The natural history of recently diagnosed autonomic neuropathy over a period of 2 years

Background: Patients with diabetic autonomic neuropathy (DAN) have an incre ased cardiovascular mortality rate compared with normals or diabetic patien ts without DAN. Indices of standard cardiovascular autonomic function tests and heart rate variability (HRV) are reliable markers of the presence and severity of DAN. Objective: The present prospective study investigated the natural history of values of HRV indices and cardiovascular reflex tests in patients with recently diagnosed asymptomatic DAN, over a period of 2 year s, at 3 month intervals. Patients and methods: A total of 30 consecutive pa tients (nine men and 21 women), of median age 51 (range 25-65) years, eight with type 1 and 22 with Type 2 diabetes mellitus, were included in the stu dy, at the time that the presence of DAN was confirmed, as this was establi shed if at least two of cardiovascular autonomic function tests became abno rmal. The expiration/inspiration (E/I) ratio, S.D. and mean circular result ant of R-I;I intervals, the Valsalva index, the 30:15 ratio, and the blood pressure response to standing as well as normalised spectral power indices of HRV were used. Results: All measured indices, except the Valsalva index, deteriorated in all 30 patients during the 2 year follow-up. Most of HRV i ndices values deteriorated significantly in comparison to baseline at month 12, while the values of cardiovascular reflex tests displayed significant deterioration, in comparison to baseline, between months 15 and 21. Fourtee n patients developed symptoms of DAN during the 2 year period. Patients wit h better glycemic control exhibited deterioration of DAN markers at the sam e time period with those with poor glycemic control. Conclusions: Our data suggest that the progression of DAN is significant during the 2 years subse quent to its discovery. This was defined by the deterioration of the mean v alues of HRV indices and standard cardiovascular autonomic function tests, and by the development of autonomic symptoms in some patients. HRV indices are the earlier markers of DAN deterioration. (C) 1998 Elsevier Science Ire land Ltd. All rights reserved.