Estimation of spectral parameters of residual ECG signal during atrial fibrillation using autoregressive models

The application of AutoRegressive (AR) models to extract spectral parameters from residual ECG (rECG) signals is exploited. In particular, a new method based on AR spectra is employed to estimate the dominant atrial cycle length (DACL) on ECG obtained from patients undergoing episodes of atrial fibrillation (AF). The traditional FFT-based spectral approach will be compared with the new method. Potentialities and possible superior performances of AR spectra are documented and discussed

Estimation of spectral parameters of residual ECG signal during atrial fibrillation using autoregressive models

The application of AutoRegressive (AR) models to extract spectral parameters from residual ECG (rECG) signals is exploited. In particular, a new method based on AR spectra is employed to estimate the dominant atrial cycle length (DACL) on ECG obtained from patients undergoing episodes of atrial fibrillation (AF). The traditional FFT-based spectral approach will be compared with the new method. Potentialities and possible superior performances of AR spectra are documented and discussed

Different circadian behavior of the apex and the end of the T wave

International audienc

Cardiac effects of chronic oral beta-blockade: Lack of agreement between heart rate and QT interval changes.

A

Ventricular repolarisation and holter monitoring: role of sympathetic blockade on the physiology of the QT/RR ratio

Circadian variations of the QT interval and its heart rate dependency have been established. However, the respective roles of the sympathetic and parasympathetic nervous systems in their regulation are still undetermined. Eighteen healthy volunteers (average age 39 +/- 7 years, 10 men) were recruited and selected randomly to receive either placebo or atenolol (100 mg/day). The treatments were crossed after 7 days. The rate dependency of the QT was assessed by day and by night by 24 hour Holter ECG monitoring. The effects of atenolol on the rate dependency of the QT interval depend on the time of day. During the daytime, the QT rate dependency was reduced by atenolol (0.180 (0.162: 0.198) versus 0.216 (0.195: 0.236) with placebo, p< 0.01) whereas during the night, the QT rate dependency was the same in both groups. Therefore, the betablocker is associated with an inversion of the daily modulation of the QT fate dependency. The daytime rate-dependency of the QT interval in decreased with betablocker therapy. This result suggests a direct or indirect influence of the sympathetic nervous system on the rate dependency of ventricular repolarisation

Time- and rate-dependent alterations of the QT interval precede the onset of torsade de pointes in patients with acquired QT prolongation

abstract: Objectives: Background: Methods: Results: Conclusions: The purpose of this study was to determine whether the QT interval dynamics that precede torsade de pointes are consistent with the initiation of this arrhythmia by early afterdepolarization-induced triggered activity.Early afterdepolarization-induced triggered activity has been suggested as an electrophysiologic mechanism for torsade de pointes. Consequently, the initiation of torsade de pointes should involve time- and rate-dependent alterations of ventricular repolarization similar to those known to modulate the development of early afterdepolarizations.RR and QT intervals were measured in digitized 24-h ambulatory electrocardiographic recordings obtained from seven patients with acquired prolongation of ventricular repolarization. Each patient had one or more episodes of torsade de pointes. The relation between RR and QT intervals was determined before, during and after multiple episodes of torsade de pointes.In patients with multiple episodes of ventricular arrhythmias, the onset of the arrhythmias was associated with a critical prolongation of the QT interval. In some episodes, prolongation of the QT interval was associated with sudden prolongation of the sinus cycle length, whereas in other episodes, the QT interval prolonged progressively at a constant cycle length.The association between a critically prolonged QT interval and the onset of ventricular arrhythmias suggests that the initial complex of torsade de pointes is an early afterdepolarization-induced triggered response. However, prolongation of the QT interval itself was not sufficient to account for the initiation of torsade de pointes, suggesting that other, as yet unidentified factors are required

Diagnostic performance of QT interval variables from 24-h electrocardiography in the long QT syndrome

International audienceThe long QT syndrome is mainly defined by QT interval prolongation (QTc > 0.44s). However, data obtained in genotyped patients showed that resting QTc measurement alone may be inaccurate for ascertaining the phenotype. The aim of this study was to evaluate the diagnostic performance of QT interval rate-dependence in untreated chromosome 11-linked patients

A randomized, double-blind, placebo-controlled trial assessing the efficacy of S66913 in patients with paroxysmal atrial fibrillation

Anti-arrhythmic drugs (AAD) for the treatment of atrial fibrillation (AF) are associated with limited efficacy and adverse effects. Inhibition of the atrial current IKur, absent from the ventricle, is expected to be antiarrhythmic, without adverse cardiac effects, particularly ventricular pro-arrhythmic effects.A randomized clinical trial in symptomatic paroxysmal AF patients being considered for ablation. The primary endpoint was AF burden (AFB) as measured by insertable continuous monitoring (ICM) devices. Screened patients had an ICM implanted and were included if AFB was between 1-70% after 4 weeks of recording. They were randomly allocated to 4-week treatment of a selective IKur inhibitor S66913 (5 mg, 25 mg, or 100 mg orally per day) or placebo. The study was to enroll 160 patients.The study was terminated prematurely, due to non-study related preclinical safety concerns, after 58 patients had been enrolled. The median AFB ranged from 4.3% to 10.3% at baseline in the 4 treatment groups. S66913 had no significant effect on AFB or on AFB plus atrial tachycardia (AT) burden, at any dosage; nor on any secondary endpoints including the number and duration of AT or AF episodes, and symptoms. The drug was well tolerated with no safety concern during the treatment or the extended clinical follow-up.DIAGRAF-IKUR was the first study to show that using ICM to assess the effect of an AAD is feasible. The selective IKur inhibitor S66913 was safe but had no clinically meaningful effect at the time of early termination of the study.A. John Camm, Paul Dorian, Stefan H. Hohnloser, Peter R. Kowey, Benoît Tyl, Yongbin Ni, Victoria Vandzhura, Pierre Maison-Blanche, Mirko de Melis, and Prashanthan Sanders, for the DIAGRAF-IKUR study investigator