In 2011, ≈326200 people experienced emergency medical
services–assessed out-of-hospital cardiac arrests in the
United States. Survival to hospital discharge after nontraumatic
EMS-treated cardiac arrest with any first recorded
rhythm was 10.6% for patients of any age. Of the 19300
bystander-witnessed out-of-hospital cardiac arrests in
2011, 31.4% of victims survived.