The use of atrial overdrive and ventricular rate stabilization pacing algorithms for the prevention and treatment of paroxysmal atrial fibrillation: the Pacemaker Atrial Fibrillation Suppression (PAFS) study.

AIMS: The PAFS study is a randomized, multicentre investigation of the effects of third generation anti-atrial fibrillation pacemaker algorithms in patients with paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS: 182 patients (72 +/- 9 years, 55% male) with at least three symptomatic episodes of PAF within prior 3 months resistant to two anti-arrhythmics were enrolled. A pacemaker-derived atrial fibrillation (AF) burden of 1-50% was required in the initial induction phase. Seventy-nine patients fulfilled these criteria and were randomized to four, month-long phases in a crossover design. Algorithm phases were 'rate soothing' on, 'ventricular rate stabilization' on, and 'All on', which included these two algorithms plus post-AF response. The algorithm phases were compared to 'All off' dual chamber universal mode (DDD 60) for the analysis. Forty-two percent of patients enrolled in the monitoring phase had no AF. The percentage of AF induced by premature atrial contractions (PACs) was significantly reduced by rate soothing from 25 to 17% (P < 0.05). There was no significant change in AF burden, AF episode number, quality of life, or symptoms with any algorithm (P = ns). CONCLUSION: The rate-soothing algorithm by atrial overdrive pacing reduced PAC-initiated PAF. However, there was no overall change in AF burden, PAF episodes, patient symptoms, or quality of life. Forty-two percent of PAF patients did not show any AF after enrollment, suggesting that bradycardia pacing alone eliminates AF.     

特殊心房起搏程序预防和治疗阵发性心房颤动的临床效果

目的评价特殊心房起搏程序预防和治疗阵发性心房颤动(PAF)的临床效果。方法12例病窦综合征合并PAF患者植入Vitatron Selection 900E(AF2.0、DDDR)型双腔起搏器,比较患者术后不同阶段PAF的发作总数、持续时间、AF负荷和心房起搏比率。结果除1例外,其余11例术后第2个月和第6个月(起搏预防阶段)比术后第1个月(监测阶段)的PAF事件数[80(25;215),57(12;102)vs 203(86;425)],房颤总持续时间[1.9 d(0.6d;5.3 d),1.5 d(0.3 d;6.1 d)vs 2.9 d(0.8 d;9.8 d)],AF负荷[6.3%(2.0%;17.7%),5.0%(1.0%;20.6%)vs 9.6%(2.7%;32.8%)]均减低(P均<0.05),心房起搏比率增加[60%(40%;80%),54%(42%;84%)vs46%(26%;54%),P<0.05]。结论预防性心房起搏程序可以减少PAF事件的发生,降低AF负荷,改善患者的症状,具有短期的疗效。     

Pacemaker prevention therapies for the control of drug-refractory paroxysmal atrial fibrillation.

AIMS: Atrial septal pacing has been shown to prevent paroxysmal atrial fibrillation (PAF) refractory to drugs in patients without inappropriate bradycardia. This study assesses the effects of atrial septal pacing using new pacing algorithms designed to prevent the initiation or maintenance of PAF. METHODS AND RESULTS: Eleven Medtronic AT500 and 6 Guidant Pulsar Max pacemakers were implanted. The incremental benefit of prevention pacing therapies was compared with DDDR pacing by analysis of pacemaker-stored electrograms, ambulatory electrocardiography, symptoms and quality of life questionnaires. RESULTS: Atrial septal pacing reduced AF burden by >50% in 13/17 patients (76.5%). Activation of a combined pacing algorithm (atrial pacing preference; atrial rate stabilization; and post mode-switch overdrive pacing) in patients with AT500 pacemakers produced a marginal reduction in AF burden (mean %AF 0.61 ON, 0.73 OFF, P=0.53 ns). Conversely in the Pulsar Max group when atrial pacing preference was activated, AF burden was slightly increased (mean %AF 5.84 ON, 3.73 OFF,P =0.13). Symptoms improved with atrial septal pacing but did not change when prevention algorithms were activated. CONCLUSION: Atrial septal pacing resulted in a marked improvement in AF burden and symptoms. Activation of specific prevention pacing algorithms provided more continuous atrial pacing but had limited and heterogeneous effects on AF burden.     

Right atrial overdrive pacing for prevention of symptomatic refractory atrial fibrillation.

AIMS: Our aim was to investigate whether right atrial overdrive pacing is effective for the prevention of atrial fibrillation (AF) in patients without bradyarrhythmias. METHODS AND RESULTS: Patients with symptomatic paroxysmal or persistent AF refractory to at least two Class I or III antiarrhythmic drugs and without bradyarrhythmias were included. Successful therapy was defined as the combination of (a) a reduction of AF burden with or without AAD use >75%, (b) total AF burden < or =5% per year, and (c) less than one electrical cardioversion per year. Lower rate was set at 70 b.p.m. Additional AF prevention and termination features were used in case of no success.After a median follow-up of 18 (10-55) months, therapy was effective in 19 of the 36 included patients (53%). In 74% of the successfully treated patients, additional antiarrhythmic drugs were used. In successfully treated patients, the AF burden was reduced from 15% (5-100%) to 0% (0-4%). Multivariate analysis showed that the concomitant use of a Class I or III antiarrhythmic drug, a lower AF burden before implantation and the use of an angiotensin converting enzyme inhibitor were predictors of successful therapy. CONCLUSION: Right atrial overdrive pacing in combination with antiarrhythmic drugs seems an attractive treatment option in drug refractory symptomatic AF patients.     

Prevention of paroxysmal atrial fibrillation in patients with sinus bradycardia: role of right atrial linear ablation and pacing site

INTRODUCTION: Right atrial linear lesions (RALL), either alone or in combination with antiarrhythmic drug therapy, may modify the substrate for maintenance of atrial fibrillation (AF). The aim of this prospective randomized study was to determine whether RALL provides additional benefit to right atrial appendage pacing (RAAP) and/or interatrial septum pacing (IASP) and drug therapy in patients with symptomatic paroxysmal AF and sinus bradycardia requiring permanent atrial pacing. METHODS AND RESULTS: Sixty-four patients (33 men and 31 women, mean age 73 +/- 10 years) completed the 6-month follow-up. Patients were randomized to either RALL (n = 33) or non-right atrial linear lesions (NRALL), and then to either IASP (n = 32) or RAAP (n = 32). Fifteen RALL patients were paced at the IAS and 18 at the RAA. Seventeen NRALL patients were paced at the IAS and 14 at the RAA. No statistical difference was observed with regard to the mean atrial tachyarrhythmia (AT) burden between NRALL (84 +/- 169 min/day) and RALL patients (202 +/- 219 min/day). Mean AT burden was significantly lower in the IASP group (70 +/- 150 min/day) than in RAAP group (219 +/- 317 min/day; P < 0.016). In the RALL group, the mean AT burden was 99 +/- 180 min/day in the IASP patients and 288 +/- 372 min/day in the RAAP patients (P < 0.046). In the NRALL group, no statistical difference in the mean AT burden was observed between IASP patients (46 +/- 117 min/day) and RAAP patients (130 +/- 211 min/day). CONCLUSION: The results of the present study indicate that RALL did not provide any additional therapeutic benefit to combined antiarrhythmic drug therapy and septal or nonseptal atrial pacing in patients with sinus bradycardia and paroxysmal AF.     

What is the real atrial fibrillation burden after catheter ablation of atrial fibrillation? A prospective rhythm analysis in pacemaker patients with continuous atrial monitoring.

AIMS: Rhythm follow-up after catheter ablation of atrial fibrillation (AF ablation) is mainly based on Holter electrocardiogramm (ECG), tele-ECG or on patients symptoms. However, studies using 7-day Holter or tele-ECG follow-up revealed a significant number of asymptomatic recurrences. Thus, the aim of this study was to analyse continuous atrial recordings in pacemaker patients with an incorporated Holter function before and after AF ablation in order to determine all AF recurrences and thereby the 'real' success rates. METHODS AND RESULTS: The study comprised 37 patients (64.6 +/- 10 years) with prior pacemaker/implantable cardioverter defibrillator (ICD) implantation including an atrial Holter function referred for AF ablation. Holter data were obtained and correlated to patients' symptoms before and every 3-month after AF ablation. AF recurrence was defined as an atrial high frequency episode of less than 330 ms (180 b.p.m.) lasting longer than 30 s. The ablation procedure consisted of pulmonary vein isolation (PVI) in patients with paroxysmal atrial fibrillation (PAF, n = 20) and additional substrate modification aiming arrhythmia termination in patients with persistent or inducible AF after PVI as well as in patients with a history of long-lasting persistent AF (PersAF, n = 17). The mean atrial Holter monitoring period was 7.4 +/- 3.3 months before and 13.5 +/- 4.2 months after ablation with an overall AF burden of 33.7% prior to ablation. During follow-up, AF burden decreased from 17.3-0.65% (P = 0.001) in PAF patients and from 57.4 to 13.9% (P = 0.024) in patients with PersAF. Complete AF freedom was observed in 85% (17 patients) of PAF patients and 59% (10 patients) in patients with PersAF. The absence of symptoms correlated well with documented freedom of AF. CONCLUSION: In the present study we could show, that freedom from AF can be achieved by catheter ablation in a high percentage of patients even with PersAF. Continuous atrial monitoring reveals AF ablation success rates comparable with those assessed by clinical evaluation. Symptomatic freedom of AF correlated well with the actual freedom of AF at least in this highly symptomatic patient cohort.     

抗心房颤动起搏器和普通DDD起搏器治疗阵发性心房颤动的疗效对比

目的对比抗心房颤动(简称房颤)起搏器和普通DDD起搏器治疗阵发房颤的疗效。方法阵发房颤患者19例置入Vitatron型或ST.JudeAFX抗房颤起搏器,21例置入普通DDD起搏器。结果两组生活质量评分提高分别达35分(P<0.05)和43分(P<0.05),显效率分别为47.4%和14.3%(P<0.05)、有效率分别为73.7%和23.8%(P<0.05)。900E患者房颤负荷降低58.57%(P<0.05)。结论抗房颤起搏器治疗阵发房颤优于普通DDD起搏器,似可作为传统治疗方法的重要补充。     

Bifocal versus unifocal right atrial pacing under plasma level controlled sotalol to prevent atrial fibrillation in patients with symptomatic sinus bradycardia and paroxysmal atrial fibrillation

AIMS : Bifocal right atrial pacing (BP) has been reported to increase arrhythmia-free intervals in patients with paroxysmal atrial fibrillation (PAF) under antiarrhythmic drugs. This study compares AF burden with unifocal pacing (UP) vs BP under sotalol. METHODS : In 19 patients with PAF a DDDR pacemaker with right atrial lateral and CS ostial leads was implanted. Sotalol was initiated. After a 3 month back-up pacing period patients were randomized to continuous UP or BP for 3 months and crossed over for 3 more months. Primary endpoint was AF burden. Secondary endpoints included number of episodes, time to first recurrence and safety of BP. RESULTS : The intention to treat analysis revealed 12.4% AF during back-up, 6.2% during UP and BP (p=0.91 UP vs BP, p=0.08 back-up vs UP and p=0.07 back-up vs BP). Per protocol analysis showed no advantage of either pacing mode (UP 4.8% and BP 5.4% AF, p=0.64). Overdrive pacing reduced AF burden to 6.2 vs 8.8% during back-up (p=0.09). Septal lead dislodgement occurred in 3 patients. CONCLUSION : Atrial pacing tends to reduce AF burden in patients with PAF under sotalol. An incremental effect of BP vs UP cannot be confirmed. BP may be complicated by elevated lead dislodgement rates.     

Paroxysmal atrial fibrillation prevention by pacing in patients with pacemaker indication.

AIMS: The prevent-atrial fibrillation (AF) registry analyses the clinical relevance and usefulness of the four preventive pacing algorithms, available in a family of cardiac stimulators, to prevent atrial fibrillation. METHODS AND RESULTS: This study is a prospective, non-randomized, multicentre registry. Patients are eligible for the registry if they have sick sinus syndrome (SSS) with or without pre-existing atrial fibrillation. The preventive pacing algorithms were programmed for each patient on an individual basis using the diagnostic features of the devices. In the period from April 2000 to April 2001 a total of 68 patients (33 male, 35 female) has been included in the registry in 14 hospitals in Spain. Mean age was 72+/-12 years and the pacemaker indication was SSS in 15 patients (22%) and SSS with paroxysmal AF in 53 patients (78%). The median AF burden for the total group (n=32) was significantly reduced from 3.9 to 1.3% (67%, P=0.034, Wilcoxon signed rank test). The decrease in AF burden was accompanied by a non-significant decrease in the median number of episodes per day from 1.47 to 0.64 (a decrease of 56%). The average atrial pacing % was increased from 72 to 78%. CONCLUSIONS: The prevent-AF registry demonstrated the usefulness of four preventive pacing algorithms in daily clinical practice. During the registry a significant reduction in AF burden and all other endpoints was observed. Dedicated diagnostics were key to adapting the optimal pacing therapy during follow-up.     

Atrial arrhythmia suppression by atrial overdrive pacing: pacemaker Holter assessment.

The purpose of this study was to assess the efficacy of overdrive, single-site right atrial appendage pacing to reduce the burden of atrial fibrillation (AF) when compared with a standard lower rate limit of 60 bpm. This was verified by using the pacemaker's Holter. Eighteen subjects with a pre-implant history of paroxysmal AF and implanted DDDR mode-switching pacemakers were recruited. The pacemaker lower rate limit was programmed in random order to 60, 75 or 90 bpm for three 2-month periods and the amount of AF quantified. In addition, the exercise tolerance (ET), general well being (GWB), functional capacity (FC) and specific symptom prevalence (SSP) were assessed. The main finding of the study was that when ranked according to the amount of AF, there was no significant difference in the amount of AF according to the pacing rate. Six patients failed to tolerate pacing at 90 bpm. There were no differences in the ET, GWB, FC and SSP scores. It is concluded that those clinicians that manage patients with paroxysmal     

Septal atrial pacing for the prevention of atrial fibrillation.

AIMS: Atrial fibrillation (AF) produces significant morbidity and mortality. The current method of permanent pacing of the right atrium (RA) may cause delayed interatrial conduction and predispose to AF. We hypothesized that atrial septal pacing would reduce AF compared with high RA pacing. METHODS AND RESULTS: The patients were randomized into two groups. After randomization, patients received a dual-chamber rate-responsive device capable of mode-switching with advanced telemetry features. Devices were programmed in a standardized manner. To be eligible, the patients were required to have a conventional indication for a permanent pacemaker and recurrent paroxysmal AF. Group 1 was paced from high RA and Group 2 was paced from the atrial septum. Analysis of 43 patients who have completed 6 months of follow-up and 22 patients who completed 12 months of follow-up showed no significant differences in the number of mode-switching episodes or in AF burden between groups (P = NS by Mann-Whitney) although there was a trend for less AF with septal pacing. There were no differences in thresholds, sensing, or lead impedance. Lead parameters remained stable over time and there were no displacements of the electrodes after implantation. No patient experienced lead-related complications. A significant variability in AF burden was noted in this patient population. CONCLUSIONS: Implantation of an atrial-active fixation lead on the atrial septum is safe and feasible. However, this study showed no significant difference between septal pacing and high atrial pacing, using the endpoints of AF duration and number of AF episodes.     

Conventional and dedicated atrial overdrive pacing for the prevention of paroxysmal atrial fibrillation: the AFTherapy study.

AIMS: This investigation was conducted to determine the effectiveness of several conventional overdrive pacing modalities (single rate and rate responsive pacing at various lower rates) and of four dedicated preventive pacing algorithms in the suppression of paroxysmal atrial fibrillation (AF). METHOD AND RESULTS: In this multi-centre, randomized trial, 372 patients with drug-refractory paroxysmal AF were enrolled. Patients received a dual-chamber pacing device capable of delivering conventional pacing therapy as well as dedicated AF prevention pacing therapies and to record detailed AF-related diagnostics. The primary endpoint was AF burden, whereas secondary endpoints were time to first AF episode and averaged sinus rhythm duration. During a conventional pacing phase, patients were randomized to single rate or rate-responsive pacing with lower rates of either 70 or 85 min(-1) or to a control group with single rate pacing at 40 min(-1). In the subsequent preventive pacing phase, patients underwent pacing at a lower rate of 70 min(-1) with or without concomitant application of four preventive pacing algorithms. A substantial amount of data was excluded from the analysis because of atrial-sensing artefacts, identified in the device-captured diagnostics. In the conventional pacing phase, no significant differences were found between various lower rates and the control group receiving single rate pacing at 40 min(-1) or between single rate and rate-responsive pacing. Patients receiving preventive pacing with all four therapies enabled had a similar AF burden compared with patients treated with conventional pacing at 70 min(-1) (P = 0.47). CONCLUSIONS: The results do not demonstrate a significant effect of conventional atrial overdrive pacing or preventive pacing therapies. However, the observations provided important information for further consideration with respect to the design and conduct of future studies on the effect of atrial pacing therapies for the reduction of AF.     

Effect of atrial overdrive pacing on pulmonary vein focal discharge in patients with atrial fibrillation.

AIMS: Recently, it has been shown that atrial fibrillation may be caused by spontaneously discharging foci located predominantly in the pulmonary veins. However, the effect of atrial overdrive pacing on these pulmonary vein foci has not been studied. METHODS AND RESULTS: In 58 patients with drug refractory paroxysmal or persistent atrial fibrillation we performed radiofrequency catheter ablation of arrhythmogenic triggers inside the pulmonary veins and/or an ostial pulmonary vein isolation with conventional mapping and ablation technology. Continuous bigeminal pattern of discharge from one or more arrhythmogenic pulmonary veins was recorded in 14 patients. Atrial overdrive pacing resulted in suppression of pulmonary vein 'focus' activity in all patients. The longest mean atrial pacing cycle length resulting in overdrive suppression was 587+/-114 ms. Independent of pacing rate and duration, bigeminal pulmonary vein focus activity reemerged 2.5+/-3.7s after cessation of pacing. Overdrive suppression of the pulmonary vein focus was incomplete in 9 pacing attempts, and resulted in induction of atrial fibrillation from the same vein in 3 of 31 pacing manoeuvres. At 2 years follow-up 79% of these patients were free of atrial fibrillation, 55% without antiarrhythmic drugs, 24% on previously ineffective antiarrhythmic drug therapy. CONCLUSION: Stable pulmonary vein 'focus' activity in patients with atrial fibrillation can be suppressed by atrial overdrive pacing. However, 'proarrhythmic' effects of atrial overdrive pacing, such as induction of atrial fibrillation, were also seen.     

Right atrial preventive and antitachycardia pacing for prevention of paroxysmal atrial fibrillation in patients without bradycardia: a randomized study.

AIMS: To investigate the efficacy of preventive and antitachycardia pacing (ATP) in patients with symptomatic paroxysmal atrial fibrillation (AF) without bradyarrhythmias. METHODS AND RESULTS: In this randomized cross-over pilot study, we randomized 38 symptomatic paroxysmal AF patients 'without' bradyarrhythmias to atrial pacing lower rate 70 ppm and prevention and ATP therapies ON or to atrial pacing lower rate 34 ppm and prevention and ATP therapies OFF during 12 weeks with a 4 week washout period in between. The atrial lead was preferably placed in the inter-atrial septum. Antiarrhythmic drugs were continued during the study. Primary endpoint was AF burden. Mean age was 62 +/- 9 years and 27 (71%) patients had lone AF. Septal lead placement was accomplished in 26 (68%) patients. During the treatment ON, there was a trend for AF burden reduction [from median 3.3% (1.0-15.2) to 2.4% (0.2-12.2), P = 0.06, reduction 27%]. If septal lead placement was accomplished, AF burden reduction was statistically significant [44% reduction, from median 2.5% (1.0-8.0) to 1.4% (0.2-8.4), P = 0.03]. Quality of life and symptoms did not change, also not in the septal group. CONCLUSION: A hybrid therapy of preventive and ATP pacing and antiarrhythmic drugs may significantly reduce but not abolish AF burden if septal pacing is realized.     

A Prospective Randomized Study to Assess the Efficacy of Rate and Site of Atrial Pacing on Long-Term Development of Atrial Fibrillation

The Septal Pacing for Atrial Fibrillation Suppression Evaluation (SAFE) study is a single-blinded, parallel randomized designed multicenter study in pacemaker indicated patients with paroxysmal atrial fibrillation (AF). The objective is to evaluate whether the site of atrial pacing–-conventional right atrial appendage versus low atrial septal—with or without atrial overdrive pacing will influence the development of persistent AF. The study will provide a definitive answer to whether a different atrial pacing site or the use of AF suppression pacing or both can give incremental antiarrhythmic benefit when one is implanting a device for a patient with a history of paroxysmal AF.     

Temporary atrial epicardial pacing as prophylaxis against atrial fibrillation after heart surgery: a meta-analysis

INTRODUCTION: Recent studies have reported the use of temporary epicardial atrial pacing as prophylaxis for postoperative atrial fibrillation (AF). The aim of this study was to assess the effect of pacing therapies for prevention of postoperative AF using meta-analysis. METHODS AND RESULTS: Using a computerized MEDLINE search, eight pacing prophylaxis trials with 776 patients were included in the meta-analysis. Trials compared control patients to patients randomized to right atrial, left atrial, or biatrial pacing used in conjunction with either fixed high-rate pacing or overdrive pacing. Overdrive biatrial pacing (OR 2.6, CI 1.4-4.8), overdrive right atrial pacing (OR 1.8, CI 1.1-2.7), and fixed high-rate biatrial pacing (OR 2.5, CI 1.3-5.1) demonstrated a significant antiarrhythmic effect for prevention of AF after open heart surgery. Furthermore, studies investigating overdrive left atrial pacing and fixed high-rate right atrial pacing have been underpowered to assess efficacy. CONCLUSION: Biatrial overdrive and fixed high-rate pacing and right atrial fixed high-rate pacing reduced the risk of new-onset AF after open heart surgery, and the relative risk reduction is approximately 2.5-fold. These results imply that various pacing algorithms are useful as a nonpharmacologic method to prevent postoperative AF.     

缬沙坦对病窦综合征双腔起搏术后阵发性心房颤动的影响

目的评价缬沙坦对病窦综合征(SSS)双腔起搏后阵发性心房颤动(AF)的作用。方法双腔起搏器植入术的患者,术后随访时选出有阵发性AF者81例,将其随机分为治疗组(n=41)和对照组(n=40)。在治疗基础疾病的基础上,治疗组给予缬沙坦80 mg,每晚顿服,对照组不予血管紧张素Ⅱ受体阻滞剂类药物治疗。随访1年,观察AF发作次数、AF负荷及左房内径。结果治疗组起搏术后1年AF发作次数、AF负荷、左房内径明显低于对照组(4.2±1.9次/天vs 9.5±3.4次/天,0.395±0.285 h/d vs 0.860±0.316 h/d,35.9±2.7 mm vs 40.7±3.8mm,P均<0.05),亦低于用药前(P<0.01),而对照组上述指标无变化。结论缬沙坦可有效抑制SSS双腔起搏后阵发性AF的发生。     

Atrial pacing periablation for prevention of paroxysmal atrial fibrillation.

BACKGROUND: This study tested the hypothesis that rate-adaptive atrial pacing would prevent paroxysmal atrial fibrillation (PAF) in patients with frequent PAF in the absence of symptomatic bradycardia. METHODS AND RESULTS: Patients (n=97) with antiarrhythmic drug-refractory PAF received a Medtronic Thera DR pacemaker 3 months before planned AV node ablation. Patients were randomized to no pacing (n=48) or to atrial rate-adaptive pacing (n=49). After a 2-week stabilization period, patients were followed up for an additional 10 weeks. The time to first recurrence of sustained PAF, the interval between successive episodes of PAF, and the frequency of PAF were compared between the 2 groups in intention-to-treat analysis. Time to first episode of sustained PAF was similar in the no-pacing (4.2 days; 95% CI, 1.8 to 9.5) and the atrial-pacing (1.9 days; 95% CI, 0.8 to 4.6; P=NS) groups. PAF burden was lower in the no-pacing (0.24 h/d; 95% CI, 0.10 to 0.56) than in the atrial-pacing (0.67 h/d; 95% CI, 0.30 to 1.52; P=0.08) group. Paired crossover analysis in 11 patients revealed that time to first PAF was shorter during atrial pacing (1.6 days; 95% CI, 0.6 to 4.9) than with no pacing (6.0 days; 95% CI, 2.4 to 15.0; P=0.13), and PAF burden was greater during atrial pacing (1.00 h/d; 95% CI, 0.35 to 2.91) than with no pacing (0.32 h/d; 95% CI, 0.09 to 1.13; P<0.016). CONCLUSIONS: Atrial rate-adaptive pacing does not prevent PAF over the short term in patients with antiarrhythmic drug-resistant PAF without symptomatic bradycardia.     

Clinical assessment of antiarrhythmic agents for paroxysmal atrial fibrillation guided by modification of electrophysiologic arrhythmogenicity

INTRODUCTION: Rapid atrial pacing alters atrial electrophysiology, promoting initiation and maintenance of atrial fibrillation (AF). The aim of this study was to assess differences in the electrophysiologic properties of atrial tissue between patients with and without AF episodes and to determine whether electrophysiologic properties can predict the clinical efficacy of antiarrhythmic agents. METHODS AND RESULTS: Sixty patients were studied, 33 with documented episodes of paroxysmal atrial fibrillation (PAF) and 27 control patients. Atrial effective refractory period (AERP), atrial vulnerability, and intra-atrial conduction time were measured at baseline and after rapid constant atrial pacing for 5 minutes at rates of 130, 150, 170, and 190 beats/min. The clinical efficacy of antiarrhythmic agents for PAF prophylaxis was assessed over 14 months with an antiarrhythmic agent identical to that administered intravenously, and the antiarrhythmic agent effects on AERP, atrial vulnerability, and intra-atrial conduction time were assessed. AERP shortening and atrial vulnerability increase were significantly larger in the PAF group. Antiarrhythmic agents that were clinically effective in suppressing PAF significantly attenuated AERP shortening, but antiarrhythmic agents that were clinically ineffective did not. CONCLUSION: Changes in AERP and atrial vulnerability observed after rapid atrial pacing are considered indicative of the electrophysiologic substrate of PAF. Attenuation of AERP and atrial vulnerability by antiarrhythmic agents might be useful in predicting their clinical efficacy.     

Verification of pacemaker automatic mode switching for the detection of atrial fibrillation and atrial tachycardia with Holter recording.

AIMS: Verification of the accuracy of onset, offset, and duration of automatic mode switching (AMS) of pacemakers compared with onset and end of atrial fibrillation (AF) or atrial tachycardia (AT). Correct pacemaker diagnosis of atrial tachyarrhythmias (AA) is indispensable for reliable automatic prevention and intervention algorithms of AA. METHODS AND RESULTS: Comparison was made of the AMS registration of the pacemaker-stored electrograms (EGMs) and the number and cumulative duration of these episodes with continuous 7-day Holter monitoring. Atrial sensitivity was kept at 0.5 mV and far field R-wave recognition in the atrial channel was excluded by blanking of this signal. Lead types were confined to leads with short-ring tip spacing (10-13.8 mm). During Holter monitoring, 18 of 57 included patients with standard reason for pacemaker implantation showed episodes of AF or AT. Cumulative duration of AF and AT from Holter was correctly interpreted by the pacemaker in 99.9% of the patients. All episodes of AF, as seen on the Holter recording, were recognized by the pacemaker (correlation 99.9%). During AF, multiple episodes of undersensing were detected. The number of AMS episodes was influenced by undersensing during AF. The influence of these short episodes of undersensing on the total duration of AF was trivial (cumulative duration of AF was 99.9% correct). In patients with AT without AF on Holter (n=7) and in contrast to the AF episodes, the cumulative AT duration did not correlate well (63%) with the Holter recordings. The number of AMS episodes in the setting of AT was influenced by the atrial tachycardia detection rate setting and the duration of the post-ventricular atrial blanking interval. CONCLUSION: The total duration of AF is correctly represented by the total duration of AMS and can be considered a reliable measure of total AF duration. AT duration was poorly correlated with AMS duration. The number of mode switches does not reflect the number of episodes of AF/AT. Increased memory capacity allowing the storing of all EGMs triggered by the initiation of AF/AT would be the ideal setting with which to optimize the diagnostic performance of pacemakers.