Comparison of atrial overdrive pacing with and without extrastimuli for termination of atrial flutter

Optimization of pacing algorithms to prevent and treat supraventricular tachyarrhythmias

Preventive atrial pacing and antitachycardia pacing have been proposed for the treatment of atrial fibrillation and associated arrhythmias in patients with indications for device implantation. Preventive algorithms provide overdrive atrial pacing, reduction of atrial premature beats, and prevent short-long atrial cycles with good patient tolerance. However, clinical trials testing preventive algorithms have shown contradictory results, possibly because of different trial designs, end points and patient populations. Factors probably responsible for neutral results include an already high atrial pacing percentage with the conventional DDDR mode, suboptimal atrial pacing site, and the deleterious effects of high percentages of right ventricular apical pacing. Atrial antitachycardia pacing therapies are effective in treating organized atrial tachyarrhythmias (that precede atrial fibrillation), mainly when delivered early after the onset particularly if the tachycardia is relatively slow. Antitachycardia pacing therapies might influence atrial fibrillation burden, but clinical studies have shown conflicting results about this issue. Consistent monitoring of atrial and ventricular rhythm including progression to persistent forms of atrial arrhythmias, variability of atrial arrhythmia recurrence patterns and onset mechanisms as well as antitachycardia pacing efficacy should be recorded in the stored device memory and used for optimal individual programming of these new functions.

Management of atrial tachyarrhythmias. Rhythm control using implantable devices

Presently, most devices with atrial diagnostic and therapeutic features are implanted in patients for electrical treatment of bradyarrhythmias and ventricular tachyarrhythmias. The painless electrical strategies for prevention and termination of ATa have not demonstrated significant clinical effectiveness in the general population with ATa. The effectiveness of ATP in reducing burden may be significantly higher in a subgroup of patients with a high incidence of stable ATa, but this needs to be evaluated prospectively. Smart sensing and detection schemes will also help provide accurate information and determine when ATa can be terminated with ATP. Although electrical defibrillation is effective, the discomfort associated with atrial shocks has limited the widespread use of this technology. Recent technological advances have increased the capabilities of implantable devices to store large amounts of diagnostic information. In the near future, implantable devices without transvenous leads may be implanted to monitor a variety of physiologic signals. This could help improve clinical outcomes and determine which therapies (pharmacologic, ablative, or electrical) would be most effective as well as monitor their safety and efficacy. Frequent monitoring from home and the availability of this data to the physician/nurse on the Internet can potentially improve the management of patients' ATa at a much lower cost.

Randomized comparison between Ramp and Burst+ atrial antitachycardia pacing therapies in patients suffering from sinus node disease and atrial fibrillation and implanted with a DDDRP device

AIMS

Atrial tachycardia and flutter frequently occur in association with atrial fibrillation and may be treated by overdrive pacing in patients who receive pacemakers with antitachycardia pacing (ATP) capabilities. The PITAGORA trial was a multi-centre, randomized, cross-over study aimed at comparing two different ATP modes for atrial tachyarrhythmia (AT) termination in patients suffering from sinus node disease (SND).

METHODS AND RESULTS

One hundred and seventy-six patients (72 M, age 71+/-9 years) received a Medtronic AT500 pacemaker. All patients were on class IC or III antiarrhythmic drugs. After a 5-month observation period, 170 patients were randomized to either Ramp or Burst+ ATP therapy; 4 months later they crossed over. One hundred and fifty-seven patients completed the 13 months of follow-up; 114 (72.6%) suffered 6088 AT episodes. In 75 patients, 1904 AT episodes were treated and 934 (49.1%) successfully terminated. The median value of individual patients' ATP efficacy was 60%. Burst+ terminated 387 out of 873 AT episodes (44%) in 58 patients. Ramp terminated 547 out of 1031 AT episodes (53%, P<0.001) in 56 patients. Ramp efficacy was significantly (P<0.01) and directly correlated with AT cycle length (ATCL), whereas Burst+ efficacy was not. Ramp showed higher (P<0.001) termination efficacy than Burst+ for ATCL >240 ms. Quality of life, as measured by the EuroQoL questionnaire, and number of symptoms significantly improved in the overall population. This improvement was significantly higher in patients with ATP efficacy >60%.

CONCLUSION

In patients suffering from SND and AT, Ramp therapy shows higher termination efficacy than Burst+ therapy in AT episodes with ATCL >240 ms. Further studies are required to show the impact of ATP on clinical outcomes.

Use of global atrial fibrillation organization to optimize the success of burst pace termination

OBJECTIVES

The purpose of this study was to determine if burst atrial pacing would have an effect on terminating atrial fibrillation.

BACKGROUND

We hypothesized that frequency domain analysis of a filtered wide bipolar atrial electrogram describes the global organization of atrial fibrillation (AF) and should vary over time. Timing burst pacing to periods of high organization of AF should promote regional atrial conduction block and terminate AF.

METHODS

Nine dogs were conditioned with rapid atrial pacing for 48 h. Electrogram recordings were made from a wide right atrium (RA) to left atrium (LA) bipole and digitally filtered. A fast-Fourier transform was performed every 0.5 s on a sliding 2-s window, and the organization index (OI) was calculated as a ratio of the area of the first four harmonic peaks to the total power of the spectrum. Organization indexes >0.5 indicated more organized AF activity. Right atrium and LA burst pacing (burst) (cycle length 50 ms, 9.9 ms, 9.9 mA, 1 to 4 s) was performed through decapolar catheters. Burst was either random or synchronized to OI >0.5.

RESULTS

Burst termination was attempted 1,814 times (889 OI sync, 925 random) and succeeded in seven of nine dogs. Burst had an overall success rate of 11.1% versus 6.3% for random (p < 0.0003). Biatrial pacing had the highest efficacy for terminating AF, with a success rate of 16.5% for OI sync versus 8.2% for random (p < 0.0001).

CONCLUSIONS

Timing the delivery of the burst pace when the OI is >0.5 increases the efficacy of burst pace termination of AF. Biatrial pacing is more effective than either RA or LA pacing alone.

Safety and efficacy of advanced atrial pacing therapies for atrial tachyarrhythmias in patients with a new implantable dual chamber cardioverter-defibrillator

OBJECTIVES

This study evaluated the safety and efficacy of atrial pacing therapies for the treatment and prevention of atrial tachycardia (AT) or atrial fibrillation (AF) in a new dual chamber implantable cardioverter defibrillator (ICD).

BACKGROUND

Patients with an ICD may also experience AT or AF that is amenable to pace termination.

METHODS

The efficacy of atrial antitachycardia pacing (ATP) therapies for atrial tachycardia or atrial fibrillation (AT/AF) was determined in 151 patients after implantation of a GEM III AT ICD (Medtronic Inc., Minneapolis, Minnesota). The percentage of episodes successfully terminated was adjusted for multiple episodes per patient.

RESULTS

A total of 717 of 728 (96%) episodes classified as AT or AF were judged to be appropriate detections. By device classification, atrial ATP terminated 187 of 383 (40% adjusted) episodes classified as AT compared with 65 of 240 episodes classified as AF (26% adjusted, p = 0.013). Atrial Ramp or Burst+ ATP terminated 184 of 378 episodes of AT (39% adjusted), whereas 50-Hz Burst pacing therapy terminated only 12 of 109 episodes of AT (12% adjusted) and 65 of 240 episodes of AF (26% adjusted). If efficacy was defined as termination of AT/AF within 20 s of delivery of the pacing therapy, ATP therapies terminated 139 of 383 (32% adjusted) episodes of AT compared with 34 of 240 episodes of AF (15% adjusted, p = 0.003). Efficacy was dependent on AT cycle length. Frequent transitions between AT and AF predicted inefficacy of atrial ATP (p < 0.001). Ventricular proarrhythmia secondary to atrial ATP was not observed.

CONCLUSIONS

Atrial ATP therapies terminate many episodes of AT without ventricular proarrhythmia. The addition of 50-Hz Burst pacing has minimal efficacy for AT/AF.

Suppression of atrial tachyarrhythmias by pacing

INTRODUCTION

Treatment of atrial tachyarrhythmias (ATs) remains difficult in many patients. Accordingly, new therapeutic approaches for AT suppression are evaluated. Atrial pacing may prevent ATs by modifying the electrophysiologic conditions required for sustained ATs.

METHODS AND RESULTS

New pacing algorithms for prevention of AT are aimed at permanent overdrive suppression of arrhythmic activity, reduction of dispersion of atrial refractoriness produced by short-long cycles, more aggressive overdrive pacing after spontaneous sinus conversion to prevent early reinitiation of ATs, and prevention of inadequate rate decay in patients with vagally induced ATs. AT prevention may be achieved by dedicated atrial pacing sites, e.g., pacing at the insertion of Bachmann's bundle or biatrial pacing, which compensates for interatrial conduction delay. Preexciting regions of critical conduction delay, pacing at the triangle of Koch or coronary sinus os, and dual-site right atrial pacing have shown antiarrhythmic effects. Atrial preventive pacing and pharmacologic treatment may work synergistically in the concept of hybrid therapy. To prevent atrial electrical remodeling, early termination of AT seems desirable. This may be achieved by implanted devices that automatically detect ATs and provide atrial antitachycardia pacing for organized ATs. Initial studies showed that regular AT can automatically be terminated in approximately 50% of treated episodes.

CONCLUSION

Pacing for prevention of AT and termination of organized AT episodes may become important steps within the concept of hybrid therapy of AT. However, their clinical efficacy and optimal patient selection remain to be evaluated in prospective, well-designed clinical trials.

Automatic atrial anti-tachy pacing for the termination of spontaneous atrial tachyarrhythmias: clinical experience with a novel dual-chamber pacemaker

Automatic atrial anti-tachy pacing (aATP) is a novel approach to treat paroxysmal/persistent atrial tachyarrhythmias in pacemaker patients. To evaluate the efficacy of aATP in terminating spontaneous atrial flutter/tachycardia episodes (AT), a dual-chamber stimulator with extensive diagnostic capabilities and programmable aATP therapies (AT500(TM), Medtronic Inc.) was implanted in 30 patients with conventional pacing indications. During a mean follow-up time of 5.5 (1-12) months, aATP was delivered for 10494 AT. According to automatic device analysis, 8289 AT were treated with success (success-rate 79.0%). On 468 AT stored with the corresponding atrial EGM, an additional manual analysis was performed. The success-rate based on automatic analysis of these AT episodes (73.1%) was comparable to that found for all treated AT (79.0%), but manual EGM analysis revealed that only 209 of the 468 treated AT episodes (44.7%) were actually terminated by aATP. The aATP success-rate in the slower (cycle length 360-270 ms) AT detection zone was significantly higher (73.8%, 62/84 eps) than in the overlapping, faster (cycle length 270-220 ms) AT zone (38.3%, 147/384 eps, P<0.01).

CONCLUSIONS

According to manual analysis, 1. aATP was safe and had a success-rate of 44.7%, 2. aATP success-rate was higher for AT in the slower than in the faster detection zone and 3. automatic analysis overestimated the efficacy of aATP.

Efficacy of pacing therapies for treating atrial tachyarrhythmias in patients with ventricular arrhythmias receiving a dual-chamber implantable cardioverter defibrillator

BACKGROUND

Although overdrive pacing for treating atrial flutter is well established, the efficacy of device-based atrial pacing for treating spontaneous atrial tachyarrhythmias in patients with implantable cardioverter defibrillators (ICD) is unknown. This study evaluated the efficacy of novel pacing therapies for treating atrial tachyarrhythmias in patients receiving a dual-chamber ICD to treat ventricular tachyarrhythmias.

METHODS AND RESULTS

A Jewel AF ICD was implanted in 537 patients with ventricular arrhythmia who were followed for 11.4+/-8.2 months (74% had a documented history of atrial tachyarrhythmias). The device discriminated atrial tachycardia (AT) from atrial fibrillation (AF) on the basis of cycle length and regularity, and it used 3 different methods of overdrive atrial pacing (Ramp, Burst+, and 50-Hz burst) to treat AT episodes and one method (50-Hz burst) to treat AF episodes. Pacing successfully terminated 59% of 1500 spontaneous AT episodes in 127 patients and 30% of 880 AF episodes in 101 patients (P<0.001). With AT and AF episodes combined, pacing efficacy was 48%. Pacing efficacy was significantly reduced at AT cycle lengths </=220 ms and AF cycle lengths </=160 ms (P<0.01) The median time from pacing to AT/AF termination was 1.1 minute for the pacing successes and 96 minutes for the failures (P<0.001).

CONCLUSIONS

Atrial pacing terminated 48% of AT/AF episodes in patients with a history of ventricular arrhythmias. Pacing efficacy was greater for device-classified AT than AF. Pacing efficacy was significantly influenced by tachycardia cycle length. Successful pacing significantly reduces the time required for AT/AF termination.

Detection of atrial arrhythmia for cardiac rhythm management by implantable devices

Implantable atrial defibrillators (IAD) should provide pacing therapy whenever appropriate (ie, typical atrial flutter) to minimize shock-related patient discomfort. Additionally, IADs should provide diagnostics regarding atrial arrhythmia type and frequency of occurrence to enable improved physician management of atrial arrhythmia. To achieve this, IADs should accurately classify atrial arrhythmia such as atrial fibrillation (AF) and atrial flutter (AFL) This article evaluates the performance of an algorithm, atrial rhythm classification (ARC), designed to classify AF and AFL. The ARC algorithm uses maximum rate, standard deviation, and range of the 12 most recent atrial cycle lengths to plot a point in a three-dimensional space. A decision boundary divides the space into 2 regions--faster/unstable atrial cycle lengths (AF) or slower/stable cycle lengths (AFL). Classifications are made on a sliding window of 12 consecutive cycles until the end of the episode is reached. In this way, continuous episode feedback is provided that can be used to help guide device therapy, measure arrhythmia type and frequency of occurrence. Bipolar (1-cm) electrogram episodes of AF (n = 16) and AFL (n = 7) were acquired from 20 patients and retrospectively analyzed using the ARC algorithm. The sensitivity and specificity in this study was 0.993 and 0.982, respectively. The ARC algorithm would have appropriately guided atrial therapy and minimized discomfort associated with defibrillation shocks in this small patient data set warranting further studies. The ARC algorithm may also be beneficial as a diagnostic tool to assist physician management of atrial arrhythmia.

How smart should pacemakers Be?

The concept of the "smart" pacemaker has been continuously changing during 40 years of progress in technology. When we talk today about smart pacemakers, it means optimal treatment, diagnosis, and follow-up for patients fitting the current indications for pacemakers. So what is smart today becomes accepted as "state of the art" tomorrow. Originally, implantable pacemakers were developed to save lives from prolonged episodes of bradycardia and/or complete heart block. Now, in addition, they improve quality of life via numerous different functions acting under specific conditions, thanks to the introduction of microprocessors. The devices have become smaller, with the miniaturization of the electrical components, without compromising longevity. Nevertheless, there are still some unmatched objectives for these devices, for example, the optimization of cardiac output and the management of atrial arrhythmias in dual-chamber devices. Furthermore, indications continue to evolve, which in turn require new, additional functions. These functions are often very complex, necessitating computerized programming to simplify application. In addition, the follow-up of these devices is time-consuming, as appropriate system performance has to be regularly monitored. A great many of these functions could be automatically performed and documented, thus enabling physicians and paramedical staff to avoid losing time with routine control procedures. In addition, modern pacemakers offer extensive diagnostic functions to help diagnose patient symptoms and pacemaker system problems. Different types of data are available, and their presentation differs from one company to the other. This huge amount of data can only be managed with automatic diagnostic functions. Thus, the smart pacemaker of the near future should offer high flexibility to permit easy programming of available therapies and follow-up, and extensive, easily comprehensible diagnostic functions.

Overdrive atrial pacing for conversion of atrial flutter: comparison of postoperative with nonpostoperative patients

BACKGROUND

Previous studies have reported varying success rates in overdrive pace termination of atrial flutter. We hypothesized that these discrepancies might be caused by differences in study populations. Accordingly, we prospectively compared the success rate of pacing in patients with atrial flutter that occurred after heart surgery with that of patients with atrial flutter from other causes.

METHODS AND RESULTS

The study population consisted of 65 consecutive patients referred for pace termination of typical (type I) atrial flutter. Pacing was performed in 30-second bursts, starting at the flutter cycle length, and repeated in 5-ms decrements until normal sinus rhythm or atrial fibrillation occurred. Normal sinus rhythm was restored in 38 (65%) patients. Of 20 patients whose flutter was precipitated by heart surgery, 19 (95%) were successfully pace terminated. In contrast, pace termination was successful in only 47% of the remainder of the population (P <.001). No other clinical parameters were predictive of outcome.

CONCLUSIONS

We conclude that overdrive pacing is an effective means of terminating atrial flutter that has occurred after heart surgery. Alternative methods should be considered as the initial therapeutic approach in patients with atrial flutter from other causes.

Intracardiac overdrive pacing as a treatment of atrial flutter in a horse

A five-year-old warmblood mare with atrial fibrillation was treated with quinidine sulphate. The atrial rhythm changed to atrial flutter and, because there were toxic effects, the treatment was discontinued. Seven months after the occurrence of the atrial flutter, treatment with a rapid atrial pacing technique restored a normal sinus rhythm. One year after the pacing therapy the horse was still in sinus rhythm and had been brought back into training.

Pharmacologic therapy of atrial flutter

Atrial flutter is a relatively rare but nonetheless important arrhythmia. Its mechanism and anatomy have been defined as right atrial macroreentry. It responds to treatment with a variety of antiarrhythmic agents but, in general, drug efficacy for acute termination is low. The addition of pacing to drug therapy markedly improves the success rate for restoration of sinus rhythm. Useful antiarrhythmic agents include amiodarone, sotalol, disopyramide, flecainide, and propafenone, but definitive efficacy studies have not been performed. The risk of provoking 1:1 AV conduction and a marked increase in ventricular response rate is always present. AV nodal blocking drugs (digoxin and verapamil) probably offer protection from this unwanted effect, but the prevalence of 1:1 conduction and the efficacy of AV nodal blockade remain to be established. When drug management fails, there is a place for radiofrequency ablation. Little is known about the thromboembolic risk of atrial flutter. As a consequence, the role of prophylactic anticoagulation is uncertain. Current interest in atrial flutter will ensure that these and other clinical questions are answered in the near future.

Comparative efficacy of intravenous ibutilide versus procainamide for enhancing termination of atrial flutter by atrial overdrive pacing

This study compares the influence of intravenous ibutilide, a class III antiarrhythmic agent, with procainamide, a class IA antiarrhythmic agent, and with placebo on its ability to terminate atrial flutter using rapid atrial pacing. Fifty-nine episodes of atrial flutter in 54 patients who failed to terminate with an intravenous infusion of ibutilide, procainamide, or placebo alone underwent attempts at pacing termination using a standard protocol of burst atrial overdrive pacing. Atrial flutter cycle length and atrial monophasic action potential duration recorded from the right atrium during atrial flutter were measured at baseline and following infusion of ibutilide, procainamide, or placebo. Both ibutilide and procainamide significantly enhanced (p <0.001) pacing-induced termination of atrial flutter compared with placebo. Pacing converted 2 of 11 patients (18%) who received placebo, 13 of 15 patients (87%) who received ibutilide, and 29 of 33 patients (88%) who received procainamide to sinus rhythm. Ibutilide and procainamide compared with placebo markedly reduced (p <0.001) the incidence of pacing-induced atrial fibrillation. The atrial flutter cycle length was prolonged significantly less (p <0.001), and the atrial monophasic action potential duration was increased significantly more (p <0.001) by ibutilide than by procainamide. Although the electrophysiologic changes induced by these antiarrhythmic agents contributed to facilitating pacing-induced termination, neither tachycardia cycle length nor action potential duration were useful predictors of the ability of pacing to terminate atrial flutter. In conclusion, despite differing electrophysiologic effects, the use of intravenous ibutilide or procainamide enhances the termination of atrial flutter by atrial overdrive pacing.

Overdrive pacing for atrial flutter

To determine the incidence and predictors of conversion to normal sinus rhythm, a total of 124 procedures using a standard pacing protocol were performed in 101 consecutive inpatients referred for pace termination of atrial flutter. Normal sinus rhythm was achieved in 75 pace termination procedures (60%), including 10 in which atrial fibrillation occurred initially and later converted spontaneously. Sustained atrial fibrillation was provoked in 39 procedures, and atrial flutter persisted in 10. Clinical and laboratory parameters, including use of antiarrhythmic drugs, were not helpful in predicting the outcome of pacing. Of 17 patients undergoing repeat pacing for recurrent flutter, concordant results were obtained in only 4. It is concluded that: (1) overdrive pacing is only a moderately effective means of restoring sinus rhythm in patients with atrial flutter, although some change in rhythm occurs in the vast majority; (2) pacing-induced atrial fibrillation may be unstable and spontaneously converts to sinus rhythm in > 20% of cases; (3) there are no clinically useful predictors of success; (4) antiarrhythmic drugs do not facilitate pacing-induced conversion to sinus rhythm; and (5) failure to convert to sinus rhythm with 1 episode of flutter does not preclude success on subsequent occasions.