A study on stability analysis of atrial repolarization variability using ARX model in sinus rhythm and atrial tachycardia ECGs

© 2016 Elsevier Ireland Ltd Background The interaction between the PTa and PP interval dynamics from the surface ECG is seldom explained. Mathematical modeling of these intervals is of interest in finding the relationship between the heart rate and repolarization variability. Objective The goal of this paper is to assess the bounded input bounded output (BIBO) stability in PTa interval (PTaI) dynamics using autoregressive exogenous (ARX) model and to investigate the reason for causing instability in the atrial repolarization process. Methods Twenty-five male subjects in normal sinus rhythm (NSR) and ten male subjects experiencing atrial tachycardia (AT) were included in this study. Five minute long, modified limb lead (MLL) ECGs were recorded with an EDAN SE-1010 PC ECG system. The number of minute ECGs with unstable segments (N us ) and the frequency of premature activation (PA) (i.e. atrial activation) were counted for each ECG recording and compared between AT and NSR subjects. Results The instability in PTaI dynamics was quantified by measuring the numbers of unstable segments in ECG data for each subject. The unstable segments in the PTaI dynamics were associated with the frequency of PA. The presence of PA is not the only factor causing the instability in PTaI dynamics in NSR subjects, and it is found that the cause of instability is mainly due to the heart rate variability (HRV). C onclusion The ARX model showed better prediction of PTa interval dynamics in both groups. The frequency of PA is significantly higher in AT patients than NSR subjects. A more complex model is needed to better identify and characterize healthy heart dynamics

Laparoscopic versus open gastrectomy for gastric cancer

BACKGROUND: Gastric cancer is the third most common cause of cancer-related mortality in the world. Currently there are two surgical options for potentially curable patients (i.e. people with non-metastatic gastric cancer), laparoscopic and open gastrectomy. However, it is not clear whether one of these options is superior. OBJECTIVES: To assess the benefits and harms of laparoscopic gastrectomy or laparoscopy-assisted gastrectomy versus open gastrectomy for people with gastric cancer. In particular, we planned to investigate the effects by patient groups, such as cancer stage, anaesthetic risk, and body mass index (BMI), and by intervention methods, such as method of anastomosis, type of gastrectomy and laparoscopic or laparoscopically-assisted gastrectomy. Search methods We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Science Citation Index, ClinicalTrials.gov and the WHO ICTRP (World Health Organization International Clinical Trials Registry Platform) until September 2015. We also screened reference lists from included trials. SELECTION CRITERIA: Two review authors independently selected references for further assessment by going through all titles and abstracts. Further selection was based on review of full text articles for selected references. Data collection and analysis Two review authors independently extracted study data. We calculated the risk ratio (RR) with 95% confidence interval (CI) for binary outcomes, the mean difference (MD) or the standardised mean difference (SMD) with 95% CI for continuous outcomes and the hazard ratio (HR) for time-to-event outcomes. We performed meta-analyses where it was meaningful. MAIN RESULTS: In total, 2794 participants were randomised in 13 trials included in this review. All the trials were at unclear or high risk of bias. One trial (which included 53 participants) did not contribute any data to this review. A total of 213 participants were excluded in the remaining trials after randomisation, leaving a total of 2528 randomised participants for analysis, with 1288 undergoing laparoscopic gastrectomy and 1240 undergoing open gastrectomy. All the participants were suitable for major surgery. There was no difference in the proportion of participants who died within thirty days of treatment between laparoscopic gastrectomy (7/1188: adjusted proportion = 0.6% (based on meta-analysis)) and open gastrectomy (4/1447: 0.3%) (RR 1.60, 95% CI 0.50 to 5.10; risk difference 0.00, 95% CI -0.01 to 0.01; participants = 2335; studies = 11; I2 = 0%; low quality evidence). There were no events in either group for short-term recurrence (participants = 103; studies = 3), proportion requiring blood transfusion (participants = 66; studies = 2), and proportion with positive margins at histopathology (participants = 28; studies = 1). None of the trials reported health-related quality of life, time to return to normal activity or time to return to work. The differences in long-term mortality (HR 0.94, 95% CI 0.70 to 1.25; participants = 195; studies = 3; I2 = 0%; very low quality evidence), serious adverse events within three months (laparoscopic gastrectomy (7/216: adjusted proportion = 3.6%) versus open gastrectomy (13/216: 6%) (RR 0.60, 95% CI 0.27 to 1.34; participants = 432; studies = 8; I2 = 0%; very low quality evidence), long-term recurrence (HR 0.95, 95% CI 0.70 to 1.30; participants = 162; studies = 4; very low quality evidence), adverse events within three months (laparoscopic gastrectomy (204/268: adjusted proportion = 16.1%) versus open gastrectomy (253/1222: 20.7%) (RR 0.78, 95% CI 0.60 to 1.01; participants = 2490; studies = 11; I2 = 38%; very low quality evidence), quantity of perioperative blood transfused (SMD 0.05, 95% CI -0.27 to 0.38; participants = 143; studies = 2; I2 = 0%; very low quality evidence), length of hospital stay (MD -1.82 days, 95% CI -3.72 to 0.07; participants = 319; studies = 6; I2 = 83%; very low quality evidence), and number of lymph nodes harvested (MD -0.63, 95% CI -1.51 to 0.25; participants = 472; studies = 9; I2 = 40%; very low quality evidence) were imprecise. There was no alteration in the interpretation of the results in any of the subgroups. AUTHORS' CONCLUSIONS: Based on low quality evidence, there is no difference in short-term mortality between laparoscopic and open gastrectomy. Based on very low quality evidence, there is no evidence for any differences in short-term or long-term outcomes between laparoscopic and open gastrectomy. However, the data are sparse, and the confidence intervals were wide, suggesting that significant benefits or harms of laparoscopic gastrectomy cannot be ruled out. Several trials are currently being conducted and interim results of these trials have been included in this review. These trials need to perform intention-to-treat analysis to ensure that the results are reliable and report the results according to the CONSORT Statement

Non-surgical versus surgical treatment for oesophageal cancer

BACKGROUND: Oesophageal cancer is the sixth most common cause of cancer-related mortality in the world. Currently surgery is the recommended treatment modality when possible. However, it is unclear whether non-surgical treatment options is equivalent to oesophagectomy in terms of survival. OBJECTIVES: To assess the benefits and harms of non-surgical treatment versus oesophagectomy for people with oesophageal cancer. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Science Citation Index, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) up to 4th March 2016. We also screened reference lists of included studies. Selection criteria Two review authors independently screened all titles and abstracts of articles obtained from the literature searches and selected references for further assessment. For these selected references, we based trial inclusion on assessment of the full-text articles. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted study data. We calculated the risk ratio (RR) with 95% confidence interval (CI) for binary outcomes, the mean difference (MD) or the standardised mean difference (SMD) with 95% CI for continuous outcomes, and the hazard ratio (HR) for time-to-event outcomes. We performed meta-analyses where it was meaningful. MAIN RESULTS Eight trials, which included 1132 participants in total, met the inclusion criteria of this Cochrane review. These trials were at high risk of bias trials. One trial (which included five participants) did not contribute any data to this Cochrane review, and we excluded 13 participants in the remaining trials after randomisation; this left a total of 1114 participants, 510 randomised to non-surgical treatment and 604 to surgical treatment for analysis. The non-surgical treatment was definitive chemoradiotherapy in five trials and definitive radiotherapy in three trials. All participants were suitable for major surgery. Most of the data were from trials that compared chemoradiotherapy with surgery. There was no difference in long-term mortality between chemoradiotherapy and surgery (HR 0.88, 95% CI 0.76 to 1.03; 602 participants; four studies; low quality evidence). The long-term mortality was higher in radiotherapy than surgery (HR 1.39, 95% CI 1.18 to 1.64; 512 participants; three studies; very low quality evidence). There was no difference in long-term recurrence between non-surgical treatment and surgery (HR 0.96, 95% CI 0.80 to 1.16; 349 participants; two studies; low quality evidence). The difference between non-surgical and surgical treatments was imprecise for short-term mortality (RR 0.39, 95% CI 0.11 to 1.35; 689 participants; five studies; very low quality evidence), the proportion of participants with serious adverse in three months (RR 0.61, 95% CI 0.25 to 1.47; 80 participants; one study; very low quality evidence), and proportion of people with local recurrence at maximal follow-up (RR 0.89, 95% CI 0.70 to 1.12; 449 participants; three studies; very low quality evidence). The health-related quality of life was higher in non-surgical treatment between four weeks and three months after treatment (Spitzer Quality of Life Index; MD 0.93, 95% CI 0.24 to 1.62; 165 participants; one study; very low quality evidence). The difference between non-surgical and surgical treatments was imprecise for medium-term health-related quality of life (three months to two years after treatment) (Spitzer Quality of Life Index; MD −0.95, 95% CI −2.10 to 0.20; 62 participants; one study; very low quality of evidence). The proportion of people with dysphagia at the last follow-up visit prior to death was higher with definitive chemoradiotherapy compared to surgical treatment (RR 1.48, 95% CI 1.01 to 2.19; 139 participants; one study; very low quality evidence). AUTHORS' CONCLUSIONS Based on low quality evidence, chemoradiotherapy appears to be at least equivalent to surgery in terms of short-term and long-term survival in people with oesophageal cancer (squamous cell carcinoma type) who are fit for surgery and are responsive to induction chemoradiotherapy. However, there is uncertainty in the comparison of definitive chemoradiotherapy versus surgery for oesophageal cancer (adenocarcinoma type) and we cannot rule out significant benefits or harms of definitive chemoradiotherapy versus surgery. Based on very low quality evidence, the proportion of people with dysphagia at the last follow-up visit prior to death was higher with definitive chemoradiotherapy compared to surgery. Based on very low quality evidence, radiotherapy results in less long-term survival than surgery in people with oesophageal cancer who are fit for surgery. However, there is a risk of bias and random errors in these results, although the risk of bias in the studies included in this systematic review is likely to be lower than in non-randomised studies. Further trials at low risk of bias are necessary. Such trials need to compare endoscopic treatment with surgical treatment in early stage oesophageal cancer (carcinoma in situ and Stage Ia), and definitive chemoradiotherapy with surgical treatments in other stages of oesophageal cancer, and should measure and report patient-oriented outcomes. Early identification of responders to chemoradiotherapy and better second-line treatment for non-responders will also increase the need and acceptability of trials that compare definitive chemoradiotherapy with surgery

Subunit-Selective Interrogation of CO Recombination in Carbonmonoxy Hemoglobin by Isotope-Edited Time-Resolved Resonance Raman Spectroscopy

Hemoglobin (Hb) is an allosteric tetrameric protein made up of αβ heterodimers. The α and β chains are similar, but are chemically and structurally distinct. To investigate dynamical differences between the chains, we have prepared tetramers in which the chains are isotopically distinguishable, via reconstitution with 15N-heme. Ligand recombination and heme structural evolution, following HbCO dissociation, was monitored with chain selectivity by resonance Raman (RR) spectroscopy. For α but not for β chains, the frequency of the ν4 porphyrin breathing mode increased on the microsecond time scale. This increase is a manifestation of proximal tension in the Hb T-state, and its time course is parallel to the formation of T contacts, as determined previously by UVRR spectroscopy. Despite the localization of proximal constraint in the α chains, geminate recombination was found to be equally probable in the two chains, with yields of 39 ± 2%. We discuss the possibility that this equivalence is coincidental, in the sense that it arises from the evolutionary pressure for cooperativity, or that it reflects mechanical coupling across the αβ interface, evidence for which has emerged from UVRR studies of site mutants

Comparative safety and efficacy of vasopressors for mortality in septic shock: A network meta-analysis

© 2015, © The Intensive Care Society 2015.Introduction: Septic shock is a life-threatening condition requiring vasopressor agents to support the circulatory system. Several agents exist with choice typically guided by the specific clinical scenario. We used a network meta-analysis approach to rate the comparative efficacy and safety of vasopressors for mortality and arrhythmia incidence in septic shock patients. Methods: We performed a comprehensive electronic database search including Medline, Embase, Science Citation Index Expanded and the Cochrane database. Randomised trials investigating vasopressor agents in septic shock patients and specifically assessing 28-day mortality or arrhythmia incidence were included. A Bayesian network meta-analysis was performed using Markov chain Monte Carlo methods. Results: Thirteen trials of low to moderate risk of bias in which 3146 patients were randomised were included. There was no pairwise evidence to suggest one agent was superior over another for mortality. In the network meta-analysis, vasopressin was significantly superior to dopamine (OR 0.68 (95% CI 0.5 to 0.94)) for mortality. For arrhythmia incidence, standard pairwise meta-analyses confirmed that dopamine led to a higher incidence of arrhythmias than norepinephrine (OR 2.69 (95% CI 2.08 to 3.47)). In the network meta-analysis, there was no evidence of superiority of one agent over another. Conclusions: In this network meta-analysis, vasopressin was superior to dopamine for 28-day mortality in septic shock. Existing pairwise information supports the use of norepinephrine over dopamine. Our findings suggest that dopamine should be avoided in patients with septic shock and that other vasopressor agents should continue to be based on existing guidelines and clinical judgement of the specific presentation of the patient

A Survey on Adaptation Strategies for Mutation and Crossover Rates of Differential Evolution Algorithm

Differential Evolution (DE), the well-known optimization algorithm, is a tool under the roof of Evolutionary Algorithms (EAs) for solving non-linear and non-differential optimization problems. DE has many qualities in its hand, which are attributing to its popularity. DE also is known for its simplicity in solving the given problem with few control parameters: the population size (NP), the mutation rate (F) and the crossover rate (Cr). To avoid the difficulty involved in setting of suitable values for NP, F and Cr many parameter adaptation strategies are proposed in the literature. This paper is to present the working principle of the parameter adaptation strategies of F and Cr. The adaptation strategies are categorized based on the logic used by the authors, and clear insights about all the categories are presented

Laparoscopic versus open transhiatal oesophagectomy for oesophageal cancer

Surgery is the preferred treatment for resectable oesophageal cancers, and can be performed in different ways. Transhiatal oesophagectomy (oesophagectomy without thoracotomy, with a cervical anastomosis) is one way to resect oesophageal cancers. It can be performed laparoscopically or by open method. With other organs, laparoscopic surgery has been shown to reduce complications and length of hospital stay compared to open surgery. However, concerns remain about the safety of laparoscopic transhiatal oesophagectomy in terms of post-operative complications and oncological clearance compared with open transhiatal oesophagectomy

Diagnostic accuracy of different imaging modalities following computed tomography (CT) scanning for assessing the resectability with curative intent in pancreatic and periampullary cancer

BACKGROUND: Periampullary cancer includes cancer of the head and neck of the pancreas, cancer of the distal end of the bile duct, cancer of the ampulla of Vater, and cancer of the second part of the duodenum. Surgical resection is the only established potentially curative treatment for pancreatic and periampullary cancer. A considerable proportion of patients undergo unnecessary laparotomy because of underestimation of the extent of the cancer on computed tomography (CT) scanning. Other imaging methods such as magnetic resonance imaging (MRI), positron emission tomography (PET), PET-CT, and endoscopic ultrasound (EUS) have been used to detect local invasion or distant metastases not visualised on CT scanning which could prevent unnecessary laparotomy. No systematic review or meta-analysis has examined the role of different imaging modalities in assessing the resectability with curative intent in patients with pancreatic and periampullary cancer. OBJECTIVES: To determine the diagnostic accuracy of MRI, PET scan, and EUS performed as an add-on test or PET-CT as a replacement test to CT scanning in detecting curative resectability in pancreatic and periampullary cancer. SEARCH METHODS: We searched MEDLINE, Embase, Science Citation Index Expanded, and Health Technology Assessment (HTA) databases up to 5 November 2015. Two review authors independently screened the references and selected the studies for inclusion. We also searched for articles related to the included studies by performing the "related search" function in MEDLINE (OvidSP) and Embase (OvidSP) and a "citing reference" search (by searching the articles that cite the included articles). SELECTION CRITERIA: We included diagnostic accuracy studies of MRI, PET scan, PET-CT, and EUS in patients with potentially resectable pancreatic and periampullary cancer on CT scan. We accepted any criteria of resectability used in the studies. We included studies irrespective of language, publication status, or study design (prospective or retrospective). We excluded case-control studies. DATA COLLECTION AND ANALYSIS: Two review authors independently performed data extraction and quality assessment using the QUADAS-2 (quality assessment of diagnostic accuracy studies - 2) tool. Although we planned to use bivariate methods for analysis of sensitivities and specificities, we were able to fit only the univariate fixed-effect models for both sensitivity and specificity because of the paucity of data. We calculated the probability of unresectability in patients who had a positive index test (post-test probability of unresectability in people with a positive test result) and in those with negative index test (post-test probability of unresectability in people with a positive test result) using the mean probability of unresectability (pre-test probability) from the included studies and the positive and negative likelihood ratios derived from the model. The difference between the pre-test and post-test probabilities gave the overall added value of the index test compared to the standard practice of CT scan staging alone. MAIN RESULTS: Only two studies (34 participants) met the inclusion criteria of this systematic review. Both studies evaluated the diagnostic test accuracy of EUS in assessing the resectability with curative intent in pancreatic cancers. There was low concerns about applicability for most domains in both studies. The overall risk of bias was low in one study and unclear or high in the second study. The mean probability of unresectable disease after CT scan across studies was 60.5% (that is 61 out of 100 patients who had resectable cancer after CT scan had unresectable disease on laparotomy). The summary estimate of sensitivity of EUS for unresectability was 0.87 (95% confidence interval (CI) 0.54 to 0.97) and the summary estimate of specificity for unresectability was 0.80 (95% CI 0.40 to 0.96). The positive likelihood ratio and negative likelihood ratio were 4.3 (95% CI 1.0 to 18.6) and 0.2 (95% CI 0.0 to 0.8) respectively. At the mean pre-test probability of 60.5%, the post-test probability of unresectable disease for people with a positive EUS (EUS indicating unresectability) was 86.9% (95% CI 60.9% to 96.6%) and the post-test probability of unresectable disease for people with a negative EUS (EUS indicating resectability) was 20.0% (5.1% to 53.7%). This means that 13% of people (95% CI 3% to 39%) with positive EUS have potentially resectable cancer and 20% (5% to 53%) of people with negative EUS have unresectable cancer. AUTHORS' CONCLUSIONS: Based on two small studies, there is significant uncertainty in the utility of EUS in people with pancreatic cancer found to have resectable disease on CT scan. No studies have assessed the utility of EUS in people with periampullary cancer.There is no evidence to suggest that it should be performed routinely in people with pancreatic cancer or periampullary cancer found to have resectable disease on CT scan