Single-site Atrial Pacing Research Articles

Can linear triple-site atrial pacing reinforce the electrical treatment of atrial fibrillation?

This editorial refers to ‘Atrial activation time and pattern of linear triple-site vs. single-site atrial pacing after cardioversion in patients with atrial fibrillation’ by J.-I. Choi et al., on page 508. In their recent editorial commentary on the role of atrial pacing in prevention or interruption of atrial tachyarrhythmias, Janko and Hoffmann1 have concluded that today this treatment is of the arbitrary value and finished off with the statement ‘do we still need to talk about it?’ Indeed, despite more than a decade of significant intellectual investments and numerous clinical trials exploring a vast spectrum of pacing algorithms, pacing sites, and lead configurations, the majority of published data indicate unsatisfying short- or mid-term prevention or suppression of atrial fibrillation (AF) and atrial tachycardia (AT). The reasons for these poor results have been well documented and include: (i) the inability to adequately suppress predominantly left atrial sided triggers and/or penetrate the initial circulatory wave fronts, (ii) delayed interruption of AT/AF because of time needed for classifying and confirming the type of the already ongoing and nested atrial tachyarrhythmias, and (iii) incorrect pattern recognition. Most serious of all, adverse effects of inappropriate antitachycardia or overdrive pacing by provoking AT/AF instead of suppressing or preventing the arrhythmia due to incorrect or not timely diagnosis often emerge. Presently, classical sick sinus syndrome with a low incidence of paroxysmal AT/AF remains the best indication for this electrical therapy while patients with … *Corresponding author. Tel: +31 817559801; fax: +31 302516396, Email: n.m.vanhemel{at}hetnet.nl

Atrial activation time and pattern of linear triple-site vs. single-site atrial pacing after cardioversion in patients with atrial fibrillation

Multisite atrial pacing has been suggested to be effective in suppressing atrial fibrillation (AF), however, the effect of linear triple-site atrial pacing (LTSP) in humans has not been evaluated. We compared the effects of LTSP to single-site atrial pacing (SSP) on the atrial activation and wavefront propagation pattern in patients with persistent AF. In 10 patients with persistent AF, the effects of LTSP and SSP were evaluated by left atrial (LA) endocardial non-contact multielectrode array mapping and multipolar catheters. LTSP and SSP were delivered from the high right atrium (HRA), the distal coronary sinus (CS), and within the LA at the site showing maximal overlay of low-voltage zones during sinus rhythm and pacing at HRA and CS. Atrial activation time and pattern, P wave duration, and the prevention of AF induced by burst pacing were assessed with these pacing interventions. Compared with SSP, LTSP at the HRA, CS, and LA shortened atrial activation times (183 +/- 24 vs. 174 +/- 24 ms, 186 +/- 29 vs. 166 +/- 28 ms, and 171 +/- 40 vs. 163 +/- 39 ms; P < 0.05, respectively). P wave duration was shorter with LTSP than SSP at all three sites (141.7 +/- 35.1 vs. 146.9 +/- 38.5 ms, 138.1 +/- 34.6 vs. 145.7 +/- 33.7 ms, and 142.7 +/- 33.4 vs. 151.3 +/- 35.1 ms; P < 0.05, respectively). LTSP initially depolarized a larger area than SSP, and produced more uniform and planar wavefront propagation. LTSP prevented the burst-induction of AF during LA pacing in 3 of 10 patients, while SSP was never successful. In patients with persistent AF, LTSP provided more rapid and uniform activation of the atria compared with SSP, which was associated with prevention of burst-induction of AF in some patients. Further study is required to determine whether LTSP can modify the substrate of chronic AF, leading to frank AF suppression.

Atrial antitachycardia pacing: do we still need to talk about it?

Since first described in 1968,1 sick sinus syndrome (SSS) has become one of the most frequent indications for pacemaker implantation. Although in early days, the presence of atrial fibrillation (AF) limited the use of pacemakers in patients with SSS, nowadays pacemakers play an important role in the management of AF in patients with SSS. Highly sophisticated devices have been developed with increased Holter capabilities allowing continuous rhythm monitoring. Although the prevalence of AF prior to pacemaker implantation has been found in the range of 40–45%,2 AF detection during follow-up using pacemaker Holter data is reported in 50–65% of patients with SSS.3,4 In the Mode Selection Trial (MOST), pacemaker-detected paroxysmal AF was a strong independent predictor of stroke, death, and persistent AF, whereas symptoms as a clinical comparator could not reliably predict AF recurrence.4 The known limited success rate of drug therapy for rhythm control and the overwhelming number of pacemaker patients with paroxysmal AF prompted interest in using pacing therapy to treat AF. Therapy options developed included alternative single-site atrial pacing, multisite atrial pacing, pacing algorithms to prevent AF by increasing the amount of atrial pacing suppressing triggers of AF, and atrial antitachycardia pacing (ATP) to terminate AF. Many clinical trials have been conducted over the past 10 years studying the efficacy of pacing algorithms for AF prevention and termination. The present paper by Gillis et al. 5 reports the first long-term data on atrial ATP. Neither ATP alone nor ATP in combination with preventive pacing algorithms could successfully suppress atrial tachycardia (AT)/AF during a follow-up period of 3 years. The trial was early terminated due to phasing out of the AT500/501 pacemaker and study results may have been underpowered to detect any differences. However, the results correlate well with other ATP studies like … *Corresponding author. Tel: +49 89 9270 2071, Fax: +49 89 9270 2683, Email: ellen.hoffmann{at}klinikum-muenchen.de

Role of Permanent Pacing to Prevent Atrial Fibrillation

This advisory summarizes the current database on pacing modalities and algorithms used to prevent and terminate atrial fibrillation (AF). On the basis of the evidence indicating that ventricular pacing is associated with a higher incidence of AF in patients with sinus node dysfunction, a patient who has a history of AF and needs a pacemaker for bradycardia should receive a physiological pacemaker (dual chamber or atrial) rather than a single-chamber ventricular pacemaker. For patients who need a dual-chamber pacemaker, efforts should be made to program the device to minimize the amount of ventricular pacing when atrioventricular conduction is intact. Many pacemakers and implantable defibrillators have features designed to prevent AF and to terminate AF with rapid atrial pacing. The evidence to support their use is limited, although these algorithms appear to be safe and usually add little additional cost. For patients who have a bradycardia indication for pacing and also have AF, no consistent data from large randomized trials support the use of alternative single-site atrial pacing, multisite right atrial pacing, biatrial pacing, overdrive pacing, or antitachycardia atrial pacing. Even fewer data support the use of atrial pacing in the management of AF in patients without symptomatic bradycardia. At present, permanent pacing to prevent AF is not indicated; however, additional studies are ongoing, which will help to clarify the role of permanent pacing for AF.

Intra- and interatrial conduction delay: implications for cardiac pacing.

Atrial conduction disorders are frequent in elderly subjects and/or those with structural heart diseases, mainly mitral valve disease, hyperthrophic cardiomyopathies, and hypertension. The resultant electrophysiological and electromechanical abnormalities are associated with a higher risk of paroxysmal or persistent atrial tachyarrhythmias, either atrial fibrillation, typical or atypical flutter or other forms of atrial tachycardias. Such an association is not fortuitous because intra- and interatrial conduction abnormalities delays disrupt (spatial and temporal dispersion) electrical activation, thus promoting the initiation and perpetuation of reentrant circuits. Preventive therapeutic interventions induce variable, sometimes paradoxical effects as with the proarrhythmic effect of class I antiarrhythmic drugs. Similarly, atrial pacing may promote proarrhythmias or an antiarrhythmic effect according to the pacing site(s) and mode. Multisite atrial pacing was conceived to correct, as much as possible, abnormal activation induced by spontaneous intra- or interatrial conduction disorders or by single site atrial pacing, which are situations responsible for commonly refractory arrhythmias. Atrial electrical resynchronization can also be used to correct mechanical abnormalities like left heart AV dyssynchrony resulting from intraatrial conduction delays.

Effects of Biatrial Pacing in Prevention of Postoperative Atrial Fibrillation After Coronary Artery Bypass Surgery

Atrial fibrillation (AF) is common after coronary artery bypass surgery (CABG) and results in prolonged hospitalization. The purpose of this study was to evaluate the efficacy of biatrial pacing in preventing post-CABG AF compared with single-site atrial pacing. A total of 132 patients who had no history of AF and who underwent CABG were randomized to 1 of the following 4 groups: biatrial pacing (BiA), left atrial pacing (LA), right atrial pacing (RA), or no pacing (control) in postoperative period. Overdrive atrial pacing was performed for 5 days. The incidence of AF was significantly reduced in the BiA group (12.5%) compared with the other 3 groups (LA, 36.4%; RA, 33.3%; control, 41. 9%; P<0.05). The mean length of hospital stay was significantly reduced in the BiA group. At baseline, the mean P-wave duration (P(dur)) and dispersion (P(dis)) were not prolonged. BiA pacing resulted in the most significant percentage of reduction in P(dis) when compared with the LA or RA groups (BiA, 42+/-8%; LA, 13+/-6%; RA, 10+/-9%; P<0.05 for BiA versus LA or RA). No significant differences existed in mean P(dur) and P(dis) between patients who developed AF and those who remained in sinus rhythm at baseline. However, only those patients who remained in sinus rhythm had a significant reduction in mean P(dur) and P(dis) after pacing therapy. Biatrial overdrive pacing is more effective in preventing post-CABG AF than single-site atrial pacing; this therapy also results in a shortened hospital stay. The overall reduction in atrial activation time with BiA pacing was reflected in the reduction in P(dis).

Regional right and left atrial activation patterns during single- and dual-site atrial pacing in patients with atrial fibrillation

We examined the activation of the right atrium and left atrium by pacing from different atrial sites using several single- and dual-site atrial pacing modes in patients with atrial fibrillation or flutter. We also analyzed the effect of these pacing modes on fixed coupled extrastimuli in this population. Patients underwent detailed mapping of regional right atrial (RA) and left atrial (LA) sites. Bipolar pacing was performed individually from the high right atrium, coronary sinus ostium, and the distal coronary sinus, and simultaneously from the high right atrium and coronary sinus ostium (dual-site RA pacing) or high right atrium and distal coronary sinus (biatrial pacing). Extrastimuli were delivered from the high right atrium at fixed coupling intervals of 350 and 250 ms. Twenty patients with atrial fibrillation were studied. P-wave duration during pacing was significantly abbreviated by both dual-site RA and biatrial pacing (p < 0.001 vs high RA pacing, respectively) but not by any other single-site atrial pacing method. Both dual-site atrial pacing modes also significantly abbreviated P wave durations for closely coupled high RA premature beats (p < 0.001) in contrast to high RA pacing. During the basic pacing drive and for high RA extrastimuli, RA activation at the crista terminalis and atrial septum was comparable in sinus rhythm, high RA pacing, and in both dual-site atrial pacing methods, but was significantly delayed by coronary sinus ostial and distal coronary sinus pacing. In contrast, proximal coronary sinus activation was delayed with high RA pacing compared with all other pacing modes, and high RA extrastimuli encountered reduced conduction delay at this location with dual-site atrial pacing modes. LA activation was advanced superiorly by both single-site coronary sinus pacing methods and both dual-site atrial pacing techniques. Inferior and lateral LA activation was advanced by all pacing modes using a coronary sinus pacing site. However, earlier activation of LA sites occurred for high RA premature beats after both dual-site pacing methods (p < 0.05) compared with single-site pacing modes. Incremental conduction delay at different atrial regions for closely coupled high RA extrastimuli ranged from 33% to 120% during high RA pacing and was significantly attenuated at multiple RA and LA sites by dual-site RA and biatrial pacing. Distinct global, as well as regional electrophysiologic effects, may mediate the variable antiarrhythmic effects of different and novel atrial pacing methods.

Randomized Prospective Pilot Study of Long-Term Dual-Site Atrial Pacing for Prevention of Atrial Fibrillation

To determine whether dual-site atrial pacing is feasible, safe, and effective. We undertook a randomized prospective single-blind crossover study. Nine patients with at least two episodes per month of symptomatic paroxysmal atrial fibrillation participated in a randomized crossover study involving three separate 3-month blocks of single-site atrial pacing, dual-site atrial pacing, and control (support-only) pacing. Dual-site atrial pacing resulted in shorter P wave duration (81 +/- 14 ms) than did single-site pacing (111 +/- 12 ms) or control sinus rhythm (123 +/- 9 ms) (P<0.0001) and in fewer premature atrial complexes on Holter monitoring (P = 0.06). The arrhythmia-free interval was longer with dual-site pacing (67 +/- 17 days) than with single-site (62 +/- 30 days) or support-only (49 +/- 34 days) pacing (P = 0.10). This pilot study was not statistically powered to detect a difference between pacing modes. (1) Dual-site atrial pacing is feasible and safe; (2) it shortens the P wave duration and tends to decrease premature atrial complexes on Holter monitoring; (3) any atrial pacing tends to prolong the arrhythmia-free interval; and (4) this pilot study enrolled too few patients to determine whether a significant difference in pacing modes exists and supports the need for a larger study.

Effects of Different Atrial Pacing Modes on Atrial Electrophysiology

Multiple-site atrial pacing has been shown to prevent recurrence of atrial fibrillation. However, information about the mechanisms of different atrial pacing modes in prevention of atrial fibrillation was not clear. Forty-two patients without structural heart disease were classified into group 1 and group 2 according to absence or presence of clinical atrial fibrillation, respectively. Atrial conduction time and electrogram width of the right posterior interatrial septum (RPS) were measured during drive-train stimulation (S1) and early extrastimulation (S2). The locations of S1 were the high right atrium (HRA), distal coronary sinus (DCS), or both sites simultaneously. Effective refractory periods (ERPs) of the HRA and DCS were also determined during S1 stimulation at each site and during biatrial pacing. The ERPs were not different between single-site atrial pacing and biatrial pacing. In contrast, early S2 stimulation at the HRA caused greater atrial conduction delay and greater increment of electrogram width of the RPS in patients with a history of atrial fibrillation. Biatrial pacing significantly reduced the conduction delay and electrogram width of the RPS caused by HRA extrastimulation. In addition, in 17 group 2 patients, atrial fibrillation was induced by an early HRA S2 coupled to HRA pacing. However, with the same coupling interval of S2 at HRA, only 6 of them had the arrhythmia induced during biatrial pacing. Furthermore, conduction delay and increase of electrogram width caused by early S2 at the HRA were reduced by biatrial pacing only in patients whose arrhythmia induction was successfully prevented by biatrial pacing. Biatrial pacing reduced both the atrial conduction delay and increase of electrogram width at the RPS caused by early S2 at HRA, and these effects could prevent induction of atrial fibrillation.

754-2 Dual Site Atrial Pacing for the Acute and Chronic Prevention of Atrial Fibrillation: A Prospective Study

We evaluated the feasibility of dual site atrial pacing (DAP) at the high RA & coronary sinus os &its efficacy in the immediate &chronic prevention of atrial fibrillation (AF) using a prospective crossover study design. 13 patients (pts) with drug refractory paroxysmal or chronic AF, mean age 68 ± 15 yrs, mean LV ejection fraction 49 ± 17%, mean LA diameter 37 ± 7 mm with &gt;2 documented episodes in prior 6 mos, were considered for DAR AF was induced using 1, 2 or 3 extrastimuli at 2 to 4 RA sites & DAP was tested acutely for prevention of induced AF. Chronic DAP was instituted using 2 atrial leads & 1 ventricular lead in the DDDR mode. DAP was switched to single site atrial pacing after 3 mos while remaining in the DDDR mode. Endpoint for failure with either pacing mode was recurrent AF needing new antiarrhythmic drugs or D.C. cardioversion. 11 pts had DAP tested acutely. Mean P wave duration was 120 ± 33 ms & PA interval was 49 ± 22 ms. The effective refractory period at the coronary sinus os was 225 ± 17 ms & at the high RA was 238 ± 22 ms (p &gt; 0.2). Acutely, DAP prevented AF in 4 of 11 pts. 8 pts had permanent pacemakers implanted to institute chronic DAR In 4 pts, DAP had been effective acutely in suppression of inducible AF whereas it was ineffective in 2 pts & was not tested in 2 pts. Atrial pacing threshold at the high RA was 0.9 ± 0.2V, at the coronary sinus os was 1.4 ± 0.2V, & with DAP was 1.5 ± 0.5V (p = 0.01 vs high RA). P wave amplitude at the coronary sinus os was 2.15 ± 0.85 mV, at the high RA was 2.75 ± 1.1 V, & with DAP was 2.52 ± IV During followup of 3 to 180 (mean 92) days, all 8 pts during DAP remained in sinus rhythm despite a decrease in antiarrhythmic drug use (mean 2.1 ± 1 before DAP vs 0.4 ± 0.5 after DAR p &lt; 0.001). 5 pts did not require any antiarrhythmic therapy & the remaining 3 were maintained on 1 previously ineffective drug. In 1 of 4 pts switched to single site atrial pacing, sustained AF recurred requiring cardioversion. (1) DAP is feasible & can be evaluated acutely at electrophysiologic study or chronically using currently available DOOR pacemakers. (2) Acutely, DAP can suppress inducible AF in selected pts. (3) Chronically, DAP can preventAF recurrences during intermediate term followup.