title: Prediction of defibrillation success from a single defibrillation threshold measurement with sequential pulses and two current pathways in humans.
abstract: The ultimate aim of defibrillation testing is to predict consistent defibrillation. This study tested the hypothesis that defibrillation success could be predicted from a single measurement of defibrillation threshold. We measured defibrillation threshold by using three patch electrodes and a standard protocol intraoperatively in 49 patients undergoing arrhythmia surgery. Each patient was then assigned to one of five energy subgroups (0.5, 1.0, 1.5, 2.0, or 2.5 times defibrillation threshold) for a single shock (followed by a rescue shock if necessary) for a subsequent ventricular fibrillation episode. A curve relating percent success to energy was then constructed for the group. Defibrillation threshold averaged 4.7 +/- 2.98 J for the group (mean +/- SD). There was a curvilinear relation between the energy of the defibrillation threshold ratio test shock and percent success: 33.3%, 58.3%, 81.8%, 91.7%, and 100% at mean defibrillation threshold ratios of 0.56 +/- 0.14, 1.02 +/- 0.07, 1.53 +/- 0.14, 1.88 +/- 0.09, and 2.60 +/- 0.14, respectively. We conclude that consistent defibrillation is predictable from a single measurement of defibrillation threshold. Furthermore, for an individual patient, a safety margin of 2.6 times defibrillation threshold should approximate 100% successful defibrillation for a single test shock.
authors.affiliation: Department of Medicine, University of Western Ontario, London, Canada.
authors.forename: D L
authors.initials: DL
authors.lastname: Jones
authors.forename: G J
authors.initials: GJ
authors.lastname: Klein
authors.forename: G M
authors.initials: GM
authors.lastname: Guiraudon
authors.forename: A D
authors.initials: AD
authors.lastname: Sharma
authors.forename: R
authors.initials: R
authors.lastname: Yee
authors.forename: M J
authors.initials: MJ
authors.lastname: Kallok
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000601:surgery; D004554:Electric Countershock / Q000379:methods*; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011897:Random Allocation; D014693:Ventricular Fibrillation / Q000628:therapy*