title: Changes in cardiac repolarisation during spontaneous nocturnal hypoglycaemia in subjects with type 1 diabetes: a preliminary report.
abstract: OBJECTIVE
  Experimental studies have revealed that hypoglycaemia can result in morphological changes in electrocardiographic repolarisation in subjects with type 1 diabetes. However, the influence of spontaneous nocturnal hypoglycaemia on repolarisation morphology in a 'real life' situation is not clear.
  
  
  METHODS
  Adults with type 1 diabetes (n = 11) underwent continuous glucose monitoring with a subcutaneous sensor and digital 12-lead ECG recording for three nights. T-wave morphology was analysed with custom-made software during both hypoglycaemia (glucose <3.5 mmol/l at least 20 min) from ten consecutive heart beats in the middle of the deepest hypoglycaemia and from a control nonhypoglycaemic period (glucose ≥5.0 mmol/l) from the same recording.
  
  
  RESULTS
  In the comparison of 10 hypoglycaemia-control pairs, heart rate (65 ± 12 beats/min during normoglycaemia versus 85 ± 19 beats/min during hypoglycaemia, p = 0.028) increased and the QTcinterval (439 ± 5 vs. 373 ± 5 ms, respectively, p = 0.025) decreased significantly during hypoglycaemia. The spatial QRS-T angle (TCRT) was reduced, and the roughness of the T-wave loop (T-E) increased significantly (p = 0.037 for both) in the patients during hypoglycaemia.
  
  
  CONCLUSIONS
  In adults with type 1 diabetes, spontaneous nocturnal hypoglycaemia results in morphological changes and increased heterogeneity of global cardiac repolarisation. These changes may contribute to the risk of 'dead in bed' syndrome encountered in young individuals with type 1 diabetes.
authors.affiliation: Department of Internal Medicine, Institute of Clinical Medicine, University of Oulu, P.O.Box 5000, Kajaanintie 50, Oulu, Finland. minna.l.koivikko@ppshp.fi.
authors.forename: Minna L
authors.identifier: http://orcid.org/0000-0001-7227-966X
authors.initials: ML
authors.lastname: Koivikko
authors.affiliation: Department of Internal Medicine, Institute of Clinical Medicine, University of Oulu, P.O.Box 5000, Kajaanintie 50, Oulu, Finland.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Kenttä
authors.affiliation: Department of Internal Medicine, Institute of Clinical Medicine, University of Oulu, P.O.Box 5000, Kajaanintie 50, Oulu, Finland.
authors.forename: Pasi I
authors.initials: PI
authors.lastname: Salmela
authors.affiliation: Department of Internal Medicine, Institute of Clinical Medicine, University of Oulu, P.O.Box 5000, Kajaanintie 50, Oulu, Finland.
authors.forename: Heikki V
authors.initials: HV
authors.lastname: Huikuri
authors.affiliation: Department of Internal Medicine, Institute of Clinical Medicine, University of Oulu, P.O.Box 5000, Kajaanintie 50, Oulu, Finland.
authors.forename: Juha S
authors.initials: JS
authors.lastname: Perkiömäki
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D001786:Blood Glucose / Q000502:physiology; D015190:Blood Glucose Self-Monitoring; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007003:Hypoglycemia / Q000139:chemically induced / Q000453:epidemiology / Q000503:physiopathology*; D015994:Incidence; D008297:Male; D010865:Pilot Projects; D055815:Young Adult
chemical_list: D001786:Blood Glucose
keywords: Electrocardiography; Hypoglycaemia; QRS loop; Repolarisation; T-wave loop; Type 1 diabetes