Antiarrhythmic benefits of dual chamber stimulation with rate-response in patients with paroxysmal atrial fibrillation and chronotropic incompetence: a prospective, multicentre study

Presence and duration of atrial fibrillation detected by continuous monitoring: crucial implications for the risk of thromboembolic events

INTRODUCTION

Asymptomatic atrial fibrillation (AF) can expose patients to the risk of stroke. The primary objective of this study was to assess the incidence of thromboembolic events in relationship with CHADS(2) (congestive heart failure, hypertension, age >or=75 years, diabetes mellitus, and prior stroke, or transient ischemic attack) score and AF presence/duration. The secondary objective was to compare intermittent versus continuous monitoring strategies.

METHODS AND RESULTS

Data from patients with an implanted pacemaker and a history of AF were analyzed. Thromboembolic risk was quantified through CHADS(2) score. Three AF groups were considered: patients with <5-minutes AF on 1 day (AF-free); patients with >5-minutes AF on 1 day but <24 hours (AF-5 minutes); patients with AF episodes >24 hours (AF-24 hours). Monitoring strategies involving 24-hour Holter, 1-week Holter, and 30-day Holter were simulated. Data from 568 patients continuously monitored for 1 year were analyzed: 171 (30%) had CHADS(2) score = 0; 269 (47%) had CHADS(2) score = 1; 111 (20%) had CHADS(2) score = 2; and 17 (3%) had CHADS(2) score >or= 3. During follow-up, 14 patients (2.5%) had an ischemic thromboembolic event. AF-24 hours patients numbered 223 (39.2%); AF-5 minutes, 179 (31.5%); and AF-free, 29.2%. By combining AF presence/duration with CHADS(2) score, two subpopulations with markedly different risks of events (0.8% vs 5%, P = 0.035) were identified, the former corresponding to AF-free with CHADS(2)<or=2, or AF-5 minutes with CHADS(2)<or=1, or AF-24 hours with CHADS(2)= 0. The mean sensitivity in detecting an AF episode lasting >5 minutes was 44.4%, 50.4%, and 65.1% for 24-hour Holter, 1-week Holter, and 1-month Holter monitoring, respectively.

CONCLUSION

In patients with recurrent AF episodes, risk stratification for thromboembolic events can be improved by combining CHADS(2) score with AF presence/duration.

Medium-term follow-up and modes of failure following epicardial pacemaker implantation in young children

AIMS

Young children suffering from congenital or post-operative AV-block require life-long pacemaker stimulation. Due to the anatomical prerequisites initially epicardial electrodes are implanted and the generator is placed in the upper abdominal wall. The following study investigated modes of failure leading to reoperation in this group of technically challenging patients.

METHODS AND RESULTS

Between October 2000 and May 2005, a total of 21 infants (age 3 days to 5 years) underwent pacemaker implantation using a subxyphoidal incision for newborns (and a partial lower or complete median sternotomy for older children). Nine patients had previous cardiac surgery for complex congenital defects. The remaining 12 young children suffered from congenital AV-Block (CAVB). Twenty-one bipolar epicardial electrodes (Medtronic Capsure epi) were fixed to the right ventricle, 15 had additional implantation of a bipolar atrial lead. The pacemaker generator (Medtronic Kappa 701) was implanted into the right upper abdominal wall. Indications for revision were recorded. No mortality was observed; pacing and sensing parameters remained stable up to a 5-year follow-up. A total of four reoperations occurred. Three of the four revisions were caused by ventricular electrode fracture. At revision, two electrodes were broken at the crossing between the pericardial cavity and the abdominal wall, one bipolar lead at the Y-division into the two tip electrodes. One reoperation was due to a pacemaker recall. All revisions were performed without complications.

CONCLUSION

In our institute epicardial pacing in young children was associated with a satisfactory clinical outcome, but also a significant number of failures leading to reoperation, mainly due to electrode fracture caused by the muscular activity of this patient group. Reoperations were performed at a low risk.

Cardiac pacing for bradycardia support: Evidence-based approach to pacemaker selection and programming

The vast majority of pacemakers implanted in the United States for the treatment of symptomatic bradycardia are dual-chamber systems with a complex array of functions, such as rate responsiveness, dynamic atrioventricular delay, and automatic mode switching. Basic hemodynamic studies have convincingly demonstrated the superiority of maintaining atrioventricular synchrony. However, clinical trials have failed to demonstrate the impressive results expected based on physiologic data. The most recent randomized clinical trials have demonstrated that dual-chamber devices, when compared with single-chamber ventricular pacing, do not prevent mortality or stroke, and lead to an unexpectedly small reduction in heart failure hospitalizations. Although improvements in quality of life have not been consistently found when comparing ventricular-based versus atrial-based pacing, a reduction in the incidence of newly diagnosed atrial fibrillation in dual chamber-paced patients has been reported by most trials. Dual-chamber pacing has been reported to reduce pacemaker syndrome in US trials. The addition of rate modulation, in spite of attempting to replicate the normal response to exercise, has not shown a consistently positive impact on quality of life or treadmill time. The use of pacemakers for the treatment of vasovagal syncope is controversial. Adding dual-chamber sensing ability to current implanted defibrillators considerably reduces the number of inappropriate shocks but may increase mortality if not programmed to minimize ventricular stimulation.

Dual defibrillator improves quality of life and decreases hospitalizations in patients with drug refractory atrial fibrillation

AIM OF THE STUDY

to evaluate the impact of dual defibrillator implantation on quality of life and resource utilization in patients with drug refractory atrial fibrillation (AF) without prior ventricular arrhythmias.

METHODS

Forty patients (28 M, mean age 64 +/- 10) received a dual defibrillator Medtronic 7250. AF was persistent in 60% and paroxysmal in 40%.

RESULTS

The follow-up lasted 15 +/- 4 months (range 12-30). Eighty-five percent of patients had atrial tachyarrhythmia recurrences. Among 1366 treated episodes, overall success rate was 60.1% for antitachy pacing and 88.2% for atrial shock. Within one year after implant, arrhythmia related hospitalization number decreased from 1.5 +/- 2.0 to 0.4 +/- 0.8 ( p < 0.01) and 77% of patients were free from hospitalization. As regard to quality of life, Symptom Checklist/Frequency and Severity Scale improved after implant for all items and SF-36 questionnaire showed significant improvements in physical activities because of health problems and social activities. The patients assigned to early delivery of atrial shock after AF onset, when compared with the patients who did not accept atrial shock, showed a significant reduction of AF burden, a higher reduction of hospitalization number and a greater improvement of quality of life.

CONCLUSION

Dual defibrillator improved quality of life and decreased resource utilization in patients with drug refractory AF. Early delivering of atrial shock seems to be the most effective option.

Pacing to prevent atrial fibrillation

INTRODUCTION

Pacing has been proposed as a nonpharmacologic treatment option to prevent atrial tachyarrhythmias (ATs) in drug-refractory patients. This article reviews the current state of pacing to prevent ATs.

METHODS AND RESULTS

Different pacing modalities have been assessed with regard to their ability to prevent AT: conventional DDDR pacing with elevated lower rate limit, biatrial pacing, dual-site right atrial pacing, atrial septal pacing, and pacing with the use of dedicated pacing algorithms. Small studies suggest a benefit of conventional pacing for AT prevention in patients with bradycardia, but a randomized trial did not reveal any AT reduction by conventional pacing in patients without bradycardia. AT prevention by biatrial or dual-site right atrial pacing has been reported in small studies, but randomized trials did not show a clear benefit of these pacing techniques. Small studies showed a reduced AT recurrence rate in patients with septal pacing at the triangle of Koch or at Bachmann's bundle. Two large randomized trials with preventive pacing algorithms showed a significant AT reduction compared to conventional pacing, but this was not confirmed in four trials.

CONCLUSION

Pacing seems to be able to suppress ATs in a minority of patients; however, prospective identification of responders to different pacing modalities does not appear to be feasible at the present time.

Suppression of atrial tachyarrhythmias by pacing

INTRODUCTION

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

METHODS AND RESULTS

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

CONCLUSION

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

Impact of consistent atrial pacing algorithm on premature atrial complexe number and paroxysmal atrial fibrillation recurrences in brady-tachy syndrome: a randomized prospective cross over study

AIM OF THE STUDY

The Consistent Atrial Pacing (CAP) algorithm has been designed to achieve a high percentage of atrial pacing to suppress paroxysmal atrial fibrillation. The aim of our study was to compare the impact of DDDR+CAP versus DDDR pacing on paroxysmal atrial fibrillation recurrences and triggers in patients with Brady-Tachy Syndrome.

METHODS

61 patients, 23 M and 38 F, mean age 75+/-9 y, affected by Brady-Tachy Syndrome, implanted with a DDDR pacemaker, were randomized to DDDR or DDDR+CAP pacing with cross over of pacing modality after 1 month.

RESULTS

78 % of patients in DDDR pacing and 73 % in DDDR + CAP pacing (p=n.s.) were free from symptomatic paroxysmal atrial fibrillation recurrences. During DDDR+CAP pacing, the atrial pacing percentage increased from 77+/-29 % to 96+/-7 % (p<0.0001). Automatic mode switch episodes/day were 0.73+/-1.09 in DDDR and 0.79+/-1.14 (p=n.s.) in DDDR+CAP. In patients with less than 50 % of atrial pacing during DDDR, automaticmode switch episodes/day decreased during DDDR+CAP from 1.13+/-1.59 to 0.23+/-0.32 (p<0.05) and in patients with less than 90 % from 1.23+/-1.27 to 0.75+/-1.10 (p<0.001). The number of premature atrial complexes per day decreased during DDDR + CAP from 2665+/-4468 to 556+/-704 (p<0.02).

CONCLUSION

CAP algorithm allowed continuous overdrive atrial pacing without major side effects. Triggers of paroxysmal atrial fibrillation induction, such as premature atrial complexes, were critically decreased. Paroxysmal atrial fibrillation episodes were reduced in patients with atrial pacing percentage lower than 90 % during DDDR pacing.

Does atrial overdrive pacing prevent paroxysmal atrial fibrillation in paced patients?

The role of atrial overdrive pacing for the suppression of paroxysmal atrial fibrillation remains unclear. To investigate this we have performed a randomised study evaluating the role of an increased atrial base rate in suppressing this arrhythmia in patients implanted with a permanent pacemaker (Chorum ELA) for sick sinus syndrome with previous documented paroxysmal atrial fibrillation. Twenty-seven patients (mean age, 69; 15 female) were randomised to two 3-month single-blinded crossover periods of DDDR pacing. The pacemaker was set with a base rate of 60 bpm (normal) during one period and at 10 bpm (overdrive) above the average heart rate during the other, mean (S.D.) 75+/-7 beats/min (range, 70-96). The fallback algorithm of the pacemaker was activated to record the number and duration of paroxysmal atrial fibrillation episodes. During the overdrive period there was a significant increase in the total duration of atrial pacing (normal 60+/-26% vs. overdrive 72+/-28%, P<0.001). However there was no significant difference in the number of paroxysmal atrial fibrillation episodes (normal 43+/-109 vs. overdrive 43+/-106, P=ns), or their total duration (normal 42+/-108 h vs. overdrive 99+/-254 h, P=ns). In conclusion, atrial overdrive pacing, achieved by increasing the atrial base rate, has no incremental benefit in the suppression of paroxysmal atrial fibrillation when compared to rate responsive pacing with a base rate of 60 bpm.