Cardioversion is the delivery of an electric shock to the chest through electrodes or paddles. The shock is given to correct a dangerous heart rhythm.

Cardioversion can be done as a planned procedure or may be done urgently if an abnormal heartbeat is immediately life-threatening.

External Cardioversion

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Reasons for Procedure

The heart should beat in a regular rhythm. Abnormal rhythms can make it hard for the heart to pump blood and oxygen to through the body. This can cause damage to organs, including the brain and heart.

Non-emergency cardioversion may be used to treat:

  • Atrial fibrillation—very rapid, irregular quivering in the upper chamber of the heart. Can cause problems with how lower chambers work.
  • Atrial flutter —fast but more regular movement in the upper chambers.

Other arrhythmias can lead to death if they are not immediately treated. Emergency cardioversion may be used to treat:

  • Atrial tachycardia —rapid beating of the entire heart that starts in upper chambers.
  • Ventricular tachycardia—rapid beating of the heart that starts in lower chamber.
  • Ventricular fibrillation—lower chambers moving fast but not able to push blood out of the heart. May be a fatal.

Possible Complications

Problems from the procedure are rare, but all procedures have some risk. Your doctor will review potential problems, like:

  • Inability to stop the abnormal rhythm
  • Abnormal rhythm is resumed after a normal rhythm was established
  • Development of a more dangerous arrhythmia
  • Damage to the heart muscle
  • Blood clots introduced into your circulation, leading to such complications as a stroke or organ damage
  • Burning or irritation to the skin of the chest where the paddles or electrodes are applied

What to Expect

Prior to Procedure

The doctor will review tests that were already done. For planned cardioversion:

  • Blood thinners may be given for several weeks before the procedure.
  • A transesophageal echocardiography may be done to look for 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. Do not eat or drink anything after midnight.
  • Some medication may need to be stopped before the procedure. Talk to the care team about any medicine you are taking.

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


A deep sedation medicine will be used. You will be unaware of the treatment.

Description of the Procedure

Electrodes or paddles will be applied to the chest. An electric charge will be delivered through these electrodes or paddles to the chest and heart. This can reset the electrical activity of the heart. The process may need to be repeated to reach the desired heart rhythm. The electric charge may be increased with each attempt.

Immediately After Procedure

You will be monitored closely in a recovery room until you are fully awake. You may be allowed to go home after the procedure. You may need to stay in the hospital if medicine will be needed to keep your heart in rhythm.

How Long Will It Take?

The procedure itself is usually less than 30 minutes.

How Much Will It Hurt?

Sedation prevents pain during the procedure. If you have an urgent cardioversion, you may be more aware during the procedure. You may feel a jolt that some people liken to a kick in the chest.

Average Hospital Stay

If you had nonemergency cardioversion, you may be sent home.

People who need emergency cardioversion may be admitted to the hospital.

Post-procedure Care

At Home

Blood thinners and medicine to keep a healthy rhythm may be needed.

Call Your Doctor

It is important to monitor your recovery. Alert your doctor to any problems. If any of the following occur, call your doctor:

  • Blisters, redness, or open sores on your chest
  • Confusion or lightheadedness
  • Sensation of your heart fluttering (palpitations)
  • Sensation of a skipped or missed heartbeat, 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

If you think you have an emergency, call for emergency medical services right away.


American Heart Association
Heart Rhythm Society


Canadian Heart Rhythm Society
Heart and Stroke Foundation of Canada


Cardioversion of atrial fibrillation. EBSCO DynaMed website. Available at:
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Accessed November 28, 2020.
Direct-current (DC) cardioversion-defibrillation. Merck Manual Professional Version website. Available at:
...(Click grey area to select URL)
Accessed November 28, 2020.
Overview of arrhythmias. Merck Manual Professional Version website. Available at:
...(Click grey area to select URL)
Accessed November 28, 2020.
Last reviewed November 2020 by EBSCO Medical Review Board Michael J. Fucci, DO, FACC
Last Updated: 12/20/2020

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