Defibrillators: How They Restore Normal Heart Rhythm

What Is a Defibrillator?

A defibrillator is a medical device that delivers a controlled electric shock to the heart to terminate life-threatening arrhythmias (such as ventricular fibrillation or pulseless ventricular tachycardia) and restore a normal sinus rhythm.

Types of Defibrillators

• Automated External Defibrillators (AEDs): Portable, user-friendly devices designed for layperson use in public spaces. They analyze heart rhythm and advise shock delivery.
• Manual External Defibrillators: Used by trained healthcare professionals (paramedics, nurses, physicians) who interpret rhythms and manually select energy levels.
• Implantable Cardioverter Defibrillators (ICDs): Surgically implanted devices that continuously monitor heart rhythm and automatically deliver shocks when needed.
• Wearable Cardioverter Defibrillators (WCDs): External vests with electrodes for temporary protection in high-risk patients.

When Are They Used?

Defibrillators are deployed in emergencies when the heart stops beating effectively (cardiac arrest) or beats in a chaotic, non-perfusing rhythm. Early defibrillation (within 3–5 minutes) dramatically improves survival rates.

Key Points

• Defibrillation does not "restart" a stopped heart (asystole); it resets a fibrillating heart.
• CPR should be performed until a defibrillator is available.
• Public access to AEDs and widespread CPR training save lives.