Randomized crossover comparison of DDDR versus VDD pacing after atrioventricular junction ablation for prevention of atrial fibrillation. The atrial pacing peri-ablation for paroxysmal atrial fibrillation (PA (3)) study investigators

2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The "2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation" provides recommendations to guide clinicians in the treatment of patients with atrial fibrillation.

METHODS

A comprehensive literature search was conducted from May 12, 2022, to November 3, 2022, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through November 2022, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Atrial fibrillation is the most sustained common arrhythmia, and its incidence and prevalence are increasing in the United States and globally. Recommendations from the "2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" and the "2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" have been updated with new evidence to guide clinicians. In addition, new recommendations addressing atrial fibrillation and thromboembolic risk assessment, anticoagulation, left atrial appendage occlusion, atrial fibrillation catheter or surgical ablation, and risk factor modification and atrial fibrillation prevention have been developed.

2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The "2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Patients With Atrial Fibrillation" provides recommendations to guide clinicians in the treatment of patients with atrial fibrillation.

METHODS

A comprehensive literature search was conducted from May 12, 2022, to November 3, 2022, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through November 2022, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Atrial fibrillation is the most sustained common arrhythmia, and its incidence and prevalence are increasing in the United States and globally. Recommendations from the "2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" and the "2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" have been updated with new evidence to guide clinicians. In addition, new recommendations addressing atrial fibrillation and thromboembolic risk assessment, anticoagulation, left atrial appendage occlusion, atrial fibrillation catheter or surgical ablation, and risk factor modification and atrial fibrillation prevention have been developed.

Impact of high-grade atrioventricular block and cumulative frequent pacing on atrial arrhythmias

BACKGROUND

The relationship between high-grade atrioventricular block (HGAVB) with cumulative frequent pacing and risk of atrial arrhythmias (AAs) has not been well characterized. We hypothesized HGAVB and pacing may have significant impact on incidence and prevalence of AAs by modulating atrial substrate.

OBJECTIVE

To determine impact of HGAVB and pacing on AAs including atrial fibrillation (AF), atrial flutter (AFL), and atrial tachycardia (AT).

METHODS

All consecutive patients who underwent dual-chamber pacemaker implantation for HGAVB from 2005 to 2011 at the University of Chicago were included. AAs and percent of pacing were detected through device interrogation. Patients' data were collected from electronic medical records and clinic visits.

RESULTS

A total of 166 patients (mean age 71 ± 15 years; 54% female, 56% African American) were studied. AF was documented in 27% of patients before pacemaker implantation. During a mean 5.8 ± 2.2 years of follow-up, 47% had device-detected AF, 10% AFL, and 26% AT. New-onset AF was documented in 40 of the 122 patients without prior AF (33%). Continuous (≥ 99%) right ventricular pacing was associated with significantly decreased AF prevalence (34% vs 59%, P = 0.005), and correlated with lower incidence (26% vs 41%, P = 0.22). Pacing suppressed AF in 14% of patients with baseline AF; those patients had lower atrial pacing (3.2% vs 45%, P < 0.0001). Left atrial dilation was the only independent predictor of AF with frequent pacing (P = 0.009).

CONCLUSIONS

HGAVB is associated with high incidence and prevalence of AAs with and without pacing. Cumulative frequent (≥99%) ventricular pacing reduces risk of AF in patients with HGAVB.

Pacing to prevent atrial fibrillation

PURPOSE OF REVIEW

Pacemakers are frequently implanted in patients with atrial fibrillation. Many patients with pacemakers also develop atrial fibrillation. Over a period of time, through many studies on different pacing modes, sites, and algorithms, significant insights have been gained in the field of treatment and prevention of atrial fibrillation. The purpose of this review is to discuss some aspects of the scientific basis, current standards and possible future research related to cardiac pacing for prevention of atrial fibrillation.

RECENT FINDINGS

Trials involving pacing at the alternative pacing site per se or in combination with specific algorithms for prevention of atrial fibrillation have not shown consistent results. Recently, a new generation of antitachycardia pacing therapies has brought on a new optimism with promising outcome data of reduction in permanent atrial fibrillation, cardiovascular hospitalizations, and mortality.

SUMMARY

Multiple trials and clinical observational studies of different pacing methods and algorithms, with the exception of newer therapies in conjunction with atrial pacing algorithms, have not been shown to prevent atrial fibrillation. Hence, while permanent pacing is indicated for sinus node dysfunction and conduction abnormalities in patients with or without atrial fibrillation, the prevailing data in the literature does not support implantation of a permanent pacemaker for prevention of atrial fibrillation per se.

Management of Patients with Atrial Fibrillation: Focus on Treatment Options

Atrial fibrillation (AF) is leading cardiac arrhythmia with important clinical implications. Its diagnosis is usually made on the basis on 12-lead ECG or 24-hour Holter monitoring. More and more clinical evidence supports diagnostic use of cardiac event recorders and cardiovascular implantable electronic devices (CIED). Treatment options in patients with atrial fibrillation are extensive and are based on chosen rhythm and/or rate control strategy. The use and selected contraindications to AF related pharmacotherapy, including anticoagulants are shown. Nonpharmacological treatments, comorbidities and risk factors control remain mainstay in the treatment of patients with AF. Electrical cardioversion consists important choice in rhythm control strategy. Much progress has been made in the field of catheter ablation and cardiac surgery methods. Left atrial appendage occlusion/closure may be beneficial in patients with AF. CIED are used with clinical benefits in both, rhythm and rate control. Pacemakers, implantable cardioverter-defibrillators and cardiac resynchronization therapy devices with different pacing modes have guaranteed place in the treatment of patients with AF. On the other hand, the concepts of permanent leadless cardiac pacing, atrial dyssynchrony syndrome treatment and His-bundle or para-Hisian pacing have been proposed. This review summarizes and discusses current and novel treatment options in patients with atrial fibrillation.

The role of implantable devices to treat atrial fibrillation

In the last decades several nonpharmacological therapies for the treatment and prevention of atrial fibrillation (AF) have been developed. Pacemakers play a potential important role in the nonpharmacological management of AF. In patients with sinus node dysfunction both, atrial and dual-chamber pacing, have been proven to prevent or delay progression to permanent AF compared with ventricular pacing alone. However, in patients without conventional indications for pacing, the utility of pacemakers as a stand-alone therapy has not yet proven. Following the positive results obtained by low energy internal defibrillation, specific implantable devices for AF cardioversion have been developed. Despite implantable atrial defibrillators being possible alternatives for drug refractory AF, industry did not further develop these due to shock discomfort. Newer implantable pulse generators also offer data storage that permits detection of asymptomatic AF. Such a help provided by implantable devices, has been enhanced by the development and spread out of remote monitoring systems.

A placebo-controlled, double-blind, randomized, multicenter study to assess the effects of dronedarone 400 mg twice daily for 12 weeks on atrial fibrillation burden in subjects with permanent pacemakers

Purpose

Dronedarone is a benzofuran derivative with a pharmacological profile similar to amiodarone but has a more rapid onset of action and a much shorter half-life (13–19 h). Our goal was to evaluate the efficacy of dronedarone in atrial fibrillation (AF) patients using dual-chamber pacemakers capable of quantifying atrial fibrillation burden.

Methods

Pacemakers were adjusted to optimize AF detection. Patients with AF burden >1 % were randomized to dronedarone 400 mg twice daily (BID) or placebo. Pacemakers were interrogated after 4 and 12 weeks of treatment. The primary endpoint was the change in AF burden from baseline over the 12-week treatment period. Patients with permanent AF, severe/recently decompensated heart failure, and current use of antiarrhythmic drugs were excluded. AF burden was assessed by a core laboratory blinded to treatment assignment.

Results

From 285 patients screened, 112 were randomized (mean age 76 years, 60 % male, 84 % hypertensive, 65 % with sick sinus syndrome, 26 % with diabetes mellitus type II, 15 % with heart failure). Baseline mean (SEM) AF burden was 8.77 % (0.16) for placebo and 10.14 % (0.17) for dronedarone. Over the 12-week study period, AF burden compared to baseline decreased by 54.4 % (0.22) (P = 0.0009) with dronedarone and trended higher by 12.8 % (0.16) (P = 0.450) with placebo. The absolute change in burden was decreased by 5.5 % in the dronedarone group and increased by 1.1 % in the placebo group. Heart rate during AF was reduced to approximately 4 beats/min with dronedarone (P = 0.285). Adverse events were higher with dronedarone compared to placebo (65 vs 56 %).

Conclusions

Dronedarone reduced pacemaker-assessed the relative AF burden compared to baseline and placebo by over 50 % during the 12-week observation period.

Hybrid therapy in the management of atrial fibrillation

Atrial fibrillation is the most common sustained arrhythmia. Because of the sub-optimal outcomes and associated risks of medical therapy as well as the recent advances in non-pharmacologic strategies, a multitude of combined (hybrid) algorithms have been introduced that improve efficacy of standalone therapies while maintaining a high safety profile. Antiarrhythmic administration enhances success rate of electrical cardioversion. Catheter ablation of antiarrhythmic drug-induced typical atrial flutter may prevent recurrent atrial fibrillation. Through simple ablation in the right atrium, suppression of atrial fibrillation may be achieved in patients with previously ineffective antiarrhythmic therapy. Efficacy of complex catheter ablation in the left atrium is improved with antiarrhythmic drugs. Catheter ablation followed by permanent pacemaker implantation is an effective and safe treatment option for selected patients. Additional strategies include pacing therapies such as atrial pacing with permanent pacemakers, preventive pacing algorithms, and/or implantable dual-chamber defibrillators are available. Modern hybrid strategies combining both epicardial and endocardial approaches in order to create a complex set of radiofrequency lesions in the left atrium have demonstrated a high rate of success and warrant further research. Hybrid therapy for atrial fibrillation reviews history of development of non-pharmacological treatment strategies and outlines avenues of ongoing research in this field.

Influence of structural heart disease on characteristics of atrial fibrillation recurrence in patients with dual-chamber pacemakers

AIMS

The aim of the study was to prospectively examine the influence of structural heart disease (SHD) and sinus node dysfunction (SND) on the frequency and duration of atrial fibrillation (AF) episodes in patients with implanted pacemakers.

METHODS

We examined episodes of AF in 207 patients (93 with SHD; 165 with SND) with known or suspected paroxysmal AF who underwent dual-chamber pacing.

RESULTS

Seventy-one percent of all patients experienced at least one episode of AF during follow-up, with a mean burden of 3.3 +/- 6.4 h/d (median, 0.2 hours) and a mean frequency of 11.7 +/- 26.0 episodes per day (median, 1.4). The proportion of episodes longer than 6 hours was greater in patients with SHD when compared to patients without SHD. In a logistic regression model adjusted for SND, gender, and the 2-way interactions of SND, sex, and SHD, SHD was a significant factor (P = .0188) with the odds ratio of having an episode longer than 6 hours 3.4 times higher for patients with SHD than for patients without SHD. Older patients with SHD had less frequent but longer episodes compared to younger patients. In patients without SHD, there was no comparable age difference. Burden, frequency, and average episode length were not influenced by the presence or absence of SND.

CONCLUSIONS

Patients with SHD have longer episodes of AF supporting the concept that SHD influences the underlying substrate to favor perpetuation.

Progression of paroxysmal atrial fibrillation to persistent atrial fibrillation in patients with bradyarrhythmias

INTRODUCTION

The experimental concept that "atrial fibrillation (AF) begets AF" implies that atrial tachyarrhythmia (AT)/AF burden uniformly increases over time. However, the temporal patterns of paroxysmal AT/AF burden progression, its conversion to persistent AF, and the relationship to underlying disease in humans are unknown. We analyzed the average daily AT/AF burden in patients with concomitant bradycardia and paroxysmal AF to examine these issues.

METHODS

Three hundred thirty patients with a history of paroxysmal AF (mean age 70 +/- 10 years; 61% male) were implanted with a pacemaker that automatically recorded the cumulative daily AT/AF burden. Persistent AT/AF was defined as 7 consecutive days with >23 hours of AT on the device data logs. Antiarrhythmic drug therapy was required to be stable for at least 7 months.

RESULTS

Average follow-up was 401 +/- 123 days. Seventy-eight patients (24%) progressed to persistent AT/AF during the follow-up period with a mean interval of 147 +/- 149 days. Mean AT/AF burden increased progressively (slope 14 s/d, P < .001) over 500 days after implant, and median AT/AF burden also increased (P < .01) in this subgroup of patients. This increase was highly correlated with the presence of structural heart disease (P < .001). There was a concomitant decrease in atrial premature beat (APB) frequency. Most patients transitioning to persistent AF were in sinus rhythm with minimal AT/AF burden in the days immediately before persistent AF. Neither mean nor median AT/AF burden increased over time in patients remaining in paroxysmal AF (slope 0 s/d, P = .7) despite a higher APB frequency than in patients with heart disease (P =.003) and a higher likelihood of daily AT/AF events (P < .001).

CONCLUSIONS

Temporal patterns of AT/AF burden in patients developing persistent AF show a progressive increase with a sudden transition to persistent AF. This is more consistent with substrate changes, rather than increased density of triggering APBs or paroxysmal AT/AF events. Thus, progression to persistent AF is probably related to an AF substrate, which is undergoing progressive structural remodeling owing to heart disease and other factors and is now suddenly capable of sustaining prolonged or multiple ATs. Therapies directed at the atrial substrate may be needed to prevent persistent AF.

Catheter ablation as first-line therapy for patients with symptomatic atrial fibrillation

Atrial fibrillation (AF) is a common clinical problem that is associated with an impaired quality of life, thromboembolism, heart failure and death. Medical treatment of AF remains suboptimal and is associated with potentially serious side effects. The disappointing outcomes with medical therapy have spurred the age of catheter ablation of AF. In the last 10 years, catheter ablation of AF has evolved dramatically and has been shown to be superior to medical therapy in multiple studies. As a result, catheter ablation may be offered to the symptomatic patient as first-line therapy in lieu of antiarrhythmic medications, which have limited efficacy and are associated with significant toxicity.

The role of pacing in rhythm control and management of atrial fibrillation

Atrial fibrillation is the most common sustained cardiac arrhythmia and is increasing in prevalence with an ageing population. As the arrhythmia is often asymptomatic the true prevalence is likely even higher. Largely because of stroke this arrhythmia places a huge financial burden on the health economy. Despite this, large studies assessing rate versus rhythm control have been equivocal. Because of the ineffectiveness of pharmacological therapy much research effort has been undertaken in device and ablative approaches to rhythm management. Although catheter ablation has gained favour because of the high success rates the technique requires considerable expertise and still has a significant complication profile maintaining interest in pacing therapies for atrial fibrillation. Dual chamber versus single-chamber ventricular pacing has been shown to significantly reduce the incidence of atrial fibrillation. Research is currently underway to see if minimising the deleterious effects of right ventricular apical pacing could further increase the benefits of atrioventricular synchronous pacing. Several studies show some (albeit variable) reduction in AF burden with anti-AF algorithms in the setting of bradycardia. Antitachycardia pacing, on the other hand, has not been shown to treat AF in a randomised trial despite the successful termination of co-existent atrial tachycardias. There is increasing evidence that alternative atrial pacing sites may treat AF by improving atrial function. Furthermore, these strategies coupled with other therapies in a 'hybrid approach' have also showed promising results.

Pacing therapy for prevention of atrial fibrillation

The role of permanent pacing for the prevention of atrial fibrillation is reviewed. A moderate decrease in the incidence of acute and chronic atrial fibrillation has been seen with atrial pacing compared with ventricular pacing, especially in patients with sinus node dysfunction based on a meta-analysis of clinical trials. A variety of different pacing algorithms have been studied in small numbers of patients for only short durations of time and have shown an inconsistent effect on different measures of atrial fibrillation burden. The interatrial septum or Bachmann's bundle has been shown in some, but not all, studies to have a beneficial effect on reducing the incidence of atrial fibrillation. Less well studied is the combined benefit of alternate site atrial pacing combined with atrial fibrillation prevention pacing algorithms. Device measurement of the duration of atrial fibrillation appears to be an accurate measure of disease burden, and preliminary evidence suggests that atrial fibrillation burden is associated with an increased risk of stroke and death. Future studies are needed to demonstrate the long-term efficacy of device algorithms for the prevention or termination of atrial fibrillation.

Physiologic Pacing in Patients With Obstructive Sleep Apnea

OBJECTIVES

This study was designed to assess the impact of prevention of bradycardia with physiologic pacing on the severity of obstructive sleep apnea.

BACKGROUND

Apneic episodes during sleep are associated with slowing of the heart rate during apnea and tachycardia with subsequent arousal. Patients with permanent pacemakers may have reduced episodes of sleep apnea when their pacemaker rate is set faster than their spontaneous nocturnal heart rate.

METHODS

We conducted a prospective, randomized, single-blind crossover trial of temporary atrial pacing in obstructive sleep apnea to reduce the apnea hypopnea index (AHI). Fifteen patients (age 60 +/- 13 years, 12 men) with moderate to severe obstructive sleep apnea (AHI 34 +/- 14) underwent insertion of an externalized atrial permanent pacing system via the left subclavian vein. Patients underwent overnight respiratory sleep studies in hospital, during atrial pacing at 75 beats/min, and with pacing turned off. The order of pacing mode was randomized, with crossover the subsequent night to the other mode. Patients were blinded to pacing mode, and the analysis of sleep recordings was blind to pacing mode.

RESULTS

Pacing was tolerated without complications in all patients. Overnight physiologic pacing did not affect the AHI (pacing 39 +/- 21/h vs. control 42 +/- 21/h, p = 0.23, 95% confidence interval -9.3 to 2.5 for difference), desaturation time (pacing 3.8 +/- 6.0% vs. control 3.5 +/- 4.3%, p = 0.70), or the minimum SaO(2) (pacing 75 +/- 10% vs. control 77 +/- 11%, p = 0.38). There was a borderline significant reduction in circulatory time with pacing (pacing 23.4 +/- 3.2 s vs. control 25.5 +/- 4.4 s, p = 0.09).

CONCLUSIONS

Temporary atrial pacing does not appear to improve respiratory manifestations of obstructive sleep apnea. Permanent atrial pacing in this patient population does not appear to be justified.

Device-based therapies for atrial fibrillation

Ablation of the atrioventricular conduction system and pacemaker implantation is the preferred procedure for patients with atrial fibrillation (AF) in whom a rate control strategy has been selected but in whom rate-controlling medications are intolerable or ineffective. Selection of standard right ventricular (RV) pacing versus biventricular pacing is individualized, based on the degree and etiology of left ventricular dysfunction. Atrial-based pacing is clearly preferable to ventricular-based pacing in patients with sick sinus syndrome, because it leads to a reduction in the development of AF. Emerging evidence indicates that excess RV pacing is deleterious, increasing AF, heart failure, and possibly mortality. Therefore, physiologic pacing with minimization of RV pacing is desirable. Atrial pacing algorithms that increase the frequency of atrial pacing have shown modest efficacy in the prevention of AF. Use of atrial pacing algorithms is reasonable for patients with a history of AF and standard bradycardia indications for permanent pacing in whom maintenance of sinus rhythm is desirable. Studies assessing novel and multiple site atrial pacing therapies have mixed results, without compelling evidence of clinically important benefit. The exceptions are biatrial and right atrial overdrive pacing immediately after cardiac surgery. Several studies have shown effective suppression of postoperative AF with their use. Device therapy (eg, atrial antitachycardia pacing and defibrillation) for the termination of AF is effective in reducing arrhythmia burden. However, improvement in clinically relevant end points is not established and indications are not clearly defined. If a patient lacks an indication for an implantable cardioverter-defibrillator, we do not offer atrial defibrillation as a treatment option. Atrial arrhythmias may be better prevented by programming to avoid ventricular pacing than by specific atrial interventions.

Catheter Ablation of Atrial Fibrillation Versus Atrioventricular Junction Ablation Plus Pacing Therapy for Elderly Patients with Medically Refractory Paroxysmal Atrial Fibrillation

BACKGROUND

Catheter ablation of atrial fibrillation (AF) has become another nonpharmacologic therapeutic option for medically refractory paroxysmal AF. Whether this method is better than atrioventricular (AV) junction ablation plus pacing therapy is unknown. The purpose of this study was to compare the very long-term (longer than 4 years) clinical outcomes of the 2 methods in elderly patients (>65 years old) with medically refractory paroxysmal AF.

METHODS

From January 1995 to December 2001, 71 elderly patients with medically refractory paroxysmal AF were included; group 1 included 32 patients with successful AV junction ablation plus pacing therapy and group 2, 37 patients with successful catheter ablation of AF.

RESULTS

After a mean follow-up of more than 52 months, the AF was better controlled in the group 1 patients than group 2 (100% vs 81%, P = 0.013), however, they had a significantly higher incidence of persistent AF (69% vs 8%, P < 0.001) and heart failure (53% vs 24%, P = 0.001). Furthermore, the incidence of ischemic stroke and cardiac death was similar between the 2 groups. Compared with the preablation values, a significant increase in the NYHA functional class (1.7 +/- 0.9 vs 1.4 +/- 0.7, P = 0.01) and significant decrease in the left ventricular ejection fraction (44 +/- 8% vs 51 +/- 10%, P = 0.01) were noted in the group 1 patients, but not in the group 2 patients.

CONCLUSIONS

Although AV junction ablation plus pacing therapy better controlled the AF in elderly patients with medically refractory paroxysmal AF, that method was associated with a higher incidence of persistent AF and heart failure than catheter ablation of AF in the very long-term follow-up.

Limited Benefit of Septal Pre-Excitation in Pace Prevention of Atrial Fibrillation

BACKGROUND

Pre-excitation of the intra-atrial septum (IAS) by pacing at the ostium of the coronary sinus (CSO) can prevent atrial fibrillation (AF) in case of single atrial premature beats (APBs). We investigated whether pre-excitation of IAS, either by pacing at CSO or at the right ventricle in the presence of retrograde conduction (RV), can prevent atrial tachyarrhythmia triggered by single and multiple APBs. AF vulnerability was compared to pacing at the right atrium (RA) and sinus rhythm (SR).

METHODS

Seventeen patients, age 52 +/- 21 years, who exhibited retrograde VA conduction and reproducible induction of atrial tachyarrhythmia during an electrophysiological procedure, were studied. Both during SR and pacing (S1-S1:600 ms) at RA, CSO, and right ventricle (RV), single (A1-S2:200 ms) and multiple premature stimuli (A1-S2-S3-S4:200-180-180 ms) were delivered at RA (4 x diastolic threshold).

RESULTS

During pacing at RA, single and multiple APBs invariably induced runs of atrial tachyarrhythmia (mean duration 34 +/- 67 sec and 37 +/- 69 sec, range 1 sec to 20 min). During preventive pacing at CSO and RV, single APBs (A1-S2:200 ms) did not induce atrial arrhythmia (0 +/- 0 sec, 0 +/- 0 sec, P < 0.05 vs pacing at RA). In contrast, when multiple APBs were applied, pacing at CSO or RV failed to prevent initiation of AF (mean duration 36 +/- 63 sec, 38 +/- 65 sec, NS). Also during SR, single APBs did not induce AF (0 +/- 0 sec, P < 0.05 vs pacing at RA) whereas multiple APBs invariably induced AF (39 +/- 74 sec, NS).

CONCLUSIONS

Compared to pacing at RA, pre-excitation of IAS either by pacing at CSO or at RV with retrograde conduction can prevent initiation of paroxysms of atrial tachyarrhythmia triggered by single but not by multiple right APBs. These findings imply that the potential benefit of choosing an optimal pacing site in patients requiring atrial-based pacing is limited. Moreover, in the absence of bradycardia, no specific pacing site offers incremental benefit over the natural "protective" effect of sinus rhythm.

Atrial fibrillation: profit from cardiac pacing?

The impact of cardiac pacing on the prevention of atrial fibrillation is under scientific investigation. Several prospective randomised clinical trials have reported that atrial-based "physiologic" AAI(R)- or DDD(R)-pacing is associated with a lower incidence of paroxysmal and permanent atrial fibrillation than single-chamber ventricular pacing in patients with a conventional pacemaker indication. However, it is still uncertain whether atrial pacing itself has independent antiarrhythmic properties. In contrast, right ventricular pacing is considered to promote atrial fibrillation, even in preserved AV synchrony during dual-chamber pacing. The electrical secondary prevention of atrial fibrillation is mainly based on variations of the atrial pacing site and sophisticated preventive pacing algorithms incorporated in the pacemaker software. Dual-site right atrial and biatrial pacing were reported to exhibit modest to no benefit for the prevention of atrial fibrillation, whereas septal pacing and specific preventive pacing algorithms have been demonstrated to reduce the incidence of atrial fibrillation in a number of clinical trials. However, the role of septal pacing and preventive pacing algorithms still has to be clarified since, overall, study results have been inconsistent so far. One of the main goals of future investigations should be the identification of responder groups of preventive pacing concepts. In clinical practice, the efficacy of pacing algorithms and septal pacing has to be determined in the individual case. These options should be taken into account in patients with symptomatic bradycardia as the indication for cardiac pacing and, in addition, symptomatic atrial fibrillation.

Feasibility of his bundle pacing as an alternative pacing site: measurement of his refractoriness

BACKGROUND

Direct pacing of the His bundle has been proposed for permanent pacing to maintain physiological synchrony of ventricular activation. Measurement of His bundle refractoriness may be useful in predicting suitability of this technique in an individual. We sought to determine whether this could be measured consistently in patients, defining a normal range.

METHODS

His bundle pacing was performed in 20 consecutive patients (mean age 44.6 +/- 19.5, 5 male) undergoing electrophysiology study. Incremental and extrastimulus testing were performed from the His region to determine effective and functional refractory periods of the His bundle.

RESULTS

Consistent His capture was possible in 18 of 20 (90%) patients studied. Extrastimulus testing from the His region at a drive cycle length of 600 msec was successful in all of these patients. With loss of His capture, QRS duration prolonged 32%, and stimulus to atrial electrogram interval prolonged 49.6 +/-16.3 msec. The effective refractory periods at drive cycle lengths 600, 500, and 400 msec were 407 +/- 70 msec, 320 +/- 39 msec, and 336 +/- 54 msec, respectively. Corresponding functional refractory periods were 414 +/- 62, 371 +/- 52, and 329 +/- 32. Consistent capture with incremental His pacing was possible in 50% of patients, and 1:1 His capture was lost at mean cycle length 408 +/-93 msec.

CONCLUSIONS

His refractory periods can be determined consistently in unselected individuals undergoing electrophysiological studies. Measurement of HERP and HFRP may prove useful in assessing the suitability of the His bundle for permanent pacing.

Cardiac pacing: the state of the art

Permanent cardiac pacing remains the only effective treatment for chronic, symptomatic bradycardia. In recent years, the role of implantable pacing devices has expanded substantially. At the beginning of the 21st century, exciting developments in technology seem to happen at an exponential rate. Major advances have extended the use of pacing beyond the arrhythmia horizon. Such developments include dual-chamber pacers, rate-response algorithms, improved functionality of implantable cardioverter defibrillators, combinations of sensors for optimum physiological response, and advances in lead placement and extraction. Cardiac pacing is poised to help millions of patients worldwide to live better electrically. We review pacing studies of sick-sinus syndrome, neurocardiogenic syncope, hypertrophic obstructive cardiomyopathy, and cardiac resynchronisation therapy, which are common or controversial indications for cardiac pacing. We also look at the benefits and complications of implantation in specific arrhythmias, suitability of different pacing modes, and the role of permanent pacing in the management of patients with heart failure.

Intra- and interatrial conduction delay: implications for cardiac pacing

Atrial conduction disorders are frequent in elderly subjects and/or those with structural heart diseases, mainly mitral valve disease, hyperthrophic cardiomyopathies, and hypertension. The resultant electrophysiological and electromechanical abnormalities are associated with a higher risk of paroxysmal or persistent atrial tachyarrhythmias, either atrial fibrillation, typical or atypical flutter or other forms of atrial tachycardias. Such an association is not fortuitous because intra- and interatrial conduction abnormalities delays disrupt (spatial and temporal dispersion) electrical activation, thus promoting the initiation and perpetuation of reentrant circuits. Preventive therapeutic interventions induce variable, sometimes paradoxical effects as with the proarrhythmic effect of class I antiarrhythmic drugs. Similarly, atrial pacing may promote proarrhythmias or an antiarrhythmic effect according to the pacing site(s) and mode. Multisite atrial pacing was conceived to correct, as much as possible, abnormal activation induced by spontaneous intra- or interatrial conduction disorders or by single site atrial pacing, which are situations responsible for commonly refractory arrhythmias. Atrial electrical resynchronization can also be used to correct mechanical abnormalities like left heart AV dyssynchrony resulting from intraatrial conduction delays.

Cardiac pacing device therapy for atrial dysrhythmias: how does it work?

Atrial fibrillation (AF) is the most common dysrhythmia in North America. Paroxysmal or persistent AF affects an estimated 2.8 million individuals, causes significant morbidity, and is associated with 1 billion dollars in healthcare costs each year in the United States. An aging population, the prevalence of hypertension, and the emergence of heart failure as the final common pathway of heart disease finds us in an age where the incidence of AF is ever increasing and the management challenges are indeed an expanding clinical problem. Although guidelines for selection of the appropriate pacing mode have been published, device therapy for the control of AF and paroxysmal AF is an emerging clinical management strategy. In 2001 The American College of Cardiology (ACC)/American Heart Association (AHA) published a document to revise the 1998 guidelines for device therapy, and even now these guidelines require elucidation and inclusion for the use of cardiac pacing device therapy for the control of atrial dysrhythmia. Choosing a complex system, in particular for the patient with persistent and symptomatic atrial dysrhythmia, is a most intricate challenge for the healthcare professional and the healthcare system. Rate dependent effects on refractoriness, reduction of ectopy, remodeling of the substrate, and prevention of pauses have been described as the potential mechanisms responsible for the rhythmic control effect attributed to atrial pacing. However, while permanent cardiac pacing is required for patients with symptomatic bradycardia with atrioventricular block and AF, the concept of pacing for the primary prevention of AF is novel. Pacing algorithms, single site, biatrial, and dual-site atrial pacing and site-specific pacing have all been studied as substrate modulators to prevent recurrent atrial dysrhythmia.A dilemma exists surrounding the primary approach for the control of symptomatic AF with rapid ventricular response. The question remains: should it be to maintain the sinus rhythm or to control the ventricular response rate to the AF and anticoagulate? Variations in the population studied, differences in the pacing algorithms and protocols, and a lack of definitive end points account for the variable results of the studies completed thus far. With the current data available, it appears that for individuals with sinus node dysfunction and paroxysmal AF in combination with a bradyarrhythmia indication for pacing, suppression algorithms may play an additive role with full atrial pacing in the management and reduction of episodes and burden of paroxysmal AF. The goal of these therapies is to reduce the symptoms and hopefully decrease the healthcare costs associated with paroxysmal and persistent AF with uncontrolled ventricular response.

Impact of informed consent requirements on cardiac arrest research in the United States: exception from consent or from research?

INTRODUCTION

Research in patients with life-threatening illness such as cardiac arrest is challenging since they can not consent. The Food and Drug Administration addressed research under emergency conditions by publishing new criteria for exception from informed consent in 1996. We systematically reviewed randomized trials over a 10-year period to assess the impact of these regulations.

METHODS

Case-control study of published trials for cardiac arrest (cases) and atrial fibrillation (controls.) Studies were identified by using structured searches of MEDLINE and EMBASE from 1992 to 2002. Included were studies using random allocation in humans with cardiac arrest or atrial fibrillation prior to enrollment. Excluded were duplicate publications. Number of American trials, foreign trials and proportion of trials of American origin were compared by using regression analysis. Changes in cardiac arrest versus atrial fibrillation trials were calculated as risk differences.

RESULTS

Of 4982 identified cardiac arrest studies, 57 (1.1%) were randomized trials. The number of American cardiac arrest trials decreased by 15% (95% CI: 8, 22%) annually (P = 0.05). The proportion of cardiac arrest trials of American origin decreased by 16% (95% CI: 10, 22%) annually (P = 0.006). Of 5596 identified atrial fibrillation studies, 197 trials (3.5%) were randomized trials. The risk difference between cardiac arrest versus atrial fibrillation trials being of American origin decreased significantly (annual difference -5.8% (95% CI: -10, -0.1%), P = 0.03).

INTERPRETATION

Fewer American cardiac arrest trials were published during the last decade, when federal consent requirements changed. Regulatory requirements for clinical trials may inhibit improvements in care and threaten public health.

Atrial Septal Pacing:. A New Approach to Prevent Atrial Fibrillation

Atrial pacing may prevent the onset of atrial fibrillation (AF) because of: (1) prevention of the relative bradycardia that triggers paroxysmal AF; (2) prevention of the bradycardia induced dispersion of refractoriness; (3)suppression or reduction of premature atrial contractions that initiate reentry and predispose to AF; (4) preservation of AV synchrony, which might prevent switch induced changes in atrial repolarization predisposing to AF. Atrial pacing locations that decrease atrial activation and dispersion of refractoriness may be preferable in patients with a history of AF. Two different interatrial septum sites have been proposed: the Bachmann's bundle and the coronary sinus ostium. The results of two prospective randomized studies indicate that septal pacing, when compared to the traditional right atrial appendage pacing, significantly reduces : (1) paroxysmal AF recurrences and burden; and (2) progression to chronic AF.

Device therapy for atrial fibrillation

Currently, there are more therapeutic options available for AF patients with recurrent symptomatic AF episodes. The studies on the role of device therapy for AF have been promising thus far, but they have not achieved any of the goals of AF management. Based on large randomized clinical trials, patients with SSS should receive atrial-based pacing devices. Moderate sized randomized studies have shown minimal benefit of multi-site pacing in AF prevention, even when combined with antiarrhythmic agents. Alternative site pacing such as septal pacing (high or low), however, may be more advantageous, as it achieves similar results in terms of AF reduction with less hardware. The role of ATP in AF prevention is still in its infancy and will need further studies to determine its role in conjunction with antiarrhythmic agents. Furthermore, the role of radiofrequency ablation of pulmonary veins and other sites of AF initiation has been evolving and may be offered to more patients in the future. This approach may be more acceptable to patients and may gain wider acceptance for some groups of AF patients rather than device therapy. In any event, there is still a large role for pacemaker therapy in the management of AF, especially in patients who cannot benefit from curative ablation or surgery procedures, or patients who have failed these procedures, and particularly elderly patients who typically do not undergo these procedures. Based on current understanding, careful selection of pacing sites and pacing algorithms may help in reducing AF episodes in patients receiving devices.

Total Atrioventricular Nodal Ablation Increases Atrial Fibrillation Burden in Patients with Paroxysmal Atrial Fibrillation Despite Continuation of Antiarrhythmic Drug Therapy

INTRODUCTION

Total atrioventricular nodal (TAVN) ablation and pacing is an accepted and safe treatment for patients with drug-refractory paroxysmal atrial fibrillation (AF). Many patients develop permanent AF within the first 6 months after TAVN ablation. This usually is ascribed to the cessation of antiarrhythmic drug therapy. We hypothesized that TAVN ablation itself creates an atrial substrate prone to AF.

METHODS AND RESULTS

Patients participating in the Atrial Pacing Periablation for Paroxysmal Atrial Fibrillation (PA3) study who remained on stable antiarrhythmic drug therapy throughout follow-up were included in this analysis. AF burden and the development of persistent AF in the preablation period were compared to two consecutive postablation periods. Echocardiographic changes also were evaluated. Twenty-two patients remained on stable drug therapy (9 men and 13 women, age 59 +/- 3 years). One patient developed persistent AF preablation compared to 10 postablation (P < 0.05). AF burden preablation was 3.0 +/- 1.2 hours/day and increased to 10.4 +/- 2.2 hours/day and 11.8 +/- 2.3 hours/day in the two postablation follow-up periods (P < 0.05). In patients with fractional shortening (FS) >30% prior to ablation, FS decreased significantly from 39.4% +/- 1.3% to 36.4%+/- 1.7% (P < 0.05). In contrast, in patients with a FS < or =30% prior to ablation, FS increased from 27% +/- 0.8% to 33.6 +/- 1.7% (P < 0.05).

CONCLUSION

TAVN ablation increases AF burden and facilitates the development of persistent AF in patients with paroxysmal AF despite the continuation of antiarrhythmic drugs. Loss of AV and/or interventricular synchrony may lead to altered cardiac hemodynamics resulting in atrial stretch and increasing AF burden.

Pacing to prevent atrial fibrillation

INTRODUCTION

Pacing has been proposed as a nonpharmacologic treatment option to prevent atrial tachyarrhythmias (ATs) in drug-refractory patients. This article reviews the current state of pacing to prevent ATs.

METHODS AND RESULTS

Different pacing modalities have been assessed with regard to their ability to prevent AT: conventional DDDR pacing with elevated lower rate limit, biatrial pacing, dual-site right atrial pacing, atrial septal pacing, and pacing with the use of dedicated pacing algorithms. Small studies suggest a benefit of conventional pacing for AT prevention in patients with bradycardia, but a randomized trial did not reveal any AT reduction by conventional pacing in patients without bradycardia. AT prevention by biatrial or dual-site right atrial pacing has been reported in small studies, but randomized trials did not show a clear benefit of these pacing techniques. Small studies showed a reduced AT recurrence rate in patients with septal pacing at the triangle of Koch or at Bachmann's bundle. Two large randomized trials with preventive pacing algorithms showed a significant AT reduction compared to conventional pacing, but this was not confirmed in four trials.

CONCLUSION

Pacing seems to be able to suppress ATs in a minority of patients; however, prospective identification of responders to different pacing modalities does not appear to be feasible at the present time.

AV nodal ablation and pacemaker implantation improves hemodynamic function in atrial fibrillation

In drug refractory and highly symptomatic atrial fibrillation (AF) patients, hemodynamic effects of AV node ablation and pacing therapy (APT) were evaluated. Thirty-eight patients with drug refractory and symptomatic AF, underwent APT in eight centers in Japan. The outcome of this therapy was assessed in terms of quality-of-life, cardiac performance measured by echocardiogram, and plasma ANP and BNP levels before and after APT. Quality-of-life assessed by self-administered semi-quantitative questionnaires: WHO QOL 26 (3.0 +/- 0.5 vs 3.4 +/- 0.6, P < 0.01) and the Symptom Checklist: Frequency Scale (1.6 +/- 0.6 vs 0.7 +/- 0.7, P < 0.01) and Severity Scale (1.3 +/- 0.4 vs 0.6 +/- 0.6, P < 0.01), improved significantly 6 months after APT. Ejection fraction (EF) by echocardiogram improved 1 week after APT (59.0% +/- 13.3% vs 63.3% +/- 11.6%, P = 0.02). Plasma ANP levels in the group of ANP > 40 pg/mL at enrollment significantly decreased 1 month later (P = 0.03), and plasma BNP levels in the group of BNP > 20 pg/mL at enrollment significantly decreased 1 month later (P < 0.01). In conclusion, APT has beneficial hemodynamic effects, and plasma BNP levels can predict the most optimal candidates for ablation and pacing therapy.

New approaches to atrial fibrillation management: a critical review of a rapidly evolving field

Atrial fibrillation (AF) is the most common cardiac arrhythmia, the prevalence of which is increasing with the aging of the population. Because of its clinical importance and the lack of highly satisfactory management approaches, AF is the subject of active clinical and research efforts. This paper reviews recent and on-going developments in pharmacological and non-drug management of AF. The ideal therapeutic goal for AF is the production and maintenance of sinus rhythm. Comparative studies suggest that available class I and III drugs have comparable and modest efficacy for sinus rhythm maintenance. Amiodarone, with actions of all antiarrhythmic classes, has recently been shown to have clearly superior efficacy compared with other available drugs. Newer agents are in development, but their advantages are as yet unclear and appear limited. A potentially interesting approach is the prescription of drugs upon the occurrence of an attack, rather than on a continuous basis. Recent insights into AF mechanisms may permit therapy to prevent development of the AF substrate. An alternative to sinus rhythm maintenance is a rate control approach, with no attempt to prevent AF. Drugs to effect rate control include digitalis, beta-blockers and calcium channel antagonists. Digitalis has limited value for control of exercise heart rate and for paroxysmal AF, but is particularly well suited for patients with concomitant AF and congestive heart failure. AV-nodal ablation and pacing is an effective alternative for rate control but leaves the patient pacemaker dependent. The relative merits of rate versus rhythm control are being evaluated in ongoing trials, preliminary results of which indicate no statistically significant differences in primary endpoints but highlight the risks of rhythm control therapy. In patients requiring pacemakers, physiological pacing (dual chamber devices or atrial pacing) has an advantage over purely ventricular pacemakers in AF prevention. Newer pacing modalities that produce more synchronised atrial activation, as well as pacemakers that prevent excessive atrial rate swings, show promise in AF prevention and may soon see wider use. The usefulness of automatic atrial defibrillators is presently limited by discomfort during shocks. Targeted destruction of pulmonary vein foci by radiofrequency catheter ablation suppresses paroxysmal AF. Efficacy in persistent AF is lower and still under study. Problems include potential recurrence in other veins and a small but nontrivial risk of pulmonary vein stenosis. Surgical division of the atria into zones with limited electrical connection, the MAZE procedure, is highly effective in AF prevention but is a major intervention that is not applicable to most patients. In conclusion, significant advances are being made in the management of patients with AF but much more work remains to be done.

The results of pacing trials for the prevention and termination of atrial tachyarrhythmias: is there any evidence of therapeutic breakthrough?

Atrial fibrillation (AF) is now recognized as the most prevalent sustained cardiac arrhythmia and it is associated with considerable mortality and morbidity. The demand for effective therapeutic strategies for AF has always been high and is anticipated to further increase. Anticoagulation and pharmacologic antiarrhythmic therapy or radiofrequency catheter ablation remain the mainstay of treatment for AF. Among the wide range of nonpharmacologic options which are presently being investigated, only ablation in or around the pulmonary veins and the surgical maze procedure have been shown to accomplish the aim of the curative treatment of the arrhythmia. Preventative atrial pacing and antitachycardia pacing may offer an attractive alternative option for the management of AF by either eliminating the triggers and/or by modifying the substrate of the arrhythmia. The results of several recent trials have shown a significant increase in the time to first AF recurrence, a decrease in atrial conduction time, and a trend towards reduction in AF burden, suggesting that atrial pacing may prevent AF due to improved synchronization of atrial depolarization. The recognition of potential triggers of AF, such as atrial premature complexes, short-long sequence, and bradycardia, has encouraged the development of novel atrial pacing algorithms designed to prevent the initiation of the arrhythmia on an individual basis. Observations of AF often starting with regular atrial activity consistent with atrial tachycardia have supported the hypothesis that early antitachycardia pacing may prevent progression to AF. The concept of "hybrid therapy" based on the combination of several different therapeutic strategies suggests that antitachycardia pacing therapy, integrated with an atrial defibrillator and preventative atrial pacing modes, may act synergistically to prevent AF. Dual chamber cardioverter-defibrillators with capacity to prevent and interrupt AF may offer more comprehensive and successful treatment for patients with advanced heart disease, frequent paroxysms of AF, and the risk of proarrhythmia.

Effects of septal pacing on P wave characteristics: the value of three-dimensional echocardiography

Interatrial septum (IAS) pacing has been proposed for the prevention of paroxysmal atrial fibrillation. IAS pacing is usually guided by fluoroscopy and P wave analysis. The authors have developed a new approach for IAS pacing using intracardiac echocardiography (ICE), and examined its effects on P wave characteristics. Cross-sectional images are acquired during pullback of the ICE transducer from the superior vena cava into the inferior vena cava by an electrocardiogram- and respiration-gated technique. The right atrium and IAS are then three-dimensionally reconstructed, and the desired pacing site is selected. After lead placement and electrical testing, another three-dimensional reconstruction is performed to verify the final lead position. The study included 14 patients. IAS pacing was achieved at seven suprafossal (SF) and seven infrafossal (IF) lead locations, all confirmed by three-dimensional imaging. IAS pacing resulted in a significant reduction of P wave duration as compared to sinus rhythm (99.7 +/- 18.7 vs 140.4 +/- 8.8 ms; P < 0.01). SF pacing was associated with a greater reduction of P wave duration than IF pacing (56.1 +/- 9.9 vs 30.2 +/- 13.6 ms; P < 0.01). P wave dispersion remained unchanged during septal pacing as compared to sinus rhythm (21.4 +/- 16.1 vs 13.5 +/- 13.9 ms; NS). Three-dimensional intracardiac echocardiography can be used to guide IAS pacing. SF pacing was associated with a greater decrease in P wave duration, suggesting that it is a preferable location to decrease interatrial conduction delay.

Pacemaker diagnostics: a critical appraisal of current technology

Diagnostic information retrieved from a pacemaker offers the ability to improve patient care. Pacemaker diagnostic data provides information regarding pacemaker function and activity, lead function, arrhythmia occurrence, and data to aid in optimal pacemaker programming. Current pacemakers incorporate greater storage capabilities, more efficient means of storing and presenting data between follow-up visits, and more options for programming diagnostic functions and algorithms. The cardiac rhythm of the paced patient can be evaluated via real-time intracardiac electrograms at interrogation, surface electrocardiograms, ambulatory electrocardiograms, and by pacemaker stored diagnostic function that may include stored intracardiac electrograms. This article focuses on the various methods of obtaining diagnostic information regarding pacemaker activity, pacemaker function, and diagnostic information on cardiac arrhythmias. The current clinical applicability and limitations of these methods and the use of stored diagnostic data in the clinical follow-up and study of patients with pacemakers is discussed.

Role of pacemakers in treating neurocardiogenic syncope

Patients with frequent vasovagal syncope have a poor quality of life and often resist treatment with standard pharmacologic approaches. Clinical vasovagal syncope may be associated with some degree of bradycardia. Studies of temporary pacing during tilt table tests showed that pacing prevented syncope in a little more than half of patients who developed a vasovagal response. Six open-label studies of permanent pacing show that permanent pacemaker therapy is associated with substantial improvement over medical therapy. The roles of specific pacemaker modes have not been determined, although there is some evidence that rate-drop responsiveness helps. The second Vasovagal Pacemaker Study will quantify the true benefits of pacing for vasovagal syncope and assess the role of rate-drop response algorithms.

Atrial pacing for the prevention and termination of atrial fibrillation

Atrial fibrillation (AF) affects about 2% of the general population and 8%-11% of those older than 65 years. The demand for effective therapeutic strategies for AF is anticipated to increase substantially as the proportion of the elderly population increases. Atrioventricular nodal ablation accompanied by permanent pacemaker implantation is an established option in elderly patients with intractable arrhythmia and poor ventricular rate control. However, it renders most patients pacemaker dependent and does not eliminate symptoms associated with loss of atrial transport or reduce the risk of stroke. The considerable limitations of rhythm or rate control strategies prompted interest in preventative atrial pacing, which may reduce the incidence of AF by either eliminating the triggers and/or by modifying the substrate of AF. Atrial or dual-chamber pacing has been proven to prevent or delay progression to permanent AF in elderly patients with sinus node dysfunction as compared with ventricular pacing. Patients with advanced atrial conduction delay may benefit from atrial resynchronization pacing. There may be additional benefits associated with the use of particular sites of pacing, specific pacing algorithms designed to target potential triggers of AF, and pace-termination of atrial tachycardia. Preventive and antitachycardia pacing algorithms incorporated in implantable cardioverter-defibrillators and pacemakers are currently under investigation and may offer a valuable alternative to antiarrhythmic drug therapy in elderly patients with left ventricular dysfunction at high risk of proarrhythmia or worsening heart failure. The evolution of hybrid therapy, in which two or more different strategies are employed in the same patient, may be the most effective approach to management of AF.

Improved suppression of recurrent atrial fibrillation with dual-site right atrial pacing and antiarrhythmic drug therapy

OBJECTIVES

We compared the safety, tolerance and effectiveness of overdrive high right atrial (RA), dual-site RA and support (DDI or VDI) pacing (SP) in patients with symptomatic atrial fibrillation (AF) and bradycardias.

BACKGROUND

Optimal pacing methods for AF prevention remain unclear.

METHODS

Patients (n = 118) were randomized to each of three pacing modes in a crossover trial.

RESULTS

Mode adherence was superior for dual-site RA (5.8 months) compared with SP (3.3 months; p < 0.001) and high RA pacing (4.7 months; p = 0.006). Adverse event-free survival improved with dual-site RA (p = 0.007 vs. SP) and was comparable to high RA (p = 0. 75). AF-free survival trended to improve with dual-site RA (hazard ratio [HR] 0.715, p = 0.07 vs. SP) but not high RA (HR = 0.71, p = 0.19) or when dual-site RA was compared with high RA (HR = 0.835, p = 0.175). Time-to-recurrence was longer in dual-site RA (1.77 months) compared with high RA (0.62 months, p < 0.09) or SP (0.44 months, p < 0.05). In antiarrhythmic drug-treated patients, dual-site RA reduced recurrence risk compared with SP (HR = 0.638, p = 0.011) and high RA (HR = 0.669, p = 0.06). In patients with < or =1 AF event/week, dual-site RA improved AF suppression (HR = 0.464, p = 0.004 vs. SP; HR = 0.623, p = 0.006 vs. high RA). Dual-site RA improved AF-free and mode survival (p < 0.03 vs. high RA, p < 0.001 vs. SP) and reduced asymptomatic AF (p < 0.01 vs. high RA).

CONCLUSION

Dual-site RA is safe and better tolerated than high RA and SP. In patients on antiarrhythmics, dual-site RA prolonged and high RA trended to prolong time-to-recurrent AF compared with SP. Dual-site RA provides superior symptomatic and asymptomatic AF prevention compared with high RA in patients with symptomatic AF frequency of < or =1/week.

Dual site right atrial pacing in the prevention of symptomatic atrial fibrillation refractory to drug therapy and unrelated to sinus bradycardia

Dual-site right atrial pacing has been shown recently to prevent atrial fibrillation relapses in patients affected by drug-refractory, highly-recurring tachyarrhythmia, associated to sinus bradycardia. The aim of our study was to verify whether this stimulation modality could be useful in patients affected by refractory atrial fibrillation unassociated to sinus bradycardia.

METHODS AND RESULTS

Fifteen patients (6 males) affected by refractory, symptomatic atrial fibrillation, and potential candidates to AV node ablation, were prospectively enrolled. Mean age was 65 +/- 5 years (range 62-78). Associated pathology was arterial hypertension in 12, and dilated cardiomyopathy in 3. Eight patients were affected by persistent atrial fibrillation, and seven by paroxysmal atrial fibrillation. The duration of the arrhythmia was 61 +/- 63 months (range 3-216). Left atrial diameter was 39.4 +/- 4.2 mm (range 33-46), left ventricular end-diastolic diameter was 52.4 +/- 12.2 mm (range 41-90), and left ventricular ejection fraction was 55 +/- 16 (range 18-81). Single chamber atrial pacing was used in 10 patients, dual chamber in 5 patients. The mean duration of follow up was 24 +/- 12 months (range 3-41). During this period the number of episodes of atrial fibrillation decreased from a mean of 13 +/- 38 (range 1-150) to 0.4 +/- 0.7 (range 0-2.3) per month (p < 0.001). In the subgroup of patients with persistent atrial fibrillation the number of episodes decreased from a mean of 20.4 +/- 52.4 (range 1-150) to 0.6 +/- 0.9 (range 0-2.3) (p < 0.001). In patients with paroxysmal atrial fibrillation the number of episodes decreased from 4.6 +/- 3.5 (range 2-12) to 0.2 +/- 0.5 (range 0-1.4) (p < 0.001). One patient (6.7%) developed chronic atrial fibrillation 16 months after the implant, 2 remaining patients (13%) had their arrhythmia unaltered. After the implant the number of Class 1 antiarrhythmic drugs fell from 18 to 6 (p < 0.001) and that of Class 2 changed from 0 to 7 p < 0.001). The use of Class 3 and 4 did not change significantly. No complications related to implant were observed.

CONCLUSIONS

Permanent dual-site right atrial pacing can prevent atrial fibrillation recurrences in patients affected by highly symptomatic episodes unassociated to sinus bradycardia.

Catheter ablation of inducible atrial flutter, in combination with atrial pacing and antiarrhythmic drugs ("hybrid therapy") improves rhythm control in patients with refractory atrial fibrillation

Atrial flutter or tachycardia may coexist with atrial fibrillation [AF] and can be treated with ablation techniques in attempt to reduce the total AF burden. The role of ablation of latent atrial tachyarrhythmias elicited at electrophysiologic study in conjunction with atrial pacing and antiarrhythmic drugs in patients with refractory AF has not been evaluated. We evaluated the efficacy of catheter ablation of electrically induced atrial flutter or atrial tachycardia in improving rhythm control in patients with refractory AF.

METHODS

Consecutive patients with refractory AF, and spontaneous atrial flutter (Group 1) or without spontaneous atrial flutter (Group 2) underwent programmed stimulation in a baseline drug-free state. All patients had electrically induced atrial flutter or tachycardia. Radiofrequency ablation of the arrhythmia substrate was performed in all patients. Primary endpoints evaluated for patient outcome in both groups included maintenance of rhythm control and freedom from recurrent atrial tachyarrhythmias.

RESULTS

Forty-three patients, with a mean age of 66 +/- 13 years were studied. Group 1 consisted of 22 patients while Group 2 had 21 patients. Ablation of the tricuspid valve-inferior venacaval isthmus was performed in 41 patients who had common atrial flutter induced at electrophysiologic study. Ablation of other atrial sites was performed in 8 patients with induced atypical flutter and 4 patients with induced atrial tachycardia. Ten of these patients had ablation of more than one arrhythmia. 17 patients (40%) had atrial pacing instituted and 28 patients remained on a class 1/3 antiarrhythmic drug. During a mean follow-up of 26 +/- 14 months, 33 patients (82.5%) remained in rhythm control. Actuarial analysis showed 96% of patients in rhythm control at 6 months, 94% at 12 months, and 90% at 24 months. Freedom from symptomatic AF recurrence was 64% at 6 months, 58% at 12 months, and 42% at 24 months. The outcome for both of these endpoints was similar for Group 1 and Group 2 (p = NS). The AF free interval increased significantly from 7+/- 9 days to 172 +/- 121 days (p < 0.01) after ablation. This increase was again similar in both the groups. In the 14 patients were who did not receive atrial pacing and who remained on the same class 1/3 antiarrhythmic drug, the AF free interval increased from 18 +/- 17 days to 212+/- 102 days (p < 0.01).

CONCLUSIONS

We conclude that electrophysiologic studies can elicit latent atrial flutter or tachycardia in patients with refractory AF without spontaneous monomorphic atrial tachyarrhythmias. Catheter ablation of electrically induced atrial flutter or tachycardia either alone, or with atrial pacing and with antiarrhythmic drug may improve rhythm control and reduce AF recurrences. This is similar in patients with and without spontaneous atrial flutter and refractory AF.