title: Quantitative assessment of the effects of therapeutic hypothermia on early repolarization in idiopathic ventricular fibrillation survivors: a 7-year cohort study.
abstract: BACKGROUND
  The early repolarization (ER) pattern on ECG is associated with an increased risk of idiopathic ventricular fibrillation (ID-VF). Hypothermia is known to result in similar electrocardiographic changes. In this retrospective cohort study, we examine the impact of therapeutic hypothermia on ER in survivors of cardiac arrest attributed to ID-VF and draw comparisons with a control group who experienced coronary artery disease-related VF (CAD-VF).
  
  
  RESULTS
  All patients who had cardiac arrest and were treated with therapeutic hypothermia over a 7-year period were considered for inclusion in the study. Forty-three patients were identified with ID-VF or CAD-VF arrest. ECGs were obtained during cooling and again after rewarming. ECGs were digitized and assessed for the presence of ER by 2 independent observers. Cooling significantly increased the prevalence (74% during cooling versus 51% at baseline temperature; P=0.044) and mean amplitude (0.78±0.10 mV during cooling versus 0.56±0.09 mV at baseline temperature; P=0.038) of ER in the overall cohort. During cooling, ER was more common among survivors of ID-VF than of CAD-VF (100% versus 67%; P=0.043). ER magnitude was significantly greater among ID-VF survivors than CAD-VF survivors both during cooling (1.16±0.18 versus 0.70±0.11 mV; P=0.044) and at baseline temperature (1.02±0.21 versus 0.42±0.09 mV; P=0.005).
  
  
  CONCLUSIONS
  Hypothermia increases both the prevalence and magnitude of ER in cardiac arrest survivors. Despite the association of ER with ID-VF, therapeutic hypothermia only increases ER amplitude in CAD-VF survivors.
authors.affiliation: Division of Imaging Sciences and Biomedical Imaging, King's College London, United Kingdom.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Williams
authors.forename: Ian
authors.initials: I
authors.lastname: Sabir
authors.forename: Camus
authors.initials: C
authors.lastname: Nimmo
authors.forename: Nick
authors.initials: N
authors.lastname: Linton
authors.forename: Frederic A
authors.initials: FA
authors.lastname: Sebag
authors.forename: James L
authors.initials: JL
authors.lastname: Harrison
authors.forename: Matthew
authors.initials: M
authors.lastname: Wright
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Barrett
authors.forename: Manu
authors.initials: M
authors.lastname: Shankar-Hari
authors.forename: Mark D
authors.initials: MD
authors.lastname: O'Neill
mesh_terms: D000200:Action Potentials; D000328:Adult; D003324:Coronary Artery Disease / Q000150:complications; D004562:Electrocardiography; D005260:Female; D006323:Heart Arrest / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D007036:Hypothermia, Induced / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted; D017741:Survivors; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*
keywords: arrhythmias, cardiac; death, sudden, cardiac; hypothermia; paroxysmal ventricular fibrillation; ventricular fibrillation