Concealed accessory pathways (APs) are considered benign as they can only sustain orthodromic atrioventricular re-entrant tachycardia (ORT). We describe a unique case of a concealed posteroseptal AP where longitudinal surveillance following repeated failed ablation attempts due to abnormal coronary sinus (CS) anatomy revealed spontaneous development of manifest pre-excitation. The pathway was ultimately ablated via the percutaneous epicardial approach. The potential for development of Wolff-Parkinson-White (WPW) syndrome in patients with concealed APs has implications for ongoing surveillance in these patients.

Background To describe the performance and clinical outcomes of consecutive patients having a leadless pacemaker (LP) implanted at a single institution. Methods Clinical data and device parameters were prospectively collected on all patients undergoing LP implantation from November 2015 to April 2018. Results A total of 79 patients (52 male), median age of 78 years, was included. Leadless pacemaker implantation was successful in 76 patients (96%). Implantation failed in two patients due to excessive venous tortuosity and due to inadequate sensing in another. Seventy-three (73) patients (96%) had chronic atrial fibrillation and all had a Class I or II indication for pacing. Procedure time was 29 minutes (IQR 21-43) and fluoroscopy time was 8 minutes (IQR 5-13). The median R wave at implant was 11.2 mV (IQR 6.9-15.0). The median capture threshold at 0.24 ms was 0.5 V (IQR 0.4-0.9) and impedance was 754 SZ (IQR 680-880). Intraprocedural acute dislodgement occurred in one patient following cutting of the tether but successful snaring and reimplantation was performed. During a median follow-up of 355 days (range 9-905), overall electrical performance has been excellent. No patients have been readmitted for device revision or complications. Five (5) patients (7%) died during follow-up from unrelated causes. Conclusions Leadless pacemakers can be implanted safely and effectively in the majority of patients. Device electrical performance was excellent over a median follow-up of 12 months.

Background: Electrophysiology procedures require fluoroscopic guidance, with the associated potentially adverse effects of ionizing radiation. Newer fluoroscopy systems have more features that enable dose-reduction strategies. This study aimed to investigate any reduction in radiation dose between an older fluoroscopy system (Philips Integris H5000, Philips Healthcare, Einhoven, Netherlands) and one of the latest systems (Siemens Artis Q, Siemens Healthcare, Erlangen, Germany), optimized with dose-reduction strategies.Methods: Radiation dose measures were collected over a 2-year period in a single electrophysiology laboratory. Procedures were separated into seven groups: devices, biventricular devices, electrophysiology studies, standard radiofrequency ablation, complex atrial ablation, ablation for ventricular arrhythmias, and pulmonary vein isolation. In the first year, an older fluoroscopy system was used, and in the second year, a new system, with dose reduction strategies. Comparisons were also made to the literature with regard to radiation dose levels.Results: Patient characteristics, fluoroscopy times, number of digital acquisitions, procedural times, and procedural success were largely similar between the old and new system across procedure groups. Overall dose area product (DAP) was reduced by 91% (5.0 [2.0-17.0] to 0.45 [0.16-2.61] Gycm(2) [P > 0.001]) with the new system and was lower across all groups. DAP readings with the new system are some of the lowest published in the literature in all groups.Conclusion: An optimized contemporary digital fluoroscopy system, with low radiation dose configuration and continued good procedural practice, can result in ultra-low radiation levels for all electrophysiology procedures, without compromising procedural time or procedural success.

Patients with Brugada syndrome are at risk of life-threatening ventricular arrhythmias. Epicardial substrate ablation for Brugada syndrome has been described as a means of controlling these arrhythmias and recent reports describe elimination of the Brugada phenotype with ablation. We describe a unique case in which a patient developed inferior J waves with an early repolarization-type electrocardiogram following successful epicardial infundibular substrate ablation (which eliminated the Brugada syndrome electrocardiogram on ajmaline challenge). We discuss the likely underlying pathophysiology responsible for this phenomenon, its relationship to the anatomic obstacles encountered during epicardial ablation, and the implications for long-term arrhythmic risk.

Left objects pose a real threat to security in public areas such as railway stations and airports. Detection of these objects therefore forms an important part in any intelligent video surveillance system that is deployed at such locations. Successful left object detection algorithms must operate in real time and produce sufficient detection accuracy with low false positive rates. However in reality, the requirement of both speed and performance is not often achieved due to the huge variation in image appearance caused by illumination, scene, and foreground objects (both dynamic and static). This paper tackles the challenge using a background subtraction scheme coupled with three other techniques. Short-term frame averaging is used to reduce the effect of moving objects such as pedestrians and vehicles. Statistical image background modelling is applied to enhance the visual contrast between the object and the background. Pixel colour modelling is employed to verify the results of left object segmentation. All three techniques are computationally lightweight and thus enable the left object detection to operate in real time.

Background: In recent months there has been considerable concern and debate regards the safety and performance of low profile ICD leads.

Background: The number of implantable cardiac defibrillators (ICD's) patients has increased considerably since the release of the primary prevention and heart failure trials. Guidelines released by CSANZ in 1999 for the management of deceased patients with ICD's suggest that ICD's should be turned off prior to explant. The question that presents is whether these guidelines are being followed by people explanting devices given the potential danger of receiving high energy shocks.

We report the experimental demonstration of spectral encoding of the polarization state of light by use of multiplexed distributed-feedback lasers in a dye-doped organic thin film by exploiting the pump polarization selectivity of the superimposed resonators. Measurement of the Stokes parameters of the pump light without a priori knowledge of the lasing properties of the structure is discussed.

The emergence of molecular photonics as a new domain of research at the cross-road of physics, chemistry and device engineering is being triggered by the increasing demands of broadband telecommunication systems which start to challenge the fundamental limits of current inorganic semiconductor based technologies. Increasing to 100 GHz and beyond the bandwidth acceptance of optoelectronic devices, such as modulators and switches, or down-scaling device dimensions into the new frontier of quantum physics have become scientific as well as industrially relevant targets, unlikely to be met by unimaginative extrapolation of current avenues. Facing this formidable challenge, the so-far relatively untapped wealth of molecular structures, and the targeted exploitation of their functional as well as structural flexibility throughout consistent molecular, material and device engineering steps, open-up thoroughly renewed horizons. An important asset is the complementarity and technological compatibility of polymer and inorganic semiconductor structures providing the possibility of smooth and economically viable transitions towards hybrid organic-inorganic technological solutions. Major current and foreseeable impacts appear to be in the realm of nonlinear optics (harmonic generation and carrier frequency shifting, routing, electrooptic modulation and switching, pulse shaping and synchronization, nonlinear refraction) and microlasers which will be exemplified by a selection of recent and ongoing developments in our laboratory at different macroscopic, microscopic and nanoscopic scales.

We report the fabrication and characterization of optically pumped multiple grating distributed feedback lasers in dye doped organic thin films. Each multiplexed laser structure is inscribed at a different angle in the sample plane and possesses a unique emission wavelength. The polarization sensitivity of these structures with respect to the pumping light is exploited to enable simple and high-speed switching of the device emission wavelength.

Microcavity lasers are of interest for both fundamental studies of cavity quantum electrodynamics and for potential applications in all‐optical networks. Microrings and microdisks are especially suited for fabricating polymer microcavity lasers. Current research with microcavity lasers has focussed on two areas : (1) laser threshold minimization and (2) directional laser emission. Laser emission is obtained with different optical pumping configurations according the cavity shapes. We present the lasing characteristics of optically pumped luminescent polymer microcavities. Geometrical parameters and pumping configurations are investigated to modify the lasing threshold and the directionality of emissions.

The dependence of the laser threshold of organic distributed-feedback (DFB) lasers having index and surface gratings on the pump polarization angle is studied and examined. A model is developed to describe the relationship between the fluorophore orientational distribution and the number of photons emitted into the laser mode. Experimental data fitted with this model demonstrate that the fluorophores are isotropically oriented in the plane of the sample. The polarization dependence of the laser threshold is then used in conjunction with the measured pump intensity dependence of the emission intensity to explain the pump polarization selectivity of the laser emission of these structures. The effect of the above phenomena on future applications is discussed.

Microcavity lasers are of interest for both fundamental studies of cavity quantum electrodynamics and for potential applications in all-optical networks. Among the different types of microcavities, the microdisk is especially suited for fabricating polymer microcavity lasers. Current research with microdisk lasers has focused on two areas: (1) directional laser emission; and (2) laser threshold minimization. The laser emissions are obtained with optical pumping performed by focusing the pump laser directly on the top face of the microdisks. We present the lasing characteristics of optically pumped luminescent polymer microdisks on semiconductor substrates. Geometrical parameters such as radius disks are shown to affect the lasing threshold.

A set of organic glasses has been synthesized and evaluated for photorefractive performance. The functions of optical nonlinearity, birefringence, and charge transport were built into a single molecule by attaching an NLO chromophore to a charge transport moiety with an adjustable linking group. The longer linking group not only lowers the glass transition temperature T-g but also influences the photorefractive performance of the samples. The photorefractive gain coefficient is larger for longer linkers with about a 2-fold increase going from the 2-carbon atom linker to 12. The glass stability and chemical stability of the materials was adequate for full photorefractive characterization.

The photorefractive properties of the hole-transporting polymer poly(methyl-bis-(3-methoxyphenyl)-(4-propylphenyl)amine)siloxane (MM-PSX-TAA) doped with the photorefractive chromophore 4-di(2-methoxyethyl) aminobenzylidene malononitrile (AODCST) are presented and compared with results obtained on similar composites based on poly(n-vinylcarbazole) (PVK). The low intrinsic T-g of the new polymer allows the preparation of samples without additional plasticizers. These composites exhibit good chromophore orientational. mobility and exhibit photorefractive response times in the millisecond range, among the fastest reported to date.

We report the synthesis and characterization of several related amorphous multifunctional photorefractive (PR) materials with the charge transport agent covalently linked to a chromophore. DCTA (4,4′-di(carbazol-9-yl) triphenylamine) is used as the charge transport agent in conjunction with C60 to provide photoconductivity and DCST (an aminodicyanostyrene) is used as the birefringent and nonlinear optical chromophore. Chains with different lengths (2, 6 and 12 carbons) are used to covalently connect these two moieties. The linking units influence the glass transition temperature of the system, which in turn influences the PR performance. The longer linker allows faster orientation of the chromophore and results in higher PR speed but the response still appears to be limited by the molecular reorientation rather than photoconductivity in these systems.

A monolithic photorefractive organic glass with large gain coefficients at low electric fields is presented. The molecule DCDHF-6 (see Figure) acts simultaneously as charge transport material and nonlinear optical chromophore. Strong beam fanning is observed with suppression of the initial beam to 25 % of its initial value in samples only 100 mum thick.

We present a novel scheme with which to detect small ultrasonic surface displacements by use of a photochromic polymer instead of a photorefractive material as an adaptive beam combiner in a two-wave mixing geometry. Poly(methyl methacrylate) is doped with a derivative of zinc tetrabenzoporphyrin that possesses a long-lived triplet state that can be efficiently populated in a reversible manner. The resulting dynamic hologram consists of local absorption and refractive-index gratings, which can process speckled beams reflected from rough surfaces. We believe that this is the first use of a local nonlinear medium for adaptive homodyne detection of ultrasonic surface displacements.

The photoconductive, orientational, and photorefractive properties of monolithic glasses based on new nonlinear optical chromophores containing a 2-dicyanomethylene-3-cyano-2,5-dihydrofuran (DCDHF) acceptor group are presented. Large net gain coefficients are observed in both red and infrared wavelength regions. The physical and optical properties of glasses based on various DCDHF-containing derivatives are compared and analyzed, and the factors limiting steady-state and dynamical photorefractive performance are discussed.