| 摘要 |
A microprocessor-controlled pacemaker is programmed to extend an atrial refractory interval in response to the detection of events which could initiate a pacer sustained tachycardia. The extended atrial refractory interval ensures that a spurious atrial event resulting from retrograde conduction of a ventricle event will not cause a pace of the ventricle. The pacer is also programmed to break out of a pacer sustained tachycardia by inhibiting a ventricular pace when a predefined number of previous successive ventricular paces have occurred at the ventricular rate limit. The pacer is further programmed so that in response to a high atrial rate, the ventricle is paced at either a predefined ventricular upper rate limit value or at a rate limit value that is decremented to a fallback rate limit value. The pacer further increases the VA interval when the ventricle is paced at the ventricular rate limit. The pacer is also programmed to show Wenckebach behavior and thereby occasionally drop a ventricular pace in response to an atrial rate that exceeds the ventricular rate limit. The pacer resets the defined ventricular rate limit to an upper rate limit value when two successive ventricular paces are provided at a rate less than the defined ventricular rate limit. A nonphysiological interval is defined after an atrial pace. If a ventricular event is detected during the nonphysiological interval, the ventricle is paced at a predefined time period following the initiating atrial event.
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