title: A novel low-energy electrotherapy that terminates ventricular tachycardia with lower energy than a biphasic shock when antitachycardia pacing fails.
abstract: OBJECTIVE
  The authors sought to develop a low-energy electrotherapy that terminates ventricular tachycardia (VT) when antitachycardia pacing (ATP) fails.
  
  
  BACKGROUND
  High-energy implantable cardioverter-defibrillator (ICD) shocks are associated with device failure, significant morbidity, and increased mortality. A low-energy alternative to ICD shocks is desirable.
  
  
  METHODS
  Myocardial infarction was created in 25 dogs. Sustained, monomorphic VT was induced by programmed stimulation. Defibrillation electrodes were placed in the right ventricular apex, and coronary sinus and left ventricular epicardium. If ATP failed to terminate sustained VT, the defibrillation thresholds (DFTs) of standard versus experimental electrotherapies were measured.
  
  
  RESULTS
  Sustained VT ranged from 276 to 438 beats/min (mean 339 beats/min). The right ventricular-coronary sinus shock vector had lower impedance than the right ventricular-left ventricular patch (54.4 ± 18.1 Ω versus 109.8 ± 16.9 Ω; p < 0.001). A single shock required between 0.3 ± 0.2 J to 5.9 ± 2.5 J (mean 2.64 ± 3.22 J; p = 0.008) to terminate VT, and varied depending upon the phase of the VT cycle in which it was delivered. By contrast, multiple shocks delivered within 1 VT cycle length were not phase dependent and achieved lower DFT compared with a single shock (0.13 ± 0.09 J for 3 shocks, 0.08 ± 0.04 J for 5 shocks, and 0.09 ± 0.07 J for 7 shocks; p < 0.001). Finally, a multistage electrotherapy (MSE) achieved significantly lower DFT compared with a single biphasic shock (0.03 ± 0.05 J versus 2.37 ± 1.20 J; respectively, p < 0.001). At a peak shock amplitude of 20 V, MSE achieved 91.3% of terminations versus 10.5% for a biphasic shock (p < 0.001).
  
  
  CONCLUSIONS
  MSE achieved a major reduction in DFT compared with a single biphasic shock for ATP-refractory monomorphic VT, and represents a novel electrotherapy to reduce high-energy ICD shocks.
authors.affiliation: Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO 63130, USA.
authors.forename: Ajit H
authors.initials: AH
authors.lastname: Janardhan
authors.forename: Wenwen
authors.initials: W
authors.lastname: Li
authors.forename: Vadim V
authors.initials: VV
authors.lastname: Fedorov
authors.forename: Michael
authors.initials: M
authors.lastname: Yeung
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wallendorf
authors.forename: Richard B
authors.initials: RB
authors.lastname: Schuessler
authors.forename: Igor R
authors.initials: IR
authors.lastname: Efimov
mesh_terms: D000818:Animals; D017147:Defibrillators, Implantable; D004195:Disease Models, Animal; D004285:Dogs; D004599:Electric Stimulation Therapy / Q000379:methods*; D004562:Electrocardiography; D004868:Equipment Failure; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000628:therapy*