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Background: The best choice of defibrillator lead in patients with routine implantable cardioverter-defibrillator (ICD) is not settled. Traditionally, most physicians prefer dual-coil leads but the use of single-coil leads is increasing.Objective: The purpose of this study was to compare clinical outcomes in patients with single- and dual-coil leads.Methods: All 4769 Danish patients 18 years or older with first-time ICD implants from 2007 to 2011 were included from the Danish Pacemaker and ICD Register. Defibrillator leads were 38.9% single-coil leads and 61.1% dual-coil leads. The primary end point was all-cause mortality. Secondary end points were lowest successful energy at implant defibrillation testing, first shock failure in spontaneous arrhythmias, structural lead failure, and lead extraction outcomes.Results: Single-coil leads were associated with lower all-cause mortality with an adjusted hazard ratio of 0.85 (95% confidence interval 0.73-0.99; P = .04). This finding was robust in a supplementary propensity score-matched analysis. However, dual-coil leads were used in patients with slightly higher preimplant morbidity, making residual confounding by indication the most likely explanation for the observed association between lead type and mortality. The lowest successful defibrillation energy was higher using single-coil leads (23.2 ± 4.3 J vs 22.1 ± 3.9 J; P < .001). No significant differences were observed for other secondary end points showing high shock efficacies and low rates of lead failures and extraction complications.Conclusion: Shock efficacy is high for modern ICD systems. The choice between single-coil and dual-coil defibrillator leads is unlikely to have a clinically significant impact on patient outcomes in routine ICD implants. [ABSTRACT FROM AUTHOR]

A hybrid model for the prediction of ground-borne vibration due to discrete wheel and rail irregularities, such as wheel flats, dipped welds and insulated rail joints, is presented. The hybrid model combines the simulation of vertical wheel-rail contact force in the time domain, accounting for parametric excitation due to sleeper periodicity and impact excitation induced by loss of wheel-rail contact, and calculation of ground-borne vibration in the frequency-wavenumber domain considering a layered soil model. The model is demonstrated by investigating the influence of wheel flat size and vehicle speed on maximum vertical wheel-rail contact force and free field ground vibration. It is shown that magnitudes of impact load and ground vibration are increasing with increasing wheel flat length (and depth), but the influence of vehicle speed is not as evident. Higher vehicle speeds often lead to loss of wheel-rail contact and severe impact loads but the frequency content of such impact loads is shifted to higher frequencies which may be less significant for ground vibration. [ABSTRACT FROM AUTHOR]

Background Recalled St. Jude Medical Riata defibrillator leads are prone to insulation failures with externalized conductors (ECs). Longitudinal studies are needed to guide lead management. Objective The purpose of this study was to describe the dynamic nature of EC and the association with electrical abnormalities and lead extraction outcomes. Methods A nationwide cohort established in 2012 of 295 patients with recalled Riata leads with dwell time 5.1 ± 1.1 years, 34 ECs, and 19 electrical abnormalities were followed until death, lead discontinuation with fluoroscopy, or a new 2013 screening with fluoroscopy and device interrogation. Results Fluoroscopic follow-up of 239 patients with normal baseline fluoroscopy revealed incident overt EC in 8 leads and borderline EC in 2 leads after 1.1 ± 0.2 years, with an incidence rate of 3.7 per 100 person-years (95% confidence interval 2.0–6.9). Fluoroscopic follow-up in 27 patients with baseline EC showed an increase in EC length of 4 ± 1 mm ( P <.001) after 1.1 ± 0.3 years. Electrical follow-up in 276 patients with normal baseline electrical function demonstrated 20 incident electrical abnormalities after 1.0 ± 0.3 years, with an incidence rate of 7.1 per 100 person-years (95% confidence interval 4.6–11.0). This rate was significantly higher in leads with baseline EC, with an adjusted incidence rate ratio of 4.4 (95% confidence interval 1.7–11.5, P = .002). In 15 extractions, all leads were removed, with 2 major complications. Conclusion The development of EC is a dynamic process despite long lead dwell time. ECs are associated with a higher risk of electrical abnormalities. Therefore, lead replacement should be considered, especially in patients with a long life expectancy. [ABSTRACT FROM AUTHOR]

Background The St Jude Medical Riata lead advisory was issued owing to insulation failures. The impact of this advisory on patients’ well-being is unknown. Objectives The objectives of this study were to describe the acute impact of the Riata advisory on patients’ well-being and psychological functioning and to examine changes over time. Methods Patients with active Riata leads completed standardized and validated patient-reported outcomes (PROs) in connection with a nationwide fluoroscopic screening with 12-month follow-up. They were matched (1:1) on age, sex, and implant indication with nonadvisory controls for baseline comparisons. Cohen’s effect size d was used to determine the clinical relevance of the estimated adjusted mean differences (small, d = 0.20; moderate, d = 0.50; large, d ≥ 0.80). Results Of all Riata patients, 86% (256 of 299) completed baseline PROs and 70% (210 of 299) follow-up PROs. Riata patients reported poorer device acceptance ( d = −0.28; P = .001) and increased device-related concerns ( d = 0.29; P < .001) as compared with matched nonadvisory controls. There were no differences in symptoms of depression ( d = 0.13; P = .13). Female sex was an independent predictor of a high advisory impact on general well-being as assessed with a purpose-designed question (odds ratio 2.24; P = .04). Device-related concerns decreased over time ( d = −0.17; P = .002), but no changes were seen for other PROs. Conclusion The Riata advisory is associated with a persistent small reduction in device acceptance and a small increase in device-related concerns with minimal improvement over time. Female sex is a predictor of a high negative advisory impact on general well-being. A need for counseling may arise in vulnerable subsets of patients. [ABSTRACT FROM AUTHOR]

A methodology for the optimisation of a prescribed track gauge variation (gauge widening) in the switch panel of a railway turnout (switch and crossing, S&C) is presented. The aim is to reduce rail profile degradation. A holistic approach is applied, where both routes and travel directions (moves) of traffic in the switch panel are considered simultaneously. The problem is formulated as a multi-objective minimisation problem which is solved using a genetic-type optimisation algorithm which provides a set of Pareto optimal solutions. The dynamic vehicle-tumout interaction is evaluated using a multi-body simulation tool and the energy dissipation in the wheel-rail Contacts is used for the assessment of gauge parameters. Two different vehicle models are used, one freight car and one passenger train set, and a stochastic spread in wheel profile and wheel-rail friction coefficient is accounted for. It is found that gauge configurations with a large gauge-widening amplitude for the stock rail on the field side are optimal for both the through and diverging routes, while the results for the gauge side show a larger route dependence. The optimal gauge configurations are observed to be similar for both vehicle types. [ABSTRACT FROM AUTHOR]

A time-domain method for the simulation of general three-dimensional dynamic interaction between a vehicle and a curved railway track, accounting for a prescribed relative wheel-rail displacement excitation in a wide frequency range (up to several hundred Hz), is presented. The simulation model is able to capture the low-frequency vehicle dynamics simultaneously due to curving and the high-frequency track dynamics due to the excitation by, for example, the short-pitch corrugation on the low rail. The adopted multibody dynamics formulation considers inertia forces, such as centrifugal and Coriolis forces, as well as the structural flexibility of vehicle and track components. To represent a wheel/rail surface irregularity, isoparametric two-dimensional elements able to describe generally curved surface shapes are used. The computational effort is reduced by including only one bogie in the vehicle model. The influence of the low-frequency vehicle dynamics of the remaining parts of the vehicle is considered by pre-calculated look-up tables of forces and moments acting in the secondary suspension. For a track model taken as rigid, good agreement is observed between the results calculated with the presented model and a commercial software. The features of the model are demonstrated by a number of numerical examples. The influence of the structural flexibility of the wheelset and track on wheel-rail contact forces is investigated. For a discrete rail irregularity excitation, it is shown that the longitudinal creep force is significantly influenced by the wheelset eigenmodes. The introduction of a velocity-dependent friction law is found to induce an oscillation in the tangential contact force on the low rail with a frequency corresponding to the first anti-symmetric torsional mode of the wheelset. Further, under the application of driving moments on the two wheelsets and excitation by a discrete irregularity on the high rail, the frequency content of the tangential contact forces on the low rail is significantly influenced by the P2 resonance as well as by several wheelset eigenmodes. [ABSTRACT FROM AUTHOR]

Results from an extensive field test performed in a UIC60-760-1:15 turnout on Svealandsbanan in Sweden are reported. Lateral and vertical wheel-rail contact forces were measured by a wheelset instrumented with strain gauges on the wheel discs. The test train with axle load 25 tonnes passed through the turnout in the main and diverging routes and in the facing and trailing moves. The influences of train speed and moving direction on the magnitude and the position of the maximum lateral contact force in the diverging route of the switch panel, and the influences of train speed, moving direction and route on the maximum vertical contact force in the crossing panel, are investigated. Measured contact forces are compared with calculated forces for a validation of two previously developed numerical models. The magnitude and position of the calculated maximum lateral contact forces are in good agreement with the corresponding measured values. Both measurements and numerical simulations show an increase in maximum lateral contact force with increasing train speed in both the facing and trailing moves. The facing move of the diverging route leads to the highest lateral contact forces in the switch panel. The maximum vertical contact force is not influenced significantly by whether the train is moving in the facing or trailing moves. However, the train route (main or diverging) has a large influence on the maximum vertical contact force at the crossing. [ABSTRACT FROM AUTHOR]

Dynamic train–track interaction is more complex in railway turnouts (switches and crossings) than that in ordinary tangent or curved tracks. Multiple contacts between wheel and rail are common, and severe impact loads with broad frequency contents are induced, when nominal wheel–rail contact conditions are disturbed because of the continuous variation in rail profiles and the discontinuities in the crossing panel. The absence of transition curves at the entry and exit of the turnout, and the cant deficiency, leads to large wheel–rail contact forces and passenger discomfort when the train is switching into the turnout track. Two alternative multibody system (MBS) models of dynamic interaction between train and a standard turnout design are developed. The first model is derived using a commercial MBS software. The second model is based on a multibody dynamics formulation, which may account for the structural flexibility of train and track components (based on finite element models and coordinate reduction methods). The variation in rail profile is accounted for by sampling the cross-section of each rail at several positions along the turnout. Contact between the back of the wheel flange and the check rail, when the wheelset is steered through the crossing, is considered. Good agreement in results from the two models is observed when the track model is taken as rigid. [ABSTRACT FROM AUTHOR]

High-frequency train-track interaction and mechanisms of wheel/rail wear that is non-uniform in magnitude around/along the running surface are surveyed. Causes, consequences and suggested remedies to relieve the problems are discussed for three types of irregular wheel/rail wear: (1) short-pitch rail corrugation on tangent tracks and large radius curves, (2) wheel corrugation as caused by tread braking, and (3) wheel polygonalisation. The state-of-the-art in modelling of dynamic train-track interaction in conjunction with prediction of irregular wear is reviewed. [ABSTRACT FROM AUTHOR]

This paper presents a finite element model of a railway crossing panel for use in multibody simulations (MBS). It is a two-layer track model with rails and sleepers represented by beam elements that use linear bushings for rail fastenings and non-linear bushings for ballast. The model is calibrated and validated to measurement data from a comprehensively instrumented switch and crossing demonstrator installed in the Austrian railway network as a part of the European research programme Shift2Rail. The validation concerns the capability of the model to capture the structural response of the crossing panel under traffic loading after calibration of physical track parameters to realistic values. The structural response is measured in the form of displacements, strains, and sleeper-ballast contact forces. It is shown that the developed model can represent the measured track responses well and that it was necessary to account for a varying sleeper-ballast gap distribution along the crossing transition sleeper to obtain good agreement. The calibration uses Latin hypercube samples to explore the parameter space in a sensitivity analysis before a parameter optimisation is performed using a gradient-based method on a response surface built from a polyharmonic spline. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is available in the text. Background: Patients with nonischemic systolic heart failure (HF) have increased risk of sudden cardiac death (SCD) and death from progressive pump failure. Whether the risk of SCD changes over time is unknown. We seek here to investigate the relation between duration of HF, mode of death, and effect of implantable cardioverter-defibrillator implantation. Methods and Results: We examined the risk of all-cause death and SCD according to the duration of HF among patients with nonischemic systolic HF enrolled in the DANISH (Danish Study to Assess the Efficacy of ICDs in Patients with Non-ischemic Systolic Heart Failure on Mortality). In all, 1116 patients were included. Patients were divided according to quartiles of HF duration (≤8, 9≤18, 19≤65, and ≥66 months). Patients with the longest duration of HF were older, more often men, had more comorbidity, and more often received a cardiac resynchronization therapy device. Doubling of HF duration was an independent predictor of both all-cause mortality (hazard ratio [HR], 1.27; 95% CI, 1.17–1.38; P <0.0001), and SCD (HR, 1.29; 95% CI, 1.11–1.50; P =0.0007). The proportion of deaths caused by SCD was not different between HF quartiles (P =0.91), and the effect of implantable cardioverter-defibrillator implantation on all-cause mortality was not modified by the duration of HF (P =0.59). Conclusions: Duration of HF predicted both all-cause mortality and risk of SCD independently of other risk indicators. However, the proportion of death caused by SCD did not change with longer duration of HF, and the effect of implantable cardioverter-defibrillator was not modified by the duration of HF. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT00542945. [ABSTRACT FROM AUTHOR]

Aims: Current guidelines recommend implantable cardioverter‐defibrillator (ICD) therapy in patients with heart failure, a left ventricular ejection fraction of ≤35%, and New York Heart Association (NYHA) class II–III. However, the evidence regarding the benefit of primary prevention ICD is less consistent in patients with NYHA class III. We investigated the long‐term effects of primary prevention ICD implantation according to NYHA class in an extended follow‐up study of the DANISH trial. Methods and results: The DANISH trial randomized 1116 patients with non‐ischaemic heart failure with reduced ejection fraction (HFrEF) to ICD implantation or usual care. Outcomes were analysed according to NYHA class at baseline (NYHA class II and III/IV). The primary outcome was all‐cause mortality. Of the 1116 patients randomized in the DANISH trial, 597 (53.5%) were in NYHA class II at baseline, 505 (45.3%) in NYHA class III, and 14 (1.3%) in NYHA class IV. During a median follow‐up of 9.5 years, NYHA class III/IV, compared with NYHA class II, were associated with a greater long‐term rate of all‐cause mortality (hazard ratio [HR] 1.52, 95% confidence interval [CI] 1.20–1.93) and cardiovascular death (HR 1.95 [1.47–2.60]). ICD implantation, compared with usual care, did not reduce the long‐term rate of all‐cause mortality (all participants: HR 0.89 [95% CI 0.74–1.08]; NYHA class II: HR 0.85 [0.64–1.13]; NYHA class III/IV: HR 0.89 [0.69–1.14]; pinteraction = 0.78) or cardiovascular death (all participants: HR 0.87 [95% CI 0.70–1.09]; NYHA class II: HR 0.78 [0.54–1.12]; NYHA class III/IV: HR 0.89 [0.67–1.19]; pinteraction = 0.58), irrespective of NYHA class. Similarly, NYHA class did not modify the beneficial effects of ICD implantation on sudden cardiovascular death (all participants: HR 0.60 [95% CI 0.40–0.92]; NYHA class II: HR 0.73 [0.40–1.36]; NYHA class III/IV: HR 0.52 [0.29–0.94]; pinteraction = 0.39). Conclusions: In patients with non‐ischaemic HFrEF, ICD implantation, compared with usual care, did not reduce the overall mortality rate, but it did reduce sudden cardiovascular death, regardless of baseline NYHA class. Clinical Trial Registration: ClinicalTrials.gov NCT00542945. [ABSTRACT FROM AUTHOR]