Reinnervation after heart transplantation in children: Results of short-time heart rate variability testing

Aims: To detect impairment in short-term heart rate variability (HRV) in children after heart and heart-lung transplantation (TX) as reported in adults. To assess vagal and sympathetic influence on the donor heart rate using frequency domain analysis of HRV. Methods and Results: Measurement of short-term HRV was performed in 17 patients (age 16.9 +/- 3.6, 6.1 +/- 3.7 yr after TX) and 12 healthy controls (age 14.8 +/- 3.0 yr). Testing consisted of a resting phase of 15 minutes followed by a tilt phase of 45 min. All HRV parameters were significantly impaired in transplanted patients: RR interval (RRI) 717.2 +/- 122.5 m/s (controls 827 +/- 139.7, p < 0.05), standard deviation of RR interval (RRI-SD) 20.1 +/- 15.5 (89.9 +/- 38.4, p < 0.001), RRI at tilt 607.9 +/- 79.7 (654.0 +/- 104.7, NS), RRI-SD at tilt 21.1 +/- 20.0 (60.4 +/- 31.4, p < 0.001). Low-frequency (LF)/High-frequency (HF) ratio of HRV showed prominent sympathetic influence in TX-patients (3.38 +/- 5.60 vs. 1.18 +/- 0.86, NS) increasing during tilting (5.91 +/- 8.36 vs. 4.74 +/- 5.27, NS). In subgroup analysis, 4 yr after TX an increasing sympathetic control of heart rate was observed. Conclusion: Short-term HRV is severely impaired in children after TX. If changes are observed, they are time-related and show increasing sympathetic influence starting from 4 yr after TX.