Assessment of atrioventricular junction ablation and DDDR mode-switching pacemaker versus pharmacological treatment in patients with severely symptomatic paroxysmal atrial fibrillation: a randomized controlled study

Long-term follow-up after atrioventricular nodal ablation and pacing: low incidence of sudden cardiac death

Sudden cardiac death (SCD) has been reported in patients with drug refractory AF who underwent AV nodal ablation and pacing. However, whether SCD in these patients is related to the underlying heart disease or to the ablating and pacing procedure remains uncertain. Between May 1987 and January 1997, AV nodal ablation was performed in 585 patients (mean age 66 +/- 11 years) with drug-resistant, paroxysmal (n = 308) or chronic (n = 277) AF in 12 Italian centers. Lone AF was present in 133 patients. After AV junction ablation, patients underwent VVIR (454 patients) or DDDR (131 patients) pacemaker implantation. At a follow-up of 33.6 +/- 24.2 months, 80 (13.7%) deaths were recorded: 40 noncardiac, 23 nonsudden, and 17 sudden cardiac death (3%, 1.04% per year). Among five variables, including age. NYHA functional class, presence of heart disease, paroxysmal or chronic AF, previous embolic events, and LVEF, the presence of heart disease (P = 0.007) and a LVEF < 0.45, (P = 0.003) were associated with a higher risk of SCD. Analysis of SCD-free survival by log-rank test showed a higher incidence of SCD in patients with LVEF < 0.45 (P = 0.0001) and with coronary artery disease (P = 0.005). In this large cohort, a low incidence of long-term SCD after AV nodal ablation and pacing for drug-refractory AF was observed. The presence of underlying heart disease and the extent of baseline LV dysfunction were associated with an increased likelihood of SCD.

The impairment of health-related quality of life in patients with intermittent atrial fibrillation: implications for the assessment of investigational therapy

OBJECTIVES

We sought to assess the impact of intermittent atrial fibrillation (AF) on health-related quality of life (QoL).

BACKGROUND

Intermittent AF is a common condition with little data on health-related QoL questionnaires to guide investigational therapies.

METHODS

Outpatients from four centers, with documented AF (n = 152), completed validated QoL questionnaires (Medical Outcomes Study Short Form 36 [SF-36], Specific Activity, Symptom Checklist, Illness Intrusiveness and University of Toronto AF Severity Scales). Comparison groups were made up of healthy individuals (n = 47) and four cardiac control groups: published (n = 78) and created for study (n = 69) percutaneous transluminal coronary angioplasty (PTCA); published heart failure (n = 216) and published postmyocardial infarction (MI) (n = 107).

RESULTS

Across all domains of the SF-36, AF patients reported substantially worse QoL than healthy controls (1.3 to 2.0 standard deviation units), with scores of 24%, 23%, 16% and 30% lower than healthy individuals on measures of physical and social functioning, mental and general health, respectively (all p < 0.001). Patients with AF were either significantly worse (p < 0.05, published controls) or as impaired (study controls) as either PTCA or post-MI patients on all domains of the SF-36 and the same as heart failure controls on SF-36 psychological subscales. Patients with AF were as impaired or worse than study PTCA controls on measures of illness intrusiveness, activity limitations and symptoms. Associations between objective disease indexes and subjective QoL measures had poor correlations and accounted for <6% of the total variability in QoL scores.

CONCLUSIONS

Quality of life is as impaired in patients with intermittent AF as in patients with significant structural heart disease. Patients' perception of QoL is not dependent on the objective measures of disease severity that are usually employed.

Ablate and pace for drug refractory paroxysmal atrial fibrillation. Is ablation necessary?

BACKGROUND

Atrio-ventricular junctional ablation with pacemaker insertion has been shown to improve quality of life in patients with drug refractory paroxysmal atrial fibrillation. It is unknown whether this improvement is secondary to the ablation procedure or to the pacemaker mode utilised. To investigate this we reviewed our experience of implanting a dual chamber rate responsive pacemaker with mode switching (DDDR/MS) alone on quality of life in this patient group.

METHODS AND RESULTS

Over a 1-year period, 19 patients (mean age 62+/-9 years, 13 female) with drug refractory paroxysmal atrial fibrillation (mean duration of symptoms 8.7+/-7 years, failed 3.1+/-0.9 anti-arrhythmic drugs, amiodarone in 15) were recruited. Quality of life was assessed at baseline and after 1 month using a cardiac specific questionnaire, the modified Karolinska questionnaire. The mean score for all patients significantly improved by 39% at follow up (baseline 59+/-24, 1 month 36+/-24, P=0.001). Individually 15 patients (79%) had an improvement in their score, whilst for 13 patients (68%) their symptoms were sufficiently improved after pacing that ablation was not required. The benefit was maintained to a mean follow up of 12+/-5 months (score 31+/-20, P<0.001). Six patients remained symptomatic after pacing and requested further treatment. Benefit was unrelated to symptoms at baseline or the number and total duration of paroxysmal atrial fibrillation episodes recorded on pacemaker Holter.

CONCLUSIONS

Patients with drug refractory paroxysmal atrial fibrillation, DDDR/MS pacing alone can improve quality of life without concurrent atrio-ventricular junctional ablation in a significant proportion of patients.

Management of arrythmias

The management of arrhythmias in elderly patients with congestive heart failure, including atrial fibrillation, ventricular tachyarrhythmias, and bradyarrhythmias, is described. Patients with atrial fibrillation can be treated with rate control anticoagulation for stroke prevention or by attempt at cardioversion and maintenance of sinus rhythm. Elderly patients remaining in atrial fibrillation benefit from anticoagulation provided that no contraindication exists. In patients surviving malignant ventricular arrhythmias, defibrillator implantation is beneficial in elderly patients with heart failure. Prognosis and treatment of nonsustained arrhythmias depends on the presence of underlying cardiac abnormalities. In the healthy elderly population, treatment is not indicated. In patients with coronary artery disease, decreased ejection fraction, and nonsustained ventricular tachycardia, electrophysiology can further stratify risk, and defibrillator implantation can improve survival if arrhythmias are induced. This benefit is as great in elderly patients as in younger patients. Symptomatic bradycardias are increasingly common with advancing age. Symptoms are improved with pacing, with maximum benefit from physiologic rather than ventricular pacing. Although the elderly population poses a unique challenge when faced with arrhythmias, an active approach not only saves lives but also reduces morbidity.

Appropriate outcome measures in trials evaluating treatment of atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is a widespread disease that has only recently received the focused attention of arrhythmia specialists despite being the most frequently occurring significant cardiac arrhythmia.

METHODS AND RESULTS

The wide variety of trial designs used to evaluate AF treatment is a reflection of the diverse outcomes associated with this condition. The best trials assess the impact of treatment on a clearly measured outcome that is of clinical relevance to patients. This review discusses the different designs of AF treatment trials and analyzes the utility of the various outcomes that can be assessed.

CONCLUSIONS

A sensible goal of AF treatment is to reduce the frequency of recurrences and to prolong the time between them. The most appropriate trials focus on AF recurrences that are symptomatic and therefore relevant to the patient. We still do not know if there is value in AF prevention, beyond preventing symptoms. However, ongoing and future studies will show whether AF suppression reduces the longer-term risks of stroke or death and improves patient quality of life. Cost of care will increasingly be studied in future trials of AF management.

Management of atrial tachyarrhythmias in patients with implantable devices

The incidence of atrial fibrillation in patients with conduction system disease is high and the management of patients with pacemakers and atrial fibrillation is discussed. The use of mode switch algorithms to avoid tracking of atrial arrhythmias is explained in detail and programming and evaluation of different mode switch algorithms is presented.

The AFFIRM trial: main trial and substudies-what can We expect?

The clinical categorization of patients who present with atrial fibrillation is a major determinant of the most appropriate strategy for rhythm management. For those patients with recurrent atrial fibrillation that has not become permanent the two available strategies are rhythm control and anticoagulation or rate control and anticoagulation. There is no clear evidence that one of these strategies is superior to the other. In the AFFIRM trial these two strategies are being compared to one another in a randomized trial. Patients are randomly assigned to one of the two strategies and the treating physician then uses therapies from an approved menu as clinically indicated. Both pharmacologic and nonpharmacologic therapies are used. An overview of the main study protocol is presented. The primary endpoint is total mortality but there are a number of clinically important secondary endpoints. Several substudies will explore important ancillary questions and some of these are also described. At this time over 3000 patients have been enrolled and the planned enrollment is 4300. Enrollment will end late in 1999 and the last patient enrolled will be followed for two years. The AFFIRM Trial will provide important information concerning the management of atrial fibrillation in a large portion of the patients who have this arrhythmia.

Thromboembolism after atrioventricular node ablation and pacing: long term follow up

OBJECTIVE

To assess the incidence of arterial embolic events in patients with high rate, drug resistant, severely symptomatic paroxysmal and chronic atrial fibrillation who have undergone atrioventricular (AV) node ablation and permanent pacing.

DESIGN

Multicentre retrospective cohort study. PATIENTS AND MANAGEMENT: From May 1987 to January 1997, AV node ablation was performed in 585 severely symptomatic patients (mean (SD) age 66 (11) years) with high rate, drug resistant paroxysmal atrial fibrillation (308) or chronic atrial fibrillation (277). Lone atrial fibrillation was present in 133 patients, while the remaining 452 suffered from dilated, ischaemic, or valvar heart disease. Patients underwent VVIR (454) or DDDR (131) pacemaker implantation, after AV node ablation. Antiplatelet agents were given to 202 patients, warfarin to 187 patients.

RESULTS

During a follow up of 33.6 (24.2) months, thromboembolic events were observed in 17 patients (3%); the actuarial occurrence rates of thromboembolism were 1.1%, 3%, 4.2%, and 7.4% after one, three, five, and seven years, respectively. Among five variables, univariate analysis showed that only the presence of chronic atrial fibrillation at the time of ablation (relative risk (RR) = 1.8, 95% confidence interval (CI) = 1.02 to 3. 20, p = 0.04) and the need for warfarin treatment (RR = 1.6, 95% CI 1.00 to 2.71, p = 0.048) were associated with a significantly higher risk of occurrence of thromboembolic events. On multivariate analysis the only predictor of embolic events during the follow up was the presence of chronic atrial fibrillation.

CONCLUSIONS

Data from this large cohort of patients indicate a fairly low incidence (1.04% per year) of thromboembolic events after AV node ablation and pacing for drug refractory, high rate atrial fibrillation.

Prolonged QT interval and altered QT/RR relation early after radiofrequency ablation of the atrioventricular junction

This study evaluated the paced QT interval in the days after radiofrequency ablation of the atrioventricular junction in patients with chronic rapid atrial fibrillation. There is an abnormality in the dynamics of the paced QT interval until the second day after ablation, resulting in an increased duration when the paced heart rate is <75 beats/min.

Radiofrequency ablation of atrioventricular junction and pacemaker implantation versus modulation of atrioventricular conduction in drug refractory atrial fibrillation

Modulation of atrioventricular (AV) node conduction and radiofrequency ablation of AV junction are alternative approaches to control ventricular rate in drug refractory atrial fibrillation (AF). In 2 centers, 120 patients were treated either with AV junction ablation (center 1, group 1, 60 patients [30 men, aged 64 +/- 11 years], paroxysmal AF in 24 patients) or with modulation (group 2, 60 patients [32 men, aged 58 +/- 12 years], paroxysmal AF in 43 patients). In group 1, complete AV block was achieved in all patients. In group 2, the procedure was performed in sinus rhythm (30 patients), prolonging the Wenckebach cycle length from 328 +/- 85 to 466 +/- 80 ms (p <0.01) or during AF (30 patients), decreasing ventricular rate from 178 +/- 35 to 96 +/- 35 beats/min (p <0.01), and to <100 beats/min in 17 patients (61%). Complete AV block was induced in 9 of 60 patients (15%). In groups 1 and 2, at a follow-up of 27 +/- 7 and 26 +/- 6 months, there were 2 deaths (1 cardiac, 1 sudden death) and 1 death for end-stage heart failure, respectively. Hospital readmissions decreased from 3.2 to 0.2 and from 4.2 to 0.2/year; late AF recurrences at of >120 beats/min were documented in 6% and 12%, respectively. Symptom score analysis including effort and rest dyspnea, exercise intolerance, weakness, and palpitation showed a significant improvement in both treatment groups, when acutely effective, in patients with paroxysmal and/or chronic AF. In conclusion, ablation of the AV junction shows a higher acute success rate compared with modulation of the AV node conduction in patients with drug refractory AF. Depending on the acute success, both approaches therefore were similarly effective in achieving long-term ventricular rate control and symptom score improvement.

Survival of DDD pacing mode after atrioventricular junction ablation and pacing for refractory atrial fibrillation

BACKGROUND

Patients with recurrent forms of atrial fibrillation may receive dual-chamber pacemakers after atrioventricular junction ablation for refractory symptoms. These patients are at risk for chronic atrial fibrillation, which would negate the benefits of dual-chamber pacing. The purpose of this study was to examine the survival of dual-chamber pacing modes in patients undergoing ablate and pace therapy.

METHODS AND RESULTS

One hundred fifty-six patients underwent ablate and pace therapy for medically refractory chronic (70 patients) or recurrent (86 patients) atrial fibrillation. Seventy-eight percent of patients had structural heart disease. The mean age was 66 +/- 11 years, with an average ejection fraction of 48% +/- 18%. The choice of pacing mode and programming were at the discretion of the investigators. At implantation, 91 patients (58%) were programmed to VVI mode, 47 (30%) were programmed to DDD mode, and 18 (12%) were programmed to DDI mode. After 1 year of follow-up, 10 DDD patients were reprogrammed to VVI mode (7 patients) or DDI mode (3 patients), most frequently for chronic atrial fibrillation (7 patients). Two patients with DDI mode were reprogrammed to VVI and DDD modes (1 patient each). Survival of the DDD mode was 76% at 1 year by Kaplan-Meier analysis. Reprogramming from DDD mode was not associated with patient age, left ventricular ejection fraction, discontinuation of antiarrhythmic drugs, or the duration of atrial fibrillation symptoms before ablation.

CONCLUSIONS

Seventy-six percent of patients with recurrent atrial fibrillation who are initially programmed to DDD mode remain in DDD mode 1 year after ablation and pacing therapy. The modest rate of progression to chronic atrial fibrillation supports the use of dual-chamber pacing in this setting.

Atrioventricular nodal ablation and pacemaker implantation in patients with atrial fibrillation

In drug-resistant, poorly tolerated atrial fibrillation, atrioventricular (AV) junction catheter ablation can be proposed as the last-resort option. Technically, the procedure is easy to perform and relatively safe. Interruption of the AV conduction implies the insertion of a permanent pacemaker. In patients with chronic atrial fibrillation, a VVIR pacemaker is inserted. For those having severely symptomatic episodes of paroxysmal atrial fibrillation, DDDR mode-switching devices are more appropriate. Results are remarkable. The treatment is highly effective in controlling symptoms and improving general well-being. Exercise capacity is also increased. Left ventricular ejection fraction may increase after ablation, an effect that is mainly apparent in patients with markedly depressed myocardial function. Consumption of healthcare resources has been shown to decrease significantly in the aftermath of AV junction ablation. However, sudden-death risk has been invoked as a limiting factor for the procedure. This may be due to AV-block-related ventricular tachyarrhythmias, occurring early after ablation, whereas the reasons for late sudden deaths are somewhat more obscure. It is unclear whether such events are procedure-related or rather secondary to the underlying heart disease. Thus, AV junction ablation for refractory atrial fibrillation remains the only nonpharmacologic, alternative therapy that is performed on a routine basis. Failure of newer therapeutic approaches should further reinforce the clinical impact of this procedure in the future.

Taking advantage of sophisticated pacemaker diagnostics

The ever-increasing complexity of pacing systems, combined with functions that vary from one manufacturer to another, can pose challenges during analysis of device function. Standard pacemaker diagnostics are measured data, electrogram telemetry, maker annotations and event counters, albeit with their current limitations. New diagnostic features discussed include time-based diagnostics, histograms of sensed amplitudes, pacing thresholds, or impedance trending. Mode-switching algorithms, combined with diagnostic features, facilitate the use of dual-chamber devices in patients with paroxysmal atrial tachyarrhythmias. The introduction of electrogram storage into pacemakers further improves diagnostic capabilities and allows a permanent validation and optimization of diagnostic and therapeutic algorithms. External diagnostic devices, which provide Holter recordings with continuous marker annotations and patient-triggered diagnostics, are additional features that will become increasingly important.

Frequency and long term follow up of valvar insufficiency caused by retrograde aortic radiofrequency catheter ablation procedures

OBJECTIVE

To assess the frequency of valvar complications caused by left sided radiofrequency catheter ablation using the retrograde aortic technique.

METHODS

179 patients (118 male) with a mean (SD) age of 43 (17) years underwent 216 procedures at one centre. The target of the ablation was an accessory atrioventricular pathway in 144 patients, the atrioventricular junction in 29 patients, and a ventricular tachycardia in six patients. In 25 patients structural heart disease was identified before the procedure (ischaemic heart disease 10, cardiomyopathy nine, valvar three, other three). Echo/Doppler examinations were performed the day before the procedure and within 24 hours postablation; the investigations were all reviewed by the same investigator. Patients with identified valvar injury caused by the procedure were followed for 42 (7) months.

RESULTS

Valvar injury caused by the ablation procedure was identified in four young (age 30 (8) years), otherwise healthy patients with left lateral atrioventricular accessory pathways. Mild mitral insufficiency with a central regurgitation jet was detected in two patients and remained unchanged at follow up. Mild aortic insufficiency was detected in another two patients. In one of these the regurgitation jet was central and remained unchanged at follow up. In one patient the regurgitation jet was located between the non-coronary and left cusps in relation to a loosely attached structure. Both the structure and the valvar regurgitation disappeared during follow up. No clinical complications occurred in any of the patients during follow up.

CONCLUSION

In this study, the frequency of valvar complications after left sided radiofrequency catheter ablation using the retrograde aortic technique was 1.9%.

Heterogeneous changes in electrophysiologic properties in the paroxysmal and chronically fibrillating human atrium

INTRODUCTION

The regional changes in atrial electrophysiologic properties related to atrial fibrillation (AF) in patients with paroxysmal AF (PAF) and chronic AF (CAF) remain unclear. The purpose of this study was to investigate the regional changes in atrial electrophysiology in patients with AF.

METHODS AND RESULTS

We evaluated the atrial electrophysiology at different sites (high right atrium, low right atrium [LRA], and distal coronary sinus [DCS]) in 11 patients with CAF, 8 patients with PAF, and 10 controls. Patients with CAF had significantly prolonged interatrial conduction and corrected sinus node recovery time, and shortened atrial effective refractory period (ERP) with loss of rate-related adaptation in the DCS, but had paradoxic prolongation of atrial ERP in the LRA, as compared with patients with PAF and the controls. As a result, the spatial distribution of atrial ERP that was observed in the controls and in patients with PAF was reversed in patients with CAF, without an increase in the dispersion of atrial refractoriness. Patients with PAF showed intermediate changes in atrial conduction times and atrial refractoriness as compared with patients with CAF and controls.

CONCLUSION

There was a regional heterogeneity on the changes of atrial electrophysiology in different parts of the atrium, and the "normal" spatial distribution of atrial refractoriness was reversed in patients with CAF. The electrophysiologic changes observed in patients with PAF appear to behave as if in transition from the control state to CAF, suggesting progressive changes in atrial electrophysiologic properties.

Determinants of development of permanent atrial fibrillation and its treatment

We evaluated the rate of progression of permanent atrial fibrillation (AF) and identified clinical factors that predict this event in 63 consecutive patients who had undergone AV junctional ablation and DDDR pacemaker implantation for drug-refractory paroxysmal atrial fibrillation/ flutter. Immediately after ablation, anti-arrhythmic drugs were discontinued in all cases. Permanent AF was considered to have developed if AF was present on two consecutive 6-monthly examinations with no interim documented sinus rhythm. During a mean follow-up of 23 +/- 16 months, 22 (35%) of the 63 patients developed permanent AF. The actuarial estimate of progression of permanent AF was 22%, 40% and 56%, respectively, 1, 2 and 3 years after ablation. Age and underlying heart disease were independent predictors of progression of permanent AF. Only one (6%) of 16 patients with idiopathic AF had permanent AF (low risk group). Among the 47 patients with structural heart disease, permanent AF developed in 18 (62%) of the 29 who were aged >75 years or had >12 arrhythmic episodes per year and a symptom duration >4 years (high risk group), but only in three (17%) of the remaining 18 patients who did not (intermediate risk group). In conclusion, during a 3-year follow-up period, about half of the patients with a history of drug-refractory paroxysmal AF did not develop permanent AF after AV junctional ablation and dual-chamber pacemaker implantation, even in the absence of anti-arrhythmic drug therapy. Moreover, subgroups of patients whose risk of permanent AF progression differed were identified on the basis of simple baseline clinical variables. The results of this study form the necessary background for the correct management of patients after AV junction ablation and for the planning of future trials in this field.

Chronic atrial fibrillation in patients with paroxysmal atrial fibrillation, atrioventricular node ablation and pacemakers: determinants and treatment

AIMS

This study examined the factors associated with the development of chronic (or permanent) atrial fibrillation (AF) in patients who had undergone atrioventricular (AV) node ablation with permanent pacing because of paroxysmal AF.

METHODS

A retrospective review of case notes of all 65 consecutive patients identified as having had paroxysmal atrial arrhythmias, AV node ablation and permanent pacemaker implantation was performed. Atrial rhythm was established from all pacing records and from the surface ECG. Treatment with anti-arrhythmic drugs and with warfarin was recorded. A multivariate analysis was undertaken, using atrial rhythm on final ECG and chronic AF as outcome measures.

RESULTS

During a mean follow-up of 30 months, 42% of patients with paroxysmal AF had developed chronic AF. Multivariate analysis showed that increasing age, history of electrical cardioversion and VVI pacing all contributed to the development of chronic AF. 25/62 patients were taking warfarin, and four had had strokes (2.5%/year).

CONCLUSION

The majority of patients with paroxysmal atrial arrhythmias treated with AV node ablation and pacing develop chronic AF eventually. Stroke remains a risk, particularly in those who develop chronic AF.

The Atrial Pacing Peri-ablation for Paroxysmal Atrial Fibrillation (PA3) Study: rationale and study design

The Canadian Atrial Pacing Peri-Ablation for Paroxysmal Atrial Fibrillation Study tested the hypotheses that atrial pacing prevents paroxysmal atrial fibrillation (PAF) in patients without symptomatic bradycardia and that DDDR pacing is more likely to prevent PAF following total atrioventricular (AV) node ablation compared to VDD pacing. Patients with PAF who were refractory to or intolerant of antiarrhythmic drug therapy received a Medtronic Thera DR pacemaker 3 months prior to a planned total AV node ablation. Patients were randomized to atrial pacing or no pacing therapy. The time to first recurrence of sustained PAF was the primary study outcome event. Following AV node ablation, patients were randomized to the DDDR or VDD mode in a crossover study design. Patients were followed in each mode for 6 months. The time course of PAF recurrence was compared for each pacing mode.

Atrial fibrillation trials: will they teach us what we need to know?

Atrial fibrillation (AF) has captured the imagination of clinical investigators who have initiated trials to examine several aspects of this multifaceted arrhythmia. We will review the protocol designs of ongoing trials that are examining the relative value of rhythm versus rate control, new methods for pharmacologic restoration and maintenance of sinus rhythm (including prophylaxis after cardiac surgery), and nonpharmacologic interventions such as pacing and atrial defibrillation. We antic ipate that the results of these studies will have a major impact on the care of patients with AF in the new millennium.

Unexpected instant death following successful coronary artery bypass graft surgery (and other clinical settings): atrial fibrillation, quinidine, procainamide, et cetera, and instant death

Primum non nocere. Atrial fibrillation (AF) occurs commonly following coronary artery bypass graft surgery, although new onset atrial fibrillation in this setting is usually transient. When AF reverts or is converted to sinus rhythm it is unlikely to recur, whether or not the patient takes preventive medication. As no benefit (and sometimes increased risk) associated with reduced mortality or morbidity in this setting has been reported for antiarrhythmic agents, standard treatment should consist of observation or control of ventricular response with an appropriate agent until AF relapses to sinus rhythm. If an antiarrhythmic agent, especially a class I agent, is used because of persistent or recurrent AF in the early postoperative period, heart rhythm should be monitored as long as the class I agent is administered and treatment initiated if an undersirable rhythm develops. Atrial fibrillation in other clinical settings in patients with structural heart disease presents a more difficult management problem. Class I agents are reported to be associated with an increased risk of death, despite an efficacious effect of maintaining sinus rhythm. Amiodarone is reported to be well tolerated with respect to the cardiovascular system, but unacceptable noncardiac effects are reported. A safe amiodarone-like agent is greatly needed. Atrial fibrillation in patients with no structural heart disease is not discussed in this presentation.

[Pacemaker therapy in patients with atrial fibrillation]

Pacemaker therapy in patients with atrial fibrillation means the best current pacemaker therapy for patients with bradycardias with the aim to avoid the onset of atrial fibrillation and to establish DDD pacing despite of a history of atrial tachyarrhythmias. The newer application of pacing is the suppression of atrial arrhythmias in patients with medical refractory atrial tachyarrhythmias. Patients with slow ventricular rates and permanent atrial fibrillation should receive a VVI-pacemaker, if the bradycardias causes syncope, dizziness or a decrease of their exercise tolerance. In case of chronotropic incompetence the pacemaker should provide rate responsive pacing. Patients with sick sinus syndrome should receive an atrial (AAI) or dual-chamber (DDD) pacemaker, because patients with these in contrast to VVI-pacemakers develop less often atrial fibrillation and subsequent complications such as atrial thromboembolism. A dual-chamber or VDD-pacemaker--the latter connected to a VDD-single-lead--is indicated in patients with advanced AV-block. Atrial fibrillation occurs in 3 to 6% of the patients with no history of arrythmia and is, if pacemakers have no automatic mode switch, an often reason to program the devices to the VVI-pacing mode. Nowadays, most DDD(R)-pacemakers provide an automatic mode switch: During an atrial tachycardia the pacemaker switches to a VVI/VVIR mode and restores the initial DDD(R)-pacing mode with termination of the arrhythmia. In respect to the newer applications, one approach to prevent atrial tachyarrhythmias is permanent atrial pacing. As lower pacing rates of 80 to 90 ppm are usually needed and many patients hardly tolerate these pacing rates, new algorithms are under clinical investigation. Another approach is the simultaneous depolarization of the right and left atrium. Biatrial pacing is performed with one lead in the high right atrium and another lead in the coronary sinus. Another solution is bifocal atrial pacing with leads placed in the high right atrium and in the coronary sinus ostium. One effect of the new pacing techniques is to shorten interatrial conduction times. Therefore, biatrial pacing has become a therapy to prevent atrial arrhythmias deriving from delayed interatrial conduction times. As atrial reentry circuits seem to be important in atrial fibrillation, multisite atrial pacing is also performed in patients with medical refractory paroxysmal atrial fibrillation. Preliminary results suggest a more effective prevention of atrial fibrillation; nevertheless, these techniques should be still restricted to patients enrolled in clinical studies.

Progression of permanent atrial fibrillation after atrioventricular junction ablation and dual-chamber pacemaker implantation in patients with paroxysmal atrial tachyarrhythmias

Among 63 patients affected by symptomatic drug refractory paroxysmal atrial fibrillation who had undergone atrioventricular junction ablation and dual-chamber pacemaker implantation, the actuarial estimate of progression of permanent atrial fibrillation was 22%, 40%, and 56% respectively, 1, 2, and 3 years after ablation. A stratification of the risk of development of permanent atrial fibrillation was obtained on the basis of several clinical variables.