Cardiac Arrest

Overview

Cardiac arrest is a sudden, life-threatening emergency in which the heart abruptly stops pumping blood to the body and brain. Within seconds the person loses consciousness, collapses, and stops breathing normally. Without blood flow, the brain and other organs begin to suffer damage within minutes, which is why cardiac arrest requires immediate action.

Cardiac arrest is different from a heart attack, although the two are often confused. A heart attack is a blockage that cuts off blood supply to part of the heart muscle, while cardiac arrest is an electrical problem that makes the heart stop beating effectively. A heart attack can sometimes trigger a cardiac arrest. Survival depends on bystanders recognizing it instantly and starting CPR and using a defibrillator without delay.

Common Causes

Cardiac arrest usually results from a sudden, dangerous heart rhythm that prevents the heart from pumping. Common causes and triggers include:

• Dangerous heart rhythms: Very fast, chaotic rhythms (such as ventricular fibrillation) stop effective pumping. These can arise from various arrhythmias.
• Heart attack: A heart attack can disrupt the heart's electrical system and trigger arrest.
• Heart muscle disease: A weakened or thickened heart, including heart failure and inherited heart conditions, raises the risk.
• Severe electrolyte problems: Very abnormal potassium or other electrolyte levels can disturb the rhythm.
• Other causes: Major blood loss, drowning, severe drug overdose, electrocution, or a severe lack of oxygen.

Some people have inherited conditions or prior heart disease that increase risk, but cardiac arrest can also occur with no known prior heart problem.

Associated Symptoms

Cardiac arrest itself is dramatic and sudden:

• Sudden collapse and loss of consciousness
• No pulse and no normal breathing, or only gasping
• Unresponsiveness, including no reaction to shouting or shaking

Some people have warning signs in the minutes, hours, or days before, which should never be ignored:

• Chest pain or pressure
• Palpitations or a racing, irregular heartbeat
• Shortness of breath
• Unexplained fainting, dizziness, or extreme weakness

Sudden gasping breaths in a collapsed person are not normal breathing and should prompt immediate CPR.

Diagnosis & Evaluation

Recognizing cardiac arrest is done at the scene: an unresponsive person who is not breathing normally and has no pulse. Treatment must begin immediately, before any formal testing. After resuscitation, hospital evaluation looks for the cause and may include:

• An electrocardiogram (ECG) and continuous heart monitoring
• Blood tests for heart enzymes, electrolytes, and other problems
• Imaging of the heart, such as an echocardiogram or coronary angiogram
• Tests for inherited or structural heart conditions

These investigations guide treatment to prevent another arrest, but at the moment of collapse the priority is CPR and defibrillation, not diagnosis.

Treatment & Management

Cardiac arrest is treated with immediate emergency resuscitation, then care to prevent it from happening again.

• Call for help and start CPR: Call emergency services and begin chest compressions immediately. Push hard and fast in the center of the chest.
• Use an AED: An automated external defibrillator can shock a dangerous rhythm back to normal; follow its spoken instructions.
• Advanced care: Paramedics and hospital teams provide medications, advanced airway support, and treatment of the underlying cause.
• Preventing recurrence: Depending on the cause, treatment may include procedures for blocked arteries, medications, or an implantable defibrillator (ICD).

Every minute without CPR and defibrillation lowers the chance of survival, so bystander action is critical.

Reducing Your Risk

Many cardiac arrests are linked to heart disease, so steps that protect the heart also lower the risk of arrest:

• Manage heart risk factors: Control blood pressure, cholesterol, and diabetes, do not smoke, stay active, and eat a heart-healthy diet.
• Treat known heart conditions: Follow your treatment plan for heart disease, heart failure, or rhythm problems, and attend regular check-ups.
• Don't ignore warning signs: Get prompt evaluation for unexplained fainting, chest pain, palpitations, or a family history of sudden death, which may reveal a treatable risk.
• Know your family history: Some inherited heart conditions raise risk; tell your doctor if relatives had sudden cardiac death at a young age.
• Learn CPR: Knowing CPR and how to use an AED means you can help save a life if someone near you collapses.

For people at high risk, doctors may recommend an implantable defibrillator (ICD) that can detect and correct a dangerous rhythm automatically.

When to See a Doctor

Cardiac arrest is always a life-threatening emergency. If you see someone collapse and they are unresponsive and not breathing normally:

• Call emergency services right away (or have someone else call)
• Begin CPR immediately with hard, fast chest compressions
• Send someone to find and bring an AED, and use it as soon as possible
• Continue CPR until emergency responders take over

Do not wait to see if the person recovers. Separately, see a doctor promptly if you have warning signs such as unexplained fainting, chest pain, palpitations, or a family history of sudden cardiac death, as these may identify a treatable risk before an arrest occurs.

Related Topics

Frequently Asked Questions

References

1. American Heart Association. Cardiac Arrest.
2. Mayo Clinic. Sudden cardiac arrest — Symptoms and causes.
3. National Heart, Lung, and Blood Institute (NHLBI). Cardiac Arrest.
4. MedlinePlus, U.S. National Library of Medicine. Cardiac arrest.