Understanding Sudden Cardiac Arrest (Ventricular Fibrillation) | Palo Alto Medical Foundation Arrhythmia Center

What is Sudden Cardiac Arrest?

Sudden Cardiac Arrest (SCA) happens when the heart suddenly stops pumping blood the right way. This occurs because the lower chambers of the heart (the ventricles) go into a very fast and chaotic rhythm called ventricular fibrillation (VF).

When this happens, the heart cannot pump blood to the brain and body.

SCA is not the same as a heart attack. A heart attack is caused by a blocked blood vessel. Sudden cardiac arrest is usually an electrical problem in the heart. It is more common in people who already have heart disease, but it can happen to others as well.

What Does It Feel Like?

If VF happens only for a short time, a person may feel symptoms like:

A fluttering or racing heartbeat
Chest pressure or discomfort
Feeling very tired
Trouble breathing
Feeling dizzy or lightheaded

If VF lasts longer, it can cause fainting, collapse, and cardiac arrest.

How is Sudden Cardiac Arrest Treated?

Emergency CPR and AED
- CPR helps keep blood flowing to the brain and body when the heart is not pumping.
- An AED (automated external defibrillator) can give an electric shock to stop VF and help the heart return to a normal rhythm.
- Quick CPR and AED use can save lives while waiting for emergency medical services (EMS).
Implantable Cardioverter-Defibrillator
- People who survive sudden cardiac arrest often receive an ICD, a small device placed under the skin of the chest.
- The ICD watches the heart rhythm all the time.
- If a dangerous rhythm is detected, it gives a shock to restore a normal heartbeat.
- This helps prevent fainting, cardiac arrest, and heart damage.
Medications
- Some medicines can help lower the risk of dangerous heart rhythms:
  - Beta blockers (such as metoprolol or carvedilol):
    - Often the first medicine used
    - Help slow the heart and reduce stress on it
    - Possible side effects: tiredness, dizziness, low blood pressure
  - Antiarrhythmic medicines (such as sotalol or amiodarone):
    - Help control abnormal heart rhythms
    - Can sometimes slow the heart too much, so close monitoring is needed
    - Amiodarone is very effective but requires regular blood tests and checkups (lungs, eyes, thyroid) due to possible side effects