Derick Todd

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.

United Kingdom national experience of entirely subcutaneous implantable cardioverter-defibrillator technology: important lessons to learn

AIMS The aim of this study was to describe the early phase United Kingdom (UK) clinical experience with a novel entirely subcutaneous implantable cardioverter-defibrillator (S-ICD). METHODS AND RESULTS A questionnaire was sent to all UK hospitals implanting S-ICDs. Nineteen of 25 (76%) hospitals responded with the details of 111 implanted patients [median 5/hospital (range 1-18)]. Mean duration of follow-up was 12.7 ± 7.1 months. Median patient age was 33 years (range 10-87 years). Underlying pathology was primary electrical disease in 43%, congenital heart disease 12%, hypertrophic cardiomyopathy 20%, ischaemic cardiomyopathy 14%, idiopathic dilated cardiomyopathy 5%, and other cardiomyopathies 7% patients. Nineteen (17%) patients required 20 re-operations, including permanent device explantation in 10 (9%). Twenty-four appropriate shocks were delivered in 13 (12%) patients, including 10 for ventricular fibrillation. One patient suffered arrhythmic death, but there were no failures to detect or terminate ventricular arrhythmias above the programmed detection rate. Fifty-one inappropriate shocks were delivered in 17 (15%) patients. Forty-one (80%) were for T-wave over-sensing and 1 (2%) for atrial flutter-wave over-sensing. The 11 patients who received inappropriate shocks due to T-wave over-sensing were significantly younger than patients who did not (24 ± 10 vs. 37 ± 19 years; P = 0.02). CONCLUSION The S-ICD is an important innovation in ICD technology. However, these data indicate that adverse event rates are significant during early clinical adoption. Important lessons in patient selection, implant technique, and device programming can be learnt from this experience.

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.

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.

Ablation index, a novel marker of ablation lesion quality: prediction of pulmonary vein reconnection at repeat electrophysiology study and regional differences in target values

Aims Force-Time Integral (FTI) is commonly used as a marker of ablation lesion quality during pulmonary vein isolation (PVI), but does not incorporate power. Ablation Index (AI) is a novel lesion quality marker that utilizes contact force, time, and power in a weighted formula. Furthermore, only a single FTI target value has been suggested despite regional variation in left atrial wall thickness. We aimed to study AIs and FTIs relationships with PV reconnection at repeat electrophysiology study, and regional threshold values that predicted no reconnection. Methods and results Forty paroxysmal atrial fibrillation patients underwent contact force-guided PVI, and the minimum and mean AI and FTI values for each segment were identified according to a 12-segment model. All patients underwent repeat electrophysiology study at 2 months, regardless of symptoms, to identify sites of PV reconnection. Late PV reconnection was seen in 53 (11%) segments in 25 (62%) patients. Reconnected segments had significantly lower minimum AI [308 (252-336) vs. 373 (323-423), P < 0.0001] and FTI [137 (92-182) vs. 228 (157-334), P < 0.0001] compared with non-reconnected segments. Minimum AI and FTI were both independently predictive, but AI had a smaller P value. Higher minimum AI and FTI values were required to avoid reconnection in anterior/roof segments than for posterior/inferior segments (P < 0.0001). No reconnection was seen where the minimum AI value was ≥370 for posterior/inferior segments and ≥480 for anterior/roof segments. Conclusion The minimum AI value in a PVI segment is independently predictive of reconnection of that segment at repeat electrophysiology study. Higher AI and FTI values are required for anterior/roof segments than for posterior/inferior segments to prevent reconnection.

Patients' attitude and knowledge about oral anticoagulation therapy: results of a self-assessment survey in patients with atrial fibrillation conducted by the European Heart Rhythm Association

The purpose of this European Heart Rhythm Association survey was to assess the attitude, level of education, and knowledge concerning oral anticoagulants (OACs) among patients with atrial fibrillation (AF) taking vitamin K antagonists (VKAs), non-VKA oral anticoagulants (NOACs) or antiplatelets. A total of 1147 patients with AF [mean age 66 ± 13 years, 529 (45%) women] from 8 selected European countries responded to this survey. The overall use of OACs and antiplatelets was 77 and 15.3%, respectively. Of the patients taking OACs, 67% were on VKAs, 33% on NOACs, and 17.9% on a combination of OACs and antiplatelets. Among patients on VKAs, 91% correctly stated the target international normalized ratio (INR) level. The proportion of patients on VKA medication who were aware that monthly INR monitoring was required for this treatment and the proportion of patients on NOAC who knew that renal function monitoring at least annually was mandatory for NOACs was 76 and 21%, respectively. An indirect estimation of compliance indicated that 14.5% of patients temporarily discontinued the treatment, and 26.5% of patients reported having missed at least one dose. The survey shows that there is room for improvement regarding education and adherence of patients taking OACs, particularly regarding monitoring requirements for NOACs.

Prevalence and Significance of Focal Sources of Atrial Arrhythmia in Patients Undergoing Cardioversion of Persistent Atrial Fibrillation

Atrial Arrhythmias After Cardioversion of AF. Introduction: Recent reports have highlighted the importance of focal atrial arrhythmias as a curable cause fur a group of patients with frequently recurrent paroxysmal atrial fibrillation (AF). The importance of this arrhythmia mechanism in the general population of patients with persistent AF is unknown.

Effect of amiodarone on dispersion of atrial refractoriness and cycle length in patients with atrial fibrillation.

Introduction: Amiodarone is effective in preventing the recurrence of atrial fibrillation (AF) after cardioversion (CV). Dispersion of atrial refractoriness may be relevant to the generation of AF. We designed a study to determine the electrophysiologic effects of amiodarone in patients with previous early recurrence of AF after CV.

Improving Safety in Catheter Ablation for Atrial Fibrillation: A Prospective Study of the Use of Ultrasound to Guide Vascular Access

The most frequent complications of AF ablation (AFA) are related to vascular access, but there is little evidence as to how these can be minimized.

Current periprocedural management of ablation for atrial fibrillation in Europe: results of the European Heart Rhythm Association survey

The purpose of this EP Wire survey was to assess clinical practice in periprocedural management of atrial fibrillation ablation. This survey is based on an electronic questionnaire sent to the European Heart Rhythm Association Research Network members. Responses were received from 78 centres in 20 countries. The results of the survey have shown that periprocedural management is generally in accordance with guidelines and consensus recommendations on ablation for atrial fibrillation ablation, although there are some areas of variation. Differences between high- and low-volume centres are observed with respect to patient selection, antiarrhythmic drug management, and heparin bridging.