Pathophysiology of atrial fibrillation: Focal patterns of activation.

For decades, electrical activity recorded has been investigated to unravel pathophysiology of cardiac arrhythmias, such as atrial fibrillation (AF). Particularly high-resolution mapping studies have significantly contributed to novel insights into AF mechanisms. From these mapping studies, it appeared that persistence of AF is associated with a high incidence of focal patterns of activation.

Spatial distribution of conduction disorders during sinus rhythm.

Background: Length of lines of conduction block (CB) during sinus rhythm (SR) at Bachmann's bundle (BB) is associated with atrial fibrillation (AF). However, it is unknown whether extensiveness of CB at BB represents CB elsewhere in the atria. We aim to investigate during SR 1) the spatial distribution and extensiveness of CB 2) whether there is a predilection site for CB and 3) the association between CB and incidence of post-operative AF.

Relevance of Conduction Disorders in Bachmann's Bundle During Sinus Rhythm in Humans.

Background: Bachmann's bundle (BB) is considered to be the main route of interatrial conduction and to play a role in development of atrial fibrillation (AF). The goals of this study are to characterize the presence of conduction disorders in BB during sinus rhythm and to study their relation with AF.

Methods And Results: High-resolution epicardial mapping (192 unipolar electrodes, interelectrode distance: 2 mm) of sinus rhythm was performed in 185 patients during coronary artery bypass surgery of whom 13 had a history of paroxysmal AF.

Dynamics of Endo- and Epicardial Focal Fibrillation Waves at the Right Atrium in a Patient With Advanced Atrial Remodelling.

Focal waves appear frequently at the epicardium during persistent atrial fibrillation (AF), however, the origin of these waves is under debate. We performed simultaneous endo-epicardial mapping of the right atrial wall during longstanding persistent AF in a patient undergoing cardiac surgery. During 10 seconds 53 and 59 focal waves appeared at random at respectively the endocardium and epicardium.

QUest for the Arrhythmogenic Substrate of Atrial fibRillation in Patients Undergoing Cardiac Surgery (QUASAR Study): Rationale and Design.

The heterogeneous presentation and progression of atrial fibrillation (AF) implicate the existence of different pathophysiological processes. Individualized diagnosis and therapy of the arrhythmogenic substrate underlying AF may be required to improve treatment outcomes. Therefore, this single-center study aims to identify the arrhythmogenic areas underlying AF by intra-operative, high-resolution, multi-site epicardial mapping in 600 patients with different heart diseases.

Dynamics of Focal Fibrillation Waves during Persistent Atrial Fibrillation.

The incidence and appearance of focal fibrillation waves on the right and left atrial epicardial surface were visualized during 10 seconds of persistent atrial fibrillation in a 71-year-old woman with valvular heart disease. The frequent, nonrepetitive, widespread, and capricious distribution of focal waves suggests that transmural conduction of fibrillation waves is most likely the mechanism underlying focal fibrillation waves.

HALT & REVERSE: Hsf1 activators lower cardiomyocyt damage; towards a novel approach to REVERSE atrial fibrillation.

Background: Atrial fibrillation is a progressive arrhythmia, the exact mechanism underlying the progressive nature of recurrent AF episodes is still unknown. Recently, it was found that key players of the protein quality control system of the cardiomyocyte, i.e.

A novel intra-operative, high-resolution atrial mapping approach.

Purpose: A new technique is demonstrated for extensive high-resolution intra-operative atrial mapping that will facilitate the localization of atrial fibrillation (AF) sources and identification of the substrate perpetuating AF.

Methods: Prior to the start of extra-corporal circulation, a 8 × 24-electrode array (2-mm inter-electrode distance) is placed subsequently on all the right and left epicardial atrial sites, including Bachmann's bundle, for recording of unipolar electrograms during sinus rhythm and (induced) AF. AF is induced by high-frequency pacing at the right atrial free wall.

Diagnosis and Therapy of Atrial Fibrillation: The Past, The Present and The Future.

Atrial fibrillation (AF) is the most common age-related cardiac arrhythmia. It is a progressive disease, which makes treatment difficult. The progression of AF is caused by the accumulation of damage in cardiomyocytes which makes the atria more vulnerable for AF.

Tachycardia-induced silencing of subcellular Ca2+ signaling in atrial myocytes.

Atrial fibrillation (AF) is characterized by sustained high atrial activation rates and arrhythmogenic cellular Ca2+ signaling instability; however, it is not clear how a high atrial rate and Ca2+ instability may be related. Here, we characterized subcellular Ca2+ signaling after 5 days of high atrial rates in a rabbit model. While some changes were similar to those in persistent AF, we identified a distinct pattern of stabilized subcellular Ca2+ signaling.

Transmural conduction is the predominant mechanism of breakthrough during atrial fibrillation: evidence from simultaneous endo-epicardial high-density activation mapping.

Background: Endo-epicardial dissociation (EED) of electric activations resulting in transmural conduction of fibrillation waves (breakthroughs) has been postulated to contribute to the complexity of the substrate of atrial fibrillation (AF). The aim of this study was to elucidate the correlation between EED and incidence of breakthrough and to test the plausibility of transmural conduction versus ectopic focal discharges as sources of breakthrough.

Methods And Results: We analyzed high-resolution simultaneous endo-epicardial in vivo mapping data recorded in left atrial free walls of goats with acute AF, 3 weeks and 6 months of AF (all n=7).

Electrophysiological effects of acute atrial stretch on persistent atrial fibrillation in patients undergoing open heart surgery.

Background: The electrophysiologic effects of acute atrial dilatation and dedilatation in humans with chronic atrial fibrillation remains to be elucidated.

Objective: To study the electrophysiological effects of acute atrial dedilatation and subsequent dilatation in patients with long-standing persistent atrial fibrillation (AF) with structural heart disease undergoing elective cardiac surgery.

Methods: Nine patients were studied.

Aldosterone promotes atrial fibrillation.

Aims: Hyperaldosteronism is associated with an increased prevalence of atrial fibrillation (AF). However, it is unclear whether this is the consequence of altered haemodynamics or a direct aldosterone effect. It was the aim of the study to demonstrate load-independent effects of aldosterone on atrial structure and electrophysiology.

Electropathological substrate of longstanding persistent atrial fibrillation in patients with structural heart disease: epicardial breakthrough.

Background: During persistent atrial fibrillation (AF), waves with a focal spread of activation are frequently observed. The origin of these waves and their relevance for the persistence of AF are unknown.

Methods And Results: In 24 patients with longstanding persistent AF and structural heart disease, high-density mapping of the right and left atria was performed during cardiac surgery.

Electropathological substrate of long-standing persistent atrial fibrillation in patients with structural heart disease: longitudinal dissociation.

Background: The electropathological substrate of persistent atrial fibrillation (AF) in humans is largely unknown. The aim of this study was to compare the spatiotemporal characteristics of the fibrillatory process in patients with normal sinus rhythm and long-standing persistent AF.

Methods And Results: During cardiac surgery, epicardial mapping (244 electrodes) of the right atrium (RA), the left lateral wall (LA), and the posterior left atrium (PV) was performed in 24 patients with long-standing persistent AF.

Role of progressive widening of the temporal excitable gap for perpetuation of atrial fibrillation in the goat.

Background: Previous studies suggest that a short temporal excitable gap exists between the fibrillation waves during atrial fibrillation (AF). The aim of this study was to investigate the role of that gap in the development of sustained AF in goats.

Methods And Results: Eight female goats were instrumented with left atrium (LA) electrodes, and sustained AF (>24 h) was induced by intermittent rapid atrial pacing for 9.

Progression from paroxysmal to persistent atrial fibrillation clinical correlates and prognosis.

Objectives: We investigated clinical correlates of atrial fibrillation (AF) progression and evaluated the prognosis of patients demonstrating AF progression in a large population.

Background: Progression of paroxysmal AF to more sustained forms is frequently seen. However, not all patients will progress to persistent AF.

Analysis of fractionated atrial fibrillation electrograms by wavelet decomposition.

This study introduces the use of wavelet decomposition of unipolar fibrillation electrograms for the automatic detection of local activation times during complex atrial fibrillation (AF). The purpose of this study was to evaluate this technique in patients with structural heart disease and longstanding persistent AF. In 46 patients undergoing cardiac surgery, unipolar fibrillation electrograms were recorded from the right atrium, using a mapping array of 244 electrodes.

Effects of intrapericardial sotalol and flecainide on transmural atrial electrophysiology and atrial fibrillation.

Introduction: Intrapericardial (IPC) delivery of antiarrhythmic agents is an appealing idea to increase the therapeutic width and reduce side effects of drugs, particularly in the thin atria. The aim of this study was to determine the effects of IPC versus intravenous (IV) d,l-sotalol and flecainide infusion on transmural atrial electrophysiology and sustained atrial fibrillation (AF) in the goat.

Methods And Results: Effects of IPC and IV sotalol and flecainide infusion on epi- and endocardial atrial electrophysiology, ECG, and tissue drug concentrations were studied in goats without and with persistent AF (>24 hours).

Distinct contractile and molecular differences between two goat models of atrial dysfunction: AV block-induced atrial dilatation and atrial fibrillation.

Atrial dilatation is an independent risk factor for thromboembolism in patients with and without atrial fibrillation (AF). In many patients, atrial dilatation goes along with depressed contractile function of the dilated atria. While some mechanisms causing atrial contractile dysfunction in fibrillating atria have been addressed previously, the cellular and molecular mechanisms of atrial contractile remodeling in dilated atria are unknown.

Low-frequency oscillations of atrial fibrillation cycle length in goats: characterization and potentiation by class III antiarrhythmic almokalant.

Background: In chronically fibrillating goats, low-frequency oscillations (LFOs) of atrial fibrillation cycle length (AFCL) with a deceleration-acceleration sequence have been observed. The present investigation characterized such oscillations in control conditions and during the infusion of class III antiarrhythmic almokalant, trying to understand their mechanism and possible relevance.

Methods And Results: The study was performed on fibrillating goats instrumented with multiple electrodes.

Management of atrial fibrillation in patients with heart failure.

Atrial fibrillation (AF) and chronic heart failure (CHF) are two major and even growing cardiovascular conditions that often coexist. However, few data are available to guide treatment of AF in patients with CHF. This review summarizes current literature concerning the following topics: (i) prognostic relevance of AF in patients with CHF, (ii) relevance and strategies of rhythm and rate control in patients with AF and CHF, and (iii) options for prevention of AF in patients with ventricular dysfunction.