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Cardiac Arrest Background

Jimmy September 4, 2021


A cardiac arrest is defined in clinical terms as a sudden, prolonged state of unconsciousness with pulselessness and apnea or agonizing breathing.

Though data on cardiac arrest cases varies widely, it is estimated there are more than 350,000 people in the United States being evaluated by emergency medical services (EMS) for a suspected out-of-hospital cardiac arrest each year.

National estimates for out-of-hospital cardiac arrest survival for patients that are transported to the hospital is ~ 10.8%, but when taking into consideration the deceased on arrival cases the overall is about 5-percent for all out-of-hospital cardiac arrests.

79% of cases have a presentation with non-shocking heart rhythms (PEA and asystole), compared to 21% having shockable rhythms (ventricular fibrillation and Pulseless Ventricular Tachycardia).

The Cardiac Arrest Registry to Enhance Survival (CARES) project reported asystole to be the most common presenting rhythm (47.3%) of the initial rhythms.

If survival rates were broken down by the presented rhythm, PEA/asystole had a survival rate of 12.2% compared to 35% for shock-like rhythms.


The most common condition that causes an adult patient to suffer a sudden cardiac death is coronary artery disease, and it accounts for 75% of such events.

In pediatric patients, cardiac arrest is often the terminal event of respiratory failure or progressive shock.

The pathophysiological causes of cardiac arrest are mostly attributed to cardiac abnormalities but could be attributed to other causes listed below.

Common causes of sudden cardiac arrest

Phases of Cardiac Arrest

  • There‚Äôs a proposed model for cardiac arrest that breaks down the event based on the pathology and therapeutic intervention need.
    • Electrical phase (the first 4 minutes after arrest)
      • Usually, initial rhythm is shockable
      • Defibrillation as the first therapy for VF/VT
        • A defibrillator deployed within the first few minutes is associated with a better than 50% chance of survival from the start.
    • Circulatory phase (minutes 4 through 10)
      • This is initially managed with chest compressions and ventilation followed by defibrillation after several minutes of CPR.
    • Metabolic phase (after 10 minutes)
      • The effectiveness of both defibrillation and CPR are significantly reduced, and additional medication may assist with perfusion to the heart

Predictors for Survival