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

Atrial septal pacing for the termination of atrial fibrillation: study in a biophysical model of human atria

AIMS

While successful termination by pacing of organized atrial tachycardias has been observed in patients, single site rapid pacing has not yet led to conclusive results for the termination of atrial fibrillation (AF). The purpose of this study was to evaluate a novel atrial septal pacing algorithm for the termination of AF in a biophysical model of the human atria.

METHODS AND RESULTS

Sustained AF was generated in a model based on human magnetic resonance images and membrane kinetics. Rapid pacing was applied from the septal area following a dual-stage scheme: (i) rapid pacing for 10-30 s at pacing intervals 62-70% of AF cycle length (AFCL), (ii) slow pacing for 1.5 s at 180% AFCL, initiated by a single stimulus at 130% AFCL. Atrial fibrillation termination success rates were computed. A mean success rate for AF termination of 10.2% was obtained for rapid septal pacing only. The addition of the slow pacing phase increased this rate to 20.2%. At an optimal pacing cycle length (64% AFCL) up to 29% of AF termination was observed.

CONCLUSION

The proposed septal pacing algorithm could suppress AF reentries in a more robust way than classical single site rapid pacing. Experimental studies are now needed to determine whether similar termination mechanisms and rates can be observed in animals or humans, and in which types of AF this pacing strategy might be most effective.

Optimizing local capture of atrial fibrillation by rapid pacing: study of the influence of tissue dynamics

While successful termination by pacing of organized atrial tachycardias has been observed in patients, rapid pacing of AF can induce a local capture of the atrial tissue but in general no termination. The purpose of this study was to perform a systematic evaluation of the ability to capture AF by rapid pacing in a biophysical model of the atria with different dynamics in terms of conduction velocity (CV) and action potential duration (APD). Rapid pacing was applied during 30 s at five locations on the atria, for pacing cycle lengths in the range 60-110% of the mean AF cycle length (AFCL(mean)). Local AF capture could be achieved using rapid pacing at pacing sites located distal to major anatomical obstacles. Optimal pacing cycle lengths were found in the range 74-80% AFCL(mean) (capture window width: 14.6 ± 3% AFCL(mean)). An increase/decrease in CV or APD led to a significant shrinking/stretching of the capture window. Capture did not depend on AFCL, but did depend on the atrial substrate as characterized by an estimate of its wavelength, a better capture being achieved at shorter wavelengths. This model-based study suggests that a proper selection of the pacing site and cycle length can influence local capture results and that atrial tissue properties (CV and APD) are determinants of the response to rapid pacing.

Optimization of antitachycardia pacing protocols applied to atrial fibrillation: insights from a biophysical model

We present a model-based systematic study of antitachycardia pacing protocols applied to atrial fibrillation, focusing on the ability to achieve and maintain capture during pacing, as a function of both pacing site and period. We observed that pacing sites located away from anatomical obstacles led to faster and more robust capture. Moreover, after comparing burst and ramp pacing, our results indicate that in order to get capture it is necessary to pace at a fixed optimal period over a sufficient long time.

Pacing therapy for prevention of atrial fibrillation

The role of permanent pacing for the prevention of atrial fibrillation is reviewed. A moderate decrease in the incidence of acute and chronic atrial fibrillation has been seen with atrial pacing compared with ventricular pacing, especially in patients with sinus node dysfunction based on a meta-analysis of clinical trials. A variety of different pacing algorithms have been studied in small numbers of patients for only short durations of time and have shown an inconsistent effect on different measures of atrial fibrillation burden. The interatrial septum or Bachmann's bundle has been shown in some, but not all, studies to have a beneficial effect on reducing the incidence of atrial fibrillation. Less well studied is the combined benefit of alternate site atrial pacing combined with atrial fibrillation prevention pacing algorithms. Device measurement of the duration of atrial fibrillation appears to be an accurate measure of disease burden, and preliminary evidence suggests that atrial fibrillation burden is associated with an increased risk of stroke and death. Future studies are needed to demonstrate the long-term efficacy of device algorithms for the prevention or termination of atrial fibrillation.

Novedades en estimulación cardiaca 2006

This article summarizes progress in cardiac pacing that has taken place in the last year, such as the incorporation of navigation technology into programmers, systems for monitoring hemodynamic parameters, and new developments in patient follow-up, principally home monitoring and the use of treatment guidelines. In addition, the article covers recent findings in resynchronization therapy, paroxysmal atrial fibrillation, and the management of patients with pacemakers who need to undergo magnetic resonance imaging.