SAFE Unsound: Right Atrial Septal and Overdrive Pacing Fail to Prevent Progression of AF
The prevalence of atrial fibrillation (AF) in the entire US population is approximately 1%.1 The prevalence of AF increases substantially with age, with up to 9% of patients over the age of 80 developing AF. The population presenting with permanent pacing requirements also increases with age and the cumulative lifetime risk of developing paroxysmal AF in pacemaker patients may be as high as 40%.2
Mechanisms for AF initiation and maintenance are multiple, but are widely accepted as a result of initiation by atrial premature beats (APB), and maintenance through multiple wavelets of reentry dependent on inhomogeneous atrial refractory periods (ARP) and atrial conduction velocities (ACV). Atrial pacing may prevent both AF triggers and atrial substrate changes by suppressing APB and inducing a more homogenous atrial landscape of refractory periods and conduction velocities. Atrial based pacing is clearly superior to ventricular pacing alone in preventing atrial fibrillation with an 18% relative risk reduction with atrial based pacing over a 3 year follow up.3 This treatment effect has been postulated to be the result of APB suppression and changes in ARP and ACV as a result of atrial stretch due to higher atrial pressure from AV dyssynchronous pacing. The atrial changes associated with atrial based pacing could possibly be enhanced by atrial overdrive pacing algorithms and/or by alternative sites for atrial pacing such as the atrial septum. The role of alternative site atrial pacing in the primary prevention of AF in pacemaker patients and to reduce the progression of AF (secondary prevention) is also not well established. In addition, despite the initial enthusiasm for overdrive atrial pacing algorithms, the recent ASSERT trial did not demonstrate any efficacy with overdrive atrial pacing in the primary prevention of AF.4
- Received July 12, 2013.
- Accepted July 16, 2013.