title: Diurnal Differences in Risk of Cardiac Arrhythmias During Spontaneous Hypoglycemia in Young People With Type 1 Diabetes.
abstract: Hypoglycemia may exert proarrhythmogenic effects on the heart via sympathoadrenal stimulation and hypokalemia. Hypoglycemia-induced cardiac dysrhythmias are linked to the "dead-in-bed syndrome," a rare but devastating condition. We examined the effect of nocturnal and daytime clinical hypoglycemia on electrocardiogram (ECG) in young people with type 1 diabetes.
  
  
  
  Thirty-seven individuals with type 1 diabetes underwent 96 h of simultaneous ambulatory ECG and blinded continuous interstitial glucose monitoring (CGM) while symptomatic hypoglycemia was recorded. Frequency of arrhythmias, heart rate variability, and cardiac repolarization were measured during hypoglycemia and compared with time-matched euglycemia during night and day.
  
  
  
  A total of 2,395 h of simultaneous ECG and CGM recordings were obtained; 159 h were designated hypoglycemia and 1,355 h euglycemia. A median duration of nocturnal hypoglycemia of 60 min (interquartile range 40-135) was longer than daytime hypoglycemia of 44 min (30-70) (P= 0.020). Only 24.1% of nocturnal and 51.0% of daytime episodes were symptomatic. Bradycardia was more frequent during nocturnal hypoglycemia compared with matched euglycemia (incident rate ratio [IRR] 6.44 [95% CI 6.26, 6.63],P< 0.001). During daytime hypoglycemia, bradycardia was less frequent (IRR 0.023 [95% CI 0.002, 0.26],P= 0.002) and atrial ectopics more frequent (IRR 2.29 [95% CI 1.19, 4.39],P= 0.013). Prolonged QTc, T-peak to T-end interval duration, and decreased T-wave symmetry were detected during nocturnal and daytime hypoglycemia.
  
  
  
  Asymptomatic hypoglycemia was common. We identified differences in arrhythmic risk and cardiac repolarization during nocturnal versus daytime hypoglycemia in young adults with type 1 diabetes. Our data provide further evidence that hypoglycemia is proarrhythmogenic.
authors.affiliation: Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.|Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.
authors.forename: Peter
authors.initials: P
authors.lastname: Novodvorsky
authors.affiliation: Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.|INSIGNEO Institute for in silico Medicine, University of Sheffield, Sheffield, U.K.
authors.forename: Alan
authors.initials: A
authors.lastname: Bernjak
authors.affiliation: Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.|Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, U.K.
authors.forename: Elaine
authors.initials: E
authors.lastname: Chow
authors.affiliation: Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.|Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.|Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, U.K.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Iqbal
authors.affiliation: Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.|Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.
authors.forename: Lianne
authors.initials: L
authors.lastname: Sellors
authors.affiliation: Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.|Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.
authors.forename: Scott
authors.initials: S
authors.lastname: Williams
authors.affiliation: Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.|Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Fawdry
authors.affiliation: Department of Biomedical Science, University of Sheffield, Sheffield, U.K.
authors.forename: Bhavin
authors.initials: B
authors.lastname: Parekh
authors.affiliation: School of Health and Related Research, University of Sheffield, Sheffield, U.K.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Jacques
authors.affiliation: Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K.
authors.forename: Jefferson L B
authors.initials: JLB
authors.lastname: Marques
authors.affiliation: Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.|Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, U.K.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Sheridan
authors.affiliation: Department of Oncology and Metabolism, University of Sheffield, Sheffield, U.K. s.heller@sheffield.ac.uk.|Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, U.K.
authors.forename: Simon R
authors.identifier: 0000-0002-2425-9565
authors.initials: SR
authors.lastname: Heller
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000209:etiology* / Q000503:physiopathology; D002940:Circadian Rhythm / Q000502:physiology*; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007003:Hypoglycemia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D012307:Risk Factors