Detection of autonomic sympathetic dysfunction in diabetic patients - A study using laser Doppler imaging

OBJECTIVE - To study signs of the disturbed reflex autonomic sympathetic nerve function in type 1 and type 2 diabetic patients. RESEARCH DESIGN AND METHODS - Measurements were made on 15 type 1 (duration 13-32 years) and on 50 recently diagnosed type 2 diabetic patients (duration 3-4 years). The vasoconstrictor responses in the distal phalanx of the middle finger (locally heated to 40 degrees C) to the cooling of the contralateral arm were measured using Laser Doppler Imaging (LDI). A vasoconstriction index (VAC) was calculated taking age into account and was compared with reference values obtained in 80 control subjects. The diabetic patients were also studied with deep-breathing tests (i.e., the heart-rate variation expressed as the expiration-to inspiration [E/I] ratio, a lest of parasympathetic nerve function). RESULTS - The vasoconstrictor responses to indirect cooling (VAC) were significantly reduced in the fingers of the diabetic patients, both type 2 (0.77 +/- 0.02 V; P < 0.01) and type 1 (0.83 +/- 0.03 V; P < 0.001), compared with the healthy control subjects (0.65 +/- 0.01); the age-corrected VAC (VAC(z)) was slightly more impaired in type 1 than in type 2 diabetic patients. The frequency of an abnormal VAC(z) corresponded well to the frequency of an abnormal E/I ratio in type 1 diabetic patients (similar to 50%), whereas the frequency of an abnormal VAC(z) was significantly higher than an abnormal E/I ratio among type Z diabetic patients (11/50 vs. 4/50; P < 0.05). CONCLUSIONS - Both type 1 and type 2 diabetic patients have impaired cutaneous blood flow regulation. The VAC index seems to be a promising tool for detection of subclinical changes in autonomic sympathetic function.