Synchronized Cardioversion for an Abnormal Heart Rhythm

This information was reviewed and approved by Madison Hucke, BSN, RN (6/23/2026).

What is synchronized cardioversion?

Your healthcare provider has suggested you have a procedure called synchronized cardioversion because of an abnormal heart rhythm. Synchronized cardioversion is a procedure where an electrical shock is used to reset the rhythm of your heart. The electrical shock is synchronized so it happens at the appropriate time during the heart beating cycle.

Sometimes a procedure called transesophageal echocardiogram (TEE) is done before synchronized cardioversion. Your doctor may recommend you have TEE before synchronized cardioversion as part of your evaluation at National Jewish Health. If this is done, you will receive the Test Facts on TEE also.

Preparing for your Synchronized Cardioversion

Stop eating all food for 8 hours before your procedure. You may still sip clear liquids only until 4 hours before your procedure. Clear liquids include: water, clear juices without pulp (such as apple juice), and clear sports drinks. Stop drinking fluids of any kind 4 hours before your procedure. If you do not follow these instructions, your procedure will be cancelled for your safety.
Avoid caffeine sources 24 hours prior to this test. This includes coffee, decaffeinated coffee, tea, decaffeinated tea, herbal tea, soda pop and chocolate.
You may be asked to hold certain medications. Notify your doctor if you take any diabetes or weight loss medications such as Ozempic, Mounjaro, Wegovy, or Trulicity, etc., as you may need to hold these medications up to a week before the procedure.

On Procedure Day

Please arrive 60 minutes before your test is scheduled.
Check in at the Front Desk, and they will direct you to the Minimally Invasive Diagnostic Center (MIDC) waiting area. If you have questions, or if you would like to cancel or reschedule your appointment, please call 303-398-1355, option #4.
Do not take the medicines your healthcare provider has asked you to hold.
Heart, blood pressure, or seizure medication may be taken as prescribed with a small sip of water at least 2 hours before your procedure.
Do not wear jewelry.
A responsible adult must wait for you at National Jewish Health during your procedure and take you back to your residence after you are discharged. They must be readily available for the recovery period to review discharge instructions. You will not be able to drive yourself or take a taxi/public transportation. If you do not have someone with you to drive you home, your procedure will be cancelled.
You should not work, drive, or make any important decisions for the rest of the day.

What is done during the procedure?

When you arrive in the procedural area, the healthcare team will explain what will be done before, during, and after the synchronized cardioversion. If you have any questions, please ask. A nurse will start an IV and review your medical history with you. Your vital signs will be monitored throughout your stay in the procedural area. Additionally, a technician will obtain a 12-lead electrocardiogram (ECG) prior to your procedure. Small, sticky patches will be placed on your chest and are attached to an electrocardiograph monitor (ECG) that charts your heart’s electrical activity. Hair on your chest may be shaved before the electrodes are applied to improve the contact between the skin and electrode.

You will meet with the provider performing your procedure as well as the anesthesia provider prior to being transported to the procedure room. The anesthesia provider will give you medication through your IV to keep you comfortable and asleep.

During the procedure, the provider or nurse will apply large pads to your chest. An electrical shock will be delivered to reset the rhythm of your heart. The electrical shock is synchronized so that it happens at the appropriate time during the heart beating cycle. It may take more than one shock to reset the rhythm of your heart. You will be always monitored by trained medical staff before, during and after the procedure.

Once the procedure is complete, you will go to a recovery room and be monitored by a nurse until you are awake, and your provider determines when you are able to go home. Another 12 lead ECG will be obtained after the procedure to confirm your heart rhythm and the success of your procedure. Your nurse will review your procedure report and discharge instructions with you and send you home with a copy of each.

How long will the test take?

The average time at the facility from check-in to discharge is typically 2 to 3 hours. This timeframe includes pre-procedure preparation, procedure, and post-procedure recovery. The synchronized cardioversion is a very rapid procedure and is often completed within 15 to 45 minutes. Your visit may take longer depending on the complexity of your medical needs and the overall patient volume at the time. We appreciate your patience and understanding as we work to provide the highest quality care to every patient.