title: Prospective use of a clinical decision rule to identify pulmonary embolism as likely cause of outpatient cardiac arrest.
abstract: A clinical decision rule (CDR) derived retrospectively found that 57% of outpatients aged 65 years or less, with witnessed arrest+PEA had pulmonary embolism (PE) as cause of cardiac arrest. These retrospectively studied patients also had significant frequency of pre-arrest respiratory distress, altered mental status, and shock.
  
  
  OBJECTIVE
  (1) To test prospectively the feasibility and diagnostic accuracy of this CDR. (2) To test if the pre-arrest clinical triad of respiratory distress, altered mental status and shock predicts the presence of PE. All EMS personnel (N=204) in an urban EMS system and Emergency Department physicians (N=143) at 7 hospitals were included in the CDR and data collection.
  
  
  METHODS
  age 18-70, non-trauma, witnessed arrest, PEA as the first and primary rhythm. Exclusion: defibrillation before or more often than once after PEA. Criterion standards: autopsy or predefined cardiopulmonary imaging for PE. Over 21 months, 44 subjects were enrolled. Thirty-three subjects had a criterion standard (N=20 autopsy, 13-other criteria). 18/33 (54%; 95% CI 36-72%) had PE. Of the PE arrests, 88% were witnessed by EMS (N=8) or ED physicians (N=8), compared with 47% in the non-PE group (N=3 EMS and N=4 ED). Of the PE arrests, 83% had at least two of the three components of the triad versus 33% of the non-PE group (95% CI for difference 20-79). Mortality was 100% in the PE group. Analysis of the EMS cardiac arrest registry indicated that 65% of all patients served by the EMS system, age<or=70 recorded as having pre-hospital PEA arrest were enrolled during the study period.
  
  
  CONCLUSIONS
  We implemented successfully a CDR in a large, urban prehospital system to detect PE rapidly as most likely cause of cardiac arrest.
authors.affiliation: Department of Emergency Medicine, Feinberg School of Medicine, Northwestern University, Emergency Medicine, 259 E. Erie Suite 100, Chicago, IL 60611, USA. mcourtney@nmff.org
authors.forename: D Mark
authors.initials: DM
authors.lastname: Courtney
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Kline
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000488:Allied Health Personnel; D003661:Decision Support Techniques; D004417:Dyspnea / Q000209:etiology; D004632:Emergency Medical Services / Q000379:methods*; D006323:Heart Arrest / Q000209:etiology*; D006801:Humans; D001523:Mental Disorders / Q000209:etiology; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000150:complications* / Q000175:diagnosis*; D012769:Shock / Q000209:etiology