Cardiac arrest

Cardiac arrest is the sudden loss of effective heart activity, stopping circulation and causing unconsciousness and absent or abnormal breathing. It is a medical emergency requiring immediate resuscitation.

Ventricular fibrillation: A disorganized ventricular rhythm that prevents effective pumping and commonly causes cardiac arrest. This shockable rhythm is a major arrest mechanism and a target of defibrillation.
Chain of survival: A sequence of coordinated actions intended to improve survival after cardiac arrest. Its links organize recognition, CPR, defibrillation, and post-arrest care.
Sudden cardiac death: An unexpected death caused by loss of cardiac function, usually occurring rapidly after symptom onset. Fatal cardiac arrest is the immediate event underlying many sudden cardiac deaths.
Heart attack: A blockage of blood flow to heart muscle that causes myocardial injury. A heart attack is a circulation problem in the heart; cardiac arrest is loss of effective pumping.
Pulseless electrical activity: Organized electrical activity without a detectable pulse or effective circulation. It causes arrest despite electrical signals, so defibrillation is not its treatment.
Automated external defibrillator: A portable device that analyzes heart rhythm and advises or delivers a defibrillation shock. It enables rapid rhythm assessment and shock delivery before advanced care arrives.
Out-of-hospital cardiac arrest: Cardiac arrest occurring outside a hospital, often before professional medical help arrives. Bystander action and access to defibrillation strongly shape outcomes in this setting.
Syncope: A brief loss of consciousness caused by temporary reduction in blood flow to the brain. Syncope usually resolves spontaneously, unlike ongoing cardiac arrest without circulation.
Asystole: Near-absence of ventricular electrical activity on an electrocardiogram. This non-shockable rhythm is a distinct electrical presentation of cardiac arrest.
Advanced cardiac life support: A set of advanced interventions for cardiac arrest and other life-threatening cardiovascular emergencies. It adds rhythm-directed treatment, medications, and airway management to basic resuscitation.

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