Prospective use of a clinical decision rule to identify pulmonary embolism as likely cause of outpatient cardiac arrest

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. Objectives: (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. Inclusion criteria: 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 ≤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.