| 摘要 |
An implantable pacemaker operates in a DDD mode and reverts to a modified DDI mode in response to sensing atrial depolarization early in the pacing cycle. The modified DDI mode, when invoked, provides addtional atrial kick by generating an atrial stimulation pulse (A-pulse) (150) when there is sufficient time left in the current pacing cycle for the atrial kick resulting from such A-pulse to be of hemodynamic and electrophysiologic benefit. A time window, Ta (146), is defined that follows the post-ventricular atrial refractory period (PVARP) (144) of the normal DDD pacing cycle. If a P-wave (142) is sensed during Ta, then the modified DDI mode is invoked. In this mode, the time between the last ventricular event and the next scheduled V-pulse, absent the detection of an inhibiting R-wave, is preserved. Further, if there is sufficient time to supply an A-pulse before the next V-pulse is scheduled, such A-pulse will be generated to provide the additional atrial kick.
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