title: Amplitude spectrum area to guide resuscitation-a retrospective analysis during out-of-hospital cardiopulmonary resuscitation in 609 patients with ventricular fibrillation cardiac arrest.
abstract: BACKGROUND
  The capability of amplitude spectrum area (AMSA) to predict the success of defibrillation (DF) was retrospectively evaluated in a large database of out-of-hospital cardiac arrests.
  
  
  METHODS
  Electrocardiographic data, including 1260 DFs, were obtained from 609 cardiac arrest patients due to ventricular fibrillation. AMSA sensitivity, specificity, accuracy, and positive and negative predictive values (PPV, NPV) for predicting DF success were calculated, together with receiver operating characteristic (ROC) curves. Successful DF was defined as the presence of spontaneous rhythm ≥40bpm starting within 60s from the DF. In 303 patients with chest compression (CC) depth data collected with an accelerometer, changes in AMSA were analyzed in relationship to CC depth.
  
  
  RESULTS
  AMSA was significantly higher prior to a successful DF than prior to an unsuccessful DF (15.6±0.6 vs. 7.97±0.2mV-Hz, p<0.0001). Intersection of sensitivity, specificity and accuracy curves identified a threshold AMSA of 10mV-Hz to predict DF success with a balanced sensitivity, specificity and accuracy of almost 80%. Higher AMSA thresholds were associated with further increases in accuracy, specificity and PPV. AMSA of 17mV-Hz predicted DF success in two third of instances (PPV of 67%). Low AMSA, instead, predicted unsuccessful DFs with high sensitivity and NPV >97%. Area under the ROC curve was 0.84. CC depth affected AMSA value. When depth was <1.75in., AMSA decreased for consecutive DFs, while it increased when the depth was >1.75in. (p<0.05).
  
  
  CONCLUSIONS
  AMSA could be a useful tool to guide CPR interventions and predict the optimal timing of DF.
authors.affiliation: IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri", Milan, Italy. Electronic address: gristag@gmail.com.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Ristagno
authors.forename: Yongqin
authors.initials: Y
authors.lastname: Li
authors.forename: Francesca
authors.initials: F
authors.lastname: Fumagalli
authors.forename: Andrea
authors.initials: A
authors.lastname: Finzi
authors.forename: Weilun
authors.initials: W
authors.lastname: Quan
mesh_terms: D004554:Electric Countershock; D004562:Electrocardiography / Q000379:methods*; D006801:Humans; D058687:Out-of-Hospital Cardiac Arrest / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000150:complications / Q000503:physiopathology / Q000628:therapy*
keywords: Amplitude spectrum area; Defibrillation; Outcome; Prediction; Ventricular fibrillation