Cardioversion is the delivery of an electric shock to the chest via electrodes or paddles in order to correct a dangerous heart dysrhythmia. A dysrhythmia is an abnormality of the heartbeat which may be either a faster or slower than normal rate.

Cardioversion can be done as an elective (scheduled) procedure, or may be done urgently if a dysrhythmia is immediately life threatening.

External Cardioversion

Nucleus factsheet image

© 2008 Nucleus Medical Art, Inc.

Parts of the Body Involved

Chest wall and heart

Reasons for Procedure

Certain heart dysrhythmias may prevent the normal circulation of blood through the body and may deprive various organs, including the brain and heart, of oxygen.

Nonemergency cardioversion may be used to treat the following conditions:

  • Atrial fibrillation—very rapid, irregular twitching in the atrium, when the ventricular heart rate is not too fast
  • Atrial flutter—rapid but regular contractions in the atrium, when the ventricular heart rate is not too fast

Emergency cardioversion may be used to treat the following types of dysrhythmias, which can lead to death if they are not immediately converted to a more normal rhythm:

  • Atrial tachycardia—rapid beating of the heart, originating in the atrium with rapid ventricular heart rate
  • Ventricular tachycardia—rapid beating of the heart, originating in the ventricle
  • Ventricular fibrillation—rapid movement of the ventricular muscle without effective beats

Risk Factors for Complications During the Procedure

  • Blood clots in the heart chambers that may be dislodged into the circulation during cardioversion

What to Expect

Prior to Procedure

For elective cardioversion:

  • To diagnose the condition, you will have an electrocardiogram (ECG, EKG)—a test that records the heart's activity by measuring electrical currents through the heart muscle.
  • You may be given blood thinners for several weeks prior to nonemergency cardioversion.
  • You may undergo transesophageal echocardiogram to evaluate the presence of blood clots in the heart.
  • Arrange for a ride to and from the procedure.
  • Arrange for help at home after the procedure.
  • The night before, eat a light meal and do not eat or drink anything after midnight.
  • Do not take digoxin, a heart medication, the morning of the procedure.

For urgent cardioversion, there is no time for to prepare for the procedure.

During the Procedure

  • You will have continuous cardiac monitoring.
  • An intravenous line will be placed to administer medications or fluids as needed.
  • Short-acting, deep sedation or anesthesia will be given.


Short-acting general or brief, deep sedation

Description of the Procedure

Electrodes or paddles are applied to the chest. An electric charge is delivered through these electrodes or paddles to the chest and into the heart. This momentarily stops the electrical activity of the heart and allows the heart to reset itself into a normal rhythm. This may need to be repeated several times, with a gradually increasing electric charge.

After Procedure

You'll be monitored closely in a recovery room or in the coronary care unit of the hospital. If you had nonemergency cardioversion, you'll be sent home after the sedation wears off and once you are in stable condition.

How Long Will It Take?

The procedure itself is usually less than 30 minutes. You will need to be monitored for at least several hours after the procedure.

Will It Hurt?

Anesthesia prevents pain during the procedure. If you have urgent cardioversion, you may still be unaware of the pain involved, or you may feel a jolt that some people liken to a kick in the chest.

Possible Complications

  • Inability to stop the abnormal rhythm
  • Resumption of the abnormal rhythm after a normal rhythm was established
  • Development of a more dangerous dysrhythmia
  • Damage to the heart muscle
  • Blood clots introduced into your circulation, leading to such complications as stroke or damage to your intestines, kidneys, or limbs
  • Burning or irritation to the skin of the chest where the paddles or electrodes are applied
  • Death

Average Hospital Stay

Elective procedures are usually performed in a monitored outpatient setting, and most people can go home later that day. People who need emergency cardioversion may be admitted to the hospital for further observation or because of the illness that caused the event.

Postoperative Care

You may be put on blood thinners for a few weeks after undergoing cardioversion. (In which case, blood levels of these medications will need to be monitored via blood tests, usually weekly). You may also be put on a medication called an anti-arrhythmic, which will help prevent the dysrhythmia from recurring.


Cardioversion usually results in a more normal heart rhythm

Call Your Doctor If Any of the Following Occurs

  • Blisters, redness, or open sores on your chest
  • Lightheadedness, dizziness
  • Confusion
  • Sensation of your heart fluttering (palpitations)
  • Sensation of a skipped or missed beat, or an irregular pulse
  • Cough, difficulty breathing, shortness of breath
  • Severe nausea or vomiting
  • Chest pain or pain in your left arm or jaw
  • Pain in your abdomen, back, arms, or legs
  • Blood in your urine
  • Changes in vision or speech
  • Difficulty walking or using your limbs
  • Drooping facial muscles


American Heart Association

National Heart, Lung, and Blood Institute


Health Canada

Heart and Stroke Foundation of Canada


Procedures for Primary Care Physicians . Mosby-Year Book, Inc; 1994.

Last reviewed November 2007 by J. Peter Oettgen, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

Your Health and Happiness