title: Rates of upgrade of ICD recipients to CRT in clinical practice and the potential impact of the more liberal use of CRT at initial implant.
abstract: BACKGROUND
  Many implantable cardioverter defibrillator (ICD) recipients may develop indications for cardiac resynchronization therapy (CRT) during follow-up. However, the actual upgrade rate during follow-up in clinical practice is not known.
  
  
  METHODS
  We performed a single center retrospective observational study of all new ICD implants over 5 years (2003-2007). The rate of CRT upgrade of patients initially implanted with a single-/dual-chamber ICD during follow-up was assessed. The impact of using alternative criteria on the need for CRT in ICD recipients at initial implant was also evaluated.
  
  
  RESULTS
  During the study period, there were 549 new ICD implants. The initial implant was a single/dual-chamber ICD in 73% (n = 399) and a CRT-D in 27% (n = 150). During follow-up (48±20 months) of the 399 ICD recipients, 70 (17.5%) died and 15 (3.8%) were upgraded to CRT, including eight cases where left ventricular lead implant had been initially unsuccessful. Upgrade rates at 1, 3, and 5 years were 0.03%, 2.4%, and 5.1%, respectively. Using alternative CRT criteria (left ventricular ejection fraction [LVEF]≤30%, QRS ≥130 ms, New York Heart Association I-IV) 42.6% (n = 234) of ICD recipients met criteria for CRT at initial implant.
  
  
  CONCLUSIONS
  In this retrospective single center study, rates of CRT upgrade in ICD recipients over the medium term were low, which may reflect underuse in otherwise appropriate candidates. The more liberal use of CRT at initial implant in patients with a reduced LVEF, a broad QRS, but only mild heart failure symptoms would require approximately 50% increase in CRT use in ICD recipients at initial implant, and may help address some of the suggested underutilization.
authors: Wessex Cardiothoracic Unit, Southampton University Hospitals NHS Trust, Southampton, UK. paul.andrew.scott@btinternet.com
authors: Paul A
authors: PA
authors: Scott
authors: Andrew
authors: A
authors: Whittaker
authors: Mehmood
authors: M
authors: Zeb
authors: Edd
authors: E
authors: Watts
authors: Arthur M
authors: AM
authors: Yue
authors: Paul R
authors: PR
authors: Roberts
authors: John M
authors: JM
authors: Morgan
mesh_terms: D058409:Cardiac Resynchronization Therapy Devices / Q000706:statistics & numerical data*; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D020878:Device Removal; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000453:epidemiology* / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D006113:United Kingdom / Q000453:epidemiology