Diabetes Care, Vol 23, Issue 11 1686-1693, Copyright © 2000 by American Diabetes Association
Predictors of abnormal cardiovascular autonomic function measured by frequence domain analysis of heart rate variability and conventional tests in patients with type 1 diabetes
S Makimattila, A Schlenzka, M Mantysaari, R Bergholm, P Summanen, P Saar, H Erkkila and H Yki-Jarvinen
Department of Medicine, Helsinki University Central Hospital, Finland.
OBJECTIVE: Frequency domain analysis of heart rate variability (HRV) is
used to assess cardiovascular autonomic function. There are no prospective
data on the sensitivity of its various components to glycemia or other
diabetes-related risk factors compared with conventional tests and with
other complications of diabetes. RESEARCH DESIGN AND METHODS: In 1985,
possible risk factors of future complications were determined in 115
children with type 1 diabetes. In 1996, the presence of complications (HRV
analysis, conventional tests of autonomic function, urinary albumin
excretion rate [UAER], and retinopathy) were assessed in 83 of these
patients (age 32 +/- 1 years, duration of diabetes 22 +/- 1 years).
RESULTS: Poor glycemic control (measured as lifetime glycemic exposure or
HbA1c in 1985) was the most important independent predictor of decreases in
all measures of absolute power of HRV (total power [TP] and very low
frequency, low frequency [LF], and high frequency [HF] power) and square
root of the mean square of R-R interval differences but not of changes of
normalized measures or ratios (normalized HF and LF LF/HF). Other
significant independent predictors of autonomic dysfunction were late age
of onset of diabetes, female sex, and high BMI. To examine the sensitivity
of the various tests to glycemia, the patients were divided into tertiles
based on lifetime glycemic exposure (A1c months). Glycemic exposure in the
tertiles averaged 194 +/- 25 A1c months (20 years of HbA1c 0.8% above
normal), 556 +/- 19 A1c months(20 years of HbA1c 2.3% above normal), and
963 +/- 30 A1c months (20 years of HbA1c 4% above normal). Tests of
complications that were significantly abnormal in patients already in the
lowest tertile and were correlated with glycemia were TP and severity of
retinopathy. Of conventional tests, only the ratio of length of R-R
intervals during expiration to inspiration (E/I ratio) was significantly
related to glycemic exposure, but it required high glycemic exposure (20
years of HbA1c 4% above normal) to be abnormal. UAER was significantly
increased only in the highest tertile of glycemic exposure. CONCLUSIONS: TP
and retinopathy score were much more sensitive to antecedent glycemia than
conventional tests of autonomic function or UAER and were significantly
abnormal in patients exposed to approximately 20 years' duration of an
HbA1c 0.8% above normal.