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What is cardioversion?

Cardioversion is a treatment for cardiac arrhythmias (abnormal heartbeats), including atrial fibrillation. Arrhythmias happen when the heart’s electrical signal causes it to pump too fast or irregularly. Arrhythmias can prevent the heart from pumping enough blood to your brain and body and cause other problems, such as blood clots. Cardioversion uses medications or low-energy electrical shocks to restore a normal heartbeat.

Cardioversion is usually a scheduled procedure. It is an emergency procedure done right away when symptoms are severe. Severe symptoms include dizziness, passing out, chest pain, shortness of breath, and low blood pressure.  

Cardioversion is only one method of treating cardiac arrhythmias. Discuss all of your treatment options with your doctor to understand which choices are right for you. 

Types of cardioversion

There are two basic methods of performing cardioversion. Your doctor will chose the best method for you based on the type of rhythm, your medical history, and your particular situation. Types of cardioversion include:

  • Chemical or pharmacological cardioversion uses oral or IV medications to convert your arrhythmia to a normal heartbeat. You may take medications at home or stay in the hospital during chemical cardioversion. Your doctor will monitor you closely in either case.

  • Electrical cardioversion uses low-energy shocks to convert your arrhythmia to a normal heartbeat. Electric cardioversion delivers an electrical shock at a specific time in the heart rhythm. Electric cardioversion 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.

Patients with a high risk of arrhythmias that can become rapidly life threatening may have an implantable cardioverter defibrillator (ICD). An ICD is implanted in the chest or belly. It is attached to the heart by wires and electrodes. 
An ICD delivers low-energy cardioversion shocks automatically when needed. If cardioversion shocks don’t convert the arrhythmia, the ICD will deliver a higher-energy defibrillation shock to convert the arrhythmia.

Other procedures that may be performed 

Your doctor may perform other procedures to diagnose and treat your cardiac arrhythmia or the underlying cause. Other procedures include: 

  • Advanced cardiac life support (ACLS) to stabilize your condition as needed. This can include defibrillation, cardiopulmonary resuscitation (CPR), and continuous monitoring of your vital signs and heart rhythm. ACLS may also include IV medications, oxygen therapy, and placing a breathing tube in your windpipe (intubation) and attaching it to a ventilator.

  • Transesophageal echocardiography (TEE) to rule out blood clots in the heart before your scheduled cardioversion. The arrhythmia, atrial fibrillation, can cause blood clots to develop in the heart. If you have blood clots, you may need to take blood-thinning medicines before a scheduled cardioversion.

Why is cardioversion performed? 

Your doctor may recommend cardioversion to treat cardiac arrhythmias when medications are not successful or when the rhythm causes serious symptoms. Serious symptoms include shortness of breath, dizziness, passing out, low blood pressure, and chest pain or pressure. 

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. These electrical signals coordinate the chambers to produce a normal heartbeat. Certain malfunctions in these signals will cause an arrhythmia that may require cardioversion.

Cardioversion treats the following cardiac arrhythmias:

  • Atrial fibrillation, which occurs when electrical signals move too fast and erratically through the heart’s upper chambers (atria). This causes the atria to quiver instead of contracting effectively.

  • Atrial flutter, which occurs when electrical signals move regularly, but too fast, through the atria.

  • Ventricular tachycardia with a pulse, which occurs when the ventricles beat extremely fast. The rapid contractions cannot pump enough blood to produce a pulse for very long. Without rapid cardioversion, it can quickly lead to ventricular fibrillation. This is a life threatening cardiac arrhythmia that can lead to cardiac arrest and death.

Who performs cardioversion?

Cardiologists perform scheduled cardioversions. A cardiologist is a doctor who specializes in diagnosing and treating diseases of the heart.

The following healthcare providers perform emergency cardioversion:

  • Cardiac surgeons specialize in the surgical treatment of conditions of the heart and its blood vessels. Cardiac surgeons may also be known as cardiothoracic surgeons.

  • Clinical cardiac electrophysiologists are cardiologists with specialty training in treating heart rhythm disturbances (arrhythmias).

  • Critical care medicine doctors specialize in the diagnosis and management of life threatening conditions.

  • Emergency medicine doctors specialize in rapidly diagnosing and treating acute or sudden illnesses, injuries, and complications of chronic diseases.

  • Paramedics are healthcare professionals who are trained to provide emergency medical treatment or to assist doctors in providing medical care.

  • Thoracic surgeons specialize in the surgical treatment of diseases of the chest, including the blood vessels, heart, lungs and esophagus. Thoracic surgeons may also be known as cardiothoracic surgeons.

How is cardioversion performed?

Your scheduled cardioversion will be performed in the hospital. Emergency cardioversion may be performed in the hospital or pre-hospital setting by paramedics. Cardioversion generally includes these steps:

  1. You will receive an IV and sedation to make you sleepy and keep you comfortable.

  2. Your provider will apply two sticky electrodes or paddles lubricated with special jelly to your upper right chest and lower left ribcage area. An alternative is placing the devices to the upper right chest and the upper left back.

  3. The cardioversion machine will show your heart rhythm in a waveform on a screen.

  4. The provider will analyze your heart rhythm and deliver one low-energy shock to your heart.

  5. The provider will re-analyze the resulting heart rhythm and deliver more shocks as needed. Your care team will monitor your blood pressure and other vital signs during and after the procedure.

An implantable cardioverter defibrillator (ICD) will automatically perform cardioversion as needed. Your ICD will automatically perform a higher energy defibrillation shock if the lower energy cardioversion shocks do not convert the arrhythmia. 

A high-energy shock feels like being kicked in the chest. If you feel a high-energy shock, you or someone you are with should immediately call 911, even if you feel fine afterward. You will need medical evaluation, monitoring, and possibly more treatment.

Will I feel pain?

Your comfort and relaxation is important to you and your care team. You may or may not feel a cardioversion shock, but some people describe it as feeling a thump in the chest. You will receive sedatives and pain medications so that you stay comfortable. Tell a member of your healthcare team if you are uncomfortable.

What are the risks and potential complications of cardioversion?  

Risks and complications of cardioversion are uncommon but, but any medical procedure involves risk and potential complications. Complications may become serious in some cases. Complications can develop during the procedure or recovery. Risks and potential complications of cardioversion include: 

  • Allergic reaction to sedation medications

  • Displacement of blood clots that have developed in the heart due to an arrhythmia, usually atrial fibrillation. Displaced blood clots can move through the bloodstream to the brain and cause a stroke.

  • Skin redness or burns where the paddles or electrodes touched the skin

  • Worsening of arrhythmias

Reducing your risk of complications

You can reduce the risks of some complications by following your treatment plan and:

  • Following activity, dietary and lifestyle restrictions and recommendations

  • Taking medications exactly as directed. This may include blood thinner medications to prevent blood clots that can travel to the brain and cause a stroke.

  • Telling all members of your care team if you have any allergies  or if you are pregnant or nursing

You can reduce the risks of some complications of an implantable cardioverter defibrillator by:

  • Avoiding close or prolonged exposure to electrical devices or devices that have a strong magnetic field. Your doctor will give you specific instructions about these devices.

  • Taking your medications exactly as directed. Some medications reduce the risk of unnecessary shocks.

How do I prepare for my cardioversion?

You are an important member of your own healthcare team. The steps you take before cardioversion can improve your comfort and outcome. 

You can prepare for a cardioversion by:

  • Answering all questions about your medical history and medications. This includes prescriptions, over-the-counter drugs, herbal treatments, and vitamins. It is a good idea to carry a current list of your medical conditions, medications, and allergies at all times.

  • Taking or stopping medications exactly as directed. This may include taking blood thinner medications.

Questions to ask your doctor

It is common for patients to forget some of their questions during a doctor’s visit. You may also think of other questions after your appointment or after you leave the hospital. Contact your doctor with concerns and questions before cardioversion and between appointments. 

It is also a good idea to bring a list of questions to your appointments. Common questions include:

  • Why do I need cardioversion? What are the other options for treating my condition?

  • Will I need chemical cardioversion using medications or electrical cardioversion using an electrical shock?

  • Who will perform my scheduled electrical cardioversion? Is this person a board-certified cardiologist?

  • How should I take my medications before and after my cardioversion?

  • When should I follow up with you?

  • How should I contact you? Ask for numbers to call during and after regular hours.

What can I expect after my cardioversion?

Knowing what to expect can help make your road to recovery after cardioversion as smooth as possible. 

How long will it take to recover?

Your care team will evaluate and monitor you closely after a scheduled cardioversion. You will likely go home the same day if you have a scheduled cardioversion and are in stable condition. Your doctor will tell you when you can return to normal activities.

After emergency cardioversion, you may also need other treatments to stabilize your condition and treat the underlying cause of your arrhythmia. Recovery time after emergency cardioversion varies depending on the underlying cause, your general health, your age, and other factors. Talk to your doctor about all the factors that influence your recovery and when you can return to normal activities.

How will I feel after the cardioversion?

Many people feel immediate relief of symptoms, such as dizziness and palpitations, after cardioversion. Tell your doctor or care team if you have new symptoms or if your symptoms do not go away.

You may be drowsy after your cardioversion and for the rest of the day if you had sedative medications. You will need a ride home from the hospital. It is a good idea to have someone stay with you for the first 24 hours.  

When should I call my doctor?

It is important to keep your follow-up appointments after cardioversion. Contact your doctor for questions and concerns between appointments. Call your doctor right away or seek immediate medical care if you have:

  • Breathing problems, such as shortness of breath, difficulty breathing, labored breathing, or wheezing
  • Change in alertness, such as passing out, dizziness, unresponsiveness, or confusion
  • Chest pain, pressure or squeezing, or palpitations

How might cardioversion affect my everyday life?

Cardioversion can save your life by converting an arrhythmia to a normal heart rhythm. It will not cure heart disease or other underlying causes of arrhythmias. 

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 general health, your age, and other factors. Talk with your doctor about your diagnosis and treatment plan and how it will affect your everyday life.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 15
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  2. Arrhythmia: Cardioverter-Defibrillator: A Treatment for Arrhythmia. American Academy of Family Physicians.
  3. Arrhythmias. American college of Cardiology.
  4. Cardioversion. American Heart Association.
  5. Cardioversion. Heart Rhythm Society.
  6. Implantable Cardioverter Defibrillator (ICD). American College of Cardiology.
  7. What is Cardioversion? National Heart Lung and Blood Institute.
  8. What is an Implantable Cardioverter Defibrillator? National Heart Lung and Blood Institute.