Patent ID: 6505070
Filing Date: 2003-01-07
Classification: A61N

Abstract:
A dual-chamber cardiac pacemaker comprising:atrium sensing means for sensing an electrical activity event in the vestibule and producing an atrium electrical activity signal, and ventricle sensing means for sensing an electrical activity event in the ventricle of a heart and producing a ventricle electrical activity signal; a timer for detecting the time of the occurrence of the electrical activity event and producing a timer signal; ventricle stimulation means for producing stimulation pulses and outputting same to the ventricle; and a stimulation control unit for time control of the production and output of the stimulation means, said stimulation means comprising switching means for switching over from an asynchronous to a vestibule-synchronous mode, criterion memory means for the storage of at least one switching-over criterion for mode switching-over, and a processing unit for processing signals from the atrium sensing means, the ventricle sensing means and the timer and for checking fulfilment of the switching-over criterion, wherein: the criterion memory means has a signal sequence memory for storage of a predetermined selection of signal sequence patterns, the signal sequence patterns including electrical activity events reflecting the electrical activity of the heart selected from the group consisting of: signals from the atrium sensing means and the ventricle sensing means, signals from the ventricle stimulation means, and a time interval criterion which concerns the spacing between two atrially sensed events and signals from an atrially sensed event in relation to a ventricular activity event, the processing unit has comparison means for comparing the electrical activity events sensed by the atrium sensing means and the ventricle sensing means in a plurality of successive cardiac cycles to the stored signal sequence patterns, the signal sequence patterns being stored as follows: As-V-As wherein As-As>1.000 ms V-As-As-V wherein As-As>1.000 ms V-V-As wherein V-As>1.000 ms V-V without interposed As, wherein: As is an atrially detected event and V is a ventricularly detected or stimulated event, and the stimulation control unit further has counter means connected to the comparison means for counting the number of cardiac cycles in which the electrical activity events sensed by the atrium sensing means and the ventricle sensing means is the same as one of the pre-stored signal sequence patterns within a predetermined total number of successive cardiac cycles and produce a representative output signal, the counting means being in signal communication with a control input of the switching means such that when the switching means receives the output signal from the counting means the switching means switches between the asynchronous and the vestibule-synchronous modes; wherein the stimulation control unit further comprises a test device having an output for outputting a test signal and a logic stage having at least one input, wherein the test device is designed to carry out, evaluate, and signal the results of an active test for the presence of retrograde transfer, the output of the test device being connected to the at least one input of the logic stage, the logic stage being connected between the counter means and the switching means, such that switching of the switching means depends on the presence of an output signal from the counter means and an output signal from the test device, indicating a positive test result; and wherein the test device has modulation means for producing a predetermined modulation of the time spacing of successive ventricle stimuli, VA-detection means for detecting and storing a plurality of VA-time intervals between a respective ventricle stimulus and a subsequent atrial activity, and VA-evaluation means for comparative evaluation of the VA-time intervals as a reaction to modulation of the time spacing of the ventricle stimuli.