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INTRODUCTION: We aimed to describe baseline amyloid‐beta (Aβ) and tau‐positron emission tomograrphy (PET) from Longitudinal Early‐onset Alzheimer's Disease Study (LEADS), a prospective multi‐site observational study of sporadic early‐onset Alzheimer's disease (EOAD). METHODS: We analyzed baseline [18F]Florbetaben (Aβ) and [18F]Flortaucipir (tau)‐PET from cognitively impaired participants with a clinical diagnosis of mild cognitive impairment (MCI) or AD dementia aged < 65 years. Florbetaben scans were used to distinguish cognitively impaired participants with EOAD (Aβ+) from EOnonAD (Aβ−) based on the combination of visual read by expert reader and image quantification. RESULTS: 243/321 (75.7%) of participants were assigned to the EOAD group based on amyloid‐PET; 231 (95.1%) of them were tau‐PET positive (A+T+). Tau‐PET signal was elevated across cortical regions with a parietal‐predominant pattern, and higher burden was observed in younger and female EOAD participants. DISCUSSION: LEADS data emphasizes the importance of biomarkers to enhance diagnostic accuracy in EOAD. The advanced tau‐PET binding at baseline might have implications for therapeutic strategies in patients with EOAD. HIGHLIGHTS: 72% of patients with clinical EOAD were positive on both amyloid‐ and tau‐PET.Amyloid‐positive patients with EOAD had high tau‐PET signal across cortical regions.In EOAD, tau‐PET mediated the relationship between amyloid‐PET and MMSE.Among EOAD patients, younger onset and female sex were associated with higher tau‐PET. [ABSTRACT FROM AUTHOR]

In winter 2013, a sea ice breakout in the Beaufort Sea produced extensive fracturing and contributed to record ice export. Rheinlænder et al. (2022, https://doi.org/10.1029/2022GL099024) simulated this event using the neXtSIM sea ice model, reproducing a realistic progression of lead opening and ice drift following the track of an anticyclone. Their simulations indicate strong winds and thin ice are key factors in breakouts. We discuss observational records giving additional insight into the mechanisms controlling breakout events, including the role of wind direction. Breakouts are common and have occurred under weaker winds than in 2013 and in thicker ice of previous decades. During 2013 and other events, patterns of lead opening during breakout followed changes in wind direction relative to the coast with anticyclone position. For skillful predictions of future breakouts, models must reproduce this behavior, and their performance should be assessed across a range of wind and ice conditions. Plain Language Summary: In winter, the Beaufort Sea is covered by a layer of sea ice that is usually frozen against the southern and eastern coastlines that bound the sea. When winds continuously blow from east to west away from these boundaries, the ice cover can tear apart and rapidly drift away from the coasts in what is called a breakout event. The prediction of such dynamic events is important for those who navigate the region. Rheinlænder et al. (2022, https://doi.org/10.1029/2022GL099024) recently used the neXtSIM sea ice model to simulate realistic ice cracking and drift during an exceptionally strong breakout that occurred in 2013. The authors highlighted strong winds and thin sea ice as key factors for breakout. We use observational records to provide additional insight into processes during Beaufort breakouts. Records of many similar events demonstrate that breakouts are common under weather patterns that produce east‐to‐west winds, even for weaker winds and thicker ice than in 2013. Across observed events, wind direction influences sea ice fracturing patterns and breakout timing. To ensure that model predictions of future sea ice breakouts are accurate, simulations should be compared against observations of multiple recorded events that span a range of wind and ice conditions. Key Points: Observational data provide context for a 2013 Beaufort Sea (BS) breakout simulated with the neXtSIM model by Rheinlænder et al. (2022, https://doi.org/10.1029/2022GL099024)While the 2013 event was exceptional, winter sea ice breakout is common under anticyclonic winds including in years with thicker ice packsWind direction relative to the coast influences the timing and location of lead opening during breakout in the BS [ABSTRACT FROM AUTHOR]

Patients with early‐onset Alzheimer's disease (EOAD) are commonly excluded from large‐scale observational and therapeutic studies due to their young age, atypical presentation, or absence of pathogenic mutations. The goals of the Longitudinal EOAD Study (LEADS) are to (1) define the clinical, imaging, and fluid biomarker characteristics of EOAD; (2) develop sensitive cognitive and biomarker measures for future clinical and research use; and (3) establish a trial‐ready network. LEADS will follow 400 amyloid beta (Aβ)‐positive EOAD, 200 Aβ‐negative EOnonAD that meet National Institute on Aging–Alzheimer's Association (NIA‐AA) criteria for mild cognitive impairment (MCI) or AD dementia, and 100 age‐matched controls. Participants will undergo clinical and cognitive assessments, magnetic resonance imaging (MRI), [18F]Florbetaben and [18F]Flortaucipir positron emission tomography (PET), lumbar puncture, and blood draw for DNA, RNA, plasma, serum and peripheral blood mononuclear cells, and post‐mortem assessment. To develop more effective AD treatments, scientists need to understand the genetic, biological, and clinical processes involved in EOAD. LEADS will develop a public resource that will enable future planning and implementation of EOAD clinical trials. [ABSTRACT FROM AUTHOR]

Abstract: Sea ice kilometer‐scale characteristics are not explicitly represented in weather and climate model systems. However, due to the large differences of the surface temperature between sea ice and ocean, sea ice‐free areas (leads, polynyas, etc.) can have a strong impact on the surface heat fluxes and, in turn, on atmospheric dynamics. In the present study we analyze the atmospheric response to changes in the sea ice characteristics in the marginal ice zone of the Fram Strait and Barents Sea. A kilometer‐scale convection permitting atmospheric modeling system is used. The model sensitivity experiment is idealized, since there is no complete information on sea ice on these scales available. Instead, we are merging information from the passive microwave satellite product of sea ice concentration with a sea ice lead product based on thermal infrared sensors. An important constraint is that the sea ice‐free areas are introduced locally, but on scales of 100 km the sea ice coverage is kept constant for both the experiments. The sensitivity of air‐sea fluxes, atmospheric temperature, and winds is analyzed between the model experiments. In general, the standard deviation of the changes in surface air temperature and winds is, on large scales, about 2 K and 2 m/s, respectively. Those values are in the same order as the mean 12‐hr forecast error of advanced weather forecast models in this region. [ABSTRACT FROM AUTHOR]

Abstract: Spring phytoplankton growth in polar marine ecosystems is limited by light availability beneath ice‐covered waters, particularly early in the season prior to snowmelt and melt pond formation. Leads of open water increase light transmission to the ice‐covered ocean and are sites of air‐sea exchange. We explore the role of leads in controlling phytoplankton bloom dynamics within the sea ice zone of the Arctic Ocean. Data are presented from spring measurements in the Chukchi Sea during the Study of Under‐ice Blooms In the Chukchi Ecosystem (SUBICE) program in May and June 2014. We observed that fully consolidated sea ice supported modest under‐ice blooms, while waters beneath sea ice with leads had significantly lower phytoplankton biomass, despite high nutrient availability. Through an analysis of hydrographic and biological properties, we attribute this counterintuitive finding to springtime convective mixing in refreezing leads of open water. Our results demonstrate that waters beneath loosely consolidated sea ice (84–95% ice concentration) had weak stratification and were frequently mixed below the critical depth (the depth at which depth‐integrated production balances depth‐integrated respiration). These findings are supported by theoretical model calculations of under‐ice light, primary production, and critical depth at varied lead fractions. The model demonstrates that under‐ice blooms can form even beneath snow‐covered sea ice in the absence of mixing but not in more deeply mixed waters beneath sea ice with refreezing leads. Future estimates of primary production should account for these phytoplankton dynamics in ice‐covered waters. [ABSTRACT FROM AUTHOR]

We performed measurements of carbon dioxide fugacity ( fCO2) in the surface water under Arctic sea ice from January to June 2015 during the Norwegian young sea ICE (N-ICE2015) expedition. Over this period, the ship drifted with four different ice floes and covered the deep Nansen Basin, the slopes north of Svalbard, and the Yermak Plateau. This unique winter-to-spring data set includes the first winter-time under-ice water fCO2 observations in this region. The observed under-ice fCO2 ranged between 315 µatm in winter and 153 µatm in spring, hence was undersaturated relative to the atmospheric fCO2. Although the sea ice partly prevented direct CO2 exchange between ocean and atmosphere, frequently occurring leads and breakup of the ice sheet promoted sea-air CO2 fluxes. The CO2 sink varied between 0.3 and 86 mmol C m−2 d−1, depending strongly on the open-water fractions (OW) and storm events. The maximum sea-air CO2 fluxes occurred during storm events in February and June. In winter, the main drivers of the change in under-ice water fCO2 were dissolution of CaCO3 (ikaite) and vertical mixing. In June, in addition to these processes, primary production and sea-air CO2 fluxes were important. The cumulative loss due to CaCO3 dissolution of 0.7 mol C m−2 in the upper 10 m played a major role in sustaining the undersaturation of fCO2 during the entire study. The relative effects of the total fCO2 change due to CaCO3 dissolution was 38%, primary production 26%, vertical mixing 16%, sea-air CO2 fluxes 16%, and temperature and salinity insignificant. [ABSTRACT FROM AUTHOR]

Background Echocardiographically detected patent foramen ovale (PFO) has been associated with stroke/transient ischemic attack (TIA) in patients with cardiac implantable electronic devices (CIEDs). We sought to evaluate the relationship between echocardiographic characteristics and risk of stroke/TIA and mortality in CIED patients with PFO. Methods In 6,086 device patients, PFO was detected in 319 patients. A baseline echocardiogram was present in 250 patients, with 186 having a follow-up echocardiogram. Results Of 250 patients with a baseline echocardiogram, 9.6% (n = 24) had a stroke/TIA during mean follow-up of 5.3 ± 3.1 years; and 42% (n = 105) died over 7.1 ± 3.7 years. Atrial septal aneurysm, prominent Eustachian valve, visible shunting across PFO, baseline or change in estimated right ventricular systolic pressure (RVSP)/tricuspid regurgitation (TR), or maximum RVSP were not associated with postimplant stroke/TIA (P > 0.05). An exploratory multivariate analysis using time-dependent Cox models showed increased hazard of death in patients with increase in TR ≥2 grades (hazard ratio [HR] 1.780, 95% confidence interval [CI] 1.447-2.189, P < 0.0001), or increase in RVSP by >10 mm Hg (HR 2.018, 95% CI 1.593-2.556, P < 0.0001), or maximum RVSP in follow-up (HR 1.432, 95% CI 1.351-1.516, P < 0.0001). A significant increase (P < 0.001) in TR was also noted during follow-up. Conclusions In patients with CIED and PFO, structural and hemodynamic echocardiographic markers did not predict future stroke/TIA. However, a significantly higher TR or RVSP was associated with higher mortality. [ABSTRACT FROM AUTHOR]

Ultrasound-Guided Lead Placement. Introduction: Ultrasound guidance is widely recommended to reduce the risk of complications during central venous catheter placement. However, ultrasound guidance is not commonly utilized for implanting leads for cardiac rhythm management devices. Methods and Results: We describe our technique of ultrasound-guided pacemaker implantation, including a novel pull-through technique that allows percutaneous guidewire insertion prior to the first incision. We review the literature and recent advances in ultrasound imaging technology that may facilitate the adoption of ultrasound guidance. Conclusions: Ultrasound guidance provides a safe and rapid technique for extrathoracic subclavian or axillary venous lead placement. (J Cardiovasc Electrophysiol, Vol. 24, pp. 370-374, March 2013) [ABSTRACT FROM AUTHOR]

Implanted cardiac devices, including pacemakers, defibrillators, and resynchronization devices, are known to develop thrombus on their intravascular leads. Patent foramen ovale (PFO) occurs in approximately one-quarter of the adult population. It is unclear whether paradoxical cardioembolism and clinically relevant stroke occur in patients with implanted cardiac leads and PFO. We present a case series of four patients with cardioembolic stroke, presumed to arise from intravascular cardiac leads and associated PFO that required device closure of the PFO. (PACE 2013; 36:50-54) [ABSTRACT FROM AUTHOR]

Impact of Recalls on ICD Utilization. Introduction: The study was designed to evaluate the feasibility and performance of right ventricular (RV) mid-septal versus apical implantable defibrillator (ICD) lead placement. Methods and Results: SEPTAL is a randomized, noninferiority trial, which randomly assigned patients to implantation of ICD leads in the RV mid-septum versus apex, with a primary objective of comparing the implant success rate of implant at each site, based on strict electrical predefined criteria. We also compared the (1) pacing lead characteristics, (2) rates of appropriate and inappropriate ICD therapies, and (3) all-cause mortality between the 2 sites at 1 year. The trial enrolled 215 patients (mean age = 59.7 ± 12.4 years, mean LVEF = 34.0 ± 14.2%, 84.2% men), of whom 148 (68.8%) presented with ischemic heart disease. The ICD indication was primary prevention in 117 patients (54.4%). The lead was successfully implanted in 96/107 patients (89.7%) assigned to the RV mid-septum, and in 99/108 (91.7%) assigned to the apex (ns). The 1-year rate of lead-related adverse events was similar in both groups. A total of 8 first inappropriate ICD therapies (7.9%) were delivered in the RV mid-septal group, versus 8 (7.8%) in the apical group (ns), while first appropriate therapies were delivered to 22 (21.4%) and 24 patients (23.8%), respectively (ns). All-cause mortality was 7.9% in the RV mid-septal versus 2.9% in the RV apical group (ns). Conclusion: This study confirmed the technical feasibility and noninferior performance of ICD leads implanted in the RV mid-septum versus the apex. (J Cardiovasc Electrophysiol, Vol. 23, pp. 853-860, August 2012) [ABSTRACT FROM AUTHOR]

Background: There has been concern over declining bipolar (BP) impedance (Z) in aging polyurethane (PU) cardiac pacing leads. Subsequently, a prospective study was conducted comparing BP Z, threshold (Th), and R-wave sensing amplitude of 55D PU-insulated (Model 4024, Medtronic, Inc., Minneapolis, MN, USA) and silicone-insulated (Model 5024) leads. Methods: This study was initiated by The Iowa Heart Center. Patients with Model 4024 (N = 162) or 5024 (N = 120) pacing leads with at least 6 years implant time were enrolled and followed for an additional 5 years. Results: There was a significant drop in the mean BP Z for the Model 4024 population, between enrollment (6 years) and the final endpoint (11 years), which was in contrast to the Model 5024 which did not see a significant drop in its mean BP Z for this same period. The trend difference seen in the means between the two models was statistically significant (P < 0.0001). In addition, a statistically significant relationship was found between dropping BP Z and rising Th (P < 0.0001). The analysis showed that if BP Z dropped below 200 ohms, the probability of having a >3X increase over baseline, in Th at 2.5 V, increases from approximately 3-7% to as high as 30%. Conclusions: A significant drop in BP Z observed in the PU-insulated Model 4024 lead was not present in the silicone-insulated Model 5024 lead. The statistically significant relationship between dropping BP Z and rising Th helps to understand how to better manage patients with aging leads. (PACE 2012; 35:51-57) [ABSTRACT FROM AUTHOR]

The biocompatibility of all metallic, polymeric, or ceramic materials used for functional electrical stimulation is governed by the inevitable inflammatory tissue response, but possibly also by immunological reactions to the bulk material or released constituents. Besides chemical, physical, and corrosion properties of the conductive electrode materials, increased surface area and roughness of the electrode can influence tissue contact and signal delivery, and can also affect electrode-tissue impedance due to increased connective tissue encapsulation. The polymeric materials used for electrode insulation and those for leads and stimulator packaging seem more or less compatible in an aggressive biological environment. For the long-term performance of electrodes and leads, the relative motion in the various implant bed situations also has to be considered. [ABSTRACT FROM AUTHOR]

In addition to knowledge of normal and pathological patterns, the correct interpretation of electrocardiographic (ECG) recordings requires the use of acquisition procedures according to approved standards. Most manuals on standard electrocardiography devote little attention to inadequate ECG recordings. In this article, we present the most frequent ECG patterns resulting from errors in limb and precordial lead placement, artifacts in 12-lead ECG as well as inadequate filter application; we also review alternative systems to the standard ECG, which may help minimize errors. [ABSTRACT FROM AUTHOR]

Introduction: Insulation defects are a leading cause of transvenous lead failure. The purpose of this study was to determine the effects of electrocautery on transvenous lead insulation materials. Methods: A preparation was done to simulate dissection of a transvenous lead from tissues. Radiofrequency energy was delivered using a standard cautery blade at outputs of 10, 20, and 30 W, for 3 and 6 seconds, using parallel and perpendicular blade orientations on leads with outermost insulations of silicone rubber, polyurethane, and silicone–polyurethane copolymer. Damage to each lead segment was classified after visual and microscopic analysis. Results: Significant insulation damage occurred to almost all polyurethane leads. Full insulation breaches were observed with 30 W regardless of application duration with a parallel direction and with all power outputs with a perpendicular direction. Thermal insulation damage to copolymer insulation was similar to that of the polyurethane leads. In contrast, there was no thermal damage to silicone leads, regardless of the power output and duration of power delivery. However, mechanical insulation damage was observed to all silicone leads when at least 20 W was applied in a direction perpendicular to the lead. Conclusions: Polyurethane (PU55D) and copolymer materials have low thermal stability and are highly susceptible to thermal damage during cautery. Implanting physicians should be aware of the lead insulation materials being used during implant procedures and their properties. The use of direct contact cautery on transvenous leads should be minimized to avoid damage to the lead, especially on leads with polyurethane or copolymer outer insulations. [ABSTRACT FROM AUTHOR]

Background: The potential advantages of using a 4Fr lumenless pacing lead (3830 SelectSecure™, Medtronic Inc, Minneapolis, MN, USA) in children are largely negated due to the large size of the delivery system. Here we describe an innovative, sheath guided, delivery technique using conventional 5F sheaths. Methods: Transvenous access was obtained via the left cephalic or axillary vein. A 5Fr introducer set with a 45° curved tip (CheckFlo® Performer® Introducer Set with the Children's Hospital Boston Modification, Cook Medical Inc, Bloomington, IN, USA) was placed over a wire into the right atrium (RA) or right ventricle (RV). The sheath was modified by cutting off the valved end and a SelectSecure™ lead was introduced through the sheath. Rotating the sheath provided steerability and allowed for precise placement of the lead. After successful lead placement, the sheath was removed with a universal sheath splitter. Results: We placed seven atrial and six ventricular leads in eight patients during nine separate cases with this method. Patient ages and weights ranged from 5 to 16 years and 16 to –59 kg respectively. Pacing thresholds were excellent at implant. Leads were placed successfully in all attempts. There were no procedural complications. One patient had leads placed twice; both lead systems were removed for suspected infection. Over short-term follow-up in five patients, lead position and characteristics have remained stable. Conclusion: Delivery of the SelectSecure™ lead in children can be successfully and precisely performed using a modified 5Fr sheath obviating the need for a large steerable delivery system. [ABSTRACT FROM AUTHOR]

Information about several papers discussed at a conference organized by the International Cardiac Pacing and Electrophysiology Society (ICPES) in December 2007 in Rome, Italy is presented. Topics included those on pacemakers and implantable cardioverters and on how to improve device performance monitoring. It featured several professors including C. P. Lau from Hong Kong, China and M. Santini.

Objectives: Implantation of an additional HV-P/S lead versus extraction of the defective HV-P/S lead and implantation of a new one is one possible therapeutic approach in cases of a defective high-voltage pace/sense lead (HV-P/S). No information is available on potential differences in clinical outcome in these different approaches. Methods: Between January 2000 and February 2006, 86 patients with HV-P/S lead defect received either an additional transvenous HV-P/S lead (n = 33, group 1) or the HV-P/S lead was replaced (n = 53, group 2). The duration of the initially implanted leads was significantly different in the two groups (7.4 ± 2.9; group 1 and 4.1 ± 3.4 years; group 2).The outcome of these two groups of patients was retrospectively analyzed. Results: Seventy-three patients [85%] survived until the end of follow-up of 29 ± 15 (group 1) and 33 ± 21 (group 2) months (P = ns), respectively. Thirteen patients died: six in group 1 and seven in group 2 (P = ns). Fourteen patients experienced perioperative complications (group 1: six; group 2: eight; P = ns). ICD system-related complications occurred in 22 patients (group 1: seven; group two: 15; P = ns). The event-free cumulative survival of patients with additional and replaced HV-P/S lead for postoperative events (including death) after 1, 2, and 3 years was 82%, 70%, 70%, and 86%, 81%, 66%, respectively (P = 0.93). Conclusions: Implantation of an additional HV-P/S lead or replacement of the HV-P/S lead in case of HV-P/S lead failure is statistically not different concerning mortality and morbidity. There are no predictors for further lead defects. Implantation of an additional HV-P/S lead should not be recommended in young patients or patients with greater likelihood of living many years. Predictors for death were an age over 70 years and renal insufficiency. [ABSTRACT FROM AUTHOR]

Introduction: Much clinical evidence has shown that right ventricular (RV) apical pacing is detrimental to left ventricular function. Preservation of the use of the His-Purkinje (H-P) system may be ideal in heart block that is restricted to the AV node, but may be of no benefit when H-P disease exists. Aim: To investigate the feasibility of direct His-bundle pacing (DHBP) using a new system consisting of a steerable catheter and a new 4.1 F screw-in lead. Method: Between May and December 2004, 26 patients (19 male, mean age: 77 ± 5 years) with a standard pacemaker (PM) indication and preserved His-bundle conduction were enrolled and DHBP was attempted. Results: DHBP was achieved in 24 patients (92%); two patients were paced in the His area, but the paced QRS morphology and duration were different from the native QRS. The mean time for lead positioning was 19 ± 17 minutes, the mean fluoroscopy time was 11 ± 8 minutes, and the total procedure time (skin-to-skin including positioning of a quadripolar diagnostic catheter for His recording) was 75 ± 18 minutes. In DHBP pacing, the acute pacing threshold was 2.3 ± 1.0 V at a pulse duration of 0.5 msec, and the sensed potentials were 2.9 ± 2.0 mV. At a 3-month follow-up examination, the same QRS duration and morphology recorded on implantation were observed in all patients. The pacing threshold was 2.8 ± 1.4 V, and sensed potentials were 2.5 ± 1.8 mV; the sensing configuration was changed from bipolar to unipolar in 6 patients to resolve undersensing issues. No major complications were observed. Conclusions: This feasibility study shows that DHBP can be accomplished with a new system consisting of a steerable catheter and an active fixation lead in 92% of the patients in whom it was attempted. [ABSTRACT FROM AUTHOR]

WOLLMANN, C.G., et al.: Incidence of Complications in Patients with Implantable Cardioverter/Defibrillator Who Receive Additional Transvenous Pace/Sense Leads. Background: Implantation of an additional pace/sense (P/S) lead is commonly used in patients with implantable cardioverter/defibrillators (ICDs) to overcome P/S defects of integrated defibrillation leads (HV-P/S leads). No information is available about the clinical outcome and the incidence of complications in these patients. Methods: Retrospective analysis was performed in 151 patients (125 male, age 54.9 ± 13.6 years, LVEF 48.1 ± 17.8%, CAD in 86 [57%], DCM in 24 [16%], ARVCM in 11 [7%]) who received an additional P/S lead between 1990 and 2002 (54 patients with abdominal and 97 patients with pectoral ICD system). Statistical analysis was done using Kaplan-Meier survival curves. Results: The average follow-up (FU) after implantation of the additional P/S lead was 43 ± 27 months. In total 117 patients [77.5%] remain implanted; 22 patients died due to cardiac-related reasons. After a FU of 23 ± 23 months, 43 patients [28.5%] experienced lead-related problems after implantation of the additional P/S lead: oversensing in 23 [53.5%], insulation defect in 3 [7.0%], fracture in 1 [2.3%], system infection in 4 [9.3%], and defect of the HV-P/S lead in 6 [14.0%] patients. The event-free cumulative survival of the additional P/S lead after 1, 2, and 5 years was 87.0%, 79.8%, and 59.4%, respectively (for pectoral leads: 89.6%, 82.0%, and 60.0%, respectively). Conclusions: Implantation of an additional P/S lead in case of failure of an HV-P/S lead is safe. However, it is associated with a substantial rate of complications during FU. Therefore, extraction of damaged defibrillation leads instead of implantation of P/S leads should be favored. (PACE 2005; 28:795–800) [ABSTRACT FROM AUTHOR]

GULA, L.J., et al.: Central Venous Occlusion Is Not an Obstacle to Device Upgrade with the Assistance of Laser Extraction . Objective: To assess the efficacy and safety of laser-assisted lead extraction for upgrade of existing pacemakers and defibrillators in patients with central venous obstruction. Background: Implantable cardiac defibrillators and biventricular pacing have become the accepted therapeutic measures for patients with congestive heart failure. Many patients who are candidates for device therapy, however, already have existing right ventricular leads and the presence of central venous obstruction. Upgrade of existing devices in these patients is a dilemma, which is increasingly encountered by device-implanting physicians. Laser-assisted extraction of existing leads can facilitate access for device upgrade and provide an alternative to lead abandonment and contralateral implant. Methods: We review our experience with laser-assisted lead extraction in patients, referred for upgrade of existing devices, who were found to have, or known to have, ipsilateral subclavian vein occlusion. Results: Over the past 3 years, 18 patients (13 men, 5 women; mean age 63.9 ± 16 years) with subclavian vein occlusion underwent successful laser-assisted lead extraction (total 29 leads) and upgrade of existing leads to defibrillators and/or biventricular systems. Mean implant duration prior to extraction was 70.8 ± 43.5 (11–192) months. Cannulation of the coronary sinus and placement of a transvenous left ventricular lead were achieved in all 13 patients in whom it was attempted. No complications occurred. Conclusions: Laser-assisted lead extraction is a safe and effective approach, allowing for ipsilateral device upgrade in patients with existing devices and central venous obstruction. (PACE 2005; 28:661–666) [ABSTRACT FROM AUTHOR]

RÜB, N., et al.: Addition of a Defibrillation Electrode in the Low Right Atrium to a Right Ventricular Lead Does Not Reduce Ventricular Defibrillation Thresholds. Transvenous unipolar active can defibrillation systems have proven to be effective in treating ventricular tachyarrhythmias. However, a further reduction of ventricular defibrillation thresholds (V-DFT) would increase the longevity, reduce the size of pulse generators, and help to avoid additional leads in patients with inacceptable high V-DFTs. In a finite difference computer model, the extension of the right ventricular (RV) defibrillation coil into the low right atrium led to a 40% reduction of unipolar V-DFT. To evaluate this finding, we conducted a prospective, randomized study in 11 patients receiving an ICD. Extension of the RV electrode was simulated by adding a second coil placed in the low right atrium with the same polarity. Using a binary search protocol, V-DFT was determined with and without the additional electrode in each patient. Total shock impedance was significantly lower in the two coil (low RA) configuration, compared to the single coil (RV) configuration. Corresponding values were 49.9 ± 6.7 Ohm and 61.1 ± 9.3 Ohm, respectively (P < 0.01, paired t-test). However, there was no reduction, but even a nonsignificant increase in V-DFTs. Mean V-DFT in the RV configuration was 12.0 ± 5.6 J and 16.3 ± 7.8 J in the low RA configuration (P = 0.09, paired t-test). Despite a reduction in total impedance, the addition of a defibrillation coil in the low right atrium does not reduce ventricular defibrillation thresholds. (PACE 2004; 27:346–351) [ABSTRACT FROM AUTHOR]

GRADAUS, R., et al.: ICD Leads: Design and Chronic Dysfunctions. The treatment of ventricular tachyarrhythmias has changed over the last 10 years. Implantable cardioverter defibrillators (ICDs), once used only as a last resort therapy, have now become the treatment of choice. This change occurred before the first results of randomized studies on ICD therapy in patients with life-threatening ventricular tachyarrhythmias were published by the end of 1997. Technological advances of ICD therapy, in particular the development of transvenous leads, were to a large extent responsible for this change. Modern leads are characterized by their multilumen design that incorporates straight wires and coiled conductors into a single electrode body. Conductors and insulation are sheathed with additional insulation layers. The most frequently used insulating materials are silicone, polyurethane, and fluoropolymers. Lead failures are an important complication of ICD therapy. Fractured conductors, compression, creeping, or insulation defects from abrasion can cause such lead dysfunctions. Chronically implanted leads will inevitably have an increased risk of failure due to defects despite all technological advances. In the light of improving survival figures in patients with ventricular tachyarrhythmias and increasing numbers of ICD implantations, lead failures are becoming a clinical problem of ever increasing importance. Therefore, the question of which lead types necessitate extraction when a certain failure occurs and which leads can be left in place. Despite continuous improvements in lead extraction systems and growing experience in their use, the extraction of any pacemaker or ICD lead is associated with some risk of complications. (PACE 2003; 26[Pt. I]:649–657). [ABSTRACT FROM AUTHOR]

Transvene models 6936/6966, a coaxial polyurethane ICD lead, may be prone to structural failure. These models comprise 54% of ICD lead failures in the authors' Multicenter Registry database. Because ICD leads perform a vital function, the clinical features, causes, and probability of Transvene 6936/6966 lead failure were determined. The Registry and United States Food and Drug Administration databases were queried for the clinical features and structural causes of the Transvene 6936/6966 lead failure, and a five-center substudy estimated the survival probability for 321 Transvene 6936/6966 implants. The mean time to failure was 4.8 ± 2.1 years, and the estimated survival at 60 and 84 months after implant were 92% and 84%, respectively. Oversensing was the most common sign of failure (76%), and 24 patients experienced inappropriate shocks. The manufacturer's reports indicated that high voltage coil fracture and 80A polyurethane defects were the predominant causes of lead failure. Transvene models 6936 and 6966 coaxial polyurethane ICD leads are prone to failure over time. Patients who have these leads should be evaluated frequently. Additional studies are needed to identify safe management strategies. [ABSTRACT FROM AUTHOR]

Pericarditis has been noted as a potential complication of pacemaker implantation. This study evaluated the risk of developing pericarditis following pacemaker implantation with active-fixation atrial leads. Included were 1,021 consecutive patients (mean age 73.4 ± 0.4 years, range 16-101 years ;45.2% women ) undergoing new pacemaker system implantation between 1991 and 1999 who were reviewed for the complication of pericarditis. The incidence and outcomes of postimpiantation pericarditis in patients receiving active-fixation atrial leads were compared to those not receiving these leads. Of 79 patients who received active-fixation atrial leads, 4 (5%) developed pericarditis postpacemaker implantation. Of 942 patients with passive-fixation atrial leads or no atrial lead (i.e., a ventricular lead only), none developed pericarditis postoperatively (P < 0.001). Of patients receiving active-fixation ventricular leads only (n = 97), none developed pericarditis. No complications were apparent at the time of implantation in patients who developed pericarditis. Pleuritic chest pain developed between 1 and 28 hours postoperatively. Three patients had pericardial rubs without clinical or echocardiographic evidence of tamponade. They were treated conservatively with acetyisalicylic acid or ibuprofen and their symptoms resolved without sequelae in 1-8 days. One patient (without pericardial rub) died due to cardiac tamponade on postoperative day 6. Postmortem examination revealed hemorrhagic pericarditis with no gross evidence of lead perforation. Pericarditis complicates pacemaker implantation in significantly more patients who receive active-fixation atrial leads. It maybe precipitated by perforation of the atria! lead screw through the thin atrial wall. Patients developing postoperative pericarditis should be followed closely due to the risk of cardiac tamponade. [ABSTRACT FROM AUTHOR]

A new segmented polyether polyurethane atrial pacemaker lead has been developed and tested acutely and chronically in dogs. This lead was constructed so that its tip could quickly and accurately be positioned in close proximity to the S-A node and provide long-term stability without the use of active fixation devices such as tines or screws. The acute intrinsic P-wave potentials seen at the S-A node area (9.7 ± 4.7 mV) were superior to those detected in the appendage (4.7 ± 2.8 mV) and coronary sinus (6.8 ± 4.1 mV). There were no significant differences in pacing thresholds between sites. In long-term studies, transvenous (jugular) leads maintained their position for over three months without dislodgment in active unrestrained dogs with only a 25% decrease in intrinsic P-wave potentials. The chronic pacing thresholds for this lead were similar, or superior, to those reported for other pacemaker lead placement sites. The polyurethane coating material produces no adverse tissue reaction or thrombosis. [ABSTRACT FROM AUTHOR]

One hundred five implantable cardioverter defibrillator (ICD) patients (71 ± 9 years of age, 83% men) without spontaneous ICD discharges for ≥ 12 months were tested to assess high voltage (HV) circuit integrity and the system's ability to recognize and terminate ventricular fibrillation (VF). Indications for ICD implantation were sustained ventricular tachycardia (VT) (35%), cardiac arrest (27%), and inducible VT (38%). Eighty-two percent of the patients had coronary artery disease (CAD), and the mean left ventricular ejection fraction (LVEF) was 36% ± 13%. Results: One hundred patients had inducible VF and five did not. Testing led to ICD reprogramming in 50 (49%) patients. Two (1.9%) patients required ICD replacement: (1) a 45-year-old patient with a Ventritex 110 ICD implanted for 13 months interfaced with a CPI 0062 lead implanted for 46 months could not be defibrillated internally (impedance nonmeasurable); (2) an 82-year-old patient with a 23-month-old Medtronic 7219 ICD interfaced with 6936 and 6933 leads whose defibrillation threshold (DFT) had doubled since implantation (24 J from 12 J). Lead fractures were found in both cases (proximal coil of the 0062, and subcutaneously in the 6933). Based on DFT determinations, the first shock output was programmed lower in 37 patients and higher in 10 patients. Shock pulse width was changed in one patient and the ventricular refractory period in another. No programming changes were made in 54 (51 %) patients. Conclusions: (1) Late testing of HV circuit integrity in ICD patients without an ICD shock in ≥ 12 months identifies previously unsuspected HV lead fractures; (2) chronic DFT testing resulted in HV output reprogramming in one-half of the patients. [ABSTRACT FROM AUTHOR]

AutoCapture™ is a programmable feature of the Pacesetter Microny™ SR+2425T Wilt pacemaker, which provides for the automatic capture verification, increase in output in the presence of noncapture and threshold searching, with adjustment of output settings. The effectiveness of this unit in conjunction with the Membrane™ models 1400T and 1401T bipolar endocardial leads was studied in 54 patients followed at 19 Italian Centers. The patients were randomized at the time of implantation to receive either the model 1400T or the 1401T lead. The electrodes in these leads are covered by a Nation membrane, which was either impregnated (model 1400T) or not-impregnated (model 1401T) with steroid. This paper reports the data collected over the first six weeks postimplantation. The results of the automatic capture function was compared to the capture threshold measured using the Vario™ technique at the time of predischarge evaluations, and weeks 1, 2, and 6 of postimplant follow-up. The reliability and effectiveness of the pulse generator lead system allowed for consistent pacing at very low outputs and safety preserved at a programmed output only 0.3 V above the capture threshold. [ABSTRACT FROM AUTHOR]

Background: Nonthoracotomy systems are rapidly becoming the preferred surgical method for implantation of cardioverter defibrillators. Testing is performed at the time of implantation to insure an adequate margin of safety for defibrillation. However, this safety margin may change with lead maturation. This study evaluated changes in defibrillation threshold following implantation of a nonthoracotomy system. Methods and Results: Ten dogs underwent implantation of a nonthoracotomy system consisting of a single catheter with a distal coil electrode in the right ventricular apex and a proximal coil electrode in the superior vena cava forming a common anode with a subcutaneous patch over the left thorax. Defibrillation threshold testing, using a biphasic waveform, was performed on each animal under general anesthesia at implantation (day 1) and subsequently on postoperative days 3, 7, 10, 17, 24, 31, 38, and 45. E50, the energy associated with a 50% likelihood of successful defibrillation, was determined at each setting. The mean E50 was 12.2 ± 1.1 J at the time of implantation, increasing 36% to 16.8 ± 2.0 J by day 38 (P < 0.01). Individual increases in E50 of 10-12 f were observed in four animals. Conclusions: Energy requirements for defibrillation with a nonthoracotomy system increase during the early postoperative period, with the highest defibrillation threshold observed at 38 days. This increase may be applicable to humans and should be considered when selecting an adequate energy safety margin for defibrillation at time of implantation. [ABSTRACT FROM AUTHOR]

Much research has been done to lower defibrillation thresholds (DFT) through improved waveforms and electrodes. We hypothesized that DFTs are declining steadily, as did pacing thresholds. We performed a meta-analysis of 105 reports of DFTs from 58 articles and abstracts published from 1973 to 1991. Human, dog, and pig studies were included. Transthoracic and isolated heart studies were excluded. Variables analyzed were: publication year, human study, epicardial electrodes only, multiple pathways (simultaneous or sequential), biphasic wave, subcutaneous patch: coronary sinus electrode, spring-patch combination, and catheter-based. DFTs are highly correlated with publication year (P = 0.013) and show an average drop of 0.75 joules/year by a linear univariate analysis. A linear multivariate analysis (r² = 0.51) gave six significant variables for the DFT: epicardial electrodes only, subcutaneous patch, biphasic wave, coronary sinus electrode (each decreased DFTs), and human subject and catheter-based system (increased DFTs). Conclusions: DFTs have shown a decline over 18 years through electrode and waveform improvements. The practice of making devices with ever increasing energy ratings may eventually merit reexamination. The animal model is a useful predictor for clinical DFTs. [ABSTRACT FROM AUTHOR]

VDD stimulation using a single catheter for atrial sensing and ventricular sensing and pacing has become a reality. In order to compare the quality of the cavitary atrial electrogrom (AEG) and to determine the intraatrial P wave direction and conduction time (CT), we compared, in an acute study, three different types of atrial electrode systems using four different leads, in 53 patients in sinus rhythm. The three electrode systems were: (1) one experimental system with quadripolar orthogonal electrodes using the Goldreyer concept: (2) one experimental system with quadripolar whole ring electrodes: (3) two systems with diagonally oriented half-ring electrodes, one experimental quadripolar and one bipolar CCS commercial (Polysafe A-Track lead). For the experimental systems, the four electrodes forming two independent bipolar pairs were situated on the intraatrial floating portion of a single lead and one supplemental electrode was distally positioned in the right ventricular apex. Bipolar AEGs were recorded at the high and at the low levels of the right atrium. For the CCS lead, the single bipolar AEG was recorded of the high level of the right atrium only. The highest AEG amplitude and the highest values for ventricular far-field rejection were provided by both diagonally oriented half-ring electrodes at the high atrial level and by the whole ring electrodes at the low atrial level. For both atrial levels, the orthogonal electrode system provided the smallest AEG amplitudes, the highest ventricular electrogram amplitudes, and therefore, the smallest values for ventricular far-field rejection. With the three quadripolar experimental systems, in sinus rhythm, the direction of the intraatrial depolarization was high-low in 46 patients (87%) and low-high in 3 patients (6%). with a mean CT of 28.9 ms and 23.3 ms, respectively: high and low AEGs were recorded simultaneously in 4 patients (7%). During ventricular pacing, retrograde (V-A) conduction was present in 35... [ABSTRACT FROM AUTHOR]

Early polyurethane leads were reported to have a high incidence of materials failure. In 1979 a six-center registry was begun. By October 31, 1989, 7,311 leads hod been registered and lead longevity was calculated by individual manufacturer, cumulatively for all manufacturers and for individual leads. Each lead was registered at implant and at removal from service as having been removed for materials failure or for unrelated reasons. Calculations were mode for 23 models and for a total of three manufacturers with more than 100 leads implanted. Four thousand seven hundred and sixty three leads (65.1%) were from Medtronic; 2,177 (29.8%) from Cordis; 297 (4.1%) from Intermedics; and 77 (1.0%) were from all others. The 10-year cumulative survival of Medtronic leads was 96.6 ± 0.4%; for Cordis leads it was 99.9 ± 0.1% and for Intermedics leads 97.7 ± 0.9%. Three lead models registered over 100 units and had poorer survival at 5 years than the remainder of all manufacturers' experience. They were #6972 (n = 107) with 78.6 ± 4.5%; #6991U (n = 294) with 90.6 ± 1,9%: and #4012 (n = 288) with 97.3 ± 1.5%. Other possibly failed models did not achieve statistical significance. It can be anticipated that a lead which survives to the seventh year will have prolonged longevity as thereafter additional failures are uncommon. [ABSTRACT FROM AUTHOR]

Although several types of commercially available epicardial leads exist, few postimplantation data have been reported. To compare ‘screw-in’ (6917-35) leads with ‘stab-on’ leads (4951-35) from the same manufacturer, we reviewed the records of 80 young patients (age 8 days to 29 years) who underwent ventricular epicardial pacemaker implantation from 1973 to 1986. Follow-up for the 57 patients with the 6917-35 model ranged from 3 months to 17 years (median 6.5 years) and for the 23 patients with the 4952-35 model 9 days to 4.25 years (median 2.0 years). Actuarial life table analysis revealed significantly (P < 0.001) fewer 4951-35 leads were functioning at each of 1–5 years after implant, compared to the 6917-35 leads. Analysis of available threshold pulse width data revealed no difference (P = 0.08) acutely (6 weeks after implant), but a significantly (P = 0.05) higher mean threshold for the 4951-35 leads was found chronically. No significant correlation was found for lead failure with age, underlying heart .disease, lead site (i.e., left or right ventricle), or surgical approach. Using the sutureless, stab-on technique, me 4951-35 lead is associated with higher thresholds and lower survival rate when compared to the 6917-35 lead. [ABSTRACT FROM AUTHOR]

Individuals with permanently implanted pacemakers who have normal sensing and pacing at rest may demonstrate abnormalities, particularly of atrial sensing, with exercise. Exercise is known to cause changes in the surface electrocardiographic voltages. The purpose of this study was to evaluate changes in endocardial and epicardial voltages during exercise in canines with permanently implanted pacing leads similar to those permanently implanted in humans with pacemakers. Six adult mongrel dogs were equipped with transvenous atrial and ventricular endocardial bipolar screw-in leads from a jugular venosection, and with atrial and ventricular bipolar stab-on leads from a left thoracotomy. Exercise was performed at one week following implantation and at weekly intervals for a total of 4 weeks. The animals were studied at rest and at a single workload of 3 miles per hour at a 30% elevation. Unfiltered electrograms were recorded with a VR-12 Electronics-for-Medicine photographic recorder. The mean decreases of electrograms with exercise from resting voltage were: 15% for atrial endocardial unipolar leads; 11% for atrial endocardial bipolar leads; 4% for atrial epicardial unipolar leads; 15% for atrial epicardial bipolar leads; 8% for ventricular endocardial unipolar leads; 18% for ventricular endocardial bipolar leads; 0.1% for ventricular epicardial unipolar leads and 5% for ventricular epicardial bipolar leads. [ABSTRACT FROM AUTHOR]

The patterns resulting from improper connections of the right leg (ground) cable to the right arm, left arm, and left leg electrodes (hardly ever discussed in books dealing with electrocardiography) are presented and their genesis is explained. Knowledge about this technical error is important because it: (1) may be misinterpreted as resulting from switching the right arm and left arm cables; and, worse, (2) may not be recognized, which, in patients with abnormal electrocardiograms, can lead to clinically significant errors in interpretation. [ABSTRACT FROM AUTHOR]

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Introduction: High atrial defibrillation energy requirements (ADER) in patients with chronic atrial fibrillation (AF) may limit the acceptance of transvenous atrial defibrillation. We evaluated an optimized defibrillation electrode configuration that could help to reduce the ADER in patients with AF. Methods and Results: We tested ten different configurations in nine dogs with AF (3.33 ± 2.92 days) induced by rapid atrial pacing. The configurations were: right atrial (RA) appendage as anode and coronary sinus (CS) as cathode; RA and innominate vein (I) as anode to CS (cathode); RA-CS (anode) to I (cathode); I-CS (anode) to RA (cathode); RA and left lateral subcutaneous patch (P) as anode to CS (cathode); RA-CS (anode) to P (cathode); P-CS (anode) to RA (cathode); superior vena cava (SVC) and CS (anode) to RA (cathode); RA-CS (anode) to SVC (cathode); and RA-SVC (anode) to CS (cathode). ADER was defined as the voltage needed to defibrillate the atria in 10% to 90% of 20 consecutive shocks. Three lead systems had ADER lower than the RA (anode) to CS (cathode) configuration, which required a mean of 143 ± 58 volts. These three were: RA-SVC (anode) to CS (cathode) 103 ± 29 V; I-CS (anode) to RA (cathode) 129 ± 39 V; and P-CS (anode) to RA (cathode) 130 ± 38 V. The remaining configurations had ADER higher than the RA (anode) to CS (cathode) configuration. Conclusion: Adding an additional shocking electrode may reduce ADER when compared with the RA (anode) to CS (cathode) configuration. This concept could be incorporated into future implantable atrial defibrillators or used for refractory patients undergoing temporary transvenous cardioversion. [ABSTRACT FROM AUTHOR]

Techniques and Technology. The use of magnetic resonance (MR) imaging as a diagnostic technique is rapidly expanding. In parallel, the number of patients with cardiac devices is constantly growing and many of them may be referred for MR examinations. However, implantable cardiac devices are subject to multiple effects from MR, and numerous safety issues need to be considered prior to scanning. In this review, we will summarize our experience with MR imaging of patients with implantable cardiac devices, and outline our safety protocol. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1040-1042, September 2012) [ABSTRACT FROM AUTHOR]

This case reports on an 81-year-old man with implanted dual-chamber pacemaker for binodal disease who required ventricular lead revision due to loss of ventricular capture. Successful placement of a new lead via the subclavian vein despite of high degree stenosis of the medial part of the vein is described using a very thin bipolar ventricular pacing lead. Currently available pacing electrodes for this purpose are reviewed. [ABSTRACT FROM AUTHOR]