Autonomic Disturbances in Children with Nutcracker Syndrome: A Case Control Study.

Objective: To describe the autonomic nervous system abnormalities including frequency of orthostatic symptoms, orthostatic response to the active standing test and analysis of heart rate variability (HRV) parameters in children with Nutcracker syndrome (NCS).

Methods: A case-control study was conducted between May and November 2023. We included children with NCS and healthy age- and sex-matched healthy controls. Children were evaluated for autonomic system disturbances by history for orthostatic symptoms, performance in an active standing test, 24-hour holter monitoring to determine the heart rate variability (HRV), maximum and minimum heart rates, and the average heart rate and urine analysis for orthostatic proteinuria and hematuria.

Results: 45 children with NCS and 47 age-matched healthy controls were included. Orthostatic symptoms were observed in 55.5% of the NCS patients, with dizziness being the predominant complaint (37%), followed by fatigue (20%), palpitations (13%), headache (11%), vision disturbances (11%), syncope (6%), chest discomfort (4%), and diaphoresis (2%). In the 24-h holter monitoring of 24 patients, a decrease in the standard deviation of the NN intervals (SDNN), root mean square of successive R-wave peak to R-wave peak (RR) interval differences (rMSSD) was observed. SDNN was significantly lower in NCS compared to the control group; 135.5 (42.3) vs 155.9 (35.2), P = 0.039. rMSDD was also significantly lower in the NCS compared to control group; 46.2 (19.7) vs 61.3 (26.6), P = 0.020. The mean (SD) maximum heart rate was higher in NCS compared to control group; 172.3 (28.4) vs 159.4 (14.6), P = 0.015.

Conclusion: Autonomic nervous system dysfunction and orthostatic disturbances may be seen in children with NCS.