title: Effectiveness of subcutaneous implantable cardioverter-defibrillators and determinants of inappropriate shock delivery.
abstract: OBJECTIVE
  Assess subcutaneous implantable cardioverter-defibrillator (S-ICD) effectiveness in the prevention of sudden cardiac death and the impact of demographics and the initial detection algorithm in the delivery of inappropriate shocks (safety).
  
  
  METHODS
  Real world prospective registry in which we assessed 54 patients (40±17years old, 85% males) who underwent S-ICD implantation for primary or secondary prevention of SCD. Safety and efficacy outcomes were defined as the delivery of inappropriate shocks and the prevention of sudden cardiac death, respectively. Tiered-therapy S-ICD had at least two programmed zones, determined by the longest RR interval.
  
  
  RESULTS
  During a mean follow-up of 2.6±1.9years, 6 patients (11%) died, none due to sudden cardiac death. Six patients (11%) received appropriate therapies, irrespectively of the established detection algorithm (p=0.59). All ventricular tachycardia and fibrillation episodes were adequately treated. Nine patients (17%) had inappropriate shocks: 6 without tiered-therapy vs 3 with previously programmed tiered-therapy (p=0.001). The yearly rate of inappropriate shocks was 17%/year with single zone detection vs 4%/year with tiered-therapy programming (p=0.007). Single-zone detection programming was an independent predictor of inappropriate shock delivery (HR 1.49, IC 95%: 1.05-18.80, p=0.04).
  
  
  CONCLUSIONS
  In this selected population of patients, the S-ICDs proved effective in preventing sudden cardiac death. Tiered-therapy was independently associated with a lower rate of inappropriate shock delivery.
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal. Electronic address: johnpvm@gmail.com.
authors.forename: João
authors.initials: J
authors.lastname: Mesquita
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Diogo
authors.initials: D
authors.lastname: Cavaco
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Ferreira
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Nicodemus
authors.initials: N
authors.lastname: Lopes
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Pedro G
authors.initials: PG
authors.lastname: Santos
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Maria S
authors.initials: MS
authors.lastname: Carvalho
authors.affiliation: Hospital de Santa Cruz, Anaesthesiology Department, Lisbon, Portugal.
authors.forename: Andreia
authors.initials: A
authors.lastname: Haas
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Francisco
authors.initials: F
authors.lastname: Costa
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Carmo
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Francisco
authors.initials: F
authors.lastname: Morgado
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Adragão
authors.affiliation: Hospital de Santa Cruz, Cardiology Department, Lisbon, Portugal.
authors.forename: Miguel
authors.initials: M
authors.lastname: Mendes
mesh_terms: D000328:Adult; D000465:Algorithms; D016757:Death, Sudden, Cardiac / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011322:Primary Prevention / Q000379:methods*; D011446:Prospective Studies; D012042:Registries; D012307:Risk Factors; D055502:Secondary Prevention / Q000379:methods*; D017180:Tachycardia, Ventricular / Q000150:complications / Q000401:mortality / Q000628:therapy*; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
keywords: Defibrillator; Subcutaneous implantable cardioverter-defibrillator; Sudden cardiac death; Ventricular arrhythmia