title: The Effect of Direct Current Stimulation versus T-Wave Shock on Defibrillation Threshold Testing.
abstract: BACKGROUND
  There are several methods to induce ventricular fibrillation (VF) during defibrillation threshold (DFT) testing. Delivering a shock at a critical time during the T wave (T-shock) is the conventional approach, while delivering a constant direct current voltage (DC stim) from the implantable cardioverter defibrillator is an alternative method. Only a few reports compare VF induction methods. The purpose of this study was to evaluate the effects and safety of DC stim versus T-shock.
  
  
  METHODS
  We retrospectively investigated 414 consecutive patients undergoing DFT testing. We compared the two groups (DC stim and T-shock) with respect to clinical characteristics, electrocardiogram (ECG) changes, and complications.
  
  
  RESULTS
  Ventricular arrhythmia, including ventricular tachycardia (VT) and VF, was induced by DC stim in 93 patients or T-shock in 321 patients. No more than three attempts were performed during one procedure. There was no significant difference in the baseline ECG, induced tachycardia cycle length (TCL), or complications between the two groups. However, the induced TCL was significantly shorter than the clinical TCL regardless of induction method (P = 0.001). Five patients suffered major complications (i.e., electromechanical dissociation or incessant VT). A history of atrial fibrillation was significantly greater in patients with major complications than the others (80% vs 24%, P = 0.004), and was an independent predictor on multivariate analysis.
  
  
  CONCLUSIONS
  There is no significant difference in induced TCL or complications between the DC stim and T-shock. The induced TCL is significantly shorter than clinical TCL regardless of induction method.
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ito
authors.affiliation: Division of Cardiology, Department of Medicine, Showa University, Tokyo, Japan.
authors.forename: Mitsuharu
authors.initials: M
authors.lastname: Kawamura
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Nitish
authors.initials: N
authors.lastname: Badhwar
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Vasanth
authors.initials: V
authors.lastname: Vedantham
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Zian H
authors.initials: ZH
authors.lastname: Tseng
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Byron K
authors.initials: BK
authors.lastname: Lee
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Lee
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Marcus
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Edward P
authors.initials: EP
authors.lastname: Gerstenfeld
authors.affiliation: Division of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.
authors.forename: Melvin M
authors.initials: MM
authors.lastname: Scheinman
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D004056:Differential Threshold; D004558:Electric Stimulation / Q000009:adverse effects / Q000379:methods*; D022062:Electrophysiologic Techniques, Cardiac / Q000009:adverse effects / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D012495:San Francisco / Q000453:epidemiology; D017678:Sex Distribution; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000453:epidemiology* / Q000209:etiology; D014693:Ventricular Fibrillation / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control*
keywords: defibrillation threshold testing; direct current voltage; electromechanical dissociation; shock on T; tachycardia cycle length