title: Comparison of defibrillation thresholds using monodirectional electrical vector versus bidirectional electrical vector.
abstract: BACKGROUND
  Currently, two main lead configurations are used for implantable cardioverter-defibrillators (ICD). One generates a monodirectional electrical vector by using the can surface as an active part (hot can) together with a right ventricular defibrillation coil. The other one (TRIAD) produces a bidirectional electrical vector by adding a proximal defibrillation electrode on the same lead. The purpose of this prospective study was to determine whether there is a difference between these configurations in terms of the acute defibrillation threshold (DFT). The secondary objective was to evaluate the possible sequential effect of successive arrhythmia induction and defibrillation shocks on the final DFT value.
  
  
  METHODS
  In 44 patients (37 males, 7 females, mean age 59.18 +/- 12.05 years; mean ejection fraction 35.21 +/- 11.69%), a Hot Can Ventak family ICD (Guidant, St. Paul, MN, USA) was implanted in a left pectoral pocket. During the implant procedure, step-down to failure DFT testing was performed twice in each patient using the two different above-mentioned configurations: the bidirectional and the monodirectional. The first configuration to be tested was determined by a 1:1 randomization by center.
  
  
  RESULTS
  The step-down DFT protocol was followed in 35 patients. The average DFT was 8.6 +/- 4.0 J for TRIAD and 10.4 +/- 4.3 J for the monodirectional (p = 0.009) lead configuration; this represents a 16.3% decrease in the DFT using a bidirectional configuration. Furthermore, no relationship between the final DFT and the number of ventricular fibrillation inductions and shocks received was observed, confirming the secondary objective.
  
  
  CONCLUSIONS
  Compared to the monodirectional electrical vector, the bidirectional electrical vector is clearly more beneficial for the patient.
authors.affiliation: Cardiology Department, University of Turin, Italy. luigi.libero@galactica.it
authors.forename: L
authors.initials: L
authors.lastname: Libero
authors.forename: I F
authors.initials: IF
authors.lastname: Lozano
authors.forename: M
authors.initials: M
authors.lastname: Bocchiardo
authors.forename: M
authors.initials: M
authors.lastname: Marcolongo
authors.forename: L
authors.initials: L
authors.lastname: Sallusti
authors.forename: A
authors.initials: A
authors.lastname: Madrid
authors.forename: F
authors.initials: F
authors.lastname: Gaita
authors.forename: G P
authors.initials: GP
authors.lastname: Trevi
mesh_terms: D000328:Adult; D000368:Aged; D000638:Amiodarone / Q000627:therapeutic use; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods; D005121:Extremities / Q000098:blood supply; D005260:Female; D006331:Heart Diseases / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D014665:Vasodilator Agents / Q000627:therapeutic use; D014672:Vectorcardiography / Q000379:methods
chemical_list: D014665:Vasodilator Agents; D000638:Amiodarone