Abstract
Heart rate variability (HRV) is a sensitive marker of autonomic regulation. This study examined adolescents in the long-term postoperative period after early surgical correction of aortic coarctation (CoA) compared with age-matched healthy peers. Seventy adolescents (35 CoA, 35 controls; 12-17 years) underwent 5-min resting ECG and respiratory monitoring. HRV was analyzed using time domain, frequency domain, and nonlinear methods; respiratory rate was included as a covariate in ANCOVA models. Adolescents with repaired CoA showed lower time domain indices (SDNN, RMSSD, pNN50; all p < 0.01), reduced total spectral power (p = 0.002), and higher VLF (p < 0.001). Group differences in SDNN, RMSSD, and the LF/HF remained significant after adjustment for respiratory rate, indicating that autonomic alterations were not explained by breathing patterns. Nonlinear analysis revealed reduced Poincaré plot parameters (SD1, SD2; p < 0.01) and higher fractal scaling (DFA Alpha2; p < 0.001) in the CoA group, whereas entropy measures and DFA Alpha1 did not differ. These findings demonstrate persistent and selective alterations in autonomic regulation during adolescence despite anatomically successful repair. The coexistence of altered and preserved HRV features suggests domain specific reorganization rather than uniform loss of complexity. Nonlinear HRV indices may improve long term monitoring and help guide individualized rehabilitation.