| 摘要 |
There is disclosed a demand pacer which exhibits rate hysteresis without requiring additional active elements. The reference potential, to which the voltage across a timing capacitor is compared, is derived from the tap on a voltage divider, with an additional capacitor being connected across one branch of the voltage divider. Whenever the voltage across the timing capacitor exceeds the reference voltage, the pacer is triggered and the capacitor in the voltage divider circuit discharges slightly. This lowers the reference voltage so that the escape interval is shortened. The escape interval gets shorter and shorter during successive cycles when stimulating pulses are generated until a lower limit is reached. If successive spontaneous beats are detected, the capacitor continuously charges until the escape interval is at the maximum limit. It requires 2-6 seconds for the escape interval to change from one extreme to the other.
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