phase of significant melting initiated. We analyzed the marine sedimentary record to reconstruct Thwaites Glacier's history from the early Holocene to present. Marine geophysical surveys were carried out along the floating ice-shelf margin to identify core locations from various geomorphic settings. We use sedimentological data and physical properties to define sedimentary facies at seven core sites. Glaciomarine sediment deposits reveal that the grounded ice in the Amundsen Sea Embayment had already retreated to within ~45 km of the modern grounding zone prior to ca. 9,400 y ago. Sediments deposited within the past 100+ y record abrupt changes in environmental conditions. On seafloor highs, these shifts document ice-shelf thinning initiating at least as early as the 1940s. Sediments recovered from deep basins reflect a transition from ice proximal to slightly more distal conditions, suggesting ongoing grounding-zone retreat since the 1950s. The timing of ice-shelf unpinning from the seafloor for Thwaites Glacier coincides with similar records from neighboring Pine Island Glacier. Our work provides robust new evidence that glacier retreat in the Amundsen Sea was initiated in the mid-twentieth century, likely associated with climate variability.

Examining the forgotten valve: outcomes of tricuspid valve surgery, a 15-year experience.

BACKGROUND: We have entered an era of renewed interest in novel approaches to surgical intervention and minimally invasive and transcatheter technique. With an aging population, isolated tricuspid valve regurgitation incidence is rising; however, referral for surgical intervention remains low. AIMS: We undertook this retrospective review to assess outcomes and challenges associated with tricuspid valve intervention. METHODS: A comprehensive retrospective review of all patients undergoing tricuspid valve intervention in our institution between 2004 and 2018 was carried out. RESULTS: A total of 259 patients who underwent a tricuspid intervention between 2004 and 2018 were identified. Of those, 229 underwent a repair and 30 underwent a replacement. Median survival for repair was 3124 days, and replacement was 2294 days. In-patient mortality was 12% for those undergoing repair and 7% for the replacement patients. Of those undergoing redo tricuspid valve intervention, eight patients (61.5%) were alive at most recent follow-up. Eight patients required intraoperative pacemakers, 2 required postoperative pacemakers. Of those who had intraoperative epicardial pacing systems placed, 5 of the 8 remained pacing dependent on most recent follow up. CONCLUSION: Beyond technical challenges, decision making regarding pacemaker requirement requires further exploration. Redo tricuspid valve surgery carries a significant mortality risk and consideration should be given to earlier intervention in this context.

Age-Stratified Outcome in Treatment of Left Main Coronary Artery Stenosis: A NOBLE Trial Substudy.

BACKGROUND: In the treatment of left main coronary artery (LMCA) disease, patients' age may affect the clinical outcome after percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG). This study stratified the clinical outcome according to the age of patients treated for LMCA stenosis with PCI or CABG in the Nordic-Baltic-British Left Main Revascularization (NOBLE) study. METHODS: Patients with LMCA disease were enrolled in 36 centers in northern Europe and randomized 1:1 to treatment by PCI or CABG. Eligible patients had stable angina pectoris, unstable angina pectoris, or non-ST elevation myocardial infarction. The primary endpoint was major adverse cardiac or cerebrovascular events (MACCEs), a composite of all-cause mortality, nonprocedural myocardial infarction, any repeat coronary revascularization, and stroke. Age-stratified analysis was performed for the groups younger and older than 67 years and for patients older than 80 years. RESULTS: For patients ≥67 years, the 5-year MACCEs were 35.7 versus 22.3% (hazard ratio [HR] 1.72 [95% confidence interval [CI] 1.27-2.33], p = 0.0004) for PCI versus CABG. The difference in MACCEs was driven by more myocardial infarctions (10.8 vs. 3.8% HR 3.01 [95% CI 1.52-5.96], p = 0.0009) and more repeat revascularizations (19.5 vs. 10.0% HR 2.01 [95% CI 1.29-3.12], p = 0.002). In patients younger than 67 years, MACCE was 20.5 versus 15.3% (HR 1.38 [95% CI 0.93-2.06], p = 0.11 for PCI versus CABG. All-cause mortality was similar after PCI and CABG in both age-groups. On multivariate analysis, age was a predictor of MACCE, along with PCI, diabetes, and SYNTAX score. CONCLUSIONS: As the overall NOBLE results show revascularization of LMCA disease, age of 67 years or older was associated with lower 5-year MACCE after CABG compared to PCI. Clinical outcomes were not significantly different in the subgroup younger than 67 years, although no significant interaction was present between age and treatment. Mortality was similar for all subgroups (ClinicalTrials.gov identifier: NCT01496651).

Percutaneous coronary angioplasty versus coronary artery bypass grafting in the treatment of unprotected left main stenosis: updated 5-year outcomes from the randomised, non-inferiority NOBLE trial.

BACKGROUND: Percutaneous coronary intervention (PCI) is increasingly used in revascularisation of patients with left main coronary artery disease in place of the standard treatment, coronary artery bypass grafting (CABG). The NOBLE trial aimed to evaluate whether PCI was non-inferior to CABG in the treatment of left main coronary artery disease and reported outcomes after a median follow-up of 3·1 years. We now report updated 5-year outcomes of the trial. METHODS: The prospective, randomised, open-label, non-inferiority NOBLE trial was done at 36 hospitals in nine northern European countries. Patients with left main coronary artery disease requiring revascularisation were enrolled and randomly assigned (1:1) to receive PCI or CABG. The primary endpoint was major adverse cardiac or cerebrovascular events (MACCE), a composite of all-cause mortality, non-procedural myocardial infarction, repeat revascularisation, and stroke. Non-inferiority of PCI to CABG was defined as the upper limit of the 95% CI of the hazard ratio (HR) not exceeding 1·35 after 275 MACCE had occurred. Secondary endpoints included all-cause mortality, non-procedural myocardial infarction, and repeat revascularisation. Outcomes were analysed in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, NCT01496651. FINDINGS: Between Dec 9, 2008, and Jan 21, 2015, 1201 patients were enrolled and allocated to PCI (n=598) or CABG (n=603), with 17 subsequently lost to early follow-up. 592 patients in each group were included in this analysis. At a median of 4·9 years of follow-up, the predefined number of events was reached for adequate power to assess the primary endpoint. Kaplan-Meier 5-year estimates of MACCE were 28% (165 events) for PCI and 19% (110 events) for CABG (HR 1·58 [95% CI 1·24-2·01]); the HR exceeded the limit for non-inferiority of PCI compared to CABG. CABG was found to be superior to PCI for the primary composite endpoint (p=0·0002). All-cause mortality was estimated in 9% after PCI versus 9% after CABG (HR 1·08 [95% CI 0·74-1·59]; p=0·68); non-procedural myocardial infarction was estimated in 8% after PCI versus 3% after CABG (HR 2·99 [95% CI 1·66-5·39]; p=0·0002); and repeat revascularisation was estimated in 17% after PCI versus 10% after CABG (HR 1·73 [95% CI 1·25-2·40]; p=0·0009). INTERPRETATION: In revascularisation of left main coronary artery disease, PCI was associated with an inferior clinical outcome at 5 years compared with CABG. Mortality was similar after the two procedures but patients treated with PCI had higher rates of non-procedural myocardial infarction and repeat revascularisation. FUNDING: Biosensors.

The marine geological imprint of Antarctic ice shelves.

Reductions in the thickness and extent of Antarctic ice shelves are triggering increased discharge of marine-terminating glaciers. While the impacts of recent changes are well documented, their role in modulating past ice-sheet dynamics remains poorly constrained. This reflects two persistent issues; first, the effective discrimination of sediments and landforms solely attributable to sub-ice-shelf deposition, and second, challenges in dating these records. Recent progress in deciphering the geological imprint of Antarctic ice shelves is summarised, including advances in dating methods and proxies to reconstruct drivers of change. Finally, we identify several challenges to overcome to fully exploit the paleo record.

Fauna of the Kemp Caldera and its upper bathyal hydrothermal vents (South Sandwich Arc, Antarctica).

Faunal assemblages at hydrothermal vents associated with island-arc volcanism are less well known than those at vents on mid-ocean ridges and back-arc spreading centres. This study characterizes chemosynthetic biotopes at active hydrothermal vents discovered at the Kemp Caldera in the South Sandwich Arc. The caldera hosts sulfur and anhydrite vent chimneys in 1375-1487 m depth, which emit sulfide-rich fluids with temperatures up to 212°C, and the microbial community of water samples in the buoyant plume rising from the vents was dominated by sulfur-oxidizing Gammaproteobacteria. A total of 12 macro- and megafaunal taxa depending on hydrothermal activity were collected in these biotopes, of which seven species were known from the East Scotia Ridge (ESR) vents and three species from vents outside the Southern Ocean. Faunal assemblages were dominated by large vesicomyid clams, actinostolid anemones, Sericosura sea spiders and lepetodrilid and cocculinid limpets, but several taxa abundant at nearby ESR hydrothermal vents were rare such as the stalked barnacle Neolepas scotiaensis. Multivariate analysis of fauna at Kemp Caldera and vents in neighbouring areas indicated that the Kemp Caldera is most similar to vent fields in the previously established Southern Ocean vent biogeographic province, showing that the species composition at island-arc hydrothermal vents can be distinct from nearby seafloor-spreading systems. δ 13C and δ 15N isotope values of megafaunal species analysed from the Kemp Caldera were similar to those of the same or related species at other vent fields, but none of the fauna sampled at Kemp Caldera had δ 13C values, indicating nutritional dependence on Epsilonproteobacteria, unlike fauna at other island-arc hydrothermal vents.

Role of preoperative blood markers as prognostic factors for lung cancer surgery.

OBJECTIVE: This study was undertaken to assess the potential value of preoperative blood components as prognostic markers of outcome after lung cancer resection, and hence their potential to aid in the selection of patients for curative surgery. METHODS: This was a single-center study on 313 patients who underwent surgery for non-small-cell lung cancer from 2006 to 2008. Data were analyzed retrospectively from a prospectively maintained thoracic database. Preoperative blood results including plasma fibrinogen levels, serum C-reactive protein, hemoglobin concentration, and platelet count were included in the analysis. RESULTS: The mean age was 75 years, and 40% of the patients were females. The most common resection was lobectomy in 68% of patients, followed by pneumonectomy, wedge resection, and segmentectomy in 18%, 10%, and 1.6%, respectively. Patients with abnormal C-reactive protein, fibrinogen, and hemoglobin levels had a worse overall survival. Large tumor size and nodal metastasis on clinical staging was also associated with poor survival. However, on Cox regression analysis, plasma fibrinogen and nodal metastasis were the only independent predictors of survival after lung resection. CONCLUSIONS: Among the different blood markers, elevated preoperative plasma fibrinogen was an independent marker of reduced survival in patients with resected non-small-cell lung cancer, and its value in selecting patients who may benefit from surgery needs further investigation.

Hard rock landforms generate 130 km ice shelf channels through water focusing in basal corrugations.

Satellite imagery reveals flowstripes on Foundation Ice Stream parallel to ice flow, and meandering features on the ice-shelf that cross-cut ice flow and are thought to be formed by water exiting a well-organised subglacial system. Here, ice-penetrating radar data show flow-parallel hard-bed landforms beneath the grounded ice, and channels incised upwards into the ice shelf beneath meandering surface channels. As the ice transitions to flotation, the ice shelf incorporates a corrugation resulting from the landforms. Radar reveals the presence of subglacial water alongside the landforms, indicating a well-organised drainage system in which water exits the ice sheet as a point source, mixes with cavity water and incises upwards into a corrugation peak, accentuating the corrugation downstream. Hard-bedded landforms influence both subglacial hydrology and ice-shelf structure and, as they are known to be widespread on formerly glaciated terrain, their influence on the ice-sheet-shelf transition could be more widespread than thought previously.

A new acute scaphoid fracture assessment method: a reliability study of the 'long axis' measurement.

BACKGROUND: The aim of this study was to assess the inter observer and intra observer reliability of acute scaphoid fracture classification methods including a novel 'long axis' measurement, a simple method which we have developed with the aim of improving agreement when describing acute fractures. METHODS: We identified sixty patients with acute scaphoid fractures at two centres who had been investigated with both plain radiographs and a CT (Computed Tomography) scan within 4 weeks of injury. The fractures were assessed by three observers at each centre using three commonly used classification systems and the 'long axis' method. RESULTS: Inter observer reliability: based on X-rays the 'long axis' measurement demonstrated substantial agreement (Intraclass Correlation Coefficient (ICC) =0.76) and was significantly more reliable than the Mayo (p < 0.01), the most reliable of the established classification systems with moderate levels of agreement (kappa = 0.56). Intra observer reliability: the long axis measurement demonstrated almost perfect agreement whether based on X-ray (ICC = 0.905) or CT (ICC = 0.900). CONCLUSIONS: This study describes a novel pragmatic 'long axis' method for the assessment of acute scaphoid fractures which demonstrates substantial inter and intra observer reliability. The 'long axis' measurement has clear potential benefits over traditional classification systems which should be explored in future clinical research.

An overview of realist evaluation for simulation-based education.

This article describes the key features of realist (realistic) evaluation and illustrates their application using, as an example, a simulation-based course for final year medical students. The use of simulation-based education (SBE) is increasing and so too is the evidence supporting its value as a powerful technique which can lead to substantial educational benefits. Accompanying these changes is a call for research into its use to be more theory-driven and to investigate both 'Did it work?' and as importantly 'Why did it work (or not)?' An evaluation methodology that is capable of answering both questions is realist evaluation. Realist evaluation is an emerging methodology that is suited to evaluating complex interventions such as SBE. The realist philosophy positions itself between positivist and constructivist paradigms and seeks to answer the question 'What works for whom, in what circumstances and why?' In seeking to answer this question, realist evaluation sets out to identify three fundamental components of an intervention, namely context, mechanism and outcome. Educational programmes work (successful outcomes) when theory-driven interventions (mechanisms) are applied to groups under appropriate conditions (context). Realist research uses a mixed methods (qualitative and quantitative) approach to gathering data in order to test the proposed context-mechanism-outcome (CMO) configurations of the intervention under investigation. Realist evaluation offers a valuable methodology for researchers investigating interventions utilising simulation-based education. By investigating and understanding the context, mechanisms and outcomes of SBE interventions, realist evaluation can provide the deeper level of understanding being called for.

Diverse landscapes beneath Pine Island Glacier influence ice flow.

The retreating Pine Island Glacier (PIG), West Antarctica, presently contributes ~5-10% of global sea-level rise. PIG's retreat rate has increased in recent decades with associated thinning migrating upstream into tributaries feeding the main glacier trunk. To project future change requires modelling that includes robust parameterisation of basal traction, the resistance to ice flow at the bed. However, most ice-sheet models estimate basal traction from satellite-derived surface velocity, without a priori knowledge of the key processes from which it is derived, namely friction at the ice-bed interface and form drag, and the resistance to ice flow that arises as ice deforms to negotiate bed topography. Here, we present high-resolution maps, acquired using ice-penetrating radar, of the bed topography across parts of PIG. Contrary to lower-resolution data currently used for ice-sheet models, these data show a contrasting topography across the ice-bed interface. We show that these diverse subglacial landscapes have an impact on ice flow, and present a challenge for modelling ice-sheet evolution and projecting global sea-level rise from ice-sheet loss.

Limited grounding-line advance onto the West Antarctic continental shelf in the easternmost Amundsen Sea Embayment during the last glacial period.

Precise knowledge about the extent of the West Antarctic Ice Sheet (WAIS) at the Last Glacial Maximum (LGM; c. 26.5-19 cal. ka BP) is important in order to 1) improve paleo-ice sheet reconstructions, 2) provide a robust empirical framework for calibrating paleo-ice sheet models, and 3) locate potential shelf refugia for Antarctic benthos during the last glacial period. However, reliable reconstructions are still lacking for many WAIS sectors, particularly for key areas on the outer continental shelf, where the LGM-ice sheet is assumed to have terminated. In many areas of the outer continental shelf around Antarctica, direct geological data for the presence or absence of grounded ice during the LGM is lacking because of post-LGM iceberg scouring. This also applies to most of the outer continental shelf in the Amundsen Sea. Here we present detailed marine geophysical and new geological data documenting a sequence of glaciomarine sediments up to ~12 m thick within the deep outer portion of Abbot Trough, a palaeo-ice stream trough on the outer shelf of the Amundsen Sea Embayment. The upper 2-3 meters of this sediment drape contain calcareous foraminifera of Holocene and (pre-)LGM age and, in combination with palaeomagnetic age constraints, indicate that continuous glaciomarine deposition persisted here since well before the LGM, possibly even since the last interglacial period. Our data therefore indicate that the LGM grounding line, whose exact location was previously uncertain, did not reach the shelf edge everywhere in the Amundsen Sea. The LGM grounding line position coincides with the crest of a distinct grounding-zone wedge ~100 km inland from the continental shelf edge. Thus, an area of ≥6000 km2 remained free of grounded ice through the last glacial cycle, requiring the LGM grounding line position to be re-located in this sector, and suggesting a new site at which Antarctic shelf benthos may have survived the last glacial period.

Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation.

The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies.

Classifying simulation-based studies using the description, justification and clarification framework: a review of simulation conference abstracts.

Introduction: Simulation-based medical education (SBME) is an accepted learning methodology with an ever-expanding evidence base. Concerns have been expressed that research output in SBME lacks explicit links to educational theory. Using the 'Description, Justification and Clarification' framework we have investigated the extent to which SBME conference abstracts declare the educational theory underpinning their studies. Methods: Abstracts from four major international SBME conferences (for 2014 and 2015) were reviewed. Abstracts were classified using the framework offered by Cook et al who classified studies published in major educational journals. Clarification studies are those which specifically declare and test their underpinning educational approach. Results: We reviewed 1398 conference abstracts which we classified as Description 54.4%, Justification 36.3% and Clarification 9.3%. The two most frequently declared educational theories were Cognitive Theories and Experiential Learning. Conclusion: The low proportion of Clarification studies found in the SBME conference abstracts reflects previous findings highlighting the lack of medical education studies that establish how and why SBME works. Researchers should be encouraged to declare their underpinning educational theories when presenting their work. Conference organisers play an important role in facilitating this through allowing sufficient word count in their submission criteria.

Percutaneous coronary angioplasty versus coronary artery bypass grafting in treatment of unprotected left main stenosis (NOBLE): a prospective, randomised, open-label, non-inferiority trial.

BACKGROUND: Coronary artery bypass grafting (CABG) is the standard treatment for revascularisation in patients with left main coronary artery disease, but use of percutaneous coronary intervention (PCI) for this indication is increasing. We aimed to compare PCI and CABG for treatment of left main coronary artery disease. METHODS: In this prospective, randomised, open-label, non-inferiority trial, patients with left main coronary artery disease were enrolled in 36 centres in northern Europe and randomised 1:1 to treatment with PCI or CABG. Eligible patients had stable angina pectoris, unstable angina pectoris, or non-ST-elevation myocardial infarction. Exclusion criteria were ST-elevation myocardial infarction within 24 h, being considered too high risk for CABG or PCI, or expected survival of less than 1 year. The primary endpoint was major adverse cardiac or cerebrovascular events (MACCE), a composite of all-cause mortality, non-procedural myocardial infarction, any repeat coronary revascularisation, and stroke. Non-inferiority of PCI to CABG required the lower end of the 95% CI not to exceed a hazard ratio (HR) of 1·35 after up to 5 years of follow-up. The intention-to-treat principle was used in the analysis if not specified otherwise. This trial is registered with ClinicalTrials.gov identifier, number NCT01496651. FINDINGS: Between Dec 9, 2008, and Jan 21, 2015, 1201 patients were randomly assigned, 598 to PCI and 603 to CABG, and 592 in each group entered analysis by intention to treat. Kaplan-Meier 5 year estimates of MACCE were 29% for PCI (121 events) and 19% for CABG (81 events), HR 1·48 (95% CI 1·11-1·96), exceeding the limit for non-inferiority, and CABG was significantly better than PCI (p=0·0066). As-treated estimates were 28% versus 19% (1·55, 1·18-2·04, p=0·0015). Comparing PCI with CABG, 5 year estimates were 12% versus 9% (1·07, 0·67-1·72, p=0·77) for all-cause mortality, 7% versus 2% (2·88, 1·40-5·90, p=0·0040) for non-procedural myocardial infarction, 16% versus 10% (1·50, 1·04-2·17, p=0·032) for any revascularisation, and 5% versus 2% (2·25, 0·93-5·48, p=0·073) for stroke. INTERPRETATION: The findings of this study suggest that CABG might be better than PCI for treatment of left main stem coronary artery disease. FUNDING: Biosensors, Aarhus University Hospital, and participating sites.

Anomalous Left Main Coronary Artery: Not Always a Simple Surgical Reimplantation.

We present the case of 56-year-old woman who required complex coronary artery bypass grafting for high-risk anomalous left main coronary artery (LMCA) originating from right coronary cusp including conventional reimplantation of the LMCA plus left internal mammary artery (LIMA) graft to the left anterior descending (LAD) and saphenous vein graft (SVG) to the left circumflex (LCx). On subsequent cardiac computed tomography screening and cardiac catheterization, the LIMA graft was occluded after just a few centimeters, but the SVG graft was patent with good run-off into the native LCx and also filled the LAD retrogradely. The reimplanted left main stem demonstrated at least moderate ostial stenosis although pressure wire assessment of this was not significant (fractional flow reserve 0.89), probably due to good retrograde filling of the LAD from the SVG to LCx, therefore, we did not proceed with ostial LMCA stenting. She remains on yearly review with a low threshold for further revascularization should the SVG to LCx develop progressive stenosis. This case illustrates how patients with anomalous LMCA may sometimes benefit from grafting in addition to conventional reimplantation.