When is a Cardiac Arrest Non-Cardiac?

Area of Science:

• Emergency medicine
• Cardiology
• Public health

Background:

• Out-of-hospital cardiac arrest (OHCA) survival rates are low (5-10%).
• Modified CPR algorithms show promise for improving OHCA survival.
• Many studies focus on presumed cardiac etiology, assuming airway management is less critical than chest compressions.

Purpose of the Study:

• To examine the variability in reported cardiac vs. non-cardiac etiology proportions in OHCA studies.
• To assess the consistency of prehospital clinical etiology assessment.

Main Methods:

• A Medline search was conducted using "OHCA" and "Emergency Medical Services" (EMS) as subject headings.
• Studies were included if they reported the prevalence of cardiac etiology in the overall OHCA patient sample.
• Studies lacking etiology data or excluding specific etiologies were excluded.

Main Results:

• Twenty-four studies with 27 datasets from 15 countries were analyzed.
• The prevalence of cardiac etiology in OHCA ranged widely from 50% to 91%.
• No clear patterns were observed based on database size, publication year, or geographic region.

Conclusions:

• Significant variation exists in reported cardiac etiology rates for OHCA.
• This variation may stem from differing actual etiologies, inconsistent definitions, or varied implementation of definitions.
• A consensus definition for cardiac etiology is needed to improve prehospital assessment and research consistency.