title: Resumption of chest compressions after successful defibrillation and risk for recurrence of ventricular fibrillation in out-of-hospital cardiac arrest.
abstract: BACKGROUND
  Prior investigation of out-of-hospital cardiac arrest has raised the concern that ventricular fibrillation (VF) recurrence may be triggered by chest compression (CC) resumption. We investigated predictors of VF recurrence after defibrillation, including timing of CC resumption.
  
  
  RESULTS
  Patients with witnessed out-of-hospital cardiac arrest and initial rhythm of VF from an Utstein-style database were analyzed. For each shock that defibrillated VF, CC resumption and VF recurrence times were determined. Shocks were classified according to postshock rhythm. Factors (age, sex, time from dispatch to monitor/defibrillator application, and CC resumption) that could predict VF recurrence were analyzed. CC resumption was categorized into groups: CC1, 1 to 5 seconds; CC2, 6 to 10 seconds; CC3, 11 to 30 seconds; and CC4, >30 seconds. Eighty-eight subjects were analyzed, with a total of 285 shocks, with 226 shocks that achieved asystole (n=102), organized rhythm (n=120), or monomorphic ventricular tachycardia (n=4). After a successful shock, CC resumption occurred at a median (interquartile range) of 8 (5-18) seconds. VF recurred after 166 shocks (74%) and recurred within 30 seconds in 69 shocks. There was no significant relationship between VF recurrence and factors analyzed including CC resumption time, nor stratified by postshock rhythm. The hazard ratios (HRs) for VF recurrence within 30 seconds for later CC groups (CC2, CC3, and CC4) relative to early CC resumption (CC1) were as follows: HR(CC2)=1.05 (P=0.9); HR(CC3)=1.75 (P=0.1); and HR(CC4)=0.67 (P=0.4).
  
  
  CONCLUSIONS
  VF recurrence within 30 seconds of a defibrillatory shock was not dependent on timing of CC resumption in patients with witnessed arrest and initial rhythm of VF.
authors.affiliation: From the Sarver Heart Center (Z.C., K.B.K., D.W.S., J.H.I.), and Arizona Emergency Medicine Research Center, Department of Emergency Medicine (D.W.S.), University of Arizona College of Medicine, Tucson; Maricopa Medical Center Department of Emergency Medicine, University of Arizona College of Medicine, Phoenix (B.J.B.); and ZOLL Medical Corporation, Chelmsford, MA (A.E.S.).
authors.forename: Zacherie
authors.initials: Z
authors.lastname: Conover
authors.affiliation: From the Sarver Heart Center (Z.C., K.B.K., D.W.S., J.H.I.), and Arizona Emergency Medicine Research Center, Department of Emergency Medicine (D.W.S.), University of Arizona College of Medicine, Tucson; Maricopa Medical Center Department of Emergency Medicine, University of Arizona College of Medicine, Phoenix (B.J.B.); and ZOLL Medical Corporation, Chelmsford, MA (A.E.S.).
authors.forename: Karl B
authors.initials: KB
authors.lastname: Kern
authors.affiliation: From the Sarver Heart Center (Z.C., K.B.K., D.W.S., J.H.I.), and Arizona Emergency Medicine Research Center, Department of Emergency Medicine (D.W.S.), University of Arizona College of Medicine, Tucson; Maricopa Medical Center Department of Emergency Medicine, University of Arizona College of Medicine, Phoenix (B.J.B.); and ZOLL Medical Corporation, Chelmsford, MA (A.E.S.).
authors.forename: Annemarie E
authors.initials: AE
authors.lastname: Silver
authors.affiliation: From the Sarver Heart Center (Z.C., K.B.K., D.W.S., J.H.I.), and Arizona Emergency Medicine Research Center, Department of Emergency Medicine (D.W.S.), University of Arizona College of Medicine, Tucson; Maricopa Medical Center Department of Emergency Medicine, University of Arizona College of Medicine, Phoenix (B.J.B.); and ZOLL Medical Corporation, Chelmsford, MA (A.E.S.).
authors.forename: Bentley J
authors.initials: BJ
authors.lastname: Bobrow
authors.affiliation: From the Sarver Heart Center (Z.C., K.B.K., D.W.S., J.H.I.), and Arizona Emergency Medicine Research Center, Department of Emergency Medicine (D.W.S.), University of Arizona College of Medicine, Tucson; Maricopa Medical Center Department of Emergency Medicine, University of Arizona College of Medicine, Phoenix (B.J.B.); and ZOLL Medical Corporation, Chelmsford, MA (A.E.S.).
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Spaite
authors.affiliation: From the Sarver Heart Center (Z.C., K.B.K., D.W.S., J.H.I.), and Arizona Emergency Medicine Research Center, Department of Emergency Medicine (D.W.S.), University of Arizona College of Medicine, Tucson; Maricopa Medical Center Department of Emergency Medicine, University of Arizona College of Medicine, Phoenix (B.J.B.); and ZOLL Medical Corporation, Chelmsford, MA (A.E.S.). jindik@email.arizona.edu.
authors.forename: Julia H
authors.initials: JH
authors.lastname: Indik
mesh_terms: D000368:Aged; D001130:Arizona; D047548:Defibrillators; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation; D004562:Electrocardiography; D004632:Emergency Medical Services / Q000379:methods*; D005260:Female; D006336:Heart Massage / Q000009:adverse effects; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D011237:Predictive Value of Tests; D012008:Recurrence; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*
keywords: cardiopulmonary resuscitation; heart arrest; ventricular fibrillation