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

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

AIM

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

METHODS

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

STRUCTURE

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

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

AIM

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

METHODS

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

STRUCTURE

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

The physics of heart rhythm disorders

The global burden caused by cardiovascular disease is substantial, with heart disease representing the most common cause of death around the world. There remains a need to develop better mechanistic models of cardiac function in order to combat this health concern. Heart rhythm disorders, or arrhythmias, are one particular type of disease which has been amenable to quantitative investigation. Here we review the application of quantitative methodologies to explore dynamical questions pertaining to arrhythmias. We begin by describing single-cell models of cardiac myocytes, from which two and three dimensional models can be constructed. Special focus is placed on results relating to pattern formation across these spatially-distributed systems, especially the formation of spiral waves of activation. Next, we discuss mechanisms which can lead to the initiation of arrhythmias, focusing on the dynamical state of spatially discordant alternans, and outline proposed mechanisms perpetuating arrhythmias such as fibrillation. We then review experimental and clinical results related to the spatio-temporal mapping of heart rhythm disorders. Finally, we describe treatment options for heart rhythm disorders and demonstrate how statistical physics tools can provide insights into the dynamics of heart rhythm disorders.

EHRA White Paper: knowledge gaps in arrhythmia management—status 2019

Clinicians accept that there are many unknowns when we make diagnostic and therapeutic decisions. Acceptance of uncertainty is essential for the pursuit of the profession: bedside decisions must often be made on the basis of incomplete evidence. Over the years, physicians sometimes even do not realize anymore which the fundamental gaps in our knowledge are. As clinical scientists, however, we have to halt and consider what we do not know yet, and how we can move forward addressing those unknowns. The European Heart Rhythm Association (EHRA) believes that scanning the field of arrhythmia / cardiac electrophysiology to identify knowledge gaps which are not yet the subject of organized research, should be undertaken on a regular basis. Such a review (White Paper) should concentrate on research which is feasible, realistic, and clinically relevant, and should not deal with futuristic aspirations. It fits with the EHRA mission that these White Papers should be shared on a global basis in order to foster collaborative and needed research which will ultimately lead to better care for our patients. The present EHRA White Paper summarizes knowledge gaps in the management of atrial fibrillation, ventricular tachycardia/sudden death and heart failure.

Is An Atrial Defibrillator Still An Option In Treating Patients With Atrial Fibrillation?

Atrial fibrillation (AF) is a common disorder associated with significant morbidities and presents several challenges for the control of symptoms and prevention of long-term implications. Atrial defibrillators (ADs), used for rhythm control in patients with symptoms refractory to medical therapy, can detect recurrences of the arrhythmia, allow prompt patient-directed treatment, and have the potential to reduce hospitalizations and improve quality of life. The efficacy of this form of therapy is highest in patients with paroxysmal AF, and with the use of a coronary sinus shocking lead. While R-wave synchronized shocks are a prerequisite for a safe use, the procedure is well tolerated and usually not associated with long-term psychological side effects. Limitations of ADs include acute and chronic complications related to cardiac rhythm device implantation, the requirement in some cases for more than one shock to terminate AF, the discomfort from shocks, as well as the need for sedation to alleviate pain from the shocks. With the ever-expanding role of catheter-based therapies for AF, it seems that the role of ADs in this regard is rather limited.

Atrial burst pacing with biphasic and monophasic waveforms for atrial fibrillation

BACKGROUND

Biphasic pacing is a novel mode of pacing that was suggested to increase cardiac conduction velocity as compared with cathodal monophasic pacing. We aimed to evaluate the safety and efficacy of rapid atrial pacing to convert atrial fibrillation (AF) to normal sinus rhythm.

METHODS

Multiple biphasic (anodal/cathodal), reverse biphasic (cathodal/anodal), and monophasic (cathodal) atrial pacing therapies were performed among 12 patients undergoing left atrial catheter ablation for AF. The efficacy end point was successful conversion of AF to sinus rhythm, and safety end point no induction of ventricular arrhythmias. Patients were paced at three cycle lengths (100, 200, and 333 msec) for 60 seconds at three locations (right and left atrial appendages and coronary sinus).

RESULTS

Among the 66 biphasic (anodal/cathodal) pacing procedures one procedure in a patient with chronic AF, which involved pacing at the left atrial appendage with a cycle length of 200 msec, led to conversion of AF to sinus rhythm. None of the 66 monophasic pacing procedures or the 66 reverse biphasic (cathodal/anodal) pacing procedures was associated with AF termination. None of the biphasic pacing procedures was associated with induction of ventricular arrhythmias.

CONCLUSIONS

Rapid atrial pacing using a variety of waveforms at the cycle length and output used in the current study was found to be safe. There was a single success in converting a chronic AF to sinus rhythm.

Morphological analysis of sinus and retrograde atrial waves detected through a permanent pacemaker atrial lead

AIMS

The main objective of this study was to characterize morphological differences between sinus and retrograde atrial waves.

METHODS

We collected intracardiac atrial signals through a DDDR pacemaker to characterize their morphologies and discriminate retrograde from sinus atrial waves off-line. Intracardiac unipolar and bipolar signals were collected at an 800-Hz sampling rate through a 0.4-Hz high-pass filter. Sinus and retrograde atrial waves during ventricular pacing were recorded in the supine and upright positions.

RESULTS

Eleven different form parameters (FPs) were applied to describe atrial wave morphology. Data from 14 patients were collected and analyzed. Atrial signals differed markedly between the two body postures. However, it was possible to discriminate retrograde from sinus atrial waves on the basis of at least one FP in 12 of 14 (86%) patients when unipolar and bipolar atrial signals recorded in both body postures were analyzed separately. When body postures were pooled together to mimic natural conditions, discrimination was successful in nine of 14 patients with either configuration of the atrial signal.

CONCLUSIONS

The results indicate that retrograde atrial waves can be discriminated from sinus waves by using high sampling rate, digital signal processing, and specific FPs incorporated in these pacemakers.

Termination of atrial fibrillation using pulsed low-energy far-field stimulation

BACKGROUND

Electrically based therapies for terminating atrial fibrillation (AF) currently fall into 2 categories: antitachycardia pacing and cardioversion. Antitachycardia pacing uses low-intensity pacing stimuli delivered via a single electrode and is effective for terminating slower tachycardias but is less effective for treating AF. In contrast, cardioversion uses a single high-voltage shock to terminate AF reliably, but the voltages required produce undesirable side effects, including tissue damage and pain. We propose a new method to terminate AF called far-field antifibrillation pacing, which delivers a short train of low-intensity electric pulses at the frequency of antitachycardia pacing but from field electrodes. Prior theoretical work has suggested that this approach can create a large number of activation sites ("virtual" electrodes) that emit propagating waves within the tissue without implanting physical electrodes and thereby may be more effective than point-source stimulation.

METHODS AND RESULTS

Using optical mapping in isolated perfused canine atrial preparations, we show that a series of pulses at low field strength (0.9 to 1.4 V/cm) is sufficient to entrain and subsequently extinguish AF with a success rate of 93% (69 of 74 trials in 8 preparations). We further demonstrate that the mechanism behind far-field antifibrillation pacing success is the generation of wave emission sites within the tissue by the applied electric field, which entrains the tissue as the field is pulsed.

CONCLUSIONS

AF in our model can be terminated by far-field antifibrillation pacing with only 13% of the energy required for cardioversion. Further studies are needed to determine whether this marked reduction in energy can increase the effectiveness and safety of terminating atrial tachyarrhythmias clinically.

[Sandwiched between the single- and triple-chamber ICD: do we still need the dual-chamber ICD?]

Since it has been shown that adverse events are more frequent with dual-compared to single-chamber ICDs in patients with heart failure, and since the importance of prevention of unnecessary right ventricular pacing and the success of biventricular pacing have been demonstrated in numerous studies, the need for dual-chamber ICD systems has to be reassessed. The development of these systems was accompanied by expectations of improved hemodynamics in patients with bradycardia, a reduced incidence of atrial fibrillation, inappropriate therapies, and bradycardia-associated ventricular tachyarrhythmias. Single-chamber ICDs should be used restrictively and with great caution in patients with (sinus-) bradycardia and heart failure, since a relevant proportion of these patients is at risk of hemodynamic deterioration. Even if the proportion of patients with proven pacemaker syndrome is so small that it does not reach the level of statistical significance in large studies, a small percentage of patients with hemodynamic deterioration due to VVI pacing is still clinically (and economically) intolerable. Since the development of bradycardia or symptomatic chronotropic incompetence (e.g., due to amiodarone) is difficult to predict, it seems reasonable to use the indication for dualchamber systems liberally. However, the systematic prevention of unnecessary right ventricular pacing is crucial if dual-chamber ICDs are used. If advanced tachycardia discrimination algorithms and careful, individual programming are used, dual-chamber ICDs are superior in the prevention of inappropriate therapies. Additionally, dualchannel electrograms allow a more reliable interpretation of stored tachycardia episodes. In summary, dual-chamber systems represent a valuable improvement of ICD therapy but require thorough programming to convey their advantage.

How, why, and when may atrial defibrillation find a specific role in implantable devices? A clinical viewpoint

This viewpoint article discusses the potential for incorporation of atrial defibrillation capabilities in modern multi-chamber devices. In the late 1990s, the possibility of using shock-only therapy to treat selected patients with recurrent atrial fibrillation (AF) was explored in the context of the stand-alone atrial defibrillator. The failure of this strategy can be attributed to the technical limitations of the stand-alone device, low tolerance of atrial shocks, difficulties in patient selection, a lack of predictive knowledge about the evolution of AF, and, last but not least, commercial considerations. An open question is how atrial defibrillation capability may now assume a specific new role in devices implanted for sudden death prevention or cardiac resynchronization. For patients who already have indications for implantable devices, device-based atrial defibrillation appears attractive as a "backup" option for managing AF when preventive pharmacological/electrical measures fail. This and several other personalized hybrid therapeutic approaches await exploration, though assessment of their efficacy is methodologically challenging. Achievement of acceptance by patients is an essential premise for any updated atrial defibrillation strategy. Strategies that are being investigated to improve patient tolerance include waveform shaping, pharmacologic modulation of pain, and patient-activated defibrillation (patients might also perceive the problem of discomfort somewhat differently in the context of a backup therapy). The economic impact of implementing atrial defibrillation features in available devices is progressively decreasing, and financial feasibility need not be a major issue. Future studies should examine clinically relevant outcomes and not be limited (as occurred with stand-alone defibrillators) to technical or other soft endpoints.

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.

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.

Role of High Frequency Atrial Pacing for the Termination of Acute Atrial Fibrillation and Atypical Atrial Flutter

BACKGROUND

The aim of this study was to assess the efficacy of high-frequency (HF) pacing from the right atrial appendage (RAA) or coronary sinus ostium (CS-Os) for the termination of acute atrial fibrillation (AF) and atypical atrial flutter (AAFL) during an electrophysiological (EP) study.

METHODS

128 episodes of acute fast atrial arrhythmias (FAAs; 93 AF and 35 AAFL) were analyzed in 110 patients. Patients were initially observed for 60s leading to spontaneous termination of 28 FAAs. The remaining 100 FAAs (70 AF) episodes were randomized to the following strategies: (A) pacing at RAA using up to 10 consecutive 20-Hz trains followed by the same stimulation protocol at CS-Os if RAA pacing failed, (B) pacing at CS-Os using the same stimulation protocol followed by HF pacing at RAA, or (C) observation up to 6 minutes ("no pacing").

RESULTS

The 20-Hz pacing at both RAA and CS-Os was associated with higher conversion of AAFL, as compared to strategy C (60% and 77% vs 11%; P < 0.05). Only HF pacing at CS-Os was superior to observation strategy for the conversion of AF (21% vs 4%; P < 0.05).

CONCLUSIONS

The 20-Hz pacing protocol is superior to observation strategy for interruption of either acute AF or acute AAFL episodes; however, its efficacy is higher in AAFLs. These results can be helpful for the termination of acute atrial tachyarrhythmias during EPstudy and should be further evaluated in patients with implantable devices capable of antitachycardia pacing.

Physiologic Pacing for Atrial Fibrillation Prevention in Sinus Node Disease: Long-Term Results

BACKGROUND

Physiologic pacing has been demonstrated to be effective in preventing atrial fibrillation recurrences in patients with sinus bradycardia. Aim of the study was to evaluate long-term incidence of atrial fibrillation in a large population of patients affected by sinus node disease receiving physiologic pacing. Furthermore, predictors of arrhythmia recurrence and effect of pacing mode were investigated.

POPULATION

Four hundred twenty-five patients (220 Male, 77 +/- 9 years) were retrospectively analyzed: implanted system was AAI in 20.5% and DDD in 79.5%. Thirty-four percent had atrial fibrillation before implant.

RESULTS

Follow-up lasted on average 51 +/- 36 months (median 42, range 1 month-18 years). Sixty-six percent were on antiarrhythmic drug therapy. After 5 years, 89% survived, 74.5% had at least one episode of atrial fibrillation, 39.9% were submitted to electrical cardioversion, 67.2% were hospitalized because of cardiac causes, 33.3% developed permanent atrial fibrillation. Primary conduction system disease and valvular heart disease were independent predictors for atrial fibrillation recurrence. Preimplant atrial fibrillation predicted arrhythmia recurrence during the follow-up, but it did not predict development of permanent atrial fibrillation. AAI pacing, when compared with DDD, was associated to a lower rate of atrial fibrillation recurrences (AAI 28.7%, DDD 53.3%, P < 0.001).

CONCLUSION

In spite of expected benefits of physiologic pacing, the development of atrial fibrillation and permanent atrial fibrillation were quite common. The additional benefits of multifunction pacemakers designed to prevent and treat atrial fibrillation should be evaluated in controlled studies.

Transthoracic Tissue Doppler Imaging of the Atria: A Novel Method to Determine the Atrial Fibrillation Cycle Length

BACKGROUND

The atrial fibrillation cycle length (AFCL) is a critical parameter for the perpetuation and termination of AF. In the present study, we evaluated a new method to measure the AFCL based on transthoracic tissue Doppler imaging (TDI) of the right atrium (RA) and left atrium (LA).

METHODS

Twenty patients with AF (6 acute AF, 14 persistent or permanent AF) were studied. A quadripolar catheter was positioned at RA or LA to measure AFCL (AFCL(EGM), gold standard). Transthoracic echocardiography (apical 4-chamber view) was used to perform pulsed wave TDI at the free wall of RA or LA. AFCL(TDI) was defined as the time interval between two consecutive positive to negative crossings of the baseline of the atrial time velocity curves. AFCL(EGM) and AFCL(TDI) were measured at baseline and during a 10-minute infusion of flecainide (1.5 mg/kg).

RESULTS

Measurement of AFCL(TDI) was feasible in all but one patient. At baseline, AFCL(EGM) was 170 +/- 22 ms, AFCL(TDI) 172 +/- 22 ms (difference 2 +/- 5 ms). AFCL(TDI) correlated significantly with AFCL(EGM) (R = 0.91, P < 0.0001). Bland-Altman analysis showed a bias of -2 ms with a 95% limit of agreement between -26 ms and +22 ms. During flecainide, the AFCL(TDI) method yielded an AFCL prolongation from 176 +/- 23 ms at baseline to 279 +/- 68 ms (P < 0.01) after 10 minutes of infusion (57 +/- 26%).

CONCLUSIONS

(1) Tissue Doppler imaging of the atria during transthoracic echocardiography can be used to reliably determine the AFCL during both acute and persistent or permanent AF. (2) Continuous measurement of AFCL with TDI can be used to monitor the effect of antiarrhythmic drugs on atrial rate during AF. (3) This novel method is attractive because of the ease of acquiring the data and its noninvasive character.

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.

Internal defibrillation: where we have been and where we should be going?

Internal cardioversion has been developed as an alternative technique for patients who are resistant to external DC cardioversion of atrial fibrillation (AF) and was found to be associated with higher success rates. It used initially high energies (200-300 J) delivered between an intracardiac catheter and a backplate. Subsequent studies have shown that it is possible to terminate with energies of 1 to 6 Joules, paroxysmal or induced AF in 90 percent of patients and persistent AF in 75 percent of patients, using biphasic shocks delivered between a right atrium-coronary sinus vectors. Consequently, internal atrial defibrillation can be performed under sedation only without the need for general anesthesia. Recently developed external defibrillators, capable of delivering biphasic shocks, have increased the success rates of external cardioversion and reduced the need for internal cardioversion. However, internal defibrillation is still useful in overweight or obese patients, in patients with chronic obstructive pulmonary disease or asthma who are more difficult to defibrillate, and in patients with implanted devices which may be injured by high energy shocks. Low energy internal defibrillation has also proven to be safe and this has prompted the development of implantable devices for terminating AF. The first device used was the Metrix system, a stand-alone atrial defibrillator (without ventricular defibrillation) which was found to be safe and effective in selected groups of patients. Unfortunately, this device is no longer being marketed. Only double chamber defibrillators with pacing capabilities are presently available: the Medtronic GEM III AT, an updated version of the Jewel AF and the Guidant PRIZM AVT. These devices can be patient-activated or programmed to deliver automatically ounce atrial tachyarrhythmias are detected, therapies including pacing or/and shocks. Attempts to define the group of patients who might benefit from these devices are described but the respective role of atrial defibrillators versus other non-pharmacologic therapies for AF, such as surgery and radiofrequency catheter ablation, remains to be determined. Advantages and limitations or atrial defibrillators and approaches to reduce shock related discomfort which may be a concern in some patients, are reviewed. Studies have shown that despite shock discomfort, quality of life was improved in patients with atrial defibrillators and the need for repeated hospitalizations was reduced. The cost of these devices remains a concern for the treatment of a non-lethal arrhythmia. Attention that atrial defibrillators will receive from cardiologists and from the industry in the future, will depend of the long-term results of other non-pharmacological options and of the identification of the group of AF patients which will require restoration and maintenance of sinus rhythm. But there is no doubt that selected subsets of patients with AF could benefit from atrial defibrillation.

Predictors of atrial antitachycardia pacing efficacy in patients affected by brady-tachy form of sick sinus syndrome and implanted with a DDDRP device

Predictors of ATP efficacy in brady/tachy patients.

BACKGROUND

Recent options to treat atrial tachyarrhythmias (ATA) include implantable devices delivering antitachycardia pacing therapies (ATP). No prospective study selected patients with higher chances of episode termination by ATP or indicated the most effective ATP use. Our aim was to study ATP efficacy in patients with brady-tachy form of sinus node disease (SND), identifying clinical factors, ATA characteristics, and device features predicting ATP efficacy.

METHODS AND RESULTS

Three hundred and sixteen patients (105 M, aged 71.1+/-8.8 years) received a DDDRP pacemaker and were prospectively followed. Median follow-up was 18 months: 37,125 ATA episodes occurred in 217 patients; ATP treated 5,536 of them. Overall, ATP efficacy was 50.0%. A multivariate analysis identified longer arrhythmia cycle lengths (OR=1.25; CI=1.07-1.47) and shorter delays to ATP delivery (OR=0.15; CI=0.10-0.22) as independent predictors of ATP efficacy for episodes preceded by >or=5 minutes of sinus rhythm. Additionally, ATP efficacy for all treated episodes was predicted by lower New York Heart Association (NYHA) class (OR=0.64; CI=0.42-0.98), episode classification as nonimmediate recurrence of ATA (non-IRAT) (OR=0.07; CI=0.02-0.33), absence of overlap in the device detection windows (OR=0.54; CI=0.32-0.91), and flecainide treatment (OR=2.22; CI=1.04-4.71).

CONCLUSIONS

In patients paced for SND, multivariate analysis shows that ATP efficacy is associated to longer arrhythmia cycle lengths, shorter ATP delivery delays, NYHA class I, episode classification as non-IRAT, absence of overlap in the atrial arrhythmia device detection windows, and flecainide treatment.

Pacemaker selection: time for a rethinking of complex pacing systems?The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal or of the European Society of Cardiology

Evidence from randomized trials indicates that the clinical benefits of dual-chamber (DDD) pacing are modest: (i) no significant differences exist between physiological pacing and single-chamber pacing in mortality and stroke; (ii) ventricular desynchronization resulting from chronic right-ventricular pacing in DDD mode, induces a significantly increased incidence of atrial fibrillation (AF) and heart failure hospitalizations; (iii) AF pacing prevention and therapy algorithms have shown a modest to minimal or absent efficacy; (iv) the widespread use of physiological pacemakers is not an economically attractive strategy. Thus, these data provide a reliable body of evidence on which to make more rationale clinical decisions for individual patients and policy decisions for health costs saving. The cheaper single-chamber AAI(R) or VVI(R) has been shown to satisfy both conditions in most cases of sinus node disease and AV block.

Recurrence of Atrial Tachyarrhythmias in Implantable Cardioverter-Defibrillator Recipients

BACKGROUND

Because the natural history of atrial tachyarrhythmia (AT) is not known in patients with implantable cardioverter-defibrillators (ICDs) but without device-based atrial therapies, we aimed to describe the characteristics and recurrence of AT in such patients.

METHODS

In this multicenter trial, 269 patients with standard indications for ICD placement and 2 episodes of AT in the preceding year received a dual-chamber ICD capable of logging AT. Patients were randomly assigned to 3-month periods of atrial therapies "on" or "off." This analysis considered only the 118 patients with atrial therapies programmed off at ICD placement.

RESULTS

Fifty-eight patients (49%) had at least 1 AT episode longer than 1 minute, and 21 (18%) had at least 1 prolonged episode (>24 hours). The median episode frequency for each patient (episodes per month) was 1.8 episodes longer than 1 minute, 0.8 longer than 1 hour, and 0 longer than 24 hours. The median AT burden was 12.2 hours per month.

CONCLUSIONS

Patients with standard ICD indications and history of AT have infrequent episodes, frequent short episodes, or prolonged episodes of AT-atrial fibrillation. However, the clinical characteristics examined did not distinguish among the groups. Improved diagnostic tools may help identify patients at risk for development of AT, thereby allowing specific therapies to be targeted to each group of patients.

Long-term reduction of atrial tachyarrhythmia recurrences in patients paced for bradycardia-tachycardia syndrome

BACKGROUND

Atrial tachyarrhythmias (AT) are considered progressive diseases. Several rhythm control therapies for treatment of AT have been proposed.

OBJECTIVES

The Italian AT500 Registry was designed to prospectively study long-term AT evolution in patients paced for the brady-tachy form of sinus node disease (BT-SND).

METHODS

Three hundred forty-six BT-SND patients received an antitachycardia dual-chamber pacemaker and were followed-up for a minimum of 12 months (median 19 months). Prevention and antitachycardia pacing (ATP) features were enabled in all patients.

RESULTS

During the observation period, 224 (65%) patients were treated by antiarrhythmic drugs and 45 (13%) patients were cardioverted. Five patients suffered a stroke, 4 transient ischemic attack, 22 permanent AT, and 98 AT recurrences longer than 7 days. AT mean cycle length changed from 246 to 270 ms, and the percentage of patients with AT-related hospitalizations significantly decreased with an annual 28% relative reduction. AT burden and the percentage of patients with AT recurrences longer than 2 days remained constant with time in the overall population but decreased significantly in the subgroup of patients who did not develop permanent AT. High ATP efficacy was associated with an increasingly higher prevention of AT recurrences longer than 2 days.

CONCLUSION

In a long-term observation of BT-SND patients, AT-related hospitalizations decreased significantly and mean AT cycle length increased significantly. The data suggest that rhythm control therapies induce inversion of AT progression.

Atrial Fibrillation in Patients with a Dual Defibrillator: Characteristics of Spontaneous and Induced Episodes and Effect of Ventricular Tachyarrhythmia Induction

BACKGROUND

The pattern of FF intervals during atrial fibrillation (AF) has been analyzed in induced and spontaneous AF episodes, after the induction of ventricular fibrillation (VF) and after atrial shock, in order to suggest practical considerations for AF management in patients implanted with antitachycardia devices.

METHODS

In 13 patients implanted with a dual-chamber defibrillator, FF intervals were analyzed during two separate induced AF episodes, before and after VF induction over AF, as well as during spontaneous AF episodes and after unsuccessful atrial shocks. The following parameters were considered: mean atrial cycle length (CL), atrial CL stability, and standard deviation of the atrial cycle.

RESULTS

The AF pattern had comparable characteristics considering two separate inductions of AF, as well as spontaneous AF episodes. Ventricular tachyarrhythmia induction resulted in a shortening of atrial CL (P < 0.02) and in a less organized AF pattern (P < 0.005). Changes in the FF interval after ineffective shock therapy showed a shortening of AF cycles after shocks with energies far below the defibrillation threshold.

CONCLUSIONS

(a) The AF pattern is reproducible in separate inductions of sustained AF and in spontaneous episodes, (b) dynamic changes involving a shortening of the AF cycle and an evolution to a less homogeneous pattern occur after VF induction, revealing a complex interplay between AF and VF, and (c) FF interval analysis after ineffective shock delivery may allow the relationship between delivered shock energy and effective defibrillation energy to be estimated, thereby providing practical suggestions for step-up protocols in atrial cardioversion.

High atrial antitachycardia pacing therapy efficacy is associated with a reduction in atrial tachyarrhythmia burden in a subset of patients with sinus node dysfunction and paroxysmal atrial fibrillation

BACKGROUND

Atrial tachycardia (AT) and atrial flutter that occur in association with paroxysmal atrial fibrillation (AF) can be successfully terminated by antitachycardia pacing (ATP) therapy. We hypothesized that atrial ATP therapy reduces AT/AF burden in a subset of patients with symptomatic bradycardia and frequent paroxysmal AT/AF.

OBJECTIVES

This study evaluated the effect of atrial ATP therapy on AT/AF burden in a pacemaker population with paroxysmal AF.

METHODS

We compared AT/AF burden in 261 patients who received a Medtronic AT500 pacemaker for treatment of AT/AF in the setting of symptomatic bradycardia based on device-classified atrial ATP efficacy < 60% and > or = 60%. Patients with > or = 10 device-detected episodes of AT/AF before and after atrial ATP therapy initiation were identified from four clinical studies performed in 72 centers worldwide.

RESULTS

The high efficacy group comprised 75 patients with atrial ATP efficacy > or = 60%. The low efficacy group comprised 186 patients with atrial ATP efficacy < 60%. AT/AF episode frequency was similar in both groups prior to ATP activation and decreased in the low efficacy group following ATP activation. Following atrial ATP initiation, total AT/AF burden increased slightly in the low ATP efficacy group (median 2.77 [25th-75th percentiles 0.84-5.86] hours/day vs 2.92 [0.59-8.12] hours/day, P = .01). In contrast, total AT/AF burden decreased significantly in the high efficacy group (median 2.46 [0.29-8.88] hours/day vs 0.68 [0.13-2.97] hours/day, P < .001).

CONCLUSION

Up to 30% of patients with frequent episodes of paroxysmal AF and symptomatic bradycardia experience a reduction in AT/AF burden from atrial ATP therapy over time.

Comparison of Induced and Spontaneous Atrial Tachyarrhythmias in Patients with a History of Spontaneous Atrial Tachyarrhythmias

INTRODUCTION

This retrospective study investigated whether induced episodes could be used to predict the morphology of future spontaneous atrial episodes.

METHODS

Eighty-two patients (64 +/- 12 years; 77% male; CAD in 60%; left ventricular ejection fraction 45 +/- 16%) with a history of atrial tachycardia or atrial fibrillation (AT/AF) were implanted with a dual-chamber implantable cardioverter defibrillator (ICD) and followed for 6 months. A total of 224 episodes of induced and spontaneous AT/AF were classified into type I, II, and III according to the method of Israel et al. and then compared based on average cycle length (CL) and atrial amplitude. Episodes were also grouped as "pace-terminable" or "nonpace-terminable" based on the CL definition of Gillis et al.

RESULTS

The analysis of 121 induced episodes (from 80 patients) and 103 spontaneous episodes (from 43 patients) showed that within each arrhythmia type, there were no significant differences in CL or mean amplitude between induced and spontaneous episodes. Additional analysis of patients that had both induced and spontaneous episodes (n = 41) showed 78% had at least one spontaneous episode that matched the induced episode. Fifty-seven percent of spontaneous episodes were considered to be pace-terminable based on CL.

CONCLUSIONS

Our data suggest that there is no significant difference between induced and spontaneous episodes of AT/AF of the same type. The majority of patients had at least one spontaneous episode of the same type as the induced episode, showing that induced atrial arrhythmias may be useful in predicting the morphology of future spontaneous episodes and in identifying patients potentially benefiting from atrial antitachycardia pacing.

Implantable Dual-Chamber Defibrillator for the Selective Treatment of Spontaneous Atrial and Ventricular Arrhythmias: Arrhythmia Incidence and Device Performance

INTRODUCTION

Atrial tachyarrhythmias are a common co-morbidity in patients with an ICD indication. Recently introduced ICD's are equipped to independently detect and treat atrial and ventricular tachyarrhythmias. The purpose of this prospective study was to evaluate the incidence and termination of spontaneous atrial and ventricular tachyarrythmias in patients with a history of atrial tachyarrhythmias.

METHODS AND RESULTS

Ninety patients, 70% male with an ICD indication and history of atrial tachyarrhythmia (LVEF 45 +/- 6%, [AT/AF indication 55 +/- 10, AT/VT 45 +/- 16], 46% CAD) were enrolled and 89 were implanted with a VENTAK PRIZM AVT (Guidant). Spontaneous atrial and ventricular tachyarrhythmias were printed and evaluated during an average follow-up period of 272 +/- 72 days utilizing the stored intracardial electrogram function of the device. Nineteen patients (21%) presented had only atrial tachyarrhythmias, 32 patients (36%) had both atrial and ventricular tachyarrhythmias and 18 patients (20%) had only ventricular tachyarrhythmias. Patients with only atrial tachyarrhythmias had a total of 3274 atrial episodes; 2002 terminated spontaneously, 1264 were treated with ATP and 8 with shock therapy. ATP was successful in 735 (58%) of 1264 episodes. Patients with both atrial and ventricular tachyarrhythmias had 7277 documented atrial tachyarrhythmias, 5231 terminated spontaneously, 1153 of 2009 were terminated by ATP (57.4%) and 37 by shock therapy (20 patient controlled). Atrial tachyarrhythmias identified as atrial flutter (AT) by the atrial rhythm classification (ARC) algorithm had a higher ATP conversion success rate than episodes identified as atrial fibrillation (AF); 66.7% for AT and 26.4% for AF. Patients with only ventricular tachyarrhythmias had 690 documented episodes, 401 terminated spontaneously, 248 (85.8%) were terminated by ATP and 41 by shock.

CONCLUSION

Seventy-seven percent of patients with an ICD indication had spontaneous atrial and/or ventricular tachyharrhythmias within the first 6 months after ICD implantation. ATP therapy terminated 58% of all atrial tachyarrhytmias and 66.7% of the atrial flutters. The dual chamber ICD detected, classified and terminated all ventricular tacharrhythmias appropriately.

Supraventricular arrhythmias: an electrophysiology primer

Supraventricular arrhythmias are the most wide-spread group of arrhythmias and affect all age groups. Atrial fibrillation is the most common arrhythmic disorder and is even more prevalent among the elderly. Due to their prevalence, it is imperative for the clinician to be informed about these arrhythmias and treatment considerations. This paper presents a basic review of the incidence, pathophysiology, diagnosis, and treatment of supraventricular arrhythmias, along with gender differences, and discusses important implications for the health care provider. A summary of common electrocardiogram findings in supraventricular arrhythmias is presented along with a brief overview of pharmacologic agents.

A novel implantable cardiac telemetry system for studying atrial fibrillation

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. Most in vivo experimental research on AF is performed in a surgical setting, on animals instrumented by external devices, or using commercial implantable pacemakers. This paper describes a novel implantable cardiac telemetry system, which allows the study of AF remotely in conscious and ambulatory animals over a few month period. To validate this concept, the system was built and implanted in a sheep for 3 months. During this period, the system was used to deliver chronic rapid atrial pacing for AF induction, and to record and measure atrial electrograms and atrial effective refractory period (AERP) daily. During the course of AF induction the AERP decreased, confirming the progression of the electrical remodeling process in the atria. Episodes of paroxysmal AF were successfully induced in the animal. Burst pacing therapy was delivered with the system, however, no AF termination was observed. Result shows that this telemetry-based pacing and monitoring system can be used to study AF in a conscious animal non-invasively for an extended period of time, making this system a unique research tool.

Ventricular high-rate episodes in pacemaker diagnostics identify a high-risk subgroup of patients with tachy-brady syndrome

OBJECTIVES

The purpose of this study was to evaluate the frequency and clinical significance of ventricular high-rate (VHR) episodes (ventricular rate >162 bpm) in patients with symptomatic bradycardia and paroxysmal atrial fibrillation (AF).

BACKGROUND

Newer pacemakers have enhanced diagnostic features that permit detection and storage of detailed information about the frequency, duration, and time of onset of multiple episodes of AF, atrial tachycardia (AT), and ventricular tachycardia (VT). However, the prevalence and prognostic value of AF associated with rapid ventricular rates in the pacemaker population are unknown.

METHODS

We prospectively followed 125 patients who received a Medtronic AT 500/501 pacemaker for symptomatic bradycardia and paroxysmal AF.

RESULTS

AF recurred in 112 patients (90%) during 22 +/- 8 months of follow-up. A total of 1,324 VHR episodes occurred in 38 patients (30%). Episodes with available electrograms (n = 560) were reviewed and classified as AF (n = 279; 50%), AT (n = 266; 47%) or VT (n = 15; 3%). AF burden was higher in patients with VHR episodes (median 1.9 vs 0.2 hours/day; P < .001). After controlling for AT/AF burden and heart disease, VHR episodes were a significant independent predictor of hospitalization for cardiovascular symptoms (odds ratio 2.92, 95% confidence interval 1.33-6.38; P = .007). Heart rate control improved over time in the cohort, and the frequency of VHR episodes decreased during follow-up (P < .001).

CONCLUSIONS

VHR episodes documented in the pacemaker diagnostics identify a high-risk subgroup of patients with AF. Monitoring VHR episodes may be useful for identifying pacemaker patients with AF who require more vigilant monitoring, additional investigations, and/or additional interventions.

Far-Field R Wave Oversensing in Dual Chamber Pacemakers Designed for Atrial Arrhythmia Management:. Effect of Pacing Site and Lead Tip to Ring Distance

INAMA, G., et al.: Far-Field R Wave Oversensing in Dual Chamber Pacemakers Designed for Atrial Arrhythmia Management: Effect of Pacing Site and Lead Tip to Ring Distance. The aim of the study was to determine the incidence and practical implications of far-field R wave oversensing (FFRWO) and its association with pacing site and lead tip to ring spacing (TTRS) in implantable devices designed to diagnose and treat atrial tachyarrhythmias and programmed with a fixed and short postventricular blanking period. The study included 395 patients who were implanted with a DDDRP pacemaker and prospectively followed. At implant and follow-up visits FFRWO was assessed by analyzing lead electrical measures and atrial tachyarrhythmic episodes collected in the device diagnostics. During a median follow-up of 12 months 11 (2.8%) of 395 patients showed a clinically significant FFRWO that induced inappropriate detection or pacemaker malfunctioning. The atrial pacing site of these 11 patients was right atrium appendage (RAA) for 3 patients, representing 1.1% of 254 RAA patients, coronary sinus ostium (CSO) for 7 patients, representing 7.4% of 94 CSO patients (P < 0.005 vs RAA), and lateral wall (LW) for 1 (2.9%) of 34 LW patients. The minimal value of the FFRWO to P wave ratio, measured at implant, associated with a clinically significant FFRWO was 0.6; therefore, a value of 0.5 was used as a cutoff to identify patients at risk of undesirable device behavior induced by FFRWO: there were 11 (9.6%) of 114 of RAA patients with short (< or = 10 mm) TTRS, 22 (18.8%) of 117 of RAA patients with long (> or = 17 mm) TTRS (P < 0.05 vs short TTRS), 21 (30.6%) of 64 of CSO patients short TTRS (P < 0.001 vs RAA patients with short TTRS) and 3 (30%) of 10 of CSO patients with long TTRS. The analysis showed that, despite the short postventricular blanking time, FFRWO inducing undesired functioning in AT500 pacemakers is infrequent (2.8% of patients). Compared to RAA, the CSO lead position was more frequently associated with FFRWO.TTRS < 10 mm was associated with lower risk of clinically significant FFRWO in RAA. (PACE 2004; 27:1221-1230).

The impact of atrial prevention and termination therapies on atrial tachyarrhythmia burden in patients receiving a dual-chamber defibrillator for ventricular arrhythmias

INTRODUCTION

This prospective, multicenter, randomized trial evaluated the effects of atrial prevention and termination therapies on atrial tachyarrhythmia (ATA) burden in patients with a standard indication for an implantable cardioverter defibrillator (ICD).

METHODS

A Jewel AF or GEM III AT ICD was implanted in 451 patients. At 1-month post-implant, patients were randomized to atrial prevention and termination therapies ON ( n = 199) or OFF ( n = 206) and followed for 6 additional months. Automatic atrial shocks were enabled in only 14% of the ON group. The follow-up time after randomization was 6.9 +/- 2.4 months ON versus 6.8 +/- 2.3 months OFF.

RESULTS

There were 126/405 (31.1%) patients who had AT/AF episodes during follow-up. Only four patients received a shock to treat ATA's during follow-up. The median ATA burden was 0 hours/month in both the ON and OFF groups ( P = 0.40). The mean ATA burden was 4.3 +/- 20.0 hours/month ON versus 9.0 +/- 50.0 hours/month OFF ( P = 0.11). In a subgroup of 192 patients with a history of ATA's, the median burden was 0 hours/month in the both groups ( P = 0.23). However, the mean burden in this subgroup was 7.6 +/- 27.1 hours/month ON versus 19.2 +/- 73.7 hours/month OFF ( P = 0.056).

CONCLUSIONS

In patients receiving an ICD for ventricular arrhythmias, no significant change in ATA burden was observed when atrial prevention and termination therapies were enabled. This may have been due to the low ATA burden in this population. In a subgroup of patients with history of ATA's, there was a trend towards a reduction in mean burden.

Accuracy of Atrial Tachyarrhythmia Detection in Implantable Devices with Arrhythmia Therapies

The clinical application of atrial tachyarrhythmia (AT) episode data stored by implantable devices is presently limited by the high proportion of inappropriate detection. We quantified the percentage of inappropriate AT detection in two implantable devices with AT diagnostics and therapies via meta-analysis of stored AT episodes from a number of clinical trials. The AT500 and GEM III AT, contain dual chamber logic to discriminate AT from ventricular tachycardia and far-field R wave (FFRW) oversensing using dual chamber bipolar electrograms. A subset of data from four clinical trials of 1,142 patients was considered. Manual analysis was performed on 21,553 stored episodes with atrial EGM and marker channel from 409 patients with stored episodes and the market-released device detection configuration. The percentage of episodes with inappropriate detection and termination was evaluated and compared between septal and nonseptal lead locations. The percentage of inappropriately detected episodes receiving ATP therapy was also determined. The percentage of episodes appropriately detected and the percentage of net episode duration (i.e., burden) recorded by the device were also determined from a separate analysis of 24-hour Holter recordings from a subset of 40 patients from one trial. Adjusted estimates of the percentage of appropriate [corrected] detection were 95.3% (93.5-96.7; 95% CI) for AT500 and 95.7% (84.3-98.9) for GEM III AT. Inappropriate detection was primarily due to FFRW oversensing or brief runs of premature atrial contractions (PACs). The device detected 100% of the sustained atrial arrhythmia episodes and 95.3% (range 76.1-99.9) of the net AT duration observed on the Holter recordings. AT detection was not influenced by atrial lead location. Appropriate detection of normal sinus rhythm at episode termination was 83.7% (80.7-86.3) for AT500 and 92.1% (84.5-96.2) for GEM III AT. Accurate detection and discrimination of FFRWs validates the reliability of AT diagnostic data and decreases the risk of inappropriate device therapy.

Long-term care of the patient with the atrial defibrillator

With an aging population, atrial fibrillation is becoming an increasingly common cause of hospital admission. Patients with recurrent, symptomatic persistent atrial fibrillation often require repeated admissions to the hospital for cardioversion. The development of the atrial defibrillator has empowered such patients to take charge of their condition and perform cardioversion on themselves at home. This liberates them from the worry of hospitalization and can increase patient confidence. The implantation of an atrial defibrillator, however, has some disadvantages, and long-term use of the device exposes patients to some of the psychological adaptations that occur in recipients of implantable devices. This article discusses in depth the patient selection process, the implantation procedure, the use of the atrial defibrillator, and problems that can arise during long-term follow-up.

Future prospects for implantable devices for atrial defibrillation

The success of the implantable cardioverter defibrillator (ICD) led to the concept of a device that would terminate atrial fibrillation (AF) using an implantable device. Implantable devices for AF are undergoing rapid evolution. Currently used devices combine pacing and cardioversion therapies to prevent and to treat AE Recent studies have shown that these devices are safe and can decrease the incidence of AF and improve quality of life significantly. Implantable devices for atrial defibrillation are likely to have an increasing role in the near future, particularly when they are used in combination with ICD and cardiac resynchronization therapy in which AF is both common and its termination is clinically beneficial.