Cardioversion: Background, preparation & procedure

Cardioversion (delivery of a synchronized shock) is a medical procedure that helps to restore a normal heart rhythm in people with various types of arrhythmias (i.e., abnormal heartbeats). In cardioversion, electrodes are placed on the patient’s chest which sends electric shocks to the heart. Cardioversion can also be performed with certain medications. Usually, cardioversion is a scheduled procedure that is performed in a hospital. After the procedure is performed the patient can return home on the same day. For many patients, cardioversion restores a normal heart rhythm promptly.

Cardioversion is usually used to treat atrial fibrillation patients or patients with a flutter in atria. These conditions occur when the electric signals do not travel properly through the upper chamber of the heart to make a normal heartbeat at a regular rate. Cardioversion helps medical professionals to promptly see if cardioversion has restored normal heartbeat successfully. Electric cardioversion takes less time than cardioversion that is performed solely with medications. It depends on the prescription of medical professionals whether the patient will receive cardioversion with medications or electric cardioversion1.

Cardioversion is referred to as defibrillation when it is performed in an emergency condition to prevent death due to cardiac arrest caused by potentially fatal ventricular arrhythmias. If atrial fibrillation remains untreated it can increase the risk of heart failure and stroke2.


Heart muscle contract due to electrical impulses. Normally each impulse travels in an ordered and standardized manner over nerves from atria to ventricles, each resulting in a heartbeat. Any change in the pattern of these nerve impulses causes abnormal heartbeat.

Preparing for cardioversion:

Normally doctors advise the patients not to eat or drink 8 hours before the procedure. If the patient takes medicine before the procedure usually then he/she should sip enough water only to swallow the pill. If the patient does not take any medicine, the doctor will tell if he/she needs any medication before the procedure.

Sometimes, before cardioversion, a procedure called a transesophageal echocardiogram (it checks if there are any blood clots in the heart) is performed on the patient. As blood clots can break away and can cause life-threatening complications. This again will be decided by the medical professional whether the patient needs a transesophageal echocardiogram procedure to be performed or not.

If after a transesophageal echo (TEE) test blood clots appear in the heart, then the cardioversion procedure will be delayed for three or four weeks. In that time the patient will take blood-thinning medications to reduce the risk of any mishap1.

During cardioversion:

  • The patients are given medications through IV to make them sleep during the procedure, and don’t feel any pain because of the shocks. Other medications may also be given intravenously to help restore the normal heart rhythm of the patient.
  • Several large patches called electrodes are placed on the patient’s chest. The electrodes are attached to the defibrillator (cardioversion machine) with the help of wires. The machine detects your heart rhythm and delivers a shock to bring your heart rhythm back to normal. This machine also corrects the heart rhythm if it beats too slowly even after cardioversion. Once the patient is sedated, electric cardioversion takes only a few minutes to complete.

After cardioversion:

Cardioversion is done on an outpatient basis, this means that the patient can return home on the same day when the procedure is done. The patient spends an hour or so in the recovery room where he/she is kept under examination for any complications.

The patient needs someone to drive him/her home, as the decision-making power is affected for a few hours after the procedure.

Even if no clots are found in the patient’s heart, blood-thinning medications are given to the patient for at least some weeks after cardioversion is performed to avoid the formation of new clots.

Risks of cardioversion:

Risks associated with cardioversion are:

  • If the patient has atrial fibrillation, then there are chances of blood clots forming in the heart. Cardioversion can set the clot free and if the clot (embolus) travels to the brain it can cause a stroke.
  • If electrical cardioversion is performed on the patient, the skin where the electrodes were applied (i.e., chest or back) may become irritated. The doctor will prescribe any cream to make the skin of the patient feel better.
  • Cardioversion does not always bring normal heart rhythms back. In such a case the patient is given medications, an implantable cardioverter-defibrillator (ICD), or a pacemaker2


Cardioversion is the delivery of a synchronized shock (i.e., synchronized cardioversion) to restore a normal heartbeat. The procedure takes a few minutes after the patient is sedated. Medications are provided to restore a normal heart rhythm however in electrical cardioversion electric shocks are delivered to the heart by the help of electrodes. In either of the cases, the patient is allowed to return home the same day. Cardioversion can sometimes worsen arrhythmias and can cause life-threatening complications.


This page was last reviewed and updated by on Sep 15, 2020.