Atrioventricular Interval Extension Is Highly Efficient in Preventing Unnecessary Right Ventricular Pacing in Sinus Node Disease: A Randomized Cross-Over Study Versus Dual- to Atrial Single-Chamber Mode Switch.

OBJECTIVES: This study sought to compare the Intrinsic Rhythm Support (IRSplus) and Ventricular Pace Suppress (VpS) in terms of right ventricular pacing percentage (VP %), mean atrioventricular interval (MAVI), atrial fibrillation, and cardiac volumes. BACKGROUND: Modern pacemakers are provided with algorithms for reducing unnecessary ventricular pacing. These may be classified as: periodic search for intrinsic atrioventricular (AV) conduction prolonging the AV delay accordingly; or DDD-ADI mode switch. The IRSplus and VpS algorithms belong to the former and latter classes, respectively. METHODS: Patients with sick sinus dysfunction without evidence of II/III degree AV block were 1:1 randomized to 6-month periods of either IRSplus or VpS, and then crossed over. Subsequent follow-ups were at the 12th month after randomization for device data retrieving, and at the 18th month with the same device programming for echocardiographic assessment. RESULTS: A total of 230 patients (62% males, median age 75 years [interquartile range: 69 to 79 years]) were enrolled. At a linear mixed-model analysis with order of treatment and investigational sites as nested random effects, differences in VP% and MAVI reached statistical significance: VP% was 1% (0% to 11%) during IRSplus and 3% (0% to 26%) during VpS (p = 0.029); MAVI was 225 ms (198 to 253 ms) during IRSplus and 214 ms (188 to 240 ms) during VpS (p = 0.014). No differences were observed in atrial fibrillation burden and incidence, ejection fraction, and cardiac volumes. CONCLUSIONS: Both IRSplus and VpS algorithms ensured VP% ≤3% in most patients with sinus node dysfunction and preserved AV conduction. The IRSplus was slightly more efficient in reducing VP% at the expense of a small MAVI increase, with statistical but clinically insignificant differences. (Ventricular Pace Suppression Versus Intrinsic Rhythm Support Study; NCT01528657).

Overdrive versus conventional or closed-loop rate modulation pacing in the prevention of atrial tachyarrhythmias in Brady-Tachy syndrome: on behalf of the Burden II Study Group.

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.