title: The effect of duration of follow-up and presence of competing risk on lifespan-gain from implantable cardioverter defibrillator therapy: who benefits the most?
abstract: BACKGROUND
  In at-risk patients with left ventricular dysfunction, implantable cardioverter defibrillators (ICDs) prolong life. Implantable cardioverter defibrillators are increasingly implanted for primary prevention and therefore into lower risk patients. Trial data have demonstrated the benefit of these devices but does not provide an estimate of potential lifespan-gain over longer time periods, e.g. a patient's lifespan.
  
  
  METHODS
  Using data from landmark ICD trials, lifespan-gain was plotted against baseline annual mortality in the individual trials. Lifespan-gain was then extrapolated to a time-horizon of >20 years while adjusting for increasing 'competing' risk from ageing and non-sudden cardiac death (pump failure).
  
  
  RESULTS
  At 3 years, directly observed lifespan-gain was strongly dependent on baseline event rate (r = 0.94, P < 0.001). However, projecting beyond the duration of the trial, lifespan-gain increases rapidly and non-linearly with time. At 3 years, it averages 1.7 months, but by 10 years up to 9-fold more. Lifespan-gain over time horizons >20 years were greatest in lower risk patients (∼5 life-years for 5% baseline mortality, ∼2 life-years for 15% baseline mortality). Increased competing risks significantly reduce lifespan-gain from ICD implantation.
  
  
  CONCLUSIONS
  While high-risk patients may show the greatest short-term gain, the dramatic growth of lifespan-gain over time means that it is the lower risk patients, e.g. primary prevention ICD implantation, who gain the most life-years over their lifetime. Benefit is underestimated when only trial data are assessed as trials can only maintain randomization over limited periods. Lifespan-gain may be further increased through advances in ICD device programming.
authors.affiliation: International Centre for Circulatory Health, National Heart Lung Institute, Imperial College, St. Mary's Hospital, London W2 1LA, UK claire.raphael@gmail.com z.whinnett@imperial.ac.uk.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Raphael
authors.affiliation: International Centre for Circulatory Health, National Heart Lung Institute, Imperial College, St. Mary's Hospital, London W2 1LA, UK.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Finegold
authors.affiliation: International Centre for Circulatory Health, National Heart Lung Institute, Imperial College, St. Mary's Hospital, London W2 1LA, UK.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Barron
authors.affiliation: International Centre for Circulatory Health, National Heart Lung Institute, Imperial College, St. Mary's Hospital, London W2 1LA, UK claire.raphael@gmail.com z.whinnett@imperial.ac.uk.
authors.forename: Zachary I
authors.initials: ZI
authors.lastname: Whinnett
authors.affiliation: International Centre for Circulatory Health, National Heart Lung Institute, Imperial College, St. Mary's Hospital, London W2 1LA, UK.
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
authors.affiliation: Department of Cardiology, Karolinska University, Stockholm, Sweden.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Linde
authors.affiliation: Royal Brompton and Harefield NHS Foundation Trust and National Heart Lung Institute, Imperial College, London, UK.
authors.forename: John G F
authors.initials: JG
authors.lastname: Cleland
authors.affiliation: Division of Cardiology, University of Washington, Seattle, WA, USA.
authors.forename: Wayne C
authors.initials: WC
authors.lastname: Levy
authors.affiliation: International Centre for Circulatory Health, National Heart Lung Institute, Imperial College, St. Mary's Hospital, London W2 1LA, UK.
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000401:mortality / Q000628:therapy; D002304:Cardiac Pacing, Artificial; D016757:Death, Sudden, Cardiac / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D004812:Epidemiologic Methods; D006333:Heart Failure / Q000401:mortality / Q000628:therapy*; D006801:Humans; D008136:Longevity; D008875:Middle Aged; D018487:Ventricular Dysfunction, Left / Q000401:mortality / Q000628:therapy
keywords: Heart failure; ICD; Implantable cardioverter defibrillator; Lifespan; Mortality; Sudden death