| 摘要 |
The pacemaker operates in a conventional manner unless a PVC premature ventricular contraction is sensed. If an extended atrial refractory period is triggered in an attempt to block any retrograde atrial events resulting from the PVC. This is followed by an artrial alert time window. After a prescribed A-V delay subsequent to the timing out or other termination of the atrial alert time window, a ventricular stimulation pulse is generated, unless prior ventricular activity is sensed that inhibits such ventricular stimulation pulse. Alternatively, the sensing of a PVC triggers, after a suitable refractory period, a retrograde sense period during which any sensed atrial electrical activity is presumed to be a retrograde event. Appropriate steps are taken in order to deal with the retrograde event to prevent its occurrence from triggering a PMT. If a PMP has started, a prescribed number of cycles of the PMT are counted, after which the same action used in response to a sensed PVC is triggered, which action disrupts the rhythm of the PMT so as to break it. If the PMT is not broken with the first attempt, the PVC response is recurringly generated after a prescribed number of subsequent PMT cycles.
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