Dual-site atrial pacing for atrial fibrillation in patients without bradycardia

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Sinus Node Dysfunction

Sinus node dysfunction (SND) is a multifaceted disorder most prevalent in older individuals, but may also occur at an earlier age. In most cases, the SND diagnosis is ultimately established by documenting its ECG manifestations. EPS has limited utility. The treatment strategy is largely dictated by symptoms and ECG manifestations. Not infrequently, both bradycardia and tachycardia coexist in the same patients, along with other diseases common in the elderly (e.g., hypertension, coronary artery disease), thereby complicating treatment strategy. Prevention of the adverse consequences of both bradyarrhythmia and tachyarrhythmia is important to reduce susceptibility to syncope, falls, and thromboembolic complications.

Atrial Fibrillation: The New Epidemic of the Ageing World

The prevalence of atrial fibrillation (AF) increases with age. As the population ages, the burden of AF increases. AF is associated with an increased incidence of mortality, stroke, and coronary events compared to sinus rhythm. AF with a rapid ventricular rate may cause a tachycardia-related cardiomyopathy. Immediate direct-current (DC) cardioversion should be performed in patients with AF and acute myocardial infarction, chest pain due to myocardial ischemia, hypotension, severe heart failure, or syncope. Intravenous beta blockers, diltiazem, or verapamil may be administered to reduce immediately a very rapid ventricular rate in AF. An oral beta blocker, verapamil, or diltiazem should be used in persons with AF if a fast ventricular rate occurs at rest or during exercise despite digoxin. Amiodarone may be used in selected patients with symptomatic life-threatening AF refractory to other drugs. Digoxin should not be used to treat patients with paroxysmal AF. Nondrug therapies should be performed in patients with symptomatic AF in whom a rapid ventricular rate cannot be slowed by drugs. Paroxysmal AF associated with the tachycardia-bradycardia syndrome should be treated with a permanent pacemaker in combination with drugs. A permanent pacemaker should be implanted in patients with AF and symptoms such as dizziness or syncope associated with ventricular pauses greater than 3 seconds which are not drug-induced. Elective DC cardioversion has a higher success rate and a lower incidence of cardiac adverse effects than does medical cardioversion in converting AF to sinus rhythm. Unless transesophageal echocardiography has shown no thrombus in the left atrial appendage before cardioversion, oral warfarin should be given for 3 weeks before elective DC or drug cardioversion of AF and continued for at least 4 weeks after maintenance of sinus rhythm. Many cardiologists prefer, especially in elderly patients , ventricular rate control plus warfarin rather than maintaining sinus rhythm with antiarrhythmic drugs. Patients with chronic or paroxysmal AF at high risk for stroke should be treated with long-term warfarin to achieve an International Normalized Ratio of 2.0 to 3.0. Patients with AF at low risk for stroke or with contraindications to warfarin should be treated with aspirin 325 mg daily.

The place of hybrid therapies with drugs to supplement nonpharmacological therapies in atrial fibrillation

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias, and its prevalence continues to rise as the aged population increases. Comparative studies of rhythm control and rate control have been equivocal; however, the benefits of rhythm control may have been offset by the limitations of antiarrhythmic drugs. More recently, nonpharmacological therapies have emerged that provide hope of more effective rhythm control. Catheter ablation techniques have gained favour with high success rates in specialized centers, although these techniques are not without complications and require considerable expertise. Pacing therapies designed to reduce harmful right ventricular pacing and increase physiological pacing have shown benefit in AF patients with bradycardia. Despite this progress, no single modality confers benefit for all patients. Strategies to combine these treatment modalities in a hybrid approach has shown increasing promise for subgroups of AF patients.

Etiology, pathophysiology, and treatment of atrial fibrillation: part 1

Atrial fibrillation (AF) is associated with a higher incidence of mortality, stroke, and coronary events than is sinus rhythm. AF with a rapid ventricular rate may cause a tachycardia-related cardiomyopathy. Immediate direct-current cardioversion should be performed in patients with AF and acute myocardial infarction, chest pain due to myocardial ischemia, hypotension, severe heart failure, or syncope. Intravenous beta blockers, verapamil, or diltiazem may be given to immediately slow a very rapid ventricular rate in AF. An oral beta blocker, verapamil, or diltiazem should be used in persons with AF if a fast ventricular rate occurs at rest or during exercise despite digoxin. Amiodarone may be used in selected patients with symptomatic life-threatening AF refractory to other drugs. Digoxin should not be used to treat patients with paroxysmal AF. Nonpharmacologic therapies should be used in patients with symptomatic AF in whom a rapid ventricular rate cannot be slowed by drugs. This is part 1 of a 2-part review of the etiology, pathophysiology, and treatment of atrial fibrillation. The second part will be published in the subsequent issue of Cardiology in Review.

Bifocal versus unifocal right atrial pacing under plasma level controlled sotalol to prevent atrial fibrillation in patients with symptomatic sinus bradycardia and paroxysmal atrial fibrillation

AIMS

Bifocal right atrial pacing (BP) has been reported to increase arrhythmia-free intervals in patients with paroxysmal atrial fibrillation (PAF) under antiarrhythmic drugs. This study compares AF burden with unifocal pacing (UP) vs BP under sotalol.

METHODS

In 19 patients with PAF a DDDR pacemaker with right atrial lateral and CS ostial leads was implanted. Sotalol was initiated. After a 3 month back-up pacing period patients were randomized to continuous UP or BP for 3 months and crossed over for 3 more months. Primary endpoint was AF burden. Secondary endpoints included number of episodes, time to first recurrence and safety of BP.

RESULTS

The intention to treat analysis revealed 12.4% AF during back-up, 6.2% during UP and BP (p=0.91 UP vs BP, p=0.08 back-up vs UP and p=0.07 back-up vs BP). Per protocol analysis showed no advantage of either pacing mode (UP 4.8% and BP 5.4% AF, p=0.64). Overdrive pacing reduced AF burden to 6.2 vs 8.8% during back-up (p=0.09). Septal lead dislodgement occurred in 3 patients.

CONCLUSION

Atrial pacing tends to reduce AF burden in patients with PAF under sotalol. An incremental effect of BP vs UP cannot be confirmed. BP may be complicated by elevated lead dislodgement rates.

Management of atrial fibrillation

Atrial fibrillation is the most common sustained cardiac rhythm disorder, and confers a substantial mortality and morbidity from stroke, thromboembolism, heart failure, and impaired quality of life. With the increasingly elderly population in the developed world, as well as improvements in the management of myocardial infarction and heart failure, the prevalence of atrial fibrillation is increasing, resulting in a major public-health problem. This Review aims to provide an overview on the modern management of atrial fibrillation, with particular emphasis on pharmacological and non-pharmacological approaches. Irrespective of a rate-control or rhythm-control strategy, stroke prevention with appropriate thromboprophylaxis still remains central to the management of this common arrhythmia. Electrophysiological approaches could hold some promise for a curative approach in atrial fibrillation.

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.

Pharmacotherapy changes following pacemaker implantation in patients with bradycardia-tachycardia syndrome

The management of bradycardia-tachycardia syndrome (BTS) includes bradycardia and tachyarrhythmia therapy. At present, the treatment for symptomatic bradycardia in BTS patients is permanent cardiac pacing. The pharmacological treatment of atrial tachyarrhythmias comprises of rhythm and rate control, and prevention of thromboembolism. Patients with BTS often require both pacemaker and drug therapy. This article reviews the interactions of pacing and drug therapies in BTS. Drugs that alter cardiac electrophysiological properties may influence pacemaker indications, pacing mode selection, efficacy of pacing algorithms and pacing performance. Pacing by preventing drug-induced bradycardia increases the safety of pharmacotherapy and, thus, allows the intensification of those treatments. Pacing therapy and antiarrhythmic drugs used together as a hybrid therapy have a synergistic effect in the prevention of atrial tachyarrhythmias. Atrial-based pacing may reduce atrial tachyarrhythmia burden, allowing reduction of rhythm and rate control. Contemporary pacemakers' memory functions may help guide rhythm and rate control, as well as anticoagulation pharmacotherapy.

Effectiveness of triple-site triggered atrial pacing for prevention of atrial fibrillation after coronary artery bypass graft surgery

BACKGROUND

Recently, several temporary multisite pacing methods have been developed for prevention of postoperative atrial fibrillation (AF).

HYPOTHESIS

In this study, we evaluated the effect of triple-site temporary triggered pacing in the AAT mode on the development of AF in patients undergoing coronary artery bypass graft (CABG) at high risk for developing postoperative AF.

METHODS

A total of 70 patients undergoing CABG were randomly assigned either to pacing group (study group, n = 35 patients) or to no pacing group (control group, n = 35 patients). The external pacemaker was programmed to pace at the atrial triggered mode at a lower rate of 40 beats/min for 4 days.

RESULTS

Atrial fibrillation, defined as lasting > 30 s, occurred in 4 patients (11.4%) in the study group and in 16 patients (45.7%) in the control group (p = 0.003). Sustained AF, defined as AF lasting > 10 min, also was observed less frequently in the study group than in the control group (11.6 vs. 37.1%, p = 0.024). Triple-site triggered atrial pacing was observed to reduce the incidence of AF by 75% and the incidence of sustained AF by 69%.

CONCLUSIONS

We believe that multiple-site temporary pacing in the triggered mode is an effective way of preventing postoperative AF. This technique may be used especially in patients at high risk of developing AF.

Bachmann's Bundle: Does It Play a Role in Atrial Fibrillation?

BACKGROUND

Cardiac anatomists have known the presence of a group of specialized fibers connecting the right and left atrium for years. However, only recently have clinical cardiologists come to recognize the potential importance of this specialized conduction system. Anatomical and microscopic studies have shown that the Bachmann's bundle (BB) represents a distinct structure similar to the atrio-ventricular node and the His-Purkinje conduction system but without any insulating tissue.

RESULTS

BB cells have specialized electrophysiological properties like supernormal excitability and faster longitudinal conduction that can facilitate more rapid impulse transmission compared to the normal atrial tissue. Experimental blockage of this pathway causes prolongation and widening of the P wave, which is associated with an increased incidence of atrial fibrillation. Atrial pacing is effective in reducing the incidence of atrial fibrillation by preventing bradycardia, synchronizing the atria, limiting anisotropy and reducing the dispersion of refractoriness. Various animal and human studies have shown pacing near the right atrial insertion of BB to have a beneficial effect in patients with interatrial conduction delay and atrial tachyarrhythmias. This mode of atrial septal pacing is convenient, safe, reliable, and clinically as effective as multisite pacing.

CONCLUSION

This article is an effort to define the special properties of BB and its possible role in prevention of atrial fibrillation by permanent pacemakers.

Dual Site Right Atrial Pacing can Improve the Impact of Standard Dual Chamber Pacing on Atrial and Ventricular Mechanical Function in Patients with Symptomatic Atrial Fibrillation: Further Observations from the Dual Site Atrial Pacing for Prevention of Atrial Fibrillation Trial

BACKGROUND

The effects of atrial pacing mode on atrial and ventricular function in patients with atrial fibrillation (AF) and bradycardia have not been evaluated. We evaluated atrial and ventricular function during randomization to support pacing (SP), high right atrial pacing (HRA), and dual site right atrial pacing (DAP).

METHODS

Seventy-nine patients (66 +/- 12 yr, 46 male) with standard pacing indications and symptomatic AF were randomized to each of three pacing modes (DAP, HRA, SP) for 6 months in a crossover design. Echocardiographic studies were performed at enrollment and the end of each mode. Paired comparisons of atrial and ventricular function parameters were performed between each pacing mode and baseline.

RESULTS

HRA pacing in DDDR mode resulted in increased left ventricular (LV) end systolic volume (78 +/- 42 vs. 60 +/- 31 ml, p = 0.001) and reduced LV ejection fraction (44 +/- 14 vs. 50 +/- 11%, p = 0.007) compared to baseline. These parameters did not change during DAP. DAP resulted in increased peak A wave velocity (75 +/- 19 vs. 63 +/- 23 cm/s, p = 0.003) and atrial filling fraction compared to baseline (0.47 +/- 0.15 vs. 0.38 +/- 0.13, p = 0.005). Atrial and ventricular function were similar between control and SP.

CONCLUSION

DAP, but not HRA or SP, improved left atrial (LA) function in patients with AF and bradycardia. HRA pacing in DDDR mode resulted in LA dilatation and deterioration of LV function which was not observed with DAP.

Reducing atrial tachycardia and atrial fibrillation episodes with a prevention and treatment device and tailored treatment

BACKGROUND

Pacemaker treatment of known trigger mechanisms for atrial tachyarrhythmias (AT) and atrial fibrillation (AF) has shown reduction in the incidence of AF. A new arrhythmia management device, which included storage of AT/AF (for tailoring treatment) and three prevention algorithms and one for treatment, was examined in order to identify the influence on arrhythmia episodes over a 12-month follow-up (FU) period.

METHODS

Twenty-three consecutive patients with known tachybradyarrhythmias were examined. Seven patients had to be excluded (two outliers, four developed permanent AF, one had no detection algorithm turned on at implantation). The remaining 16 patients showed 2723 episodes (675 treated episodes) for evaluation of the effect on episodes/month/patient (e/m/p), treatment success, duration of episodes, circadian distribution and quality of life.

RESULTS

The AT/AF e/m/p were reduced from 37 +/- 102 e/m/p at 1-month FU to 16 +/- 48 e/m/p at 3-month FU, 15 +/- 48 e/m/p at 6-month FU and 10 +/- 28 e/m/p at 12-month FU (p < 0.05), according to fewer subjective symptoms. Treatment success remained stable during the observation period (29-40%). Only minor changes in the duration of episodes and the distribution of start times were observed.

CONCLUSION

Tailoring treatment by the pacemaker examined with several prevention and treatment algorithms reduces e/m/p and might be a promising supplement in the treatment of selected patients with known AT/AF and bradycardia.

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.

[The role of cardiac pacing in atrial arrhythmia prevention]

Pathophysiological considerations, animal data and acute clinical tests suggest some benefit of cardiac pacing in the prevention of paroxysmal atrial tachyarrhythmia. While early clinical studies confirm this notion, data of randomized prospective trials at least are mixed. The equivocal effects of using alternative atrial pacing sites and/or dedicated preventive pacing algorithms leaves the question of how to predict the beneficial effect of antitachycardia pacing strategies in the individual patient. Since the answer is lacking, the mere intention to prevent atrial arrhythmias is not a valid pacing indication. Pacing for the bradycardia tachycardia syndrome, however, may benefit from preventive techniques in individual cases.

Quality of life restored to normal in patients with atrial fibrillation after pulmonary vein ostial isolation

BACKGROUND

Pulmonary vein isolation (PVI) is effective in patients with paroxysmal atrial fibrillation. However, its impact on quality of life (QOL) is not completely understood.

METHODS

Eighty-nine otherwise healthy patients (74 men; age, 53 +/- 11 years) were selected for PVI. The Medical Outcomes Short Form 36 (SF-36) and the Symptom Checklist (SCL) QOL questionnaires were obtained before PVI and for as long as 6 months after PVI.

RESULTS

A total of 294 PVs (3.3 PVs/patient) were targeted in 125 procedures (1.4/patient). After a mean follow-up period of 191 +/- 109 days, scores for SCL frequency (19.09 +/- 8.07 vs 10.67 +/- 6.61), SCL severity (15.97 +/- 7.68 vs 9.72 +/- 5.98), SF-36 physical composite (45.43 +/- 9.70 vs 51.70 +/- 6.52), and SF-36 mental composite (44.50 +/- 11.33 vs 51.67 +/- 8.73) improved significantly (P <.0001 each). Seventy-five patients provided data at both the baseline and a late (3- or 6-month) follow-up. This cohort had significantly worse QOL scores in 7 of the 8 SF-36 subscales at baseline compared with age-matched healthy control subjects, but their QOL scores were similar to a comparison group of 152 previously reported patients with atrial fibrillation receiving drug treatment who had similar demographic and clinical variables. After PVI, patients improved significantly, resulting in equivalence with the healthy control population. Logistic regression analysis of demographic variables and baseline QOL scores revealed no significant predictors of PVI responders.

CONCLUSIONS

QOL measures in patients with paroxysmal atrial fibrillation are severely depressed before PVI. Within a 6-month follow-up period after ablation, SF-36 subscale scores were restored to equivalence with an age-matched, healthy control population. Neither demographic or clinical variables nor baseline QOL scores were predictive of response to PVI.

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.

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.

Randomized Trials for Selective Site Pacing:. Do We Know Where We Are Going?

Clinical evidence is accumulating that pacing from traditional right-sided sites (right ventricular apex and right atrial appendage) may be associated with long-term detriment to left ventricular function and promotion of atrial arrhythmias. Large numbers of small studies, some randomized, have addressed the effects of pacing from nontraditional or alternate sites, but the studies have varied in design such that comparison of results is often difficult. Many studies show data from acute studies only, although more recently longer-term data have started to become available; definition and description of pacing site also varies, adding further to the difficulties in comparing data. This article attempts to examine the randomized studies available to date, and to consider how future studies may contribute to our understanding of the effects of pacing from traditional and selected, specific sites on the right side of the heart.

Left Atrial Vein Pacing:. A Technique of Biatrial Pacing for the Prevention of Atrial Fibrillation

Biatrial pacing is a promising new therapy for drug refractory AF. This article reports two studies. First, an initial 14-patient experience with a novel technique for biatrial pacing. The authors attempted to pace from the LA vein branches of the proximal CS for LA stimulation. LA vein pacing would potentially offer the advantages of greater interatrial synchronization and possibly greater reduction in AF burden and also of lesser far-field R wave sensing and greater lead stability. Second, a postmortem series examining the number, size, and site of LA veins draining into the proximal CS is described. LA vein pacing was successful in 9 of 14 patients. LA vein electrode parameters have been stable during a median follow-up of 580 days. There were three early lead dislodgments but no other complications. In the second study, a postmortem analysis of 43 human hearts was performed. The study found that 38 (88.4%) of 43 hearts had at least one LA vein draining into the proximal 5 cm of the CS. In addition, 81.2% (33/43) had at least one vein greater than 4 Fr caliber. Thus, pacing in a greater proportion of patients might be achieved by the development and use of smaller (3, 4, and 5 Fr) electrodes. Furthermore, these smaller leads would obviously allow deeper advancement into the LA veins with the potential advantages of greater interatrial synchronization and lead stability and lesser far-field R wave sensing.

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.

Hybrid therapy of atrial fibrillation: algorithms and outcome

Rhythm control methods have not shown superior outcomes to rate control strategies in atrial fibrillation. Newer approaches to rhythm control employ "hybrid" therapies combining pharmacologic and non pharmacologic interventions. Pathophysiologic insights into mechanisms of atrial fibrillation (AF) suggest that arrhythmogenesis is due to interactions of multiple triggering rhythms and a complex electrophysiologic substrate resulting in the emergence of multiple tachyarrhythmias, often in disparate locations that may coexist in time. Thus, an "hybrid" therapy prescription is more likely to address several of the etiologic factors culminating in clinical AF. Results of pilot clinical studies of hybrid therapy are encouraging and involve drugs, devices and ablation techniques in varying permutations. Hybrid therapy algorithms using right heart procedures can improve efficacy with potentially lower risk. Considerations in implementation of these algorithms include staged or simultaneous interventions and a right versus left heart strategy. The parallel with the current coronary disease management paradigm is obvious and relevant.

Combined Efficacy of Atrial Septal Lead Placement and Atrial Pacing Algorithms for Prevention of Paroxysmal Atrial Tachyarrhythmia

INTRODUCTION

The combined role of atrial septal lead location and atrial pacing algorithms in the prevention of atrial tachyarrhythmias (AT/AF), including both atrial fibrillation and flutter, is unknown. We tested the hypothesis that atrial prevention pacing algorithms could decrease AT/AF frequency in patients with atrial septal leads, bradycardia, and paroxysmal AT/AF.

METHODS AND RESULTS

A total of 298 patients (age 70 +/- 10 years; 61% male) from 35 centers were implanted with a DDDRP pacing system including three AT/AF prevention pacing algorithms. Lead site was randomized at implant to right atrial septal or nonseptal. Patients were randomized 1 month postimplant to AT/AF prevention ON or OFF for 3 months and then crossed over for 3 months. Patients logged symptomatic AT/AF episodes via a manual activator. Prevention efficacy was evaluated based on intention-to-treat in 277 patients (138 septal) with complete follow-up. No changes in device-recorded AT/AF frequency or burden were observed with algorithms OFF versus ON or between patients randomized to septal versus nonseptal lead location. Analysis of other secondary outcomes revealed that AT/AF prevention pacing resulted in decreased atrial premature contractions in both the septal (1.9 [0.2-8.7] vs 3.3 [0.3-10.6]x 103/day; P < 0.01) and nonseptal groups (0.9 [0.2-3.3] vs 1.3 [0.3-5.5]x 103/day; P < 0.001). Patients with septal leads had fewer symptomatic AT/AF episodes ON versus OFF (1.4 +/- 3.0 vs 2.5 +/- 5.2/month, P = 0.01).

CONCLUSION

The combination of three atrial prevention pacing algorithms did not decrease device classified atrial tachyarrhythmia frequency or burden during a 3-month cross-over period in bradycardic patients and septal or nonseptal atrial pacing leads. Prevention pacing was associated with decreased frequency of premature atrial contractions and with decreased symptomatic atrial tachyarrhythmia frequency in patients with atrial septal leads.

Rationale and patient selection for "hybrid" drug and device therapy in atrial and ventricular arrhythmias

Three quite different forms of direct antiarrhythmic therapy are available for the treatment of cardiac arrhythmias: antiarrhythmic drugs, cardiac ablation and implantable devices (pacemakers and defibrillators). None of these therapies is fully effective and consequently they are increasingly combined. This combination therapy is often described as "hybrid" a term that implies fundamental different qualities of treatment which together provide some form of synergism. The mechanisms for the initiation and perpetuation of most cardiac arrhythmias are complex and multiple. It is therefore not surprising that single therapies are not completely effective. Theoretically the use of multiple different therapies allows more specific mechanisms of arrhythmia to be directly addressed. However, this is largely a theoretical concept that has only been strictly evaluated in a small number of studies. Studies of multiple therapies are difficult to perform unless the combination therapy is regarded as a strategy which can be compared to baseline, conventional treatment or one or more single constituent therapies from the combination. Despite the lack of formal studies there is a very substantial clinical experience which testifies to the value of hybrid therapy for the management of both atrial fibrillation and ventricular tachycardia/fibrillation.

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.

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.

Atrial pacing lead location alters the hemodynamic effects of atrial-ventricular delay in dogs with pacing induced cardiomyopathy

The role of atrial lead location in cardiovascular function in the presence of impaired ventricular dysfunction is unknown. We tested the hypothesis that left atrial (LA) and left ventricular (LV) hemodynamics are affected by alterations in AV delay and are influenced by atrial pacing site in dogs with dilated cardiomyopathy. Dogs (n = 7) were chronically paced at 220 beats/min for 3 weeks to produce cardiomyopathy and then instrumented for measurement of LA, LV end diastolic pressure (LVEDP) and mean arterial pressure (MAP), LA volume, LV short-axis diameter, and aortic and pulmonary venous blood flow. Hemodynamics were measured after instrumentation and during atrial overdrive pacing from the right atrial appendage (RAA), coronary sinus ostium (CSO) and lower LA lateral wall (LAW). The AV node was then ablated, and hemodynamics were compared during dual chamber AV pacing (right ventricular apex) from each atrial lead location at several AV delays between 20 and 350 ms. Atrial overdrive pacing from different sites did not alter hemodynamics. Cardiac output (CO), stroke volume, LVEDP, MAP and +dLVP/dt demonstrated significant (P < 0.05) variation with AV delay during dual chamber pacing. CO was higher during LAW pacing than RAA and CSO pacing (2.3 +/- 0.4 vs 2.1 +/- 0.3 vs 2.0 +/- 0.3 l/min, respectively) at an AV delay of 120 ms. Also, MAP was higher in the LAW than RAA and CSO (65 +/- 9 vs 59 +/- 9 vs 54 +/- 11 mmHg, respectively) at an AV delay of 350 ms. Atrial lead location affects indices of LV performance independent of AV delay during dual chamber pacing in dogs with cardiomyopathy.

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.

Atrial fibrillation: the newest frontier in arrhythmia management

At least 2.3 million people in the United States have atrial fibrillation. Since the risk for developing atrial fibrillation increases with age, the number of people with atrial fibrillation is expected to rise sharply. Atrial fibrillation is a complex condition that adversely influences mortality, morbidity, quality of life, and use of health care resources. Knowledge generated from extensive research has led to innovative management strategies. As the number of individuals with atrial fibrillation increases and treatment options expand, nurses in a variety of settings will be challenged to respond to the multifaceted needs of this population. This review discusses the significance of atrial fibrillation and summarizes research findings influencing current management strategies. Pharmacologic therapies are reviewed and new technologies for atrial fibrillation treatment are introduced. Nursing assessment and treatment of patients' response to atrial fibrillation are discussed. Recommendations for patient education are offered. A plan describing specific nursing diagnoses, outcomes, interventions, and activities for care of patients with atrial fibrillation is presented.

Management of the older person with atrial fibrillation

Atrial fibrillation (AF) is associated with a higher incidence of mortality, stroke, and coronary events than is sinus rhythm. AF with a rapid ventricular rate may cause a tachycardia-related cardiomyopathy. Immediate direct-current (DC) cardioversion should be performed in patients with AF and acute myocardial infarction, chest pain due to myocardial ischemia, hypotension, severe heart failure, or syncope. Intravenous beta blockers, verapamil, or diltiazem may be given to slow immediately a very rapid ventricular rate in AF. An oral beta blocker, verapamil, or diltiazem should be used in persons with AF if a fast ventricular rate occurs at rest or during exercise despite digoxin. Amiodarone may be used in selected patients with symptomatic life-threatening AF refractory to other drugs. Nondrug therapies should be performed in patients with symptomatic AF in whom a rapid ventricular rate cannot be slowed by drugs. Paroxysmal AF associated with the tachycardia-bradycardia syndrome should be treated with a permanent pacemaker in combination with drugs. A permanent pacemaker should be implanted in patients with AF and with symptoms such as dizziness or syncope associated with ventricular pauses greater than 3 seconds that are not drug-induced. Elective DC cardioversion has a higher success rate and a lower incidence of cardiac adverse effects than does medical cardioversion in converting AF to sinus rhythm. Unless transesophageal echocardiography has shown no thrombus in the left atrial appendage before cardioversion, oral warfarin should be given for 3 weeks before elective DC or drug cardioversion of AF and should be continued for at least 4 weeks after maintenance of sinus rhythm. Many cardiologists prefer, especially in older persons, ventricular rate control plus warfarin rather than maintaining sinus rhythm with antiarrhythmic drugs. Digoxin should not be used to treat patients with paroxysmal AF. Patients with chronic or paroxysmal AF at high risk for stroke should be treated with long-term warfarin to achieve an International Normalized Ratio of 2.0 to 3.0. Patients with AF at low risk for stroke or with contraindications to warfarin should receive 325 mg of aspirin daily.

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.

Atrial fibrillation

The prevalence and incidence of atrial fibrillation increase with age. Atrial fibrillation is associated with a higher incidence of coronary events, stroke, and mortality than sinus rhythm. A fast ventricular rate associated with atrial fibrillation may cause tachycardia-related cardiomyopathy. Management of atrial fibrillation includes treatment of underlying causes and precipitating factors. Immediate direct-current cardioversion should be performed in persons with atrial fibrillation associated with acute myocardial infarction, chest pain due to myocardial ischemia, hypotension, severe heart failure, or syncope. Intravenous beta-blockers, verapamil, or diltiazem may be used to immediately slow a fast ventricular rate associated with atrial fibrillation. An oral beta-blocker, verapamil, or diltiazem should be given to persons with atrial fibrillation if a rapid ventricular rate occurs a rest or during exercise despite digoxin. Amiodarone may be used in selected persons with symptomatic life-threatening atrial fibrillation refractory to other drug therapy. Nondrug therapies should be performed in persons with symptomatic atrial fibrillation in whom a rapid ventricular rate cannot be slowed by drug therapy. Paroxysmal atrial fibrillation associated with the tachycardia-bradycardia syndrome should be managed with a permanent pacemaker in combination with drugs. A permanent pacemaker should be implanted in persons with atrial fibrillation in whom symptoms such as dizziness or syncope associated with non-drug-induced ventricular pauses longer than 3 seconds develop. Elective direct-current cardioversion has a higher success rate and a lower incidence of cardiac adverse effects than medical cardioversion in converting atrial fibrillation to sinus rhythm. Unless transesophageal echocardiography shows no thrombus in the left atrial appendage before cardioversion, oral warfarin should be given for 3 weeks before elective direct-current or drug cardioversion of atrial fibrillation and continued for at least 4 weeks after maintenance of sinus rhythm. Many cardiologists prefer the treatment strategy of ventricular rate control plus warfarin rather than to maintain sinus rhythm with antiarrhythmic drugs, especially in older patients. Digoxin should not be used in persons with paroxysmal atrial fibrillation. Patients with chronic or paroxysmal atrial fibrillation who are at high risk for stroke should be treated with long-term warfarin to achieve an International Normalized Ratio (INR) of 2.0 to 3.0. Persons with atrial fibrillation who are at low risk for stroke or who have contraindications to warfarin should receive 325 mg aspirin daily.