Impact of Kidney Transplantation on Heart Rate Variability: A Narrative Review

Abstract

Cardiovascular disease is the leading cause of mortality in patients with end-stage renal disease (ESRD), an incipient risk that often materializes before signs of cardiovascular impairment. Kidney transplantation initiates a complex and multiphasic recovery process, in which functional responsiveness is restored before normalization of baseline HRV indices. Methods: Prospective, observational, and cross-sectional studies that used heart rate monitors (such as the Polar H10) and Holter monitoring to collect R-R interval data were reviewed. Analyses included time domain (SDNN, RMSSD), frequency domain (LF, HF), nonlinear parameters (SD1, SD2), and recurrence quantification analysis (RQA). The study populations ranged from kidney transplant recipients compared to healthy donors to longitudinal follow-ups of up to 5 years. Results: Patients with ESRD exhibit substantial autonomic dysfunction, evidenced by a markedly lower HRV than healthy controls in almost all domains (p < 0.001). Surprisingly, HRV may decline further in the first 5 to 7 days after surgery. Significant reductions were observed in SDNN, sample entropy, and total power, indicating that transplantation does not immediately restore autonomic balance and may even exacerbate initial instability due to surgical stress and medications. Findings are conflicting. Some studies report improvements in autonomic regulation and baroreflex sensitivity after 3 to 12 months. However, others indicate that HRV remains inhibited or only partially recovered even after 6 months. There is a positive correlation between a higher estimated glomerular filtration rate (eGFR) and a wider HRV, suggesting that improved graft function directly influences autonomic recovery. Although reduced HRV is an established predictor of sudden cardiac death and mortality in dialysis patients, parameters recorded specifically in the perioperative period have not proven to be effective tools for stratifying the long-term (5-year) risk of cardiac death. Conclusions: Patients with ESRD exhibit severe HRV impairment that persists and may worsen in the immediate post-transplant period. While successful kidney transplantation offers the potential for restoration of physiological homeostasis, normalization of autonomic function is a gradual and individualized process. These findings reinforce the importance of continuous HRV monitoring to assess cardiovascular health and the need for interventions that optimize autonomic recovery in this population.