Effect of controlled hypoglycaemia on sympathetic skin response in patients with Type 1 diabetes and control subjects.

AIM: To evaluate the quantity and mechanism of sudomotor function during euglycaemia and hypoglycaemia using sympathetic skin responses in patients with Type 1 diabetes and control subjects. METHODS: Sympathetic skin responses were measured in 16 patients with diabetes without neuropathy and in eight control subjects during euglycaemic and hypoglycaemic clamp. RESULTS: During hypoglycaemia, the number of repetitive synchronous sympathetic skin responses significantly increased in both groups (P<0.05), and this increase was significantly associated with the hypoglycaemia and sweating. CONCLUSIONS: During hypoglycaemia the number of repetitive synchronous sympathetic skin responses was related to increased sweating according to the hypoglycaemic symptom score. This is best explained by central nervous system reactions. The sympathetic skin responses of the patients with Type 1 diabetes had a weaker correlation with hypoglycaemia and its symptoms, which was possibly attributable to an adaptation or a dysfunction of the patients' sudomotor pathways.

Effects of controlled hypoglycaemia on cardiac repolarisation in patients with type 1 diabetes.

AIMS/HYPOTHESIS: Nocturnal hypoglycaemia may contribute to sudden death in diabetic patients. However, it is not well known why hypoglycaemia makes these patients prone to death. METHODS: We assessed the effects of controlled hypoglycaemia on cardiac repolarisation using novel electrocardiographic descriptors of T-wave and QRS complex morphology in 16 type 1 diabetic patients and eight healthy counterparts. Several electrocardiographic variables characterising repolarisation were analysed from digitised 12-lead electrocardiograms during a euglycaemic and a hypoglycaemic clamp. RESULTS: Hypoglycaemia did not result in significant changes either in the QT interval corrected for heart rate by the nomogram method or in QT dispersion. However, the morphology of the T-wave changed significantly during hypoglycaemia. The T-wave amplitude and area in precordial leads decreased significantly in both groups (p<0.05 to p<0.001). The spatial QRS-T angle (total cosine R to T) (p<0.05) and the height and the width of the T-wave loop (p<0.05 and p<0.01, respectively) were also reduced in the diabetic patients. The changes in the repolarisation parameters did not exhibit any significant association with changes in catecholamine levels or in heart rate variability in either group. CONCLUSIONS/INTERPRETATION: Hypoglycaemia results in distinct alterations in cardiac repolarisation, which may increase the vulnerability to arrhythmic events.