Individualized selection of pacing algorithms for the prevention of recurrent atrial fibrillation: Results from the VIP registry

OBJECTIVES: The VIP registry investigated the efficacy of preventive pacing algorithm selection in reducing atrial fibrillation (AF) burden. BACKGROUND: There are few data identifying which patients might benefit most from which preventive pacing algorithms. METHODS: Patients, with at least one documented AF episode and a conventional antibradycardia indication for pacemaker therapy, were enrolled. They received pacemakers with AF diagnostics and four preventive algorithms (Selection and PreventAF series, Vitatron). A 3-month Diagnostic Phase with conventional pacing identified a Substrate Group (>70% of AF episodes with <2 premature atrial contractions [PACs] before AF onset) and a Trigger Group (< or =70% of AF episodes with <2 PACs before AF onset). This was followed by a 3-month Therapeutic Phase where in the Trigger Group algorithms were enabled aimed at avoiding or preventing a PAC and in the Substrate Group continuous atrial overdrive pacing was enabled. RESULTS: One hundred and twenty-six patients were evaluated. In the Trigger Group (n = 73), there was a statistically significant 28% improvement in AF burden (median AF burden: 2.06 hours/day, Diagnostic Phase vs 1.49 hours/day, Therapy Phase; P = 0.03304 signed-rank test), and reduced PAC activity. There was no significant improvement in AF burden in the Substrate Group (median AF burden: 1.82 hours/day, Diagnostic Phase vs 2.38 hours/day, Therapy Phase; P = 0.12095 signed-rank test), and little change in PAC activity. CONCLUSIONS: We identified a subgroup of patients for whom the selection of appropriate pacing algorithms, based on individual diagnostic data, translated into a reduced AF burden. Trigger AF patients were more likely responders to preventive pacing algorithms as a result of PAC suppression.     

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

Background

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

Objective

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

Methods

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

Results

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

Conclusions

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

     

New onset of pacemaker dependency after permanent pacemaker implantation

Pacemaker dependency has dangerous consequences under conditions of electromagnetic interference, unrecognized lead dysfunction, and battery depletion, and has been associated with cardiovascular and overall mortality. The aim of this study was to examine the incidence of new onset of pacemaker dependency during long-term follow-up after pacing system implantation. The study included 518 patients (mean age 72.9 +/- 10.4 years) who presented with intrinsic rhythms at the time of implantation. Indications for pacing were sick sinus syndrome (SSS) in 275 (53%) patients, AV block in 209 (40%), and AF with bradycardia in 34 (7%) patients. The mean follow-up was 3.7 +/- 2.7 years (range 1-17). Pacemaker dependency was defined as the absence of an intrinsic rhythm during backup pacing at 30 beats/min for 30 seconds. New onset of pacemaker dependency was observed in 23 (4.4%) of the 518 patients at a mean of 3.1 +/- 2.7 years of follow-up. Pacing indications were SSS in 6 (2.2%) of 275 patients, AV block in 15 (7.2%) of 209, and AF with bradycardia in 2 (5.9%) of 34. Patients with AV block had a significantly higher incidence of pacemaker dependency than patients with SSS (odds ratio 3.51; 95% CI 1.3 to 9.3; P = 0.012). The average annual rate of new pacemaker dependency was 1.6% during an 8-year follow-up. The incidence of new onset of pacemaker dependency varied among pacing indications, and was significantly higher in patients with AV block than patients with SSS.     

Diagnosis of Paroxysmal Atrial Fibrillation in Patients with Implanted Pacemakers: Relationship to Symptoms and Other Variables

Background: Atrial fibrillation (AF) is not always accompanied by clear-cut symptoms and symptoms suggestive of AF may not correspond to a genuine AF episode. The study prospectively evaluated the burden of asymptomatic AF episodes in pacemaker patients (for sick sinus syndrome) with a history of documented paroxysmal AF.
Methods: Consecutive patients were enrolled and implanted with dual-chamber pacemakers equipped with diagnostic features for AF monitoring. Each patient was instructed about typical AF symptoms and was asked to keep a detailed log of symptoms. Stored pacemaker data were analyzed using only AF episodes >30 s.
Results: The mean follow-up was 16 ± 6 months and 102 patients were enrolled (73 ± 7 years, 59 M). Thirteen patients (13%) dropped out with the development of permanent AF and their data were discarded. Twenty-three patients (26%) without device-stored AF episodes all reported at least one annotated AF episode. There were 1,245 device-stored AF episodes in 66 (74%) out of 89 patients. Patients reported 1,141 episodes of AF-related symptoms. Only 240 (21%) corresponded to a genuine device-stored AF event. The sensitivity and positive predictive value of symptoms to detect AF were respectively 19% and 21%. Episode duration, rate increase at the onset of the arrhythmia, heart disease, or antiarrhythmic drug therapy showed no statistically significant differences comparing symptomatic and asymptomatic episodes.
Conclusions: Many pacemaker patients with paroxysmal AF can develop AF-like symptoms in the absence of device-stored AF. AF-related symptoms have low sensitivity and low positive predictive value in patients with permanent pacemakers.     

Sinus and paced P wave duration and dispersion as predictors of atrial fibrillation after pacemaker implantation in patients with isolated sick sinus syndrome

The aim of this study was to prospectively evaluate the sinus and the paced P wave duration and dispersion as predictors of AF after pacemaker implantation in patients with isolated sick sinus syndrome (SSS). The study included 109 (69 women, mean age 72 +/- 11 years) patients with SSS, 59 with bradycardia-tachycardia syndrome (BTS). A 12-lead ECG was recorded before pacemaker implantation and during high right atrial and septal right atrial pacing at 70 and 100 beats/min. The ECGs were scanned into a computer and analyzed on screen. The patients were treated with AAIR (n = 52) or DDDR pacing. The P wave duration was measured in each lead and mean P wave duration and P wave dispersion were calculated for each ECG. AF during follow-up was defined as: AF in an ECG at or between follow-up visits; an atrial high rate episode with a rate of > or =220 beats/min for > or =5 minutes, atrial sensing with a rate of > or =170 beats/min in > or =5% of total counted beats, mode-switching in >/=5% of total time recorded, or a mode switching episode of > or =5 minutes recorded by the pacemaker telemetry. The ECG parameters were correlated to AF during follow-up. Mean follow-up was 1.5 +/- 0.9 years. None of the ECG parameters differed between patients with AF and patients without AF during follow-up, nor was there any difference between groups after correction for BTS and age. BTS was the strongest predictor of AF during follow-up (P < 0.001). P wave duration and dispersion measured before and during pacemaker implantation were not predictive of AF after pacemaker implantation in patients with isolated SSS.     

Effects of continuous and triggered atrial overdrive pacing on paroxysmal atrial fibrillation in pacemaker patients

Background: The aim of the study was to compare the effects of different pacing strategies to prevent paroxysmal atrial fibrillation (AF): triggered atrial overdrive pacing versus the combination of triggered and continuous overdrive pacing.
Methods : Patients with an indication for dual-chamber pacing (Selection 9000, Prevent AF; Vitatron B.V., Arnhem, the Netherlands) and a history of paroxysmal AF were randomized to triggered atrial pacing (three pacing functions, "triggered group": PAC Suppression™, Post-PAC Response™, and Post-Exercise Response™) or to the combination of continuous (Pace Conditioning™) and triggered atrial pacing (four pacing functions, "combined group"). After 3 months, there was a crossover to the other pacemaker setting.
Results : In 171 enrolled patients, the median AF burden of the combined group was with 2.1% versus 0.1% in the triggered group (P = 0.014). Fewer AF episodes were observed in the triggered (median: 7) than in the combined group (median: 116; P = 0.016). The combined group had more frequent atrial pacing (median 97%) than the triggered group with 85% (P < 0.001), but ventricular pacing was not significantly different with 95% and 96% in the combined and triggered group, respectively. After the crossover, the AF burden increased in the triggered group to 0.3% and decreased in the combined group to 0.4%.
Conclusions : Triggered atrial pacing functions alone resulted in a low AF burden. The additional activation of continuous atrial overdrive pacing increased the percentage of atrial pacing, but had no beneficial effects on the prevention of paroxysmal AF.     

Advanced Pacemaker Diagnostic Features in the Characterization of Atrial Fibrillation: Impact on Preventive Pacing Algorithms

YANG, A., et al .: Advanced Pacemaker Diagnostic Features in the Characterization of Atrial Fibrillation: Impact on Preventive Pacing Algorithms. Pacing algorithms to prevent PAF are mainly based on the suppression of premature atrial complexes (PACs), which play an important role in its initiation. In contrast to 24-hour ambulatory electrocardiograms, advanced pacemaker (PM) diagnostic features are capable of recording AF episodes during long follow-up periods and of characterizing AF in a detailed fashion. For the specific use of these algorithms, a detailed characterization of AF was performed in 91 dual chamber PM recipients with histories of AF. Fifteen patients with episodes of oversensing due to far-field signals or frequent episodes of "2:1-undersensing" of atrial flutter were excluded. The remaining 76 patients had high recurrence rates of AF (median 0.8 episodes/day), however, the majority of episodes lasted <7 minutes. Despite frequent PACs (median 10.8/hour) during sinus rhythm, a median of 66.4% of the AF episodes were preceded by <2 PACs/min before onset. In conclusion, frequent, short-lived AF episodes seem best suited for AF preventive pacing therapies. However, the small number of PACs preceding many AF episodes may limit the efficacy of PAC suppressing algorithms. (PACE 2003; 26[Pt. II]:310–313)     

Initial Experience with Mode Switching in a Dual Sensor, Dual Chamher Pacemaker in Patients with Paroxysmal Atrial Tachyarrhythmias

Mode switching algorithms have been developed to avoid tracking of atrial fibrillation (AF) or flutter (AFL) during DDD(R) pacing. Upon recognition of AF or AFL, the mode is switched to a nontracking, sensor driven mode. The Vitatron Diamond model 800 pacemaker does this on a beat-to-beat basis. Atrial events occurring within a “physiological range” (± 15 beats/min) calculated from a running average of the atrial rate are tracked. When atrial events are not tracked the escape interval is either determined by the sensor(s) or by a fallback algorithm thereby preventing large increases in V-V interval during mode switching. Loss of atrioventricular (AV) synchrony by atrial premature beats and after an episode of AF or AFL is prevented by atrial synchronization pulses (ASP), which are delivered after a safe interval (timed out from the sensed premature atrial event) has expired and before delivery of the next ventricular stimulus. We implanted 26 such devices in 18 men and 8 women with symptomatic second- or third-degree AV block and paroxysmal AF or AFL. Their ages ranged from 18–84 years (mean 60), and the follow-up ranged from 2–13 months (mean 8). During pacemaker check-up, exercise testing or 24-hour Holter monitoring one or more episodes of mode switching was documented in 8 patients. In these 8 patients a smooth transition (ventricular rate) from sinus rhythm to AF or AFL was documented on one or more occasions, without inappropriate increase in ventricular rate in the DDDR mode. None of the patients complained of palpitations. Appropriate rate response was seen in all patients during Holter monitoring and exercise. Restoration of AV synchrony with ASP was documented many times. In 2 patients the DDIR mode was programmed due to intermittent synchronization of ventricular stimuli to near incessant supraventricular tachycardia, which sometimes gave rise to asymptomatic slightly irregular ventricular paced rhythms below WO beats/min. Recognition of AF or AFL was reliable. No inappropriate increases in ventricular pacing rate were seen at the onset of or during AF or AFL. ASP is an effective method of maintaining AV synchrony and avoiding competitive atrial pacing.     

Mechanisms of onset of atrial fibrillation: a multicenter,prospective, pacemaker-based study

The aim of this study was to analyze the onset mechanisms of atrial tachyarrhythmias using a dedicated diagnostic system in 83 recipients of DDDR pacemakers implanted for standard clinical indications. The pulse generator was programmed in DDD mode, at 60 beats/min, and the diagnostic instrument was programmed to document atrial tachyarrhythmic episodes at rates >200 beats/min. Onset mechanism was defined as the combination of ambient rhythm and trigger. Various underlying rates and rhythms patterns, including tachycardia, increasing frequency of premature atrial complex (PAC), underlying heart rate increase, restart, and no specific underlying rhythm, and various triggers, including single, multiple, or short runs of PACs, sudden rate decrease, and sudden onset of atrial tachyarrhythmia were included in the combined classification. Atrial tachyarrhythmic episodes were documented on one follow-up interrogation in 48 of the 83 patients. The pacing indications consisted of high degree atrioventricular block in 19 patients, bradycardia-tachycardia syndrome in 22, and isolated sinus node dysfunction in 6 patients. The onset mechanisms of 318 episodes were recorded and analyzed. A variety of triggers were observed in 33 of the 48 patients, and 39 patients had various ambient rhythms. Among 20 documented onset mechanisms, the most common were increasing frequency of PAC + short runs (17%), no specific ambient rhythm + sudden onset (24%), and increasing frequency of PAC + sudden onset (12%). There were wide intra- and interpatient variations in onset mechanisms, suggesting that state-of-the-art pacemakers should represent versatile diagnostic tools and offer flexible pacing methods to refine the management of atrial tachyarrhythmias.     

Primary Prevention of Atrial Fibrillation: Does the Atrial Lead Position Influence the Incidence of Atrial Arrhythmias in Patients with Sinus Node Dysfunction? Results from the PASTA Trial

Introduction: PASTA (pacing of the atria in sinus node disease) is a prospective and randomized trial, assessing the effect of different atrial lead positions on the atrial fibrillation (AF) incidence in patients with sinus node disease (SND). Method: The atrial lead position is randomized to: (a) free right atrial wall, (b) right atrial appendage (RAA), (c) coronary sinus ostium (CS‐Os), or (d) dual site right atrial pacing (CS‐Os + RAA). The pacemakers (Vitatron Selection 9000 or Prevent AF, Vitatron B.V., Arnhem, The Netherlands) are programmed in DDDR 70 mode and the total follow‐up duration is 24 months. To describe the atrial rhythm state, pacemaker‐derived data (arrhythmia counter) were assessed for AF episodes. AF was considered as evident, if the AF burden (time in AF related to follow‐up interval) was >1% (i.e., 15 min/d). Follow‐up data after 24 months were evaluated. Results: The analysis evaluates 142 patients (77 male, 74.5 ± 7.8 years). There was no statistical significant difference with respect to the occurrence of AF between the four groups after 24 months (A: 36%; B: 38%, C: 32%, D: 48%). The percentage of atrial/ventricular pacing was in A: 78/76%, in B: 84/81%, in C: 70/65%, and in D: 79/69%. These differences were not significant. Conclusion: The evaluation of the AF burden >1% and the total AF burden after 24 months did not show differences in the incidence of AF in patients with dual chamber pacemaker therapy for SND. We were not able to demonstrate a significant influence of right atrial lead position on the incidence of AF recurrence.     

P wave duration and morphology predict atrial fibrillation recurrence in patients with sinus node dysfunction and atrial-based pacemaker

P wave duration and morphology have never been systematically evaluated as markers of AF in patients with a conventional indication to pacing. This study correlated sinus P wave duration and morphology and the incidence of AF in patients with sinus node dysfunction (SND), previous history of AF before implant, and atrial-based pacemaker. Included were 140 patients (86 men, 54 women; mean age 71.8 +/- 10.4 years) with recurrent paroxysmal AF and who received a DDD (128 patients) or AAI (12 patients) pacemaker for SND. Forty-nine patients had structural heart disease. Sinus P wave duration and morphology was evaluated in leads II, III. Twenty-two patients had an abnormal P wave morphology, diphasic (+/-) in 5 and notched (+/+) in 17. The basic pacemaker rate was programmed between 60 and 70 beats/min. Rate responsive function was activated in 65 patients. During a follow-up of 27.6 +/- 17.8 months, AF was documented in 87 patients. Forty-four patients developed permanent AF, following at least one episode of paroxysmal AF in 26 cases. Statistical analysis used Cox model regression. Univariate predictors of AF (P < 0.10) were drugs (mean: 2 +/- 1.4) and DC shock before pacing (16/140 patients), P wave duration (mean 112.5 +/- 24.6 ms), basic pacemaker rate (mean 68 +/- 5 beats/min), and drugs in the follow-up (mean 1.2 +/- 0.94). Multivariate analysis showed that P wave duration (b = 0.013, s.e. = 0.004; P = 0.003), and drugs before pacing (b = 0.2; s.e. = 0.08; P < 0.01) resulted in a significant independent predictor of AF. Actuarial incidence of patients free of AF at 30 months was 35%: 56% in patients with a P wave < 120 ms, and 13% in those with P wave > or = 120 ms (P < 0.01 by Score test). Univariate predictors of permanent AF were drugs and DC shock before pacing, left atrial size (mean 39 +/- 6 mm), P wave duration, abnormal P wave morphology (22/140 patients), and drugs in the follow-up. Multivariate analysis showed that P wave morphology was the most important predictor of permanent AF (b = -0.56, s.e. = 0.2; P = 0.008). Incidence of patients free of permanent AF at 30 months was 69%: 74% in patients with normal P wave, compared to 28% in the case of abnormal P wave morphology (P < 0.01). P wave duration and morphology are good markers of postpacing AF recurrence in patients with SND and an atrial-based pacemaker. This observation suggests that intra- and interatrial conduction disturbances be extensively evaluated before implantation, and the indication for atrial resynchronization procedures be reevaluated.     

Choosing the Stimulation Rate in Patients with Intermittent Bradycardia and a Single Lead Pacemaker

In order to assess the prevalence of intermittent bradycardia in a pacemaker population, we retrospectively evaluated the occurrence of intrinsic heart activity in 229 patients with ventricular pacing. Spontaneous heart activity was recorded in 60% of the patients. However, the stimulation rate had been decreased in onJy 40% of the patients in order to allow for longer periods of intrinsic heart activity. In the second part of the study we prospectively assessed differences in pacemaker utilization in 19 patients with intermittent bradycardia and single lead pacemakers. All patients were observed over four periods of 14 days, with the following pacing modes: 70 heats/min, 50 beats/min, hysteresis sensing 50 beats/min, and pacing 70 heats/min; and search hysteresis sensing 50 beats/min and pacing 70 beats/min. Search hysteresis pacing is a new feature that theoretically allows for a shorter time of pacing than that of hysteresis pacing. A reduction in the stimulation rate from 70 beats/min to 50 beats/ min resulted in a 60% reduction in pacemaker utilization (P < 0.05). Search hysteresis decreased pacemaker utilization by 33% (P < 0.05) There was no statistical difference between conventional hysteresis and fixed rate pacing at 70 beats/min. Most patients found fixed rate pacing preferable to hysteresis pacing. In order to minimize battery consumption and to avoid unfavorable hemodynamics in patients with ventricular pacing, the stimulation mode and rate should be optimized in patients with intermittent bradycardia to allow for longer periods of intrinsic heart activity.     

Predictors and clinical impact of atrial fibrillation after pacemaker implantation in elderly patients treated with dual chamber versus ventricular pacing

The Pacemaker Selection in the Elderly (PASE) trial was a prospective, multicenter, single blind, randomized comparison of single chamber, rate adaptive, ventricular pacing (VVIR) with dual chamber, rate adaptive pacing (DDDR) in 407 patients aged > or =65 years(mean 76 +/- 7 years, 60% male)with standard bradycardia indications for dual chamber pacemaker implantation. The incidence, predictors, and clinical consequences of atrial fibrillation (AF) developing after pacemaker implantation in the PASE trial were studied prospectively. During a median follow-up of 18 months, AF developed in 73 (18%) patients. Kaplan-Meier estimated cumulative incidences of AF in patients with sinus node dysfunction (n=176) at 18 months were 28% in the VVIR and 16% in the DDDR groups (P=0.08). After adjustment for other clinical variables using a Cox multivariate regression model, randomization to VVIR compared with DDDR pacing mode among patients with sinus node dysfunction was independently associated with a 2.6-fold increased relative risk (RR) of developing AF after pacemaker implantation (P=0.01). Other independent clinical risk factors for development of postimplant AF included a preimplant history of hypertension (P=0.02) or supraventricular tachyarrhythmias(P<0.04). Patients who developed AF had similar health related quality of life scores and cardiovascular functional status after 18 months of pacing as patients who remained free of AF. The RR of death, stroke, or heart failure hospitalization was not increased in patients who developed AF. Thus, in the elderly patients with sinus node dysfunction requiring permanent pacing, DDDR pacing mode protected against the development of AF. However, development of AF after pacemaker implantation in this population was not associated with a significant impact on quality-of-life, functional status, or other clinical endpoints during 18 months of follow-up.     

Clinical Evaluation of Morphology Discrimination: An Algorithm for Rhythm Discrimination in Cardioverter Defibrillators

The aim of this study was to test the new morphology discrimination diagnostic algorithm for ICDs that differentiates supraventricular tachycardias (SVTs) from VTs by analysis of ventricular depolarization complexes morphology. Twenty-five patients implanted with a St. Jude Ventritex single chamber ICD were studied during electrophysiological evaluation at predischarge and were followed for 7 +/- 4 months. Sensitivity and specificity for VT detection and overall diagnostic accuracy of the morphology discrimination algorithm were calculated on 326 detected events. At electrophysiological evaluation, the algorithm was tested during 67 episodes of right atrial pacing, during 119 episodes of RV pacing (at basal interventricular septum and RV apex) and during 27 episodes of sustained AF: specificity was 98%, sensitivity was 66%, and diagnostic accuracy was 80%. All episodes of AF were correctly diagnosed as SVT. Exclusion of detections related to pacing at the basal interventricular septum, resulted in a specificity of 98%, a sensitivity of 85%, and a diagnostic accuracy of 93%. During follow-up, evaluation of the morphology discrimination algorithm on 113 spontaneous episodes (31 VTs, 31 AF, 7 SVTs, and 44 sinus tachycardias) exhibited a specificity of 89%, a sensitivity of 100%, and a diagnostic accuracy of 92%. In conclusion, the morphology discrimination algorithm exhibits a high specificity in discriminating VTs from SVTs, although with a corresponding reduction in sensitivity. The preliminary experience on spontaneous episodes is promising. To correct for the reduction in sensitivity, it is advisable to use this algorithm in parallel with other algorithms for rhythm discrimination (sudden onset, stability) coupled with extended high rate.     

High rate atrial tachyarrhythmia detections in implantable pulse generators: low incidence of false-positive detections. The PA Clinical Trial Investigators

Some newer pulse generators have enhanced diagnostic features that provide information on the frequency, date, time of onset, and duration of atrial and/or ventricular tachyarrhythmias. However, the sensitivity and specificity of device-based atrial tachyarrhythmia detections may vary and depend, in part, on lead position and selected programming parameters. The prevalence of inappropriate detections of paroxysmal atrial fibrillation (PAF) was investigated in 97 patients who received a Thera DR pacemaker 3 months prior to a planned AV node ablation. Patients were randomized to no atrial or to rate adaptive atrial pacing therapy and followed for 3 months. Following a total AV node ablation, patients were randomized to DDDR versus VDD pacing and followed for 1 year. The high rate atrial episode diagnostic feature was used for detection of PAF and the diagnostic data were retrieved during follow-up visits. Criteria were developed to identify oversensing due to near-field P wave detections, far-field R wave detections, or competitive atrial pacing as causes of false-positive atrial tachyarrhythmia detections. A total of 1,636 detections of PAF were recorded in patients preablation. Only 48 episodes (2.9%) were characterized as false-positive detections; 25 episodes (1.5%) were classified as oversensing, and 23 episodes (1.4%) were classified as competitive atrial pacing. A total of 3,061 detections of PAF were recorded postablation. Only four episodes (0.1%) were classified as oversensing. Thus, the diagnostic atrial tachyarrhythmia detection feature in newer pacemakers is an effective method for evaluating the time course of PAF in patients with implantable pulse generators.     

Microdislodgment of ventricular pacing lead undetectable during rapid pacing one year after implantation

A 71-year-old woman had undergone valvular heart surgery in 1981, and implantation of a permanent ventricular pacemaker for ventricular pauses during atrial fibrillation in 2001. One year after pacemaker implantation, she complained of faintness. When pacing at 100 beats/min the pacemaker functioned properly. However, pacing and sensing failure was detected at a pacing rate of 60 beats/min. At rapid pacing rates, the lead tip was in closer contact with the endocardium, and its microdislodgment was undetectable. The symptoms have resolved since the lead was repositioned.     

VDDR Pacing after His-Bundle Ablation for Paroxysmal Atrial Fibrillation: A Pilot Study

His-bundle ablation followed by pacemaker implantation is today a widely accepted therapeutic choice when drug refractoriness of symptomatic AF is evident. The selection of pacing mode in patients suffering from paroxysmal AF is still controversial. Preservation of AV synchrony is an attractive option in patients with paroxysmal AF who undergo His-bundle ablation. The purpose of this study was to examine prospectively the contribution of VDDR pacing for preservation of AV synchrony. After His-bundle ablation a VDDR pacing system was implanted in 17 patients with paroxysmal AF, and all antiarrhythmic drugs were withdrawn. The endpoint of the study was defined as the onset of chronic AF. To document the onset of chronic AF 48-hour Holter recordings were made every 6–8 weeks. After a mean followup of 18.2 (range 14–21) months, VDDR pacing is still operative in 13 patients (77%). Four patients developed chronic AF after a mean follow-up of 6 months. Of several baseline characteristics, only the intraatrial P wave at implantation was significantly smaller in patients developing chronic AF than in patients in whom the VDDR mode is still operative. This pilot study suggests that VDDR pacing is an attractive pacing method for patients with paroxysmal AF after His-bundle ablation. A low intraatrial P wave electrogram at implant was associated with a higher risk for the development of chronic AF.     

Detection of Atrial Fibrillation by Implanted Devices with Wireless Data Transmission Capability

Remote telemetry may facilitate the management of implantable devices. We tested the reliability of a new automatic, wireless home monitoring (HM) system that archives data every 24 hours. We retrospectively analyzed archival data from 276 consecutive pacing system implants to define temporal atrial fibrillation (AF) patterns and associated ventricular rate. An "AF day" was defined by a >20%/24 hour mode switch (MS) duration, irrespective of the MS number. Management decisions resulting from transmissions were noted. A pilot study confirmed that 89% of 22,356 transmissions were successful, of which >90% were received in <5 minutes. Data integrity was 100% preserved. Overall, AF developed in 29 patients (10.5%), representing a total of 645 AF days (mean = 22.2 ± 29.6 AF, median = 9 days), over 12 ± 2 months of monitoring. AF was infrequent (50% of 24 hours. Ventricular rates during 645 AF days in 29 patients averaged 95.1 ± 9.9 beats/min (median = 94 beats/min). Ventricular rates were >80 beats/min in 25 ± 30 AF days (median = 11 days). HM enabled rapid anticoagulation decisions. In recipients of implantable devices, automatic wireless telemetry with HM was efficient and reliable. Its application may overcome some current challenges in AF management by early notification and precise measurement of both AF burden and ventricular rate during AF.     

Identification of Atrial Fibrillation Episodes in Ambulatory Electrocardiographic Recordings: Validation of a Method for Obtaining Labeled R-R Interval Files

MURGATROYD, F.D., et.al .: Identification of Atrial Fibrillation Episodes in Ambulatory Electrocardiographic Recordings: Validation of a Method for Obtaining Labeled R-R Interval Files . Current systems for analyzing ambulatory electrocardiograms (ECGs) are unable to distinguish precisely between sinus rhythm and atrial fibrillation (AF) episodes, and are unable to produce RR interval listings that distinguish AF from sinus rhythm on a beat-to-beat basis. We describe a method for obtaining such a computerized listing ("Composite Rhythm" file) from ambulatory recordings containing episodes of AF. The file lists the rhythm of each beat, its real time, and the QRS complex morphology. A visual inspection is made of a full printout of the recording to identify the precise time of onset and termination of each episode of AF. These times are entered into a computer and identified with the corresponding beats on a conventional RR interval file generated by Holter analysis. The method was validated using 1-hour segments from 20 ambulatory ECGs containing 145 episodes of AF. These were visually identified by four independent observers with a mean sensitivity of 99.1%. The first beat of AF was identified concordantly in 96% of episodes, with a discrepancy of ≤ 3 beats in the other episodes. The times of 200 selected QRS complexes were then entered into the computer by each observer; 91.1 % of these complexes were identified exactly and 100% were identified to within one beat. The Composite Rhythm files have several potential applications for testing AF detection algorithms and studying the mode of onset of AF.     

Effect of right atrial overdrive pacing in the prevention of symptomatic paroxysmal atrial fibrillation: a multicenter randomized study,the PAF-PACE study

The aim of this study was to assess if right atrial overdrive pacing can suppress symptomatic episodes of paroxysmal atrial fibrillation (PAF) in patients without bradyarrhythmias. Forty-two patients with frequent and symptomatic PAF without other pacing indication had a pacemaker implanted after a 4-week run-in period, during which the frequency of symptomatic PAF episodes and the mean heart rate were objectively documented. Depending on the mean heart rate recorded during run-in, the pacemaker was programmed in random order to right atrial AAI pacing at 10-19 beats/min > mean heart rate (medium overdrive [MO]), at 20-29 beats/min > mean heart rate (high overdrive [HO]) and to no pacing (OAO mode) for 4-12 weeks each using a crossover design. In the 35 patients who completed the protocol, the number of symptomatic episodes of PAF (>30-second duration) per week was significantly lower during MO pacing (median 0.88, P = 0.001, n = 35) and during HO pacing (median 0.75, P = 0.002, n = 20) than during OAO (median 2.02 and 2.04, respectively). There was no difference between MO and HO pacing in the 20 patients paced at both rates (0.97 vs 0.75, P = 0.33). Seven patients did not complete the protocol due to persistent atrial fibrillation (n = 4), angina pectoris requiring surgery (n = 1), and unwillingness to continue the study due to improvement (n = 1) or worsening (n = 1) of symptoms during the study periods. Right atrial overdrive pacing can reduce the number of symptomatic PAF episodes in patients with frequent and drug refractory PAF but without bradyarrhythmias.