ZEIGLER, V., ET AL.: Is Activity Sensored Pacing in Children and Young Adults a Feasible Option? Activity sensing pacemakers are being utilized with increasing frequency in adults, but less frequently in the pediatric and young adult age group. We evaluated 12 young patients with activity sensing devices. Seven of the implanted devices were VVIRO, four were DDDRO and one was AAIRO. Patients ranged in age from 1–21 years, mean 9.3 years, median 8 years. Weights ranged from 8.25 to 80 kgs, mean 35 kgs, median 27.6 kgs. Anatomical diagnoses revealed six normal hearts, two P/O tetralogy, one P/O transposition, two P/O ablations, and one P/O Fontan. Rhythm diagnoses included congenital complete atrioventricular block in five, acquired complete atrioventricular block in three, sinus bradycardia in two, and His-bundle catheter ablation in one patient. Rate responsive settings of medium and 7 were used in 10 out of 12 patients. Treadmill exercise testing showed that 5 out of 7 patients' rates were controlled by the activity sensor at peak exercise while two were tracking sinus rhythm (average rate increase was 76.8 ppm in the five patients). Ambulatory monitoring revealed that 10 out of 12 patients used their activity sensor to control their heart rate (average rate increase was 54 ppm). Follow-up has ranged from 1–26 months, mean 6.8 months, median 5.5 months. There was one death. Effective rate modulated, activity sensing pacing was achieved in 7 out of 9 young patients. It should be considered when the atrium itself is not a feasible sensor.