Historically pediatric pacing needs were met almost completely by single chamber fixed rate pacemakers. As pacemaker technology improved such that dual chamber pacemakers became smaller and atrially implanted electrodes became more reliable, the use of dual chamber pacemakers increased. In 1983 dual chamber pacemakers accounted for less than 20% of all generators implanted. This percentage has gradually increased with time such that approximately 45% of all generators implanted in 1993-1994 were dual chamber pacemakers. Had it not been for the development of single chamber rate variable generators this percentage may well be higher as the benefits of heart rate variability have become better appreciated. The major impediment to the use of dual chamber pacemakers currently is related to the difficulty of placing an atrial electrode particularily when the epicardial approach is required.
Variable rate pacing defined as the ability of the pacemaker to pace at a variable rate based either upon the intrinsic atrial rate or an activity sensor in the pacemaker has found increasing utility in the child. Meeting the variable metabolic demands imposed by activity in the child has been greatly aided by rate variable pacing. The use of such pacemakers has greatly increased over the years such that 65% to 80% of all generators implanted are initially programmed to a rate variable mode (DDD, VVIR, DDDR, AAIR). Greater than 95% of all generators implanted in 1993-1994 had the capability to be programmed into a rate variable mode even though such a mode had not been selected at the time of initial programming.
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