User's Manual

US-ENGLISH – 63
18.2. SAFER CLINICAL STUDY
SafeR mode in PARADYM RF is similar to that in Symphony.
The differences in SafeR mode between the two devices are:
─ To prevent long RR intervals during VT/VF, SafeR has no effect
during VT/VF therapy, electrophysiologic studies, and post-shock
recovery.
─ The maximum acceptable AV delay for first degree AV block
varies as a function of pacing rate.
─ PARADYM RF requires a ventricular sensed event to atrial paced
event (RA) interval of at least 100 ms. Therefore, the device
lengthens the atrial escape interval so that it ends at least 102
ms after the ventricular event.
─ During atrial fibrillation episode, pause criterion is fixed to 2s to
avoid long bradycardia episodes in switching to DDD mode.
Despite these differences, the data collected on Symphony devices
are applicable to PARADYM RF because the principles of SafeR
operation did not change. The criteria for switching from AAI to DDD
(or vice versa) did not change. The device’s method for evaluating
the presence of AV conduction did not change.
Methods: All patients were implanted with a Symphony Model 2550 dual-
chamber rate-responsive pacemaker with SafeR mode. A variety of
marketed atrial and ventricular pacing leads were used. The pacemaker
was programmed and interrogated via bi-directional telemetry using a
Sorin CRM dedicated programmer and a CPR3 programming head.
The study’s routine evaluation consisted of enrollment, pre-discharge
evaluation, and a scheduled follow-up visit at one month. At pre-
discharge, a 24-hour Holter recording was performed and pacemaker
memory was read. At one month, pacemaker memory was read.
Investigators also documented adverse events.
Patients studied: A total of 45 patients from 12 centers had Symphony
2550 pacemakers with SafeR. Of these, 14 (31 %) were female and 31