Rate-Responsive Pacing Using Electrographic Parameters as Sensors

The use of evoked QT-interval and ventricular depolarization gradient as sensors for rate-responsive pacing is described in this article. The QT interval has been used as a biosensor in implantable pacemakers since 1981, and recent refinements have improved the rate response characteristics and simplified the programming of this pacemaker. Recently, QT and activity sensing have been combined to produce a dual-sensor rate-responsive pacemaker that may offer advantages over single-sensor devices. The ventricular depolarization gradient has been incorporated into a closed-loop rate-responsive pacing system and is undergoing clinical evaluation.