title: Heart rate variability is decreased in chronic kidney disease but may improve with hemoglobin normalization.
abstract: BACKGROUND
  Cardiac autonomic function can be measured by heart rate variability (HRV). Dialysis patients have an abnormally low HRV and are at increased risk for sudden death. A reduction in HRV is associated with anemia. HRV was therefore measured in patients with chronic kidney disease (CKD) after hemoglobin normalization.
  
  
  METHODS
  Sixteen nondiabetic patients with CKD stage 4 (glomerular filtration rate 23.7 +/- 13.9 ml/min) and renal anemia received epoetin aiming at a hemoglobin level of 135-150 g/L. HRV was measured by 24-hour Holter electrocardiogram at baseline and after hemoglobin normalization and in a reference group consisting of 16 volunteers without impairment of renal function.
  
  
  RESULTS
  Hemoglobin level increased from 100.7 +/- 12.6 g/L to 142.4 +/- 7.2 g/L during the study. At baseline, HRV measured in the time domain as the standard deviation of all normal RR intervals in the entire 24-hour electrocardiogram (SDNN) was 116.3 +/- 39.2 ms compared with 147.5 +/- 27.2 ms in the reference group (p<0.05). The frequency domain measures low-frequency power and total power were 367.7 +/- 350.2 ms2 and 1,368.9 +/- 957.4 ms2 compared with 717.3 +/- 484.5 ms2 and 2,228.3 +/- 1142.4 ms2 (p<0.05) in the reference group. After hemoglobin normalization there was an increase in low-frequency power to 498.3 +/- 432.7 ms2 (p<0.05) and in total power to 1,731.0 +/- 1,069.4 ms2 (p<0.05) while SDNN remained at 120.9 +/- 33.8 ms (p=ns).
  
  
  CONCLUSIONS
  CKD patients not yet on dialysis had a reduced HRV, indicating impaired autonomic function, compared with a reference group without impaired renal function. Hemoglobin normalization improved but did not fully normalize HRV. The clinical significance of this deserves further investigation.
authors.affiliation: Department of Medical Sciences, University Hospital, Uppsala, Sweden. hans.furuland@medsci.uu.se
authors.forename: Hans
authors.initials: H
authors.lastname: Furuland
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Linde
authors.forename: Anders
authors.initials: A
authors.lastname: Englund
authors.forename: Björn
authors.initials: B
authors.lastname: Wikström
mesh_terms: D000328:Adult; D000368:Aged; D000740:Anemia / Q000503:physiopathology; D001794:Blood Pressure; D002908:Chronic Disease; D005260:Female; D006339:Heart Rate; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged
chemical_list: D006454:Hemoglobins