Anomalous behavior in an effective model of graphene with Coulomb interactions

We analyze by exact Renormalization Group (RG) methods the infrared properties of an effective model of graphene, in which two-dimensional massless Dirac fermions propagating with a velocity smaller than the speed of light interact with a three-dimensional quantum electromagnetic field. The fermionic correlation functions are written as series in the running coupling constants, with finite coefficients that admit explicit bounds at all orders. The implementation of Ward Identities in the RG scheme implies that the effective charges tend to a line of fixed points. At small momenta, the quasi-particle weight tends to zero and the effective Fermi velocity tends to a finite value. These limits are approached with a power law behavior characterized by non-universal critical exponents.Comment: 42 pages, 7 figures; minor corrections, one appendix added (Appendix A). To appear in Ann. Henri Poincar

Thromboembolic event rate in paroxysmal and persistent atrial fibrillation: Data from the GISSI-AF trial

BACKGROUND: Few data on the thromboembolic (TE) risk of paroxysmal and persistent atrial fibrillation (AF) are available. This study aimed to assess the incidence of TE events in paroxysmal and persistent AF. METHODS: We performed a subset post hoc analysis of 771 patients with paroxysmal and 463 with persistent AF enrolled in the multicenter, prospective, randomized, double-blind, placebo-controlled GISSI-AF trial - comparing the efficacy of valsartan versus placebo in preventing AF recurrences – where the choice of antithrombotic treatment was left to the judgment of the referring physician. TE and major outcome events were centrally validated. AF recurrences were detected by frequent clinic visits and a transtelephonic monitoring device with weekly and symptomatic transmissions. RESULTS: Eighty-five percent of patients had a history of hypertension, and the 7.7% had heart failure, left ventricular dysfunction, or both. The mean CHADS(2) score was 1.41±0.84. TE and major bleeding events were observed at a low incidence among the overall population at 1-year follow-up (0.97% and 0.81%, respectively). The univariate and multivariable analyses revealed no statistically significant differences in the incidence of TE, major bleeding events or mortality in paroxysmal and persistent AF patients. TE events were more common among women than men (p=0.02). The follow-up examination showed under- or overtreatment with warfarin in many patients, according to guideline suggestions. Warfarin was more frequently prescribed to patients with persistent AF (p<0.0001) and patients with AF recurrences (p<0.0001). AF recurrences were noninvasively detected in 632 (51.2%) patients. In patients without AF recurrences, the TE event rate was 0.5% versus 1.74%, 1.28%, and 1.18% for those with only symptomatic, only asymptomatic or both symptomatic and asymptomatic AF recurrences, respectively, but the difference was not statistically significant, even after adjusting for warfarin treatment and the CHADS(2) score (HR 2.93; CI 95%; 0.8-10.9; p=0.11). CONCLUSIONS: TE and major bleeding events showed a very low incidence in the GISSI-AF trial population, despite under- or overtreatment with warfarin in many patients. TE events had a similar rate in paroxysmal and persistent AF. TRIAL REGISTRATION: Trial registration number: NCT0037627

Declining clinical benefit of ICD in heart failure patients: Temporal trend of mortality outcomes from randomized controlled trials

The risk of sudden cardiac death in patients with heart failure has declined over time thanks to the sequential introduction of new treatments. However, current guidelines recommendations for implantable cardioverter-defibrillator (ICD) are based on randomized controlled trials (RCTs) carried out in the past three decades and their meta-analyses. To highlight potential changes over time in ICD clinical benefit in primary prevention of sudden cardiac death, we analyzed the temporal trends of RCT risk of mortality outcomes in this time frame

Heart Rate Turbulence Is a Powerful Predictor of Cardiac Death and Ventricular Arrhythmias in Postmyocardial Infarction and Heart Failure Patients: A Systematic Review and Meta-Analysis

Background—Heart rate turbulence (HRT) has been proposed as a candidate marker of altered autonomic tone, and some studies showed its prognostic value for both cardiac death (CD) and sudden death. Nevertheless, HRT is not currently used in the clinical practice. Methods and Results—We performed a systematic review and meta-analysis of the predictive value of HRT for the end points of total mortality, CD, and fatal and nonfatal ventricular arrhythmias in postacute myocardial infarction and heart failure patients. MEDLINE and The Cochrane Library databases were systematically searched to identify studies, which analyzed the predictive value of abnormal HRT for the defined end points. Twenty studies (25 cohorts: 12 832 patients) were identified by the systematic review, and 15 studies (20 cohorts: 11 499 patients) were included in the meta-analyses. Abnormal HRT was a predictive marker for all the end points in heart failure patients and more markedly in postacute myocardial infarction patients, where 9 out of the 10 cohorts had an ejection fraction >30%. In postacute myocardial infarction patients, HRT had pooled risk ratios of 3.53 (95% confidence interval [CI], 2.54–4.90), 4.82 (95% CI, 3.12– 7.45), and 4.48 (95% CI, 3.04–6.60), and positive likelihood ratios of 3.5 (95% CI, 2.6–4.8), 4.1 (95% CI, 3.0–5.7), and 2.7 (95% CI, 2.2–3.3) for total mortality, CD, and arrhythmic events, respectively. The combination of abnormal HRT and T-wave alternans (5 cohorts: 1516 patients) increased the predictive power for CD and arrhythmic events. Conclusions—HRT is a powerful predictor of both CD and arrhythmic events, particularly in postacute myocardial infarction patients with ejection fraction >30%. HRT power increases in combination with T-wave alternans analysis

Ventricular tachycardia-inducibility predicts arrhythmic events in post-myocardial infarction patients with low ejection fraction. A systematic review and meta-analysis

Background: Inducibility of ventricular arrhythmias at electrophysiological study (EPS) has long been suggested as predictive for subsequent arrhythmic events. Nevertheless, the usefulness of EPS in the clinical practice is still unclear. We performed a systematic review and meta-analysis to assess the predictive power of EPS in primary prevention of ventricular arrhythmias in post-myocardial infarction (MI) patients with left ventricular dysfunction. Methods: MEDLINE and the Cochrane Library databases were systematically searched to identify studies, which analyzed EPS predictive value in post-MI patients with mean EF < 40% for the composite arrhythmic endpoint defined by: sudden cardiac death (SCD), aborted SCD, ventricular tachycardia (VT), ventricular fibrillation (VF), appropriate implantable cardioverter-defibrillator (ICD) interventions. Results: Nine studies, evaluating 3959 patients with 647 arrhythmic events, were included in the meta-analyses. EPS showed a strong predictive power for the arrhythmic endpoint with a pooled odds ratio (OR) of 4.00 (95% confidence interval [CI]: 2.30–6.96) in the whole set of studies, albeit a high level of heterogeneity among studies. EPS predictive power was higher in studies where VT-inducibility was tested (OR 6.52; 95% CI: 2.30–18.44; sensitivity 0.65, specificity 0.78, and negative predictive value 0.94), versus those assessing VT/VF-inducibility (OR 2.09; 95% CI: 1.34–3.26). VT-inducibility was predictive even when assessed within one month after MI (OR 7.85; 95% CI: 3.67–16.80). Conclusions: Inducibility of ventricular arrhythmias at EPS is a strong predictor of the arrhythmic endpoint in post-MI patients with impaired EF, particularly when VT-inducibility is tested. EPS could help selecting the patients who can mostly benefit from ICD therapy. Keywords: Arrhythmia inducibility, Clinical electrophysiology, Implantable cardioverter-defibrillator, Left ventricular dysfunction, Myocardial infarction, Sudden cardiac deat