Suspended SOI waveguide with sub-wavelength grating cladding for mid-infrared.

We present a new type of mid-infrared silicon-on-insulator (SOI) waveguide. The waveguide comprises a sub-wavelength lattice of holes acting as lateral cladding while at the same time allowing for the bottom oxide (BOX) removal by etching. The waveguide loss is determined at the wavelength of 3.8 µm for structures before and after being underetched using both vapor phase and liquid hydrofluoric acid (HF). A propagation loss of 3.4 dB/cm was measured for a design with a 300 nm grating period and 150 nm holes after partial removal (560 nm) of BOX by vapor phase HF etching. We also demonstrate an alternative design with 550 nm period and 450 nm holes, which allows a faster and complete removal of the BOX by liquid phase HF etching, yielding the waveguide propagation loss of 3.6 dB/cm.

The cardiac catheterization lab: implementing best practice in Trinidad and Tobago

On 13 May 2012, the Quarterly Cardiology Conference program was organized by the Trinidad and Tobago Medical Association and The University of the West Indies, St. Augustine. The program provided a forum for discussion of issues related to the implementation of best practices in the management of patients requiring cardiac catheterization laboratory (Cathe Lab ) procedures. The participants who were stakeholders in the management of patients referred for catheter-based procedures reviewed best practice guidelines for patients, identified local barriers to the implementation of these best practices and made recommendations for the implementation of these best practice guidelines

First time and repeat cardioversion of atrial tachyarrhythmias - a comparison of outcomes.

INTRODUCTION: Repeat cardioversion may be necessary in over 50% of patients with persistent atrial fibrillation (AF), but identifying responders remains challenging. This study evaluates the long-term success of direct current cardioversion (DCCV) and the clinical and echocardiographical parameters that influence them, in over 1000 sedation-cardioversion procedures undertaken at Eastbourne General Hospital between 1996 and 2006. METHODS: A total of 770 patients of mean age (SD) 70.1(10.1) underwent 1013 DCCVs (first n = 665, repeat n = 348) for atrial tachyarrhythmias from 1996 to 2006. Time to persistent arrhythmia recurrence was compared between first and multiple DCCV, and the effect of age, gender, presence of heart disease, left atrial size, fractional shortening, arrhythmia duration, anti-arrhythmic drug therapy (AAD) and other concomitant cardiac medication was evaluated using the Kaplan-Meier method and Cox's Proportional-hazards model. RESULTS: In all, 33% of first and 29% of repeat DCCVs were in sinus rhythm (SR) at 12 months (m). There was no difference in median time to arrhythmia recurrence (SE) between first and multiple procedures: 1.5 +/- 0.1 m (1.3-1.7) and 1.5 +/- 0.0 m (1.4-1.6) respectively, p = 0.45. AAD use was significantly higher, arrhythmia duration shorter and more diabetic patients underwent repeat procedures. Amiodarone, OR 0.56, p = 0.04, sotalol, OR 0.61, p = 0.02 and arrhythmia duration, < 6 m, OR 0.72, p = 0.03 were independent predictors of improved outcome in first procedures only. In patients undergoing first procedures on amiodarone or sotalol, median time to arrhythmia recurrence was longer and 12 m SR rates higher, 6.0 +/- 2.4 m (42%) than those who had a repeat procedure on the same medication, 1.5 +/- 0.1 m (33%), p = 0.06. CONCLUSIONS: The efficacy of first and subsequent DCCV procedures is similar, achieving a similar proportion of SR maintenance at 1 year. However, the benefits of AAD therapy are the greatest following first time procedures. Concomitant AAD therapy should be considered for all first time procedures for persistent AF.

The safety and effectiveness of a nurse led cardioversion service under sedation.

OBJECTIVE: To assess the safety and effectiveness of nurse led elective cardioversion of atrial fibrillation under sedation. DESIGN: Prospective, longitudinal study. SETTING: Cardiac catheterisation laboratory and recovery area of a district general hospital. PATIENTS: 300 patients referred for elective cardioversion of persistent atrial fibrillation. INTERVENTIONS: Pre-procedure evaluations (history, physical examination, blood tests), consent, sedation administration, cardioversions, and post-procedure monitoring until discharge by advanced life support certified coronary care unit nurses trained in the techniques. A doctor was immediately available if required but not present. MAIN OUTCOME MEASURES: Success rates at discharge and at six weeks, energy delivered, number of shocks, dose of sedation, immediate, 24, and 48 hour patient perceptions, complications, waiting times, and cost effectiveness. RESULTS: Cardioversion success rate was 87% at discharge and 48% at six weeks. Mean (SD) cumulative energy was 497 (282) J and number of shocks 1.6 (0.8). Mean (SD) dose of sedation was 23 (9) mg intravenous diazepam. No patient required reversal of sedation, airway support, or medical intervention. Ninety eight per cent of patients had no pain or recall of the procedure. Four patients who were adequately anticoagulated experienced embolic phenomena. Ninety eight per cent of patients would repeat the procedure if necessary. Without requirement for a physician or anaesthetist, waiting times for elective cardioversion fell from three months to under four weeks. There was a significant reduction in the estimated cost of the procedure from 337 pounds sterling with general anaesthesia to 130 pounds sterling with nurse led sedation and cardioversion (p < 0.001). CONCLUSION: With appropriate training, a nurse led cardioversion service with sedation is safe, effective, well tolerated, and cost efficient.

The clinical and electrophysiological implications of asymptomatic atrial fibrillation.

Atrial fibrillation (AF) is the commonest arrhythmia encountered in clinical practice and is frequently associated with significant symptoms. Asymptomatic AF may also increase the risks of heart failure, thromboembolism and cardiomyopathy but its prevalence is significantly underestimated by routine surveillance methods. The development of long-term external monitors and implantable devices has offered a new insight into the true prevalence of asymptomatic AF. Similar management strategies should be applied to both symptomatic and asymptomatic patient groups and anticoagulation should be continued indefinitely in those with a history of AF and risk factors for thromboembolism. Enhanced detection of clinically silent AF could improve outcomes but the resource implications will be significant.

Diazepam or midazolam for external DC cardioversion (the DORM Study).

AIMS: To compare the clinical efficacy and tolerability of two intravenous sedatives for physician-led DC cardioversion of atrial arrhythmias. METHODS AND RESULTS: One hundred and forty-one patients attending for elective DC cardioversion of atrial arrhythmias were randomized to intravenous midazolam or diazepam. Sedation was administered using titration protocols. Procedure times, operator satisfaction scores and adverse events were documented. The patients immediate, 24- and 48-h recall and awareness of after-effects were obtained from questionnaires. Seventy-one patients received midazolam (mean 12.5 mg) and 70 patients received diazepam (mean 28.1 mg). There were 16 minor adverse events with midazolam (20% hypotension, 3% oxygen desaturation) and nine with diazepam (7% hypotension, 6% required additional analgesia), P = 0.14. There were no major adverse events. Sedation time was 5.0 +/- 3.4 min for midazolam and 6.5 +/- 3.4 min for diazepam (P = 0.0016). Patients awoke 77 +/- 46 min post-sedation with midazolam and 39 +/- 24 min with diazepam (P < 0.0001). There was no recall of the procedure at 48 h and no difference in awareness of after-effects between the two groups at 24 or 48 h, P = ns. CONCLUSION: Physician-led cardioversion of atrial arrhythmias using intravenous sedation is effective and well tolerated. Sedation with diazepam was associated with fewer minor adverse events and a quicker recovery time than midazolam.

Is cardiac catheterization being appropriately utilized in Trinidad and Tobago?

Coronary angiography is an expensive technology which has recently become available in Trinidad and Tobago. Established methods have not so far been proposed to monitor the appropriateness of its utilization. We hypothesized that a frequency of normal results comprising greater than 25 percent of the population undergoing coronary angiography should prompt a review of policy with a view to improving resource utilization. This is consistent with the American Heart Association's benchmark figure of 25 percent set for mature laboratories operating in the United States. We therefore retrospectively reviewed all catheterization records of patients undergoing cardiac catheterization at the Eric Williams Medical Sciences Complex during its first three years of operation (1993-1995). Of a total of 785 patients undergoing procedures, 453 had coronary angiography. The number of studies per year increased from 96 in 1993, to 190 in 1994 and 167 in 1995. Thirty-one percent of patients were reported to have normal coronary arteries in the first year of operation. However, this fell to 22 per cent in 1994 and 21 percent in 1995. The first year's statistics are believed to represent a cautious initial referring practice and a learning curve. Second and third year statistics confirm an appropriate pattern of cost-efficient utilization of cardiac catheterization resources at this institution. We propose that the frequency of the finding of normal coronary angiograms is a valid indicator of the appropriateness of resource utilization, which should be voluntarily reported by catheterization laboratories throughout the region (AU)