Impaired 0.1-Hz vasomotion assessed by laser Doppler anemometry as an early index of peripheral sympathetic neuropathy in diabetes.

Impairment of 0.1-Hz vasomotion, which was found in diabetic patients, was suggested to be an early index of sympathetic dysfunction. We studied the relationships between alterations in vasomotion and both cardiac autonomic and sensory neuropathy. Twenty type 1 and 22 type 2 diabetic patients were investigated. Vasomotion was recorded in single capillaries at the dorsal middle phalangeal area of the left ring finger by means of laser Doppler anemometry. Cardiac autonomic neuropathy was assessed by spectral analysis of heart rate variation during rest and recording heart rate responses to deep breathing and Valsalva manoeuvre. Sensory neuropathy was investigated by measuring heat pain, vibration, and thermal sensory thresholds. Impaired vasomotion was more often (82.4%) found in diabetic patients with at least one altered cardiac autonomic test, but also in 47.1% of those with all of these tests being normal (P = 0.035). Both heart rate variation coefficient during rest (r = 0.40, P = 0.045) and Valsalva ratio (r = 0.41, P = 0.037) correlated positively with amplitudes of vasomotion in type 1 diabetic patients. The prevalence of impaired vasomotion was not higher in patients with sensory neuropathy compared to those with normal sensory functions. A disturbed warm sensation was only found in 2 patients and none had an abnormal heat pain threshold. Our data indicate that impairment of 0.1-Hz vasomotion precedes parasympathetic neuropathy, assessed by heart rate variation tests, and abnormalities in warm and heat pain sensation. Reduction of arteriolar vasomotion, detected by laser Doppler anemometry, might be an early index of sympathetic dysfunction, because it correlates with disturbances in those cardiac autonomic tests, which are at least in part under sympathetic control.