What is defibrillation?

Defibrillation is an emergency treatment for ventricular fibrillation and other life-threatening arrhythmias (abnormal heartbeats). A heart in ventricular fibrillation stops pumping blood to the brain and body. It will cause cardiac arrest and death within a few minutes if not treated immediately. Defibrillation restores a normal heartbeat by shocking the heart with electricity.

Rapid defibrillation saves lies, especially when combined with CPR and intensive medical care. Defibrillation does not reverse the underlying cause of the arrhythmia. It is not successful in all cases, especially with serious, untreated heart disease or certain end-stage diseases.

Types of defibrillators

The types of defibrillators include:

  • Advanced life support (ALS) unit is a device used by healthcare providers in hospitals and ambulances. ALS units also provide vital information to help healthcare providers make decisions and deliver treatments.
  • Automatic external defibrillator (AED) is a user-friendly device that laypersons and emergency medical technicians (EMTs), can operate. AEDs are available in public places, such as schools, shopping malls, and airports. An AED guides users to apply electrodes. It then automatically analyzes the patient’s heart rhythm. AEDs tell users to deliver a shock, if needed, or will deliver the shock automatically.
  • Implantable cardioverter defibrillator (ICD) is implanted in the chest or belly. It is attached to the heart by wires and electrodes and will automatically deliver a shock when needed. Your doctor may recommend an ICD if you are at risk for a life-threatening ventricular arrhythmia.
  • Wearable defibrillator is worn outside the body. Your doctor may recommend this device if you have a short-term risk of a life-threatening arrhythmia, or if you are not a candidate for an implantable device.

Other procedures that may be performed

Defibrillation must be combined with intensive medical care, called advanced cardiac life support (ACLS). ACLS treats the underlying cause of life-threatening ventricular arrhythmias and prevents them from occurring again. ACLS includes:

  • CPR (cardiopulmonary resuscitation) and repeat defibrillation as needed
  • Continuous monitoring of vital signs, heart rhythm, and other functions
  • IV medications to suppress more arrhythmias, reduce the heart’s workload, and improve blood pressure, vital signs, and other functions 
  • Oxygen therapy, which is often combined with intubation (placing a breathing tube in the windpipe). The breathing tube is connected to a ventilator to assist or perform breathing for the patient. 
  • Pacing using a temporary pacemaker to correct arrhythmias

Other procedures vary depending on the underlying cause of the life-threatening ventricular arrhythmia. Common procedures include:

  • Coronary angioplasty to widen or open a blocked or narrowed coronary (heart) artery. Blocked or narrowed coronary arteries are a risk for a heart attack.
  • Permanent pacemaker implant to provide continuous or as-needed automatic pacing of the heart rhythm 

Why is defibrillation performed? 

Your heart is a muscle that works like a pump. It has four chambers, two upper chambers (atria) and two lower chambers (ventricles). Like all pumps, your heart requires an energy source to function. Your heart's energy comes from a built-in electrical conduction system that sends electrical signals through the four chambers. 

Electrical signals coordinate the chambers to produce a normal heartbeat. Certain malfunctions in these signals will cause a disorganized, ineffective, quivering rhythm.

Defibrillation delivers an electrical shock that causes all the heart cells to contract at the same time. This stops the abnormal rhythm and allows the heart to restart normal electrical activity. Defibrillation must be done within several minutes of the start of a life-threatening ventricular arrhythmia to be effective.

Defibrillation treats immediately life-threatening ventricular arrhythmias including:

  • Ventricular fibrillation, which occurs when the lower chambers of your heart, or ventricles, beat so fast and unevenly that they just quiver, or shake. As a result, your heart pumps very little or no blood to your brain and body. Death occurs within five to 10 minutes without defibrillation.
  • Ventricular tachycardia without a pulse, which occurs when the ventricles beat extremely fast. This decreases efficiency of the heart. It reduces the amount of blood that your heart can pump out to your brain and body. If the amount of blood is not enough to produce a pulse or causes you to pass out, it requires treatment with defibrillation. Ventricular tachycardia without a pulse can also rapidly lead to ventricular fibrillation.