title: Etiology and Programming Effects on Shock Efficacy in ICD Recipients.
abstract: BACKGROUND
  We sought to assess the efficacy of high-energy shocks to restore rhythm and predictors of success in patients with sustained ventricular arrhythmias and implantable cardioverter defibrillator (ICD).
  
  
  RESULTS
  Data from 162 patients included in the UMBRELLA study that experienced one or more episodes of ventricular tachycardia (VT) for which ICD shocks of at least 30 Joules were delivered (appropriate high-energy shocks) were analyzed. In total, 456 ventricular arrhythmia episodes were registered. Forty four episodes (9.6%) from 39 patients (24%) had at least one ineffective high-energy shock delivered. Hypertrophic cardiomyopathy was more frequent among patients with unsuccessful shocks (10.3% vs 2.4%). Patients with ineffective shocks had higher proportion of sustained monomorphic ventricular arrhythmias (86.4%; the other 13.6% were sustained polymorphic and ventricular fibrillation [VF]) compared with patients with all their shocks effective (62.9%, P = 0.02). No statistical differences were found between groups in time from detection to the high-energy shock delivery, in tachycardia cycle length, or in antitachycardia pacing, but patients with ineffective high-energy shocks had higher proportion of previously ineffective low-energy shock (9.1% vs 0.5%, P = 0.01).
  
  
  CONCLUSIONS
  We found a substantial rate of ineffective high-energy shocks for the treatment of VT or VF in patients with ICD. High-energy shock efficacy seems to be reduced by hypertrophic cardiomyopathy and by the administration of previous low-energy shocks.
authors.affiliation: Hospital Universitario de San Juan, Universidad Miguel Hernandez, Alicante, Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Bertomeu-González
authors.affiliation: Hospital Universitario de San Juan, Universidad Miguel Hernandez, Alicante, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Moreno-Arribas
authors.affiliation: Hospital Universitario de San Juan, Universidad Miguel Hernandez, Alicante, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Castillo-Castillo
authors.affiliation: Hospital Universitario Araba, Vitoria-Gasteiz, Álava, España.
authors.forename: José
authors.initials: J
authors.lastname: Martínez-Ferrer
authors.affiliation: Hospital Santa Creu i Sant Pau, Barcelona, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Viñolas
authors.affiliation: Hospital Universitario de Canarias, Santa Cruz de Tenerife, Spain.
authors.forename: Aníbal
authors.initials: A
authors.lastname: Rodríguez
authors.affiliation: Hospital Universitario Virgen Macarena, Sevilla, Spain.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Díaz-Infante
authors.affiliation: Hospital Universitario Puerta de Hierro, Madrid, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Fernández-Lozano
authors.affiliation: Hospital Clínico Universitario Virgen de la Victoria, Málaga, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Alzueta
authors.affiliation: Hospital Universitario 12 de Octubre, Madrid, Spain.
authors.forename: Adolfo
authors.initials: A
authors.lastname: Fontenla
mesh_terms: D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013030:Spain / Q000453:epidemiology; D015996:Survival Rate; D017180:Tachycardia, Ventricular / Q000401:mortality* / Q000517:prevention & control*; D013813:Therapy, Computer-Assisted / Q000379:methods / Q000706:statistics & numerical data*; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000401:mortality* / Q000517:prevention & control*
keywords: electric defibrillation; high-energy shock; implantable cardioverter defibrillator; ventricular fibrillation; ventricular tachycardia