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Cardiac Arrest Surveillance System

The Cardiac Arrest Surveillance System (CASS) began with the implementation of paramedic services in King County in 1976. Its purpose is to identify and document all cases of cardiac arrest in which CPR is performed by EMS. These are the data collected:

Field data

  • age, gender
  • location of cardiac arrest
  • witnessed or unwitnessed
  • who started CPR
  • rhythm on EMS arrival
  • arrival times of ALS and BLS
  • treatments given


  • death at scene
  • hospital admission
  • hospital discharge

Etiologic classification is assigned based on:

  • death certificate
  • history and medications listed on the MIRF
  • hospital discharge diagnosis

Patients' names and personal information are protected under laws governing confidentiality. The data are used for quality review of EMS programs and documenting the effectiveness of community programs, and have been featured in many national and international publications.

To see a five-year summary of survival data, see the Utstein Report, 2007-2011 (PDF). The Utstein Style has become the world-wide standard for reporting cardiac arrest outcome data. To learn more about Utstein templates, see: Jacobs I, Nadkarni V et al. Cardiac arrest and cardiopulmonary resuscitation outcome reports: update and simplification of the Utstein templates for resuscitation registries. Circulation 2004 Nov 23;110(21):3385-97.