Upward bias in estimates of pacemaker reliability: effect of unreported patient mortality

OBJECTIVES: This study attempted to determine the effect of unreported patient deaths on estimates of pacemaker reliability. BACKGROUND: The reliability of pacemakers is usually reported with reference to implant registration data and returned product analysis without censoring when follow-up data are missing. METHODS: We studied 73 patients (mean [+/- SD] age 77 +/- 8 years) undergoing implantation of a ventricular-inhibited (VVI) pacemaker who were subsequently found to be at increased risk of experiencing premature pacemaker failure. Survival curves for patients and pacemakers were constructed by the Kaplan-Meier method with appropriate censoring at the time of unrelated death or elective explantation of a normal device. To examine the effect of unreported loss of follow-up data, patient mortality was then ignored, and follow-up for pacemakers without known failure was assumed to continue to the date of analysis. RESULTS: There were 13 device failures, with a median pacemaker survival time of 37 months. Twenty-three patients died, all of causes unrelated to the pacemaker system; median patient survival time was only 44 months. Ignoring this attrition inflated follow-up time from 122 to 188 patient-years and reduced the apparent pacemaker failures at 30 months by almost half, from 37% to only 20%. Modeling the process shows that when the patient mortality rate is more than half the pacemaker failure rate, ignoring censoring inflates the device survival estimate by > or = 10% from the median survival onward. CONCLUSIONS: When medical device survival curves are generated by implant registration data and returned product analysis, they should be adjusted for unreported loss of follow-up.     

Surveillance of tuberculosis in Europe. Working Group of the World Health Organization (WHO) and the European Region of the International Union Against Tuberculosis and Lung Disease (IUATLD) for uniform reporting on tuberculosis cases

Consensus-based recommendations have been developed by a Working Group of the World Health Organization (WHO) and the European Region of the International Union Against Tuberculosis and Lung Disease (IUATLD) on uniform reporting of tuberculosis surveillance data in the countries of Europe. A uniform case definition and a minimum set of variables for reporting on each case have been agreed which, when collated on a national basis, will allow comparison of the epidemiology of tuberculosis in different European countries. The Working Group recommends that the case definition includes "definite" cases, where the diagnosis has been confirmed by culture (or supported by microscopy findings in countries where diagnostic culture facilities are not available), and "other than definite cases" based on a clinical diagnosis of tuberculosis combined with the intention to treat with a full course of antituberculosis therapy. Both "definite" and "other than definite" cases should be notified by physicians and, in addition, laboratories should be required to report "definite" cases. The minimum set of variables to be collected on each case of tuberculosis should include: date of starting treatment, place of residence, date of birth, gender, and country of origin, to characterize the patient. Recommended disease-specific variables include: site of disease, bacteriological status (microscopy and culture), and history of previous antituberculosis chemotherapy. The minimum set of variables should be collated on all patients and should be as complete as possible. Additional variables may be collected for individual, local or national purposes, but, in general, completeness of reporting on cases is likely to be better if the information requested is kept to a minimum. Timely reporting of cases is essential for appropriate public health action. Cases should be reported to the health authority at the local and/or regional level within 1 week of starting treatment. Individual-case based information should be reported to the national level by the local or regional level. Feedback to reporters is essential. At the national level, preliminary quarterly reports should be produced and final reports should be published annually.     

A photovoltaic project for the rural areas of the Eastern Cape, South Africa

This paper reports on a collaborative photovoltaic project recently initiated between three tertiary institutions in the Eastern Cape region of South Africa. The broad objectives of the project are to help establish photovoltaic technology in South Africa, and to produce suitably qualified graduates in this field.     

4‐Alkylated Silver–N‐Heterocyclic Carbene (NHC) Complexes with Cytotoxic Effects in Leukemia Cells

Computational chemistry has shown that backbone‐alkylated imidazoles ought to be efficient ligands for transition metal catalysts with improved carbene‐to‐metal donation. In this work, such alkylated imidazoles were synthesized and complexed with silver(I) by means of an eight/nine‐step synthetic pathway we devised to access a new class of biologically active silver complexes. The synthesis involves selective iodination of the imidazole backbone, followed by Sonogashira coupling to replace the backbone iodine. The installed alkyne moiety is then subjected to reductive hydrogenation with Pearlman’s catalyst. The imidazole N1 atom is arylated by the palladium‐catalyzed Buchwald N‐arylation method. The imidazole N3 position was then methylated with methyl iodine, whereupon the synthesis was terminated by complexation of the imidazolium salt with silver(I) oxide. The synthetic pathway provided an overall yield of ≈20 %. The resulting complexes were tested in vitro against HL60 and MOLM‐13 leukemic cells, two human‐derived cell lines that model acute myeloid leukemia. The most active compounds exhibiting low IC₅₀ values of 14 and 27 μM , against HL60 and MOLM‐13 cells, respectively. The imidazole side chain was found to be essential for high cytotoxicity, as the imidazole complex bearing a C₇ side chain at the 4‐position was four‐ to sixfold more potent than the corresponding imidazole elaborated with a methyl group.     

Capacity upgrade in short-reach optical fibre networks: simultaneous 4-PAM 20 Gbps data and polarization-modulated PPS clock signal using a single VCSEL carrier

In this work, a four-level pulse amplitude modulation (4-PAM) format with a polarization-modulated pulse per second (PPS) clock signal using a single vertical cavity surface emitting laser (VCSEL) carrier is for the first time experimentally demonstrated. We propose uncomplex alternative technique for increasing capacity and flexibility in short-reach optical communication links through multi-signal modulation onto a single VCSEL carrier. A 20 Gbps 4-PAM data signal is directly modulated onto a single mode 10 GHz bandwidth VCSEL carrier at 1310 nm, therefore, doubling the network bit rate. Carrier spectral efficiency is further maximized by exploiting the inherent orthogonal polarization switching of the VCSEL carrier with changing bias in transmission of a PPS clock signal. We, therefore, simultaneously transmit a 20 Gbps 4-PAM data signal and a polarization-based PPS clock signal using a single VCSEL carrier. It is the first time a signal VCSEL carrier is reported to simultaneously transmit a directly modulated 20 Gbps 4-PAM data signal and a polarization-based PPS clock signal. We further demonstrate on the design of a software-defined digital signal processing (DSP)-assisted receiver as an alternative to costly receiver hardware. Experimental results show that a 3.21 km fibre transmission with simultaneous 20 Gbps 4-PAM data signal and polarization-based PPS clock signal introduced a penalty of 3.76 dB. The contribution of polarization-based PPS clock signal to this penalty was found out to be 0.41 dB. Simultaneous distribution of data and timing clock signals over shared network infrastructure significantly increases the aggregated data rate at different optical network units (ONUs), without costly investment.     

All-optical wavelength reuse with simultaneous upstream data and PPS timing signal transfer for flexible optical access networks

All-optical wavelength reuse is a viable approach for realization of low cost colourless ONUs. We experimentally demonstrate a novel all-optical wavelength reuse technique with simultaneous upstream data and pulse-per-second signal transfer, exploiting EDFA gain saturation with a holding beam. A DFB laser is modulated with 8.5 Gbps data and transmitted downstream over 24.7 km fibre. A saturated EDFA located at the ONU is adopted to reduce the extinction ratio of the downstream data from 6.2 dB to 839.1 mdB. This allows for data rewrite and wavelength reuse for upstream transmission. Receiver sensitivities of ?20.19 dBm and ?19.60 dBm are achieved at back-to-back analysis and 24.7 km downstream link respectively. A holding beam is further exploited to attain simultaneous carrier reuse and PPS clock upstream transfer. PPS jitter stability of 1.01 × 10^-08 ns and 6.64 × 10^-08 ns are attained respectively. This work offers a convenient all-optical wavelength reuse solutions for optical access networks.     

Real-time 850 nm multimode VCSEL to 1 550 nm single mode VCSEL data routing for optical interconnects

Short-reach optical interconnects among massive serves in data centers have attracted extensive research recently. Increasing capacity, cost and power efficiency as well as wavelength switching between data center network nodes are still key challenges for current optical interconnects. In this work, we experimentally demonstrate the real-time inter-mode optical wavelength switching technique, for high-speed wavelength flexible data center interconnects. A 10 Gbit/s 1 550 nm single mode vertical cavity surface emitting laser (VCSEL) is optically injected and used to control a 10 Gbit/s multimode VCSEL carrier at 850 nm. Results show that a clearly open eye diagram is achieved at back-to-back analysis, implying a successful wavelength switch and error-free operation at 10 Gbit/s. A fully optical wavelength conversion of a multimode VCSEL operation at 850 nm using a single mode VCSEL subject to external optical injection at 1 550 nm is reported. This work opens new perspectives towards the development of a cost effective high-speed real-time inter-band wavelength switching technique between servers and network devices operating at different transmission windows at network nodes, for current and future optical interconnects.     

Pre to post‐dialysis plasma sodium change better predicts clinical outcomes than dialysate to plasma sodium gradient in quotidian hemodialysis

Sodium balance across a hemodialysis treatment influences interdialytic weight gain (IDWG), pre‐dialysis blood pressure, and the occurrence of intradialytic hypotension, which associate with patient morbidity and mortality. In thrice weekly conventional hemodialysis patients, the dialysate sodium minus pre‐dialysis plasma sodium concentration (δDPNa+) and the post‐dialysis minus pre‐dialysis plasma sodium (δPNa+) are surrogates of sodium balance, and are associated with both cardiovascular and all‐cause mortality. However, whether δDPNa+ or δPNa+ better predicts clinical outcomes in quotidian dialysis is unknown. We performed a retrospective analysis of clinical and demographic data from the Southwestern Ontario Regional Home Hemodialysis program, of all patients since 1985. In frequent nocturnal hemodialysis, δPNa+ was superior to δDPNa+ in predicting IDWG (R² = 0.223 vs. 0.020, P = 0.002 vs. 0.76), intradialytic change in systolic (R² = 0.100 vs. 0.002, P = 0.02 vs. 0.16) and diastolic (R² = 0.066 vs. 0.019, P = 0.02 vs. 0.06) blood pressure, and ultrafiltration rate (R² = 0.296 vs. 0.036, P = 0.001 vs. 0.52). In short hours daily hemodialysis, δDPNa+ was better than δPNa+ in predicting intradialytic change in diastolic blood pressure (R² = 0.101 vs. 0.003, P = 0.02 vs. 0.13). However, δPNa+ was better than δDPNa+ in predicting IDWG (R² = 0.105 vs. 0.019, P = 0.04 vs. 0.68) and pre‐dialysis systolic blood pressure (R² = 0.103 vs. 0.007, P = 0.02 vs. 0.82). We also found that the intradialytic blood pressure fall was greater in frequent nocturnal hemodialysis patients than in short hours daily patients, when exposed to a dialysate to plasma sodium gradient. These results provide a basis for design of prospective trials in quotidian dialysis modalities, to determine the effect of sodium balance on cardiovascular outcome.     

Complexes in serum between alkaline phosphatase and immunoglobulin G: immunological and clinical aspects

A retrospective study was performed on 31 patients in whose sera an immune complex between alkaline phosphatase and immunoglobulin G had been detected. The average age of these patients was 64 years and the sexes were equally represented. Twenty-three patients (74%) had a disease with either an autoimmune aetiology or associated with circulating immune complexes or autoantibodies. Sera from 16 patients were tested for the presence of circulating immune complexes in addition to the alkaline phosphatase immune complex, and these complexes were detected in 14 cases (88%). Sera from 17 patients were tested for the presence of specific autoantibodies and these were detected in 9 cases (53%). Twelve patients were followed up for a mean period of 11.6 months (range 0.5 to 39 month). At the end of the follow-up period, 10 patients (83%) showed persistence of the immunoglobulin-G-alkaline phosphatase complex.