title: Rapidly switching multidirectional defibrillation: reversal of ventricular fibrillation with lower energy shocks.
abstract: OBJECTIVE
  Cardiac arrest after open surgery has an incidence of approximately 3%, of which more than 50% of the cases are due to ventricular fibrillation. Electrical defibrillation is the most effective therapy for terminating cardiac arrhythmias associated with unstable hemodynamics. The excitation threshold of myocardial microstructures is lower when external electrical fields are applied in the longitudinal direction with respect to the major axis of cells. However, in the heart, cell bundles are disposed in several directions. Improved myocardial excitation and defibrillation have been achieved by applying shocks in multiple directions via intracardiac leads, but the results are controversial when the electrodes are not located within the cardiac chambers. This study was designed to test whether rapidly switching shock delivery in 3 directions could increase the efficiency of direct defibrillation.
  
  
  METHODS
  A multidirectional defibrillator and paddles bearing 3 electrodes each were developed and used in vivo for the reversal of electrically induced ventricular fibrillation in an anesthetized open-chest swine model. Direct defibrillation was performed by unidirectional and multidirectional shocks applied in an alternating fashion. Survival analysis was used to estimate the relationship between the probability of defibrillation and the shock energy.
  
  
  RESULTS
  Compared with shock delivery in a single direction in the same animal population, the shock energy required for multidirectional defibrillation was 20% to 30% lower (P < .05) within a wide range of success probabilities.
  
  
  CONCLUSIONS
  Rapidly switching multidirectional shock delivery required lower shock energy for ventricular fibrillation termination and may be a safer alternative for restoring cardiac sinus rhythm.
authors.affiliation: Department of Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Viana
authors.affiliation: Center for Biomedical Engineering, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors.forename: Rosana A
authors.initials: RA
authors.lastname: Bassani
authors.affiliation: Department of Surgery, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil. Electronic address: petrucci@unicamp.br.
authors.forename: Orlando
authors.initials: O
authors.lastname: Petrucci
authors.affiliation: Department of Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors.forename: Denilson A
authors.initials: DA
authors.lastname: Marques
authors.affiliation: Department of Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil; Center for Biomedical Engineering, University of Campinas (UNICAMP), Campinas, São Paulo, Brazil.
authors.forename: José Wilson M
authors.initials: JW
authors.lastname: Bassani
mesh_terms: D000818:Animals; D047548:Defibrillators; D004195:Disease Models, Animal; D004554:Electric Countershock / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D005260:Female; D006439:Hemodynamics; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*