1,720,998 research outputs found
SEMI-MARKOV RELIABILITY-ANALYSIS OF ALTERNATING SYSTEMS IN A NUCLEAR-POWER-PLANT
No full textNuclear power plant operations that follow current testing and maintenance requirements sometimes result in inadvertent reactor trips, and operating staffs devote a significant amount of time and effort in complying with these requirements. Significant benefits could result from changes in current technical specifications. The benefits and impacts of changes in allowed outage times (AOTs) and surveillance test intervals (STIs) are evaluated for an alternative system that consists of multiple trains and whose operation is alternated train by train. Because of testing and AOT requirements, the alternating system exhibits semi-Markovian characteristics that change states in accordance with a Markov process but take an arbitrarily distributed amount of time between changes. The state probabilities are quantified by memorizing the necessary number of past state probabilities. Two measures of plant performance, namely, core damage probability and plant unavailability (reactor downtime), were calculated for the evaluation of AOT and STI. Results indicate that there is an optimal point that gives the lowest core damage probability and that the methodology developed in this study can be applied to existing alternating systems to evaluate accurately the various alternatives in the technical specifications
Automatic Sleep Stage Classification Based on Deep Learning for Multi-channel Signals
No full textSleep plays a crucial role in restoring physical and mental health, making it essential to monitor sleep patterns objectively. Polysomnography is a standard method used to classify sleep stages, but it tends to be costly and requires specialist involvement. In this respect, many automatic sleep classification algorithms have recently been developed through practical and easy-to-measure wearable devices. However, further research is needed on how to combine biosignals from multichannels with different sampling rates measured through wearable devices. In this study, we proposed a sleep stage classification algorithm in multi-channel signals using an electrocardiogram, accelerometer, and gyroscope. Specifically, convolutional neural networks were used to compare the sleep stage classification performance according to the sampling rate. In the 4-class sleep stage classification for the wake, light sleep, deep sleep, and rapid eye movement, an accuracy of 80.23%, an F1-score of 0.8097, and a kappa value of 0.6711 were achieved when the sampling rate was adjusted based on electrocardiogram. On the other hand, when the sampling rate was based on an accelerometer and gyroscope, the accuracy was 64.33%, the F1-score was 0.6389, and the kappa value was 0.4708 in the 4-class sleep stage classification. These results could provide great insight into developing a sleep stage classification model using multi-channel signals based on wearable devices, and would also be available in other applications such as sleep apnea
Combined epicardial and endocardial approach for redo radiofrequency catheter ablation in patients with persistent atrial fibrillation: a randomized clinical trial
No full textAIMS: An epicardial approach is an effective means to detect and eliminate residual potentials in non-transmural lesions created during prior endocardial ablation. We sought to determine the impact of a combined epicardial and endocardial approach compared with a conventional endocardial approach, on recurrence-free survival after redo ablation. METHODS AND RESULTS: Participants with recurred persistent atrial fibrillation after prior endocardial ablation were randomized (1:1) to undergo treatment with the combined approach (epicardial followed by endocardial ablation) for the treatment group or conventional approach (endocardial ablation only) for the control group. The primary outcome was the time to recurrence of atrial fibrillation or atrial tachycardia following a 90-day blanking period within 12 months after the procedure. The secondary safety outcome was the occurrence of procedure-related complications within 24 h after the procedure. Of 100 randomized participants median age, 59.0 [(interquartile range (IQR): 53.8-64.3] years, including 16% women, with one prior ablation (IQR: 1-1), 93 (93%) completed the trial. Events relevant to the primary outcome occurred in 16 patients in the treatment group and in 21 patients in the control group Kaplan-Meier estimator percentages, 32 vs. 42%; hazard ratio, 0.71 [95% confidence interval (CI): 0.37-1.37]. The periprocedural complication rate was lower in the treatment group [2 vs. 16%; odds ratio, 0.11 (95% CI: 0.00-0.87)] with similar achievement of the procedural endpoint in the two groups. CONCLUSION: In the redo procedure for persistent atrial fibrillation, the combined approach had no significant difference of recurrence-free survival and a lower procedural complication rate compared with the conventional approach
A THERMOSTABLE MUTATION LOCATED AT THE HYDROPHOBIC CORE OF ALPHA(1)-ANTITRYPSIN SUPPRESSES THE FOLDING DEFECT OF THE Z-TYPE VARIANT
No full textA thermostable mutation, F51L, at the hydrophobic core of human alpha(1)-antitrypsin (alpha(1)AT) increased the conformational stability of the molecule by decreasing the unfolding rate significantly without altering the refolding rate, The mutation specifically influenced the transition between the native state and a compact intermediate, which retained similar to 70% of the far-UV CD signal, but which had most of the fluorescence signal already de quenched. The mutant alpha(1)AT protein was more resistant than the wild-type protein to the insertion of the tetradecapeptide mimicking the sequence of the reactive center loop, indicating that the mutation increases the closing of the central beta-sheet, the A-sheet, in the native state. The F51L mutation enhanced the folding efficiency of the Z-type (E342K) genetic variation, which causes aggregation of the molecule in the liver. It has been shown previously that the aggregation of the Z protein occurs via loop sheet polymerization, in which the reactive center loop of one molecule is inserted into the opening of the A-sheet of another molecule. Our results strongly suggest that the hydrophobic core of alpha(1)AT regulates the opening-closing of the A-sheet and that certain genetic variations that cause opening of the A-sheet can be corrected by inserting an additional stable mutation into the hydrophobic core
Association of Depression with Atrial Fibrillation in South Korean Adults
No full textIMPORTANCE: The risk of atrial fibrillation (AF) in people with depression is not fully known. Depression is associated with sympathetic activation and emotional stress, which might increase the risk of new-onset AF. OBJECTIVE: To assess the incidence of new-onset AF in those with and without depression using data from a nationwide health care database. DESIGN, SETTING, AND PARTICIPANTS: This cohort study obtained data from the Korean National Health Insurance Service database and enrolled people who underwent a nationwide health checkup in 2009. People younger than 20 years and those with a history of heart valve surgery, previous diagnosis of mitral stenosis, or who were diagnosed with AF between January 1, 2002 and December 31, 2008 were excluded. The risk of new-onset AF (occurring between 2009 and 2018) was compared in people who were and were not diagnosed with depression within a year before the 2009 nationwide health checkup. Data were analyzed between August 1, 2020 and October 31, 2020. EXPOSURE: Previous diagnosis of depression. MAIN OUTCOMES AND MEASURES: Cumulative incidence and risk of new-onset AF between 2009 and 2018 in participants with and without depression. Kaplan-Meier analysis was conducted to assess incidence of AF, and Cox proportional hazards regression was used to calculate adjusted and unadjusted hazard ratios (HRs) and 95% CIs. RESULTS: A total of 5 031 222 individuals with a mean (SD) age of 46.99 (14.06) years (2 771 785 men [55.1%]) were included in the analysis; of these individuals, 148 882 (3.0%) had a diagnosis of depression in the year before the 2009 health checkup and 4 882 340 (97%) did not. People with depression vs those without depression were older (aged 56.7 vs 46.7 years) and more likely to be women (96 472 [64.8%] vs 2 162 965 [44.3%]). Prevalence of hypertension, diabetes, dyslipidemia, and heart failure was higher in the depression group. The cumulative incidence of new-onset AF was significantly higher in people with depression vs without depression in the Kaplan-Meier analysis and showed steady divergence throughout 10 years of follow-up (cumulative incidence, 4.44% vs 1.92%; log-rank P < .001). After adjusting for covariates, depression was associated with a 25.1% increased risk of new-onset AF (HR, 1.25; 95% CI, 1.22-1.29; P < .001). People with recurrent episodes of depression showed even higher risk of new-onset AF (HR, 1.32; 95% CI, 1.27-1.37; P < .001). Young age and female sex had significant interactions with depression, which suggests that young people and women with depression may have an increased risk of new-onset AF. CONCLUSIONS AND RELEVANCE: This study found that depression was associated with a significantly increased cumulative incidence and risk of new-onset AF. Recurrent episodes of depression were associated with even higher risk. These findings suggest the need for adequate screening for AF in people with depression, particularly in younger people and women
E/e’ Ratio Predicts the Atrial Pacing-Induced Left Atrial Pressure Response in Patients with Preserved Ejection Fraction
No full textBackground and Objectives: Left atrial hypertension is one of the pathophysiologies of heart failure with preserved ejection fraction. We hypothesized that left atrial pressure response (LAPR) to incremental pacing is higher in patients with atrial fibrillation (AF) and can predict left ventricular diastolic dysfunction. Materials and Methods: Patients requiring left atrial access as a part of a therapeutic procedure for AF (n = 204, AF group) or supraventricular tachycardia (n = 34, control group) were analyzed (male n = 183, 54 ± 12 years old). LAPR was measured during incremental pacing. Results: Baseline left atrial pressure and LAPR at all pacing rates were not different between the AF and control groups. They were higher in patients with a high E/e’ (≥ 8) than in those with a low E/e’ (<8). LAPR at a pacing interval of 400 ms and E/e’ were positively correlated (r = 0.373, p < 0.001). Body mass index and a high E/e’ were independent predictors of pacing-induced left atrial hypertension. Conclusions: LAPR to incremental pacing was constant regardless of AF. The non-invasive echocardiographic marker E/e’ reflected pacing-induced left atrial hypertension
Right bundle branch block–type wide QRS complex tachycardia with a reversed R/S complex in lead V6: Development and validation of electrocardiographic differentiation criteria
No full textBackground: Differentiation of supraventricular tachycardia (SVT) with a right bundle branch block (RBBB) pattern from ventricular tachycardia (VT) is difficult, particularly when the R/S ratio in lead V6 is below 1.0. Objective: We sought to investigate the electrocardiographic criteria for distinguishing between these arrhythmias. Methods: We investigated electrocardiographic parameters from 111 consecutive patients who had RBBB pattern wide QRS complex tachycardia with a reversed R/S ratio in lead V6 (72 VTs, 39 SVTs). Diagnostic criteria from the previous algorithms were compared with our new criterion, the RS/QRS ratio, which was defined as the ratio of the interval from the onset of the QRS complex to the nadir of the S wave, divided by the QRS width in lead V6. The RS/QRS ratio was further tested in a prospective population (31 fascicular VTs, 29 SVTs). Results: The diagnostic accuracy of previous criteria (Brugada algorithm, Vereckei algorithm, and R-wave peak time criterion) was only modest. However, the RS/QRS ratio in lead V6 was significantly lower in SVT than in VT (0.36 ± 0.04 vs 0.50 ± 0.08; P < .001). A cutoff value of the RS/QRS ratio >0.41 differentiated VT from SVT with a high diagnostic accuracy (sensitivity 97.2%; specificity 89.7%). When tested in a prospective population with fascicular VT, the diagnostic accuracy of the criteria was maintained (sensitivity 90.3%; specificity 86.2%). Conclusion: The RS/QRS ratio >0.41 in lead V6 is a simple and reliable index for distinguishing VT from SVT in RBBB pattern wide QRS complex tachycardia with a reversed R/S complex in lead V6. This criterion was particularly useful for the differential diagnosis of fascicular VT from RBBB pattern SVT
The impact of personal thoracic impedance on electrical cardioversion in patients with atrial arrhythmias
Full text linkBackground and Objectives—Direct current cardioversion (DCCV) is a safe and useful treatment for atrial tachyarrhythmias. In the past, the energy delivered in DCCV was decided upon empirically, based only on the type of tachyarrhythmia. This conventional method does not consider individual factors and may lead to unnecessary electrical damage. Materials and Methods— We performed DCCV in patients with atrial tachyarrhythmias. The impedance and electrical current at the moment of shock were measured. The human thoracic impedance between both defib-rillator patches and the electric current that was used were measured. Results—A total of 683 DCCVs were performed on 466 atrial tachyarrhythmia patients. The average impedance was 64 ± 11 Ω and the average successful current was 23 ± 6 mA. The magnitude of the electrical current that was successful depended upon the human impedance (linear regression, B = −0.266, p < 0.001) and the left atrial diameter (B = 0.092, p < 0.001). Impedance was directly proportional to body mass index (BMI) (B = 1.598, p < 0.001) and was higher in females than in males (77 ± 15 Ω vs. 63 ± 11 Ω, p < 0.001). Notably, the high-impedance (>70 Ω) group had a higher BMI (27 ± 4 kg/m2 vs. 25 ± 3 kg/m2, p < 0.001) and a higher proportion of females (37% vs. 9%, p < 0.001) than the low-impedance group (<70 Ω). However, thoracic impedance was not an independent predictor for successful DCCV. Con-clusions—Human thoracic impedance was one of the factors that impacted the level of electrical current required for successful DCCV in patients with atrial arrhythmias. In the future, it will be helpful to consider individual predictors, such as BMI and gender, to minimize electrical damage during DCCV
A novel predictive model for late recurrence after catheter ablation for atrial fibrillation using left appendage volume measured by cardiac computed tomography
No full textLarger left atrial appendage (LAA) volume is associated with a higher risk of late recurrence (LR) in patients undergoing radiofrequency catheter ablation (RFCA) for atrial fibrillation (AF). However, it is unclear whether LAA volume predicts LR, independent of established risk factors. We sought to evaluate the value of LAA volume in predicting LR after RFCA for AF and to develop a score prediction model including LAA volume for these patients.We retrospectively studied 992 patients who underwent RFCA for AF and cardiac computed tomography before RFCA at a single center.At 3 years after RFCA, 362 patients (36.5 %) experienced recurrence. The multivariate Cox regression model showed that age ≥ 75 years (10 points), non-paroxysmal AF (9 points), diabetes mellitus (4 points), left atrial volume index (1 point per 10 ml/m2 rounded to the nearest integer), and the second (4.7 to < 7 ml/m2; 4 points) and third (≥ 7 ml/m2; 5 points) tertiles of the LAA volume index were independent risk factors LR. The above-mentioned risk factors were included in the integrated score model, and the C-index of the proposed score model was 0.715 (95 % confidence interval [CI] 0.679–0.752).LAA volume is an independent predictor of LR and the predictive model including LAA volume showed good discrimination power. These findings provide evidence for the inclusion of LAA volume in the risk stratification for AF recurrence in patients undergoing RFCA for AF
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