title: T-wave loop area from a pre-implant 12-lead ECG is associated with appropriate ICD shocks.
abstract: OBJECTIVE
  In implantable cardioverter-defibrillator (ICD) patients, predictors of ICD shocks and mortality are needed to improve patient selection. Electrocardiographic (ECG) markers are simple to obtain and have been demonstrated to predict mortality. We aimed to assess the association of T-wave loop area and circularity with ICD shocks.
  
  
  METHODS
  The study investigated patients with ICDs implanted between 1998 and 2010 for whom digital 12-lead ECGs (Schiller CS200 ECG-Network) of sufficient quality were obtained within 1 month prior to the implantation. T-wave loop area and circularity were calculated. Follow-up data of appropriate shocks were obtained during ICD clinic visits that included reviews of device stored electrograms.
  
  
  RESULTS
  A total of 605 patients (82% males) were included; 68% had ischemic cardiomyopathy and 72% were treated for primary prevention. Over 3.8±1.4 years of follow-up, 114 patients (19%) experienced appropriate shock(s). Those with smaller T-wave loop area received fewer shocks (TLA, hazard ratio, HR, per increase of 1 technical unit, 0.71; [95% confidence interval, 0.53-0.94]; P = 0.02) and those with larger T-wave loop circularity (TLC) representing rounder T wave loop received more shocks (HR per 1% TLC increase 2.96; [0.85-10.36]; P = 0.09). When the quartile containing the largest TLA and TLC values, respectively, were compared to the remaining cases, TLA remained significantly associated with fewer and TLC with more frequent shocks also after multivariate adjustment for clinical variables (HR, 0.59 [0.35-0.99], P = 0.044; and 1.64 [1.08-2.49], P = 0.021, respectively).
  
  
  CONCLUSIONS
  The size and shape of the T-wave loop calculated from pre-implantation 12-lead ECGs are associated with appropriate ICD shocks.
authors.affiliation: Department of Cardiology and Pneumology, Division of Clinical Electrophysiology, University Medical Center Göttingen, Göttingen, Germany.|Department of Internal Medicine II, Division of Cardiology, Section of Electrophysiology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Joachim
authors.identifier: http://orcid.org/0000-0002-5299-2334
authors.initials: J
authors.lastname: Seegers
authors.affiliation: National Heart and Lung Institute, Imperial College, London, United Kingdom.
authors.forename: Katerina
authors.initials: K
authors.lastname: Hnatkova
authors.affiliation: Department of Medical Statistics, University Medical Center Göttingen, Göttingen, Germany.|DZHK (German Centre for Cardiovascular Research), partner site Göttingen, Göttingen, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Friede
authors.affiliation: National Heart and Lung Institute, Imperial College, London, United Kingdom.
authors.forename: Marek
authors.initials: M
authors.lastname: Malik
authors.affiliation: Department of Cardiology and Pneumology, Division of Clinical Electrophysiology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Zabel
mesh_terms: D000368:Aged; D017147:Defibrillators, Implantable / Q000009:adverse effects*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged