Clifford J. Garratt

A meta‐analysis of the prognostic significance of atrial fibrillation in chronic heart failure

Atrial fibrillation (AF) is one of the commonest sustained arrhythmias in chronic heart failure (CHF), although the prognostic implications of the presence of AF in CHF remain controversial. We have therefore performed this meta‐analysis to study the effects of the presence of AF on mortality in CHF patients.

Reversal of atrial electrical remodeling after cardioversion of persistent atrial fibrillation in humans.

BACKGROUND Although atrial electrical remodeling has been studied extensively in animal models, the reversibility of this phenomenon after termination of clinical atrial fibrillation (AF) has not been demonstrated. We aimed to examine this important question of reversibility by using AF cycle length (AFCL) and coupling intervals of atrial premature beats after cardioversion as measures of atrial refractoriness. METHODS AND RESULTS We measured AFCL at the right atrial appendage and distal coronary sinus before attempting internal cardioversion in 39 patients with persistent AF. Patients were monitored by daily transtelephonic recordings after discharge and admitted rapidly for repeat internal cardioversion if there was spontaneous AF recurrence. Measurements of AFCL were repeated immediately before repeat cardioversions in the 17 patients who had recurrence of AF. There was an increase in AFCL from the initial cardioversion to that measured at the time of first AF recurrence at both the right atrial appendage (161+/-22 vs 167+/-26 ms, P=0.05) and distal coronary sinus (162+/-20 vs 168+/-22 ms, P=0.01) sites. The magnitude of increase in AFCL was positively correlated with duration of sinus rhythm before AF recurrence (r=0.524, P=0.001). Other measures of refractoriness (shortest coupling interval of atrial premature beats and directly measured refractory periods after cardioversion) also increased from initial to subsequent cardioversions. CONCLUSIONS These findings demonstrate that changes in atrial electrophysiology associated with chronic AF in humans are reversible after cardioversion and that the extent of this reversal is dependent on the duration of sinus rhythm after cardioversion.

Pro‐arrhythmogenic effects of atrial fibrillation‐induced electrical remodelling: insights from the three‐dimensional virtual human atria

•  Previous studies have shown that atrial electrical properties are altered (remodelled) by atrial fibrillation (AF) and that the recurrence of AF is high following remodelling. However, demonstrating a causal link between atrial remodelling in experimental models and the increased risk of AF is a challenge. •  AF‐induced electrical remodelling abbreviated atrial action potential duration (APD) non‐uniformly across the atria; this resulted in relatively short APDs co‐existing with marked regional differences in the APD at junctions of the crista terminalis/pectinate muscle, pulmonary veins/left atrium. •  It increases tissue vulnerability to re‐entry initiation and maintenance at these tissue junctions. •  The AF‐induced electrical remodelling also stabilized and accelerated re‐entrant excitation waves, leading to rapid and sustained re‐entry. •  This study provides novel insights towards understanding the mechanisms underlying the pro‐arrhythmic effects of the AF‐induced electrical remodelling in atrial tissue.

Repetitive 4-Week Periods of Atrial Electrical Remodeling Promote Stability of Atrial Fibrillation Time Course of a Second Factor Involved in the Self-Perpetuation of Atrial Fibrillation

Background—Episodes of atrial fibrillation (AF) are known to cause both a rapid reduction in atrial refractoriness (atrial electrical remodeling) and a more delayed increase in AF stability thought to be due to a so-called “second factor.” The aim of this study was to quantify the effects and time course of such a factor on AF stability in the chronic goat model. Methods and Results—AF was maintained in 6 goats by burst atrial pacing for 3 consecutive 4-week periods separated a mean of 6±2.1 days of sinus rhythm. Six days of sinus rhythm was just sufficient for refractoriness changes to reverse fully in all goats. Atrial effective refractory period, AF inducibility, and duration of individual episodes of AF were assessed at regular intervals. There was a progressive reduction from month 1 to 2 to 3 in the mean duration of burst pacing required to induce individual episodes of AF of 60 seconds (178±251, 110±102, and 21±30 hours), 1 hour (229±224, 136±104, and 68±51 hours), and 24 hours (277±218, 192±190, and 102±75 hours; P <0.03). The frequency with which AF was induced during extrastimulus pacing increased progressively from 16.7% in month 1 to 31.7% in month 2 and 46.9% in month 3 (P <0.001). Conclusions—Sequential 4-week periods of atrial fibrillation result in a progressive increase in AF stability independent of baseline atrial refractory period. This finding suggests the presence of a second factor in the self-perpetuation of AF with a time course comparable to that of AF-induced ultrastructural changes in the atria.

Radiofrequency catheter ablation of Mahaim tachycardia by targeting Mahaim potentials at the tricuspid annulus.

BACKGROUND--Reentrant tachycardias associated with Mahaim pathways are rare but potentially troublesome. Various electrophysiological substrates have been postulated and catheter ablation at several sites has been described. OBJECTIVE--To assess the efficacy and feasibility of targeting discrete Mahaim potentials recorded on the tricuspid annulus for the delivery of radiofrequency energy in the treatment of Mahaim tachycardia. PATIENTS--21 patients out of a consecutive series of 579 patients referred to one of three tertiary centres for catheter ablation of accessory pathways causing tachycardia. All had symptoms and presented with tachycardia of left bundle branch block configuration or had this induced at electrophysiological study. In all cases, the tachycardia was antidromic with anterograde conduction over a Mahaim pathway. RESULTS--6 patients had additional tachycardia substrates (4 had accessory atrioventricular connections and 2 had dual atrioventricular nodal pathways and atrioventricular nodal reentry). After ablation of the additional pathways, Mahaim potentials were identified in 16 (76%) associated with early activation of the distal right bundle branch and radiofrequency energy at this site on the tricuspid annulus abolished Mahaim conduction in all 16 cases. In 2 patients there was early ventricular activation at the annulus without a Mahaim potential but radiofrequency energy abolished pre-excitation. In the remaining patients no potential could be found (1 patient), no tachycardia could be induced after ablation of an additional pathway (1 patient), or no Mahaim conduction was evident during the study (1 patient). During follow up (1-29 months (median 9 months)) all but 1 patient remained symptom free without medication. CONCLUSIONS--Additional accessory pathways seem to be common in patients with Mahaim tachycardias. The identification of Mahaim potentials at the tricuspid annulus confirms that most of these pathways are in the right free wall and permits their successful ablation and the abolition of associated tachycardia.

Clinical Indications for Genetic Testing in Familial Sudden Cardiac Death Syndromes: an HRUK Position Statement

The sudden unexpected death of a young person can have profound implications for the surviving family members beyond those associated with bereavement and the immediate sense of loss. Among these other sequelae may be a concern that the sudden death was caused by a genetic condition and that other family members may suffer the same fate. Increased awareness of these inherited conditions and the transfer of the techniques of genetic testing from the research laboratory into the clinical arena make it possible to identify genetically affected individuals before they have symptoms or experience sudden cardiac death. The development of such tests has been paralleled by the emergence of preventative treatments, which have amplified the clinical importance of such tests. This document provides recommendations regarding the clinical indications for these tests based on the best available evidence.

RCPE UK Consensus Conference on 'Approaching the comprehensive management of atrial fibrillation: evolution or revolution?'.

1David Cargill Professor of Geriatric Medicine, University of Glasgow, Glasgow; 2Consultant Physician in General and Elderly Care Medicine, Cwm Taf Health Board, Royal Glamorgan Hospital, Glamorgan, Wales; 3Professor of Cardiology, Manchester Heart Centre, Manchester; 4General Practitioner, University Health Centre, York University, York; 5General Practitioner, Handsworth Wood Medical Centre, Birmingham; 6Immediate Past President BASP and Consultant Stroke Physician/Clinical Senior Lecturer, Royal Devon and Exeter Hospital/Peninsula Medical School, Exeter; 7Lecturer in Cardiovascular Health, University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham; 8Lecturer Practitioner, University of Leeds, Leeds; 9Consultant Cardiologist, Bradford Hospitals NHS Trust, Bradford; 10Director of Advice and Support, Chest, Heart & Stroke, Scotland, UK; 11Freelance Writer J R Coll Physicians Edinb 2012; 42:34–5 http://dx.doi.org/10.4997/JRCPE.2012.S01

Clinical evaluation of a policy of early repeated internal cardioversion for recurrence of atrial fibrillation.

Early Repeated Cardioversion for AF Recurrence. Introduction: The clinical value of cardioversion (CV) of persistent atrial fibrillation (AF) is limited by the high rate of early AF recurrence, which may be related to the persistence of atrial electrical remodeling. We examined the hypothesis that the likelihood of maintaining sinus rhythm after CV of persistent AF is significantly enhanced by a policy of early repeated CV.

Profibrillatory effects of verapamil but not of digoxin in the goat model of atrial fibrillation.

Profibrillatory Effects of Verapamil. Introduction: Verapamil and digoxin have been shown to modulate tachycardia‐induced atrial electrical remodeling. The goal of the present study was to determine the direct effects of verapamil and digoxin on atrial fibrillation (AF), before and after electrical remodeling.

Safety and acceptability of implantation of internal cardioverter-defibrillators under local anesthetic and conscious sedation.

Background: Implantation and testing of implantable defibrillators (ICDs) using local anesthetic and conscious sedation is widely practiced; however, some centers still use general anesthesia. We assessed safety and patient acceptability for implantation of defibrillators using local anesthetic and conscious sedation.