RIVER: Portuguese registry to monitor unnecessary right ventricular pacing

The aim of this prospective registry is to evaluate a new algorithm designed to reduce the percentage of unnecessary ventricular pacing (%VP) in patients implanted with a dual-chamber pacemaker, through a dedicated pacing mode (called AAISafeR2) operating in AAI mode with back-up ventricular pacing in DDD mode, and to describe the incidence and distribution of atrioventricular (AV) block in this population. Investigators were free to assign patients to AAISafeR2 mode or to standard DDD (if AAISafeR was contraindicated, mainly due to permanent high-degree AV block). Patients underwent routine follow-up visits at 3, 6, 12, 18 and 24 months after implantation. At each follow-up visit, data were retrieved from pacemaker memories and analyzed to extract %VP and incidence of AV block. Up to December 2006, 158 patients (94 men, mean age 69 +/- 14 years) from nine Portuguese centers had been consecutively included. We also determined the distribution of AV block (according to the criteria used by the pacemaker to classify AV block and switch to DDD mode). AAISafeR was shown to be effective in reducing unnecessary VP in our patient population. The analysis also reveals a high incidence of paroxysmal AV block, often unknown at the time of implantation. There were no complications associated with AAISafeR programming.