A Concept for a Leaky Wave Antenna Oscillator With Second Order Degeneracy

We exploit a second order exceptional point of degeneracy (EPD) to enhance frequency purity and oscillation stability in oscillators. The EPD we consider in this paper is a regular band edge (RBE) that exists in lossless and gainless periodic waveguides. We present an example of single-ladder oscillator that may act as a leaky wave antenna (LWA). The oscillator we develop has 8 unit-cells that form a resonant cavity and an active element is used to compensate for the losses and start the oscillation. We show that the oscillation frequency is in proximity of the RBE frequency thanks to the second order degeneracy

Distributed Degenerate Band Edge Oscillator

We propose a new class of oscillators by engineering the dispersion of two-coupled periodic waveguides to exhibit a degenerate band edge (DBE). The DBE is an exceptional point of degeneracy (EPD) of order four, i.e., representing the coalescence of four eigenmodes of a waveguide system without loss and gain. We present a distributed DBE oscillator realized in periodic coupled transmission lines with a unique mode selection scheme that leads to a stable single-frequency oscillation, even in the presence of load variation. The DBE oscillator potentially leads to a boost of the efficiency and performance of RF sources, thanks to the unique features associated to the EPD concept. This class of oscillators is promising for improving discrete-distributed coherent sources and can be extended to radiating structures to achieve a new class of active integrated antenna arrays

Intraoperative endomanometric laparoscopic Nissen fundoplication improves postoperative outcomes in large sliding hiatus hernia with severe gastroesophageal reflux disease. A retrospective cohort study

Background: Laparoscopic Nissen Fundoplication (LNF) is the gold standard surgical intervention for gastroesophageal reflux disease (GERD). LNF can be followed by recurrent symptoms or complications affecting patient satisfaction. The aim of this study is to assess the value of the intraoperative endomanometric evaluation of esophagogastric competence and pressure combined with LNF in patients with large sliding hiatus hernia (> 5 cm) with severe GERD (DeMeester score >100). Materials and methods: This is a retrospective, multicenter cohort study. Baseline characteristics, postoperative dysphagia and gas bloat syndrome, recurrent symptoms, and satisfaction were collected from a prospectively maintained database. Outcomes analyzed included recurrent reflux symptoms, postoperative side effects, and satisfaction with surgery. Results: 360 patients were stratified into endomanometric LNF (180 patients, LNF+) and LNF alone (180 patients, LNF). Recurrent heartburn (3.9% vs. 8.3%) and recurrent regurgitation (2.2% vs. 5%) showed a lower incidence in the LNF+ group (P=0.012). Postoperative score III recurrent heartburn and score III regurgitations occurred in 0% vs. 3.3% and 0% vs. 2.8% cases in the LNF+ and LNF groups, respectively (P=0.005). Postoperative persistent dysphagia and gas bloat syndrome occurred in 1.75% vs. 5.6% and 0% vs. 3.9% of patients (P=0.001). Score III postoperative persistent dysphagia was 0% vs. 2.8% in the two groups (P=0.007). There was no redo surgery for dysphagia after LNF+. Patient satisfaction at the end of the study was 93.3% vs. 86.7% in both cohorts, respectively (P=0.05). Conclusions: Intraoperative high-resolution manometry (HRM) and endoscopic were feasible in all patients, and the outcomes were favorable from an effectiveness and safety standpoint

Safety and Efficacy of Myval Implantation in Patients with Severe Bicuspid Aortic Valve Stenosis-A Multicenter Real-World Experience.

Bicuspid aortic valve (BAV) is the most common valvular congenital anomaly and is apparent in nearly 50% of candidates for AV replacement. While transcatheter aortic valve implantation (TAVI) is a recommended treatment for patients with symptomatic severe aortic stenosis (AS) at all surgical risk levels, experience with TAVI in severe bicuspid AS is limited. TAVI in BAV is still a challenge due to its association with multiple and complex anatomical considerations. A retrospective study has been conducted to investigate TAVI's procedural and 30-day outcomes using the Myval transcatheter heart valve (THV) (Meril Life Sciences Pvt. Ltd. Vapi, Gujarat, India) in patients with severe bicuspid AS. Data were collected on 68 patients with severe bicuspid AS who underwent TAVI with the Myval THV. Baseline characteristics, procedural, 30-day echocardiographic and clinical outcomes were collected. The mean age and STS PROM score were 72.6 ± 9.4 and 3.54 ± 2.1. Procedures were performed via the transfemoral route in 98.5%. Major vascular complications (1.5%) and life-threatening bleeding (1.5%) occurred infrequently. No patient had coronary obstruction, second valve implantation or conversion to surgery. On 30-day echocardiography, the mean transvalvular gradient and effective orifice area were 9.8 ± 4.5 mmHg and 1.8 ± 0.4 cm2, respectively. None/trace aortic regurgitation occurred in 76.5%, mild AR in 20.5% and moderate AR in 3%. The permanent pacemaker implantation rate was 8.5% and 30-day all-cause death occurred in 3.0% of cases. TAVI with the Myval THV in selected BAV anatomy is associated with favorable short-term hemodynamic and clinical outcomes

Global economic burden of unmet surgical need for appendicitis

Background: There is a substantial gap in provision of adequate surgical care in many low-and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods: Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results: Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion: For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Laparoscopy in management of appendicitis in high-, middle-, and low-income countries: a multicenter, prospective, cohort study.

BACKGROUND: Appendicitis is the most common abdominal surgical emergency worldwide. Differences between high- and low-income settings in the availability of laparoscopic appendectomy, alternative management choices, and outcomes are poorly described. The aim was to identify variation in surgical management and outcomes of appendicitis within low-, middle-, and high-Human Development Index (HDI) countries worldwide. METHODS: This is a multicenter, international prospective cohort study. Consecutive sampling of patients undergoing emergency appendectomy over 6 months was conducted. Follow-up lasted 30 days. RESULTS: 4546 patients from 52 countries underwent appendectomy (2499 high-, 1540 middle-, and 507 low-HDI groups). Surgical site infection (SSI) rates were higher in low-HDI (OR 2.57, 95% CI 1.33-4.99, p = 0.005) but not middle-HDI countries (OR 1.38, 95% CI 0.76-2.52, p = 0.291), compared with high-HDI countries after adjustment. A laparoscopic approach was common in high-HDI countries (1693/2499, 67.7%), but infrequent in low-HDI (41/507, 8.1%) and middle-HDI (132/1540, 8.6%) groups. After accounting for case-mix, laparoscopy was still associated with fewer overall complications (OR 0.55, 95% CI 0.42-0.71, p < 0.001) and SSIs (OR 0.22, 95% CI 0.14-0.33, p < 0.001). In propensity-score matched groups within low-/middle-HDI countries, laparoscopy was still associated with fewer overall complications (OR 0.23 95% CI 0.11-0.44) and SSI (OR 0.21 95% CI 0.09-0.45). CONCLUSION: A laparoscopic approach is associated with better outcomes and availability appears to differ by country HDI. Despite the profound clinical, operational, and financial barriers to its widespread introduction, laparoscopy could significantly improve outcomes for patients in low-resource environments. TRIAL REGISTRATION: NCT02179112

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe

Quantitative aortography for assessment of aortic regurgitation in the era of percutaneous aortic valve replacement

Paravalvular leak (PVL) is a shortcoming that can erode the clinical benefits of transcatheter valve replacement (TAVR) and therefore a readily applicable method (aortography) to quantitate PVL objectively and accurately in the interventional suite is appealing to all operators. The ratio between the areas of the time-density curves in the aorta and left ventricular outflow tract (LVOT-AR) defines the regurgitation fraction (RF). This technique has been validated in a mock circulation; a single injection in diastole was further tested in porcine and ovine models. In the clinical setting, LVOT-AR was compared with trans-thoracic and trans-oesophageal echocardiography and cardiac magnetic resonance imaging. LVOT-AR &gt; 17% discriminates mild from moderate aortic regurgitation on echocardiography and confers a poor prognosis in multiple registries, and justifies balloon post-dilatation. The LVOT-AR differentiates the individual performances of many old and novel devices and is being used in ongoing randomized trials and registries

Mortality of emergency abdominal surgery in high-, middle- and low-income countries

Background: Surgical mortality data are collected routinely in high-income countries, yet virtually no low- or middle-income countries have outcome surveillance in place. The aim was prospectively to collect worldwide mortality data following emergency abdominal surgery, comparing findings across countries with a low, middle or high Human Development Index (HDI). Methods: This was a prospective, multicentre, cohort study. Self-selected hospitals performing emergency surgery submitted prespecified data for consecutive patients from at least one 2-week interval during July to December 2014. Postoperative mortality was analysed by hierarchical multivariable logistic regression. Results: Data were obtained for 10 745 patients from 357 centres in 58 countries; 6538 were from high-, 2889 from middle- and 1318 from low-HDI settings. The overall mortality rate was 1⋅6 per cent at 24 h (high 1⋅1 per cent, middle 1⋅9 per cent, low 3⋅4 per cent; P < 0⋅001), increasing to 5⋅4 per cent by 30 days (high 4⋅5 per cent, middle 6⋅0 per cent, low 8⋅6 per cent; P < 0⋅001). Of the 578 patients who died, 404 (69⋅9 per cent) did so between 24 h and 30 days following surgery (high 74⋅2 per cent, middle 68⋅8 per cent, low 60⋅5 per cent). After adjustment, 30-day mortality remained higher in middle-income (odds ratio (OR) 2⋅78, 95 per cent c.i. 1⋅84 to 4⋅20) and low-income (OR 2⋅97, 1⋅84 to 4⋅81) countries. Surgical safety checklist use was less frequent in low- and middle-income countries, but when used was associated with reduced mortality at 30 days. Conclusion: Mortality is three times higher in low- compared with high-HDI countries even when adjusted for prognostic factors. Patient safety factors may have an important role. Registration number: NCT02179112 (http://www.clinicaltrials.gov)