Optimal Anti-tachycardia Therapy in Implantable Cardioverter-defibrillator (ICD) Patients Without Pacing Indications

All patients will receive an implantable cardioverter defibrillator OVATIO™ DR model 6550 or a later Sorin Group device offering the same functions. After Enrolment visit but before implant, patients will be randomized in two arms according to the parallel study design. Whenever possible before implant there will be the first Holter recording for the Tvar risk stratification procedure. In case Tvar recording could not be performed before implant it has to be performed before patient leaves the hospital post implant in unpaced rhythm. The dual-chamber arm will be programmed to 3 detection zones with PARAD+ activated. The TDI for the slow VT zone will be set to 500 ms (120 bpm - or in case the resting rate is higher than 90 bpm it is recommended to adjust this parameter to: resting rate + 30 bpm) and at least one ATP program activated as specified in table 1. A VT zone with a TDI of 353 ms (170 bpm) in case of no history of VT or a TDI cycle length equalling slowest documented VT interval (spontaneous or induced) plus 50 ms is required. In this 2nd VT zone therapies need to be activated in this group. AAIsafeR2 mode will be activated with a basic rate of 60 bpm. The single-chamber arm will be programmed to optimal detection with Acceleration (Onset), Stability and Long Cycle Search (VTLC) activated. A VT zone is requested in this group, with the same programming procedures as described above. Therapies will be set according to the clinical judgment of the participating investigators but a Slow VT-zone with TDI 500 ms in monitoring setting at least is required.