Undesirable XXXX associated with rate hysteresis pacemakers.

@entity1 @entity1353 @entity713 @entity425 @entity2224 @entity955 @entity943
The introduction of the ventricular inhibited pulse generator with the feature of rate hysteresis has been associated with a variety of rhythm disturbances, some causing serious concern. This pulse generator has two different pacing rates: (1) the automatic rate, which is the interval between two successive paced beats (usually 860 msec or 70/min), and (2) the hysteresis interval, which results in a 1,000 msec delay between a sensed cardiac contraction and the next pacemaker discharge. The hysteresis interval after a sensed signal may result in long pauses that may predispose to the development of serious @entity943 . Two examples of this type of complication were recently observed. One @entity1 had bigeminal rhythm with mechanically ineffective cardiac contractions and an effective cardiac rate of 35/min; he experienced @entity1353 and @entity425 during these prolonged episodes. Another @entity1 had repeated episodes of @entity2224 . The @entity943 were not controlled by antiarrhythmic agents, and both @entity1 required replacement of the pulse generator. The proposed advantages of pulse generator hysteresis are (1) prolongation of battery life, and (2) maintenance of effective atrial transport; these advantages may be outweighed by undesirable @entity943 that may be associated with this mode of pacemaker function. Rate hysteresis cardiac pacemakers should be reserved for @entity1 having predominantly sinus rhythm without ventricular irritability. In @entity1 with frequent ectopic ventricular activity, @entity955 or high degree @entity713 , the rate hysteresis pacemaker offers no advantage over the conventional demand pacemaker. For @entity1 with frequent ectopic ventricular activity not easily controlled by antiarrhythmic agents, consideration should be given to the use of a permanent demand pacemaker with external rate control, which may provide greater flexibility in @entity943 management.
