| 摘要 |
A pacemaker capable of automatically adjusting the sensitivity of its sense amplifier to electrical cardiac signals is disclosed. In one embodiment, a pacemaker having a pressure sensor disposed on the distal end of its pacing/sensing lead counts the number of pressure events and electrical events which occur during an autosensitivity timing period. If the number of electrical events exceeds the number of pressure events by more than a predetermined margin, the sense amplifier's sensitivity threshold is decreased. If the number of electrical events does not exceed the number of pressure events by more than the predetermined margin, the sense amplifier's sensitivity threshold is increased. In another embodiment, the pacemaker maintains a running average of the peak voltages of sensed electrical events over a predetermined history period. Periodically, the pacemaker computes the ratio of the running average of peak voltages to a preprogrammed sense margin value, and adjusts the sensitivity threshold of the sense amplifier according to this computation. By basing the adjustment of the sense amplifier's sensitivity threshold on a long-term average of peak sense values, the effects of cycle-to-cycle variation in sensed values are minimized. In still another embodiment of the invention, a pressure sensor alone is employed to detect natural cardiac events. |
