Atrial Septal Pacing to Synchronize Atrial Depolarization in Patients with Delayed Interatrial Conduction

Abstract

The current method of pacing the right atrium from the appendage or free wall is often the source of delayed intraatrial conduction and discoordinate left and right atrial mechanical function. Simultaneous activation of both atria with pacing techniques involving multisite and multilead systems is associated with suppression of supraventricular tachyarrhythmias and improved hemodynamics. In the present study we tested the hypothesis that pacing from a single site of the atrial septum can synchronize atrial depolarization. Five males and two females (mean age 58 +/- 6 years) with drug refractory paroxysmal atrial fibrillation (AF) were studied who were candidates for AV junctional ablation. All patients had broad P waves (118 +/- 10 ms) on the surface ECG. Multipolar catheters were inserted and the electrograms from the high right atrium (HRA) and proximal, middle, and distal coronary sinus (CS) were recorded. The atrial septum was paced from multiple sites. The site of atrial septum where the timing between HRA and distal CS (d-CS) was < or = 10 ms was considered the most suitable for simultaneous atrial activation. An active fixation atrial lead was positioned at this site and a standard lead was placed in the ventricle. The interatrial conduction time during sinus rhythm and AAT pacing and the conduction time from the pacing site to the HRA and d-Cs during septal pacing were measured. Atrial septal pacing was successful in all patients at sites superior to the CS o.s. near the fossa ovalis. During septal pacing the P waves were inverted in the inferior leads with shortened duration from 118 +/- 10 ms to 93 +/- 7 ms (P < 0.001), and the conduction time from the pacing site to the HRA and d-CS was 54.3 +/- 6.8 ms and 52.8 +/- 2.5 ms, respectively. The interatrial conduction time during AAT pacing was shortened in comparison to sinus rhythm (115 +/- 18.9 ms vs 97.8 +/- 10.3 ms, P < 0.05). In conclusion, simultaneous activation of both atria in patients with prolonged interatrial conduction time can be accomplished by pacing a single site in the atrial septum using a standard active fixation lead placed under electrophysiological study guidance. Such a pacing system allows proper left AV timing and may prove efficacious in preventing various supraventricular tachyarrhythmias.

Bachmann’s Bundle Pacing not Only Improves Interatrial Conduction but Also Reduces the Need for Ventricular Pacing

“…They showed that the right atrial appendage pacing resulted in the longest duration of activation within both atria as compared to the Bachmann's bundle and the in teratrial septum [4,[12][13][14][15]. The stimulation of the interatrial septum is deemed by many research ers to be the best pacing placement with regards to the activation time of both atria, which seems to be in line with the theoretical model [16,17]. In some studies this kind of atrial pacing was also combined with paroxysmal atrial fibrillation pre vention [18,19].…”

The Alternative Atrial Pacing Sites

“…It was shown that the stimulation of the right atrial appendage results in the longest activation of both atria in comparison to the Bachmann's bundle (13) and interatrial septum pacing site (7,(14)(15)(16). The stimulation of septum is considered in many papers to be the best pacing place with regard to the both atria activation time (17)(18)(19), which seems to be concordant with a theoretical model. In some p a p e r s t h i s k i n d o f a t r i a l stimulation site was also combined with the prevention of paroxysmal atrial fibrillation (20,21).…”

“…The histological structure of the Bachmann's bundle fascicles resembles more the Purkinje fascicle than the working muscle cells resulting in a faster interatrial conduction and thus shortening the P wave duration (50). The stimulation of the Bachmann's bundle shortens both atria electrical activation, shortens the P wave, improves the symmetry of the left atrial activation, shortens also the sinus node recovery time (18). The long-term electrophysiological properties (sensing, pacing threshold, resistance) of the Bachmann's bundle region in terms of permanent pacing are comparable with that of right atrium appendage.…”

Alternative pacing sites at the atrial level

“…16 Rationale for septal pacing and reduction of P-wave duration Bradycardia, disturbances of the autonomic nervous system, atrial dilatation, atrial stretch, and the presence of triggers (including atrial premature beats) are factors, which predispose to paroxysmal AF. 2,[17][18][19] These factors cause loss of homogeneity of refractoriness and conduction. Pacing can abolish several of these factors.…”

“…[1][2][3][4][5][6] There is growing evidence to suggest that pacing at the atrial level in the region of Bachmann's bundle, the interatrial septum (IAS) or even multiple atrial sites may have advantages in patients with atrial fibrillation. [6][7][8][9][10] However, these specific site pacing techniques require extremely accurate lead positioning compared with those used for conventional bradycardia indications.…”