Effects of controlled hypoglycaemia on cardiac repolarisation in patients with type 1 diabetes.
OBJECTIVE
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
Hypoglycaemia results in distinct alterations in cardiac repolarisation, which may increase the vulnerability to arrhythmic events.
Koivikko
M L
ML
Department of Internal Medicine, University of Oulu, P.O. Box 5000, (Kajaanintie 50), 90014 Oulu, Finland.
Karsikas
M
M
Salmela
P I
PI
Tapanainen
J S
JS
Ruokonen
A
A
Seppänen
T
T
Huikuri
H V
HV
Perkiömäki
J S
JS
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D001786:Blood Glucose / Q000378:metabolism; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000503:physiopathology*; D004562:Electrocardiography; D004837:Epinephrine / Q000097:blood; D005260:Female; D015309:Glucose Clamp Technique; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D007003:Hypoglycemia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D011188:Potassium / Q000097:blood
D001786:Blood Glucose; D011188:Potassium; D009638:Norepinephrine; D004837:Epinephrine