Control of many electron states in semiconductor quantum dots by non-Abelian vector potentials

Adiabatic time evolution of degenerate eigenstates of a quantum system provides a means for controlling electronic states since mixing between degenerate levels generates a matrix Berry phase. In the presence of spin-orbit coupling in n-type semiconductor quantum dots the electron Hamiltonian is invariant under time reversal operation and the many body groundstate may be doubly degenerate. This double degeneracy can generate non-Abelian vector potentials when odd number of electrons are present. We find that the antisymmetry of many electron wavefunction has no effect on the matrix Berry phase. We have derived equations that allow one to investigate the effect of electron correlations by expressing the non-Abelian vector potentials for many electron system in terms of single electron non-Abelian vector potentials.Comment: minor changes included, accepted in Phys. Rev.

Temporal decline in defibrillation thresholds with an active pectoral lead system

AbstractOBJECTIVESThe objective of this study was to characterize temporal changes in defibrillation thresholds (DFTs) after implantation with an active pectoral, dual-coil transvenous lead system.BACKGROUNDVentricular DFTs rise over time when monophasic waveforms are used with non-thoracotomy lead systems. This effect is attenuated when biphasic waveforms are used with transvenous lead systems; however, significant increases in DFT still occur in a minority of patients. The long-term stability of DFTs with contemporary active pectoral lead systems is unknown.METHODSThis study was a prospective assessment of temporal changes in DFT using a uniform testing algorithm, shock polarity and dual-coil active pectoral lead system. Thresholds were measured at implantation, before discharge and at long-term follow-up (70 ± 40 weeks) in 50 patients.RESULTSThe DFTs were 9.2 ± 5.4 J at implantation, 8.3 ± 5.8 J before discharge and 6.9 ± 3.6 J at long-term follow-up (p < 0.01 by analysis of variance; p < 0.05 for long-term follow-up vs. at implantation or before discharge). The effect was most marked in a prespecified subgroup with high implant DFTs (≥15 J). No patient developed an inadequate safety margin (<9 J) during follow-up.CONCLUSIONSThe DFTs declined significantly after implantation with an active pectoral, dual-coil transvenous lead system, and no clinically significant increases in DFT were observed. Therefore, routine defibrillation testing may not be required during the first two years after implantation with this lead system, in the absence of a change in the cardiac substrate or treatment with antiarrhythmic drugs

Is CRT-D superior to CRT-P in patients with nonischemic cardiomyopathy?

Abstract Background Recent studies have questioned the role of implanted cardiac defibrillators (ICDs) in nonischemic cardiomyopathy (NICM). Cardiac resynchronization therapy (CRT) can be delivered by a pacemaker (CRT-P) or an ICD (CRT-D). This meta-analysis assessed the effect of CRT-P versus CRT-D on mortality in patients with NICM. Methods Databases were searched for studies reporting the effect of CRT on all-cause mortality in patients with nonischemic cardiomyopathy (Ovid MEDLINE, EMBASE, Scopus, Web of Science, Google Scholar, and EBSCO CINAHL). The primary endpoint was all-cause mortality. The minimum duration of follow-up required for inclusion was one year. The search was not restricted to time or publication status. Results The literature search identified 955 candidate studies, 15 studies and 22,763 patients were included. Mean follow-up was 53 months (17–100 months). CRT-D in NICM was associated with lower all-cause mortality (log HR − 0.169, SE 0.055; p = 0.002) compared to CRT-P. Heterogeneity: df = 15 (P 0.03), I2 = 43; test for overall effect: Z = − 3.043 (P = 0.002). Conclusion CRT-D in NICM was associated with lower all-cause mortality than CRT-P

Effects of GLP-1 Agonists on mortality and arrhythmias in patients with Type II diabetes

Background: Glucagon-like Peptide-1 Receptor Agonists (GLP-1 RA) are frequently used for the management of diabetes. The impact of GLP-1 RA on cardiovascular outcomes is unclear. We aim to assess the effect of GLP-1 RA on mortality, atrial and ventricular arrhythmias, and sudden cardiac death in patients with type II diabetes. Methods: We searched databases including Ovid MEDLINE, EMBASE, Scopus, Web of Science, Google Scholar and CINAHL, from inception to May 2022, for randomized controlled trials reporting the relationship between GLP-1 RA (including albiglutide, dulaglutide, exenatide, liraglutide, lixisenatide, and semaglutide) and mortality, atrial arrhythmias, and the combined incidence of ventricular arrhythmias and sudden cardiac death. The search was not restricted to time or publication status. Results: A total of 464 studies resulted from literature search, of which 44 studies, including 78,702 patients (41,800 GLP-1 agonists vs 36,902 control), were included. Follow up ranged from 52 to 208 weeks. GLP-1 RA were associated with lower risk of all-cause mortality (odds ratio 0.891, 95% confidence interval 0.837–0.949; P < 0.01) and reduced cardiovascular mortality (odds ratio 0.88, 95% confidence interval 0.881–0.954; P < 0.01). GLP-1 RA were not associated with increased risk of atrial (odds ratio 0.963, 95% confidence interval 0.869–1.066; P 0.46) or ventricular arrhythmias and sudden cardiac death (odds ratio 0.895, 95% confidence interval 0.706–1.135; P 0.36). Conclusion: GLP-1 RA are associated with decreased all-cause and cardiovascular mortality, and no increased risk of atrial and ventricular arrhythmias and sudden cardiac death