Cardioversion: How It Works

Medically Reviewed By Dr. Payal Kohli, M.D., FACC

Cardioversion is a procedure used to treat arrhythmias, or irregular heartbeats. Electrical cardioversion involves sending low energy shocks to the heart, while chemical cardioversion involves taking medications to restore regular heart rhythms. Cardioversion can be a scheduled procedure. It may also be necessary in an emergency to treat cardiac arrest, in which case it is called defibrillation.

Read on to learn more about how doctors perform cardioversion, how to prepare for it, and what recovery looks like.

Why do people need cardioversion?

An older adult checks their pulse
Jovana Milanko/Stocksy United

Your doctor may recommend cardioversion to treat cardiac arrhythmias when the rhythms cause serious symptoms. These symptoms can include shortness of breath, dizziness, fainting, low blood pressure, and chest pain or pressure.

Cardioversion may also be necessary in an emergency to treat sudden, life threatening arrhythmias.

Your heart’s energy comes from a built-in electrical conduction system that sends electrical signals through the heart’s four chambers. Certain malfunctions in these signals will cause an arrhythmia that may require cardioversion.

According to the American Heart Association (AHA) Trusted Source American Heart Association Highly respected national organization Go to source , cardioversion treats the following cardiac arrhythmias:

  • Atrial fibrillation: This occurs when electrical signals move too quickly and erratically through the heart’s upper chambers, or atria. The signals cause the atria to quiver instead of contracting effectively and can cause the bottom chambers, or ventricles, to race.
  • Atrial flutter: This occurs when electrical signals move too quickly through the atria.
  • Ventricular tachycardia: This occurs when the ventricles beat extremely quickly. The rapid contractions cannot pump enough blood to produce a pulse for very long. Without rapid cardioversion, it can lead to ventricular fibrillation, which is a life threatening cardiac arrhythmia that can lead to cardiac arrest and death.
  • Supraventricular tachycardia: This occurs when the atria beat rapidly.

What are the types of cardioversion?

There are two types of cardioversion: chemical (pharmacological) cardioversion and electrical cardioversion. The sections below cover these in more detail.

Chemical (pharmacological) cardioversion

Chemical cardioversion uses oral or IV medications to convert Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source your arrhythmia to a regular heartbeat. Your doctor will monitor your heartbeat and blood pressure closely after chemical cardioversion.

Electrical cardioversion

Doctors use electrical cardioversion to send synchronized shocks to your heart if your arrhythmia does not respond to medications. This method delivers an electrical shock at a specific time in the heart rhythm, causing all the heart cells to contract simultaneously and allowing the heart to “reset” its typical electrical activity.

For people with a high risk of arrhythmias that can become life threatening, doctors may recommend an implantable cardioverter-defibrillator (ICD) or a wearable cardioverter-defibrillator (WCD).

An ICD is implanted in the chest or stomach and is attached to the heart by wires and electrodes. A WCD rests on your skin and monitors your heart rhythm through sensors. Both devices can send a shock to your heart if they detect an arrhythmia.

Electrical cardioversion may be necessary in an emergency, such as when a person experiences dizziness or near fainting. If the person is unresponsive, this type of treatment is known as defibrillation. In this situation, a doctor or paramedic sends electrical shocks to the heart at any point in its rhythm. In synchronized electrical cardioversion, doctors time the shocks to arrive Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source at a certain point in the rhythm.

How do I prepare for cardioversion?

Your doctor will ask you to fast for a certain period to prepare for scheduled cardioversion. They may also have you stop taking certain medications before the procedure.

If you are having Trusted Source American Heart Association Highly respected national organization Go to source electrical cardioversion, it is important not to apply any ointments, powders, or lotions to your chest or back before the procedure. Doctors will need to place electrodes on these areas, and those substances may prevent proper skin contact. They may also need to shave any chest hair to ensure good contact.

How do doctors perform cardioversion?

A cardiologist, or a doctor who specializes in diagnosing and treating heart diseases, will typically perform scheduled cardioversion. In an emergency, paramedics and emergency medicine doctors can also perform cardioversion or defibrillation.

Electrical cardioversion generally includes these steps:

  1. You will receive an anesthetic to make you fall asleep.
  2. Your doctor will apply two electrodes to the front and side of your chest, or one on your chest and one on your back. The electrodes are attached to a cardioversion machine, which will show your heart rhythm.
  3. Your doctor will send one shock to your heart.
  4. Your doctor will re-analyze the resulting heart rhythm and deliver more shocks — possibly at higher doses — as needed.

For chemical cardioversion, your doctor will give Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source you either oral or IV medication and monitor your heart rate and blood pressure for signs of any complications.

What are some potential complications of cardioversion?

Complications resulting from cardioversion are uncommon, but it is possible for them to develop during the procedure or your recovery.

Some risks and potential complications of cardioversion include: 

  • You may have an adverse reaction to the anesthetic.
  • Blood clots that have developed in the heart due to an arrhythmia can become dislodged. These blood clots can move through the bloodstream to the other areas of the body and cause a stroke or another issue.
  • The electrodes may cause your skin to become irritated or sore.
  • In some cases, cardioversion can worsen existing arrhythmias or cause new ones.
  • Cardioversion can cause atrial stunning, which occurs when the heart’s upper chambers experience temporary mechanical dysfunction after the procedure.

To reduce your risk of complications from clotting, your doctor may give you anticlotting medications before and after the procedure.

Your doctor may also Trusted Source American Heart Association Highly respected national organization Go to source be able to recommend a cream or medication to help soothe your skin.

What does recovery from cardioversion look like?

After cardioversion, many people feel immediate relief from their arrhythmia symptoms. You may need Trusted Source American Heart Association Highly respected national organization Go to source to receive further treatment or take medications to continue to treat arrhythmia. Talk with your doctor or care team if you have new symptoms or if your symptoms do not go away.

Cardioversion can convert an arrhythmia to a regular heart rhythm, but it will not cure heart disease or any other underlying causes of arrhythmias, and the arrhythmia may recur.

You may need to make adjustments in your diet and lifestyle as a part of your treatment plan after cardioversion. Adjustments will vary depending on the underlying cause, your health, your age, and other factors. Talk with your doctor about your diagnosis and treatment plan and how they will affect your everyday life.

FAQ

Here are a few commonly asked questions about cardioversion.

Are you awake during cardioversion?

You will not be awake during cardioversion. A doctor will administer an anesthetic through an IV line before the procedure to make you fall asleep.

How long does cardioversion last?

Cardioversion only lasts a few minutes, and you can likely go home the same day. However, you may need to stay at the hospital for a while after the procedure. During this time, doctors will monitor your blood pressure and heart rhythm for any signs of complications.

Summary

Cardioversion is a procedure used to treat arrhythmias. Chemical cardioversion involves taking medications to restore regular heart rhythms, while electrical cardioversion involves sending low energy shocks to the heart.

Symptoms of arrhythmias can include shortness of breath, dizziness, fainting, low blood pressure, and chest pain or pressure. After cardioversion, many people experience immediate relief from their symptoms.

Talk with your doctor if you are experiencing symptoms consistent with arrhythmia. They can help determine if cardioversion is right for you.

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Medical Reviewer: Dr. Payal Kohli, M.D., FACC
Last Review Date: 2022 May 19
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