Can current minute ventilation rate adaptive pacemakers provide appropriate chronotropic response in pediatric patients?

Since children have different activity patterns and exercise responses, uncertainty exists as to whether minute ventilation (MV) sensors designed for adults provide adequate chronotropic response in pediatrics. In particular, high respiratory rates (RR > 48 breaths/min), which are characteristic of the ventilatory response to exercise in children, cannot be sensed by MV rate responsive pacemakers. The purpose of this study was to evaluate the MV sensor rate response of the Medtronic Kappa 400 using exercise data from healthy children in a computer simulation of its rate response algorithm. Thirty-eight healthy children, ages 6-14, underwent a treadmill maximal exercise test. Subjects were divided based on body surface area (BSA) and MV rate response parameters were selected. Respiratory rates and tidal volumes were entered into the Kappa 400 rate response algorithm to calculate sensor-driven rates. Intrinsic heart rate (HR), oxygen uptake, and sensor-driven rates were normalized to HR reserve (HRR), metabolic reserve (MR), and sensor-driven reserve to compare across groups. Linear regression analysis among sensor-driven rate reserve, HRR, and MR was performed as described by Wilkoff. The mean slopes (+/- SD) of the relationships between the sensor-driven rate reserve and HRR were 1.06 +/- 0.34, 1.07 +/- 0.28, and 1.01 +/- 0.19 for children with BSA < 1.10 m2, 1.10 < BSA < 1.40 m2, and BSA > 1.40 m2, respectively. High correlations were found between sensor-drive rates and HR responses and between sensor-drive rates and MV throughout exercise. No significant differences were noted between sensor-drive rates and HR using the Wilkoff model. From this study the authors conclude that: (1) MV is a good physiological parameter to control heart rate and (2) simulated sensor-driven rates closely match intrinsic HRs during exercise in healthy children, which supports the appropriateness of clinical validation in pediatric pacemaker patients.