[A new dual-chamber pacemaker with an automatic antitachycardia system in the treatment of the bradycardia-tachycardia syndrome].

A new dual-chamber pacemaker with automatic tachycardia terminating system was used in three patients with bradycardia-tachycardia syndrome. This pacemaker (Medtronic Symbios 7008) is a multiprogrammable, bipolar device with bidirectional telemetry and six permanent pacing modes (DDD-DVI-VVI-DOO-VOO-AOO). The antitachycardia system can be programmed in two different modes: underdrive dual demand and overdrive atrial burts (1 to 16 stimuli with selectable coupling interval from 135 to 360 msec). The pacing modes are automatically activated when five consecutive R-R cycles shorter than the tachycardia detection interval are sensed. The pacemaker may sense the ventricle (when set on VVI or DVI mode) or sense both the atrium and the ventricle (in DDD mode). The pacemaker was programmed on DVI mode in all three patients, and the overdrive atrial burst program was used for tachycardia termination, with promptly and costantly effective results. The underdrive dual demand program was tested after the implantation, but it did not show constant results because inefficacy or late termination of tachycardias.