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Cardioversion - Illustrated Article

by Monica Zangwill, MD, MPH

Anatomy and Physiology

The heart normally beats in a regular rhythm at 60-100 beats per minute. This steady and coordinated rhythm allows the heart to effectively pump blood.

The heart rhythm is controlled by electrical signals that travel through the heart. These electrical signals start in a cluster of cells called the sinoatrial node, or the pacemaker. This cell cluster is located in the right upper chamber of the heart, called the right atrium. When the electrical signals reach the heart muscle, they cause it to contract and pump blood.

Reasons for Procedure

An abnormal heart rhythm is called an arrhythmia. Arrhythmias can start in the upper chambers of the heart, the atria, or the lower chambers, the ventricles.

An arrhythmia may cause a fast and/or irregular heart beat. Arrhythmias can weaken the heart's ability to pump blood to the rest of the body. Certain arrhythmias may also promote the formation of clots in the heart.

People who have arrhythmias that start in the atria may feel chest pain or palpitations like a fluttering in the chest. They may be lightheaded, have trouble breathing, or have no symptoms at all. Common types of these arrhythmias are called atrial fibrillation and atrial flutter.

Arrhythmias that start in the ventricles may be life-threatening. People with these arrhythmias may become unconscious and need immediate attention.


If your heart rhythm is fast or irregular, your doctor may recommend slowing it down or converting it back to a normal rhythm. This can be done by using medicines or through a procedure called electrical cardioversion. Your doctor will suggest a treatment for you based on your symptoms, medical history, and your type of arrhythmia.

If you have an atrial arrhythmia, your doctor may schedule you to have an elective cardioversion in the hospital. If you have a ventricular arrhythmia, emergency personnel may give you immediate cardioversion in the emergency department or wherever you may be.

Electrical cardioversion, also called direct current or DC cardioversion, works by delivering a high power electrical shock to your body. This resets the electrical signal of the heart and allows the sinoatrial node to restore a normal rhythm.


In the days and weeks leading up to your elective cardioversion: You may be given blood-thinning medications to take for several weeks prior to the cardioversion to reduce the chance of a clot forming in your heart. You will have an electrocardiogram, or EKG, to record your heart's electrical activity. You may have a transesophageal echocardiogram, which is a test that takes an ultrasound picture of your heart to check for the presence of blood clots.

Also prior to your cardioversion: Arrange for a ride to and from the hospital and for help at home as you recover. The night before, eat a light meal and do not eat or drink anything after midnight. If you regularly take medications, herbs, or dietary supplements, your doctor may recommend temporarily discontinuing them. Do not start taking any new medications, herbs, or dietary supplements before consulting your doctor.

An elective cardioversion is done with sedation. Before the procedure, you will be connected to an intravenous line. You will sleep through the procedure and will not remember it. EKG electrodes will be placed on your chest to monitor your heart's electrical activity.

Once you are sedated, special cardioversion pads or paddles are placed on your chest or your chest and back. These pads or paddles deliver the electrical shock to the chest where it travels to the heart. The shock may be repeated several times until the heart restores its normal rhythm.

Risks and Benefits

Possible complications of cardioversion include: inability to convert the arrhythmia to a normal rhythm, return of the arrhythmia after the procedure, development of another type of arrhythmia or no rhythm at all, damage to the heart muscle, introduction of blood clots from your heart into your circulation, which may lead to a stroke or other serious problems, burning or irritation to the skin of the chest or back where the pads or paddles are applied.

Benefits of cardioversion include: return of normal heart rhythm; improvement in the heart's ability to effectively pump blood, decrease in palpitations, chest pain, lightheadedness, difficulty breathing, or other symptoms of the arrhythmia, and/or decreased risk of clot formation in the heart.

In cardioversion, or any procedure, you and your doctor must carefully weigh the risks and benefits to determine whether it's the most appropriate treatment choice for you.

After the Procedure

After your electrical cardioversion, you will be monitored closely in a recovery room or in the coronary care unit of the hospital. Once the sedation wears off and you are in stable condition you will be sent home. Your doctor may continue your blood-thinning medications.

Once at home, be sure to contact your doctor if you experience: blisters, redness, or open sores on your chest or back where the pads or paddles were placed, lightheadedness, dizziness, or confusion, palpitations or the sensation of your heart fluttering or skipping heartbeats, an irregular pulse, chest pain.

Also contact your doctor if you experience: shortness of breath; severe nausea or vomiting, blood in your urine, changes in your vision or speech, difficulty walking or using your limbs, drooping facial muscles.


* Cardioversion. Cardiology Patient Page. American Heart Association. Available at: Accessed June 30, 2004.
* Facts about arrhythmias/rhythm disorders. National Heart, Lung and Blood Institute website.Available at: July 1, 2004.
* Heart, How It Works. American Heart Association Available at: Accessed June 30, 2004.

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