title: Induction by direct current pulse versus 50-Hz pacing on ventricular fibrillation and defibrillation.
abstract: BACKGROUND
  Ventricular fibrillation (VF) induced by different modes of induction may have different characteristics and defibrillation thresholds. This study compares the cycle lengths and defibrillation of VF induced by direct current (DC) pulses vs 50 Hz.
  
  
  METHODS
  We compared induction by DC pulses and 50-Hz pacing in this single-centre observational study of 259 consecutive patients with implantable cardioverter defibrillators in 2007-2008. Patients with inadequate defibrillation safety margin (DSM), defined as unsuccessful defibrillation at 25 J, were identified.
  
  
  RESULTS
  Of the 259 patients, 132 underwent induction with DC pulses and 127 with 50-Hz pacing. DC pulses induced VF of shorter cycle lengths (207 ± 16 vs 231 ± 24 ms, p < 0.001) compared to 50-Hz pacing. There were 17 patients (6.6%) with inadequate DSM-13/132 (9.8%) with DC pulse vs 4/127 (3.1%) with 50-Hz pacing (p < 0.001). The induced VF cycle lengths were shorter in patients with inadequate DSM (186 ± 25 vs 221 ± 21 ms, p < 0.001). On multivariate analysis, only the induced VF cycle length (p = 0.002) was independently associated with inadequate DSM.
  
  
  CONCLUSIONS
  VF of shorter cycle lengths is independently associated with inadequate DSM. DC pulses are associated with greater proportion of patients with inadequate DSM as it induces VF of shorter cycle lengths compared to 50-Hz pacing.
authors.affiliation: University Hospital Birmingham NHS Trust, Edgbaston, Birmingham B15 2TH, UK. hsern@doctors.net.uk
authors.forename: Hoong Sern
authors.initials: HS
authors.lastname: Lim
authors.forename: Sharon
authors.initials: S
authors.lastname: Flannigan
authors.forename: Howard
authors.initials: H
authors.lastname: Marshall
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017147:Defibrillators, Implantable; D025802:Electric Capacitance; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014693:Ventricular Fibrillation / Q000517:prevention & control*
references.citation: Heart Rhythm. 2006 Sep;3(9):1010-6
references.pmid: 16945792
references.citation: Circulation. 2006 Jul 11;114(2):104-9
references.pmid: 16818810
references.citation: J Interv Card Electrophysiol. 2007 Apr;18(3):247-63
references.pmid: 17541815
references.citation: J Cardiovasc Electrophysiol. 2006 Apr;17(4):377-81
references.pmid: 16643358
references.citation: Pacing Clin Electrophysiol. 1999 Feb;22(2):302-6
references.pmid: 10087544
references.citation: Pacing Clin Electrophysiol. 2003 Jan;26(1 Pt 1):44-8
references.pmid: 12685138
references.citation: Pacing Clin Electrophysiol. 2006 Aug;29(8):885-91
references.pmid: 16923006
references.citation: Pacing Clin Electrophysiol. 2004 Jan;27(1):89-94
references.pmid: 14720161
references.citation: Pacing Clin Electrophysiol. 1993 Apr;16(4 Pt 1):769-77
references.pmid: 7683804
references.citation: Pacing Clin Electrophysiol. 1989 Sep;12(9):1522-9
references.pmid: 2476781
references.citation: Pacing Clin Electrophysiol. 1998 May;21(5):1093-7
references.pmid: 9604241
references.citation: J Am Coll Cardiol. 1999 Jan;33(1):33-8
references.pmid: 9935005
references.citation: Pacing Clin Electrophysiol. 2002 Apr;25(4 Pt 1):408-13
references.pmid: 11991364
references.citation: Heart Rhythm. 2006 Sep;3(9):1053-9
references.pmid: 16945801
references.citation: J Cardiovasc Electrophysiol. 1994 Jul;5(7):581-90
references.pmid: 7987528
references.citation: J Cardiovasc Electrophysiol. 2000 Dec;11(12):1355-63
references.pmid: 11196559