[Sympathetic skin responses and variability of the R-R interval: correlation with the severity stages of diabetic...

The sympathetic skin responses (SSR) and the variations of the R-R interval of the electrocardiogram (the difference between the maximum and minimum heart rates at rest, the ratio between the maximum and minimum heart rates during the Valsalva manoeuvre or Valsalva ratio, and during an active orthostatic test or orthostatic ratio) have been measured in 32 control subjects and 53 diabetic patients. These latter ones were classified according to the existence and the increasing severity of a polyneuropathy (PNP) into 4 grades (0 to III) based on Dyck's classification modified depending on the presence or the absence of cutaneous impairments in grade II. There was an important inter-individual variability for SSR as well as R-R interval results, in the control group. In the absence of PNP, the vegetative tests showed normal values. These tests were severely degraded in the diabetic patients with a PNP grade III, ov even could not be performed. The SSR amplitude was decreased in all diabetic patients. In the presence of clinical signs of dysautonomia, the SSR amplitude, the heart rate variability at rest and the orthostatic ratio were significantly different from those of the control subjects. The presence of trophic disorders appearing at PNP grade II did not significantly modify the results of the tests. Although they did not allow any differentiation of the PNP intermediary grades. SSR and R-R intervals are of interest in appreciating the infra-clinical existence and the importance of the neurovegetative disorders occurring during diabetic polyneuropathies.