Atrial high rate episodes detected by pacemaker diagnostics predict death and stroke: report of the Atrial Diagnostics Ancillary Study of the MOde Selection Trial (MOST)

Management of Far-Field R Wave Sensing for the Avoidance of Inappropriate Mode Switch in Dual Chamber Pacemakers: Results of the FFS-Test Study

BACKGROUND AND OBJECTIVE

Far-field R wave sensing (FFS) in the atrial channel of dual chamber pacemakers is a relevant source for inappropriate mode switch from the DDD mode to the DDI or VDI mode. Inappropriate loss of atrioventricular synchrony due to false positive mode switch is hemodynamically disadvantageous, may induce atrial tachyarrhythmias, can lead to pacemaker syndrome, and impairs the reliability of pacemaker Holter data. The aim of the study was to determine whether individual adjustment of the postventricular atrial blanking period (PVAB) based on an additional test is effective in avoiding inappropriate mode switch due to FFS when compared with standard programming of the PVAB.

METHODS

A total of 207 patients were supplied with a St. Jude Medical Identity DR or Identity ADx DR dual chamber pacemaker for sinus nodal disease (n = 84), atrioventricular block (n = 79), binodal disease (n = 35), or other indications (n = 9). At hospital discharge, they were randomized to an individually optimized PVAB (n = 100) or to a control group with the PVAB left at the nominal of 100 msec (n = 107). Primary endpoint was the occurrence of inappropriate mode switch due to FFS within 3 months after pacemaker implantation assessed by stored electrograms of the pacemaker.

RESULTS

At the 3-month follow-up, 28/107 (26%) patients with the standard programming of the PVAB showed at least one episode of inappropriate mode switch due to FFS versus 10/100 (10%) patients with optimized PVAB (P < 0.01). The optimized PVAB was shorter than the nominal PVAB in about one-third of patients and longer in about two-third of patients. Different atrial lead localizations were not associated with the occurrence of inappropriate mode switch.

CONCLUSIONS

Individual adjustment of the PVAB significantly reduces the incidence of inappropriate mode switch due to FFS.

ASymptomatic atrial fibrillation and Stroke Evaluation in pacemaker patients and the atrial fibrillation Reduction atrial pacing Trial (ASSERT)

Asymptomatic atrial fibrillation (AF) is common and may have the same prognostic implications as symptomatic AF. Among patients receiving dual-chamber pacemakers, it is now possible to quantify asymptomatic AF accurately. Most of these episodes are of short duration, often lasting only seconds to minutes and are called atrial high-rate episodes (AHRE) to distinguish them from the longer episodes of overt AF. To understand properly the clinical importance of asymptomatic AF, a large study of pacemaker patients without clinically overt AF is required. ASSERT is a multicenter, cohort follow-up, and single-blinded randomized trial in elderly hypertensive patients with a pacemaker recently implanted for sinus or atrioventricular node disease. The goals of this trial are to evaluate whether the detection of AHRE with pacemaker telemetry predicts an increased risk of stroke and other vascular events and to evaluate if atrial overdrive pacing reduces symptomatic AF. ASSERT is evaluating the hypothesis that among pacemaker patients without a previous history of AF, detection of AHRE predicts an increased risk of stroke and systemic embolism. The second hypothesis to be tested is that overdrive atrial pacing will reduce the risk of symptomatic AF in pacemaker patients without a previous history of AF. Finally, a 400-patient substudy will use the noninvasive testing capabilities of the patients' pacemaker to evaluate changes in atrial electrophysiology over 2 years. This substudy will determine if atrial electrical remodeling is detectable in pacemaker patients and if it is associated with the development of AF.

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.

Incidence of Atrial Tachyarrhythmias in Pacemaker Patients: Results from the Balanced Evaluation of Atrial Tachyarrhythmias in Stimulated Patients (BEATS) Study

OBJECTIVES

The prospective Balanced Evaluation of Atrial Tachyarrhythmias in Stimulated patients (BEATS) study compared atrial tachyarrhythmia (AT) detection by means of serial ECG recordings versus device detection.

BACKGROUND

The annual incidence of AT in patients with dual-chamber pacemakers may be significantly underestimated based on ECG and Holter recordings.

METHODS

A DDD(R) device capable of AT-triggered dual-channel electrogram (EGM) storage was implanted in 254 patients (70 +/- 11 years, 159 men) with a class I pacing indication. Patients were seen at 6, 26, and 52 weeks after pacemaker implantation. At all visits, symptoms were checked, surface ECGs were recorded including a 24-hour Holter recording at 6 weeks, and the pacemakers were interrogated. Primary study endpoint was AT documentation by surface ECG/Holter versus stored EGMs. Secondary endpoints consisted of the association between patients' symptoms and AT documentation, and of the AT incidence depending on pacing indication and a history of AT.

RESULTS

ATs were documented by ECG/Holter recordings in 37 patients (15%) and by stored EGMs in 137 patients (54%) (P < 0.0001). Symptoms were absent in 108 of 137 patients (79%) with device-documented AT but present in 70 of 117 patients (60%) without AT documentation. AT documentation was more frequent in patients with a history of AT but not in patients with sinus node compared to AV node disease.

CONCLUSION

ATs occur in pacemaker patients significantly more frequently than estimated by ECG/Holter recordings. Only the analysis of device-stored EGMs allows reliable assessment of the AT burden.

Modelling the health benefits and economic implications of implanting dual-chamber vs. single-chamber ventricular pacemakers in the UK

AIMS

To estimate the consequences of managing bradycardia due to sinoatrial node disease or atrioventricular block with dual-chamber vs. single-chamber ventricular pacemakers.

METHODS AND RESULTS

A discrete-event simulation was conducted to predict outcomes over 5 years. Patients could develop post-operative complications, clinically relevant pacemaker syndrome leading to replacement of single-chamber with dual-chamber, atrial fibrillation (AF; which if chronic might require anticoagulants) or stroke. Survival, quality-adjusted life years (QALYs), complications, and associated direct medical costs were estimated (2003 British Pounds pounds sterling). Identical patients were simulated after receiving a single-chamber device or a more expensive dual-chamber pacemaker. Probabilities of conditions were obtained from clinical trials. Benefits were discounted at 1.5% and costs at 6%. Post-operative complications increased from 6.4% with single-chamber to 7.7% with dual-chamber but AF decreased (22 vs. 18%) as did clinically relevant pacemaker symptoms (16.8 vs. 0%). Approximately 4300 pounds sterling were accrued per patient over 5 years. Additional health benefits with dual-chamber are achieved at a mean net cost of 43 pounds sterling per patient, leading to 0.09 QALY with a cost-effectiveness ratio of 477 pounds sterling/QALY.

CONCLUSION

Implanting the costlier device increases the cost of the initial operation; however, this is expected to be offset by a reduction in costs associated with re-operations and AF.

Heart failure during cardiac pacing

BACKGROUND

Right ventricular apical (RVA) pacing creates abnormal left ventricular contraction, hypertrophy, and reduced pump function. The adverse effects of ventricular desynchronization may explain the association of RVA pacing with an increased risk of heart failure hospitalization (HFH) in clinical trials.

METHODS AND RESULTS

Baseline and postimplantation variables were used to predict HFH in the Mode Selection Trial, a 2010-patient, 6-year trial of dual-chamber (DDDR) versus ventricular (VVIR) pacing in sinus node dysfunction. A Cox model showed that New York Heart Association (NYHA) class at baseline and follow-up predicted HFH (hazard ratio [HR], 3.99; 95% confidence interval [CI], 2.74-5.79 for NYHA class III/IV and HR, 2.17; 95% CI, 1.54-3.04 for NYHA class II versus class I); other predictors were heart failure (HR, 2.30; 95% CI, 1.70-3.11), atrioventricular (AV) block (HR, 1.48; 95% CI, 1.11-1.97), and myocardial infarction (MI)(HR, 1.37; 95% CI, 1.00-1.86). Postimplantation predictors were VVIR cumulative percent ventricular pacing (Cum%VP) >80 (HR, 3.58; 95% CI, 1.72-7.45), DDDR Cum%VP >40 or VVIR Cum%VP < or =80 (HR, 1.81; 95% CI, 0.94-3.50) versus DDDR Cum%VP < or =40; whether QRS duration (QRSd) was paced or spontaneous (HR, 2.21; 95% CI, 1.39-3.54; spontaneous versus paced); and drugs for atrial fibrillation (HR, 1.60; 95% CI, 1.19-2.15). Low baseline ejection fraction (EF) and postimplantation RVA-paced or spontaneous QRSd predicted HFH; the increased risk with QRSd was steeper for normal versus low EF (HR, 1.18; 95% CI, 1.11-1.27; versus HR, 1.08; 95% CI, 1.01-1.15; for a 10-ms increase); at a QRSd of approximately 200 ms, normal- and low-EF patients had equivalent risk. HFH risk nearly doubled when VVIR Cum%VP was < or =80 or DDDR Cum%VP was >40 versus DDDR Cum%VP < or =40 and was additive with other risk factors.

CONCLUSIONS

Differences in HFH risk can be explained by interactions between substrate (atrial fibrillation, AV conduction, heart failure, MI, EF) and pacing promoters (ventricular desynchronization-paced QRSd and Cum%VP, and AV desynchronization-pacing mode). Management of RVA pacing is important for reducing the risk of HFH, particularly among patients with low EF and heart failure.

Rationale and design of a prospective study of the clinical significance of atrial arrhythmias detected by implanted device diagnostics: The TRENDS study

BACKGROUND

Sustained atrial fibrillation (AF) is a common risk factor for stroke. While intermittent AF also appears to pose a substantial stroke risk, the quantitative relationship between the percentage of time spent in AF and stroke risk is poorly specified and "intermittent" AF is not the same as paroxysmal AF. Improved assessment of the impact of AF burden on stroke risk will allow more targeted and safer use of antithrombotic therapy.

METHODS AND RESULTS

The primary objective of this study is to determine if AT/AF (all device detected atrial tachyarrhythmias, including atrial flutter, atrial fibrillation, and atrial tachycardia) burden over a 30 day period is an independent predictor of the occurrence of ischemic stroke, transient ischemic attack (TIA) and/or systemic embolism in subjects not receiving anticoagulation therapy. TRENDS is a prospective, post-market, non-randomized, multicenter study designed to enroll 3100 subjects who have an independent Class I/II indication for cardiac rhythm device implantation and who have demographic features suggestive of an increased risk for thromboembolic complications related to AT/AF. All implanted devices will have the ability to collect long-term AT/AF burden trending data and will be equivalently programmed to ensure consistent data collection. All subjects will be followed with device interrogations every 3 months and clinic visits every 6 months for 1 year. Subjects with a documented history of AT/AF prior to enrollment and those who develop AT/AF during the 12-month follow-up will be followed until the last subject enrolled in the study has completed their 24-month follow-up.

CONCLUSIONS

The results of the TRENDS study should help clarify the implications of data retrieved from an implantable device with regard to the risk for thromboembolic complications from atrial arrhythmias, even in the absence of symptoms.

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.

Monitored atrial fibrillation duration predicts arterial embolic events in patients suffering from bradycardia and atrial fibrillation implanted with antitachycardia pacemakers

OBJECTIVES

The aim of our study was to evaluate arterial embolism (AE) occurrence rates and predictors in patients suffering from bradycardia and wearing a pacemaker with antitachycardia pacing therapies.

BACKGROUND

Atrial fibrillation (AF) is associated with a high incidence of AE.

METHODS

A total of 725 patients (360 men, age 71 +/- 11 years) were implanted with a DDDRP pacemaker (Medtronic AT500, Medtronic Inc., Minneapolis, Minnesota). At baseline 225 (31.0%) patients received antiplatelet therapy and 264 (36.4%) patients received anticoagulation agents.

RESULTS

Over a median 22-month follow-up (25th to 75th interquartile range 16 to 30 months), AE occurred in 14 (1.9%) patients: 7 patients suffered a nonfatal ischemic stroke (0.6% per year), 4 patients had transient ischemic attack (0.34% per year), and 3 patients had embolic complications. Among baseline patients' characteristics, multivariate logistic analysis showed that embolic events are independently associated to ischemic heart disease (7.0 odds ratio [OR], 95% confidence interval [CI] 2.3 to 21.3, p = 0.001), prior embolic event (7.3 OR, 95% CI 1.2 to 43.9, p = 0.029), diabetes (5.0 OR, 95% CI 1.2 to 15.7, p = 0.032), and hypertension (4.1 OR, 95% CI 1.1 to 15.6, p = 0.036). The risk of embolism, adjusted for known risk factors, was 3.1 times increased (95% CI 1.1 to 10.5, p = 0.044) in patients with device-detected atrial fibrillation episodes longer than one day during follow-up.

CONCLUSIONS

In a cohort of patients with bradycardia and AF, arterial embolism was common in patients with ischemic cardiopathy, hypertension, diabetes mellitus, and in patients with known stroke risk factors. Atrial fibrillation occurrences longer than one day were independently associated with embolic events.

Catheter ablation treatment in patients with drug-refractory atrial fibrillation: a prospective, multi-centre, randomized, controlled study (Catheter Ablation For The Cure Of Atrial Fibrillation Study)†

AIMS

We conducted a multi-centre, prospective, controlled, randomized trial to investigate the adjunctive role of ablation therapy to antiarrhythmic drug therapy in preventing atrial fibrillation (AF) relapses in patients with paroxysmal or persistent AF in whom antiarrhythmic drug therapy had already failed.

METHODS AND RESULTS

One hundred and thirty seven patients were randomized to ablation and antiarrhythmic drug therapy (ablation group) or antiarrhythmic drug therapy alone (control group). In the ablation group, patients underwent cavo-tricuspid and left inferior pulmonary vein (PV)-mitral isthmus ablation plus circumferential PV ablation. The primary end-point of the study was the absence of any recurrence of atrial arrhythmia lasting >30 s in the 1-year follow-up period, after 1-month blanking period. Three (4.4%) major complications were related to ablation: one patient had a stroke during left atrium ablation, another suffered transient phrenic paralysis, and the third had a pericardial effusion which required pericardiocentesis. After 12 months of follow-up, 63/69 (91.3%) control group patients had at least one AF recurrence, whereas 30/68 (44.1%) (P<0.001) ablation group patients had atrial arrhythmia recurrence (four patients had atrial flutter, 26 patients AF).

CONCLUSION

Ablation therapy combined with antiarrhythmic drug therapy is superior to antiarrhythmic drug therapy alone in preventing atrial arrhythmia recurrences in patients with paroxysmal or persistent AF in whom antiarrhythmic drug therapy has already failed.

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.

Controversies in pacing: Indications and programming

This article reviews controversies in cardiac pacing in four areas: methods to prevent unnecessary right ventricular pacing and optimal ventricular pacing sites in the bradycardia population, pacing for prevention of atrial fibrillation (AF), a novel pacing technique for the treatment of heart failure, and pacing for the treatment of sleep apnea. Frequent right ventricular pacing has been reported to increase the incidence of AF and congestive heart failure. However, many patients with pacemakers for bradycardia have intrinsic atrioventricular conduction most of the time. Optimal programming of pacemakers and new algorithms designed to reduce unnecessary ventricular pacing are discussed. Pacing algorithms for prevention of AF have generally been shown to be ineffective. Atrial antitachycardia pacing has been shown to reduce the burden of atrial tachyarrhythmias in selected patients. Cardiac contractility modulation has recently been reported to be a promising new approach to the treatment of heart failure. Some pacing techniques may be effective in the treatment of sleep apnea but larger, long-term clinical trials are required to demonstrate a significant clinical benefit.

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 (<AF 30 days/year) in 80% of patients. When AF did occur, 83% patients had >/=1 day during which the AF burden was >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.

Asymptomatic atrial fibrillation: demographic features and prognostic information from the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study

BACKGROUND

Atrial fibrillation (AF) may occur without symptoms. Little is known about demographic features and prognostic information in patients with asymptomatic AF.

METHODS

In the AFFIRM study, 4060 patients were randomized to either rhythm or rate control. At baseline, patients were identified as asymptomatic if they answered "no" to a 15-item questionnaire related to cardiac symptoms during AF in the 6 months before study entry.

RESULTS

There were 481 (12%) asymptomatic patients at baseline. Compared with symptomatic patients, asymptomatic patients were more often men and had a lower incidence of coronary artery disease and congestive heart failure, but had more cerebrovascular events. Asymptomatic patients had a longer duration of AF, a lower maximum heart rate, and better left ventricular function. They received fewer cardiac medications and fewer therapies to maintain sinus rhythm. At 5 years, there was a trend for better survival in asymptomatic patients (81% vs 77%, P = .058), and they were more likely to be free from disabling stroke or anoxic encephalopathy, major bleeding, and cardiac arrest (79% vs 67%, P = .024). However, mortality and major events were similar after correction for baseline differences.

CONCLUSIONS

Patients with asymptomatic AF have less serious heart disease but more cerebrovascular disease. Asymptomatic patients receive different therapies than symptomatic patients. However, the absence of symptoms and the differences in treatment does not confer a more favorable prognosis when differences in baseline clinical parameters are considered. Anticoagulation should be considered in these patients.

Role of transtelephonic electrocardiographic monitoring in detecting short-term arrhythmia recurrences after radiofrequency ablation in patients with atrial fibrillation

OBJECTIVES

The aim of our study was to determine the incidence of asymptomatic recurrences of atrial fibrillation (AF) by daily transtelephonic (TT) electrocardiographic (ECG) monitoring, as compared with standard ECG and 24-h Holter recording, in patients who underwent radiofrequency catheter ablation (RCA) of AF.

BACKGROUND

The efficacy of RCA of AF is usually evaluated by means of patients' symptoms.

METHODS

Seventy-two patients with paroxysmal (n = 37) or persistent (n = 35) drug-refractory AF underwent circumferential RCA of the pulmonary vein (PV) ostia. Left isthmus ablation was performed in 57 patients, and cavotricuspid isthmus ablation was done in 69 patients. Patients were scheduled to obtain an ECG and Holter recordings one and four months after ablation, as well as a daily TT ECG, from 30 to 120 days after ablation or in the event of symptoms.

RESULTS

A total of 5,585 TT ECGs were obtained (mean 77.5 per patient). In 20 patients (27.8%), AF recurrences were recorded during TT ECG, whereas ECG and Holter monitoring revealed AF recurrences in 10 patients (13.9%, p = 0.001). Ten patients had at least one asymptomatic AF recurrence, and eight were completely asymptomatic. The ECG recorded in the event of symptoms always showed AF.

CONCLUSIONS

Transtelephonic ECG is better than standard ECG and 24-h Holter recordings in evaluating AF relapses after RCA, thus decreasing the short-term success of ablation from 86% to 72%. The absence of symptoms should not be interpreted as absence of AF, as 50% of patients were asymptomatic during at least one AF episode.

Cost-effectiveness of dual-chamber pacing compared with ventricular pacing for sinus node dysfunction

BACKGROUND

Compared with single-chamber ventricular pacing, dual-chamber pacing can reduce adverse events and, as a result, improve quality of life in patients paced for sick sinus syndrome. It is not clear, however, how these benefits compare with the increased cost of dual-chamber pacemakers.

METHODS AND RESULTS

We used 4-year data from a 2010-patient, randomized trial to estimate the incremental cost-effectiveness of dual-chamber pacing compared with ventricular pacing and then projected these findings over the patients' lifetimes by using a Markov model that was calibrated to the first 5 years of in-trial data. To assess the stability of the findings, we performed 1000 bootstrap analyses and multiple sensitivity analyses. During the first 4 years of the trial, dual-chamber pacemakers increased quality-adjusted life expectancy by 0.013 year per subject at an incremental cost-effectiveness ratio of 53,000 dollars per quality-adjusted year of life gained. Over a lifetime, dual-chamber pacing was projected to increase quality-adjusted life expectancy by 0.14 year with an incremental cost-effectiveness ratio of approximately 6800 dollars per quality-adjusted year of life gained. In bootstrap analyses, dual-chamber pacing was cost-effective in 91.9% of simulations at a threshold of 50,000 dollars per quality-adjusted year of life and in 93.2% of simulations at a threshold of 100,000 dollars. Its cost-effectiveness ratio was also below this threshold in numerous sensitivity analyses that varied key estimates.

CONCLUSIONS

For patients with sick sinus syndrome requiring pacing, dual-chamber pacing increases quality-adjusted life expectancy at a cost that is generally considered acceptable.

Specificity of Atrial Mode Switching in Detecting Atrial Fibrillation Episodes:. Roles of Length and Contiguity

The number of automatic mode switch (AMS) has been used to measure the efficacy of atrial pacing in limiting atrial fibrillation (AF). We investigated the impact of length and contiguity on the specificity of AMS in detecting AF episodes in 24 recipients of dual chamber pacemakers with sick sinus syndrome and paroxysmal AF. An AMS algorithm and intracardiac electrogram recordings (IEGM) were activated in all patients to distinguish true arrhythmic events from unnecessary AMS. The length of AMS and the contiguity, that is, the probability of occurrence of another AMS within 5 minutes before or after AMS were examined to increase the specificity of the AMS. During a mean follow-up of 5 +/- 3 months, 250 AMS were collected. The IEGM analysis confirmed a true AF episode in 193 of 250 AMS (77.2%). Using the contiguity criterion, 47 of 57 (82.5%) inappropriate AMS episodes were isolated (there were no other AMS within 5 minutes), whereas 54 of 193 (27.9%) appropriate AMS episode were isolated. Adopting both length and contiguity criteria the specificity of AMS in detecting true AF episodes increased from 77.2% to 93.2% at the cost of 11.9% loss of original sensitivity. Combining the length and contiguity criteria, we were able to improve the specificity of the AMS in the detection of AF.

Temporal variability of atrial tachyarrhythmia burden in bradycardia–tachycardia syndrome patients

AIMS

Several studies have tested non-pharmacological therapies for atrial tachyarrhythmias (ATs) by measuring the cumulative time (burden) the patient spends in arrhythmia. Contradictory results questioned either therapy efficacy or statistical power of the trials. We studied AT burden variability in patients paced for sinus node disease (SND) in order to interpret currently published data appropriately and to evaluate reliable sample sizes.

METHODS AND RESULTS

One hundred and five patients with AT and SND received a dual chamber pacemaker with antitachyarrhythmia-pacing capability, and were followed for 13 months. Seventy-eight patients (74%) suffered AT recurrences. Device-gathered diagnostic measures were used to simulate results of randomized studies both with crossover and parallel design. The sample size required for statistically significant results was calculated as a function of the expected therapy-induced burden reduction. AT burden intra-patient variability was high: 43% of patients showed intrinsic fluctuations hiding any therapy-induced burden reduction lower than 30%. Demonstrating therapeutic breakthrough through a 6 month study would require 290 patients with crossover design and 5800 patients with parallel design. Doubling the study period requires 400 and 3000 patients, respectively.

CONCLUSION

Patients with AT and paced for SND showed high intra-patient burden variability, which could possibly hide an AT burden reduction induced by a therapy. Previous studies involving non-pharmacological therapies utilizing AT burden endpoints could lack the power to reach statistical significance.

Permanent Pacemakers and Implantable Defibrillators

Pacemakers and cardioverter-defibrillators are implanted in patients with cardiovascular disease for an ever-increasing array of indications. Intensivists provide care frequently for patients who have these devices, and thus, they must be familiar with common problems and nuances that may contribute to critical illness. Close collaboration of the critical care physician and cardiologist/electrophysiologist assures that pacemakers and defibrillators are tuned to optimize the hemodynamic milieu of critically ill patients. Many recent advances in the sophistication of implanted devices are reviewed herein.

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.

Atrial fibrillation after radiofrequency ablation of atrial flutter: preventive effect of angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, and diuretics

OBJECTIVES

To determine risk factors for the development of atrial fibrillation (AF) after atrial flutter (AFL) ablation; and to study the relation between AF development and periprocedural drug use.

METHODS

AFL ablation was performed in 196 patients. The relation between AF occurrence and clinical, echocardiographic, and procedural factors and periprocedural drug use was analysed retrospectively by a Cox proportional hazard method.

RESULTS

After a median follow up of 2.2 years, 114 patients (58%) developed at least one AF episode. Factors associated with AF development were the presence of preprocedural AF, a history of cardioversion, and the number of antiarrhythmic drugs used before the procedure. Use of angiotensin converting enzyme (ACE) inhibitors/angiotensin II receptor blockers and diuretics was significantly associated by univariate and multivariate analyses with less development of AF.

CONCLUSIONS

A high proportion of patients develop AF after AFL ablation. The incidence of AF is related to pre-ablation AF and its persistence. ACE inhibitors/angiotensin II receptor blockers and diuretics seem to protect against AF.

Pacemaker Diagnostics to Determine Treatment and Outcome in Sick Sinus Syndrome with Paroxysmal Atrial Fibrillation

Sequential analysis of pacemaker diagnostics has been used to help manage the treatment and pacemaker program in patients who have sick sinus syndrome with documented paroxysmal atrial fibrillation. One hundred consecutive patients were followed for an average of 18 months. Knowledge of the atrial fibrillation burden led to major changes in medical management for half of the patients and changes to pacemaker programming for all. At the end of the study, 48 patients were free of arrhythmia with pacing although 14 required antiarrhythmic medication. We advocate using pacemaker diagnostics to improve patient management.

Accuracy of Mode Switch Algorithms for Detection of Atrial Tachyarrhythmias

INTRODUCTION

In patients with permanent pacemakers, mode switching events often are interpreted as surrogate markers for atrial tachyarrhythmias. The aim of this study was to determine the accuracy of automatic mode switching algorithms in patients with permanent pacemakers for the diagnosis of atrial tachyarrhythmias.

METHODS AND RESULTS

Forty patients with tachycardia-bradycardia syndrome and Medtronic Thera or Kappa 700 permanent pacemakers underwent Holter monitoring. Date, time of onset, and duration of each mode switch episode as recorded by the pacemaker and each atrial tachyarrhythmia episode as recorded by the Holter monitor were compared. Sixteen patients had a total of 54 atrial tachyarrhythmias documented on Holter monitoring (47 atrial fibrillation, 7 atrial flutter). Comparison of Holter data with pacemaker interrogation demonstrated that 53 (98.1%) of 54 atrial tachyarrhythmia episodes resulted in mode switching with one 13-second episode of mode switching during sinus rhythm. The sensitivity and specificity of mode switching for the duration of atrial tachyarrhythmias were 98.1% and 100%, respectively. The algorithms detected 98.9% of the total duration of atrial fibrillation and 96.4% of the total duration of atrial flutter.

CONCLUSION

In patients with tachycardia-bradycardia syndrome and permanent pacemakers having these mode switching algorithms, mode switching events are reliable surrogate markers for atrial tachyarrhythmias. Therefore, mode switching may serve as a valuable tool for clinical decision making and further research into the natural history and burden of atrial tachyarrhythmias.

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.

Prospective Randomized Study of Mode Switching in a Clinical Trial of Pacemaker Therapy for Sinus Node Dysfunction

INTRODUCTION

Atrial fibrillation (AF) is common in pacemaker patients with sinus node dysfunction (SND) and may result in rapid ventricular pacing (RVP) in the DDDR mode. Mode switching (MS) reduces RVP, but its clinical benefit in patients with SND is unknown.

METHODS AND RESULTS

Two hundred two patients in the Mode Selection Trial (MOST; 2,010-patient, 6-year trial of DDDR vs VVIR pacing in SND) randomized to DDDR pacemakers with atrial high-rate episode (AHRE) storage capabilities were subrandomized to MS ON (N = 96) or MS OFF (N = 106). Cardiovascular symptoms, quality of life (QOL), reprogramming due to RVP, death, stroke, and heart failure hospitalization (HFH) were compared between groups. The treatment groups were similar with regard to AF history (59% MS ON vs 57% MS OFF). AHREs occurred in 49% patients during median follow-up of 2.2 years. Median AHRE duration (in min; MS ON 116 vs MS OFF 58, P = 0.29), frequency AHREs/week (MS ON 3.5 vs MS OFF 6.4, P = 0.23), and time spent in AHRE (min/week) (MS ON 450, MS OFF 268) were similar. Reprogramming due to any RVP during AHREs occurred more in MS OFF vs MS ON (13.2% vs 3.1%, P = 0.011) and marginally more for symptomatic RVP (8.5% vs 2.1%, P = 0.062). Cardiovascular symptoms occurred in 93.6% MS ON vs 90.2% MS OFF (P = 0.38). Median number of symptoms reported per visit was similar (MS ON 1.3 vs MS OFF 1.5, P = 0.62). Median symptom frequency/severity, summed and averaged over visits, was similar (MS ON 4.3 vs MS OFF 4.5, P = 0.74). QOL was not different between groups. Death, stroke, and HFH were not different between groups.

CONCLUSION

MS reduces pacemaker reprogramming due to RVP during AHREs in a small number of patients but does not improve QOL or cardiovascular symptoms overall among patients with SND.

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.