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332 results on '"Niederer S"'

51. Mechanism of doxorubicin cardiotoxicity evaluated by integrating multiple molecular effects into a biophysical model

Author

Fernandez-Chas, M, Curtis, M J, and Niederer, S A

Subjects
Doxorubicin, Action Potentials, Calcium, Computer Simulation, Research Papers, Models, Biological, Cardiotoxicity, Ion Channels
Abstract

Background and PurposeDoxorubicin (DOX) is an effective cancer therapeutic agent but causes therapy‐limiting cardiotoxicity. The effects of DOX and its metabolite doxorubicinol (DOXL) on individual channels have been well characterized in isolation. However, it is unknown how the action and interaction of affected channels combine to generate the phenotypic cardiotoxic outcome. We sought to develop an in silico model that links drug effects on channels to action potential duration (APD) and intracellular Ca2+ concentration in order to address this gap in knowledge.Experimental ApproachWe first propose two methods to obtain, from published values, consensus drug effects on the currents of individual channels, transporters and pumps. Separately, we obtained equivalent values for APD and Ca2+ concentration (the readouts used as surrogates for cardiotoxicity). Once derived, the consensus effects on the currents were incorporated into established biophysical models of the cardiac myocyte and were refined adjusting the sarcoplasmic reticulum Ca2+ leak current (ILeak) until the consensus effects on APD and Ca2+ dynamics were replicated. Using factorial analysis, we then quantified the relative contribution of each channel to DOX and DOXL cardiotoxicity.Key ResultsThe factorial analysis identified the rapid delayed rectifying K+ current, the L‐type Ca2+ current and the sarcoplasmic reticulum ILeak as the targets primarily responsible for the cardiotoxic effects on APD and Ca2+ dynamics.Conclusions and ImplicationsThis study provides insight into the mechanisms of DOX‐induced cardiotoxicity and a framework for the development of future diagnostic and therapeutic strategies.

Published
2018
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52. 58 Characterisation of the structural and electrical impact of an atrial septal defect

Author

O’Neill, L, primary, Sim, I, additional, O’Hare, D, additional, Flyod, C, additional, Roney, C, additional, Whitaker, J, additional, Mukherjee, R, additional, Razeghi, O, additional, Niederer, S, additional, Alam, H, additional, Rosenthal, E, additional, Jones, M, additional, Wright, M, additional, Frigoila, A, additional, Williams, S, additional, and O’Neill, M, additional

Published
2019
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53. Differential effect with septal and apical RV pacing on ventricular activation in patients with left bundle branch block assessed by non-invasive electrical imaging and in silico modelling

Author

Jackson, T., primary, Claridge, S., additional, Behar, J., additional, Sieniewicz, B., additional, Gould, J., additional, Porter, B., additional, Sidhu, B., additional, Yao, C., additional, Lee, A., additional, Niederer, S., additional, and Rinaldi, C. A., additional

Published
2019
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54. Left ventricular outflow obstruction predicts increase in systolic pressure gradients and blood residence time after transcatheter mitral valve replacement

Author

De Vecchi, A., Marlevi, David, Nordsletten, D. A., Ntalas, I., Leipsic, J., Bapat, V., Rajani, R., Niederer, S. A., De Vecchi, A., Marlevi, David, Nordsletten, D. A., Ntalas, I., Leipsic, J., Bapat, V., Rajani, R., and Niederer, S. A.

Abstract

Left ventricular outflow tract (LVOT) obstruction is a relatively common consequence of transcatheter mitral valve replacement (TMVR). Although LVOT obstruction is associated with heart failure and adverse remodelling, its effects upon left ventricular hemodynamics remain poorly characterised. This study uses validated computational models to identify the LVOT obstruction degree that causes significant changes in ventricular hemodynamics after TMVR. Seven TMVR patients underwent personalised flow simulations based on pre-procedural imaging data. Different virtual valve configurations were simulated in each case, for a total of 32 simulations, and the resulting obstruction degree was correlated with pressure gradients and flow residence times. These simulations identified a threshold LVOT obstruction degree of 35%, beyond which significant deterioration of systolic function was observed. The mean increase from baseline (pre-TMVR) in the peak systolic pressure gradient rose from 5.7% to 30.1% above this threshold value. The average blood volume staying inside the ventricle for more than two cycles also increased from 4.4% to 57.5% for obstruction degrees above 35%, while the flow entering and leaving the ventricle within one cycle decreased by 13.9%. These results demonstrate the unique ability of modelling to predict the hemodynamic consequences of TMVR and to assist in the clinical decision-making process., QC 20190626

Published
2018
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55. Methodologies for Quantitative Systems Pharmacology (QSP) Models: Design and Estimation

Author

Ribba, B., Grimm, H. P., Agoram, B., Davies, M. R., Gadkar, K., Niederer, S., Van Riel, N., Timmis, J., Van Der Graaf, P. H., Computational Biology, Experimental Vascular Medicine, ACS - Amsterdam Cardiovascular Sciences, AGEM - Amsterdam Gastroenterology Endocrinology Metabolism, and ACS - Microcirculation

Subjects
Data_Science, Systems Biology/methods, Drug Design, Humans, Drug Discovery/methods, Congresses as Topic
Abstract

With the increased interest in the application of quantitative systems pharmacology (QSP) models within medicine research and development, there is an increasing need to formalize model development and verification aspects. In February 2016, a workshop was held at Roche Pharma Research and Early Development to focus discussions on two critical methodological aspects of QSP model development: optimal structural granularity and parameter estimation. We here report in a perspective article a summary of presentations and discussions.

Published
2017
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56. Restitution slope is principally determined by steady-state action potential duration

Author

Shattock, M, Park, K, Yang, H, Lee, A, Niederer, S, MacLeod, K, and Winter, J

Subjects
Cardiac & Cardiovascular Systems, I-KR, Action potential duration, heart, Electrical restitution, 1102 Cardiovascular Medicine And Haematology, Cardiac memory, GUINEA-PIG, DISPERSION, RATE DEPENDENCE, steady state, ALTERNANS, fetal restitution, action potentials, Restitution, RABBIT VENTRICULAR MYOCYTES, Science & Technology, musculoskeletal, neural, and ocular physiology, REPOLARIZATION, Cardiovascular System & Hematology, Cardiovascular System & Cardiology, cardiovascular system, HEART-FAILURE, FIBRILLATION, Life Sciences & Biomedicine, circulatory and respiratory physiology
Abstract

Aims: The steepness of the action potential duration (APD) restitution curve and local tissue refractoriness are both thought to play important roles in arrhythmogenesis. Despite this, there has been little recognition of the apparent association between steady-state APD and the slope of the restitution curve. The objective of this study was to test the hypothesis that restitution slope is determined by APD and to examine the relationship between restitution slope, refractoriness and susceptibility to VF. Methods and results: Experiments were conducted in isolated hearts and ventricular myocytes from adult guinea pigs and rabbits. Restitution curves were measured under control conditions and following intervention to prolong (clofilium, veratridine, bretylium, low [Ca]e, chronic transverse aortic constriction) or shorten (catecholamines, rapid pacing) ventricular APD. Despite markedly differing mechanisms of action, all interventions that prolonged the action potential led to a steepening of the restitution curve (and vice versa). Normalizing the restitution curve as a % of steady-state APD abolished the difference in restitution curves with all interventions. Effects on restitution were preserved when APD was modulated by current injection in myocytes pre-treated with the calcium chelator BAPTA-AM – to abolish the intracellular calcium transient. The non-linear relation between APD and the rate of repolarization of the action potential is shown to underpin the common influence of APD on the slope of the restitution curve. Susceptibility to VF was found to parallel changes in APD/refractoriness, rather than restitution slope. Conclusion(s): Steady-state APD is the principal determinant of the slope of the ventricular electrical restitution curve. In the absence of post-repolarization refractoriness, factors that prolong the action potential would be expected to steepen the restitution curve. However, concomitant changes in tissue refractoriness act to reduce susceptibility to sustained VF. Dependence on steady-state APD may contribute to the failure of restitution slope to predict sudden cardiac death.

Published
2017
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57. Mapping troll-like practices on twitter

Author

Borra, E., Niederer, S., Preuß, J., Weltevrede, E., Bounegru, L., Gray, J., Venturini, T., Mauri, M., and ASCA (FGw)

Abstract

Tactics such as trolling and the use of bots and “sock-puppet” accounts have been linked to the spread of political disinformation and propaganda online. In the lead up to the 2017 general elections for the Dutch parliament, journalists pointed to the use of sock puppets (i.e. false online identities assumed to deceive and influence opinion) by some political parties to amplify their messages online and to attack their political opponents on social media. In this recipe set we provide some methods that can be employed to detect and profile misleading information practices by taking troll- like behaviour around the 2017 Dutch election campaign as a case study. We focus on political troll-like practices, a term which we use in the narrower sense of attacks addressed at political representatives. We focus on three aspects of political trolling: the sources of troll-like activity, the characteristics of these practices and their targets.

Published
2017

58. The Human Touch

Author

Jansz, Jeroen, Niederer, S, Schuurmans, E, Ahsmann et al., B., and Department of Media and Communication

Published
2017

62. 533Does targeting the site of maximal electrical delay result in the optimal haemodynamic improvement; results from an international multi-centre registry

Author

Sieniewicz, B, primary, Behar, J, additional, Sohal, M, additional, Claridge, S, additional, Porter, B, additional, Niederer, S, additional, Gamble, J, additional, Betts, T R, additional, Jais, P, additional, Derval, N, additional, Spragg, D, additional, Steendijk, P, additional, Van Gelder, B, additional, Bracke, F A, additional, and Rinaldi, C A, additional

Published
2018
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63. 687Cardiomyoapthic aetiology affects the distribution of endocardial electrical latency; results from a multi-centre registry

Author

Sieniewicz, B, primary, Behar, J, additional, Sohal, M, additional, Porter, B, additional, Claridge, S, additional, Niederer, S, additional, Gamble, J, additional, Betts, T R, additional, Jais, P, additional, Derval, N, additional, Spragg, D, additional, Steendijk, P, additional, Van Gelder, BERRY, additional, Bracke, F A, additional, and Rinaldi, C A, additional

Published
2018
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64. P333Dual energy cardiac computed tomography to guide cardiac resynchronisation therapy: a feasibility study using coronary venous anatomy, scar and strain to guide optimal left ventricular lead placement

Author

Gould, J, primary, Behar, J, additional, Rajani, R, additional, Sieniewicz, B, additional, Porter, B, additional, Claridge, S, additional, Sidhu, B, additional, Razeghi, O, additional, Niederer, S, additional, Toth, D, additional, Mountney, P, additional, Haberland, U, additional, Carr-White, G, additional, Razavi, R, additional, and Rinaldi, C A, additional

Published
2018
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65. The Human Touch

Author

Ahsmann et al., B., Jansz, Jeroen, Niederer, S, Schuurmans, E, Ahsmann et al., B., Jansz, Jeroen, Niederer, S, and Schuurmans, E

Published
2017

71. Wisdom of the crowd or technicity of content? Wikipedia as a sociotechnical system

Author

Niederer, S., van Dijck, J., David, M., Millward, P., and ASCA (FGw)

Subjects
InformationSystems_MISCELLANEOUS
Abstract

Wikipedia is often considered as an example of ‘collaborative knowledge’. Researchers have contested the value of Wikipedia content on various accounts. Some have disputed the ability of anonymous amateurs to produce quality information, while others have contested Wikipedia’s claim to accuracy and neutrality. Even if these concerns about Wikipedia as an encyclopaedic genre are relevant, they misguidedly focus on human agents only. Wikipedia’s advance is not only enabled by its human resources, but is equally defined by the technological tools and managerial dynamics that structure and maintain its content. This article analyses the sociotechnical system — the intricate collaboration between human users and automated content agents — that defines Wikipedia as a knowledge instrument.

Published
2014

72. POSTERS (2)96CONTINUOUS VERSUS INTERMITTENT MONITORING FOR DETECTION OF SUBCLINICAL ATRIAL FIBRILLATION IN HIGH-RISK PATIENTS97HIGH DAY-TO-DAY INTRA-INDIVIDUAL REPRODUCIBILITY OF THE HEART RATE RESPONSE TO EXERCISE IN THE UK BIOBANK DATA98USE OF NOVEL GLOBAL ULTRASOUND IMAGING AND CONTINUEOUS DIPOLE DENSITY MAPPING TO GUIDE ABLATION IN MACRO-REENTRANT TACHYCARDIAS99ANTICOAGULATION AND THE RISK OF COMPLICATIONS IN PATIENTS UNDERGOING VT AND PVC ABLATION100NON-SUSTAINED VENTRICULAR TACHYCARDIA FREQUENTLY PRECEDES CARDIAC ARREST IN PATIENTS WITH BRUGADA SYNDROME101USING HIGH PRECISION HAEMODYNAMIC MEASUREMENTS TO ASSESS DIFFERENCES IN AV OPTIMUM BETWEEN DIFFERENT LEFT VENTRICULAR LEAD POSITIONS IN BIVENTRICULAR PACING102CAN WE PREDICT MEDIUM TERM MORTALITY FROM TRANSVENOUS LEAD EXTRACTION PRE-OPERATIVELY?103PREVENTION OF UNECESSARY ADMISSIONS IN ATRIAL FIBRILLATION104EPICARDIAL CATHETER ABLATION FOR VENTRICULAR TACHYCARDIA ON UNINTERRUPTED WARFARIN: A SAFE APPROACH?105HOW WELL DOES THE NATIONAL INSTITUTE OF CLINICAL EXCELLENCE (NICE) GUIDENCE ON TRANSIENT LOSS OF CONSCIOUSNESS (T-LoC) WORK IN A REAL WORLD? AN AUDIT OF THE SECOND STAGE SPECIALIST CARDIOVASCULAT ASSESSMENT AND DIAGNOSIS106DETECTION OF ATRIAL FIBRILLATION IN COMMUNITY LOCATIONS USING NOVEL TECHNOLOGY'S AS A METHOD OF STROKE PREVENTION IN THE OVER 65'S ASYMPTOMATIC POPULATION - SHOULD IT BECOME STANDARD PRACTISE?107HIGH-DOSE ISOPRENALINE INFUSION AS A METHOD OF INDUCTION OF ATRIAL FIBRILLATION: A MULTI-CENTRE, PLACEBO CONTROLLED CLINICAL TRIAL IN PATIENTS WITH VARYING ARRHYTHMIC RISK108PACEMAKER COMPLICATIONS IN A DISTRICT GENERAL HOSPITAL109CARDIAC RESYNCHRONISATION THERAPY: A TRADE-OFF BETWEEN LEFT VENTRICULAR VOLTAGE OUTPUT AND EJECTION FRACTION?110RAPID DETERIORATION IN LEFT VENTRICULAR FUNCTION AND ACUTE HEART FAILURE AFTER DUAL CHAMBER PACEMAKER INSERTION WITH RESOLUTION FOLLOWING BIVENTRICULAR PACING111LOCALLY PERSONALISED ATRIAL ELECTROPHYSIOLOGY MODELS FROM PENTARAY CATHETER MEASUREMENTS112EVALUATION OF SUBCUTANEOUS ICD VERSUS TRANSVENOUS ICD- A PROPENSITY MATCHED COST-EFFICACY ANALYSIS OF COMPLICATIONS & OUTCOMES113LOCALISING DRIVERS USING ORGANISATIONAL INDEX IN CONTACT MAPPING OF HUMAN PERSISTENT ATRIAL FIBRILLATION114RISK FACTORS FOR SUDDEN CARDIAC DEATH IN PAEDIATRIC HYPERTROPHIC CARDIOMYOPATHY: A SYSTEMATIC REVIEW AND META-ANALYSIS115EFFECT OF CATHETER STABILITY AND CONTACT FORCE ON VISITAG DENSITY DURING PULMONARY VEIN ISOLATION116HEPATIC CAPSULE ENHANCEMENT IS COMMONLY SEEN DURING MR-GUIDED ABLATION OF ATRIAL FLUTTER: A MECHANISTIC INSIGHT INTO PROCEDURAL PAIN117DOES HIGHER CONTACT FORCE IMPAIR LESION FORMATION AT THE CAVOTRICUSPID ISTHMUS? INSIGHTS FROM MR-GUIDED ABLATION OF ATRIAL FLUTTER118CLINICAL CHARACTERISATION OF A MALIGNANT SCN5A MUTATION IN CHILDHOOD119RADIOFREQUENCY ASSOCIATED VENTRICULAR FIBRILLATION120CONTRACTILE RESERVE EXPRESSED AS SYSTOLIC VELOCITY DOES NOT PREDICT RESPONSE TO CRT121DAY-CASE DEVICES - A RETROSPECTIVE STUDY USING PATIENT CODING DATA122PATIENTS UNDERGOING SVT ABLATION HAVE A HIGH INCIDENCE OF SECONDARY ARRHYTHMIA ON FOLLOW UP: IMPLICATIONS FOR PRE-PROCEDURE COUNSELLING123PROGNOSTIC ROLE OF HAEMOGLOBINN AND RED BLOOD CELL DITRIBUTION WIDTH IN PATIENTS WITH HEART FAILURE UNDERGOING CARDIAC RESYNCHRONIZATION THERAPY124REMOTE MONITORING AND FOLLOW UP DEVICES125A 20-YEAR, SINGLE-CENTRE EXPERIENCE OF IMPLANTABLE CARDIOVERTER DEFIBRILLATORS (ICD) IN CHILDREN: TIME TO CONSIDER THE SUBCUTANEOUS ICD?126EXPERIENCE OF MAGNETIC REASONANCE IMAGING (MEI) IN PATIENTS WITH MRI CONDITIONAL DEVICES127THE SINUS BRADYCARDIA SEEN IN ATHLETES IS NOT CAUSED BY ENHANCED VAGAL TONE BUT INSTEAD REFLECTS INTRINSIC CHANGES IN THE SINUS NODE REVEALED BY I (F) BLOCKADE128SUCCESSFUL DAY-CASE PACEMAKER IMPLANTATION - AN EIGHT YEAR SINGLE-CENTRE EXPERIENCE129LEFT VENTRICULAR INDEX MASS ASSOCIATED WITH ESC HYPERTROPHIC CARDIOMYOPATHY RISK SCORE IN PATIENTS WITH ICDs: A TERTIARY CENTRE HCM REGISTRY130A DGH EXPERIENCE OF DAY-CASE CARDIAC PACEMAKER IMPLANTATION131IS PRE-PROCEDURAL FASTING A NECESSITY FOR SAFE PACEMAKER IMPLANTATION?

Author

Philippsen, T., primary, Orini, M., primary, Martin, C.A., primary, Volkova, E., primary, Ormerod, J.O.M., primary, Sohaib, S.M.A., primary, Elamin, N., primary, Blake, Sarah, primary, Sawhney, V.S., primary, Ahmad, Saqib, primary, Waring, O.A.W., primary, Bowers, R.W., primary, Raiman, L., primary, Hazelwood, T.A.H., primary, Mills, R.K., primary, Corrado, C., primary, Honarbakhsh, S., primary, Von Maydell, A., primary, Norrish, G., primary, Chubb, H., primary, Toledano, M.T., primary, Ruiz, A., primary, van Zalen, J.J., primary, Foley, P.W., primary, Pearman, C.M., primary, Rehal, O., primary, Wong, L., primary, Brahmbhatt, D.H., primary, Khan, H., primary, Wardley, J., primary, Akbar, S., primary, Christensen, L.S., additional, Hansen, M.G., additional, Brandes, A., additional, Tinker, A., additional, Munroe, P.B., additional, Lambiase, P.D., additional, Honarbakhsh, S., additional, McLean, A., additional, Schilling, R.J., additional, Lane, J.D., additional, Chow, A., additional, Earley, M., additional, Hunter, R., additional, Khan, F., additional, Lambiase, P., additional, Sporton, S., additional, Dhinoja, M., additional, Camm, C.F., additional, Xavier, R., additional, de Sousa, M., additional, Betts, T.R., additional, Shun-Shin, M.J., additional, Wright, I., additional, Lim, E., additional, Lim, P.B., additional, Koawing, M., additional, Lefroy, D.C., additional, Linton, N.W.F., additional, Davies, D.W., additional, Peters, N.S., additional, Kanagaratnam, P., additional, Francis, D., additional, Whinnett, Z.I., additional, Khan, M., additional, Bowes, R., additional, Sahu, J., additional, Sheridan, P., additional, Rogers, D., additional, Kyriacou, A., additional, Kelland, N., additional, Lewis, N., additional, Lee, J., additional, Segall, E.T., additional, Diab, I., additional, Breitenstein, A.B., additional, Ullah, W.U., additional, Sporton, S.S., additional, Earley, M.E., additional, Finlay, M.F., additional, Dhinoja, M.D., additional, Schilling, R.J.S., additional, Hunter, R.H., additional, Ahmed, M, additional, Petkar, Sanjiv, additional, Davidson, N.C.D., additional, Stout, M.S., additional, Pearce, KP, additional, Leo, M., additional, Ginks, M.R., additional, Rajappan, K., additional, Bashir, Y., additional, Balasubramaniam, R.N., additional, Sopher, S.M., additional, Paisey, J.R., additional, Cheong, J., additional, Roy, D., additional, Adhya, S., additional, Williams, S., additional, O'Neill, M., additional, Niederer, S., additional, Providencia, R., additional, Srinivasan, N., additional, Ahsan, S., additional, Lowe, M., additional, Segal, O., additional, Hunter, R.J., additional, Finlay, M., additional, Earley, M.J., additional, Stella, S.E., additional, Cantwell, C.D., additional, Chowdhury, R.A., additional, Kim, S., additional, Linton, N., additional, Whinnett, Z., additional, Koa-Wing, M., additional, Lefroy, D., additional, Davies, D. Wyn, additional, Lim, P. Boon, additional, Qureshi, N., additional, Cantarutti, N.C., additional, Limongelli, G., additional, Elliott, P., additional, Kaski, J.P., additional, Williams, S.E., additional, Lal, K., additional, Harrison, J., additional, Whitaker, J., additional, Kiedrowicz, R., additional, Wright, M., additional, Schaeffter, T., additional, Razavi, R., additional, Karim, R., additional, Montanes, M.E.M., additional, Ella Field, E.F., additional, Walsh, H.W., additional, Callaghan, N.C., additional, Till, J.T., additional, Mangat, J.M., additional, Lowe, M.L., additional, Kaski, J.P.K., additional, Ruiz Duthil, A.D., additional, Li, A., additional, Saba, M.M., additional, Patel, N., additional, Beale, L., additional, Brickley, G, additional, Lloyd, G., additional, French, A., additional, Khavandi, A., additional, McCrea, W., additional, Barnes, E., additional, Chandrasekaran, B., additional, Parry, J., additional, Garth, L., additional, Chapman, J., additional, Todd, D., additional, Hobbs, J., additional, Modi, S., additional, Waktare, J., additional, Hall, M., additional, Gupta, D., additional, Snowdon, R., additional, Papageorgiou, N., additional, Providência, R., additional, Falconer, D., additional, Sewart, E., additional, Segal, O.R., additional, Ezzat, V., additional, Rowland, E., additional, Swift, M., additional, Charlton, P., additional, James, J., additional, Colling, A., additional, Starling, L., additional, Kontogeorgis, A., additional, Roses-Noguer, F., additional, Wong, T., additional, Jarman, J., additional, Clague, J., additional, Till, J., additional, Hawkins, M., additional, Burnell, S., additional, Coulson, J., additional, Smith, L.C., additional, Choudhury, M., additional, Oguguo, E., additional, Boyett, M., additional, Morris, G.M., additional, Flinn, W.L., additional, Chari, A., additional, Belham, M.R.D., additional, Pugh, P.J., additional, Somarakis, K, additional, Parasa, R, additional, Allata, A, additional, Hashim, H, additional, Mathew, T, additional, Kayasundar, S., additional, Venables, P., additional, Quinn, J., additional, Ivanova, J., additional, Brown, S., additional, Oliver, R., additional, Lyons, M., additional, Chuen, M., additional, Walsh, J., additional, Robinson, T., additional, Staniforth, A., additional, Ahsan, A., additional, and Jamil-Copley, S., additional

Published
2016
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73. ORAL ABSTRACTS (2)EP & Ablation19CARDIAC ABLATION PATIENT REPORTED OUTCOMES MEASURES (PROMS): ANALYSIS OF POST-ABLATION AND 1 YEAR FOLLOW-UP DATA20INTENTIONAL CORONARY VEIN EXIT AND CARBON DIOXIDE INSUFFLATION TO ALLOW SAFE SUBXIPHOID EPICARDIAL ACCESS FOR VENTRICULAR MAPPING AND ABLATION - FIRST EXPERIENCE21PACED FRACTIONATION DETECTION AS A TOOL FOR MAPPING SCARS IN VT22DOES USE OF CONTACT-FORCE SENSING CATHETERS IMPROVE THE OUTCOME OF ABLATION OF VENTRICULAR TACHYCARDIA?23RETROGRADE AORTIC ACCESS OF THE PULMONARY VENOUS ATRIUM PROVIDES EQUIVALENT OUTCOMES TO RIGHT ATRIAL OR TRANSEPTAL ACCESS OF THE LEFT ATRIUM IN PATIENTS WITH CONGENITAL HEART DISEASE24COMPUTATIONAL THREE-DIMENSION LEFT ATRIAL APPENDAGE WALL THICKNESS MAPS AND HISTOLOGICAL ANALYSIS TO GUIDE LEFT ATRIAL APPENDAGE ELECTRICAL ISOLATIONPacing & Devices25IDENTIFYING THE OPTIMAL LOCATION FOR LV ENDOCARIDAL PACING:RESULTS FROM A MULTICENTRE INTERNATIONAL REGISTRY OF LV ENDOCARDIAL PACING26UK MULTI-CENTRE REGISTRY OF TRANSVENOUS LEAD EXTRACTION: CLINICAL OUTCOME USING TRACTION, CUTTING SHEATHS AND LASER TECHNIQUES27SKIN FISTULA FORMATION - A NEW EXPERIENCE WITH THE NEW TYRX ABSORBABLE ANTIMICROVIAL ENVELOPE28BIFOCAL RIGHT VENTRICULAR PACING IN PATIENTS WITH FAILED CORONARY-SINUS LEAD IMPLANTS: LONG-TERM RESULTS FROM MULTICENTRE REGISTRY29REAL TIME X-MRI GUIDED LEFT VENTRICULAR LEAD IMPLANTATION FOR TARGETED DELIVERY OF CARDIAC RESYNCHRONIZATION THERAPY30ACUTE AND CHRONIC PERFORMANCE OF COMMUNICATING LEADLESS ANTI-TACHYCARDIA PACEMAKER AND SUBCUTANEOUS IMPLANTABLE DEFIBRILLATOR

Author

Evans, J.M., primary, Silberbauer, John, primary, Glover, B., primary, Kontogeorgis, A., primary, McLellan, A.J.A., primary, Panikker, S., primary, Sieniewicz, B.J., primary, Martin, C.A., primary, Burg, M.R., primary, Providencia, R., primary, Behar, J.M., primary, Burke, M.C., primary, Withers, K.L., additional, White, J., additional, Lencioni, M., additional, Carolan-Rees, G., additional, Wood, K.A., additional, Patrick, H., additional, Griffith, M., additional, Gomes, J., additional, Kirubakaran, S., additional, O'Nunain, S., additional, Bencat, M., additional, McCready, J., additional, Michael, K., additional, Hashemi, J., additional, Gupta, D., additional, Akl, S., additional, Redfearn, D., additional, Lim, E., additional, Panikker, S., additional, Butcher, C., additional, Khan, H., additional, Mantziari, L., additional, Jarman, J.W.E., additional, Hussain, W., additional, Jones, D., additional, Clague, J.R., additional, Ernst, S., additional, Markides, V., additional, Wong, T., additional, Ezzat, V.A., additional, Schilling, R.J., additional, Lowe, M.D., additional, Whitaker, J., additional, Virmani, R., additional, Kutys, R., additional, Fastl, T., additional, Haldar, S., additional, O'Neill, M., additional, Corado, C., additional, Nicol, E., additional, Foran, J.P., additional, Niederer, S., additional, Behar, J., additional, Sohal, M., additional, Jais, P., additional, Derval, N., additional, Spragg, D., additional, Van Gelder, B., additional, Bracke, F., additional, Steendijk, P., additional, Rinaldi, C.A., additional, Chooneea, B., additional, Gajendragadkar, P.R., additional, Ahsan, S., additional, Begley, D.A., additional, Dhinoja, M., additional, Earley, M.J., additional, Finlay, M., additional, Grace, A.A., additional, Heck, P.M., additional, Hunter, R.J., additional, Lambiase, P.D., additional, Rowland, E., additional, Segal, O.R., additional, Sporton, S., additional, Virdee, M.S., additional, Chow, A., additional, Apap Bologna, R., additional, Camilleri, W., additional, Sammut, M.A., additional, Aquilina, O., additional, Barra, S., additional, Papageorgiou, N., additional, Falconer, D., additional, Duehmke, R., additional, Rehal, O., additional, Ezzat, V., additional, Ioannou, A., additional, Segal, O., additional, Lowe, M., additional, Lambiase, P., additional, Agarwal, S., additional, Chow, A.W., additional, Toth, D., additional, Mountney, P., additional, Reiml, S., additional, Panayioutu, M., additional, Brost, A., additional, Fahn, B., additional, Patel, N.R., additional, Claridge, S., additional, Jackson, T., additional, Adhya, S., additional, Sieniwicz, B., additional, Razavi, R., additional, Rhode, K., additional, Tjong, F.V.Y., additional, Brouwer, T.F., additional, Koop, B., additional, Soltis, B., additional, Shuros, A., additional, and Knops, R.E., additional

Published
2016
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74. An automatic service for the personalization of ventricular cardiac meshes

Author

Lamata de la Orden, Pablo, Sinclair, M., Kerfoot, E., Lee, A., Crozier, A., Blazevic, B., Land, S., Lewandowski, A. J., Barber, D., Niederer, S., and Smith, N.

Subjects
ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION
Abstract

Computational cardiac physiology has great potential to improve the management of cardiovascular diseases. One of the main bottlenecks in this field is the customization of the computational model to the anatomical and physiological status of the patient. We present a fully automatic service for the geometrical personalization of cardiac ventricular meshes with high-order interpolation from segmented images. The method is versatile (able to work with different species and disease conditions) and robust (fully automatic results fulfilling accuracy and quality requirements in 87% of 255 cases). Results also illustrate the capability to minimize the impact of segmentation errors, to overcome the sparse resolution of dynamic studies and to remove the sometimes unnecessary anatomical detail of papillary and trabecular structures. The smooth meshes produced can be used to simulate cardiac function, and in particular mechanics, or can be used as diagnostic descriptors of anatomical shape by cardiologists. This fully automatic service is deployed in a cloud infrastructure, and has been made available and accessible to the scientific community.

Published
2013
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75. National Web Studies

Author

Rogers, R., Weltevrede, E., Borra, E., Niederer, S., Hartley, J., Burgess, J., Bruns, A., and ASCA (FGw)

Subjects
Web standards, Web analytics, World Wide Web, Engineering, Web 2.0, Web development, business.industry, Web design, Web page, Library science, Web search engine, business, Social Semantic Web
Abstract

In 2007, Ricardo Baeza-Yates and colleagues at Yahoo! Research in Barcelonapublishedareviewarticleon‘‘characterizationsofnationalwebdomains’’inwhichthey sketched an emerging field that we would like to call national web studies.Of particular interest in the article is the distinction the authors made betweenstudies in the 1990s on the characteristics of

Published
2013
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76. At the heart of computational modelling

Author

Niederer, S A and Smith, N P

Subjects
Topical Reviews, Animals, Humans, Reproducibility of Results, Computer Simulation, Heart, Models, Biological
Abstract

The link between experimental data and biophysically based mathematical models is key to computational simulation meeting its potential to provide physiological insight. However, despite the importance of this link, scrutiny and analysis of the processes by which models are parameterised from data are currently lacking. While this situation is common to many areas of physiological modelling, to provide a concrete context, we use examples drawn from detailed models of cardiac electro-mechanics. Using this biophysically detailed cohort of models we highlight the specific issues of model parameterization and propose this process can be separated into three stages: observation, fitting and validation. Finally, future research challenges and directions in this area are discussed.

Published
2012

77. National Web Studies: Mapping Iran Online

Author

Rogers, R., Weltevrede, E., Niederer, S., Borra, E., and ASCA (FGw)

Abstract

This work offers an approach to conceptualizing, demarcating and analyzing a national web. Instead of defining a priori the types of websites to be included in a national web, the approach put forward here makes use of web devices (platforms and engines) that purport to provide (ranked) lists of URLs relevant to a particular country. Once gathered in such a manner, the websites are studied for their properties, following certain of the common measures (such as responsiveness and page age), and repurposing them to speak in terms of the health of a national web: Are sites lively, or neglected? The case study in question is Iran, which is special for the degree of Internet censorship undertaken by the state. Despite the widespread censorship, we have found a highly responsive Iranian web. We also report on the relationship between blockage, responsiveness and freshness, i.e., whether blocked sites are still up, and also whether they have been recently updated. Blocked yet blogging portions of the Iranian web show strong indications of an active Internet censorship circumvention culture. In seeking to answer, additionally, whether censorship has killed content, a textual analysis shows continued use of language considered critical by the regime, thereby indicating a dearth of self-censorship, at least for websites that are recommended by the leading Iranian platform, Balatarin. The study concludes with the implications of the approach put forward for national web studies, including a description of the benefits of a national web health index.

Published
2012

78. Simulating human cardiac physiology on clinical time-scales

Author

Niederer, S, Mitchell, L, Smith, N, and Plank, G

Subjects
strong scalability, Science & Technology, monodomain model, personalized health care, Physiology, Life Sciences & Biomedicine
Abstract

In this study, the feasibility of conducting in silico experiments in near-realtime with anatomically realistic, biophysically detailed models of human cardiac electrophysiology is demonstrated using a current national high-performance computing facility. The required performance is achieved by integrating and optimizing load balancing and parallel I/O, which lead to strongly scalable simulations up to 16,384 compute cores. This degree of parallelization enables computer simulations of human cardiac electrophysiology at 240 times slower than real time and activation times can be simulated in approximately 1 min. This unprecedented speed suffices requirements for introducing in silico experimentation into a clinical workflow.

Published
2011

80. Devices & Sudden death31Quadripolar left ventricular leads should be the gold standard in crt due to efficacy and cost effectiveness: an analysis from a multi-centre uk registry32Cardiac computed tomography is a feasible imaging modality for pre procedural planning in patients undergoing upgrade from pacemakers to CRT33Derivation and external validation of a cardiac resynchronization therapy response score34Generation and validation of transformation coefficients to reconstruct 12-lead electrocardiograms from 3 subcutaneous implantable cardioverter defibrillator electrodes35Risk stratification of sudden cardiac death: positive evaluation of novel surface electrocardiogram biomarkers in a brugada syndrome cohort36The real world cost of cardiac implantable electronic device transvenous extractions37Advances in technology for rapid and reliable ecg acquisition38Excellent symptom rhythm correlation in patients with palpitations using a novel smartphone based event recorder39Differential ventricular repolarisation responses during sympathetic surge versus sustained sympathetic stimulation–in vivo evidence from humans40Approaching a fluro free daily life ep lab41Development and validation of the cardiff cardiac ablation prom (C-CAP) for patients with symptomatic cardiac arrhythmias42The changing tide of novel oral anti-coagulant use in england

Author

Behar, J.M., primary, Providência, R., primary, Cronbach, P.L., primary, Siddiqui, S., primary, Brough, C.E.P., primary, Ara, F.A., primary, Newham, W.G., primary, Ng, F.S., primary, Ayala-Paredes, F., primary, Withers, K.L., primary, Hayward, C., primary, Chin, H.M.S., additional, Fearn, S., additional, Omerod, J., additional, Gamble, J., additional, Foley, P.W.X., additional, Bostock, J., additional, Claridge, S., additional, Jackson, T., additional, Sohal, M., additional, Razavi, R., additional, Betts, T.R., additional, Herring, N., additional, Rinaldi, C.A., additional, Pourmorteza, A., additional, McVeigh, E., additional, Niederer, S., additional, Preston, R., additional, Carr-White, G., additional, Rajani, R., additional, Boveda, S., additional, Defaye, P., additional, Barra, S., additional, Babu, G., additional, Ang, R., additional, Algalarrondo, V., additional, Bouzeman, A., additional, Ahsan, S., additional, Deharo, JC., additional, Sporton, S., additional, Segal, O., additional, Klug, D., additional, Lambiase, P., additional, Sadoul, N., additional, Agarwal, S., additional, Piot, O., additional, Chow, A., additional, Périer, M.C., additional, Fauchier, L., additional, Babuty, D., additional, Lowe, M., additional, Leclercq, C., additional, Bordachar, P., additional, Marijon, E., additional, Wilson, D.G., additional, Panfilo, D., additional, Greenhut, S.E., additional, Stegemann, B., additional, Morgan, J.M., additional, Nicolson, W.B., additional, Li, A., additional, Behr, E.R., additional, Ng, G.A., additional, Raman, G., additional, Belchambers, S., additional, Rao, A., additional, Wright, D.J., additional, John, I., additional, Crockford, C., additional, Kaba, R.A., additional, Begg, G.A., additional, Tayebjee, M.H., additional, Leong, K.M.W., additional, Hu, M.K., additional, Kanapeckaite, L., additional, Roney, C.H., additional, Lim, P.B., additional, Harding, S.E., additional, Peters, N.S., additional, Varnava, A., additional, Kanagaratnam, P., additional, Roux, J-F, additional, Badra, M., additional, White, J., additional, Lencioni, M., additional, Carolan-Rees, G., additional, Patrick, H., additional, Griffith, M., additional, Patel, H., additional, Spiesshoefer, J., additional, Morley-Smith, A., additional, Patel, K., additional, Rosen, S., additional, DiMario, C., additional, Lyon, A., additional, and Cowie, M., additional

Published
2015
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83. Urban screens reader

Author

McQuire, S., Martin, M., Niederer, S., and ASCA (FGw)

Published
2009

84. Introduction

Author

McQuire, S., Martin, M., Niederer, S., and ASCA (FGw)

Published
2009

94. POSTER SESSION 2, HRC 2013

Author

Ang, R., primary, Birnbaumer, L., additional, Gourine, A. V., additional, Tinker, A., additional, Hamilton, R. M., additional, Strandberg, L., additional, Cui, X., additional, Rath, A., additional, Liu, J., additional, Sirigam, V., additional, Ackerley, C., additional, Jaeggi, E., additional, Backx, P., additional, Silverman, E. D., additional, Debney, M. T., additional, Ng, F. S., additional, Lyon, A. R., additional, Peters, N. S., additional, Opel, A., additional, Nobles, M., additional, Winter, J., additional, Chin, S. H., additional, Brack, K. E., additional, Ng, G. A., additional, Finlay, M. C., additional, Xu, L., additional, Lane, J., additional, Lowe, M., additional, Ben-Simon, R., additional, Bhar-Amato, J., additional, Hussain, Q., additional, Sebastian, S., additional, Taggart, P., additional, Lambiase, P. D., additional, Almeida, T. P., additional, Salinet, J., additional, Chu, G. S., additional, Schlindwein, F. S., additional, Williams, S. E., additional, Linton, N. W. F., additional, Harrison, J., additional, Wright, M., additional, Plank, G., additional, O'Neill, M. D., additional, Niederer, S., additional, Raine, D. T., additional, Langley, P., additional, Shepherd, E., additional, Lord, S., additional, Murray, S., additional, Bourke, J. P., additional, Chen, Z., additional, Hanson, B., additional, Sohal, M., additional, Child, N., additional, Sammut, E., additional, Jackson, T., additional, Shetty, A., additional, Bostock, J., additional, Gill, J., additional, Carr-White, G., additional, Rinaldi, C. A., additional, Linton, N. W., additional, Rhode, K., additional, Barrows, S., additional, Jones, K., additional, and Porter, N., additional

Published
2013
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97. Integration of different cardiac electrophysiological models into a single simulation pipeline

Author

Camara, O., primary, Sermesant, M., additional, Lamata, P., additional, Wang, L., additional, Pop, M., additional, Relan, J., additional, De Craene, M., additional, Delingette, H., additional, Liu, H., additional, Niederer, S., additional, Pashaei, A., additional, Plank, G., additional, Romero, D., additional, Sebastian, R., additional, Wong, K. C. L., additional, Zhang, H., additional, Ayache, N., additional, Frangi, A. F., additional, Shi, P., additional, Smith, N. P, additional, and Wright, G. A., additional

Published
2012
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98. Inter-model consistency and complementarity: Learning from ex-vivo imaging and electrophysiological data towards an integrated understanding of cardiac physiology

Author

Camara, O., primary, Sermesant, M., additional, Lamata, P., additional, Wang, L., additional, Pop, M., additional, Relan, J., additional, De Craene, M., additional, Delingette, H., additional, Liu, H., additional, Niederer, S., additional, Pashaei, A., additional, Plank, G., additional, Romero, D., additional, Sebastian, R., additional, Wong, K.C.L., additional, Zhang, H., additional, Ayache, N., additional, Frangi, A.F., additional, Shi, P., additional, Smith, N.P., additional, and Wright, G.A., additional

Published
2011
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99. Hypokalaemia induces Ca2+ overload and Ca2+ waves in ventricular myocytes by reducing Na+,K+-ATPase α2 activity.

Author

Aronsen, J. M., Skogestad, J., Lewalle, A., Louch, W. E., Hougen, K., Stokke, M. K., Swift, F., Niederer, S., Smith, N. P., Sejersted, O. M., and Sjaastad, I.

Subjects
HYPOKALEMIA, VENTRICULAR arrhythmia, MUSCLE cells, PHYSIOLOGICAL effects of potassium channels, CALCIUM channels
Abstract

Key points Hypokalaemia is a risk factor for development of ventricular arrhythmias., In rat ventricular myocytes, low extracellular K+ (corresponding to clinical moderate hypokalaemia) increased Ca2+ wave probability, Ca2+ transient amplitude, sarcoplasmic reticulum (SR) Ca2+ load and induced SR Ca2+ leak., Low extracellular K+ reduced Na+,K+-ATPase (NKA) activity and hyperpolarized the resting membrane potential in ventricular myocytes. Both experimental data and modelling indicate that reduced NKA activity and subsequent Na+ accumulation sensed by the Na+, Ca2+ exchanger (NCX) lead to increased Ca2+ transient amplitude despite concomitant hyperpolarization of the resting membrane potential., Low extracellular K+ induced Ca2+ overload by lowering NKA α2 activity. Triggered ventricular arrhythmias in patients with hypokalaemia may therefore be attributed to reduced NCX forward mode activity linked to an effect on the NKA α2 isoform., Abstract Hypokalaemia is a risk factor for development of ventricular arrhythmias. The aim of this study was to determine the cellular mechanisms leading to triggering of arrhythmias in ventricular myocytes exposed to low Ko. Low Ko, corresponding to moderate hypokalaemia, increased Ca2+ transient amplitude, sarcoplasmic reticulum (SR) Ca2+ load, SR Ca2+ leak and Ca2+ wave probability in field stimulated rat ventricular myocytes. The mechanisms leading to Ca2+ overload were examined. Low Ko reduced Na+,K+-ATPase (NKA) currents, increased cytosolic Na+ concentration and increased the Na+ level sensed by the Na+, Ca2+ exchanger (NCX). Low Ko also hyperpolarized the resting membrane potential (RMP) without significant alterations in action potential duration. Experiments in voltage clamped and field stimulated ventricular myocytes, along with mathematical modelling, suggested that low Ko increases the Ca2+ transient amplitude by reducing NKA activity despite hyperpolarization of the RMP. Selective inhibition of the NKA α2 isoform by low dose ouabain abolished the ability of low Ko to reduce NKA currents, to increase Na+ levels sensed by NCX and to increase the Ca2+ transient amplitude. We conclude that low Ko, within the range of moderate hypokalaemia, increases Ca2+ levels in ventricular myocytes by reducing the pumping rate of the NKA α2 isoform with subsequent Na+ accumulation sensed by the NCX. These data highlight reduced NKA α2-mediated control of NCX activity as a possible mechanism underlying triggered ventricular arrhythmias in patients with hypokalaemia. [ABSTRACT FROM AUTHOR]

Published
2015
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