RESUMO
INTRODUCTION: A dysfunctional autonomic nervous system (ANS) has also been recognized as an important mechanism contributing to the poor outcome in CKD patients, with several studies reporting a reduction in heart rate variability (HRV). OBJECTIVE: Evaluate the sympathovagal balance in patients with chronic kidney disease on conservative treatment. METHODS: In a cross-sectional study, patients with CKD stages 3, 4 and 5 not yet on dialysis (CKD group) and age-matched healthy subjects (CON group) underwent continuous heart rate recording during two twenty-minute periods in the supine position (pre-inclined), followed by passive postural inclination at 70° (inclined period). Power spectral analysis of the heart rate variability was used to assess the normalized low frequency (LFnu), indicative of sympathetic activity, and the normalized high frequency (HFnu), indicative of parasympathetic activity. The LFnu/HFnu ratio represented sympathovagal balance. RESULTS: After tilting, CKD patients had lower sympathetic activity, higher parasympathetic activity, and lower sympathovagal balance than patients in the CON group. Compared to patients in stage 3, patients in stage 5 had a lower LFnu/HFnu ratio, suggesting a more pronounced impairment of sympathovagal balance as the disease progresses. CONCLUSION: CKD patients not yet on dialysis have reduced HRV, indicating cardiac autonomic dysfunction early in the course of CKD.