title: Left ventricular dysfunction is associated with prolonged average ventricular fibrillation cycle length in patients with implantable cardioverter defibrillators.
abstract: OBJECTIVE
  In cellular studies, ventricular refractoriness (ERP) is prolonged in heart failure (CHF), but clinical evidence is lacking. The average ventricular fibrillation cycle length (VFCL) has been shown to correlate with local ERP. We hypothesized that the VFCL increases with left ventricular (LV) dysfunction. Therefore, we evaluated intracardiac VFCL recorded by implantable defibrillators (ICD) in patients with and without LV dysfunction.
  
  
  METHODS
  We analyzed intracardiac VFCL recorded by sensing leads of Ventak MINI (Guidant) ICD in 49 patients (35 men; age 54 +/- 13 years; 25 (51%) with coronary artery disease; mean LV ejection fraction (EF) 41 +/- 17%, range 76-10) from the European Ventak MINI Investigator Group. No patients were receiving antiarrhythmic drugs, including beta-blockers. Mean and median VFCL were obtained at predischarge testing during first charge time (4.5 +/- 2.7 s, range 1.4-11).
  
  
  RESULTS
  Mean median VFCL was 186 +/- 21ms (range 150-230 ms). Patients with LVEF >/= 50% (n = 14) had shorter median VFCL than patients with LVEF < 50% (n = 35), (171 +/- 14 vs. 191 +/- 20 ms; p = 0.002). Median VFCL correlated with LVEF (r = -0.41; p = 0.003) and age (r = 0.28, p = 0.04), but was not significantly associated with charge time and defibrillation threshold at implant. Similar results occurred with mean VFCL. In multiple linear regression and correlation models, only LVEF% was a significant predictor (p < 0.05 for all models) of median VFCL.
  
  
  CONCLUSIONS
  LV dysfunction prolongs averaged VFCL in patients at risk for malignant ventricular arrhythmias who have implantable cardioverter defibrillators. This phenomenon might be related to alterations in the ventricular refractory period.
authors.affiliation: Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA. guilhermefenelon@uol.com.br
authors.forename: Guilherme
authors.initials: G
authors.lastname: Fenelon
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Stambler
authors.forename: Etienne
authors.initials: E
authors.lastname: Huvelle
authors.forename: Pedro
authors.initials: P
authors.lastname: Brugada
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
mesh_terms: D000704:Analysis of Variance; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*; D014693:Ventricular Fibrillation / Q000503:physiopathology* / Q000517:prevention & control