Efficacy of Rate Modulators in Children With Single-Chamber Pacemakers

Pacemaker implantation is a well-approved method for certain bradyarrhythmias. In children with single-chamber pacemakers, and in those with sinus node dysfunctions, there are no intrinsic mechanisms for rate modulation. Rather, rate modulators serve to provide the required rate. The aim of this study was to assess the efficacy of pacemaker rate modulators in children. Twenty pacemaker-dependent children with single-chamber ventricular pacemakers were compared with the same number of children of the same age range without pacemakers. Efficacy of the rate modulators was assessed with treadmill exercise testing and compared with controls. Basal heart rates, exercise tolerance, maximal heart rates, and rate change slopes were studied. Basal heart rates, maximal heart rates, and exercise tolerance were significantly lower in the children with pacemakers. Age, sex, and body mass index had no effect on the heart rate slope during the exercise test. There was no significant difference between epicardial and endocardial pacemakers. In the children in this study, pacemaker accelerometers failed to meet physiological demands.