Reduction of Right Ventricular Pacing with Advanced Atrioventricular Search Hysteresis: Results of the PREVENT Study

BACKGROUND: Right ventricular pacing predisposes to the development of heart failure and atrial fibrillation. Automatic atrioventricular search hysteresis (AVSH) is a commonly used strategy to decrease the percentage of right ventricular pacing (%VP) in patients without permanent AV block, but the results have not been optimal. METHODS: The randomized, crossover PREVENT study evaluated whether an enhanced AVSH with two new features can reduce %VP compared with standard AVSH. The new features are the repetitive hysteresis [switch from extended to basic AV delay after a consistent loss of intrinsic AV conduction (IAVC) lasting for six consecutive atrial cycles] and the scan hysteresis (periodic IAVC search extension over six consecutive atrial cycles). Both standard AVSH and enhanced AVSH performed a periodic IAVC search every 180 cardiac cycles and operated with a basic AV-delay of 225 ms and a rate-independent maximum AV-delay of 300 ms for paced and sensed atrial events. RESULTS: Among 178 patients, 53.4% had no evidence of AV block at enrollment and 46.6% had history of intermittent AV block. The median %VP was decreased by enhanced AVSH compared to standard AVSH (4.0% vs 5.5%, P < 0.001), particularly in patients with a history of AV block (21.4% vs 25.5%, P < 0.001). The primary study hypothesis that 25% of all patients would experience > 20% relative %VP reduction was not met as 46 (25.8%) patients (95% confidence interval, 20.5-31.8%) presented such relative reduction. CONCLUSION: The enhanced AVSH algorithm reduces %VP compared with standard AVSH in patients with intermittent AV block.