Cardioversion is a medical procedure to correct a heartbeat that is irregular or too fast. It can involve risks and side effects but is generally safe and effective.

Doctors primarily use cardioversion to treat people with atrial fibrillation, also known as A-fib, or other forms of arrhythmia. It involves using medication or electrical signals to help the heart return to its regular rhythm.

This article describes cardioversion in more detail, including the associated risks, what to expect during the procedure, and more.

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Cardioversion is a medical procedure that helps correct a fast or irregular heartbeat.

There are two forms of the procedure:

  • Pharmacological, or chemical, cardioversion: Pharmacological cardioversion uses oral or IV medications to restore the rhythm of the heart. Doctors may use this form of treatment for people in a stable condition.
  • Electrical cardioversion: Electrical cardioversion uses electrical pulses to return the heart to a regular rhythm. This type will be necessary in an emergency.

A doctor most commonly uses cardioversion to correct A-fib, which is a fast, irregular heartbeat. However, they may also use it to treat other types of arrhythmias, such as:

A doctor may choose to use pharmacological cardioversion in people who are generally in good health and stable.

In an emergency, they will need to perform an electrical cardioversion to help address potentially life threatening arrhythmias.

Both cardioversion and defibrillation can use a manual device to administer electrical impulses to the heart.

According to a 2021 article, the main difference between them is the timing and method of administering the electrical shocks.

Cardioversion uses electrical shocks that are synchronized with the heart’s rhythm. The shocks help stabilize a person’s heartbeat, which is still present.

Conversely, defibrillation administers asynchronous electrical shocks to the person. When a healthcare professional performs defibrillation, a person is often in cardiac arrest, meaning that their heart has stopped beating.

Another difference is that cardioversion uses less energy than defibrillation.

Cardioversion has minimal associated risks, but it is not risk-free.

There is a slight possibility of chemical cardioversion causing embolic events, which can result in stroke. A 2021 article states that this risk is small for those with arrhythmias that have lasted less than 48 hours.

The risk is higher for those with chronic arrhythmias. A healthcare professional will prescribe anticoagulant medication, or blood thinners, for at least 3 weeks before a person undergoes chemical cardioversion. People may need to continue taking this medication for 4 weeks afterward.

The American Heart Association (AHA) notes that electrical cardioversion can also increase a person’s risk of stroke. A doctor can reduce this risk by providing the person with blood thinners, such as warfarin, before the procedure.

A person also has a small chance of irritation or burns at the sites where the pads are in contact with the body.

It is important to note that there is a chance that the procedure will not be successful in returning the heart’s rhythm to normal. In such cases, the person may need additional therapies to correct the arrhythmia.

In cases of emergency cardioversion, a person will not need, or have time, to prepare.

Otherwise, the AHA notes that a doctor will likely recommend taking a blood thinner for the 2–3 weeks leading up to the procedure.

They may also advise a person to prepare by:

  • avoiding putting creams and lotions on their skin for 24 hours
  • refraining from eating or drinking for 8 hours
  • arranging for someone to drive them to and from the appointment
  • organizing their schedule so that they will not need to operate machinery or make important decisions in the hours following the procedure

A person can often continue taking their regular medication according to the prescription unless the doctor instructs otherwise.

The following outlines what to expect during each type of cardioversion.

Electrical cardioversion

A healthcare professional will perform electrical cardioversion in a hospital setting, using the following steps:

  1. A doctor or nurse will insert an IV line into the person’s arm or hand and administer a sedative. This will stop the person from feeling pain during the procedure.
  2. The doctor will use two paddles to deliver the electrical shocks. They will place one paddle on the chest and one on the back. Alternatively, they will place both paddles on the chest.
  3. They will administer the electrical shock, which will last for less than 1 second. This shock will briefly stop the heart and reset its rhythm. Some people may require only a single shock, while others may require additional shocks.

The entire process typically lasts for 30 minutes.

After the procedure, a healthcare professional will monitor the person for an hour or two. It is common to feel drowsy for a few hours, but people are usually able to go home the same day.

Chemical cardioversion

A person can undergo chemical cardioversion in various settings, including a healthcare professional’s office, a hospital, and at home.

The doctor will deliver the medication orally or through an IV. For people with A-fib, they may use one of the following medications:

  • dofetilide
  • propafenone
  • flecainide
  • ibutilide
  • amiodarone

For individuals with SVT, they may provide adenosine or verapamil.

In some cases, the medication can work quickly, but in others, it may take hours or days to work. If chemical cardioversion does not work, the doctor may recommend electrical cardioversion.

The doctor will make the person aware of the side effects that may occur. If any of the side effects are severe, the person should let the doctor know.

Research suggests that the procedure is generally safe and effective.

In a 2019 study investigating the use of electrical cardioversion in acute cases of acute-onset atrial fibrillation, the procedure was 96.2% effective in restoring the normal rhythm of the heart. However, the authors note that while it was 100% effective in people aged 18–39 years, it was 68.8% effective in people older than 80 years.

Some studies indicate that long-term success rates are not as high. In fact, people may return to having irregular heartbeats within 6 months.

Experts indicate that cardioversion is generally effective and safe for adults younger than 80 years. Following most procedures, the heart rate returns to normal.

However, some studies indicate that long-term success rates are lower. In a 2019 study, researchers found that within 6 months, most people returned to an abnormal heart rate. However, the success rates for people who were living with A-fib for less than 1 year before the procedure were higher.

If the heart rate does not improve, a doctor may recommend additional therapies or procedures to help correct it.

Cardioversion is a procedure to correct irregular heartbeats. Doctors can use it in acute situations or as a treatment for people who have lived with A-fib or other arrhythmias.

There are two versions: chemical and electrical. The chemical procedure can help when a person is otherwise in good health, whereas the electrical one may correct both acute and long-term arrhythmias.

The initial success rate of electrical cardioversion is generally high, but after several months, the heart rate may become irregular again.