TIME AND FREQUENCY-DOMAIN ESTIMATES OF SPONTANEOUS BAROREFLEX SENSITIVITY PROVIDE EARLY DETECTION OF AUTONOMIC DYSFUNCTION IN DIABETES-MELLITUS

Diabetic autonomic dysfunction is associated with a high risk of morta lity which makes its early identification clinically important. The ai m of our study was to compare the detection of autonomic dysfunction p rovided by classical laboratory autonomic function tests with that obt ained through computer assessment of the spontaneous sensitivity of th e baroreceptor-heart rate reflex (BRS) by lime domain and frequency do main techniques. In 20 normotensive diabetic patients (mean age +/-SD 41.9 +/- 8.1 years) with no evidence of autonomic dysfunction on labor atory autonomic testing (DO) blood pressure (BP) and ECG were continuo usly monitored over 15 min in the supine position, SRS was assessed as the slope of the regression line between spontaneous increases or red uctions in systolic BP and linearly related lengthening or shortening in RR interval over sequences of al feast 4 consecutive beats (sequenc e method), or as the squared ratio between RR interval and systolic BP spectral powers around 0.1 Hz. We compared the results with those of 32 age-matched normotensive diabetic patients with abnormal autonomic function tests (D1) and with those of 24 healthy age-matched control s ubjects with normal autonomic function tests (C). Compared to C, BRS w as markedly less in D1 when assessed by both the slope of the two type s of sequences (data pooled) and by the spectral method (-71.3 % and - 60.2 % respectively, both p < 0.01). However, BRS was consistently alt hough somewhat less markedly reduced in DO, the reduction being clearl y evident for all the estimates (-57.0 % and -43.5 %, both p < 0.01). The effects were more evident than those obtained by the simple quanti fication of the RR interval variability. These dal-a suggest that time and frequency domain estimates of spontaneous BRS allow earlier detec tion of diabetic autonomic dysfunction than classical laboratory auton omic tests. The estimates can be obtained by short non-invasive record ing of the BP and RR interval signals in the supine patient, i.e. unde r conditions suitable for routine outpatient evaluation.