title: ECG predictors of T wave oversensing in subcutaneous implantable cardioverter defibrillators.
abstract: BACKGROUND
  T wave oversensing (TWOS) is the commonest cause of inappropriate shocks in subcutaneous implantable cardioverter defibrillators (S-ICDs). We hypothesise that predictors of TWOS can be derived from surface ECG parameters.
  
  
  METHODS
  In a cohort of SICD recipients in two UK centres, all patients who had TWOS (study group) were compared to all those who had not (control group). The pre-implant screen was scanned and the R wave, T wave amplitudes, QRS interval, time to peak T wave, QT interval and R:T ratio was measured using digital callipers. Logistic regression was performed to identify ECG predictors of TWOS.
  
  
  RESULTS
  One hundred one patients were studied. Six (5.9%) had TWOS. The mean age of the population was 58.6±18years and the median follow-up was 19.5months. By univariate analysis, the predictors of TWOS are QRS duration (140.7±28.7 vs. 105.9±24.6, P=0.007), time to peak T wave (corrected for heart rate, pTc) (403.9±22.6 vs. 347.8±41.4, P=0.006), QTc interval (500.4±41.2 vs. 446.8±49.7, P=0.021), and R:T ratio (3.5±1.1 vs. 9.5±13.2, P=0.034). By multivariate analysis, time to pTc is the most predictive of TWOS. A time to pTc of 390ms cut-off point provided a sensitivity 38.5%, a specificity of 98.9%, a positive predictive value for TWOS of 83.3%, and a negative predictive value of 91.6% (AUC=0.687).
  
  
  CONCLUSIONS
  In this study, time to pTc is the most powerful ECG predictor of TWOS.
authors.affiliation: University Hospital Southampton NHS Foundation Trust, Southampton, England. Electronic address: Drdgwilson@gmail.com.
authors.forename: D G
authors.initials: DG
authors.lastname: Wilson
authors.affiliation: Russells Hall Hospital, The Dudley Group Hospitals NHS Foundation Trust, Dudley, England.
authors.forename: G
authors.initials: G
authors.lastname: Leventigiannis
authors.affiliation: Russells Hall Hospital, The Dudley Group Hospitals NHS Foundation Trust, Dudley, England.
authors.forename: C
authors.initials: C
authors.lastname: Barr
authors.affiliation: University Hospital Southampton NHS Foundation Trust, Southampton, England.
authors.forename: J M
authors.initials: JM
authors.lastname: Morgan
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*; D002648:Child; D015331:Cohort Studies; D017147:Defibrillators, Implantable / Q000009:adverse effects*; D004562:Electrocardiography / Q000379:methods*; D004868:Equipment Failure; D005260:Female; D005500:Follow-Up Studies; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D040521:Subcutaneous Tissue
keywords: Electrocardiogram; Inappropriate shock; Predictors; Subcutaneous implantable cardioverter defibrillator; T wave oversensing