Background: Optimizing dual-chamber pacing to prevent recurrences of atrial tachyarrhythmias (AT) in sinus node dysfunction is still debated. Despite the large number of studies, efficacy of sophisticated preventive algorithms has never been proven. It is not clear whether this is due to imperfect study designs or to a substantial inefficacy of pacing therapies.
Aim: To intraindividually compare AT burden between an atrial overdrive and two heart rate modulation approaches: a conventional accelerometric-sensor-based DDDR mode and a contractility-driven rate responsive closed loop (CLS) algorithm.
Methods and results: Four hundred fifty-one patients with Brady-Tachy syndrome (BTS), severe bradycardia, and a documented episode of atrial fibrillation were enrolled. One month after implant, each pacing therapy was activated for 3 months in random order. A simple log transformation was used to handle large and skew AT burden distributions. Estimates were adjusted for false-positive AT episodes and reported as geometric means (95% confidence interval). A significantly higher AT burden was observed during overdrive, 0.14% (0.09%, 0.23%) (adjusted, 0.12%[0.07%, 0.20%]). Both DDDR and CLS performed better: respectively, 0.11% (0.07%, 0.17%) (adjusted, 0.08%[0.05%, 0.14%]), 0.06% (0.03%, 0.09%) (adjusted, 0.04%[0.03%, 0.07%]). All the comparisons were statistically significant. During overdrive significantly more patients had AT episodes of duration between 1 minute and 1 hour. No significant differences were observed for longer episodes.
Conclusions: Atrial overdrive showed the worst performance in terms of AT burden reduction and should not be preferred to heart rate modulation approaches that still have to be considered as a first-choice pacing mode in BTS.