title: Impact of upgrade to cardiac resynchronization therapy on ventricular arrhythmia frequency in patients with implantable cardioverter-defibrillators.
abstract: OBJECTIVE
  This study compared cardiac resynchronization therapy's (CRT) impact on ventricular tachyarrhythmia susceptibility in patients who, due to worsening heart failure (HF) symptoms, underwent a replacement of a conventional implantable cardioverter-defibrillator (ICD) with a CRT-ICD.
  
  
  BACKGROUND
  Cardiac resynchronization therapy is an effective addition to conventional treatment of HF in many patients with left ventricular systolic dysfunction. However, whether CRT-induced improvements in HF status also reduce susceptibility to life-threatening arrhythmias is less certain.
  
  
  METHODS
  Clinical and ICD electrogram data were evaluated in 18 consecutive ICD patients who underwent an upgrade to CRT-ICD. Pharmacologic HF therapy was not altered during follow-up. The definition of ventricular tachycardia (VT) and ventricular fibrillation (VF) for each patient was as determined by device programming. Statistical comparisons used paired t tests.
  
  
  RESULTS
  Findings were recorded during two time periods: 47 +/- 21 months (range 24 to 70 months) before and 14 +/- 2 months (range 9 to 18 months) after CRT upgrade. At time of upgrade, patient age was 69 +/- 11 years and ejection fraction was 21 +/- 8%. Before CRT the frequency of VT, VF, and appropriate ICD shocks was 0.31 +/- 1.23, 0.047 +/- 0.083, and 0.048 +/- 0.085 episodes/month/patient, respectively. After CRT-ICD, VT and VF arrhythmia burdens and frequency of shocks were respectively 0.13 +/- 0.56, 0.001 +/- 0.004, and 0.003 +/- 0.016 episodes/month/patient (p = 0.59, 0.03, and 0.05 vs. pre-CRT).
  
  
  CONCLUSIONS
  Arrhythmia frequency and number of appropriate ICD treatments were reduced after upgrade to CRT-ICD for HF treatment. Thus, apart from hemodynamic benefits, CRT may also ameliorate ventricular tachyarrhythmia susceptibility in HF patients.
authors.affiliation: Cardiac Arrhythmia Center, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Cengiz
authors.initials: C
authors.lastname: Ermis
authors.forename: Ryan
authors.initials: R
authors.lastname: Seutter
authors.forename: Alan X
authors.initials: AX
authors.lastname: Zhu
authors.forename: Lauren C
authors.initials: LC
authors.lastname: Benditt
authors.forename: Laura
authors.initials: L
authors.lastname: VanHeel
authors.forename: Scott
authors.initials: S
authors.lastname: Sakaguchi
authors.forename: Keith G
authors.initials: KG
authors.lastname: Lurie
authors.forename: Fei
authors.initials: F
authors.lastname: Lu
authors.forename: David G
authors.initials: DG
authors.lastname: Benditt
mesh_terms: D000368:Aged; D002303:Cardiac Output, Low / Q000503:physiopathology / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D017180:Tachycardia, Ventricular / Q000517:prevention & control*; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000517:prevention & control*