Long-Term Durability of Stylet-Driven Leads for Left Bundle Branch Area Pacing.

Background Left bundle branch area pacing (LBBAP) has emerged as a promising approach to cardiac physiologic pacing. However, the mechanical stress and fracture risk has not been studied for stylet-driven leads implanted in the left bundle branch area (LBBA). Purpose The main purpose of this study was to evaluate the change in curvature during a cardiac cycle when a stylet-driven lead with a rigid distal end was implanted in LBBA and to identify any increased risk of conductor fracture for the LBBAP lead compared to those implanted at the His bundle (HB), traditional right atrium (RA) and right ventricle (RV) locations. Methods A high-resolution, four-dimensional human beating heart model was utilized for simulating the stress on the lead. The bending stiffness of lead body segments was measured with 3-pts bending test and the values were assigned to the finite element model. The curvature change of lead body during one cardiac cycle was measured. The safety factor of lead conductors was calculated using the curvature measurements, the conductor’s endurance limit, and the ultimate stress of the material (MP35N). A higher safety factor indicates better lead durability and lower risk of fracture. A parametric study was also performed to investigate how additional implant factors impact the safety factor of LBBAP leads: lead insertion angle, implant depth, degree of slack, and implant location (Figure 1). Results A total of 8 implant scenarios for LBBAP were defined and tested using the combination of the implant factors described above. Two RV implanted locations were tested: RV apex and RV apical septum. One HBP and one RA implant location were tested. The region with maximum change in curvature for LBBAP lead was at 0-10 mm proximal to the ring electrode (Figure 2A). The maximum change in curvature on the lead body for LBBAP, HBP, RV, and RA implants were: 0.022±0.005 (n=8), 0.033 (n=1), 0.036±0.002 (n=2), and 0.024 mm-1 (n=1), respectively (Figure 2B). The safety factor for the lead conductors for LBBAP, HBP, RV, and RA implants were 5.57±1.35 (n=8), 3.48 (n=1), 4.62±0.04 (n=2), and 4.65 (n=1), respectively (Figure 2C). The highest safety factor among all implant locations was 7.63, corresponding to a LBBAP implant scenario with mid-septum location, a 45 degree lead insertion angle towards apex, 7.5 mm lead depth in the septum, and low lead slack. HBP had the lowest safety factor among all implant locations. Conclusion The stylet-driven lead with a rigid distal end implanted at the left bundle branch area does not introduce any further risk of fracture compared to the HBP or traditional RA/RV implant locations in this computational modeling study.Fig 1: LBBAP implants testedFig 2: Lead curvature and safety factor

Heart failure with reduced ejection fraction (HFrEF) complicated by malignant ventricular arrhythmias remains a major therapeutic challenge, particularly in patients following complex mitral valve surgery. Conventional right ventricular pacing may aggravate ventricular dyssynchrony and further impair systolic function. Conduction system pacing (CSP) has emerged as a physiologic pacing strategy that directly activates the native His-Purkinje system, most commonly through His bundle pacing or left bundle branch area pacing (LBBAP), allowing near-normal ventricular activation.We report the case of a 70-year-old patient who developed severe heart failure, postoperative bradyarrhythmia, and an extremely high burden of ventricular arrhythmias following urgent mitral valve replacement. Despite pharmacological therapy and unsuccessful catheter ablation, electrical instability persisted. An implantable cardioverter-defibrillator (ICD) incorporating CSP using LBBAP was successfully implanted. Baseline QRS duration prior to pacing was 183 ms, whereas paced QRS duration after LBBAP implantation was 165 ms, consistent with near-physiologic ventricular activation. ECG documentation before and after device implantation demonstrated marked QRS narrowing and substantial suppression of ventricular ectopy after CSP-ICD implantation. Early post-implant monitoring demonstrated a marked reduction in ventricular ectopy and effective physiologic pacing. During 24 months of follow-up, pacing parameters remained stable, and no ventricular arrhythmias requiring ICD therapy were observed. This case demonstrates the feasibility of combining CSP with ICD therapy in selected patients early after mitral valve surgery. These findings are hypothesis-generating and require confirmation in prospective studies and larger clinical registries to define the broader clinical role and long-term durability of this strategy.

Background A leadless pacemaker (L-PM) has been designed to avoid the need for a pacemaker pocket and transvenous lead. Long-term safety will largely depend on the need for replacements, mainly due to battery depletion (end-of-life). While the mean L-PM battery longevity predicted by the manufacturer is 12 years, real-world longevity data are still scarce. We aimed to describe L-PM parameters’ stability and battery longevity during the mid-term follow-up. Methods Single-center registry of consecutive patients undergoing L-PM implantation from May 2015 to November 2023. Procedural characteristics, lead parameters and battery longevity were collected immediately after implantation and during the most recent follow-up visit. Results Overall, 261 consecutive patients had a transcatheter L-PM implanted through a femoral vein (mean age 78±10 years; 66% male). Mean procedural duration was 44±28min and fluoroscopy time was 4,4±3,9min. The device was successfully implanted in all but one patient. The main indications for permanent pacing were high-degree atrioventricular block [N=130 (50%)], atrial fibrillation with pauses [N=78 (30%)], and sinus node disease [N=28 (11%)]. Immediately after implantation, three cases (1,2%) of pericardial effusion (one with tamponade) were reported. In one case (0,4%), a conventional pacemaker was implanted due to L-PM acute dysfunction. No other procedure-related complications, including dislodgment, were reported at discharge. After a mean follow-up of 2,8±1,7years, the pacing threshold and R-wave amplitude remained stable [0,67mV vs. 0,62mV (p=0,9); and 10,3mV vs. 16,1mV (p<0,001), respectively] and mean ventricular pacing was 54±38%. Expected battery longevity was >8 years (maximum value) in 84% of the patients. In the subgroup of patients with >5 years of follow-up (N=20; mean follow up of 6,3±1,8years), the expected battery longevity was >8 years in 85% (N=17) of the patients. In three cases, the L-PM was upgraded to cardiac resynchronization therapy or left bundle branch area pacing due to pacing-induced left ventricular dysfunction. There was one case of L-PM end-of-life 6 years after implant (pacing threshold 0,5mV; ventricular pacing 100%), in which a second L-PM was successfully implanted. Overall, 78 (31%) patients died, a mean of 2,2±1,9 years after L-PM implantation, none related to the device. Conclusion In this real-world cohort, L-PM maintained stable pacing parameters and, in the mid-term follow-up, only one battery depletion was observed while expected longevity remained above 8 years in the large majority of patients. Longer follow up will allow better understanding of both technical and clinical aspects relevant to manage end-of-life devices.Table 1Figure 1

IntroductionLeft bundle branch area pacing (LBBaP) is a relatively new approach for physiologic pacing. A limited number of retrospective clinical studies, featuring small sample sizes, have shown that compared with...

Funding AcknowledgementsType of funding sources: Public grant(s) – National budget only. Main funding source(s): The Dutch Research Council (NWO)BackgroundLeft bundle branch area pacing (LBBAP) has been introduced as an alternative, more physiological pacing strategy to biventricular pacing (BiVP). LBBAP can result in selective LBB pacing (sLBBP), non-selective LBB pacing (nsLBBP), or LV septal pacing (LVSP). Direct comparison between the different pacing strategies is challenging due to the practical implications of performing multiple pacing procedures within the same patients, as well as the large heterogeneity of underlying disease in patients. Computational models can be used to perform controlled in silico experiments and to compare all possible pacing modalities under the same conditions.AimTo investigate the effects of LBBAP strategies versus BiVP on cardiac mechanics and hemodynamics in a set of well-defined virtual heart failure patients.MethodsAn electrophysiological model was used to calculate biventricular electrical activation maps during LBBB and the different pacing strategies. The resulting regional activation times were imposed to the well-validated CircAdapt model of the human four-chamber heart and circulation. A set of virtual patients at different stages of heart failure are then defined within the CircAdapt framework, which is achieved by decreasing the contractility of the LV myocardium, such that LVEF≤35%. The CircAdapt model is then used to compute regional ventricular strain patterns and myocardial work as well as global ventricular pump function during LBBB, BiVP and the different LBBAP modalities.ResultsSelective LBBP is best at restoring mechanical homogeneity in LV contraction as evidenced by simulated wall strains waveforms (Fig 1, Left). NsLBBP increases septal dyssynchrony and introduces small pre-stretch in the LVfw (1.3±0.3%). This effect is more pronounced in LVSP (2.4±1.4%). In BiVP, pre-stretch occurs only in a single LV free wall (LVfw) segment, but all septal segments display a distinct oscillatory pattern. Work load homogeneity (Fig 1, Center) was best restored in sLBBP (4.9±1.1 kPa). NsLBBP lead to reduced homogeneity (4.9±1.8 kPa). LVSP reduced this further (4.8±2.6kPa), while BiVP performed similarly (4.6±2.6kPa) to LVSP. All modalities vastly improved on the baseline LBBB (4.06±5.6 kPa). Hemodynamically (Fig 1, Right), sLBBP showed greatest improvement in LV function (LVESV:-8.1%; LVEF:+6.8%; MLAP:-16.4%; LVdp/dtmax:+12.8%), followed by nsLBBP (LVESV:-7.2%; LVEF:+6.0%; MLAP:-14.5%; LVdp/dtmax:+12.5%), LVSP (LVESV:-5.6%; LVEF:+4.6%; MLAP:-11.7%; LVdp/dtmax:+12.358%) and finally BiVP (LVESV: -4.6%; LVEF:+3.8%; MLAP:-9.3%; LVdp/dtmax:+9.8%)ConclusionWe were able to simulate LBBB and subsequent pacing strategies in virtual heart failure patients. This approach allowed direct comparison of mechanical and hemodynamic effects of BiVP and LBBAP modalities without confounding variables. Our results indicate that all LBBAP modalities perform at least similar to bi-ventricular pacing regardless of mechanical viability.

This paper was prepared for the Deep Drilling Symposium of the Society of petroleum Engineers of AIME, to be held in Amarillo, Tex., Sept. 11–12, 1972. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Many major oil companies, gas companies, funded companies, independents and contractors are involved in the drilling of deep wells in the Anadarko basin. The casing designs figured by these companies can vary considerably even on nearly identical wells. The purpose of the first part of this paper is to report variances in how part of this paper is to report variances in how these designs are calculated. The second part of this paper will review casing programs with emphasis on the compatibility of the key. industry drilling bits and casing. The 11-3/4-in. intermediate string program will be discussed. CASING DESIGNS There is a general understanding in our industry that, if someone uses the term standard with regard to casing design safety factors, he means using 1.125 for collapse, 1.800 for tension and 1.000 for burst. A standard casing design would be one considering a pressure gradient of 0.5 psi/ft and applying the above safety factors to the three design conditions. Most casing designs are handled in this manner, particularly those for shallow wells. There are particularly those for shallow wells. There are companies that deviate from the standard. Some design higher and some lower. Each of the three design conditions will be reviewed to show the variances in how companies are designing in the Anadarko basin. Collapse As previously mentioned, the standard safety factor used in collapse is 1.125. This safety factor is the minimum ratio of the tube collapse resistance over the collapse pressures. The collapse pressure on the outside of the casing is usually figured by calculating the hydrostatic pressure of the fluid the casing is set in. The inside is considered void. All companies correct for the tension effect on the collapse resistance of a tube. Some companies deviate from the standard safety factor by lowering it to 1.050 or 1.000. A few companies take credit for cement behind the pipe and use a lower safety factor below the top of cement than that above. In this regard the lowest safety factors seen are 0.850 below the top of cement and 1.000 above the top of cement. Another unique method one company uses is to apply a safety factor of 1.000 to the bottom section of casing and then switch to 1.125 at the first section change. This design method is supported by the theory that, when casing is set and cemented, the bottom portion of the string is in compression rather than tension because of the buoyant effect and slacking-off procedures. A tube in longitudinal compression procedures. A tube in longitudinal compression will have a higher collapse resistance than a tube under no load.

<div class="htmlview paragraph">The objective of this paper is to describe the reliability of a system component as a function of both a) the safety factor used in the design and b) the quality factor associated with the production of the component. Under the normal operating conditions the component is subjected to some environmental stress and to withstand this stress the component is designed with a safety factor ν. In practice the design of the component is broken down into individual dimensions and the production specifications are derived for these dimensions. The strength of the components (when produced) would consequently be function of the quality of production. Thus it is possible to describe the reliability as a function of both the safety factor ν and quality of production q. This function is computed, for specific assumptions, and the graphs are included in the paper.</div> <div class="htmlview paragraph">The principal advantage of this analysis would be the recognition of a possible trade-off within the resources allocated to better production and those assigned to higher safety factors. The same reliability would be achieveable either through a very high safety factor with poor production quality or through a lower safety factor with better production quality. The optimal resource allocation could be obtained through the solution of a mathematical programming problem.</div> <div class="htmlview paragraph"> <div id="FD1" class="formula"> <div class="graphic-wrapper"><img class="article-image equation block" src="700655_fig0001.jpg" alt="No Caption Available"/></div> </div> </div>

We studied excitation thresholds and arrhythmias produced in cultured chick embryo myocardial cells subjected to electric shocks using rectangular, untruncated resistor-capacitor (RC), and critically damped resistor-inductor-capacitor (RLC) waveforms with variable intensities while photocell mechanograms were recorded. Strength-duration curves for excitation and production of a specific postshock arrhythmia (4-s arrest) were constructed. Excitation curves closely resembled those for in situ defibrillation threshold (or specific % success). The ratio between the shock intensity producing a 4-s arrest and that producing excitation at each duration (termed the "safety factor") was determined. Waveforms with a large safety factor in vitro defibrillated most effectively in situ with little postshock dysfunction. Waveforms with low safety factors had a low rate of success in situ and produced much postshock dysfunction. Safety factor of monophasic clinical waveforms were lower than that of the 5-ms rectangular wave. The close correspondence between in vitro safety factor and in situ defibrillating effectiveness, as reported in the literature, suggests that the cell culture system is an effective screening system for determining waveforms that will improve the efficacy and safety of defibrillation procedures.

This study investigates the mechanical performance of two prosthetic forelimb designs for dogs—one with a solid structure and the other with a perforated structure—using Finite Element Analysis (FEA). Both models were analyzed under static loading conditions representing approximately 60% of a dog’s body weight, the typical load borne by the forelimbs. The prosthetics were modeled with ABS plastic, a widely used 3D printing material, and evaluated for Von Mises stress, total deformation, elastic strain, and factor of safety. The analysis showed that both models remained within the elastic limit of the material, indicating that no permanent deformation would occur under the applied loads. The Solid Model demonstrated a significantly higher factor of safety (14) and lower deformation, confirming its structural strength but also highlighting excessive rigidity, increased material use, and higher cost. In contrast, the Perforated Model exhibited slightly higher localized stresses and a lower factor of safety (3.01), yet it still met essential safety requirements while providing greater compliance, flexibility, and material efficiency. These attributes are desirable for comfort, adaptability, and practicality in veterinary applications. Although its long-term durability requires further evaluation, the Perforated Model strikes a more effective balance between safety, comfort, and sustainability. Based on these findings, the perforated design is considered the more suitable option for canine prosthetic development. Future work will extend the analysis to dynamic loading scenarios, such as walking and running, to better simulate real-world performance.

Fracture resistance, 3-dimensional finite element analysis, and safety factors for five post-and-core restorations with crowns placed in the noncircular-shaped canals of premolars

A mathematical model developed for a personal computer was used to simulate the jitter phenomenon in neuromuscular transmission in order to characterize the relationship between jitter and the safety factor. Four models of normal and abnormal neuromuscular transmission were investigated. In a human experiment, the mean consecutive difference (MCD) values for stimulated single-fiber electromyography at firing rates of 1, 2, 5, and 10 Hz were measured in 137 motor end-plates of myasthenic patients. Results of the computer simulations show that the relationship between jitter and the safety factor is exponential like. Variations in jitter are most prominent in end-plates with low safety factors. This relationship agrees with results of human end-plate studies. Changes in the MCD values caused by presynaptic depression or facilitation are linearly correlated to the initial jitter, whereas the logarithmic values of MCD are not. It is very important to keep in mind this nonlinear relationship when relating single-fiber jitter to the safety factor.

Jack-ups have been used extensively in the North Sea as mobile structures and have had a good safety record. This good record has given several operators confidence to consider using jack-ups for the more demanding roles of production for extended periods at deep water locations. This paper examines the margins of safety provided by current regulations for independent leg jack-ups, and argues that larger margins of safety are needed for the more demanding roles of production in deep water. Safety margins against collapse are examined with dynamic time-domain analyses of the nonlinear interaction of structure and seabed under escalating storm loading. These analyses extend the work of Hambly, Imm and Stahl1. Analyses on a future generation of jack-ups for 120m water depth in the North Sea highlight the fundamental importance of spudcan embedment and horizontal resistance of seabed to sliding of spudcans. SAFETY FACTORS Current regu1ations 2–6 and assessment criteria7,8 provide protection to jack-ups against collapse by specifying minimum Safety Factors against particular design loading conditions. The regulations have to cater for a wide variety of units and conditions, and for this reason the definitions are kept relatively simple and have to be interpreted in a robust manner. The Safety Factor against overturning, for example, provides a degree of protection against collapse from a variety of mechanisms including foundation failure and leg breakage. One would not expect a jack-up to collapse by overturning bodily because it is not a rigid body. The UK Department of Energy Guidance Notes2 (DEn) indicate that structures should be assessed for environmental loads which "shall not be less than those likely to be exceeded on average once only in any period of 50 years" (referred to here as the 50-year load). DEn2 and others3,7 currently permit Safety Factors against overturning to be as low as 1.1. If a jack-up really does have such a low Safety Factor under 50-year loading it is likely to have a Safety Factor of less than 1.0, i.e. be unsafe, under 100-year loading. This can be shown by reference to Table 1 which shows in columns 1 and 2 the increase of wave height in the North Sea with return period as indicated by DEn2. Column 3 shows the increase in wave overturning load on a jack-up leg associated with the increase in wave height in column 2. In particular the overturning load from a 100-year wave is more than 1.1-times the overturning load from a 50-year wave. Dynamic calculations described later for a whole jack-up, as opposed to static calculations for a single leg, also show that the total overturning moment from 100-year loading is more than 1.1-times the total overturning moment from 50-year loading. The safety record for jack-ups in the North Sea has been good9 even though stability assessments have included minimum Safety Factors close to unity. This is because it has been extremely rare for units to be subjected to loading approaching the maximum design loading while standing in deep water.

Heliostat drive unit design considerations – Site wind load effects on projected fatigue life and safety factor

A slope stability model is derived for an infinite slope subjected to unsaturated infiltration flow above a phreatic surface. Closed form steady state solutions are derived for the matric suction and degree of saturation profiles. Soil unit weight, consistent with the degree of saturation profile, is also directly calculated and introduced into the analyzes, resulting in closed-form solutions for typical soil parameters and an infinite series solution for arbitrary soil parameters. The solutions are coupled with the infinite slope stability equations to establish a fully realized safety factor function. In general, consideration of soil suction results in higher factor of safety. The increase in shear strength due to the inclusion of soil suction is analogous to making an addition to the cohesion, which, of course, increases the factor of safety against sliding. However, for cohesive soils, the results show lower safety factors for slip surfaces approaching the phreatic surface compared to those produced by common safety factor calculations. The lower factor of safety is due to the increased soil unit weight considered in the matric suction model but not usually accounted for in practice wherein the soil is treated as dry above the phreatic surface. The developed model is verified with a published case study, correctly predicting stability under dry conditions and correctly predicting failure for a particular storm.

We examined the allometry and mechanical properties of the peduncles of Hieracium pilosella and other species in the Asteraceae (H. aurantiacum, Taraxicum officinale, Tragopogon pratensi) to evaluate the hypothesis that tapered, tubular, and non-septate peduncles optimize the trade-offs among stem biomass allocation, elevating flowers and thus their wind-dispersed fruits, and the requirement for a factor of safety against mechanical failure. This hypothesis was evaluated by comparing peduncle morphometry (e.g., biomass M(s), floral biomass M(f), and length L) and mechanical properties (e.g., bending rigidity EI) for populations growing in windy and wind-sheltered sites as well as transplants between sites. Regardless of ambient wind speeds, M(s) ∝ L(4/3) and EI ∝ L(11/4) ∝ M(s)(5/3), whereas M(f) /M(s) ∝ L(-1.15), i.e., peduncles disproportionately increase in their biomass as they increase in length, but mechanically support a disproportionately smaller floral biomass relative to their biomass. Calculations show that the tall peduncles from wind-sheltered sites have a larger fruit dispersal range and a lower factor of safety than the shorter peduncles produced in open sites. These and other observations are interpreted to indicate that tubular peduncles enhance relative fitness in terms of propagule dispersal (but not propagule number per stem) while maintaining a sufficient factor of safety against mechanical failure.