title: Which patients are not suitable for a subcutaneous ICD: incidence and predictors of failed QRS-T-wave morphology screening.
abstract: BACKGROUND
  The subcutaneous cardioverter-defibrillator (S-ICD) relies on a pre-implantation QRS-T morphology screening (TMS) of the ECG to assure that it reliably detects the QRS complexes and T waves. The prevalence and clinical characteristics of the patients who fail this TMS is unknown.
  
  
  RESULTS
  QRS-TMS was done in 230 consecutive ICD outpatients (75% male, age 57 ± 15 years) without an indication for cardiac pacing, using an ECG simulating the 3 sensing vectors of the S-ICD (TMS-ECG). Patients were defined suitable when at least 1 sensing vector was considered appropriate in both supine and standing position. In total, 7.4% of patients, who were all male, were considered not suitable for a S-ICD according to the TMS-ECG. Independent predictors for TMS failure were hypertrophic cardiomyopathy (HCM; odds ratio [OR] 12.6), a heavy weight (OR 1.5), a prolonged QRS duration (OR 1.5) and a R:T ratio <3 in the lead with the largest T wave on a standard 12-lead surface ECG (OR 14.6).
  
  
  CONCLUSIONS
  In patients without an indication for pacing, 7.4% would have been not suitable for a S-ICD according to the TMS. HCM, a heavy weight, a prolonged QRS duration and a R:T ratio <3 in the ECG lead with the largest T wave were independently associated with TMS failure. These data might alert physicians that selection of patients for a S-ICD should be considered with special caution in certain patient groups, because they may not satisfy ECG criteria for adequate sensing.
authors: Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands.
authors: Louise R A
authors: LRA
authors: Olde Nordkamp
authors: Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands.
authors: Joppe L F
authors: JLF
authors: Warnaars
authors: Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands.
authors: Kirsten M
authors: KM
authors: Kooiman
authors: Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands.
authors: Joris R
authors: JR
authors: de Groot
authors: Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands.
authors: Boudewijn R A M
authors: BRAM
authors: Rosenmöller
authors: Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands.
authors: Arthur A M
authors: AAM
authors: Wilde
authors: Department of Cardiology, Academic Medical Center, Amsterdam, the Netherlands.
authors: Reinoud E
authors: RE
authors: Knops
mesh_terms: D000200:Action Potentials; D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D016757:Death, Sudden, Cardiac / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D056888:Patient Positioning; D018579:Patient Selection; D011237:Predictive Value of Tests; D012307:Risk Factors; D016683:Supine Position
keywords: ICD sensing; implantable cardioverter defibrillator; subcutaneous ICD; sudden cardiac death; ventricular tachycardia