Analysis of Screening Electrocardiogram for the Subcutaneous Defibrillator in Adults with Congenital Heart Disease.

Candidates for the subcutaneous implantable cardioverter-defibrillator (S-ICD) are screened using an electrocardiogram (S-ECG) tool to measure appropriate detection. We sought to define the S-ICD candidacy of congenital heart disease patients using the S-ECG tool. We also analyzed the reliability of the (S-ECG) tool between measurers in this population. Patients above the age of 12 and with a diagnosis associated with either a higher incidence of cardiac arrest or vascular access challenges were asked to undergo screening. S-ECGs were then analyzed by a pediatric electrophysiologist, an S-ICD device engineer, and an S-ICD clinical representative for candidacy. Results were compared for interobserver variability and S-ECGs were analyzed by t test to determine variables that differ among passing and failing leads. Thirty-one patients underwent screening. Two of the 31 (6.5%) patients failed S-ICD screening. Analysis of the screening leads demonstrated the highest passing rates using lead III at a 5 mm/mV amplitude setting with 71 and 62% pass rate in the supine and standing positions, respectively. Interobserver analysis correlated well among the three measurers. There was a higher amplitude difference between QRS and T waves among passing versus failing S-ECG. Congenital heart disease patients have acceptable passage rates utilizing the S-ECG algorithm. Interobserver measurements were well correlated and these data suggest that the proximal coil to device (lead III) vector would be best utilized in this patient population. A larger difference between QRS and T wave amplitudes was associated with a higher S-ECG passing rate.

Highly controllable and stable quantized conductance and resistive switching mechanism in single-crystal TiO2 resistive memory on silicon.

TiO2 is being widely explored as an active resistive switching (RS) material for resistive random access memory. We report a detailed analysis of the RS characteristics of single-crystal anatase-TiO2 thin films epitaxially grown on silicon by atomic layer deposition. We demonstrate that although the valence change mechanism is responsible for the observed RS, single-crystal anatase-TiO2 thin films show electrical characteristics that are very different from the usual switching behaviors observed for polycrystalline or amorphous TiO2 and instead very similar to those found in electrochemical metallization memory. In addition, we demonstrate highly stable and reproducible quantized conductance that is well controlled by application of a compliance current and that suggests the localized formation of conducting Magnéli-like nanophases. The quantized conductance observed results in multiple well-defined resistance states suitable for implementation of multilevel memory cells.

A Low-Leakage Epitaxial High-κ Gate Oxide for Germanium Metal-Oxide-Semiconductor Devices.

Germanium (Ge)-based metal-oxide-semiconductor field-effect transistors are a promising candidate for high performance, low power electronics at the 7 nm technology node and beyond. However, the availability of high quality gate oxide/Ge interfaces that provide low leakage current density and equivalent oxide thickness (EOT), robust scalability, and acceptable interface state density (D(it)) has emerged as one of the most challenging hurdles in the development of such devices. Here we demonstrate and present detailed electrical characterization of a high-κ epitaxial oxide gate stack based on crystalline SrHfO3 grown on Ge (001) by atomic layer deposition. Metal-oxide-Ge capacitor structures show extremely low gate leakage, small and scalable EOT, and good and reducible D(it). Detailed growth strategies and postgrowth annealing schemes are demonstrated to reduce Dit. The physical mechanisms behind these phenomena are studied and suggest approaches for further reduction of D(it).

A silicon-based photocathode for water reduction with an epitaxial SrTiO3 protection layer and a nanostructured catalyst.

The rapidly increasing global demand for energy combined with the environmental impact of fossil fuels has spurred the search for alternative sources of clean energy. One promising approach is to convert solar energy into hydrogen fuel using photoelectrochemical cells. However, the semiconducting photoelectrodes used in these cells typically have low efficiencies and/or stabilities. Here we show that a silicon-based photocathode with a capping epitaxial oxide layer can provide efficient and stable hydrogen production from water. In particular, a thin epitaxial layer of strontium titanate (SrTiO3) was grown directly on Si(001) by molecular beam epitaxy. Photogenerated electrons can be transported easily through this layer because of the conduction-band alignment and lattice match between single-crystalline SrTiO3 and silicon. The approach was used to create a metal-insulator-semiconductor photocathode that, under a broad-spectrum illumination at 100 mW cm(-2), exhibits a maximum photocurrent density of 35 mA cm(-2) and an open circuit potential of 450 mV; there was no observable decrease in performance after 35 hours of operation in 0.5 M H2SO4. The performance of the photocathode was also found to be highly dependent on the size and spacing of the structured metal catalyst. Therefore, mesh-like Ti/Pt nanostructured catalysts were created using a nanosphere lithography lift-off process and an applied-bias photon-to-current efficiency of 4.9% was achieved.

Implantation of implantable cardioverter-defibrillators from an ileofemoral approach.

Patients needing an implantable cardioverter defibrillator (ICD) system, but without suitable access from jugular or subclavian routes present a vexing problem. Such patients would normally undergo thoracotomy for epicardial lead placement. However, for patients who decline such an intervention, there have been no alternatives for them. There is scarce data from the published literature addressing this dilemma. We report two cases of successful ICD and biventricular ICD placement from an ileofemoral approach.

Standard chest radiograph predicts left ventricular lead location in chronic resynchronization therapy patients more accurately than intraoperative fluoroscopy.

INTRODUCTION: Targeting the proper left ventricular lead site is important in cardiac resynchronization therapy (CRT) procedures, as suboptimal lead locations may result in a lack of clinical response. Left ventricular lead locations are typically confirmed using fluoroscopy (fluoro) with AP, RAO, and LAO orientations. However, standard fluoro may inadequately delineate true left ventricular lead locations, due to insufficient angulation or extreme cardiac rotation. Posteroanterior and lateral chest radiograph (CXRPAL), performed routinely to verify lead stability and freedom from complication, may better confirm left ventricular lead location due to utilization of a straight lateral view. HYPOTHESIS: Compared to fluoro, lead localization using CXRPAL will be more predictive of true left ventricular lead location in CRT patients. METHODS: Of 252 medically optimized CHF patients who underwent CRT implantation by multiple operators from October 2001 to August 2011, 46 (mean age, 58.9 ± 13.2 years; 10 female; 19 ICM; 19 LBBB; mean ejection fraction, 26.6 ± 8.9 %; mean QRS width, 144.4 ms) had CT scanning performed as part of routine medical care and comprise this study. Operative reports of left ventricular lead location by fluoro were reviewed. Left ventricular lead location was identified on CXRPAL by three independent observers blinded to operative results. Left ventricular lead locations according to fluoro and CXRPAL were correlated with CT scan at a mean follow-up of 57.6 ± 28.8 months (Tables 1 and 2). RESULTS: Compared to standard fluoro, CXRPAL agreed better with CT scan (κ = 0.413 fluoro vs. κ = 0.864 CXRPAL on the vertical axis, and κ = 0.086 fluoro vs. κ = 0.864 CXRPAL on the horizontal axis) for identification of left ventricular lead location. CONCLUSIONS: In this small study of 46 CRT patients, interpretation of left ventricular lead location using CXRPAL correlated better with true lead location identified on CT scan, compared to standard fluoroscopy. Use of a steep lateral view during CRT implantation may be necessary to accurately identify left ventricular lead locations.