| 摘要 |
The invention concerns an implantable medical device (pacemaker, cardioverter /defi-brillator) having a housing, containing an atrial and an ventricular sensing stage and a ventricular stimulation pulse generator, a ventricular pacing pulse timer, an atrial tachycardia/fibrillation detector a ventricular rate determination stage and a mode switching stage wherein the sensing stages and the stimulation pulse generator are at least indirectly connected to a lead-connector (in a header)for an intracardiac sensing/pacing lead to receive electrical signals from the atrium and the ventricle of a heart and to deliver pacing pulses to the ventricle of the heart, the atrial sensing stage is further connected to the atrial tachycardia/fibrillation detector (ventricular sensing stage may as well be connected to A-tach/Fib Detector in order to eliminate far-field senses of ventricular events in the atrium) the ventricular pacing pulse timer is connected to the ventricular sensing stage, to the ventricular stimulation pulse generator and to the ventricular rate determination stage, the ventricular pacing pulse timer is adapted to trigger the ventricular stimulation pulse generator to deliver a ventricular stimulation pulse upon time out of a ventricular escape interval (VEI) and to inhibit the delivery of a ventricular pacing pulse if a ventricular event is sensed by the ventricular sensing stage prior to time-out of the ventricular escape interval, the ventricular rate determination stage is adapted to generate an appropriate ventricular escape interval duration value and the mode switching stage is connected to the atrial tachycardia/fibrillation detector and to the ventricular pacing pulse timer to switch the pacing mode from an atrium-synchronous mode to a non-synchronous mode upon detection of an atrial tachycardia or atrial fibrillation or both, whereby a PIZ determination stage for determining a physiological interval zone (PIZ) which determines a range of appropriate ventricular escape interval duration values for the VEI determination and which is defined by an upper limit (ULPIZ) and a lower limit (LLPIZ), the upper limit defining a longest VV-Interval of the a physiological interval zone, the lower limit defining a shortest VV-interval of the a physiological interval zone, the a physiological interval zone extending between the upper limit and the lower limit. <IMAGE>
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