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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 an elective (scheduled) procedure or may be done urgently if an abnormal heartbeat is immediately life-threatening.
External Cardioversion
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Reasons for Procedure

If the heart is not beating regularly, it may prevent the normal circulation of blood through the body. This may deprive various organs, including the brain and heart, of oxygen. Without oxygen, the organs cannot properly function and will eventually die.
In atrial fibrillation, the electrical signals from the atria are fast and irregular. The atria quiver, rather than contract. Some signals do not reach the ventricles and the ventricles continue pumping, usually irregularly and sometimes rapidly
Non-emergency cardioversion may be used to treat the following conditions:
  • Atrial fibrillation —very rapid, irregular quivering in the atrium, the ventricles pump irregularly
  • 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 irregular heartbeats, 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 pumping (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 dysrhythmia
  • 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

For elective cardioversion:
  • To diagnose the condition, you will have an ECG . An ECG can record the heart's electrical activity.
  • You may be given blood thinners for several weeks before the procedure.
  • You may undergo a transesophageal echocardiography . This is an ultrasound test 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.
  • Check with your doctor to see if you should take your medications normally on the morning of the procedure.
For urgent cardioversion, there is no time for to prepare for the procedure.


You will have a short-acting deep sedation, so you will be unaware of the procedure happening.

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 into the heart. This resynchronizes the electrical activity of the heart. It allows the heart’s normal pacemaker to resume normal function. The process may need to be repeated. 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. If medication needs to be started to keep your heart in rhythm, you may need to stay in the hospital.

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 partially 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 once you are in stable condition.
People who need emergency cardioversion may be admitted to the hospital. This may be done for further observation or because of the underlying illness that caused the event.

Post-procedure Care

At Home
You may be put on blood thinners for a few weeks after the procedure. In this case, blood levels of these medications will need to be monitored via blood tests, usually weekly. Your doctor may also advise an anti-arrhythmic. This type of drug will help prevent the abnormal heartbeat from happening again.

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 Plus website. Available at: . Updated February 22, 2017. Accessed November 28, 2017.
Direct-current (DC) cardioversion-defibrillation. Merck Manual Professional Version website. Available at: Updated September 2017. Accessed November 28, 2017.
Overview of arrhythmias. Merck Manual Professional Version website. Available at: Updated September 2017. Accessed November 28, 2017.

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