title: Shock efficacy of subcutaneous implantable cardioverter-defibrillator for prevention of sudden cardiac death: initial multicenter experience.
abstract: BACKGROUND
  Recently, subcutaneous implantable cardioverter-defibrillator (S-ICD) has become available. The aim of our study was to assess the efficacy of S-ICD in a clinical setting.
  
  
  RESULTS
  Between June 2010 and July 2011, 40 consecutive patients (42 ± 15 years; body mass index, 27 ± 6 kg/m(2); left ventricular ejection fraction, 47 ± 15%; 28 men) received an S-ICD for primary (n=17) or secondary prevention (n=23 [58%]) at 3 institutions in Germany. Intraoperative defibrillation efficacy testing failed in 1 patient with severely reduced left ventricular ejection fraction; testing was effective in all other patients. All episodes stored in the S-ICD were analyzed for appropriate and inappropriate detection, as well as effective shock delivery to convert ventricular tachyarrhythmia into sinus rhythm. During a median follow-up of 229 (interquartile range, 116-305) days, 4 patients experienced 21 episodes, with correct detection of ventricular tachyarrhythmia and subsequent shock therapy. A total of 28 shocks were delivered in these 4 patients. Mixed logistic regression modeling revealed a shock efficacy of 96.4% (95% CI, 12.8%-100%). The efficacy of first shocks, however, was only 57.9% (95% CI, 35.6%-77.4%). Four episodes were incorrectly classified as ventricular tachyarrhythmia, which led to inappropriate shock delivery in 2 patients.
  
  
  CONCLUSIONS
  Ineffective shock delivery may occur in patients with S-ICD, even after successful intraoperative testing. Multicenter trials are required with close monitoring of safety and efficacy end points to identify patients who may be at risk for shock failure.
authors.affiliation: Department of Electrophysiology, University Heart Center, Hamburg, Germany. aydin@uke.de
authors.forename: Ali
authors.initials: A
authors.lastname: Aydin
authors.forename: Friederike
authors.initials: F
authors.lastname: Hartel
authors.forename: Michael
authors.initials: M
authors.lastname: Schlüter
authors.forename: Christian
authors.initials: C
authors.lastname: Butter
authors.forename: Julia
authors.initials: J
authors.lastname: Köbe
authors.forename: Martin
authors.initials: M
authors.lastname: Seifert
authors.forename: Nils
authors.initials: N
authors.lastname: Gosau
authors.forename: Boris
authors.initials: B
authors.lastname: Hoffmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Hoffmann
authors.forename: Eik
authors.initials: E
authors.lastname: Vettorazzi
authors.forename: Iris
authors.initials: I
authors.lastname: Wilke
authors.forename: Karl
authors.initials: K
authors.lastname: Wegscheider
authors.forename: Hermann
authors.initials: H
authors.lastname: Reichenspurner
authors.forename: Lars
authors.initials: L
authors.lastname: Eckardt
authors.forename: Daniel
authors.initials: D
authors.lastname: Steven
authors.forename: Stephan
authors.initials: S
authors.lastname: Willems
mesh_terms: D000328:Adult; D000368:Aged; D016757:Death, Sudden, Cardiac / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D004452:Echocardiography; D005260:Female; D005500:Follow-Up Studies; D005858:Germany; D006801:Humans; D016015:Logistic Models; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011322:Primary Prevention; D055502:Secondary Prevention; D013318:Stroke Volume; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome