| 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 additional atrial kick by generating an atrial stimulation pulse (A-pulse) 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, is defined that follows the post-ventricular atrial refractory period (PVARP) of the normal DDD pacing cycle. If a P-wave is sensed during TA, then the modified DDI mode is invoked. In such modified DDI 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, in such modified DDI mode, 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. In one embodiment, if there is more than a fixed time interval e.g., 300 msec, plus a programmed AV delay (AVD) time remaining before the next scheduled V-pulse after sensing a P-wave during the time window TA, then an A-pulse is generated one AVD time prior to the next scheduled V-pulse.
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