title: Amplitude spectrum area: measuring the probability of successful defibrillation as applied to human data.
abstract: OBJECTIVE
  The objective of our study was to examine the effectiveness of an electrocardiographic predictor, amplitude spectral area (AMSA), for the optimal timing of defibrillation shocks in human victims of cardiac arrest. Based on the spectral characteristics of ventricular fibrillation potentials, we examined the probability of successful conversion to an organized viable rhythm, including the return of spontaneous circulation. The incentive was to predict the likelihood of successful defibrillation and thereby improve outcomes by minimizing interruptions in chest compression and minimizing electrically induced myocardial injury due to repetitive high-current shocks.
  
  
  METHODS
  Observational study on human electrocardiographic recordings during cardiopulmonary resuscitation.
  
  
  METHODS
  Medical research laboratory of a university-affiliated research and educational institute.
  
  
  METHODS
  Victims of out-of-hospital cardiac arrest.
  
  
  METHODS
  Iteration of electrocardiographic records, representing lead 2 equivalent recordings on 108 defibrillation attempts with an automated external defibrillator, of 46 victims of cardiac arrest due to ventricular fibrillation.
  
  
  RESULTS
  Three seconds of ventricular fibrillation, recorded immediately preceding delivery of a shock, were analyzed utilizing the AMSA algorithm. AMSA represents a numerical value based on the sum of the magnitude of the weighted frequency spectrum between 3 and 48 Hz. The greater the AMSA value, the greater was the probability of reversal of ventricular fibrillation. At an AMSA value of >13.0 mV-Hz, successful defibrillation yielded a sensitivity of .91 and a specificity of .94.
  
  
  CONCLUSIONS
  AMSA predicts the success of electrical defibrillation with high specificity. AMSA therefore serves to minimize interruptions of precordial compression and the myocardial damage caused by delivery of repetitive and ineffective electrical shocks.
authors.affiliation: Institute of Critical Care Medicine, Palm Springs, CA, USA.
authors.forename: Clayton
authors.initials: C
authors.lastname: Young
authors.forename: Joe
authors.initials: J
authors.lastname: Bisera
authors.forename: Stacy
authors.initials: S
authors.lastname: Gehman
authors.forename: David
authors.initials: D
authors.lastname: Snyder
authors.forename: Wanchun
authors.initials: W
authors.lastname: Tang
authors.forename: Max Harry
authors.initials: MH
authors.lastname: Weil
mesh_terms: D016208:Databases, Factual; D004554:Electric Countershock / Q000379:methods*; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D016896:Treatment Outcome